Tannic-Acid-Enriched Poly(vinyl alcohol) Nanofibrous Membrane as a UV-Shie lding and Antibacterial Face Mask Filter Material

"Green" Cross-Linking of Poly(Vinyl Alcohol)-Based Nanostructured Biomaterials: From Eco-Friendly Approaches to Practical Applications

Recently, a growing need for sustainable materials in various industries, especially biomedical, environmental, and packaging applications, has been observed. Poly(vinyl alcohol) (PVA) is a versatile and widely used polymer, valued for its biocompatibility, water solubility, and easy processing, e.g., forming nanofibers via electrospinning. As a result of cross-linking, PVA turns into a three-dimensional structure-hydrogel with unusual sorption properties and mimicry of biological tissues. However, traditional cross-linking methods often involve toxic chemicals and harsh conditions, which can limit its eco-friendly potential and raise concerns about environmental impact. "Green" cross-linking approaches, such as the use of natural cross-linkers, freeze-thawing, enzymatic processes, irradiation, heat treatment, or immersion in alcohol, offer an environmentally friendly alternative that aligns with global trends toward sustainability. These methods not only reduce the use of harmful substances but also enhance the biodegradability and safety of the materials. By reviewing and analyzing the latest advancements in "green" PVA cross-linking approaches, this review provides a comprehensive overview of current techniques, their advantages, limitations, and potential applications. The main emphasis is placed on PVA nanostructured forms and applications of PVA-based biomaterials in areas such as wound dressings, drug delivery systems, tissue engineering, biological filters, and biosensors. Moreover, this article will contribute to the broader scientific understanding of how the materials based on PVA can be optimized both in terms of "greener" and safer production, as well as adjusting the final platform properties.

Electrostatic spinning silver oxide/silver -loaded coconut fiber and tannic acid modified polylactic acid packaging film for fresh beef preservation

Due to its rich nutritional content, beef is highly susceptible to bacterial contamination and lipid oxidation, which can lead to spoilage. Therefore, it is essential to incorporate antibacterial and antioxidant agents into food packaging films. In this study, micro- and nano-coconut fibers (BW-C) were obtained with wall-breaking ultrasonic technology. Subsequently, silver oxide (Ag₂O) was deposited on BW-C via chemical method to get Ag2O-coconut fibers (BW-CA). Tannic acid‑silver oxide/silver-coconut fibers (TA-Ag₂O/Ag-BW-C) modified PLA films were prepared by electrostatic spinning technique, and applied to fresh beef sticker packaging. The characteristics of the films were evaluated through its appearance, mechanical properties, antibacterial activity, antioxidant properties, migration analysis, in vitro cellular assay analysis and beef freshness assessment. The results indicated that TA-Ag₂O/Ag-BW-C modified PLA films exhibited excellent mechanical properties. The films demonstrated excellent antibacterial activity against E. coli, S. aureus and A. niger, as well as remarkable antioxidant properties, attributed to the synergistic effects of Ag₂O/Ag and TA. Silver and TA were released stably over 18 days in three different food simulation solutions. The films had no significant cytotoxicity to intestinal epithelial cells (IECs) and had good biocompatibility. The beef preservation experiment showed that the films could significantly extend the shelf life of fresh beef stored at 4 °C. Compared to commercial polyethylene (PE) films, the films extended the shelf life of fresh beef by 3-5 days. The TA-Ag₂O/Ag-BW-C modified PLA films have great potential for application in beef preservation packaging.

Biodegradable Polyvinyl Alcohol (PVOH)-Based Films with Anthocyanin-Rich Extracts of Corozo (Bactris guineensis H.E. Moore) for Intelligent Packaging Design

