Photo-crosslinkable hydrogels through click chemistry to deliver complex protein cocktails and nanoencapsulated drugs

Osteoarthritis is the most common form of arthritis worldwide. This clinical condition, typically, leads to the degeneration of the osteochondral interfaces in the joints, as the result of a complex pathophysiologic process, characterized by a chronic inflammatory microenvironment, for which no curative treatments are currently available. New approaches to promote cartilage regeneration through the application of biomaterials, proteins/drugs delivery and/or stem cells have been actively explored by the scientific community. The main ideas explored rely in the application of bioactive factors to minimize the inflammatory process or to induce stem cells’ differentiation into chondrocytes, so new cartilagenative extracellular matrix (ECM) can be produced. Given this, in situ photo-crosslinkable hydrogels have been reported for its excellent performances on the delivery of bioactive factors, mainly due to its biocompatibility, loading potential and control over the release kinetics of the bioactive content. As such, this thesis explores the development of photocrosslinkable hydrogels, through click chemistry, and its application as a delivery system of proteins and nanoparticles/drugs. For this, hyaluronic acid (HA), a major component of hyaline cartilage ECM, was chemically modified with norbornene anhydride groups, through a two-pot reaction to produce an injectable and in situ photo-crosslinked platform. The controlled modification of the HA biopolymer allowed the control over its degree of substitution and, therefore, over its photo-crosslinking kinetics. The modified biopolymer was applied in the encapsulation of human platelet lysates (hPLs) and human bone marrow mesenchymal stem cells (hBM-MSCs) using UV-induced photo-crosslinking. The loading of hPLs promoted the encapsulated hBM-MSCs proliferation. Adding to this, Zein-HA nanoparticles (NPs), loaded with the flavonoid, Icariin, and Zein-HA-norbornene NPs were produced and used in the production of bioactive nanocomposite hydrogels for the focal delivery of flavonoids and hPLs. The encapsulation of Icariin in the nanoparticles promoted its release over 7 days. Further assays to access chondrogenesis and anti-inflammatory effects, should confirm the applicability of the developed biomaterial on the regeneration of cartilage. In the future, it is expected that this nanocomposite hydrogel successfully promotes cartilage regeneration through native stem cells’ stimulation as the result of the intra-articular injection of these systems and, consequently, of its bioactive content release.