ABSTRACT
OBJECTIVE:To synthesize 4-hydroxyphenylacetic acid(PHPAA)molecular imprinted polymers(MIPs),and to provide reference for separation and enrichment of PHPAA in urine of cancer patients. METHODS:With PHPAA as template molecule and azobisisobutyronitrile as evocating agent,MIPs was synthesized by precipitation polymerization using 4-vinyl pyridine(4-V),acrylamide(AM),1-vinyl imidazole(1-V)and o-diaminobenzene as functional monomers,ethylene glycol dimethacrylate(EGDMA)and trimethylolpropane trimethacrylate(TRIM)as crosslinking agent. Using scanning electron microscope,infrared spectrum,static adsorption test and molecular recognition performance test used adopted to characterize the structure and performance of MIPs. RESULTS:MIPs1(4-V,EGDMA)microspheres adhered seriously,and MIPs2(AM, EGDMA)microspheres are aggregated. MIPs3(1-V,TRIM),MIPs4(o-diaminobenzene,TRIM)microspheresare were dispersed and had good sphericity. Characteristic absorption peak of PHPAA was not found in infrared spectrum of MIPs. The adsorption capacity of each MIPs was higher than that of blank imprinted polymer without the template molecule,and increased as the increase of template molecular concentration. The adsorption capacity of MIPs3 was significantly higher than that of other MIPs,and its static distribution coefficient(0.14)of PHPAA was higher than that of other structural analogues [PHPA(0.06),TA(0.01)],selective separation factors of PHPAA to PHPA,PHPAA to TA were 2.3,11.5,respectively. CONCLUSIONS:MIPs synthesized with 1-V as functional monomer and TRIM as crosslinking agent has the ability of specific adsorption and selective recognition. It can used as solid phase extractant to separate and enrich low content of PHPAA in the urine of tumor patients.
ABSTRACT
Objective: To prepare quercetin molecularly imprinted polymers (MIPs) by molecular imprinting technique. Methods: This experiment used quercetin as template molecule, acrylamide (AM) as functional monomers, ethylene glycol dimethacrylate (EGDMA) as cross linking agent, and azodiisobutyronitrile (AIBN) as initiator. Using anhydrous ethanol and tetrahydrofuran as pore forming agent, quercetin MIPs were prepared by precipitation polymerization and mass polymerization methods; The optimal proportion between template and functional monomer was chosen by UV and IR; The microstructure of MIPs was investigated by SEM. The adsorption equilibrium time and maximum adsorption of MIPs prepared with two methods were investigated by balance and isothermal adsorption experiment, and the specific adsorption capacity was studied. Results: The experimental research showed that precipitation polymerization method of quercetin MIPs had uniform rules of globular structures. The adsorption kinetics and isothermal adsorption experiment found faster adsorption rate and larger adsorption capacity. Polymer on quercetin had high specificity recognition ability in rutin and quercetin adsorption selective process. Conclusion: Precipitation polymerization of MIPs, with strong selective adsorption, separation and enrichment of chemical components in Chinese medicine flavonoids complex, is a new method of research. At the same time, it also provides reference for chemical composition research of other Chinese materia medica.
ABSTRACT
The objectiveness of this study was to evaluate whether low-viscosity composite can bond effectively to dentin surface without bonding resin. The low-viscosity composites being 50wt% filler content were made by the inclusion of bonding resin of two self-etching systems(Clearfil SE Bond, Unifil Bond) varied with contents as 0, 10, 20, 30, 40, 50wt%. Exposed dentin surfaces of extracted 3rd molars are used. Dentin bond strengths were measured. The tests were carried out with a micro-shear device placed testing machine at a CHS of 1mm/min after a low-viscosity composite was filled into an iris cut from micro tygon tubing with internal diameter approximately 0.8mm and height of 1.0mm. 1. Flexural strength and modulus was increased with the addition of bonding resin. 2. Micro-shear bond strength to dentin was improved according to content of bonding resin irrespective of applying or not bonding resin in bonding procedure, and that of Clearfil SE Bond groups was higher than Unifil Bond. 3. There were no significant difference whether use of each bonding resin in bonding procedure for S-40, S-50, U-50(p>0.05). 4. In SEM examination, resin was well infiltrated into dentin after primed with self-etching primer only for S-50 and U-50 in spite of the formation of thinner hybrid layer. Low viscosity composite including some functional monomer may be used as dentin bonding resin without an intermediary bonding agent. It makes a simplified bonding procedure and foresees the possibility of self-adhesive restorative material.