Corozo (Bactris guineensis H.E. Moore) is a fruit from the Colombian Caribbean region valued for its thermostable anthocyanins, which are responsible for its characteristic reddish colour. This study aimed to evaluate the physicochemical, structural, and functional properties for an intelligent and biodegradable film design based on a polyvinyl alcohol (PVOH) matrix incorporating a Corozo extract rich in anthocyanins, with potential applications in food packaging. Anthocyanins were extracted from Corozo fruit and evaluated throughout a central composite design (CCD) for the effects of three variables-extraction time (t), temperature (T), and solvent concentration (CS). A quadratic model (R2 = 0.9586) demonstrated that the exocarp (peel) was the most effective source of anthocyanins. The best conditions were a 1:16.66 solid-to-solvent ratio at 50 °C for 75 min, yielding 38.65 mg EC3G/L. PVOH films were formulated using Corozo anthocyanin extract (CAE), which was characterised for the total anthocyanin content. Characterisation of the films revealed that the incorporation of Corozo-derived phenolic compounds did not cause significant (p < 0.05) changes in structural or water interaction properties compared to those of the control sample.

Tannic acid-grafted Polylactic acid films: A nonmigrating antibacterial packaging for chilled fresh meat

Antimicrobial packaging can prolong the shelf life of fresh food, but those active antimicrobial substances may leach into the food and affect its quality. To avoid this phenome, the CC double bond was first incorporated into the chemical structure of polylactic acid (PLLA) and tannic acid (TA) to prepare poly(L-LA-co-butyrate itaconate) (PLBI) and photoactive tannic acid (pTA). Then pTA-grafted PLBI (pTA-g-PLBI) films were fabricated using UV curing technology. Results showed that pTA was successfully grafted onto the surface of PLBI film and formed a uniform layer. The pTA-g-PLBI films exhibited good bacteriostatic effects of 86 %, 90 %, and 96 % on E. coli, P. fluorescens, and S. aureus, respectively. Additionally, pTA-g-PLBI packaging reduced the relative abundance of Shewanella, Psychrobacter, and Pseudomonas in chilled pork and delayed the deterioration of pork for more than 5 days.

Poly(vinyl alcohol)/tannic acid nanofibrous membrane containing curcumin as an intelligent indicator of food spoilage

In recent years, active packaging technology for extending food shelf life and intelligent packaging technology for monitoring food freshness have become essential for ensuring food safety. Among sensing technologies, pH-sensitive sensors have notable advantages, including simplicity, compactness, and affordability, making them ideal for monitoring food freshness. This study proposes an intelligent food indicator based on a composite nanofiber membrane fabricated by electrospinning. The membrane, composed of poly(vinyl alcohol) (PVA), tannic acid (TA), and the natural pH-sensitive dye curcumin (CUR), was heat-treated to enhance its moisture stability for food packaging. Furthermore, the incorporation of TA and CUR into PVA provides additional benefits such as UV-blocking, antioxidant, and antimicrobial properties, effectively delaying food spoilage. The CUR-incorporated nanofibrous membrane exhibited faster detection of shrimp spoilage via colorimetric changes under increasingly alkaline conditions than film samples. Moreover, compared to film-based samples, the composite nanofiber membrane exhibited faster color change responsiveness owing to its porous and high surface area structure, thus serving as an efficient and intelligent indicator.

Fabrication of versatile and durable superhydrophobic cotton fabrics using PTA-Ala adhesive

In recent years, the preparation of functional textiles based on polyphenols adhesion has received extensive attention and research. However, polyphenols are prone to peroxidation during oxidative polymerization, which can compromise the interfacial adhesion of their monomers. Reintroducing reactive functional groups after oxidative polymerization of polyphenols may potentially compensate for the lost interfacial adhesion while increasing cohesion. In this paper, L-alanine (Ala) is introduced into poly (tannic acid) (PTA) solution to generate the PTA-Ala via Michael addition and Schiff base reaction. Original cotton fabrics are modified with PTA-Ala solution to enhance adhesion strength between the fabrics and subsequent functional modifiers. A silver nanowire network is then incorporated to increase the surface roughness through tannic acid reduction. Finally, polydimethylsiloxane is applied to reduce fabric surface energy, resulting in superhydrophobic multifunctional OH-PDMS/Ag/PTA-Ala/cotton fabrics. The finished cotton fabric exhibits a water contact angle of 166.7 ± 1.9° and a rolling angle of 5 ± 0.5°. Moreover, the fabric features diverse functionalities such as oil-water separation, photothermal conversion, antimicrobial properties, water collection, and anti-icing capabilities, alongside excellent durability and self-healing properties that extend its service life. This finished cotton fabric demonstrates promising applications in oil pollution control, outdoor clothing and medical protection, highlighting its broad across various industries.

