In situ green synthesis of red wine silver nanoparticles for the production of antimicrobial cotton fabrics and the investigation of their biomedical effects
| dc.contributor.author | Erasmus Alexandria | |
| dc.date.accessioned | 2025-09-12T10:30:05Z | |
| dc.date.available | 2025-09-12T10:30:05Z | |
| dc.date.issued | 2024 | |
| dc.description.abstract | Microbial infections, particularly those caused by pathogenic bacteria, pose a significant barrier in the treatment of infectious diseases. In addition, overuse of antibiotics has resulted in the development of antimicrobial resistance (AMR). AMR is a growing global health concern that can cause serious complications in common infections and chronic wounds infected with AMR microbes. Conventional therapeutic approaches previously used in these conditions (wounds and microbial infections) become ineffective and their life cycle are prolonged. Hence, it is crucial to create innovative and alternative antimicrobial treatment strategies. The field of biomedicine can benefit from the application of nanotechnology to produce alternative or enhanced pharmaceutical products and therapies. Silver nanoparticles (AgNPs) have demonstrated strong antimicrobial properties and have shown to be beneficial in treating AMR infections. Their added benefit in chronic wounds is their ability to promote the wound healing process by stimulating angiogenesis, cell proliferation, and collagen synthesis, among others. These properties are enhanced in AgNPs synthesized by using medicinal plant extracts. Although green synthesis using this route is rapid, easy and cheap; it can often be limited by low solubility and aggregation after purification. In situ synthesis of nanoparticles offers advantages like enhanced stability, better uniformity, reduced contamination, cost-effectiveness, and tailored functionality, especially when nanoparticles need to be directly integrated into a matrix. This synthesis approach has a wide range of applications, including textiles and wound healing dressings. Cotton has been utilised in medical applications since the Middle Ages, primarily as a material for dressing wounds, whereas red wine is recognised for its elevated levels of resveratrol – a phenolic chemical molecule that possesses strong antioxidant and anti-inflammatory qualities. This study reports on the green synthesis of AgNPs using freeze-dried red wine extract (RW) (RW-AgNPs), the fabrication of RW-AgNP-loaded cotton fabrics (RW-ALC), and the investigation of their antimicrobial, antioxidant, and cytotoxic properties. RW-AgNPs were green-synthesized by optimizing pH, silver nitrate (AgNO3) concentration, and RW extract concentration under hydrothermal conditions and characterized using several physicochemical techniques including Ultraviolet-visible (UV-vis) Spectroscopy, Dynamic Light Scattering (DLS) using a Zetasizer, High-Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) Spectroscopy. The RW-ALC were synthesized in situ under hydrothermal conditions for one hour using RW extract at a concentration of 6.25 mg/ml and pH 10, and AgNO3 at a concentration of 3 mM. Assessment of antioxidant activity of the RW and RW-AgNPs was conducted using the ABTS and DPPH scavenging assays. Varying quantities of RW, RW-AgNPs, and the positive control ascorbic acid (ranging from 0.78 to 100 μg/ml) were used in the assays. The antibacterial activity of the RW-ALC and RW-AgNPs was evaluated using the agar disc diffusion and broth microdilution assays against the human pathogens S. aureus, MRSA, E. coli, E. cloacae, K. pneumoniae, P. aeruginosa, and A. baumannii. In the disc diffusion assay, RW-ALC samples synthesized with varying concentrations of RW (ranging from 1.56 to 25 mg/ml) were employed as the treatment. A standard cotton piece served as the negative control. The positive control was prepared by applying 50 μl of a 15 μg/ml Ciprofloxacin solution to a clean cotton piece, except for the E. coli samples, where a 10 μg/ml Ciprofloxacin concentration was used instead. The Müeller-Hinton agar (MHA) plates were incubated at 37 °C for 24 hours. The effect of pretreatment with 2-mercaptoethanol on the antibacterial efficacy of the RW-ALC was also investigated. For the microdilution assay, bacterial cultures were subjected to treatment for 24 hours using