A Facile Green Fabrication and Characterization of Cellulose-Silver Nanoparticle Composite Sheets for an Antimicrobial Food Packaging

Bacterial cellulose-based Pickering emulsions reinforced with silver and silica nanoparticles for advanced antibacterial and hydrophobic food packaging solutions

Conventional packaging materials typically exhibit insufficient barrier performance and limited antimicrobial efficacy, constraining their utility in food preservation. Enhancing attributes such as moisture resistance, antimicrobial potency, and stability in biodegradable matrices has presented a longstanding challenge. Herein, we report the design of an ODSA-based Pickering emulsion coating of bacterial cellulose, further modified with AgNPs and SiO2 (TAS), engineered to elevate food preservation standards within packaging applications. TAS demonstrates pronounced hydrophobicity, achieving a stable contact angle of 110°, thus offering robust water repellency-a crucial quality in moisture-resistant coatings. Moreover, the emulsion displays significant antibacterial activity, producing inhibition zones against E. coli and S. aureus, attributable to the bactericidal action of AgNPs. The TAS coating notably mitigates weight loss in fruits; strawberries treated with TAS retained over 98 % of their initial weight after seven days, compared to a 6 % weight reduction in untreated counterparts. The ODSA-TAS emulsion serves as an effective UV and IR barrier, markedly diminishing transmittance at 365 nm and 700 nm, thereby protecting produce from oxidative degradation. These results underscore the multifunctional capabilities of ODSA-TAS, affirming its potential as a sustainable solution to extend food shelf life.

Sustainable approach for fabrication of pineapple agro-waste mediated cellulose nanocrystals embedded with Ag/Ag2O/ZnO nanocomposites for efficient removal of waterborne pathogens in wastewater

Biogenic nanocomposites (NCs) effectively purify contaminated water by eliminating pollutants caused by rapid urbanization, unrestrained industrial activities, and the proliferation of pathogenic organisms, addressing the critical water contamination crisis impacting global health. This study describes the synthesis of a sustainable biopolymer NC (BNC) by incorporating pineapple (Murusi variety) crop residue-based Ag/Ag2O/ZnO NCs and cellulose nanocrystals (CNCs) through an eco-friendly and sustainable approach. TEM analysis revealed cross-sectional diameters of 11 nm consisting of spherical-shaped Ag/Ag2O NPs (9 nm) arranged on nanoflower-shaped ZnO NPs (82 nm). XRD analysis confirmed that biogenic Ag, Ag2O, and ZnO NPs exhibit space groups Fm3m, Pn-3m, and P63mc respectively with Ag/Ag2O NPs forming face-centered cubic and ZnO NPs wurtzite crystal structures. FTIR validated the pure CNCs formation, while TGA and differential thermogravimetry (DTG) demonstrated high thermal stability at 370 °C. Ag/Ag2O NPs exhibited outstanding antibacterial activity at 2000 ppm, with inhibition zones of 20 mm against E. coli and 21 mm against S. aureus. In contrast, ZnO NPs demonstrated lower antibacterial activity with inhibition zones of 13 mm against E. coli and 14 mm against S. aureus. The Ag/Ag₂O/ZnO NCs displayed significant antibacterial activity against both strains with inhibition zones of 19 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the NCs were determined to be 31.3 ppm and 62.5 ppm, respectively, for both bacterial strains. These findings highlight the superior antimicrobial properties of silver-based NCs compared to ZnO, suggesting their potential application in antimicrobial treatments. The developed BNC filter comprising of Ag/Ag2O/ZnO NCs 20 mg: CNCs: 50 g effectively removed Salmonella typhi from 1.2 L of contaminated wastewater through sequential filtration, exhibiting significant characteristics including sustainability, low production cost, water stability, easy recoverability, and high bacterial growth inhibition, making it a promising solution for water treatment applications.

Construction of efficient ethylene removal and antibacterial cellulose paper-based packaging materials for avocado preservation

Fruits are susceptible to ethylene ripening and microbial infestation, which can lead to spoilage and further significant economic losses. Thus, using functional preservation materials is an effective controlling technology to improve the post-harvest quality and extend the shelf life of fruits. Hence, a dual-function cellulose-based paper with exceptional antibacterial efficiency, favourable ethylene removal performance, improved mechanical and hydrophobic properties was prepared by covalently grafted antibacterial guanidine salt and surface-modified ethylene scavenger. When the amount of guanidine salt grafted and ethylene scavenger is 1.85 wt% and 1.5 g·m-2, respectively, the prepared cellulose paper exhibited about 99 % ethylene conversion and killing efficiency with no leaching, which extending the post-harvest avocado preservation time to 20 days at room temperature. Packaging with the preservation paper effectively reduced hardness and consumption of soluble solids in avocado during storage, maintaining their appearance and nutritional quality. These findings highlight the excellent preservation capabilities of the dual-function paper, making it a promising material for fruit and vegetable preservation in small and medium planting areas and households.

