L-Trp Imprinted Crystalline Calcium Alginate Hydrogel

There existed many shortcomings in calcium alginate hydrogel as molecular imprinting material such as the poor mechanical strength and unstable imprinting structure due to swelling. Besides the traditionary covalent crosslinking consumes specific sites and destruct the template molecule leading to the decline of recognition during elution process. Therefore, this project is proposed to construct the short-range ordered crystalline regions providing physical crosslinking site to control swelling degree and stabilize the imprinting structure. Swelling controlled urethane acrylate modified calcium alginate hydrogel was prepared by free radical polymerization. Then L-Trp imprinted crystalline microspheres with high adsorption capacity, selectivity and reutilize were prepared.Firstly, monocapped urethane acrylate monomer (OUA) with a vinyl group was sysnthesized with isophorone diisocyanate (IPDI), hydroxyethyl methacrylate (HEMA) and diglycol (DEG). The monomer structure was verified by the reaction kinetics of IPDI and HEMA, infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance spectroscopy (13C NMR).Secondly, crystalline calcium alginate gel beads were prepared by free radical initiator with azodiisobutyronitrile (AIBN) as initiator, OUA as monomer and dimethylformamide (DMF) as solvent. Modified products were measured by FTIR, 13C NMR, scanning electron microscope (SEM), thermodynamic analysis (TGA) and X-ray diffraction (XRD). The effects of reaction temperature, reaction time, initiator concentration and monomer concentration on degree of swelling gel microspheres were investigated. Besides, the pH sensibility and sodium salt susceptibility of gel microspheres were inspected. Research showed that urethane acrylate monomer could significantly affect swelling degree, crystallinity and thermal stability of gel microsphers.Next, monocapped urethane acrylate monomer (WUA) was sysnthesized with IPDI, HEMA and dimethylolpropionic acid (DMPA). Crystalline calcium alginate gel microspheres were prepared by free radical initiation with K2S2O8/Na2SO3 as initiator, WUA as monomer and CaCl2 as crosslinker. Modified products were characterized by FTIR,13C NMR, SEM, TGA, XRD and tensile machine. Many influencing factors on the swelling degree of gel microspheres were regarded including reaction temperature, reaction time, initiator concentration, monomer concentration, calcium chloride concentration and the mass ratio of re-dox. Besides, the pH sensibility and sodium salt susceptibility of gel microspheres were inspected. Research showed that the modified calcium alginate was enhanced in many aspects such as swelling degree, thermal stability, mechanical properties and swelling degree.Last, L-tryptophan imprinted modified calcium alginate hydrogel was prepared with L-tryptophan as template molecule, acetone and pH=7.2 Tris-HCl buffer system as eluate. The infrared spectroscopy confirmed the interaction between WUA and L-tryptophan molecules. Microspheres were prepared with 0.0385 mol/L WUA, 2mmol/L L-Trp and 2% CaCl2, the adsorption capacity and imprinting factor of which were 181.22 μmol/g and 4.91, respectively. According to the study of recognition, modified gel microspheres have good selectivity for template, the separation factor (5.74) of which was significantly higher than that of non-imprinted microspheres (1.17).