Hierarchically Nano-Decorated Poly(lactic acid) Nanofibers for Humidity-Resistant Respiratory Healthcare and High-Accuracy Disease Diagnosis

The application of biodegradable and eco-friendly poly(lactic acid) (PLA) nanofibrous membranes (NFMs) toward respiratory healthcare has long been thwarted by the poor electroactivity and low surface activity of PLA. Herein, we unravel a microwave-assisted route to fabricate rod-like ZnO nanodielectrics, which were decorated with dopamine (ZnO@PDA) and anchored at the PLA nanofibers via an electrospinning-electrospray approach. The PLA/ZnO@PDA NFMs featured a substantially elevated specific surface area (up to 20.7 m2/g), increased dielectric constant (nearly 1.8) and a surface potential as high as 9.5 kV, resulting in superior air filtering performance (99.45% for PM0.3, 94.1 Pa, 32 L/min) compared with the pure PLA counterpart (90.04%, 169.0 Pa, 32 L/min). The notably increased electroactivity endowed the PLA/ZnO@PDA NFMs with significant improvements in triboelectric properties (output voltage of 11.5 V at 10 N, 0.5 Hz), laying down the cornerstone for self-powered monitoring of personal respiration. More importantly, a deep learning-assisted diagnostic system was developed based on respiration-driven signal patterns, enabling intelligent and real-time disease diagnosis with 100% accuracy for the protective membranes. The proposed hierarchical nanodecoration strategy opens up new possibilities for engendering eco-friendly nanofibers with an exceptional combination of efficient respiratory healthcare and intelligent diagnosis.

Development of a multifunctional active food packaging membrane based on electrospun polyvinyl alcohol/chitosan for preservation of fruits

To mitigate environmental impacts in food preservation, the development of a multifunctional membrane for packaging is of importance. In this study, we have successfully fabricated a nanofibrous membrane using an eco-friendly electrospinning technique, comprising polyvinyl alcohol (PVA), chitosan (CS), and tannic acid (TA). The resulting nanofibrous membranes were crosslinked with glutaraldehyde (GA) and surface modified with ZnO. Our findings demonstrate that the crosslinking process enhances water resistance, reduces water vapor permeability, improves tensile strength (from 3 to 18 MPa), and enhances thermal stability (increasing decomposition temperature from 225 °C to 310 °C). Furthermore, the incorporation of TA and ZnO provides antioxidant properties to the membrane, effectively preventing food decomposition caused by UV-induced oxidation. Additionally, CS, TA, and ZnO synergistically exhibit a remarkable antibacterial effect with a bacteriostasis rate exceeding 99.9 %. The strawberry fresh-keeping experiment further confirms that our developed membrane significantly extends shelf life by up to 6 days. Moreover, cytotoxicity assays confirm the non-toxic nature of these membranes. The innovative significance of this study lies in proposing a robust GA-PVA/CS/TA@ZnO nanofibrous membrane with excellent mechanical properties, biocompatibility, and multiple functionalities including antibacterial, anti-ultraviolet, and anti-oxidation capabilities. It has tremendous potential for applications in active food packaging materials.

Recent Advances in Poly(vinyl alcohol)-Based Hydrogels

Poly(vinyl alcohol) (PVA) is a versatile synthetic polymer, used for the design of hydrogels, porous membranes and films. Its solubility in water, film- and hydrogel-forming capabilities, non-toxicity, crystallinity and excellent mechanical properties, chemical inertness and stability towards biological fluids, superior oxygen and gas barrier properties, good printability and availability (relatively low production cost) are the main aspects that make PVA suitable for a variety of applications, from biomedical and pharmaceutical uses to sensing devices, packaging materials or wastewater treatment. However, pure PVA materials present low stability in water, limited flexibility and poor biocompatibility and biodegradability, which restrict its use alone in various applications. PVA mixed with other synthetic polymers or biomolecules (polysaccharides, proteins, peptides, amino acids etc.), as well as with inorganic/organic compounds, generates a wide variety of materials in which PVA's shortcomings are considerably improved, and new functionalities are obtained. Also, PVA's chemical transformation brings new features and opens the door for new and unexpected uses. The present review is focused on recent advances in PVA-based hydrogels.