RW-AgNPs at serially diluted concentrations of 25, 12.5, 6.25, 3.125, 1.56, 0.78, 0.39, and 0.195 μg/ml. The negative control consisted of 50 μl of Mueller-Hinton broth (MHB) added to the well. For the positive control, 50 μl of a solution containing 10 μg/ml of Ciprofloxacin was introduced into each well, with the exception of E. coli, for which a concentration of 5 μg/ml of Ciprofloxacin was used. Cytotoxic properties of the RW-AgNPs on five cancerous (MCF-7 Caco-2, PC-3, Panc-1, MIA-Paca-2) and one non-cancerous (KMST-6) human cell lines was assessed using the WST-1 cell viability assay. Cell lines were treated for 24 hours with RW and RW-AgNPs at concentrations ranging from 0 – 100 μg/ml. 5 % DMSO was utilised as a positive control. The RW-AgNPs were spherical with a core size of 8.7 ± 1.3 nm, hydrodynamic size of 104.30 ± 5.51 nm, PDI value of 0.344 ± 0.2 and ζ-potential of -21.3 ± 6.16 mV. RW-AgNPs exhibited minimum inhibitory concentrations and minimum bactericidal concentrations against S. aureus (0.195 μg/ml and 0.78 μg/ml), MRSA (1.56 μg/ml and 3.125 μg/ml), K. pneumoniae (0.78 μg/ml and 1.56 μg/ml), A. baumannii (0.78 μg/ml and 1.56 μg/ml), E. cloacae (3.125 μg/ml for both), E. coli (0.78 μg/ml for both), and P. aeruginosa (3.125 μg/ml and 6.25 μg/ml). Characterisation of the cotton showed polydispersed RW-AgNPs on the surface at a concentration of 80.2 μg/ml. The results of the DPPH antioxidant assay demonstrate that the scavenging activity of RW-AgNPs is dose-dependent within the concentration range of 3.125 – 100 μg/ml. No significant activity was observed at concentrations between 0.78 and 1.56 μg/ml. While RW-AgNPs exhibited considerable antioxidant activity, their efficacy was lower compared to that of RW and ascorbic acid. Conversely, in the ABTS assay, RW, RW-AgNPs, and ascorbic acid (used as a positive control) showed a dose-dependent reduction of the ABTS•+ radical. Notably, within the concentration range of 0.78 to 50 μg/ml, RW-AgNPs exhibited superior scavenging activity compared to the positive control. RW-ALC exhibited significant antibacterial activity, with zones of inhibition ranging from 12.33 ± 1.15 mm to 23.5 ± 5.15 mm in comparison to 10 μg/ml Ciprofloxacin (between 10 ± 3 mm – 19.17 ± 1.39 mm). Preincubation with 2-mercaptoethanol abrogated the antibacterial activity of RW-ALC, indicating that the antibacterial properties are attributed to silver's ability to bind to sulfhydryl groups. Furthermore, RW-AgNPs showed significant cytotoxicity towards the cancer cell lines: MCF-7; PC-3; Caco-2; MIA-Paca-2; Panc-1 cells with half maximal inhibitory concentration (IC50) values of 11.47 μg/ml, 10.98 μg/ml, 6.76 μg/ml, 7.89 μg/ml, and 3.76 μg/ml, respectively. Reduced cytotoxicity was observed against the normal human fibroblast KMST-6 cell line (IC50 of 27.7 μg/ml), suggesting that the RW-AgNPs can be effectively employed in the treatment of bacterial infections and cancer with minimal detrimental effects to healthy mammalian cells. This study demonstrated that RWcan be used to synthesize AgNPs and AgNP-loaded textiles in situ under hydrothermal conditions. Furthermore, when evaluating the biological effects of the resultant RW-AgNPs and RW-ALC in vitro, both had potent antibacterial and anticancer effects. The RW-ALC could be useful in treating infectious diseases, including bacteria infected chronic wounds. However, cytotoxic effects of these RW-AgNPs require further investigation to ensure their biocompatibility at concentrations that are minimally detrimental to mammalian cells yet still toxic to bacteria and cancer cells. Further studies are underway to elucidate the anticancer mechanisms of the RW-AgNPs. These could then be transformed into novel affordable remedies for chronic non-healing wounds and cancer. | |
| dc.identifier.uri | https://hdl.handle.net/10566/20906 | |
| dc.language.iso | en | |
| dc.publisher | University of the Western Cape | |
| dc.subject | Antimicrobial activity | |
| dc.subject | Antimicrobial resistance | |
| dc.subject | ESKAPE | |
| dc.subject | Nanotechnology | |
| dc.subject | Silver nanoparticles (AgNPs) | |
| dc.title | In situ green synthesis of red wine silver nanoparticles for the production of antimicrobial cotton fabrics and the investigation of their biomedical effects | |
| dc.type | Thesis |