Synthesis Of Injectable Alginate-protein Hydrogels And Applications In Controlled Release And Stem Cells Scaffold

Injectable hydrogel is a biomaterial that have been extensively utilized in biomedical applications.Since it’s biocompatibility,mild gelation,and unique degradation properties,alginate-based hydrogel has attracted widely attention.However,there are still many challenges of ionically cross-linked alginate hydrogels for clinical applications.The gelation rate of ionically cross-linked alginate is rapid and poorly controlled,which may block the needle during injection and cause a heterogeneous distribution of cells or drugs within the hydrogel matrix.Another Critical drawback of ionically cross-linked alginate gels is the limited long-term stability in physiological conditions,because these gels can be dissolved due to release of divalent ions into the surrounding media due to exchange reactions with monovalent cations.In addition,alginate lacks informational structure for positive cell biological response,when used in tissue engineering functional groups have been introduced in alginate to improve its bio-interfacial interactions with cells.In view of these limitations,we synthesized alginate-protein in situ forming injectable hydrogels and investigated their potential applications in controlled release and scaffold for tissue engineering.Two novel in situ forming hydrogels was developed via ionic-covalent dual cross-linked mechanism,and crosslinked sites were characterized by Fourier transform infrared via attenuated total reflectance modes(ATR-FTIR).A rheometer was employed to investigate the elastic modulus of hydrogels.The gelation time was measured by the via inversion method.The degradation behavior of the hydrogels was determined by weight loss method.Biocompatibility of hydrogels was performed by Live-dead stain and MTT assay.Doxorubicin(Dox),an antitumor drug of clinical was used as a model drug to explored the potential application of the hydrogels in drug delivery systems for local chemotherapy.Moreover,encapsulated neural stem cells to study the injectable hydrogels as a cell scaffold for tissue engineering.The detailed research contents are as follows:The first chapter summarizes the advantages and disadvantages of the current natural and synthetic injectable hydrogel material that have been used for drug delivery and tissue engineering.The challenges and perspectives on the future of injectable hydrogel applications are discussed.An ionic-covalent dual crosslinked biological polysaccharide-protein hydrogels(SA-SF)of sodium alginate(SA)and silk fibroin(SF)was designed as an ideal injectable drug carrier in chapter two,and its application was examined with Doxorubicin(Dox)as a model drug for intratumoral anticancer drug delivery.The ATR-FTIR spectroscopy analysis was performed to characterize the presence of specific chemical groups in the hydrogels and also the effectiveness on the crosslinking process.Degradation of the in situ forming hydrogels was confirmed in vitro.Live/Dead staining assay demonstrated that SA-SF hydrogel was non-cytotoxic.The in vitro release of Dox from SA-SF hydrogel was sustained for more than 4 weeks,and the release Dox still keep its potency.In vivo experiments employing sarcoma-180 cancer cell xenograft-bearing Nude mice showed that intratumoral injection of Dox-loaded SA-SF gel inhibited the growth of tumors more effectively than injection of free Dox.This hydrogel delivery system also reduced cardiac toxicity of Doxorubicin in mice.The results obtained from this study demonstrate the potential application of a biodegradable hydrogel as an anti-cancer drug delivery system for successful chemotherapy.Injectable and degradable hydrogels(SA-G)based on sodium alginate(SA)and gelatin(G)were developed by ionic-covalent dual crosslinked in chapter three.We focused on the physical characteristics of the hydrogels(e.g.crosslinking density,degradable and biocompatibility)and the effect of the drugs on release behaviors.The in vitro cytotoxicity test and in vitro degradation showed that the SA-G hydrogel was non-cytotoxic and biodegradable.The in vitro release of Dox from SA-G hydrogel was sustained for more than 20 days without obviously initial burst.indicating that the SA-G hydrogels can acted as drug depot.Released solution from Dox-loaded SA-G hydrogel exhibited remarkable in vitro cytotoxicity activities against S180,A549 and HePG2 cancer cells.The Dox-loaded hydrogel showed an excellent antitumor activity to sarcoma-180 cancer tumor model.These results indicate that this biocompatible and injectable hydrogel systems may be useful as a potential drug delivery of intratumorally chemotherapy for controlled release applications.In the fourth chapter,alginate-gelatin(SA-G),which could be ionic-covalent dual crosslinked with independent tuning of crosslinking degree and gelation rate,was explored as an injectable hydrogel for neural stem cells(NSCs).The storage modulus of SA-G could be tuned(115-356 Pa).SA-G was cytocompatible with NSCs(yielding high viability>96%)and promoted NSC adhesion.SA-G was able to modulate proliferation and migration of NSCs in relation to the crosslinking degree.Moreover,we observed the greatest enhancement in expression of the neuronal marker b-tubulin Ⅲ within the softest hydrogels,which had an elastic modulus comparable to that of brain tissues.Overall,SA-G hydrogels are promising injectable matrices for supporting and influencing NSCs in ways that may be beneficial for nerve tissue regeneration after injuries.