Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor(s)

Shuiqin Zhou

Subject Categories

Chemistry

Abstract

Stimulus-responsive polymer microgels swell and shrink reversibly upon exposure to various environmental stimuli such as change in pH, temperature, ionic strength or magnetic fields. Therefore, they become ideal candidates for biomaterial applications. For this work, we focus on the several intelligent microgels and their application on two areas: the cell scaffold and the drug delivery system.

As for the cell scaffold, it can be realized by colloidal supra-structure microgels, which constructed by the thermo-driven gelation of the colloidal dispersion of poly(N-isopropylacrylamide-co-acrylamide) poly(NIPAM-co-AAm) microgels (Chapter 3). Such microgels exhibit a reversible and continuous volume transition in water with volume phase transition temperature (VPTT) 35 oC and remain partially swollen and soft under physiological conditions. More importantly, the size of the microgel particles can affect the sol-to-gel phase transition of the microgel dispersions, alter the syneresis degree of the constructed colloidal supra-structures, and tailor the cytocompatibility. The constructed colloidal supra-structure can be regarded as a model system for a new class of cell scaffolds.

As for drug delivery system, Chapter 4 and Chapter 5 focus on the development of biocompatible microgels-based systems for delivering a traditional anti cancer drug curcumin. These thermo-responsive core-shell structure microgels are constructed from oligo(ethylene glycol) as a hydrophilic shell and hydrophobic biocompatible materials as core, such as poly(2-vinylanisole) and poly(4-allylanisole). The rationally designed core chain networks can effectively store the hydrophobic curcumin drug molecules via hydrophobic interactions, thus provide high drug loading capacity; while thermo-sensitive nonlinear poly(ethylene glycol) (PEG) gel shell can trigger the drug release by local temperature change, offering sustained drug release profiles. In Chapter 5, additionally embedded of magnetic Fe3O4 nanoparticles enable such hybrid nanogels to delivery pharmaceuticals to a specific site of the body by applying a gradient magnetic field.

Chapter 6 investigated a class of well-defined glucose-sensitive microgels as an insulin drug release carrier, obtained via polymerization of 4-vinylphenylboronic acid (VPBA), 2-(dimethylamino) ethyl acrylate (DMAEA), and andoligo(ethylene glycol)methyl ether methacrylate (MEO5MA). The presence of MEO5MA monomer could retard the glucose-sensitive network from swelling because the rapid hydrogen bonding between the glucose molecules and the ether oxygens of the MEO5MA is prior to the glucose binding to the PBA groups. Therefore, the set point of glucose sensitivity of microgels could be adjusted possibly and result in potential biomedical applications. Compared to the non-imprinted copolymer microgels, the glucose imprinting of the microgels can create and rigidly retain more binding sites complementary to the shape of the target glucose molecule in the crosslinked polymer network, thus improve the sensitivity and selectivity of the microgels in response to the glucose level change. Additionally, the introduction of fluorescent Ag nanoparticles (NPs) to the microgels can realize the integration of optical glucose detection and self-regulated insulin delivery into a single nano-object.

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Chemistry Commons

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