Development of Versatile, thermally stable, flexible, UV-resistant and antibacterial polyvinyl alcohol-Nanodiamonds composite for efficient food packaging

This research paper reports an enhancement of thermal, optical, mechanical and antibacterial activities of the Polyvinyl alcohol-Nanodiamonds (PVA-NDs) composite required for the food packaging industry. The synthesis of composites was done by the wet processing method. The large surface area of NDs facilitated the robust interaction between the hydroxyl group and macromolecular chains of PVA to enhance the hydrogen bonding of PVA with NDs rather than PVA molecules. Thus, a reduction in PVA diffraction peak intensity was reported. NDs improved the thermal stability by preventing the out-diffusion of volatile decomposition products of PVA. The results also revealed an enhancement in tensile strength (∼60 MPa) and ductility (∼180 %). PVA-NDs composite efficiently blocked the UVC (100 %), most of the part of the UVB (∼85 % above 300 nm), and UVA (∼58 %). Furthermore, enhanced antibacterial activities were reported for PVA-NDs composite against E. coli and S. aureus. NDs accumulated around the bacterial cells prevented essential cellular functions and led to death. Hence, this composite could be a promising candidate for safe, thermally stable, strong, flexible, transparent, UV- resistant antibacterial food packaging material.

Cellulose-based biomass composite films for plastic replacement: Synergistic UV shielding, antibacterial and antioxidant properties

With the gradual increase in environmental awareness and the growing demand for food safety, sustainable and environmentally friendly cellulose-based materials have become a promising alternative to petroleum-based plastics. However, in practice, packaging materials prepared from cellulose-based materials still have some unsatisfactory properties, such as monofunctionality, low transparency, and lack of UV shielding, antibacterial or antioxidant properties. Herein, a novel synthetic strategy is proposed in this paper, specifically, tannic acid (TA), a green natural extract with antibacterial and antioxidant properties, is used as a plasticizer and cross-linker, and oxidized cellulose nanocellulose (TOCN) modified with folic acid (FA) grafting is blended with TA, and cellulose-based biomass thin films with ultraviolet (UV) shielding, antibacterial, and antioxidant properties have been successfully prepared by using a simple vacuum-assisted filtration. The experimental results showed that the films could completely block ultraviolet light at wavelengths of 200-400 nm while providing 81.47 % transparency in the visible spectrum, while the introduction of TA conferred excellent antibacterial and antioxidant capabilities with antioxidant activity of up to 95 %, and also resulted in films with excellent mechanical properties. Therefore, this work provides ideas for the design and manufacture of competitive biomass green packaging materials, laying the foundation for future applications in food packaging.

Improving astaxanthin-loaded chitosan/polyvinyl alcohol/graphene oxide nanofiber membranes and their application in periodontitis

Periodontitis is a chronic inflammatory disease primarily driven by host inflammation and plaque-induced immune responses. Controlling the host inflammatory response and improving the periodontal inflammatory microenvironment are crucial to promoting periodontal tissue regeneration. In this study, the blended nanofiber membranes previously prepared by our research group were improved, and we developed multifunctional chitosan/polyvinyl alcohol/graphene oxide/astaxanthin coaxial nanofiber membranes. Scanning electron microscopy showed that the prepared nanofibers had a smooth surface and a uniform diameter distribution. The mechanical property test results showed that the coaxial nanofiber membranes exhibited higher tensile strength compared to the blended nanofiber membranes, which increased from 4.50 ± 0.32 and 3.70 ± 0.45 MPa to 7.12 ± 0.22 and 5.62 ± 0.79 MPa respectively. Drug release studies indicated that the "shell-core" structure of coaxial nanofibers significantly reduced the initial burst release of astaxanthin (ASTA), with only 13.49 % and 10.71 % release in the first 24 h, and drug release lasted for over a week. Animal experiments confirmed that the coaxial nanofiber membranes loaded with ASTA promoted periodontal bone defect repair while inhibiting periodontal inflammation. In conclusion, the prepared coaxial nanofiber membranes are a promising sustained-release drug system for treating periodontitis.

