The Promise of PVA/GO–AgNPs Nanocomposites: A New Frontier in Antimicrobial MaterialsIf you are interested in products related to the research phase in this field, please contact for further inquiries.
Poly(vinyl alcohol) (PVA) is a biocompatible and biodegradable polymer known for its mechanical strength and water solubility. However, its lack of antimicrobial properties limits its applications in environments where bacterial growth is a concern. The incorporation of graphene oxide (GO) and silver nanoparticles (AgNPs) into PVA creates a nanocomposite with enhanced antimicrobial activity. This material, known as PVA/GO–AgNPs, combines the benefits of PVA with the antibacterial properties of GO and AgNPs, making it a promising candidate for various applications, particularly in the biomedical and environmental sectors.
Fig 1. Tensile properties of neat PVA, and PVA/GO-AgNPs nanocomposites. (a) Young´s modulus; (b) tensile strength; (c) elongation at break. (Cobos M., et al., 2020) 
The synthesis of PVA/GO–AgNPs nanocomposites involves a multi-step process. Initially, GO is synthesized from graphite flakes using a modified Hummers method. This method oxidizes graphite to produce GO, which has a high surface area and functional groups that facilitate the attachment of AgNPs. The AgNPs are then synthesized by reducing silver nitrate (AgNO3) with ascorbic acid, which acts as a green reducing agent. This process ensures that AgNPs are uniformly distributed on the GO surface, creating a stable hybrid material.
The PVA/GO–AgNPs nanocomposites are prepared by mixing the GO–AgNPs hybrid with an aqueous solution of PVA. The mixture is then cast into films and dried. The resulting nanocomposites exhibit an exfoliated structure, where GO sheets are well-dispersed within the PVA matrix. This structural arrangement enhances the mechanical and thermal properties of the composite while preserving its antimicrobial activity.
The incorporation of GO–AgNPs into PVA significantly improves the thermal stability of the composite. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveal that the glass transition temperature (Tg) and crystallization temperature (Tc) of the polymer matrix increase with the addition of GO–AgNPs. The thermal decomposition of PVA occurs in two stages, with the first stage corresponding to the dehydration and chain scission of the polymer backbone. The presence of GO–AgNPs delays and shifts the decomposition peaks to higher temperatures, indicating enhanced thermal stability.
Mechanically, the PVA/GO–AgNPs nanocomposites exhibit superior strength compared to neat PVA. Tensile tests show that the elastic modulus and tensile strength at break increase with the addition of GO–AgNPs. For instance, a 5 wt% GO–AgNPs composite demonstrates an 80% increase in tensile strength. This improvement is attributed to the excellent mechanical properties of GO and the reinforcement effect of AgNPs. However, the elongation at break decreases, resulting in a more brittle material. This brittleness is due to the constrained polymer chain mobility caused by the strong interfacial interactions between the hybrid and the PVA matrix.
PVA is inherently hydrophilic, leading to high water absorption, which can be detrimental in applications requiring water resistance. The incorporation of GO–AgNPs hybrid significantly reduces the water absorption of PVA films. The interactions between PVA and GO–AgNPs through hydrogen bonds create a constrained polymer region that prevents water from penetrating the composite. This enhanced water resistance makes PVA/GO–AgNPs nanocomposites suitable for applications in moist environments, such as wound dressings and medical devices.
The antimicrobial properties of PVA/GO–AgNPs nanocomposites are one of their most notable features. The antibacterial effect is dependent on the content of GO–AgNPs hybrid and the duration of exposure. Studies have shown that composite films with higher GO–AgNPs content exhibit stronger antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria.
The antibacterial mechanism involves both the direct contact of bacteria with the composite films and the release of silver ions (Ag+) from the oxidized surface of AgNPs. The sharp edges of GO sheets can damage bacterial cell membranes, while AgNPs can penetrate the cell membrane and disrupt vital cell functions. Additionally, the leaching of Ag+ ions from the composite films contributes to the antimicrobial effect by interacting with thiol-containing proteins in the bacterial cell wall.
It is important to note that S. aureus is more susceptible to PVA/GO–AgNPs films than E. coli. This difference can be attributed to the structural differences in their cell walls. S. aureus has a thick cell wall with many peptidoglycan layers, while E. coli has a thinner cell wall with an outer membrane composed of lipopolysaccharides (LPS), which acts as a protective barrier. The antibacterial effect is more pronounced when bacteria are in direct contact with the composite films, indicating that both the physical presence of the nanoparticles and the release of Ag+ ions contribute to the antimicrobial efficacy.
The enhanced mechanical properties, thermal stability, and antimicrobial activity of PVA/GO–AgNPs nanocomposites make them promising candidates for various biomedical applications. One potential application is in wound dressings, where the antimicrobial properties of the composite can prevent infection while promoting wound healing. The high water resistance of the composite ensures that the dressing remains effective in moist conditions.
Another potential application is in the development of antimicrobial coatings for medical devices. These coatings can reduce the risk of biofilm formation and associated infections, which are a common problem in hospitals and healthcare settings. The use of PVA/GO–AgNPs nanocomposites in these applications can help combat the rising issue of antibiotic-resistant bacteria, offering a new strategy for infection control.
Beyond biomedical applications, PVA/GO–AgNPs nanocomposites can also be explored for environmental applications. Their photocatalytic properties, which are enhanced by the synergistic effect between GO and AgNPs, can be utilized for the degradation of pollutants and organic dyes in water treatment processes. This dual functionality of the composite offers a comprehensive approach to environmental remediation.
The development of PVA/GO–AgNPs nanocomposites represents a significant advancement in the field of antimicrobial materials. By combining the biocompatibility and mechanical properties of PVA with the antibacterial capabilities of GO and AgNPs, these composites offer a multifunctional solution for various applications. The enhanced thermal stability, mechanical strength, and water resistance of PVA/GO–AgNPs nanocomposites make them suitable for biomedical and environmental applications. Ongoing research and development in this area hold the promise of overcoming current challenges and unlocking the full potential of these innovative materials.
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Reference
This article is for research use only and cannot be used for any clinical purposes.
