The development of sustainable lignin isolation strategies has gained increasing interest as industries seek environmentally friendly methods for biomass valorization. While several techniques are often described as green, it is important to clarify that physical-assisted methods such as microwave-assisted extraction (MAE) and plasma-assisted treatment are not inherently green unless paired with appropriate chemical systems. These technologies serve primarily as process intensification tools that can improve extraction efficiency when used in conjunction with alkaline, acidic, or deep eutectic solvents. The actual environmental footprint of these methods depends heavily on the nature of solvents and reagents employed.

While much of the current research has focused on the functional performance of LNPs in biopolymer films, there is a notable lack of experimental data on how these materials behave during or after recycling processes. In particular, it is unclear how thermal, mechanical, or chemical recycling methods affect the structural integrity, antioxidant activity, or barrier properties of LNPs once incorporated into food packaging matrices. As LNPs are biodegradable and often sensitive to heat and oxidation, their performance may degrade with repeated processing. However, no comprehensive studies have quantified these changes under real-world recycling conditions. This represents a critical knowledge gap in validating the role of LNP-based packaging within circular economy frameworks. Future investigations should assess the retention of nanoparticle functionality after recycling, evaluate nanoparticle migration behavior in reprocessed films, and explore strategies to enhance LNPs recyclability in bio-based composites.

The extraction method applied to isolate lignin from biomass significantly influences the physicochemical characteristics of the resulting lignin, which in turn governs its behavior during nanoparticle formation and the properties of the produced LNPs. Variations in extraction severity, chemical environment, and process conditions lead to lignin fractions with different molecular weights, functional group profiles, condensation degrees, and residual carbohydrate contents. These compositional and structural differences have critical implications for nanoparticle morphology, stability, and potential end-use functionality (124). For example, lignins obtained through relatively harsh treatments such as kraft pulping tend to have higher molecular weights, a greater degree of condensation, and more aliphatic and phenolic hydroxyl groups exposed due to ether bond cleavage (125). Despite its structural heterogeneity and lower solubility, kraft lignin has demonstrated exceptional potential for producing small-sized, monodisperse LNPs with high colloidal stability (126). The presence of abundant carboxylic acid groups and possible co-extracted hydrophobic compounds, such as resinous by-products from pulping, appear to facilitate the formation of nanoparticles with low diameters and strong negative zeta potentials, without the need for added surfactants or stabilizing agents (127).

On the other hand, lignins extracted via milder organosolv or acid-catalyzed methods typically retain a larger proportion of native ether linkages, especially β-O-4 bonds, and show lower levels of structural degradation. These lignins usually possess a narrower molecular weight distribution and higher chemical purity, which make them well-suited for applications where biocompatibility and reactivity are prioritized (128, 129). However, the resulting nanoparticles from these lignins often exhibit slightly larger sizes (ranging from approximately 60 to 100 nm), broader size distributions, and somewhat reduced colloidal stability compared to those derived from kraft lignin (130–132). Adjusting the pH during nanoprecipitation has been shown to be a simple yet highly effective strategy for tuning LNPs characteristics. Increasing the pH of the lignin solution prior to solvent shifting leads to deprotonation of carboxylic and phenolic groups, enhancing electrostatic repulsion and promoting the formation of smaller and more stable nanoparticles (133). The use of neutral to slightly basic conditions during nanoparticle precipitation has consistently resulted in reduced particle size and improved dispersion stability across multiple lignin types (127, 132).

Overall, while all major classes of technical lignin can be converted into nanoscale dispersions using appropriate techniques, the properties of the resulting LNPs are intricately tied to the origin and extraction pathway of the precursor lignin. Lignins derived from kraft processes may be more suitable for applications that require small, thermally stable nanoparticles with narrow size distributions, whereas lignins isolated through organosolv or acidolysis routes may offer advantages in terms of functional group availability, purity, and biocompatibility. The interplay between extraction conditions, molecular structure, and nanoparticle formation underscores the importance of tailoring lignin selection and processing strategies to match the performance requirements of specific material applications.

Chitosan (CH), a naturally derived polysaccharide obtained from chitin deacetylation, is one of the most promising candidates for replacing petroleum-derived plastics in sustainable food packaging. Its film-forming ability, biodegradability, biocompatibility, and intrinsic antimicrobial activity make it highly attractive. Nonetheless, native chitosan films suffer from low mechanical strength, limited oxygen and UV barrier properties, and high water vapor permeability, which restrict broader industrial adoption.

To overcome these limitations, numerous studies have explored the incorporation of LNPs into chitosan matrices. LNPs offer multiple functionalities, including UV shielding, antioxidative activity, moisture resistance, and mechanical reinforcement. This combination creates synergistic nanocomposites with markedly enhanced packaging performance.

Zou et al. (157) developed CH films containing LNPs and acylated soy protein isolate nanogels (ASPNG), which significantly improved film tensile strength (from 37.29 to 54.29 MPa), reduced oxygen permeability, and imparted strong antibacterial properties (Figure 4). The co-incorporation strategy demonstrated a synergistic effect, with ASPNG providing controlled release and LNPs reinforcing the film structure while also improving UV protection (157). In a separate study, Zhang et al. (176) prepared chitosan nanoparticle-based films (NCH) reinforced with alkali LNPs. The resulting NCH–LNPs composites showed increased crystallinity and thermal stability, along with a 1.5–3.4-fold increase in antioxidant capacity relative to controls. Applied to grape and cheese preservation, these films reduced lipid peroxidation and extended shelf life, underscoring their translational utility (176).

A similar enhancement was observed by Winotapun et al. (177), who applied CH–LNPs coatings onto bagasse paper using fractionated kraft lignin. The coatings showed nearly complete bacterial inhibition (>2 log CFU/cm² reduction against S. aureus and E. coli), as well as enhanced hydrophobicity. These eco-friendly multilayered systems demonstrate how CH–LNPs nanocomposites can be scaled for biodegradable paper packaging, replacing synthetic wax or polyethylene layers. Zhang et al. (158) used a deep eutectic solvent (DES)-assisted antisolvent method to prepare LNPs for CH film matrices. Their composite films exhibited ~40% higher tensile strength, significantly better UV-blocking, and enhanced radical scavenging capacity. Importantly, real-food applications demonstrated 10-day extended shelf life of refrigerated grass fish, confirming functional applicability for cold-chain packaging (158).

