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Abstract: Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monoliths (PolyGMA) were synthesized by high internal phase emulsion (HIPE) templating and polymerisation. The porous monoliths exhibited a hierarchical porous structure with primary pores (cavities, average diameter 35 µm) interconnected by secondary pores (average diameter 5 µm). FTIR spectroscopy confirmed the chemical composition and identified characteristic functional groups of both GMA and EGDMA. The polyGMA materials were ground and sieved to obtain particles between 710 µm and 1000 µm in diameter, which were subsequently used to immobilize the enzyme β-galactosidase. Immobilization was performed using two methods, namely direct binding via epoxide groups and binding after the activation with glutaraldehyde. The glutaraldehyde method resulted in higher enzyme loading (0.43 mg of enzyme per 100 mg of polyGMA) and significantly improved catalytic activity compared to direct binding. The immobilized β-galactosidase was used for lactose hydrolysis under various conditions using both batch and flow-through reactors. Optimal activity was observed at pH 6.5 and 35°C, with kinetic parameters vmax = 0.64 mmol∙L -1 ∙min-1 and �� = 38.8 mmol∙mol-1 . Reuse tests showed stable performance over five cycles. Comparatively, non-porous polyGMA exhibited negligible enzymatic activity compared to polyHIPE supported enzyme. In addition, lactose hydrolysis was investigated in a flow-through system at different flow rates (0.5–2.5 mL∙min- ¹). The highest conversion (100%) was observed at a flow rate of 0.5 mL∙min-¹, while a higher flow rate of 2.5 mL∙min-¹ resulted in a lower conversion (approx. 35%), both at the lactose concentration of 4 g∙L - ¹.
Keywords: immobilized enzymes, glycidyl methacrylate, polyHIPE, β-galactosidase, beta-galactosidase
Published in DKUM: 21.03.2025; Views: 0; Downloads: 0
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Abstract: PolyHIPEs are highly porous polymers with an interconnecting porous structure. They have found usage in the removal of pollutants, water clean-up, oil spill removal, catalysis, controlled release of active compounds, wound dressing and tissue engineering. The wide applicability of polyHIPEs is possible through their inherent porosity and chemical diversity. The aim of this dissertation was to increase the chemical diversity of polyHIPEs, develop an efficient method for the synthesis of polyHIPE beads and to use natural resources for the synthesis of polyHIPEs, subsequently, paving the pathway to more sustainable synthetic procedures. PolyHIPEs tend to have poor mechanical properties, therefore, it was crucial to investigate the influence of the internal phase volume, initation type (photo vs thermal) and monomer functionality on the mechanical and morphological properties of thiol-ene polyHIPEs. The results show that the main factors influencing the morphological and mechanical properties are the monomer structure and the internal phase volume. Besides the inherent porosity and chemical versatility typical of polyHIPEs, they can also be produced in various shapes, e.g., monoliths, membranes and beads. Therefore, the dissertation also focuses on the synthesis of polyHIPE beads. The polyHIPE beads were produced through the usage of water-in-oil-in-water (W/O/W) multiple emulsions. To enable the synthesise of open porous polyHIPE beads, thiol-ene polymerisation was combined with photopolymerisation to guarantee a rapid polymerisation prior the break-down of the multiple emulsion. Consequently, it was possible to synthesise polyHIPE beads. The first study showed that by altering the thiol to acrylate ratio in favour of the acrylate the degradation rate of the synthesised polyHIPE beads gets reduced. Additionally, it was demonstrated that the beads can be readily functionalised with allyl amine and used for the adsorption of methylene blue (12.0 mg/g in 24 hours). The next study combined polyHIPE beads with magnetic nanoparticles (MNPs) to produce magnetic polyHIPE beads which were used for the removal of Pb2+. To produce the magnetic polyHIPE beads, magnetic nanoparticles (MNPs) were added to the organic phase. The MNPs get incorporated into the polymer-network after the polymerisation, therefore, forming magnetic polyHIPE beads. The MNPs were shown to influence the morphology and the size of the beads. Additionally, the polyHIPE beads were shown to remove up to 97.0 % of Pb2+ after 24 hours from a 2.9 mg/L solution of Pb2+. In the last study related to the synthesis of polyHIPE beads, functional polyHIPE beads were produced and then functionalised to enable the binding of the enzyme invertase. These beads were then utilised for the hydrolysis of sucrose. The conversion of sucrose to glucose and fructose was 100% after 60 minutes for the polyHIPE beads, while the conversion for non-porous beads was only 6.5%. The last part of the thesis focused on more sustainable/natural approaches to polyHIPE synthesis. The first study utilised limonene as a replacement to conventional solvents (e.g., cyclohexane) in the production of O/W HIPEs and the polymerisation thereof into polyHIPEs. It was shown that limonene can be used as an efficient replacement in the production of polyHIPEs. The next study used natural resources (terpenoids) which were modified to contain polymerisable units, which were used for the synthesis of terpenoid-based polyHIPEs. The synthesised monomers were then crosslinked with 5 and 10 mol. % TMPTA to form polyHIPEs, consequently producing porous polymers. The last study in this thesis used the terpenes limonene, carvone and myrcene to produce bio-based polyHIPEs by utilising multifunctional acrylates (PETA and TMPTA) as the comonomers. This study demonstrates that it is possible to prepare polyHIPEs from commercially available terpenes, therefore, moving the field of polyHIPEs into a more sustainable direction.
