Dominik Fajstavr

Due to its nanostructure, bacterial nanocellulose (BC) has several advantages over plant cellulose, but it exhibits weak cell adhesion. To overcome this drawback, we studied the drying method of BC and subsequent argon plasma modification (PM). BC hydrogels were prepared using the Komagataeibacter sucrofermentans (ATCC 700178) bacteria strain. The hydrogels were transformed into solid samples via air-drying (BC-AD) or lyophilization (BC-L). The sample surfaces were then modified by argon plasma. SEM revealed that compared to BC-AD, the BC-L samples maintained their nanostructure and had higher porosity. After PM, the contact angle decreased while the porosity increased. XPS showed that the O/C ratio was higher after PM. The cell culture experiments revealed that the initial adhesion of human keratinocytes (HaCaT) was supported better on BC-L, while the subsequent growth of these cells and final cell population density were higher on BC-AD. The PM improved the final colonization of both BC-L and BC-AD with HaCaT, leading to formation of continuous cell layers. Our work indicates that the surface modification of BC renders this material highly promising for skin tissue engineering and wound healing.

Silver nanoparticles (AgNPs) possess strong antibacterial effect. The current trend is to incorporate AgNPs into functional materials that benefit from their bactericidal capabilities. Hydroxypropyl methylcellulose (HPMC) is routinely used for the controlled release of medicine thanks to its slow dissolution in water and could be used as a matrix for the controlled release of AgNPs, if a method to produce such a material without the need of other reactants was developed. We proposed such a method in a photochemical reduction of AgNO₃ in hydroxypropyl methylcellulose (HPMC) solutions by the illumination of the mixture with the light emitting diode bulb for about 2 h. These AgNPs were characterized by transmission electron microscopy and their diameter was found to be mostly under 100 nm. The colloids were then easily transformed into solid samples by drying, lyophilization and spin-coating. The slowly soluble HPMC was found to be able to release the AgNPs gradually over the duration of several hours. Antibacterial activity of the prepared colloids and the solid samples was tested against Escherichia coli and Staphylococcus epidermidis and was found to be very high, reaching the total elimination of the bacteria in the studied systems.