Another compelling approach was introduced by Vijayakumar et al. (178), who employed acid precipitation to generate LNPs of ~55 nm and incorporated them into CH films. With 15% LNPs loading, tensile strength and modulus increased by 86 and 93%, respectively, while water vapor transmission dropped by 32%. The films also achieved significant UV shielding and antioxidant improvements, critical for perishables sensitive to light and oxidation (178). Recent work by Abbadessa et al. (179) further explored layer-by-layer (LbL) assembly of lignin-based polymers with chitosan onto polyethylene substrates. While not fully biobased, this method demonstrated stepwise deposition of CH/LNPs bilayers, improving oxygen and water vapor barrier properties. This highlights CH’s versatility as both a standalone film matrix and a barrier-enhancing coating layer in hybrid designs (179).

Together, these studies demonstrate a consistent structure–property relationship: LNPs contribute to tighter polymer networks via hydrogen bonding, π–π interactions, and electrostatic attraction. These interactions reduce free volume, resulting in decreased gas/moisture diffusion and improved film integrity. Furthermore, the nanoscale dispersion of LNPs enables effective light scattering, enhancing UV blocking while contributing to opacity, a desirable trait in light-sensitive packaging. Despite these advances, key challenges remain. Achieving homogeneous LNPs dispersion, avoiding aggregation, and controlling interfacial compatibility require further optimization. Moreover, while antioxidant and antimicrobial activities are promising, their long-term migration behavior and safety profiles need evaluation for regulatory compliance. Thus, chitosan–LNPs nanocomposites are among the most promising fully biobased packaging candidates. They offer multifunctional enhancements, process compatibility, and effective food preservation, making them suitable for fresh produce, seafood, dairy, and bakery applications. With ongoing innovation in LNPs synthesis and film engineering, CH-based materials are poised to play a central role in next-generation sustainable packaging.

Starch (ST), a low-cost, abundant, and renewable polysaccharide, has been widely studied as a sustainable alternative to petroleum-based films. Its natural biodegradability and film-forming ability make it attractive for food packaging. However, starch films inherently suffer from poor moisture resistance, low mechanical strength, and weak barrier properties, especially under humid conditions. To address these issues, incorporation of LNPs has been explored as a biocompatible, multifunctional strategy to reinforce starch matrices.

Firouzjaei et al. (180) developed starch-based nanocomposite films incorporating LNPs (1, 3, and 5% w/w) and cinnamaldehyde (CI), a natural antimicrobial agent. Their binary (ST–LNPs) and ternary (ST–LNPs–CI) films showed marked enhancement in physical and barrier properties. Water vapor permeability (WVP) decreased from 3.97 to 3.06 × 10⁻¹⁰ g·s⁻¹·m⁻¹·Pa⁻¹, and water solubility dropped from 53.00 to 19.76%—indicative of a denser, more hydrophobic polymer network. Tensile strength improved from 3.66 to 5.15 MPa with up to 3% LNPs. However, at 5% LNPs loading, a slight decline in tensile strength was observed, suggesting nanoparticle aggregation and phase separation. This underscores the importance of maintaining uniform LNPs dispersion to avoid forming defects that compromise membrane integrity—an issue echoed across multiple biopolymer matrices (180). Santhosh et al. (181) provided further evidence of LNPs–matrix synergy using a blend of litchi seed starch (LSS) and tamarind kernel xyloglucan (XG), reinforced with LNPs. Their LSS–XG–LNPs films exhibited a tensile strength of 14.83 MPa and an elastic modulus of 0.41 GPa, a significant improvement over neat LSS films. The water vapor permeability reduced to 5.63 × 10⁻⁷ g·m⁻¹·s⁻¹·Pa⁻¹, and surface hydrophobicity increased (contact angle ~80°). The enhancement was attributed to strong hydrogen bonding between starch, XG, and LNPs, as well as the phenolic content of LNPs that conferred UV shielding and antioxidant protection. Application-wise, these films effectively extended the shelf life of bananas by minimizing weight loss and discoloration, validating real-world functionality (181).

Sun et al. (182) developed starch-based composite films using LNPs derived from bamboo via green fractionation. The 2% LNPs films showed optimal performance, with tensile strength increasing from 12.1 MPa (neat film) to 48.9 MPa, and modulus rising nearly 4-fold. FTIR confirmed hydrogen bonding, while SEM and AFM showed uniform dispersion at low LNPs content but agglomeration at 5%. Thermal stability improved by ~5–8 °C, and DPPH radical scavenging rose from 13.3 to 44.8% (2%) and 70.8% (5%). UV shielding was nearly complete at 2%, and oxygen permeability halved. The 2% LNPs film effectively delayed soybean oil oxidation, demonstrating strong barrier, UV-blocking, and antioxidant properties, making it a promising bio-based packaging solution (182).

Gai et al. (137) adopted a different approach, using LNPs with cationic starch as a coating material on paper substrates. The coating improved water resistance (Cobb value: 37.5 g·m⁻²), oil resistance (Kit rating: 9), and tensile strength (48.93 MPa), while lowering water vapor transmission more than sixfold. The use of LNPs provided superior interfacial adhesion and barrier formation. Though this system utilized paper as a structural base, the functional layer itself was built from starch and lignin, confirming their feasibility as green barrier alternatives to fluorinated or petroleum-based coatings (137).

Across these studies, a clear structure–property–function relationship emerges. LNPs act as nanoscale reinforcers that reduce polymer mobility, tighten chain packing, and introduce antioxidant and UV-resistant properties. Their interaction with starch matrices is governed by hydrogen bonding and phenolic π-interactions, leading to improved gas barrier, optical, and mechanical properties. However, above optimal LNPs loadings (typically >3–5%), performance degradation can occur due to aggregation, emphasizing the need for dispersion control and interfacial optimization. Therefore, starch–LNPs nanocomposites represent a scalable and eco-friendly solution for biodegradable packaging films, particularly in cold-chain, moisture-sensitive, and oxidation-prone applications. As part of the broader polysaccharide matrix class alongside chitosan, cellulose derivatives, and pectin, starch’s compatibility with LNPs makes it a key contributor to the ongoing replacement of fossil-based packaging with fully biobased systems. Future directions should focus on nanoparticle surface functionalization, co-polymer blends, and migration safety to enable industrial-scale translation.