Keywords: HIPE, PolyHIPE, Multiple Emulsions, Functional polyHIPEs, Natural Polymers, Terpenes
Published in DKUM: 08.12.2023; Views: 456; Downloads: 103
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Abstract: Namen tega dela je razložiti sintezo poliHIPE, ki vsebujejo celulozo. PoliHIPE so bili pripravljeni z uporabo emulzij olja v vodi (O/W). Vodna (kontinuirana) faza je bila sestavljena iz akrilne kisline (AA), karboksimetilceluloze (CMC), N,N′-metilenbisakrilamida (MBA), površinsko aktivne snovi in ustreznih iniciatorjev, medtem ko je bila oljna (notranja) faza toluen. Polimerizacija je potekala termično pri 60 ºC 24 ur. Dobljeni polimeri so imeli diskontinuitetno morfologijo poliHIPE z različnimi premeri, odvisno od stopnje zamreženja in količine CMC. Zanimivo je, da sta prisotnost CMC in višja stopnja zamreženja (30 %) povzročila nastanek večjih por, ki so v bistvu oblikovale material s tremi stopnjami poroznosti - primarno, sekundarno in terciarno. Velikost por je bila od približno 32 μm (0 % CMC) do 260 μm (1 % CMC), površina BET pa se je gibala od približno 1,3 m2/g do 3,9 m2/g. PoliHIPE smo uporabili tudi za adsorpcijo metilen modrega (MB). Pokazalo se je, da prisotnost CMC poveča adsorpcijo MB, vendar se pri višjih koncentracijah CMC adsorpcija zmanjša, kar kaže, da je idealna količina CMC pod 2,5 % (raztopina CMC).
Keywords: PolyHIPE, akrilna kislina, celuloza, adsorpcija, poroznost
Published in DKUM: 22.09.2021; Views: 1136; Downloads: 68
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Abstract: Tkivni inženiring hrustančnega tkiva še vedno nudi številne možnosti za izboljšavo, navkljub intenzivnim raziskovalnim naporom v zadnjem času. Razvoj umetnih materialov in 3-D celičnih nosilcev ima pomembno vlogo pri regeneraciji hrustančnega tkiva. Zanimiv pristop pri izdelavi celičnih nosilcev predstavlja izgradnja s pomočjo emulzij. Nastali material, imenovan polyHIPE (PHP), je sintetični visoko porozen polimer, ki ga pripravimo s polimerizacijo visokega deleža notranje faze emulzij (HIPEs – high internal phase emulsions). Glavni cilj te doktorske disertacije je raziskati možnosti za tvorbo hrustančnega tkiva znotraj celičnih nosilcev pripravljenih iz PHP materiala. Proizvodnjo PHP nosilcev smo posebej prilagodili tkivnemu inženiringu hrustanca, tako da smo pripravili porozne (85 %) strukture s primarno velikostjo por v območju 50–170 m. Pokazali smo, da je PHP material biokompatibilen s človeškimi sklepnimi hondrociti, kar smo ovrednotili s pomočjo testa za preživetje celic (Live/Dead kit) in histološko analizo. Opazovali smo hondrocite z okroglimi jedri, ki so bili organizirani v večceličnih plasteh na površini PHP nosilca in so rastli približno 300 m v notranjost nosilca. Kopičenje kolagena tipa 2 smo dokazali s pomočjo imunohistokemije, molekularna analiza je pokazala izražanje hrustančno specifičnih genov z ugodnim razmerjem kolagena tipa 2 in tipa 1. Dodatno so bili PHP vzorci biološko razgradljivi, njihove osnovne mehanske lastnosti pa primerljive z nativnim sklepnim hrustancem. Izsledki raziskave dokazujejo, da je zasnovan PHP celični nosilec primeren za nadaljnjo uporabo v tkivnem inženiringu hrustančnega tkiva.
Keywords: humani sklepni hrustanec, tkivni inženiring, biokompatibilni celični nosilec, sintetični polimer, polyHIPE, diferenciacija hondrocitov
Published in DKUM: 17.10.2017; Views: 2333; Downloads: 290
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Abstract: Development of artificial materials for the facilitation of cartilage regeneration remains an important challenge in orthopedic practice. Our study investigates the potential for neocartilage formation within a synthetic polyester scaffold based on the polymerization of high internal phase emulsions. The fabrication of polyHIPE polymer (PHP) was specifically tailored to produce a highly porous (85%) structure with the primary pore size in the range of 50–170 μm for cartilage tissue engineering. The resulting PHP scaffold was proven biocompatible with human articular chondrocytes and viable cells were observed within the materials as evaluated using the Live/Dead assay and histological analysis. Chondrocytes with round nuclei were organized into multicellular layers on the PHP surface and were observed to grow approximately 300 μm into the scaffold interior. The accumulation of collagen type 2 was detected using immunohistochemistry and chondrogenic specific genes were expressed with favorable collagen type 2 to 1 ratio. In addition, PHP samples are biodegradable and their baseline mechanical properties are similar to those of native cartilage, which enhance chondrocyte cell growth and proliferation.
Keywords: polyester, polymerization, polyHIPE
Published in DKUM: 23.06.2017; Views: 1985; Downloads: 415
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