20.500.12556/RUL-182941 Vpliv dvovalentnih in trovalentnih kationov na mehanske lastnosti in sproščanje glukoze iz alginatnih hidrogelov Influence of divalent and trivalent cations on the mechanical properties and glucose release from alginate hydrogels Hidrogeli so tridimenzionalna zamrežena mreža hidrofilnih polimerov. Lahko absorbirajo veliko količino vode ali bioloških tekočin, kar povzroči njihovo nabrekanje, pri čemer ohranjajo svojo 3D strukturo brez raztapljanja. Postopek ionskega zamreženja alginata s kationi vključuje tvorbo struktur »jajčne škatle«, kjer kationi koordinirajo med sosednjimi verigami alginata. Vrsta in valenca kationov pomembno vplivata na lastnosti alginatnih hidrogelov. Dvovalentni kationi (Ca$^{2+}$, Ba$^{2+}$, Sr$^{2+}$) in trivovalentni kationi (Fe$^{3+}$) učinkovito zamrežijo alginatne verige s koordinacijo s karboksilnimi in hidroksilnimi skupinami. Sproščanje učinkovine iz hidrogelov poteka preko difuzije, ki je odvisna od strukture in lastnosti materiala. Ključni dejavniki pri sproščanju so velikost por, interakcije med učinkovino in polimerno mrežo ter stopnja zamreženja. V magistrski nalogi sem pripravil 2 ut. % alginatne hidrogele z uporabo kationov Ca$^{2+}$, Sr$^{2+}$, Ba$^{2+}$, Cu$^{2+}$ in Fe$^{3+}$ v koncentraciji 0,25 %. Preučeval sem njihove kombinacije v razmerjih 25/75, 50/50 in 75/25. Cilj raziskave je bil preučiti vpliv teh kationov na mehanske lastnosti hidrogelov ter vpliv na hitrost sproščanja glukoze. Najprej sem vzorcem z reometrom določil mehanske lastnosti. Na podlagi meritev sem z uporabo posplošenega Maxwellovega modela izračunal strižni modul, ki je nadaljnje služil za določitev gostote zamreženja. Z uporabo Peppas-Merril enačbe sem nadaljnje iz gostote zamreženja ocenil povprečno velikost por v hidrogelni mreži in pripadajoče difuzijske koeficiente glukoze v vodnem mediju. Poleg mehanskih lastnosti sem izvajal tudi teste sproščanja glukoze v vodnem okolju. Vzorcem sem izmeril koncentracijo sproščene glukoze v prvih 60 minutah v 10-minutnih intervalih, nato pa v naslednji uri v 30-minutnih intervalih. Za merjenje koncentracije sem uporabil UV-Vis spektroskopijo in jim izračunal difuzijske koeficiente. Rezultate sem primerjal z vrednostmi izračunanih iz reoloških meritev. Zaključki raziskave so pokazali, da kombinacije ionskih zamreževalcev ne delujejo po načelu linearnega povprečenja, temveč povzročajo izrazite sinergijske ali antagonistične učinke, ki se odražajo tako v mehanskih lastnostih kot v difuzijskih procesih. Mešanice ionov lahko tako mehansko utrdijo ali zrahljajo polimerno mrežo, posledično pa povečajo ali zmanjšajo difuzijo glukoze. Rezultati potrjujejo, da je s kombiniranjem ionskih zamreževalcev mogoče natančno regulirati togost, gostoto zamreženja, velikost por in s tem hitrost sproščanja učinkovin. Hydrogels are three-dimensional crosslinked networks of hydrophilic polymers. They can absorb large amounts of water or biological fluids, which causes them to swell while maintaining their 3D structure without dissolving. The ionic crosslinking of alginate with cations involves the formation of “egg-box” structures, where cations coordinate between adjacent alginate chains. The type and valence of the cations strongly influence the properties of alginate hydrogels. Divalent cations (Ca$^{2+}$, Ba$^{2+}$, Sr$^{2+}$) and trivalent cations (Fe$^{3+}$) effectively crosslink alginate chains through coordination with carboxyl and hydroxyl groups. The release of an active compound from hydrogels occurs via diffusion, which depends on the structure and material properties. The key factors influencing release include pore size, interactions between the active substance and the polymer network, and the degree of crosslinking. In my master’s thesis, I prepared 2% wt. alginate hydrogels using Ca$^{2+}$, Sr$^{2+}$, Ba$^{2+}$, Cu$^{2+}$ and Fe$^{3+}$ ions at a concentration of 0.25%. I investigated their combinations in ratios of 25/75, 50/50 and 75/25. The aim of the study was to examine the influence of these cations on the mechanical properties of the hydrogels and on the release rate of glucose. First, I determined the mechanical properties of the samples using a rheometer. Based on these measurements, I used the generalized Maxwell model to calculate the shear modulus, which was then used to determine the crosslinking density. Using the Peppas–Merrill equation, I subsequently estimated the average pore size within the hydrogel network and the corresponding diffusion coefficients of glucose in the aqueous medium. In addition to mechanical characterization, I also performed glucose release tests in water. I measured the concentration of released glucose during the first 60 minutes at 10-minute intervals, followed by 30-minute intervals during the next hour. UV–Vis spectroscopy was used to determine glucose concentration, and then I calculated the diffusion coefficients. The results were compared with the values calculated from rheological measurements. The findings of the study demonstrate that combinations of ionic crosslinkers do not follow a principle of linear averaging, but instead produce pronounced synergistic or antisynergistic effects that influence both mechanical behavior and diffusion processes. Ion mixtures can mechanically strengthen or loosen the polymer network, thereby increasing or decreasing glucose diffusion. The results confirm that by combining different ionic crosslinkers, it is possible to precisely control stiffness, crosslinking density, pore size, and consequently the release rate of active compounds. hidrogeli zamreževanje hitrost sproščanja hitrost zamreženja hydrogels crosslinking release rate crosslinking rate true false false Slovenski jezik Angleški jezik Magistrsko delo/naloga 2026-05-29 07:15:23 2026-05-29 07:15:51 2026-06-19 09:53:50 0000-00-00 00:00:00 2026 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 25503 282196995 Velecic_Simon_-_Vpliv_dvovalentnih_in_trovalentnih_kationov_na_mehanske_lastnosti_in_sproscanje_.pdf Velecic_Simon_-_Vpliv_dvovalentnih_in_trovalentnih_kationov_na_mehanske_lastnosti_in_sproscanje_.pdf 1 CD598DCD80B77A1E318A8C7F0D8D10C2 29056820547606ba31d8e517b23051b924f7b096934fa32f745c36dfb03a6f52 30b853be-5b1d-11f1-b0ab-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=234632 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0