Environmentally friendly and advanced functionalization of silicone for the development of new medical devices

Prekomerna uporaba antibiotikov za zdravljenje infekcij vodi v naraščanje števila odpornih bakterij, kar predstavlja grožnjo javnemu zdravju. Strategije zmanjševanja uporabe temeljijo tudi na preprečevanju nastanka bakterijskega biofilma na površinah medicinskih pripomočkov. Predstavljamo metodo funkcionalizacije silikona z oplaščenjem z naravnimi bioaktivnimi substancami. Na silikon smo kot vezni polimer adsorbirali biopolimer polidopamin, na katerega smo kovalentno vezali karbokismetil hitozan s tiolnimi funkcionalnimi skupinami, ki izkazuje protimikrobne in biofilm-inhibitorne lastnosti. Rezultati karakterizacije so pokazali uspešno kovalentno vezavo karboksimetil hitozana preko tiolnih skupin na polidopamin, kar je pripomoglo k zmanjšanju tvorbe biofilma na površini v primerjavi s fizikalno vezanim karboksimetil hitozanom in neobdelanim silikonom.Excessive use of antibiotics to treat infections leads to an increase in the number of resistant bacteria, which poses a threat to public health. Strategies to reduce the use of antibiotics are also based on preventing the formation of bacterial biofilm on the surfaces of medical devices. In this work, we present a method of functionalizing silicone by coating it with natural bioactive substances. The biopolymer polydopamine was adsorbed on the silicon as a binding polymer, to which carboxymethyl chitosan was covalently bound with thiol functional groups exhibiting antimicrobial and biofilm-inhibitory properties. The characterization results showed successful covalent binding of carboxymethyl chitosan via thiol groups to polydopamine, which helped to reduce surface biofilm formation compared to physically bound carboxymethyl chitosan and untreated silicone

Characterization of polyester fibers degradation products after chemical recycling

Poliester v kategoriji polimernih materialov zaradi široke uporabnosti zavzema visok delež v svetovni proizvodnji tekstila in plastičnih mas, ki neprestano narašča. Z ekonomskega in okoljevarstvenega vidika je zato potrebno recikliranje. Tekom diplomskega dela smo poliestrna vlakna reciklirali po postopku nevtralne hidrolize v visokotemperaturnem in visokotlačnem reaktorju. Produkte hidrolize smo nato okarakterizirali z metodo infrardeče spektroskopije s Fourierjevo transformacijo in z metodo potenciometričnih titracij v nevodnem mediju z uporabo treh različnih topil (dimetil sulfoksida, kombinacija topil toluena in etanola ter benzil alkohola) z namenom določitve končnih karboksilnih skupin. Na podlagi dobljenih rezultatov smo lahko sklepali o učinkovitosti depolimerizacije pri različnih reakcijskih pogojih. Ugotovili smo, da se poliestrna vlakna najbolje razgradijo pri reakcijskih pogojih 250 °C, masno razmerje vlakna : voda 1:10 in 30 min reakcijskega časa po doseženi željeni temperaturi in tlaku. Dimetil sulfoksid se je izkazal za najustreznejše topilo za določitev končnih karboksilnih skupin s potenciometrično titracijo produktov v obliki prahu, benzil alkohol pa za produkte v obliki vlaken.Polyester in category of polymer materials holds a major share in global production of textiles and plastics that is growing constantly. From economic and environmental aspect, recycling is essential for this matter. During diploma work, polyester fibres were recycled by using neutral hydrolysis process in high-temperature and high-pressure reactor. Products of hydrolysis were characterised using Fourier transform infrared (FTIR) spectroscopy and potentiometric titrations in non-aqueous solutions. Three different solvents were used: dimethyl sulfoxide (DMSO), combination of toluene and ethanol, and benzyl alcohol, with the aim to determinate number of available carboxyl end-groups. Based on the results, conclusions were made on the depolymerisation efficiency under different reaction conditions. We established that the most successful fibre degradation rate was by reaction conditions of 250°C, mass ratio of fibre and water 1:10 and 30 minute reaction time after reaching desired temperature and pressure conditions. Dimethyl sulfoxide (DMSO) turned out to be the most suitable solvent for determination of available carboxyl end-groups by potentiometric titrations of powder-form products and benzyl alcohol for titrations of fibre-form products

A method for the immobilization of chitosan onto urinary catheters

A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds

Incorporation of metal-based nanoadditives into the PLA matrix

In this work, the modification process of poly(lactic acid) (PLA) with metal-based nanoparticle (NPs) additives (Ag, ZnO, TiO$_2$) at different loading (0.5, 1.0, and 2.5 wt%) and by melt-mix extrusion method followed by film formation as one of the advantageous techniques for industrial application have been investigated. PLA nanoparticle composite films (PLA-NPs) of PLA-Ag, PLA-ZnO, PLA-TiO$_2$ were fabricated, allowing convenient dispersion of NPs within the PLA matrix to further pursue the challenge of investigating the surface properties of PLA-NPs reinforced plastics (as films) for the final functional properties, such as antimicrobial activity and surface mechanical properties. The main objective was to clarify how the addition of NPs to the PLA during the melt extrusion process affects the chemistry, morphology, and wettability of the surface and its further influence on the antibacterial efficiency and mechanical properties of the PLA-NPs. Therefore, the effect of Ag, ZnO, and TiO$_2$ NPs incorporation on the morphology (SEM), elemental mapping analysis (SEM-EDX), roughness, surface free energy (SFE) of PLA-NPs measured by goniometry and calculated by OWRK (Owens, Wendt, Rabel, and Kaelble) model was evaluated and correlated with the final functional properties such as antimicrobial activity and surface mechanical properties. The developed PLA-metal-based nanocomposites, with improved mechanical and antimicrobial surface properties, could be used as sustainable and biodegradable materials, offering desirable multifunctionalities not only for food packaging but also for cosmetics and hygiene products, as well as for broader plastic products where antimicrobial activity is desirable