Hydrogel Technologies to Prevent Vaginal Toxicity and Promote Healing after Pelvic Radiotherapy

In 2022, one million women in the U.S. were diagnosed with pelvic cancers¹ , and roughly half required radiation therapy. About half of patients undergoing pelvic radiation experience vaginal stenosis, which adversely affects vaginal health, sexual function, and examinations. To mitigate this, an injectable bioadhesive hydrogel was synthesized to address post-radiotherapy damage to the vaginal canal by positioning damaged tissue apart. To promote re-epithelialization of vaginal mucosal tissue, polylactic-co-glycolic acid microspheres (PLGA-MS) loaded with estradiol (E2) were synthesized and will be embedded in the bioadhesive. Embedding E2 loaded PLGA-MS will help promote the normal healing process.

8-arm polyethylene glycol vinylsulfone (PEG-VS) was crosslinked with VPM, a dithiol protease-cleavable peptide, to generate bioadhesive hydrogels^2-3. PEG-VS reacts with thiol-rich tissue and offers tunable gelation kinetics, ensuring easy injecatbility⁴. To address vaginal toxicity and promote healing post-pelvic radiotherapy effectively, the hydrogels must be mechanically optimized, easily injectable, bioadhesive, and compatible with a controlled release drug delivery system.

Mechanical characterization of 20kDa PEG-VS (8%, 10%, and 12% w/v) bioadhesives was done using ASTM F2150-19 to characterize compressive moduli. The bioadhesives (n=3 per formulation) were placed in phosphate buffered saline (PBS) to swell overnight before testing. Increasing PEG-VS concentration saw an increase in bioadhesive stiffness. To optimize injectability, bioadhesives were formulated at different pH values (3.0, 6.5, and 7.5), and rheometric analysis was done using ASTM D2556 to determine gelation kinetics. The bioadhesive solutions (n=4 per formulation) were casted onto the rheometer to polymerize while the test was run. pH 6.5 was found to provide an appropriate working time of 15 minutes for ease of injection. Preliminary bioadhesion testing was done using ex-cadaveric vaginal tissue. The bioadhesives were cast onto the tissue using a 5 mm biopsy punch that remained in place for 20 minutes. The tissues were washed in 1X PBS. Visual inspection showed strong adherence of the bioadhesive to tissue. To test feasibility of using PLGA-MS in our bioadhesives, PLGA-MS were prepared using a single-emulsion technique. PLGA-MS were imaged on a microscope and analyzed using ImageJ for size and distribution analysis (n=150). The average particle size was 45-50 microns, which led to an appropriate size for embedding into bioadhesives during polymerization⁵. E2-loaded PLGA-MS embedded bioadhesives will be characterized the same as those without the embedded PLGA-MS. Future studies aim to optimize the stiffness of the bioadhesive to match that of vaginal tissue and study the controlled release of E2-loaded PLGA-MS embedded in the bioadhesives.

References

1. SEER*Explorer: An interactive website for SEER cancer statistics [Internet]. Surveillance Research Program, National Cancer Institute. [Cited 2022 Apr 15]. Available from https://seer.cancer.gov/explorer/.

2. Han WM, Anderson SE, Mohiuddin M, et al. Synthetic matrix enhances transplanted satellite cell engraftment in dystrophic and aged skeletal muscle with comorbid trauma. Sci Adv. 2018;4: eaar4008.

3. Patterson, J., & Hubbell, J. A. (2010). Enhanced proteolytic degradation of molecularly engineered peg hydrogels in response to MMP-1 and MMP-2. Biomaterials, 31(30), 7836–7845. https://doi.org/10.1016/j.biomaterials.2010.06.061

4. Wang, J., Youngblood, R., Cassinotti, L., Skoumal, M., Corfas, G., & Shea, L. (2020). An injectable peg hydrogel controlling neurotrophin-3 release by affinity peptides. Journal of Controlled Release, 330, 575–586. https://doi.org/10.1016/j.jconrel.2020.12.045

5. DiStefano TJ, Vaso K, Panebianco CJ, Danias G, Chionuma HN, Kunnath K, Karoulias SZ, Wang M, Xu P, Davé RN, Sahoo S, Weiser JR, Iatridis JC (2022). Hydrogel-Embedded Poly(Lactic-co-Glycolic Acid) Microspheres for the Delivery of hMSC-Derived Exosomes to Promote Bioactive Annulus Fibrosus Repair. Cartilage, 13(3). PMID: 36040157.