PVC containing silver nanoparticles with antimicrobial properties effective against SARS-CoV-2.

Poly (vinyl chloride) (PVC) is commonly used to manufacture biomedical devices and hospital components, but it does not present antimicrobial activity enough to prevent biofouling. With the emergence of new microorganisms and viruses, such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that was responsible for the global pandemic caused by Coronavirus Disease 2019 (COVID-19), it is evident the importance of the development of self-disinfectant PVC for hospital environments and medical clinics where infected people remain for a long time. In this contribution, PVC nanocomposites with silver nanoparticles (AgNPs) were prepared in the molten state. AgNPs are well-known as antimicrobial agents suitable for designing antimicrobial polymer nanocomposites. Adding 0.1 to 0.5 wt% AgNPs significantly reduced Young's modulus and ultimate tensile strength of PVC due to the emergence of microstructural defects in the PVC/AgNP nanocomposites, but the impact strength did not change significantly. Furthermore, nanocomposites have a higher yellowness index (YI) and lower optical bandgap values than PVC. The PVC/AgNP nanocomposites present virucidal activity against SARS-CoV-2 (B.1.1.28 strain) within 48 h when the AgNP content is at least 0.3 wt%, suitable for manufacturing furniture and hospital equipment with self-disinfectant capacity to avoid secondary routes of COVID-19 contagion.

Characterisation of a new exopolysaccharide obtained from of fermented kefir grains in soymilk.

Microbial exopolysaccharides (EPSs) have been widely studied in recent decades due to similarity to gums used in the food industry. Exopolysaccharides can be used in food processing as a thickener and/or stabiliser. This study aimed to investigate the physicochemical properties, thermal behaviour and structural composition of the lyophilised EPS obtained from the fermentation of kefir grains in soymilk. The EPS in concentration 18 mg/mL exhibited water activity of 0.204 and pH=6.20 at 25°C, reducing sugars content of 22.10% (v/v) and protein content of 2% (v/v). The thermogravimetric curve obtained was similar to those reported in the literature for other EPSs. The degradation temperature was 351.84°C and showed that the EPS in this study had a high thermal stability. Characteristic polysaccharide bands were observed in the infrared spectrum. The analysis by liquid chromatography coupled to electrospray ionisation mass spectrometry (LC-ESI-MS) showed that the EPS is only composed of glucose.