**1. Introduction**

Electrospinning is a simple and versatile technique, used to fabricate continuous fibers from a large number of polymers, with diameters ranging from micrometers to several nanometers [1–3]. The resulting fibrous mats are characterized by large e ffective surface areas, continuously interconnected pores, high surface roughness, and usually high porosity [4,5]. It is a highly versatile technique, allowing for the development of structures with various morphologies, including core–shell, hollow, and yarn, only by varying the parameters of the electrospinning, i.e., voltage, feed rate, collector type, distance, and nozzle design [6,7].

Polyethylene terephthalate (PET) is a class of engineered polyesters broadly used in numerous industries owing to its mechanical and thermal properties. PET materials are used in a wide range of applications, such as the automotive industry, filtering membranes, biosensors, protective clothing [8–11], surgical meshes, drug delivery systems, and tissue engineering sca ffolds (i.e., vascular grafts and ligament and tendon substitutes) [11–16].

Most of the annual world's consumption of PET estimated at 13 million tons comes from the packaging industry, raising grea<sup>t</sup> concern for environmental pollution [17], with an increasing scientific focus on developing reuse and recycling technologies of PET materials. In this regard, electrospinning is an interesting approach for the fabrication of non-woven nanofiber mats that could reduce environmental waste materials by producing recycled PET materials that could replace previously used materials [18,19]. Moreover, PET electrospun nanofibers could be further implemented in water filtration [20] and heavy-metal adsorption [21] applications. This approach has the potential to significantly decrease the amount of PET waste, by reusing this material in other non-packaging applications.

As reports show that 10% of patients entering an acute hospital develop a healthcare-associated infection, with 9% of cases being surgical wound infections, the risk of wound infections is causing grea<sup>t</sup> concern to healthcare professionals [22]. In this context, electrospun nanomaterials are widely investigated for their antimicrobial properties. The common strategy for developing such materials is represented by the attachment or encapsulation of antimicrobial agents, such as antibiotics, cyclodextrins, and metal or metal-oxide nanoparticles onto or into the supporting nanofibers [23]. Silver is the preferred metal oxide used as an antimicrobial agen<sup>t</sup> [24–30]. Moreover, its nanosized form shows enhanced beneficial properties, owing to the small size, large specific surface area, and quantum effect [31], properties which are correlated with its low toxicity [27,32,33], allowing for the development of diverse applications focused on preventing microbial contamination in di fferent environments or treating microbial infections [34]. There are several studies reporting the uniform incorporation of silver nanoparticles into the electrospun fibers for enhanced antimicrobial abilities [35].

The aim of this study was to obtain electrospun nanostructured fibrillary antimicrobial membranes based on PET materials and silver nanoparticles for di fferent antimicrobial applications. Specifically, the silver nanoparticles were applied onto the surface of the PET materials in order to enrich it with large-spectrum biocidal properties. The di fferent fibers were obtained by adjusting the flow rate of the electrospinning process, since this parameter is very important in ensuring fiber strength and it may impact the morphology and fiber size [36,37]. The in vitro and in vivo biocompatibility issues of PET containing silver nanoparticles were evaluated in order to establish their suitability for biomedical applications. Our goal was to develop a PET-based material that could be further implemented in wound dressing and biomedical coating areas (i.e., implants, medical surfaces, medical textiles), while simultaneously reducing the environmental waste produced by PET usage.
