Characterization of a collagen-based hydrogel crosslinked with biofunctional polyphenols

Osteoarthritis (OA) is a degenerative joint disease caused by numerous factors marked by cell stress, inflammation and joint damage, which unlike other conditions does not resolve on its own and causes chronic pain and loss of function, especially in older adults. The loss of autonomy and productivity, caused by OA, together with direct medical costs related to its treatment have significant social and economic impacts. The fact that current treatments only address symptoms without halting disease progress, with extensive surgery as a last resort, highlights the need for new form of treatment focused on stopping joint degeneration and restoring joint function to improve patient outcomes. Hydrogels are being explored as a promising treatment for OA, acting as a delivery system for drugs, biochemical signals and cells, to slow down joint degeneration and support cartilage regeneration. These polymer-based materials with their unique three-dimensional structure and adjustable mechanical and chemical properties offer a spectacularly adjustable platform for viscosupplementation, cell support and drug delivery. OA’s complex and aggressive microenvironment requires new and biocompatible ways to reenforce and make hydrogels more efficient in treating OA. Catechins and condensed polyphenols (TPHs), extracted form green tea, are renowned for their antioxidant, anti-inflammatory and antibacterial properties. In this thesis they will be studied as a possible natural crosslinker for a type I collagen-based hydrogel, to understand how they could improve the physiochemical characteristics of the hydrogel while still being able to exhibit their beneficial effects against OA. This study compared how two different crosslinking protocols for type I collagen and TPHs (simple immersion or syringe assisted mixing) differently impacted the properties of the hydrogel. All samples were properly characterized by several techniques (FTIR-ATR, UV spectroscopy, compression test, release test, FESEM, …) to investigate both qualitatively and quantitatively if the crosslinking process caused collagen denaturation, how different concentrations of TPHs and crosslinking protocols affected the physiochemical properties of the hydrogel and the dynamic of TPHs release in physiologic solution. In the end, the characterization process highlighted promising results for both crosslinking protocols, confirming TPHs to be an effective natural crosslinking agent able to enhance the mechanical properties of collagen-based hydrogels without causing its denaturation. The next step of this research could involve the characterization of more combinations between crosslinking protocols and TPHs concentrations, in order to understand how to modulate the hydrogel properties making it suitable for different types of biomedical application.