Preparation And Properties Of Functional Polymer Hydrogels

Hydrogels are widely used in soft contact lenses,artificial corneas,tissue engineering scaffolds and other ophthalmic materials due to excellent biocompatibility,high permeability.However,some traditional polymer hydrogels have so poor mechanical property that it seriously affect the widespread use of hydrogel.How to design and prepare tough and functional hydrogels to meet the application needs in different fields has attracted wide attention.In view of the poor stability,easy degradation of natural polymer hydrogels and low refractive index of traditional hydrogels,this paper designed and prepared a series of gelatin based hydrogels with epoxy crosslinking or interpenetrating structure and a series of highly refracted polythiamine hydrogels and refraction in order to improve the mechanical properties and functional properties of the hydrogels.1.Preparation and properties of gelatin based hydrogels.Gelatin,which is derived from collagen,has been widely used in clinics for wound dressings,pharmaceuticals and adhesives owing to its biocompatibility,biodegradability and hydrogel characteristics,as well as its formability and cost efficiency.However,the degradation rate of the unmodified gelatin is too fast,and mechanical property is also relatively poor,it is difficult to match the wound healing process.Therefore,it is necessary to modify the gelatin to improve its performance.We were trying to find an economical,convenient and effective method to improve the mechanical property and remain the biocompatibility of gelatin-based hydrogel,such as epoxy-crosslinking or semi-IPN structure froming.(1)Two kinds of novel epoxy-crosslinked gelatin-based hydrogels have been developed.Gelatin is a partially hydrolyzed product of peptides and collagen,there are a large number of amino,carboxyl,hydroxyl,mercapto groups and so on,which can react with epoxy group and result in chemical modification or cross-linking.We used ethylene glycol diglycidyl ether or glycidyl methacrylate as crosslinker instead of toxic glutaraldehyde.After crosslinking,the gelatin-based hydrogels have good stability and biocompatibility.All the as-prepared EGDE and GMA crosslinked gelatin hydrogels are optically clear and transparent with pale yellow color.The equilibrium water content varied from 84.0 to 87.1 wt%for EGDE series and from 75.0 to 87.6 wt%for GMA series gelatin hydrogels,respectively.All the hydrogels exerted minimal cytotoxicity toward human embryonic fibroblast cells and have great potential as wound dressing.(2)A series of novel Gelatin-PHEMA-PVP semi-IPN hydrogels have been developed and used for wound dressing.First,HEMA and NVP monomer were mixed in gelatin solution and form a semi-IPN structure by UV crosslinking and curing,then,gelatin was further crosslinked to get transparent hydrogel.The physical and chemical properties together with cytotoxicity of prepared hydrogels were systemically investigated.It was expected that the introduction of semi-IPN structure and glutaraldehyde crosslinking can improve the hydrolysis stability,degradation rate and mechanical properties of gelatin.The material exerted stable physical and chemical properties and minimal cytotoxicity toward HEK293T cells.Therefore,the Gelatin-PHEMA-PVP semi-IPN hydrogel developed here might be an excellent candidate for wound dressing.2.Preparation and properties of high refractive index polythiamine based hydrogels.Hydrogel have been widely considered as excellent candidates for artificial cornea.But hydrogels in the equilibrium swollen state exhibit poor mechanical properties and low refractive index(RI),based on these shortcomings,greatly limits the application of hydrogels in artificial cornea.Introducing high molar refraction coefficient and smaller molecular volume of the sulfur,halogen elements(except fluorine),aromatic ring,phosphorus atoms,etc.is one effective way of increasing RI of the hydrogel.And incorporating of high RI inorganic nanoparticles such as TiO2,ZnO and ZnS into organic hydrogel matrix is an another,among them ZnS nanoparticles have a high RI(n620nm=2.36)and also have a low light absorption characteristic.(1)We designed a series of high RI four-arm type polythiourethane hydrogels.Due to the sulfur and the four-arm structure,the four-arm type polythiourethane hydrogels have a higher RI.The high RI mainly due to the following two reasons:firstly,smaller molecular size and a similar spherical structure make the branched,like the sulfur,four-arm hydrogels have a high molar refraction.Second,the four-arm type hydrogels have a stronger hydrogen bonding effect,the hydrogels can be more free water into a combination of water,improve the EWC and RI of four-arm type hydrogels.The equilibrium water content(EWC)of the prepared hydrogel were 74.9?90.8 wt%,and the RI of hydrogels in dry and wet states were 1.522?1.552 and 1.420?1.453,respectively.A series of tests showed that the prepared hydrogel nanocomposites have good stability,solvent resistance and biocompatibility?(2)A series of high refractive index(RI)PEG-based polythiourethane hydrogel nanocomposites containing ME-ZnS nanoparticles(NPs)were successfully synthesized via a simple ultraviolet-light-initiated free radical co-polymerization method.The average diameter of the ME-ZnS NPs is?3.5 nm and the NPs are well dispersed and stabilized in the PTUP/PAA hydrogel matrix up to a high content of 30 wt%in the hydrogel nanocomposites.The resulting nanocomposites are clear and transparent and with the increase of the amount of ZnS doping,the RI increases linearly in the dry state and the wet state which can be tuned by varying the ME-ZnS NPs content.For the organic-inorganic hydrogel nanocomposites,the RI increased from 1.537 to 1.643 in the dry state and from 1.425 to 1.490 in the wet state,respectively,with a EWC of 43.1?60.2 wt%.A series of tests showed that the prepared hydrogel nanocomposites have good stability,solvent resistance and biocompatibility.Hence,the high RI PEG-based polythiourethane hydrogel nanocomposites with adjustable RI developed in this work might potentially be a candidate material for artificial corneal implants.