Abstract
A previously developed fiber-based polyester (PES) stent, with mechanical properties comparable to commercial nitinol stents, was coated with metallic silver (Ag0) and silver oxides (AgxO) thin films through direct current (DC) magnetron sputtering. Ag0 and AgxO coatings provide antimicrobial properties to the stents to minimize the occurrence of coronary stent infections. Nevertheless, the stent interacts with the atmosphere and then with the biological fluids and may lead to the generation of silver species with diminished antimicrobial efficiency and/or prone to induce cytotoxicity. Therefore, stent coating nanostructures aged 3 months were thoroughly analyzed by X-ray photoelectron spectroscopy (XPS) and their antimicrobial and cytotoxicity properties were assessed. Aging led to the presence of silver carbonate and bicarbonate as well as chemisorbed oxygen species in Ag0 and AgxO coatings. Bactericidal efficacy was tested against an important nosocomial bacterium, particularly associated to indwelling devices: Staphylococcus epidermidis. Aged Ag0 and AgxO coating presented a Log reduction of 1 and 2 at their surface; respectively. However, aged stents were able to induce a Log reduction of 2 (Ag0) and 4 (AgxO) on the surrounding medium. Only aged AgxO stent was able to provide a mild reduction of the bacterium at its surface and a clear antimicrobial effect (Log reduction >3) within its vicinity. More importantly, both aged Ag0 and AgxO stents were shown to be compatible with fibroblasts cells indicating that they can be safely used as indwelling devices, despite the aging effect.
Highlights
Cardiovascular diseases (CVD) represent nearly half of mortality in Europe, resulting each year in a loss of over €200 billion [1]
An aging period is to provide an insight on their performance in terms of surface properties, mechanical behavior, paramount to provide an insight on their performance in terms of surface properties, mechanical antimicrobial activity and biocompatibility
X-ray photoelectron spectroscopy (XPS) showed that both aged Ag0 and Agx O stent surfaces behavior, antimicrobial activity and biocompatibility
Summary
Cardiovascular diseases (CVD) represent nearly half of mortality in Europe, resulting each year in a loss of over €200 billion [1]. Different coatings have been applied in commercially available coronary stents to enhance their properties, drug-eluting stents which include in their formulation: vasodilators, anticoagulants, healing promoters, anti-proliferatives, immunosuppressants, and antimicrobials [4]. The application of a potent antimicrobial material, which is not susceptible to induce resistance, at the stent surface can be a viable strategy to prophylactically act against infection, in pathogenic-prone environments such as hospitals [16]. This strategy has been successfully applied in ureteral stents, which are highly susceptible to microbial colonization [17,18]. This work envisages the thorough assessment of the chemical modifications that stent coatings of metallic silver (Ag0 ) and silver oxides (Agx O) undergo during aging, and the implications for their antimicrobial activity and cytotoxicity
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