Antibiotic resistance is one of the major problems in healthcare and is the cause of persistent infections associated with biofilm formation at infection sites related to medical devices (catheters, joint prostheses, and prosthetic heart valves). The need for more effective antibiotics is growing daily.
The aim of the study is to develop new antimicrobial materials that can prove to be effective means in the fight against bacterial infections and contribute to improving the quality and safety of human life.
Chitosan is a special type of biopolymer, and the presence of primary amines in its main structure gives it advantageous physicochemical characteristics and unique interactions with proteins, cells, and other biologically active substances. The most important properties for biomedical applications are its non-toxicity, antibacterial activity, and biodegradability.
Recently, electrospinning has become one of the most popular methods for producing nanofibers from various synthetic and natural polymers. This method allows for the creation of materials with fiber diameters of less than 100 nm, which mimic the natural extracellular matrix and can promote cell adhesion and tissue regeneration. It has also been proven that fibrous structures made from chitosan demonstrate greater effectiveness than films, sponges, or gels.
New chitosan membranes, made using two TFA/DCM ratios (7:3 and 9:1), were produced by traditional electrospinning followed by treatment with aqueous 1 M NaOH, aqueous 1 M Na_2 CO_3, NaOH-ethanol, or Na_2 CO_3-ethanol. Besides structural stability, NaOH-ethanol neutralization preserved the membrane structure after a degradation experiment in PBS over one month. All membrane variants (post-production and post-neutralization) supported cell attachment and proliferation over a 6-day period, but ethanol treatment of chitosan membranes made with 9:1 TFA/DCM resulted in reduced cell growth. Chitosan membranes made with 7:3 TFA/DCM demonstrated biocompatibility along with moderate and more effective antibacterial properties against S. aureus and E. coli.
Adding PEG to the chitosan/polylactic acid (Ch/PLA) solution increases the hydrophilicity of the resulting materials. The produced materials, consisting of Ch, modified PLA, and PEG as a co-solvent, along with post-treatment (alkaline neutralization) to enhance water resistance, exhibit slower degradation rates (stable moderate weight loss over 16 weeks) and reduced hydrophobicity (lower contact angle reaching 21.95 ± 2.17°), making them promising for biomedical applications. The antibacterial activity of the membranes was evaluated against Staphylococcus aureus and Escherichia coli, with PEG-containing samples showing twice the levels of bacterial growth inhibition. In vitro cell culture studies demonstrated that PEG-containing materials promote uniform cell attachment and proliferation.
Enhanced antimicrobial properties can be achieved by incorporating biocidal agents, such as metal nanoparticles, into the biopolymer. However, electrospun nanofibers loaded with metal nanoparticles, such as AgNPs, may have a cytotoxic effect on mammalian cells. On the other hand, successful management of the solution composition and controlled structure of nanofibrous membranes, in addition to an appropriate post-treatment procedure, is essential considering the importance of the initial interaction between bacterial cells and nanofibers.
This study highlights the significant potential of electrospun chitosan membranes as effective antimicrobial coatings for biomedical applications, and the integration of silver nanoparticles into these membranes further enhances and balances their dose-dependent antibacterial efficacy, starting from 25–50 µg/mL against S. aureus and E. coli. The anti-adhesive activity of the membranes against these bacterial strains further emphasizes their effectiveness in combating microbial infections and preventing bacterial biofilm formation through the modification of nanofibrous materials with AgNPs.
The in vivo experiment on laboratory rats demonstrated the superiority of Ch/PLA membranes loaded with silver nanoparticles in terms of antimicrobial action on wound infection, promoting more effective wound cleansing and healing compared to unmodified samples.
Ch/PLA membranes modified with AgNPs showed a moderately pronounced inflammatory process with necrotic tissues and granulation tissue on day 3. By day 10, mature granulation tissue formation with minimal inflammatory infiltration was observed, and by day 21, the tissues were characterized by fibrotic changes with a slight inflammatory response, indicating effective wound healing.
A comprehensive evaluation of these new materials, which demonstrate improved physical, chemical, and biological properties in vitro and in vivo, underscores their potential for biomedical applications in tissue engineering and regenerative medicine.
