Browsing by Subject "poly(2-oxazoline)"
Now showing items 1-4 of 4
-
(2020)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.
-
(2022)In this project, poly(2-methyl-2-oxazoline)-block-poly(2-n-butyl-2-oxazine)-block-poly(2-methyl-2- oxazoline) (PMeOx-b-PnBuOzi-b-PMeOx) and poly(2-methyl-2-oxazoline)-block-poly(2-n-propyl-2- oxazine) (PMeOx-b-PnPrOzi) with block lengths of 35-20-35 and 100-100, respectively, were synthesized. When dispersed in water these thermoresponsive polymers aggregate into micellar aggregates or form hydrogels. Polymers were characterized with 1H-NMR, GPC, and DLS. Age-related macular edema and diabetic macular edema are the most common reasons for blindness in industrialized countries. The triamcinolone acetonide, a corticosteroid used to treat both of these macular edemas, was loaded into the polymeric micelles or hydrogel of synthesized polymers using the thin film method. The loading efficiency for a triblock copolymer ((PMeOx35-b-PnBuOzi20- b-PMeOx35) polymeric micelles was 4 % at the polymer/drug ratio of 10/4 and for a hydrogel (PMeOx100-b-PnPrOzi100) it was 48 % with the same polymer/drug ratio. The properties of the PMeOx100-b-PnPrOzi100 hydrogel formulations with the drug were studied with rheological measurements, DSC, DLS, and GPC of formulations. The formulation showed storage modulus of 3 kPa and the gelation temperature at 16 °C. From the DSC two glass transition temperatures were obtained, Tg1 at around 12 °C and Tg2 at around 74 °C. The particle size distribution of the formulation obtained with DLS showed that there were assumingly micelles or vesicles with a hydrodynamic radius between 20 and 80 nm. The drug release from the hydrogel formulation was studied with the dialysis membrane method and all the drug was released within 24 hours. Both copolymers formed quite unstable formulations with the drug. The results from this study gives information how polyoxazoline- and polyoxazine-based materials can be used to encapsulate and release corticosteroids, such as triamcinolone acetonide. To increase the drug loading capacity and to stabilize formulations, some surfactants for the drug could be tested in the future.
-
(2024)In this master’s thesis, linear zwitterionic poly(ethylene imine) methyl-carboxylates (l-PEI-MCs) were synthesized through a four-step synthesis. The synthesis started with the polymerization of 2-ethyl-2-oxazoline (EtOx) monomers into poly(2-ethyl-2-oxazoline) (PEtOx) homopolymers with polymerization degree of 50 and 100. Living cationic ring-opening polymerization (LCROP) enabled a good control over the molecular weights. Subsequently, the side chains of PEtOxs were cleaved off by acidic hydrolysis. This resulted in linear poly(ethylene imine)s (l-PEIs) bearing a secondary amine group in repeating units of the polymer chain. These amine units were then functionalized with methyl-carboxylate moieties by first introducing tert-butyl ester functionalities to l-PEI chains, and subsequently cleaving off the tert-butyl groups. The final polymer is a polyzwitterion, featuring both an anionic carboxylate and a cationic tertiary amine group within a single repeating unit. Polymers produced in each step were characterized via 1H-NMR and FT-IR spectroscopy and their thermal properties were analyzed by differential scanning calorimetry (DSC). The molecular weights and dispersities (Ð) of PEtOx polymers were additionally estimated by gel permeation chromatography (GPC). Via 1H-NMR, the degree of polymerization for PEtOxs and the hydrolysis degree for l-PEIs were determined. FT-IR gave a further insight into the structures of polymers, successfully confirming the ester functionality of modified l-PEI. The disappearance of the tert-butyl proton signal in 1H-NMR spectrum after deprotection verified the successful removal of tert-butyl groups, resulting in the final product with methyl-carboxylate functionalities. By DSC, different thermal transitions, i.e., glass transition (Tg), melting (Tm) and crystallization (Tc), were observed, and the effects of molar mass and polymer modifications on these transitions were being investigated. The state of the art explores the literature regarding synthesis and properties of poly(2-oxazoline)s (POx), poly(ethylene imine)s (PEIs), and polyzwitterions. The theory behind living cationic ring-opening polymerization of 2-oxazolines and acidic hydrolysis of POxs is described. Different post-polymerization modification strategies to functionalize PEIs are being discussed. In addition, possible applications for each of these polymer classes are shortly outlined.
-
(2023)Bioprinting has emerged as a cutting-edge technology to overcome the shortage of tissues and organs by the precise deposition of living cells and biomaterials into three-dimensional (3D) biomimetic constructs. However, the inadequate choice of bioinks has limited its widespread implementation and clinical transformation. Natural polymers, such as chitosan and alginate, are commonly used as bioinks due to their biocompatibility, biodegradability and similarity to extracellular matrix (ECM). These natural polymers are usually limited by their mechanical strength and have less tunable mechanical characteristics. Instead, synthetic polymers offer adjustable mechanical properties and good printability, and they are often used as sacrificial materials in 3D bioprinting. Hybrid hydrogels consisting of Pluronic F127 (PF) and natural polymers have been suggested to have good printability and rheological behaviors. However, PF tends to be cytotoxic at concentrations required for good printability. Another synthetic copolymer which comprises poly(2-methyl-2-oxazoline) (POx) (A-block) and poly(2-n-propyl-2-oxazine) (POzi) (B-block) was investigated as the potential alternative for PF. In this work, two different hybrid platforms consisting of synthetic POx-b-POzi /natural polymer (chitosan or alginate) and PF /natural polymer (chitosan or alginate) were formulated. The main focus of the study were on their printability and the potential of POx-b-POzi to replace PF as a sacrificial material in 3D bioprinting. POx-b-POzi and PF-based hybrid hydrogels were formulated and their printability was evaluated by rheology, mechanical compression, and 3D printing and printability assessment tests. The results showed that both POx-b-POzi and PF based hybrid hydrogels can be printed into different 3D structures, and the printed structures were successfully crosslinked. Although, the printability assessment tests and rheology showed that PF based hydrogels exhibits greater printability, POx-b-POzi also meets the critical requirements for bioinks.
Now showing items 1-4 of 4