Study On The Protein Adsorption Performance And Luminescence Mechanism Of Sodium Alginate Nanofiber Membrane

Sodium alginate（SA）,derived from marine brown algae,is a natural anionic polysaccharide with rich sources,low toxicity,nonimmunogenicity,excellent hydrophilicity and biocompatibility.SA nanofiber membranes prepared by electrospinning have attracted increasing attention due to their high surface adhesion,hygroscopicity,good biocompatibility and breathability and wide applications in such areas as filtration,adsorption,biomedicine,injury treatment and optoelectronics.However,due to insufficient chain entanglemnents arising from the obstacles of the chain rigidify and strong electrostatic repulsion among the polyanions,electrospinning of pure alginate from its aqueous solution is still a severe challenge.In this contribution,we have studied the strategies and mechanisms for improving the spinnability of SA,and explored the high-efficiency protein adsorption and luminescence behavior of the prepared SA nanofiber membranes,laying the foundation for its application in the biomedical field.1.we present a strategy of synergistical regulation by adding co-solvent（ethanol）,nonionic surfactants and PEO of high molecular weight into large SA content aqueous solution（98 wt%）,which is higher than any previous reported for the enhanced electrospinning property.Then,pure SA nanofiber membranes can be obtained by washing using water to remove a small amount of PEO and surfactants after electrospining.Using lysozyme as a model protein molecule,we explored the separation and purification performance of SA membranes toward lysozyme.Taking advantages of the nano-scale merits of large surface area and tortuous porous structure,the resultant SA nanofibrous membranes exhibited high adsorption capacity of 1235 mg g^-1 six times higher than current reported maximum value for lysozyme,fast adsorption equilibrium within 10 h and good reversibility toward lysozyme.Moreover,a high dynamic adsorption efficiency of 805 mg g^-1 can be achieved solely driven by gravity of lysozyme solution,which matches well with the demands of the actual protein purification process.2.In order to further explore the potential applications of SA fiber membranes in the biomedical field,the photophysical properties of SA fiber membranes were studied.To gain a thoroughly understanding of the emission mechanism,SA with M/G ratios approaching to 0.69 and 1.53,namely G_rM and GM_r were investigated.Both G_rM and GM_r are practically nonluminescent in dilute solutions（Φ≈0）,but get emissive upon aggregation（Φ≈6.4）.Amazingly,persistent room temperature phosphorescence（RTP）that hardly observed even in aromatic pure organic molecules is also noticed（49.0/30.0ms）.Notably,their emission can be adjusted by Ca²⁺ions due to the high ion-binding selectivity of G-rich regions.Rheological measurements indicate that SA chains are closely overlapped from individuals when the concentration changes from dilute to concentrated regimes,associating with the nonluminescence to strikingly boosted emission,thus further validating the CTE mechanism.