Preparation and characterization of poly(2-alkyl-2-oxazoline)-based platforms for biological applications

Date

2025-1-06

Author

Gündoğdu, Dilara

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This study aimed to use temperature-responsive poly(2-isopropyl-2-oxazoline) (PiPOX) and pH-responsive tannic acid (TA) to functionalize surfaces through layer-by-layer (LbL) self-assembly technique for various biological applications. The first part of the study reports on LbL modification of physical hydrogels using PiPOX and TA and examines the potential of the LbL hydrogels as dual responsive dual drug releasing platforms for antibacterial applications. Alginate (ALG)/Ca²⁺ hydrogel was used as a model template, whereas ciprofloxacin (CIP) and curcumin (CUR) were used as model drugs. CUR was incorporated into CaCO₃ microparticles and embedded into the hydrogels during gelation, while CIP was included within the multilayers. LbL modification led to greater swelling, imparted temperature-responsiveness, provided enhanced drug release with increasing temperature at pH 7.4 and reduced drug release at acidic conditions regardless of the temperature. The antibacterial activity was found to be greater at pH 7.4 than pH 5.5 against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). CIP and CUR acted in a combinatorial manner and enhanced antibacterial activity against E. coli. The second part of the study reports on the preparation of compartmentalized LbL microcapsules using PiPOX, TA, glucose oxidase (GOx), horseradish peroxidase (HRP) and poly(L-lysine) (PLL) as building blocks. The potential use of capsules as stimuli-responsive microreactors and the effects of temperature/pH on the enzymatic cascade reactions were examined. Enzymatic cascade activity was greater at pH 5.5 than that at pH 7.4. The enzymatic activity enhanced when the temperature (37 °C) approached the critical temperature of PiPOX. The effect of temperature-induced conformational changes within the multilayer capsule wall on the enzymatic cascade activity was more remarkable when the number of PiPOX layers between the compartments was increased. HeLa cells incubated with LbL capsules showed high level of viability and capsules demonstrated marked association with the cell membrane. Overall, this study generated fundamental knowledge on functionalization of various surfaces using PiPOX/TA and understanding the structure-property relationship in the resulting multilayer polymer platforms.

Subject Keywords

Layer-by-layer Self-assembly Technique, Hydrogel, Drug Release, Multilayer Capsule, Enzymatic Cascade Reaction

URI

https://hdl.handle.net/11511/113535

Collections

Graduate School of Natural and Applied Sciences, Thesis