Poly(2-ethyl-2-oxazoline) modified gellan gum

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http://urn.fi/URN:NBN:fi:hulib-202006233411
Title: Poly(2-ethyl-2-oxazoline) modified gellan gum
Author: Lavikainen, Janni
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2020
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-202006233411
http://hdl.handle.net/10138/316934
Thesis level: master's thesis
Discipline: Polymeerikemia
Abstract: Ocular drug delivery is a complex field of pharmaceutics due to the unique conditions on the eye surface. Currently used drug carriers have disadvantages like irritation and blurred vision, and moreover, the bioavailability of drug formulations is low. This research aimed to synthesize novel and safe drug carriers for ocular drug delivery that could prolong retention on the eye and resist a tear washout effect. The drug carrier consists of a gellan gum that is an anionic polysaccharide having a property for in situ gelling. Gellan gum was modified with short poly(2-ethyl-2-oxazoline) grafts that have shown to have minimal unspecific organ deposition and rapid renal excretion. The choice of synthetic procedure, solvents, and reagents was dictated by biocompatibility of the materials and possible medical application. Graft copolymers were synthesized in a two-step synthetic procedure in which at first 2-ethyl-2-oxazoline was polymerized via cationic ring-opening polymerization. Next, living polymer chains were combined with deprotonated gellan gum to attach grafts onto the gellan backbone. Grafting was performed in three different degrees of grafting by changing poly(2-ethyl-2-oxazoline)-to-gellan mass ratio in the feed. Grafted copolymers were studied by nuclear magnetic resonance spectroscopy (NMR) and infrared spectroscopy (IR) and by thermogravimetric analysis (TGA). In addition, the molecular weights of PEtOx grafts were determined by size exclusion chromatography (SEC). Based on the results, synthesized copolymers had different degrees of grafting. The thermogravimetric analysis demonstrated a two-step degradation process for copolymers, in which the steps and weight losses correlated well with the grafts content. The diffusion-ordered spectroscopy (DOSY) proved that the grafting had actually taken place, but a lower diffusion coefficient for copolymer in relation to the diffusion of a native gellan revealed degradation of the backbone.
Subject: Gellan gum
poly(2-oxazoline)
cationic ring-opening polymerization
copolymer
graft
drug carrier


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