Evolution and recent development of cellulose-modified, nucleic acid-based and green nanosensors for trace heavy metal ion analyses in complex media: A review

With increased manufacturing activities and energy sector development, monitoring of heavy metal ion (HMI) pollution is becoming increasingly pressing. The discharge of metals from industrial effluents into the waterways could cause major economic and environmental disruption. In situ and on-site detection methods of trace HMIs can be effective countermeasures before the toxicity spreads out to larger areas, affecting the ecosystem. Conventional methods are often lacking in portability and costly. In contrast, electrochemical sensing, especially with nanoplatforms, is promising for trace detection of HMIs in complex media because of the ease of fabrication and adaptability of incorporating green technology. Appropriate electrode selection with suitable modifiers is crucial in complex medium analyses to overcome electrode fouling. In this review, the evolution from metal-based and carbon-based electrodes to advancements in electrode modification involving agro/biocomposite nanomaterials (NMs) such as cellulose, chitosan, and hydroxyapatite is discussed. The fabrication of nucleic acid-based aptasensors for analyzing HMIs and the adoption of smart systems based on microfluidics with high selectivity, operational stability, and sensitivity are highlighted. The challenges and future prospects for trace HMI determination based on electrochemical sensors in real complex media, including blood and industrial effluent or wastewater, are critically examined.

Dialdehyde cellulose nanofibrils/polyquaternium stabilized ultra-fine silver nanoparticles for synergistic antibacterial therapy

Dialdehyde cellulose nanofibrils (DACNF) and Polyquaternium-10 (PQ: chloro-2-hydroxy-3-(trimethylamino) propyl polyethylene glycol cellulose) have become increasingly favored as antibacterial substances due to their advantageous characteristics. DACNF exhibits exceptional mechanical properties and biocompatibility, whereas PQ demonstrates a positive charge that enhances its antibacterial activity. Combined in a DACNF/PQ mixture, they provide an excellent template material for preparing and stabilizing ultra-fine (~ 10.3 nm) silver nanoparticles (AgNPs) at room temperature. Here, the dialdehyde group of DACNF functions as a reducing agent, while the quaternary ammonium of PQ and carboxylate groups of DACNF synergistically helped in-situ generation of AgNPs uniformly. The synthesized nanocomposites, namely PQ@AgNPs, AgNPs@DACNF, and AgNPs@DACNF/PQ, were subjected to comprehensive characterization using various advanced analytical techniques. The films containing AgNPs@DACNF and AgNPs@DACNF/PQ, fabricated via vacuum filtration, exhibited excellent mechanical properties of 9.78 ± 0.21 MPa, and demonstrated superior antibacterial activity against both Escherichia coli and Staphylococcus aureus. Additionally, the silver ion leaching from the prepared composite films was well controlled. The fabricated nanocomposites also effectively inhibited bacterial biofilm formation. It was also found to be highly biocompatible and non-toxic to human skin fibroblast cells. Furthermore, the nanocomposites exhibited enhanced migration of human dermal fibroblasts, suggesting their potential in facilitating wound healing processes.

Progress in food packaging applications of biopolymer-nanometal composites - A comprehensive review

Eco-friendly nanotechnology-enabled biopolymers are one of the novel concepts of packaging materials to substitute traditional synthetic polymers and their composites. This article succinctly reviews the recent developments of introducing additional functionalities to biopolymers using metal and metal oxide nanoparticles. The functionality of metal nanoparticles such as silver, zinc oxide, titanium dioxide, copper oxide, gold, and magnesium oxide, as food packaging materials were discussed. The addition of nanoparticles in biopolymers improves mechanical properties, gas barrier properties, durability, temperature stability, moisture stability, antimicrobial activity, antioxidant property, and UV absorbance and can prevent the presence of ethylene and oxygen, hence extending the shelf life of foodstuffs. Other than this, the functional activity of these biopolymer composite films helps them to act like smart or intelligent packaging. The selection of metal nanoparticles, particle migration, toxicological effect, and potential future scope in the food packaging industry are also reviewed.

