Researcher(s)
- Elaine Kachala, Biomedical Engineering, University of Delaware
- Ann Thomas, Biomedical Engineering, University of Delaware
- Shashika Gammanchiralage, Biomedical Engineering, University of Delaware
Faculty Mentor(s)
- Christopher Price, Biomedical Engineering, University of Delaware
- Kristi Kiick, Biomedical Engineering and Material Science and Engineering, University of Delaware
Abstract
Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, most commonly affecting the knee. Presently, no disease-modifying OA therapeutics exist, leaving patients to only ineffective symptom-targeting drugs. One hurdle in developing efficacious disease-modifying and pain-relieving drugs is rapid drug clearance and low tissue retention, even following intra-articular (i.a.) injection into the joint. To address this, our team has developed an innovative elastin-collagen peptide nanovesicle (ECnV)-based drug delivery platform, which can bind to damaged/denatured collagen while exhibiting thermo-responsive drug loading and release behaviors. We intend to investigate the localization and retention of fluorescently labeled, unloaded ECnVs following i.a. injection into adult mouse knee joints using multiscale bioimaging approaches. However, visualizing deep-tissue distribution of ECnVs within intact joints requires optical clearing of tissues for confocal imaging. However, tissue clearing approach and clearing solvent choice can significantly impact ECnV interactions/stability and fluorescent intensity. In this study, we evaluated a panel of tissue clearing protocols for their ability to retain ECnV structural and optical/fluorescence integrity. Our findings aim to guide clearing method selection for future imaging studies of i.a. ECnV targeting and retention. To assess nanoparticle structural/fluorescent stability, ECnVs were tagged with a far-red fluorophore (AZ647) and encapsulated in GelMA hydrogels. Following fixation and decalcification, gels were subjected to various tissue clearing protocols, including aqueous (TDE) and non-aqueous methods (PEGASOS, BABB, THF-DBE, ECi, MS, and THF–BBPEG). THF-BBPEG ranked the best in ECnV structural preservation, AZ647 fluorescent intensity, and tissue clearing quality. Based on these findings, we subsequently utilized the THF–BBPEG protocol to optically clear mouse knee joints that had been intra-articularly administered AZ647-labeled ECnVs. In these cleared tissues, ECnVs exhibited strong fluorescence, enabling high-resolution confocal imaging of particle distribution. These results highlight the critical role of clearing solvent–delivery vehicle compatibility in nanoparticle-based imaging and delivery studies.