Synthesis and Characterization of Biodegradable and Fluorescent Biomaterials for Dual-Mode Imaging Applications

Markham, Andrew

Synthesis and Characterization of Biodegradable and Fluorescent Biomaterials for Dual-Mode Imaging Applications

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markham_andrew_2025_thesis.pdf (3.27 MB)

Date

2025-10-10

Authors

Markham, Andrew

Abstract

This thesis presents the design and characterization of a biodegradable polymer incorporating fluorescence and ultrasound imaging functionalities within a single covalently bonded structure. The dual-imaging scaffold (hereafter named DIE-PCL) was synthesized via polycondensation of citric acid and cysteine, forming a thiazolopyridine (TPA) fluorophore. TPA was reacted with polycaprolactone diol (MW ~2000 Da), followed by amidation with aniline tetramer, a photoacoustic active moiety. Structural, mechanical, biological, and optical characterizations confirmed successful integration of the TPA fluorophore and photoacoustic-active groups. DIE-PCL retained cytocompatibility and compressive strength comparable to control polymers and was clearly visible via ultrasound imaging in ex vivo soft tissue. While fluorescence intensity was modestly reduced relative to TPA-only material, signal retention confirmed optical integrity. Although photoacoustic function was not directly tested, imaging potential was evaluated using ultrasound. This work provides a means for a chemically integrated, multimodal imaging scaffold with translational potential for real-time, non-invasive monitoring of biodegradable implants.

Summary for Lay Audience

In modern medicine, there is growing interest in materials that not only support healing but also allow surgeons to monitor their performance from outside the body. Imagine an implant that gradually dissolves as tissue regenerates and glows under special lighting or shows up clearly in an ultrasound scan. This thesis focuses on developing such a material: a biodegradable polymer that can be tracked using both fluorescent and ultrasound imaging techniques. The material is made from a combination of safe, well-studied components, including citric acid, the amino acid cysteine, and a medical-grade polymer known as polycaprolactone. It also includes two specialized features: a fluorescent structure called TPA, which makes the material glow under ultraviolet light, and a light-absorbing molecule called aniline tetramer, which may enable detection using photoacoustic imaging. These imaging functions are chemically built into the material itself, rather than mixed in after the fact, making the design more stable and easier to control. In laboratory tests, the polymer was shaped into small discs, films, and microparticles. It retained strong visibility under ultrasound and emitted a consistent fluorescent signal, although the brightness was slightly reduced when both imaging agents were included. The material was structurally strong for the intended application, showed little degradation over a four-week period, and was compatible with healthy cell growth in cell culture experiments. While the potential for photoacoustic imaging was a key part of the design, this feature was not directly tested in this study and remains a target for future research. This work represents a proof-of-concept for a new class of biodegradable materials that can be monitored in real time using non-invasive imaging. These “self-reporting” implants would one day allow doctors to track how a material is performing or degrading inside the body without needing repeated surgeries of biopsies. It’s a promising step toward safer, smarter, and more personalized medical treatments.