Development of porous biodegradable structures for biomedical applications

V sklopu magistrske naloge smo pripravili in analizirali dve vrsti poroznih biorazgradljivih materialov namenjenih za biomedicinske aplikacije. Sintetizirali smo hidrogel na osnovi alginata in guar gumija, kateremu smo dodali aktivno učinkovino kloksacilin, ki smo jo v material inkorporirali v obliki mikrosfer in z neposrednim dispergiranjem v zmes hidrogela. Vzorce smo analizirali s FTIR spektroskopijo in proučili karakteristike nabrekanja pri različnih pH vrednostih ter primerjali nabrekanje osnovnega hidrogela in hidrogela z mikrosferami. Pri tem smo ugotovili, da je razmerje nabrekanja osnovnega hidrogela višje od razmerja nabrekanja hidrogela z mikrosferami. S pomočjo merjenja kontaktnega kota s programom ImageJ, smo materialom določili hidrofilen značaj. Proučili smo tudi morfologijo vzorcev z uporabo okoljske vrstične elektronske mikroskopije (ESEM) analize in določili stopnjo poroznosti, katera je bila v primeru hidrogela z mikrosferami, višja v primerjavi z osnovnim hidrogelom. Antimikrobni učinek učinkovine kloksacilina v hidrogelu smo proučili na bakterijah E. coli in S. aureus. Tako v primeru hidrogela z dispergiranim antibiotikom, kot v primeru hidrogela z mikrosferami, smo opazili cono inhibicije rasti obeh testnih mikroorganizmov, s čemer smo dokazali antimikrobno učinkovitost hidrogelov. Posebej smo se posvetili analizi sproščanja aktivne učinkovine iz hidrogelov, kinetiko sproščanja pa smo primerjali s Korsmeyer-Peppasovim matematičnim modelom in na podlagi izračunanih kinetičnih parametrov ugotovili, da kloksacilin difundira iz hidrogelov po principu ne-Fickove oz. anomalne difuzije. Druga vrsta materiala za biomedicinske aplikacije so trdna celična ogrodja, ki smo jih sintetizirali na osnovi polikaprolaktona, celuloze in hidroksiapatita na različne načine. V sintetizirane materiale smo vključili še 1 ut. % aktivne učinkovine kloksacilin. Ogrodja smo izdelali z uporabo tehnike penjenja plina v superkritičnem CO2. Vzorce smo analizirali s pomočjo FTIR spektroskopije in jim določili hidrofoben značaj s pomočjo izrisa kontaktnega kota z uporabo programa ImageJ. Primerjali smo talilne temperature, talilne entalpije in kristaliničnost za vse 4 različne načine sinteze ogrodij s pomočjo DSC analize. Tako kot v primeru hidrogelov, smo tudi trdnim celičnim ogrodjem določili stopnjo poroznosti ter analizirali njihovo morfologijo z uporabo ESEM. Ugotovili smo, da ima najvišjo stopnjo poroznosti ogrodje, ki ga sestavlja 70 ut. % PCL in 30 ut. % celuloze. Glede na štiri razvite vrste ogrodij smo določili odstotek sproščanja aktivne učinkovine, pri čemer se je v primeru dveh ogrodij v 14 dneh sprostilo 100 % aktivne učinkovine, v primeru drugih dveh pa manj kot 50 %. Vsako izmed metod sinteze smo nato primerjali z matematičnim modelom ničelnega reda, prvega reda in Higuchijevim modelom ter določili največje ujemanje z enim izmed njih in s tem kinetiko sproščanja kloksacilina iz ogrodij.As part of the master\u27s thesis, two types of porous biodegradable materials intended for biomedical applications have been prepared and analyzed. An alginate and guar gum-based hydrogel was synthesized. The active ingredient cloxacillin was incorporated into the material in the form of microspheres and by direct dispersion into the hydrogel mixture. The samples were analyzed by FTIR spectroscopy and the swelling characteristics at different pH values were studied. A comparison in swelling between basic hydrogel and the hydrogel with microspheres has been investigated. We found that the swelling ratio of the basic hydrogel is higher than the swelling ratio of the hydrogel with the microspheres. By measuring the contact angle with the ImageJ program, we determined the hydrophilic character of the material. Information about the morphology of the samples has been gathered using environmental scanning electron microscopy (ESEM) analysis. The degree of porosity has been determined, which was higher in the case of the hydrogel with microspheres compared to the base hydrogel. The antimicrobial effect of cloxacillin in the hydrogel was studied on E. coli and S. aureus. Both in the case of the hydrogel with the dispersed antibiotic and in the case of the hydrogel with the microspheres, a growth inhibition zone of both test microorganisms was observed, thus demonstrating the antimicrobial efficacy of the hydrogels. Special attention was dedicated to the analysis of the controlled release of the active ingredient from hydrogels. The controlled release kinetics were compared to the Korsmeyer-Peppas mathematical model and based on the calculated kinetic parameters found that cloxacillin diffuses from hydrogels on the principle of non-Fick or. anomalous diffusion. Another type of material for biomedical applications that has been investigated are scaffolds based on polycaprolactone, cellulose, and hydroxyapatite in various combinations. 1 wt. % of cloxacillin was incorporated in the synthesized materials. The scaffolds were prepared using the gas-foaming technique in supercritical CO2. Samples were analyzed by FTIR spectroscopy. Their hydrophobic character was determined by drawing the contact angle using the ImageJ program. Melting temperatures, melting enthalpies and degree of crystallinity were compared for all 4 different scaffold synthesis methods using DSC analysis. As in the case of hydrogels, we determined the degree of porosity of solid cell scaffolds and analyzed their morphology using ESEM. We found that the highest degree of porosity has a scaffold consisting of 70 wt. % polycaprolactone and 30 wt. % cellulose. Based on the four developed types of scaffolds, we determined the percentage of active substance release, whereby in the case of two scaffolds 100 % of the active substance was released in 14 days, and in the case of the other two less than 50 %. Results have been compared to the mathematical models of zero and first order and the Higuchi model. A good match with one of the models has been discovered and thus the kinetics of cloxacillin release from scaffolds were determined