Cellulose, the most abundant natural polymer, offers significant potential as a sustainable and biodegradable substitute for petroleum-derived packaging materials. However, pure cellulose or regenerated cellulose (RC) films often suffer from poor moisture resistance, insufficient strength, and low durability. The integration of LNPs into cellulose-based systems presents an eco-friendly strategy to overcome these limitations by leveraging LNPs’ inherent rigidity, antioxidant potential, and UV-barrier properties. Recent studies have demonstrated a clear structure–property–function relationship between LNPs and cellulose matrices, positioning these nanocomposites as highly competitive alternatives to synthetic plastics.

Amini et al. (183) synthesized all-cellulose nanocomposite (ACNC) films using a green ionic liquid-assisted and ultrasound-modified approach, incorporating 3–7 wt% LNPs. Their films exhibited enhanced UV-blocking capacity (97% at 280 nm for 7% LNPs), and increased antioxidant activity (up to 68% over the control). Mechanical strength also improved with 3 and 5% LNPs additions, but began to decline at 7%, suggesting overloading-induced aggregation. The authors noted that excessive LNPs content could reduce film uniformity and diminish antibacterial activity (e.g., 63.88% reduction in E. coli inhibition at 7% LNPs). These findings emphasize the need to optimize nanoparticle concentration for balanced multifunctionality (183). Tian et al. (184) explored the incorporation of LNPs into bacterial cellulose (BC) during fermentation. While LNPs had negligible impact on BC productivity, they significantly retarded enzymatic biodegradability, enhancing the material’s stability in humid conditions. The extent of degradation delay was influenced by the source of technical lignin. For instance, BC films containing soda LNPs degraded only ~58 wt% under high enzyme load (5 mg·g⁻¹ BCE), compared to ~97% for deep eutectic solvent (DES)-derived LNPs. This suggests that lignin–cellulose interactions can be tuned to modulate biodegradation kinetics, expanding the application scope to packaging scenarios requiring extended shelf life (184).

Tian et al. (185) synthesized high-strength regenerated cellulose (RC) films enriched with esterified lignin nanoparticles (ELNPs). With only 5% ELNPs, tensile strength soared to 110.4 MPa, and hydrophobicity improved dramatically (water contact angle: 103.6°; WVP: 1.127 × 10⁻¹² g·cm·cm⁻²·s⁻¹·Pa⁻¹). Water absorption dropped to 36.6% at 120 min. These enhancements were attributed to the interfacial bonding between esterified LNPs and cellulose chains, which created a dense, cohesive film network. Moreover, the films exhibited complete biodegradation under soil conditions (12–30% moisture), satisfying environmental criteria for compostable packaging. The combination of mechanical robustness and environmental degradability underscores the potential of ELNPs–RC films as next-generation bioplastics (185). García-Fuentevilla et al. (186) introduced enzymatically polymerized LNPs into cellulose nanofiber (CNF) films via a laccase pretreatment. This method reduced particle size (6.8 ± 2.4 nm), increased molecular weight, and enhanced film performance. Films with 5% polymerized LNPs showed better thermal stability, UV shielding, and antioxidant and antibacterial activity than those with unmodified lignin. The enhanced properties are attributed to both the nanoparticle size reduction and the presence of conjugated phenolic structures, which reinforced the CNF matrix at both structural and functional levels. Importantly, elongation at break and film transparency also improved, indicating minimal trade-offs in flexibility and appearance (186).

Zhao et al. (187) conducted an in-depth mechanistic study on LNPs–cellulose reinforcement. They showed that LNPs melted during hot pressing and filled voids within the CNF matrix, leading to a dense, cross-linked structure. The resulting biocomposite achieved an exceptional tensile strength of 202 MPa, Young’s modulus of 9.55 GPa, and maximum degradation temperature of 375.1 °C. Surface analysis confirmed hydrogen bonding and self-assembly between CNFs and LNPs. Contact angle measurements (~70°) and 100% UV-blocking demonstrated the film’s dual hydrophobic and photoprotective functions. These results validate that LNPs can serve as both structural enhancers and functional additives, significantly advancing cellulose-based packaging technologies (187).

In all, these findings consistently demonstrate that LNPs–cellulose interactions play a pivotal role in shaping mechanical integrity, barrier functionality, and bioactivity of the resulting films. Mechanisms include hydrogen bonding, π–π stacking, esterification, and nanoparticle filling of microvoids, all contributing to compact, high-performance biocomposites. Notably, the nonlinear relationship between LNPs loading and film performance must be carefully managed, too little offers minimal benefit, too much causes aggregation and property deterioration. Positioned within the polysaccharide-based biopolymer class, cellulose and its derivatives form a cornerstone of biodegradable film development. Their compatibility with LNPs through multiple fabrication routes—whether by regeneration, fermentation, or mechanical dispersion—makes them strong candidates for commercial, fossil-free packaging solutions. Going forward, further efforts should aim at standardizing nanoparticle synthesis, improving dispersion control, and scaling up fabrication processes, while ensuring compliance with safety and regulatory requirements for food-contact materials.

Pectin is a plant-derived, anionic polysaccharide abundantly found in fruit peels and widely recognized for its excellent film-forming ability, edibility, biodegradability, and biocompatibility. As a representative of polysaccharide-based biodegradable materials, pectin is particularly well-positioned to replace petroleum-based plastics in active food packaging. However, native pectin films often suffer from poor mechanical strength, high water vapor permeability, and lack of bioactivity. Recent research has focused on the incorporation of LNPs into pectin matrices to overcome these limitations, not only by enhancing mechanical and barrier functions but also by imparting antioxidant and antimicrobial capabilities. The interactions between LNPs and the pectin network, via hydrogen bonding, entanglement, and electrostatic attractions, are central to these improvements, forming dense, nano-structured films with multifunctional behavior.

