Development of Polymeric Porphyrin Imaging Contrast Agents
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Biomedical applications of porphyrins and related molecules have been extensively pursued in the context of photodynamic therapy. The combinations of porphyrins’ and derivatives’ optical properties and generation of singlet oxygen make them candidate as theranostic agents. However, their hydrophobicity limit their biomedical applications. Most of the commonly used organic reactive groups can be incorporated on the porphyrin rings, which leads to a convenient way for modifying porphyrins with various hydrophilic polymers and increases the water solubility. Motivated by these, this thesis talks about several polymer modified hydrophilic polymeric porphyrin probes for various biomedical applications. Chapter 1 provides a comprehensive background of porphyrin, phthalocyanine (Pcs) and naphthalocyanine (Ncs), and their currently process in theranostic applications as contrast agents for bio-imaging and photosensitizers for phototherapy. The hydrophilic modifications of these hydrophobic porphyrin and derivatives will further be discussed in the following chapters. Chapter 2 introduces a water-soluble porphyrin-PEG crosslinked polymer used as contrast agent for fast detection of acute renal failure based on fluorescent and PET imaging. Chapter 3 describes the hydrophilic modification to a hydrophobic naphthalocyanine through axial conjugation with long-chain PEG molecules, which helps to extend the blood circulation time for photoacoustic vascular imaging. Chapter 4 demonstrates Sn-porphyrin-PEG corsslinked biocompatible hydrogels used as a pH sensitive fluorescent detector. Chapter 5 presentes a brief discussion and some future directions. Polymeric modifications of porphyrins has potential to help to solve problems in biomedical applications.