PVA-Based Electrospun Materials-A Promising Route to Designing Nanofiber Mats with Desired Morphological Shape-A Review

Poly(vinyl alcohol) is one of the most attractive polymers with a wide range of uses because of its water solubility, biocompatibility, low toxicity, good mechanical properties, and relatively low cost. This review article focuses on recent advances in poly(vinyl alcohol) electrospinning and summarizes parameters of the process (voltage, distance, flow rate, and collector), solution (molecular weight and concentration), and ambient (humidity and temperature) in order to comprehend the influence on the structural, mechanical, and chemical properties of poly(vinyl alcohol)-based electrospun matrices. The importance of poly(vinyl alcohol) electrospinning in biomedical applications is emphasized by exploring a literature review on biomedical applications including wound dressings, drug delivery, tissue engineering, and biosensors. The study also highlights a new promising area of particles formation through the electrospraying of poly(vinyl alcohol). The limitations and advantages of working with different poly(vinyl alcohol) matrices are reviewed, and some recommendations for the future are made to advance this field of study.

Tannin-Assisted Synthesis of Nanocomposites Loaded with Silver Nanoparticles and Their Multifunctional Applications

Nanocomposites have been widely used in many important areas due to their particular physical/chemical properties; however, just though a simple technology, endowing multiple functions into a single nanomaterial for realizing their multifunctional applications is still a challenge. Here, we report a robust method for the facile synthesis of Ag-based multifunctional nanocomposites via using tannin-coated phenol-formaldehyde resin nanospheres (TA-PFRN) as silver nanoparticle (Ag NP) carriers. The thickness of the tannin coating is readily tuned from 50 to 320 nm by regulating the concentration of tannin added. Under the optimal conditions, the TA-PFRN has a 23.8 wt % of Ag NPs loading capacity with only 17.2 nm Ag NP layers. Consequently, the novel TA-PFRN@Ag nanocomposites possess multiple functions and integrated characteristics. As catalysts, the catalytic efficiency of TA-PFRN@Ag is nearly 6 times higher than that of the PFRN@Ag. As highly effective free radical initiators, TA-PFRN@Ag nanocomposites can trigger ultrafast acrylic acid (AA)/acrylamide (AM) polymerization at room temperature (in only a few minutes). As nano-reinforced fillers, the addition of 0.04 wt % nanocomposites can improve the tensile strength of PVA film from 60 to 153.2 MPa. In addition, the nanocomposites can also serve as antibacterial agents, efficiently inhibiting the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus); as antiultraviolet agents, the presence of TA-PFRN@Ag nanocomposites endows the film/hydrogel materials excellent ultraviolet (UV) shielding. This work provides a novel strategy for the green synthesis of Ag-based multifunctional nanocomposites that show promising applications in catalysis, nanomaterials, and biomedicine.

Dual-Mechanism Tuned Engineered Polyphenols with Cascade Photocatalytic Self-Fenton Reaction for Sustainable Biocidal Coatings

Traditional disposable personal protective equipment (PPE) only blocks pathogenic bacteria by mechanical filtration, with the risk of recontamination and transmission remaining. Herein, inspired by phenolic-enabled nanotechnology (PEN), we proposed engineered polyphenol coatings by plant-derived aromatic aldehydes and metal involvement, denoted as FQM, to obtain the desired photocatalysis-self-Fenton antibacterial performance. Experiments and theoretical analysis proved the dual mechanism of Fe-induced enhancement: (1) tuning of molecular structure realized improved optical properties; (2) Fe(III)/Fe(II) triggered photocatalytic cascade self-Fenton reaction. Mechanism study reveals FQM killing bacteria by direct-contact ROS attack and gene regulation. Further, the FQM was developed as the ideal antibacterial coating on different fabrics (cloth cotton, polyester, and N95 mask), killing more than 93% of bacteria after 5 cycles of use. Such photocatalysis-self-Fenton coatings based on engineered polyphenols endowed with desirable safety, sustainability, and efficient antibacterial features are promising solutions to meet the challenges of the currently available PPE.