| In this study, the molecularly imprinted polymeric nanospheres (MIPNs) were synthesized by precipitation polymerization using mefenamic acid (MFA), L-methyldopa (LMD) and 10-hydroxycamptothecin (10-HCPT) as templates, methylacrylic acid (MAA) and 4-vinylpyridine (4-VP) as functional monomers as well as ethylene glycol dimethyl acrylate (EGDMA) and divinyl benzene (DVB) as crosslinkers. The synthetic conditions, including the polymerization temperature, kinds and amount of solvents, the molar ratio of functional monomers to crosslinkers, the amount of initiator and other conditions were investigated in detail. The interactions of template molecule and functional monomer, template molecule and the MIPNs as well as the recognition mechanism of MIPNs rebinding drugs were characterized by UV, IR and other means. The particle size, morphology and shape of MIPNs were characterized by means of scanning electron microscopy (SEM) and laser particle size analysis. The adsorption and selectivity of MIPNs were also investigated using the BET assay, Scatchard analysis and quartz crystal microbalance sensors. Finally, the controlled release test was carried out in the mimetic gastric juice (pH=1.5) using LMD-imprinted MIPNs.The synthesis experiments show that the particle size of MIPNs are affected by the polarity of template molecule, polymerization temperature, dosage of initiators, the kinds and amount of solvents, functional monmers and crosslinkers. The rescults indicate that the particle size of MIPNs increase with decreasing polymerization temperature and increase with increasing amount of AIBN. The effects of the polarity of template molecules on the particle size of MIPNs accordingly depend on the polymerization system. The UV scanning results show that there are some certain interactions between the drug templates and functional monomers. Meanwhile, the IR scanning results show that there are some functional groups in the MIPNs, in which could recognize the template molecule.The LMD imprinted nanospheres were characterized by scanning electronic microscopy (SEM), IR analysis, Scatchard analysis and the controlled release test in mimetic gastric juice. The results show that the largest saturated adsorption capacity of MIPNs is 3 times as non-imprinted polymer nanospheres (NIPNs). The controlled release test indicated that the MIPNs release the LMD for 10 h while the one of NIPNs is only for 5 h in the mimetic gastric juice, which indicates that the MIPNs exactly exhibit the delayed effect of drug release. Thus, the resultant MIPNs of LMD look forward to being used as the materials of drug delivery system (DDS). Additionally, the recognition properties of the PQC sensors coated with MIPNs (500 nm) and the molecularly imprinted polymeric microspheres (MIPMs, 5μm) of LMD were also compared. The results show that the MIPNs coated sensor is much better than that of MIPMs coated one due to the former owning the uniform and narrow particle size distribution. The MIPNs coated PQC sensor is found to give a stable and repeatable signal (R. S. D = 8 %, n=5, for a LMD concentration at 0.2 mg/mL), a fast response, a steady signal within about 2 min, a very fast response time compared to the traditional MIPs-coated PQC sensor reported in the literature. The MIPNs-coated PQC sensor has been applied for direct determination of LMD in water, giving a linear working range from 0.1 to 0.6 mg/mL following a regression equation ofΔF= 0.7279+178.63c (R= 0.9951) and a detection limit of 0.02 mg/mL (S/N = 3, n=5). |
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