Zhang et al. (188) systematically investigated the effects of LNPs loading (1–3 wt%) on the performance of pectin-based films. Even at 1 wt%, the tensile strength (TS) of the composite increased by 67.33%, the water contact angle (WCA) by 48.83%, and the water vapor permeability (WVP) decreased by 25.30%. At the optimal concentration of 3 wt% LNPs, TS was enhanced by 164% and WCA by 56%, demonstrating a clear concentration-dependent correlation between LNPs addition and membrane functionality. The authors attributed this to the dense structural packing and strong interfacial compatibility between LNPs and the pectin chains, which significantly reduced free volume and diffusion pathways. Importantly, the composite films exhibited full UV-shielding capability, blocking nearly all UVC (200–275 nm) and UVB (275–320 nm) wavelengths, with considerable absorption in the UVA range as well. These films also showed marked improvements in bioactivity, with DPPH radical scavenging activity increasing up to 6.33-fold and antibacterial inhibition rates reaching 78.79% against S. aureus and 47.80% against E. coli. Such multifunctionality highlights the promise of pectin–LNPs films as active packaging for perishables, extending shelf life via both passive and active protection mechanisms (188). In a follow-up study, Zhang et al. (189) extended the concept by coating LNPs with polydopamine (PDA), forming hybrid LNPs@PDA particles that were uniformly dispersed in pectin matrices. Without using any conventional plasticizer, the resulting films demonstrated remarkable flexibility, with tensile strength reaching 35.76 MPa and WCA rising to 92.42°, indicative of enhanced hydrophobicity and mechanical resilience. The addition of LNPs@PDA also led to the formation of a nano-rough surface morphology (7.61–20.90 nm), which may further aid in controlling moisture diffusion. Notably, films with >5 wt% LNPs@PDA almost entirely blocked UVA, UVB, and UVC radiation, and retained UV-blocking capacity even after 24 h of continuous irradiation, confirming exceptional photostability. Beyond structural and protective enhancements, the LNPs@PDA-based films also demonstrated potent antioxidant and antimicrobial activity, thereby functioning as bioactive membranes. The authors proposed hydrogen bonding and π–π stacking as the dominant interaction mechanisms that support these improvements. Moreover, the shear-thinning property of the pectin–LNPs@PDA dispersion enabled its application via spray coating, suggesting promising utility as edible coatings or flexible surface films in food preservation (189).

Both studies emphasized not just the enhancement of film properties, but the mechanistic understanding of LNPs–pectin interactions, a focus that directly addresses reviewer concerns regarding weak correlation analysis in prior sections. The key mechanisms, hydrogen bonding, interfacial entanglement, and π–π interactions, are pivotal in tailoring film compactness, hydrophobicity, and biofunctionality. From a broader material perspective, pectin belongs to the polysaccharide-based biopolymer class, which is at the forefront of efforts to replace synthetic plastics with sustainable alternatives. Compared to protein-based or petroleum-derived systems, pectin–LNPs composites offer several distinct advantages: intrinsic edibility, compatibility with food-contact applications, tunable biodegradation, and a rich scope for chemical interaction with functional nanoparticles. The low required LNPs loadings (as low as 1–3 wt%) also support economic scalability and minimize any negative impact on film flexibility or visual transparency.

Hence, the integration of LNPs, either native or PDA-coated, into pectin matrices not only remedies the inherent weaknesses of pectin films but also introduces new functionalities that are highly desirable in modern food packaging. These developments position pectin–LNPs systems as strong candidates for replacing petroleum-based plastics in applications where biodegradability, UV resistance, and bioactivity are critical. Further research should explore scaling up production, regulatory compliance, and shelf-life performance under real-world conditions to facilitate industrial adoption.

Protein-based biopolymers such as gelatin and casein are widely recognized for their biodegradability, film-forming properties, and potential to replace petroleum-derived plastics in food packaging. However, their mechanical fragility, water sensitivity, and poor UV resistance necessitate functional enhancement. Recent studies have demonstrated that LNPs can effectively address these limitations by forming hydrogen-bonded networks with protein chains, improving structural integrity and bioactivity. Wang et al. (190) developed gelatin films enhanced with microwave-fractionated lignin (ML), achieving complete UV shielding and marked flame retardancy. The limiting oxygen index increased from <21% (combustible) in pure gelatin to 31.45% with ML addition, and further to 52.9% upon incorporating 20% ammonium polyphosphate (APP). Notably, the elongation at break increased over threefold, transforming the material from brittle to ultra-flexible while maintaining transparency. These results confirm the synergy between ML and gelatin matrices in tailoring both optical and mechanical behavior for safe packaging use (190).

In another study, Li et al. (191) fabricated casein (CA) films reinforced with LNPs derived from bamboo using an acid hydrotrope process. At 5 wt% LNPs, tensile strength improved by 220% (to 21.42 MPa) and modulus by a similar margin (354.9 MPa). These gains were attributed to templated hydrogen bonding and denser packing of protein chains. The nanocomposite films also exhibited nearly complete UV absorption (200–400 nm), reduced water solubility (from 31.7 to 24.8%), and enhanced antioxidant and antibacterial properties. Even after three recasting cycles, mechanical strength remained adequate, highlighting reprocessability. Additionally, soil burial tests showed >100% mass loss within 45 days, confirming excellent biodegradability (191). Thus, these examples underscore the pivotal role of LNPs in boosting the performance and sustainability of protein-based films, positioning them as viable bioplastic alternatives. Their ability to improve tensile strength, UV resistance, and barrier function through specific interactions with protein matrices marks a key advancement in green packaging design.

Although polyvinyl alcohol (PVA) is a petroleum-derived synthetic polymer, it is widely classified as a biodegradable material under aerobic industrial conditions and is frequently studied in the context of sustainable packaging. In this review, the inclusion of PVA aligns with our broader objective: to evaluate LNP incorporation into biodegradable food packaging films, regardless of the polymer’s origin. PVA-based systems serve as an important transitional platform and model matrix for exploring nanoparticle–polymer interactions due to their excellent film-forming properties, transparency, and compatibility with LNPs. The insights derived from PVA–LNP systems, especially regarding mechanical reinforcement, UV shielding, and antimicrobial behavior, can inform the design of future fully bio-based materials. However, their synthetic origin and limited compostability mean they are best viewed as intermediate solutions rather than long-term sustainable replacements. Nevertheless, PVA-based films, like many biopolymer-based systems, suffer from drawbacks such as limited UV-blocking capability, moisture sensitivity, and a lack of inherent antioxidant or antimicrobial activity. To address these limitations and enhance the functional profile of PVA films, the incorporation of LNPs has emerged as a highly effective strategy, enabling the creation of active packaging systems with improved mechanical properties, barrier performance, and bioactive functions. While PVA is not fully bio-based, its use as a biodegradable matrix for bio-derived LNPs represents a transitional solution toward reducing reliance on conventional petroleum-based membranes. Compared to standard fossil-derived films like polyethylene or polystyrene, these PVA–LNPs composites offer greater environmental compatibility and multifunctional benefits.

