Fabrication Of PNIPAm Based Hydrogel Composite Membrane And Study On High-throughput Adsorption Of Protein

With the rapid development of molecular biology,the separation and purification of proteins has important applications in molecular diagnostics,drug manufacturing and delivery,and life sciences.Traditional protein separation methods generally have shortcomings such as complex operation,high energy consumption,and protein volatility and inactivation.This makes it impossible to purify trace amounts of protein while maintaining the integrity of protein activity and molecular structure,which restricts research on pathogenesis of related diseases,vaccine development,and clinical treatment.Therefore,it is urgent to explore new separation materials with good biocompatibility and high-throughput adsorption of proteins.Hydrogels are a class of gels with a three-dimensional（3D）network structure that can swell in water without dissolving.It is similar in structure to human tissue and acts similar to the extracellular matrix,and can reduce the collision with surrounding tissues after swelling.Hydrogel materials have good biocompatibility and tunable network structure,which have attracted extensive attention in regulating the adsorption and separation of proteins.Therefore,in this paper,N-isopropylacrylamide（NIPAM）with temperature-sensitive properties is used as the monomer and polyethylene glycol diacrylate（PEGDA）as the cross-linking agent,2-Hydroxy-4’-（2-hydroxyethoxy）-2-methylpropiophenone（Irgacure2959）was used as photoinitiator,and the hydrogel composite membrane PEGDA-PNIPAm was obtained by cross-linking reaction under UV light.Through characterization,the hydrogel was found to have a low critical solution temperature（LCST）of 32.2℃,at which point the hydrogel network undergoes a“swell-shrink”transition.Below the LCST,the hydrophilic groups in the hydrogel form hydrogen bonds with water molecules,the molecular chain stretches,and the gel swells.On the contrary,the interaction between the isopropyl groups of hydrophobic groups is enhanced,the hydrogen bond is weakened,the molecular chain changes from an extended chain to a sphere,and the network shrinks.At the same time,it was found by tensile test that the hydrogel composite membrane material has good mechanical properties and can be reused under certain conditions.The hydrogel composite membrane was used to adsorb bovine serum protein（BSA）.The study found that at p H=4.8,the PEGDA-PNIPAm hydrogel composite membrane had the best adsorption effect on BSA at32℃,and the maximum adsorption amount reached 457.0 mg g^-1.Chitosan（CS）was added to the above hydrogel prepolymer.CS-PNIPAm hydrogel composite membranes were prepared by photo-initiated polymerization with CS and PNIPAm as monomers and PEGDA as cross-linking agent.CS contains a large number of hydrophilic groups such as hydroxyl and amino groups,which changes the hydrophilic/hydrophobic balance in PNIPAm,making the CS-PNIPAm hydrogel composite membrane with a higher LCST=57.5℃.In the general temperature range（10～40℃）,it is not sensitive to temperature and has structural stability.In the study of adsorbing BSA,it was found that in an acidic environment,the-NH₂protonation in CS was converted to-NH₃⁺,the molecular chains in CS-PNIPAm stretch and the hydrogel network swells,which is beneficial for protein adsorption.Then,the effect of temperature on the adsorption of BSA to CS-PNIPAm was explored,and the results showed that,in a wide experimental operating temperature range（10～37℃）,it can adsorb proteins with high flux,and the average adsorption capacity reaches296.4±50 mg g^-1.On the basis of protein adsorption by PNIPAm hydrogel,gallium（Ga）ions were further added to the hydrogel to prepare a gallium-containing hydrogel dressing（Ga-PNIPAm）.The study found that the Ga-PNIPAm hydrogel dressing has excellent mechanical properties and elasticity,and the swelling rate can reach 537%.The dressing can release gallium ions slowly,and can release completely within 60 hours,and it shows excellent antibacterial effect on Staphylococcus aureus for a long time.The hydrogel provides new ideas and research directions for the development of wound dressings.