Nature-Inspired Tissue Adhesive Biomaterials for Tissue Engineering

Abstract

The development of the tissue adhesive biomaterials has been an emerging field of translational medicine as it has the robust potential to widely utilized in cell delivering carrier, tissue sealing, wound healing, and tissue hemostasis. To date, the most widely used tissue adhesives in the clinical field are organized based on their materials and chemistry. Although there are many commercially available medical sealants and adhesives, many limitations have been reported such as inducing immune reaction and low adhesive strength specifically under wet conditions. To this end, a widespread need for the development of the ideal tissue adhesive has led to study a variety of materials and chemistry. Among the various strategies, tyrosine-containing biopolymers have attracted much attention as it exhibited the robust potential in the aspects of the water-resistant adhesive strength in a wet environment and great chemical bonds with tissue components. Along with tyrosine-containing biopolymers, tyrosinase-mediated crosslinking is an emerging method for the formation of the covalent hydrogel due to the substrate specificity, rapid gelation time, reaction under mild conditions. However, regardless of the advantages of the tyrosinase-mediated crosslinking, the wide-spread study of how the properties of materials are affected by tyrosinase reactions of tyrosine moieties and in vivo applications has not been demonstrated. <br/> In this thesis, we have discussed tyrosinase-mediated biopolymer crosslinking in three different objectives ⅰ) development and optimization of tyrosinase mediated hydrogel systems for tissue engineering (in chapter 3), ⅱ) development of recombinant tyrosinase from Streptomyces avermitilis (SA_Ty) to enhance enzyme activity and its application in injectable and sprayable approaches (in chapter 4), ⅲ) development of fast forming and tissue adhesive hydrogels with polyphenols that can modulate immune response and analysis of hydrogel functions compared to commercial products (in chapter 5). The comprehensive studies about recombinant tyrosinase mediated biopolymer crosslinking will give the inspiration to develop a novel biomaterial-based tissue adhesive hydrogel for a variety of purposes in tissue adhesive and biomacromolecule delivery. <br/> In the chapter one and two of this dissertation, we address the general introduction of the thesis and scientific backgrounds. <br/> In the chapter three of the thesis, we developed the mushroom type tyrosinase based injectable and adhesive hydrogel and represented an application in the aspects of cell delivering carrier for tissue engineering. Here we utilized enzyme-based approaches to fabricate tissue adhesive hydrogels for tissue engineering. Tyramine conjugated hyaluronic acid (HA_t) and gelatin are susceptible to tyrosinase (Ty)-mediated crosslinking in vitro and in vivo. Importantly, mechanical properties and degradation kinetics are modulated by the tyramine substitution and Ty concentrations. Also, Ty -mediated crosslinking displayed tissue-adhesive properties. Furthermore, fibrochondrocyte-laden and Ty-crosslinked hydrogels demonstrated robust biocompatibility and resulted in enhancement of cartilage-specific gene expression and matrix synthesis. Overall, this represents a potential application of enzyme-mediated crosslinking hydrogels for meniscus tissue engineering.<br/> In the chapter four of the thesis, we reported on a tissue adhesive hydrogel based on novel recombinant tyrosinase mediated crosslinking. The adhesive hydrogels were fabricated by the site-directed coupling of tyramine-conjugated hyaluronic acid (HA_t, 1% w/v) and gelatin (3% w/v) (HG_gel) with novel tyrosinase derived from Streptomyces avermitilis (SA_Ty). The enzyme-based crosslinking by SA_Ty was fast, with less than 50 seconds for complete gelation, and the SA_Ty based crosslinking enhanced the physical properties and adhesive strength of the hydrogel significantly with the native tissue samples. Furthermore, by optimizing the injection conditions, we tailored the enzyme-based crosslinking hydrogels to be injectable and sprayable with a medical syringe and commercial airbrush nozzle, respectively. An in vivo analysis of the adhesive hydrogel showed a negligible immune reaction. In this study, demonstrate that the novel enzyme-based crosslinking hydrogel has a robust potential in tissue engineering and regenerative medicine. <br/> In the chapter five of the thesis, we reported a tissue adhesive and immune modulation hydrogel inspired by the mussel chemistry and polyphenol. We conjugated tyramine (HA_T) and EGCG (HA_E) into hyaluronic acid (HA), and the hydrogel (HA_TE) was fabricated by an oxidative reaction using tyrosinase from Streptomyces avermitillis (SA_Ty). With robust oxidative nature of EGCG, the HA_TE hydrogel can be fast formed in a few seconds. We compared HA_TE hydrogel with commercial products (cyanoacrylate and fibrin glue) in the aspects of tissue adhesive and sealants. In the lap shear and burst pressure test, HA_TE exhibited the highest tissue adhesiveness regardless of wetness compared to commercial products. When HA_TE was applied as tissue adhesive into mouse wound closure, and it successfully closed wound and recovered damaged tissue. Additionally, due to EGCG naturally possesses anti-inflammation and minimize host recognition, HA_TE hydrogel produced little inflammatory cytokines in vivo that are comparable to PBS group. This demonstrates that polyphenol based hydrogel might provide a robust platform in the field of both material science and translational medicine. <br/> Nature-inspired biomaterials and chemistry in this thesis will be useful to understand the critical cues for ideal tissue adhesive biomaterials in the aspects of tissue engineering and translational medicine. We believe that this study will directly contribute to develop more enzyme-mediated tissue adhesive biomaterials and provide inspiration to the other various research fields.<br/>