Silver-nanoparticle-modified nanocellulose synthesized by pyroligneous acid: cytotoxicity towards HaCat cells

In the present study, pyroligneous acid, also known as wood vinegar, has been employed as reducing and stabilizing agent in the synthesis of silver nanoparticles (AgNPs) anchored on nanocellulose (NC). The idea is to confer the latter bactericidal properties for its typical uses such as in cosmetics and food-packing. It has been demonstrated that AgNPs can be directly produced onto NC in one-pot fashion while dramatically enhancing the kinetics of AgNPs synthesis (2 h for reaction completion) in comparison to the NC-less counterpart (10 days for reaction completion). Furthermore, NC allowed for a narrower size distribution of AgNPs. NC-supported and non-supported AgNPs had sizes of 5.1 ± 1.6 nm and 16.7 ± 4.62 nm, respectively. Immortalized human keratinocytes (HaCat) cells were then employed as model to evaluate the cytotoxicity of the AgNPs-NC compound. The latter was found not to impact cell proliferation at any formulation, while decreasing the viability by only 6.8% after 72 h. This study contributes to the development of more environmentally benign routes to produce nanomaterials and to the understanding of their impact on cells.

Paper-based material with hydrophobic and antimicrobial properties: Advanced packaging materials for food applications

The environmental challenges posed by plastic pollution have prompted the exploration of eco-friendly alternatives to disposable plastic packaging and utensils. Paper-based materials, derived from renewable resources such as wood pulp, non-wood pulp (bamboo pulp, straw pulp, reed pulp, etc.), and recycled paper fibers, are distinguished by their recyclability and biodegradability, making them promising substitutes in the field of plastic food packaging. Despite their merits, challenges like porosity, hydrophilicity, limited barrier properties, and a lack of functionality have restricted their packaging potential. To address these constraints, researchers have introduced antimicrobial agents, hydrophobic substances, and other functional components to improve both physical and functional properties. This enhancement has resulted in notable improvements in food preservation outcomes in real-world scenarios. This paper offers a comprehensive review of recent progress in hydrophobic antimicrobial paper-based materials. In addition to outlining the characteristics and functions of commonly used antimicrobial substances in food packaging, it consolidates the current research landscape and preparation techniques for hydrophobic paper. Furthermore, the paper explores the practical applications of hydrophobic antimicrobial paper-based materials in agricultural produce, meat, and seafood, as well as ready-to-eat food packaging. Finally, challenges in production, application, and recycling processes are outlined to ensure safety and efficacy, and prospects for the future development of antimicrobial hydrophobic paper-based materials are discussed. Overall, the emergence of hydrophobic antimicrobial paper-based materials stands out as a robust alternative to plastic food packaging, offering a compelling solution with superior food preservation capabilities. In the future, paper-based materials with antimicrobial and hydrophobic functionalities are expected to further enhance food safety as promising packaging materials.

Antibacterial, antibiofilm and larvicidal activity of silver nanoparticles synthesized from spider silk protein

Green synthesis of silver nanoparticles has gained attention due to its simple process of synthesis and varied applications. Scientists have tried its synthesis from a wide range of materials, but there is lack of reports that can use the metabolites of insects. Here in this study, we have used the spider silk protein which is considered as complete waste collected from household and field sources and processed to synthesize silver nanoparticles which were subsequently analyzed using different analytical tools like SEM, TEM, FTIR, and XRD. The spider silk protein-mediated synthesized nanoparticle (SP-AgNPs) showed a sharp peak at 420 nm when analyzed spectrophotometrically giving an indication of successful synthesis of AgNP. The synthesized nanoparticle ranges from 10 to 40 nm and were of varied shapes. The synthesized SP-AgNPs showed remarkable antibacterial activity. The MIC values against B. subtilis and E. coli were recorded 45 and 40 μg/mL respectively. Further to know the mechanisms of antibacterial activity protein leakage and conductivity measurement were conducted. The synthesized nanoparticle also showed excellent antibiofilm activity with inhibition percentages of 74 % and 68 % for E. coli and B. subtilis respectively at MIC concentration of the treatment. Finally, the synthesized nanoparticles was applied as mosquito larvicidal agent against Culex sp. and the difference between LC50 and LD90 value was recorded as statistically significant (p < 0.0267) during 24 h of incubation. Therefore, it can be said that spider-web could be an excellent biological reducing and capping agent for heavy metal nanoparticle synthesis that can minimize the ailments caused by mosquitoes and pathogenic microorganisms.