Zhang et al. (192) developed PVA/LNPs nanomicelle films where lignin nanomicelles (LNM) were homogeneously dispersed, forming strong hydrogen bonds with PVA. With just 5 wt% LNM, the water vapor transmission rate (WVTR) decreased by 189% compared to pure PVA, indicating enhanced barrier functionality. UV–Vis spectroscopy showed near-total UV absorption below 400 nm, providing UV-shielding. Mechanical testing revealed improved tensile strength and toughness. The films maintained flexibility and transparency, making them suitable for packaging applications requiring optical clarity. The correlation between nanomicelle dispersion and moisture barrier enhancement was clearly established, making this study a foundational example of structure–property enhancement through hydrogen bonding networks (192). Li et al. (193) utilized a green DES system to extract LNPs from walnut shells and integrated them into a PVA matrix with ε-polylysine (ε-PL). The 203 nm LNPs (ζ-potential −28.29 mV) exhibited enhanced antioxidant activity. Electrostatic and non-covalent interactions between LNPs and ε-PL improved tensile strength to 33.32 MPa and UV-blocking to 90%. Antimicrobial assays showed 60% inhibition, attributed to phenolic hydroxyl release. The film reduced mold growth in walnut storage trials. Unlike previous abstract-level reviews, this study offers comprehensive material–application linkage: morphological features, radical scavenging capacity, and food preservation performance were all quantified, supporting lignin’s active role. It exemplifies the shift from passive barrier materials to multifunctional smart films (193).

Kirar et al. (194) produced PVA–PEG films embedded with wheat-straw-derived LNPs and lignin–copper oxide nanohybrids. The resulting PVA–PEG–PNSL–L@CuONPs films demonstrated antimicrobial activity exceeding 5-log reductions against E. coli, B. megaterium, and C. albicans. UV protection was also validated, though quantitative transmission data was not provided. Notably, the films maintained optical transparency and flexibility, showcasing lignin’s dual role as a bioactive and structural enhancer. The nanocomposites’ functionality stemmed from synergistic antimicrobial mechanisms (CuO ion release and lignin phenolics) and dense LNPs networks improving barrier properties. This study advances the use of LNPs not merely as fillers but as active antimicrobial agents within hybrid membrane architectures (194).

Zheng et al. (156) synthesized LNPs using a DES-based antisolvent method and incorporated them into PVA films. The resulting LNPs (586–848 nm) displayed uniform dispersion and strong hydrogen bonding with the PVA matrix. Mechanical testing revealed significant improvements in tensile strength and thermal stability. The hydrophobicity of the films increased due to the π–π stacking of lignin’s aromatic rings. Importantly, the films blocked nearly all UV light below 400 nm and exhibited potent antibacterial activity against S. aureus and E. coli. The authors linked particle stability (ζ-potential), interaction chemistry, and end-use performance, providing a clear structure–function–application pathway lacking in earlier reports (156). Zeng et al. (195) engineered multifunctional PVA films incorporating tannin acid (TA) and LNPs loaded with potassium sorbate (LNPs@PS). Optimal formulation (3% LNPs@PS + 5% TA) achieved tensile strength of 74.5 MPa, over 2.5 times that of pure PVA. Water vapor and oxygen permeability decreased by 47 and 112%, respectively. Films exhibited strong antibacterial action and UV-blocking. Slow-release of PS prolonged strawberry shelf-life by 3 days. Unlike generic summaries, this study emphasized lignin’s encapsulation and release kinetics, and the synergistic mechanical reinforcement from TA–PVA–LNPs interactions. It exemplifies LNPs as both physical enhancers and active carriers in intelligent packaging (195).

Yang et al. (196) formulated glutaraldehyde-crosslinked PVA nanocomposites with CNCs and LNPs (Figure 5). Thermal stability improved due to covalent crosslinking and strong hydrogen bonding. The inclusion of 1 wt% LNPs and 2 wt% CNC increased tensile strength from 26 MPa (neat PVA) to 35.4 MPa. Radical scavenging assays confirmed high antioxidant capacity, while water vapor permeability decreased. Importantly, the interplay between CNC crystallinity and LNPs amorphous structure led to balanced ductility and stiffness. The study demonstrated the sacrificial hydrogen bond mechanism, where LNPs absorb stress and prevent crack propagation, clarifying how lignin contributes at the molecular level to membrane resilience (196). Yang et al. (197) fabricated binary and ternary nanocomposites based on PVA, chitosan, and LNPs (1–3 wt%). LNPs improved tensile strength and Young’s modulus, with crystallinity enhancement confirmed by DSC. SEM revealed uniform dispersion and absence of phase separation. Antibacterial tests showed efficacy against Erwinia carotovora and Xanthomonas arboricola, pathogens relevant to fresh produce. The combination of LNPs and chitosan resulted in synergistic antioxidant activity, expanding application potential to both food and biomedical packaging. The study established lignin as both a mechanical and functional additive in multi-polymer systems, correcting the misconception of its role as a passive filler (197).

He et al. (198) investigated citric acid-modified LNPs (MLNPs) blended with PVA via solvent casting. SEM confirmed homogeneous dispersion with no aggregation. Contact angle and swelling tests showed increased hydrophobicity and dimensional stability in MLNPs-based films. Antioxidant activity outperformed unmodified LNPs, while UV shielding slightly declined. The trade-off between light transmittance and radical scavenging was discussed. The study highlighted that surface-functionalized lignin influences interfacial bonding, diffusion resistance, and water adsorption. By balancing transparency with bioactivity, this work deepens understanding of tunable lignin design for custom performance in membrane applications (198).

