# Electrospinning of Chitosan for Antibacterial Applications--Current Trends
## 7 Application Fields of Electrospun Chitosan Nanofibers and Chitosan Derivatives
### Water Filtration
#### 7.1.3 Enhancing the Antibacterial Performance with Bactericidal Agents  
Due to their distinctive polycationic character, chitosan and chitosan derivatives have been suggested for applications in food, gastronomy, agriculture, pharmaceutical products, biomedicine, and biotechnology [165; 166]. The antibacterial activities of chitosan are restricted due to the amino groups on the chitosan backbone, which serve as relatively weak positive charge centers. One possibility of increasing the antibacterial activity of chitosan is to add positively charged groups [167]. The large number of hydroxyl and amino groups in chitosan allows it to form metal complexes depending on the type of metal ion, molar ratio, molecular weight, and degree of deacetylation of the chitosan [168]. Various kinds of metal ions and chitosan complexes have recently been developed to enhance the antibacterial action [169]. Silver is the most prominent representative of antibacterial additives. In comparison to unmodified chitosan, the inclusion of a modest proportion of 2.15 w% of silver nanoparticles was adequate to substantially improve _E. coli_ inactivation [170]. Another research team found that the Ag-chitosan nanocomposite exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria [171]. Chitosan can additionally stabilize silver nanoparticles and prevents them from sticking together below a threshold concentration. Chitosan leads to a positive charge on the surfaces of nanoparticles, which helps them attach to the negative charged cell wall [172]. [PERSON] et al. studied the influence of silver doping of chitosan nanofibers on the antibacterial activity. For this, chitosan was dissolved in acetic acid (1 g/20 mL), followed by stirring for 24 h at room temperature, then stirring for 3 h at 80 \({}^{\circ}\)C until a homogeneous solution was reached. Afterward, 3 g of the chitosan solution was mixed with 14 mL of polyvinyl alcohol (PVA) solubilized in distilled water. Five different silver concentrations, varying from 1% to 5%, were added stepwise and stirred with a magnetic stirrer. For each Ag concentration, Ag-doped chitosan nanofibers were electrospun at a collector distance of 8 cm, with 25 kV of applied voltage and a constant feeding rate of 0.1 mL/h. _S. aureus_ bacteria were used to investigate their antibacterial properties. The results of the experiments showed that the antibacterial performance was enhanced as the Ag concentration rose [173]. Another group observed an intense disruption of the _S. aureus_ cell wall incubated with chitosan-silver nanocomposites, resulting in a change in its morphology, and concluded that chitosan and silver nanoparticles work synergistically, displaying greater potency than either component interacting on its own. Furthermore, the chitosan-Ag nanocomposites' minimum inhibitory and bactericidal concentrations were reported to be lower than those of pure Ag nanoparticles (AgNPs) [174]. [PERSON] et al. prepared chitosan/PVA membranes with AgNPs on the fiber surface by adding AgNO\({}_{3}\) to the electrospinninging solution. Electrospun fibers were collected on a polyester substrate, resulting in improved mechanical properties that are needed for water filtration. Different contents of AgNO\({}_{3}\) were tested in static and dynamic antibacterial filtration assessments against _E. coli._ Nanofibers from chitosan/PVA with 2 wt% AgNO\({}_{3}\) aimed to kill all bacteria within 60 min exposure time. Doubling the AgNO\({}_{3}\) concentration in the electrospinninging solution from 2 to 4 wt% halved the elimination times for all bacteria. In the release experiments, differences were detected between the static and dynamic filtration assessments. Within 24 h, about 15% of the total Ag content was released in the static experiment and about 10% in the dynamic experiment. The findings showed that antibacterial water filtration and disinfection may be accomplished with the use of chitosan/PVA electrospun nanofibrous membranes containing AgNPs.