Low Temperature Block Copolymer Processing for Biomedical Applications
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Block copolymers with amphiphilic properties have found a wide range of pharmaceutical applications. Pluronic (poloxamer), a FDA approved block copolymer, can self assemble into temperature sensitive micelle form. At low temperature below critical micellization temperature, micelles dissociate to unimers, but when with cargos loaded in the core, the kinetics of polymeric micelles would behave very differently. Motivated by these, the thesis examined the low temperature processing of temperature responsive pluronic block copolymer for biomedical applications. Chapter 1 provided a comprehensive background on porphyrins, phthlocyanines (Pcs), naphthalocyanines (Ncs) that are actively exploited as contrast agents for bioimaging or photosensitizers for phototherapy. Extreme hydrophobicity of these dyes induced the formation of frozen pluronic micelles that will further be discussed in chapter 2 and 3. Chapter 2 introduced a family of nanoparticles formulated by pluronics and Pcs/Ncs for the first ideal contrast agent of photoacoustic imaging of intestine. Chapter 3 described a general drug delivery system for numerous drugs: hydrophobic drug induced frozen pluronic micelles with extremely high drug-to-excipient molar ratio and reduced side effects. Chapter 4 briefly demonstrated a phenomenon of reversible conversion between microcrystals and nanoparticles with the assistance of pluronic by changing temperature for potential pharmaceutical use, e.g. temperature feedback device or tuning temperature-mediated properties of drugs. Chapter 5 presented a brief discussion and some future directions. The low temperature processing of block copolymer for the generation of induced frozen micelles presented in the thesis is expected to solve many essential problems in biomedical applications.