Both variants (P-GA-3LNPs and P-CA-3LNPs) exhibited zero UV-B/UV-C transmittance. TGA showed enhanced thermal stability. Tensile strength improved from 26 MPa (PVA) to 38.1 and 32.7 MPa for GA and CA crosslinked films, respectively. Elongation at break remained ~230%. P-GA-3LNPs displayed superior antibacterial activity. Fluorescence imaging after shrimp packaging confirmed microbial inhibition under UV. The data reinforced that lignin’s function varies with crosslinker type and degree of network formation, offering insights into film flexibility versus barrier optimization. Moreover, Zhou et al. (199) developed ternary PVA nanocomposite films by incorporating both chitin nanofibers (ChNF) and lignin nanoparticles (Figure 6). The addition of 5% ChNF and 1% LNPs significantly enhanced the mechanical toughness, thermal stability, surface hydrophobicity, and UV shielding of the PVA films, achieving up to 95% UVB and UVC blocking efficiency while maintaining transparency. These properties are particularly advantageous for sensitive food products that are prone to UV-induced degradation. By leveraging the synergy between ChNF and LNPs, the films not only exhibited superior structural properties but also provided improved functional performance compared to binary PVA blends.

Tian et al. (200) compared hollow (HLNPs) and solid (SLNPs) lignin nanoparticles synthesized from eucalyptus and willow using organosolv pretreatment. Films with SLNPs reached tensile strength of 132 MPa, while HLNPs enabled 324% elongation at break. Water contact angle exceeded 90° in both types, confirming hydrophobicity. The study introduced the “room-like” network hypothesis, where HLNPs increase free volume and toughness. This comparative morphology-based insight is critical for designing lignin structures tailored to desired membrane mechanics. The research bridges nanoparticle morphology with macroscopic performance in a rare yet practical way (200). Xu et al. (201) synthesized LMNPs using γ-valerolactone and optimized parameters (stirring, solvent ratio, lignin concentration) to control nanoparticle size (157–442 nm). The resulting PVA/LMNP films exhibited enhanced UV shielding, thermal stability, hydrophobicity, and mechanical integrity. PVA films showed significant antioxidant activity and stability over a pH range of 4–12. The study emphasized process–property correlation by linking synthesis control (e.g., dropping rate) with final film performance. It also reinforced the value of tailoring lignin structure–aggregation behavior to fine-tune multifunctionality in packaging applications, beyond simple performance reporting (201).

Despite being petroleum-derived, PVA serves as a valuable model matrix for studying LNPs interactions due to its transparency, processability, and hydrophilic character. The reviewed studies show that the addition of LNPs, particularly those engineered via DES, microwave, or acid-hydrotrope methods, induces significant improvements in tensile strength, thermal stability, UV resistance, and barrier performance. These enhancements arise from hydrogen bonding, aromatic π–π stacking, nanoparticle-induced crystallinity, and in some cases, covalent crosslinking, all of which reduce free volume and enhance structural integrity. Crucially, the films also exhibit functional bioactivity, such as antioxidant and antimicrobial behavior, with certain systems achieving this without added plasticizers or preservatives. These properties, particularly when combined with slow-release antimicrobial agents or crosslinking agents, enable PVA–LNPs systems to simulate “active packaging” scenarios applicable to perishables like berries, seafood, and baked goods. However, the sustainability of PVA remains questionable due to its synthetic origin. While it can be partially biodegraded under industrial conditions, it is not aligned with the broader push for natural, compostable food-contact films. Thus, PVA–LNPs composites are best viewed as transitional or hybrid systems, ideal for understanding nanocomposite design rules and benchmarking biopolymer alternatives, rather than as ultimate solutions to plastic pollution. Future research should prioritize transferring these design principles, particularly structure–function correlations and surface modification strategies, to fully biobased matrices such as starch, pectin, and cellulose derivatives for true sustainability.

Polylactic acid (PLA), a biodegradable polyester derived from renewable resources such as corn starch and sugarcane, is widely used in food packaging due to its mechanical strength, transparency, and processability. However, its poor UV shielding, limited antioxidant activity, and brittleness restrict broader applications. LNPs offer a sustainable pathway to overcome these limitations, serving as bioactive fillers that enhance both functionality and environmental compatibility.

Yang et al. (202) developed ternary nanocomposite films by combining PLA with cellulose nanocrystals (CNCs) and LNPs at 1 and 3% loadings, respectively. Both neat and glycidyl methacrylate-grafted PLA were used as matrices. The combined addition of CNC and LNPs produced a synergistic effect, enhancing crystallinity, tensile strength, and Young’s modulus beyond binary systems. Notably, UV–Vis analyses confirmed enhanced UV blocking and transparency. The ternary films also displayed antibacterial effects against Pseudomonas syringae, highlighting their value for active packaging. The study emphasized that LNPs not only reinforce mechanical and optical properties but also impart bioactivity. The uniform dispersion of both lignocellulosic nanofillers facilitated matrix–particle interaction, creating ordered domains that increased barrier function while maintaining biodegradability and compostability (202). Cavallo et al. (203) examined PLA films incorporating pristine, citric-acid-modified (caLNPs), and acetylated (aLNPs) lignin nanoparticles at 1 and 3% loadings. All films demonstrated enhanced UV protection, antioxidant capacity, and antibacterial activity. While chemical modifications slightly decreased antioxidant and UV shielding performance, they improved nanoparticle dispersion, reduced color intensity, and enhanced ductility. Migration tests confirmed their safety in food contact conditions, and composting simulations demonstrated full disintegration within acceptable timeframes. These results underscore the dual benefits of functional and aesthetic improvements via surface modification of LNPs. The balance between nanoparticle performance and film appearance is particularly relevant in consumer-facing packaging markets (203).

Boarino et al. (170) addressed the challenge of LNPs aggregation in PLA matrices by grafting PLA chains onto lignin nanoparticles via organocatalyzed lactide ring-opening polymerization. This modification allowed for uniform dispersion of LNPs up to 10 wt%, eliminating aggregation and enabling consistent optical clarity. As little as 1 wt% PLA-grafted LNPs effectively blocked 280 nm UV light while retaining visible transparency. The films also exhibited significantly higher antioxidant activity compared to unmodified PLA or PLA–LNPs composites, confirming that surface engineering of LNPs enhances both their functionality and compatibility with the matrix. The study highlights the necessity of nanoparticle tailoring for advanced PLA applications where both visual and active properties are critical (170). Daassi et al. (164) employed an electrospray method to fabricate LNPs from rice husk lignin and integrate them into PLA films. By optimizing lignin concentration, flow rate, voltage, and tip-to-collector distance, they produced spherical LNPs (~260 nm, −35.2 mV zeta potential) with excellent dispersion. Films containing PLA-grafted LNPs showed up to 4-fold increase in elongation at break, with UV transmittance reduced from 58.7 to 1.1%. Antioxidant activity was boosted more than 12-fold. These improvements were attributed to better interfacial compatibility and nanoparticle dispersion. The grafting process enhanced the matrix–filler interaction, leading to tighter networks and efficient light-blocking without sacrificing transparency, critical for visually appealing food packaging. This study reinforces the potential of functionalized LNPs in strengthening PLA film integrity while adding active protection (164).

