The skin is the first contact with the outer world, thus it is constantly exposed to the risk of injuries and wounds. The unsuccessful wound healing, lasting for more than 8 weeks, is characteristic of chronic wounds. The structure of nanofibers mimics the morphological properties of extracellular matrix, which plays a crucial role in wound healing process. Therefore, nanofibers represent modern dressing for wound healing application. The dressings should be sterile and thus meet the criteria for adequate microbiological quality of pharmaceutical products, which represents a big challenge during their preparation.
The aim of the master thesis was to evaluate microbiological quality of nanofibers produced by electrospinning. Nanofibers were produced from polyvinyl alcohol and polyethylene oxide and characterized by scanning electron microscopy. We have optimizied our working protocol using different sterilization methods (dry heat, steam and ultraviolet sterilization) and aseptic procedure with the aim to produce sterile nanofibers. Microbiological quality of nanofibers was evaluated according to the tests specified in European Pharmacopoeia 9.0. Polyvinyl alcohol and polyethylene oxide nanofibers, both with avarage diameter of approximately 200 nm, were successfully developed. The steam sterilization of polymer solutions significantly influenced the average diameter of nanofibers from polyvinyl alcohol or polyethylene oxide, whereas the high temperatures during dry heat sterilization did not affect the morphology of polyvinyl alcohol nanofibers. The sterility test performed on polyvinyl alcohol nanofibers sterilized by dry heat confirmed their sterility. We have also performed the numeric test for nonsterile products. Petri dishes with polyethylene oxide nanofibers prepared from sterilized polymer solution did not show growth of any colonies after the incubation period, while samples with polyvinyl alcohol nanofibers prepared from sterilized polymer solution showed growth of 1 (50 CFU/g of the product) and 2 colonies (100 CFU/g of the product), thus the nanofibers meet the criteria of microbiological quality of nonsterile pharmaceutical products for dermal use (the upper limit being 100 CFU/g of the product). We have managed to produce sterile nanofibers using two different approaches. Polyvinyl alcohol nanofibers were prepared and then sterilized by dry heat, while sterile polyethylene oxide nanofibers were produced by the aseptic procedure. These nanofibers represent an immense potential as modern dressings for wound healing application, due to their composition, morphology and also adequate microbiological quality.
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