Synthesis Of In Situ Hydrogels Baesd On Polyaspartamide Derivatives And Their Applications In Drug Delivery And 3D Scaffolds

Over the past several decades,hydrogels have been widely studied as biomaterials especially in the fields of drug carriers and tissue engineering due to their high water content and unique three-dimensional network structure which can resemble the biological tissues.Compared to preformed hydrogels,injectable in situ-forming hydrogels have received increasing attention for their limited surgical invasion and facile incorporation of bioactive moieties.Therapeutic agents can be simply mixed with the precursor solution before gelation and then injected into targeted tissue to fill irregular defect sites.Poly(aspartic acid)has been widely used in the preparation of drug loaded micelles due to its good biocompatibility,biodegradability and non-toxic products,but reports on in situ hydrogel based on poly(aspartic acid)are yet limited.In this study,a series of poly(aspartic acid)-based in situ hydrogels through chemical reactions were prepared and their properties and applications were.studied.In Chapter 1,the advantages and development of in situ hydrogels as biomaterials were systematically introduced,and the choice of materials for preparing hydrogel,cross linking strategies,applications and prospects were reviewed in detail.At last,the advantages of polyaspartic acid as biomedical materials are also described.In Chapter 2,a biodegradable in situ hydrogel was successfully prepared through Michael addition reaction between methacryloylanhydride modified PSI and 3-Mercaptopropionic acid modified PEG.The substitution degree of HS was determined by Ellman’s reagent.The hydrogel morphology was observed by SEM,the gelation time and other physicochemical properties including swelling ratio and viscoelastic property could be easily adjusted through varying the concentrations of PHPA-MA,the substitution degree of MA and the molecular weight of HS-PEG-SH.In the study of drug release behavior,Rh B and BSA were loaded into the hydrogel by simply mixing as two model drugs and the hydrogel displayed controlled release properties.In vitro cytotoxicity of PHPA-MA/PEG hydrogel was evaluated by MTT assay against HeLa cells and it is found that the PHPA-MA/PEG hydrogel had low cytotoxicity to HeLa cells.In conclusion,the in situ PHPA-MA/PEG hydrogels formed through Michael addition reaction had its potential in sustained delivery of protein drugs.In Chapter 3,a biodegradable in situ hydrogel was successfully prepared through Diels-Alder reaction between 2-furfurylamine modified PSI and N-glycinylmaleimide modified PEG.The substitution degree of GMI was determined by high performance liquid chromatography.The hydrogel morphology was observed by SEM,the gelation time and other physicochemical properties could be adjusted through varying the concentrations of PASP-g-FA/AP,the substitution degree of FA,the molecular weight of(GMI)2PEG,temperature and pH.In the experiment of In vitro release PASP-g-FA/AP-PEG hydrogel showed controlled release properties against Rh B.In vitro cytotoxicity test showed that the PASP-g-FA/AP-PEG hydrogel had low cytotoxicity to HeLa cells.Besides,the HeLa cells cultured within the hydrogel presented sustainable proliferation during 3 days in 3D culture study.To sum up,the biodegradable in situ hydrogel formed by AD reaction had its potential in tissue engineering and the future work should focus on the stability of PASP-g-FA/AP-PEG hydrogel under physiological conditions.In Chapter 4,a biodegradable in situ hydrogel was successfully prepared by enzymatic crosslinking of TA modified PSI.The gelation time and the viscoelastic property of PASP-g-TA/AP hydrogel were depended on the concentrations of polymer,HRP and H2O2.The physicochemical properties including hydrogel morphology and swelling ratio could be easily adjusted through varying the concentrations of polymer,HRP and H2O2.Especially in the study of drug release behavior,the hydrophilic small molecule drugs could be loaded into the hydrogel by simply mixing,and the hydrogel displayed good controlled release properties without bursting release.In vitro cytotoxicity test showed that the PASP-g-TA/AP hydrogel had low cytotoxicity to COS-7 cells.In 3D culture study,the COS-7 cells cultured within the hydrogel presented high viability and showed a sustainable proliferation during the culture period of 7 days.Besides,the hydrogels formed in the subcutaneous layer of mouse showed acceptable biocompatibility and biodegradability for up to 30 days.In conclusion,the biodegradable in situ PASP-g-TA/AP hydrogels formed by enzymatically crosslinking offered great potential as a promising biomaterial for localized and long-term sustained delivery of hydrophilic drugs and 3D scaffolds for tissue engineering.In Chapter 5,based on the biodegradable enzyme-mediated in situ hydrogel described in chapter 4,.TiO2@MWCNTs and DOX.HCl were introduced through simply mixed with precursor solution as phototherapy reagent and anti-cancer drug.Besides,PASP-g-TA/AP was further modified with DTPA for visualization by MR imaging.TiO2@MWCNTs were analyzed using TEM,EDS,FT-IR,XRD,Raman spectroscopy and UV-vis.DRS.In the photocatalytic activity experiment,the photoactivity of TiO2@MWCNTs was obviously enhanced under 808 nm infrared laser irradiation compared with TiO2.The gelation time and physicochemical properties including swelling ratio,the viscoelastic property of TiO2@MWCNTs/polymer hydrogel were depended on the concentrations of PASP-g-TA/AP-DTPA,HRP and H2O2.The morphology of the TiO2@MWCNTs/polymer hydrogel was observed by SEM.In the study of drug release behavior,DOX·HCl loaded hydrogel displayed good controlled release properties without bursting release.The result of in vitro MRI test of the hydrogel revealed that the Gd(Ⅲ)-chelated hydrogels displayed strong signals after 48 hours’dialysis and the signal intensity was dependent on the Gd3+ concentration but not crosslink density of hydrogel.In vitro cytotoxicity test showed that TiO2@MWCNTs had obvious cytotoxicity to HeLa cells under 808 nm infrared laser irradiation while the PASP-g-TA/AP-DTPA hydrogel exhibited low cytotoxicity,which means the good biocompatibility of PASP-g-TA/AP-DTPA hydrogel as drug carrier.In 3D culture study,the DOX/TiO2@MWCNTs/polymer hydrogel under 808 um infrared laser irradiation showed highest cytotoxicity and the cell viability decreased to 63%after 72 h incubation.In conclusion,The Gd3+ contained DOX/TiO2@MWCNTs/polymer hydrogel may be used for treatment in photodynamics-chemotherapy and exhibit strong signal on MR imaging for non-invasive monitoring.