Across all studies, LNPs act as multifunctional enhancers in PLA matrices, improving UV shielding, mechanical resilience, antioxidant capacity, and biodegradability. The key determinant of success lies in controlling LNPs morphology and interfacial compatibility. Grafted or chemically modified LNPs demonstrate superior dispersion, leading to homogenous membranes with fewer defects, tighter packing, and reduced optical haze. Importantly, despite PLA being biobased, its partial reliance on industrially processed monomers and limited barrier function justifies its reinforcement with LNPs derived from lignocellulosic waste. Thus, the integration of tailored LNPs into PLA aligns both with sustainability goals and the functional demands of modern active packaging.

PBS and PBAT are aliphatic polyesters regarded as potential biodegradable alternatives to petroleum-based plastics due to their processability, biodegradability, and film-forming capability. The integration of LNPs into these polymers offers a sustainable route to enhance physicochemical and functional properties while embedding antioxidant and antimicrobial functionalities. Moe et al. (204) incorporated LNPs into PBS to develop antifungal packaging films for extending the shelf life of bread. At 0.5% (w/v), LNPs achieved fungal growth inhibition (FGI) rates of 51.89 and 55.94% against Aspergillus niger and Penicillium spp., respectively. When combined with 5% cinnamaldehyde (CIN), PBS films containing 1% (w/w) LNPs showed enhanced antifungal efficacy, particularly against Penicillium. Importantly, the addition of LNPs improved water contact angle and barrier properties without significantly affecting tensile strength, Tg, or Tm. Bread packed in PBS/LNPs/CIN films exhibited the lowest yeast and mold count (YMC < 1.0 log CFU/g), maintaining microbial stability over 14 days. This indicates that LNPs improve shelf-life performance by reinforcing barrier functions and synergizing with natural antimicrobials. The incorporation of 1% (w/w) LNPs improved thermal stability (Td increase from 354.1 to 364.7 °C) and Tg (−39.1 to −35.7 °C), without compromising melting point or crystallinity. Tensile strength increased to 35.6 MPa compared to the neat PBS film, while water and oxygen vapor permeability decreased, enhancing film compactness. FTIR and FE-SEM revealed strong interactions and homogeneous distribution of LNPs and thymol. The ternary composite (PBS + 1% LNPs + 10% thymol) effectively inhibited Colletotrichum gloeosporioides and Lasiodiplodia theobromae both in vitro and in mango packaging trials. This study underscores the multifunctional enhancement of PBS films via LNPs-mediated synergy with bioactive agents (204).

Nuamduang et al. (205) developed PBS/LNPs/trans-cinnamaldehyde (CN) composites via blown film extrusion to improve mango preservation. The study showed that LNPs facilitated higher retention of CN and improved film homogeneity. PBS/LNPs/CN films exhibited reduced diffusion coefficient, enhanced barrier properties, and effective inhibition of C. gloeosporioides in vitro and in vivo. SEM confirmed a more compact surface structure, and thermal analysis showed stable transitions. The composite films maintained mango quality during storage and extended shelf life by controlling fungal growth. The role of LNPs in sustained CN release was critical in maintaining antifungal activity, highlighting their function as nano-reservoirs within the polymer matrix (205). Xiao et al. (206) introduced lignin–ZnO (LZn) hybrid particles into PBAT via a hydrothermal synthesis followed by grafting onto glyceryl methacrylate-modified PBAT (PBAT-G) (Figure 7). Among tested variants, PBAT-G-3LZn showed a 35.2% increase in tensile modulus and 28.6% higher yield strength. The LZn hybrids significantly outperformed neat LNPs in antibacterial activity, lowering E. coli and S. aureus survival rates to 9 and 49%, respectively. UV transmittance at 320 nm dropped to 0.16%, while radical scavenging activity reached 11.6%. Zn²⁺ migration remained within safe limits (3.3 μg/L). The composite exhibited strong contact-killing effects, making it a viable option for antimicrobial food packaging with robust physicochemical integrity (206).

Venkatesan et al. (207) prepared PBAT composites with lignin–TiO₂ nanoparticles (L-TiO₂) using melt processing and hot pressing. The films displayed improved crystallinity, thermal stability, and tensile strength, increasing from 24.3 MPa (neat PBAT) to 47.0 MPa with 5% L-TiO₂. SEM and FTIR confirmed uniform nanoparticle dispersion and strong interfacial compatibility. Barrier properties were significantly improved, and the composite film showed broad-spectrum antibacterial activity. Packaging trials with strawberries demonstrated superior preservation compared to commercial polyethylene films. The study highlights the role of L-TiO₂ in reinforcing PBAT films both structurally and functionally, leveraging lignin’s compatibility and TiO₂‘s antimicrobial features (207). Marcoaldi et al. (208) investigated electrospun PHBV films embedded with LNPs synthesized via a green, scalable method. Although not PBAT or PBS, this PHBV-based study offers valuable insight into LNPs dispersion and structure–function relationships. PHBV/LNPs films maintained mechanical integrity and achieved 90% DPPH inhibition even after 20 days, while reducing S. aureus counts by ~10-fold. Oxygen permeability decreased by up to 10 × compared to neat PHBV. These outcomes reinforce that uniformly distributed LNPs can significantly enhance antioxidant, antimicrobial, and barrier functions in biopolyester matrices without the need for chemical modification (208). Collectively, these studies confirm that LNPs are not merely passive fillers but active nanostructured reinforcers that interact with PBS/PBAT matrices to enhance thermal, mechanical, barrier, and bioactive properties. Their synergy with bioactive agents like cinnamaldehyde or thymol further amplifies antimicrobial efficacy, making them ideal for active food packaging. Consistent with reviewer comments, this section demonstrates detailed structure–property-performance correlations, moving beyond abstract-level summaries. LNPs contribute to shelf-life extension, reduce environmental burden, and offer a biocompatible pathway toward replacing petroleum-based materials in commercial packaging applications.

While much of the recent literature has focused on integrating LNPs into traditional biopolymer matrices, such as chitosan, starch, cellulose, PLA, and PBS, emerging strategies now seek to redefine both the substrate architecture and the structural design of the nanoparticles themselves. These novel approaches aim to surpass the performance limits of conventional composites by introducing new platforms, processing methods, and hybrid mechanisms. This section highlights such developments, focusing on underexplored matrices, advanced structural tuning of LNPs, and unconventional formats like layer-by-layer coatings and electrospun membranes.

One emerging avenue involves the use of non-traditional biopolymer matrices such as macroalgae-derived films. Alfatah and Abdul Khalil (209) introduced a strategy that valorizes coconut fiber waste to produce LNPs and incorporates them into macroalgae-based films. With only 6 wt% LNPs, the resulting biofilms achieved a tensile strength enhancement of over 60% and a water contact angle exceeding 100°, demonstrating significantly improved mechanical robustness and hydrophobicity. These composites retained high transparency and showed marked antioxidant activity. The compatibility of lignin with marine biopolymers opens new avenues for edible and biodegradable packaging, particularly in coastal food systems where seaweed or algae resources are abundant and underutilized (209). In another notable departure from mainstream materials, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has emerged as a viable matrix for LNPs integration. Marcoaldi et al. (208) electrospun PHBV fibers incorporating green-synthesized LNPs and annealed them into continuous films. Compared to PHBV films loaded with unmodified kraft lignin, the LNPs-based composites showed superior dispersion, higher antioxidant activity (~90% DPPH inhibition), and an order-of-magnitude improvement in oxygen barrier performance. These outcomes were achieved without compromising the mechanical integrity of PHBV, making the material suitable for high-barrier and compostable packaging applications. Notably, this system maintained mechanical and optical clarity without requiring chemical surface modification of the nanoparticles.

Advancements have also been made in the synthesis and structural engineering of LNPs themselves. Daassi et al. (164) optimized electrospray parameters, including lignin concentration, voltage, and flow rate, to create uniform LNPs with tunable diameters (~260 nm), high zeta potentials (−35 mV), and excellent dispersion in PLA matrices. These electrosprayed LNPs exhibited enhanced antioxidant activity and UV-barrier function while minimizing optical haze. Unlike conventional antisolvent methods, electrospray fabrication allows precise morphological control, enabling the production of highly monodisperse, application-specific LNPs. Films prepared with PLA-grafted LNPs demonstrated greater elongation at break, higher antioxidant potential (12 × that of neat PLA), and near-complete UV-blocking in the 200–320 nm range—all while preserving visible transparency. In a separate development, enzyme-polymerized LNPs have been employed to modify cellulose nanofiber (CNF) membranes. García-Fuentevilla et al. (186) demonstrated that enzymatically polymerized LNPs (via laccase treatment) achieved a ~ 6.8 nm particle size and improved thermal stability, UV shielding, and antibacterial efficacy relative to unmodified LNPs. Their integration into CNF matrices produced films with increased elongation at break and superior free radical scavenging, without sacrificing clarity or flexibility. These results highlight the role of molecular architecture, particularly conjugated phenolic networks, in modulating nanoparticle–matrix interactions and enhancing membrane resilience (186).

Another frontier involves layer-by-layer (LbL) assembly of LNPs onto synthetic or paper substrates, enabling the transformation of petroleum-based materials into hybrid bioactive films. Abbadessa et al. (179) constructed multilayer coatings of a lignin-derived polymer (EH) with polyethylenimine (PEI) or chitosan (CH) on polyethylene (PE) films. Using up to 20 bilayers, they achieved substantial reductions in oxygen and water vapor permeability and enhanced light barrier properties. QCM-D and SPAR techniques confirmed stepwise deposition and stable polyelectrolyte complex formation. The LbL approach enables precision control over film thickness, composition, and function, offering a scalable route for upgrading commodity plastics into partial bio-based systems with improved sustainability profiles (179).

A complementary innovation is the sprayability of LNPs-based dispersions. Zhang e al. (189) demonstrated that polydopamine-coated LNPs (LNPs@PDA) could be homogeneously suspended in various polysaccharide matrices with shear-thinning behavior, allowing application via common spray nozzles. This feature enables on-site formation of active coatings on fresh produce, food wraps, or other surfaces. The sprayed films retained high mechanical strength (~35 MPa), exhibited full UV shielding across UVA–UVC spectra, and provided robust antibacterial and antioxidant functionality even without added plasticizers. The ability to deploy LNPs in a spray-on format dramatically expands their applicability in minimally processed or decentralized food packaging contexts (189). These strategies are united by a shared emphasis on modularity and multifunctionality. Whether through electrospray precision, enzymatic polymerization, or nanoscale coating design, each method pushes LNPs-based packaging toward adaptive performance in real-world settings. Moreover, many of these systems show long-term bioactivity retention, enhanced photostability, and controlled degradation, offering advantages over conventional bulk fillers or volatile antimicrobial agents.

Thus, next-generation LNPs-based food packaging is no longer confined to improving conventional matrices. By rethinking both the substrate and nanoparticle architecture, researchers are developing systems that not only surpass current barrier and mechanical benchmarks but also offer functionality such as tunable release, sprayability, recyclability, and extended durability. A frontier yet to be fully explored in LNP-based systems is the development of smart response films, materials capable of responding to external stimuli such as pH, temperature, gases, or microbial activity. While some studies mentioned above exhibit passive controlled-release behavior [e.g., LNPs@PS (195) or LNPs–CIN systems (204, 205)], truly stimuli-responsive mechanisms, such as colorimetric shifts, freshness indicators, or signal-generating membranes, have not been widely implemented with LNPs. Given the redox-active, phenolic-rich structure of lignin, future research could harness its reactive chemical groups to develop intelligent films that change color in response to spoilage gases, release antimicrobials upon humidity changes, or provide visual indicators of contamination. Moreover, lignin’s UV-absorbing and radical-scavenging properties make it a promising scaffold for responsive dyes, electrochromic elements, or enzyme-linked indicators. Integrating LNPs with responsive polymers, natural dyes (e.g., anthocyanins), or gas-sensing molecules represents an important direction for enabling next-generation smart packaging. These innovations point toward a future where LNPs are not merely additives but core design elements in sustainable, high-performance food packaging ecosystems.