Application Of Surface Molecular-imprinting Technique In The Electrochemical Determination Of Small Drug Molecules

Molecularly imprinted polymer (MIP) is artificially synthesized but popular and inexpensive recognition receptor as nature receptors, such as enzyme, antibody and nucleic acid, etc. It not only possesses the desired selectivity for target molecule as natural receptors, but also presents some advantages, such as easy and controllable preparation and low cost, as well as reusable property. As a result, it has been widely applied as a recognition receptor in various fields including sensor, drug delivery, catalysis and separation, etc. However, the MIP prepared by traditional polymerization still has some disadvantages, such as hydrophobicity and large particle formed, etc. Besides that, the conductivity of the most MIPs is poor for electrochemical sensor, which hinders the electrochemical response signal transmission and makes the sensitivity of electrochemical sensor decrease. In addition, the adsorption and elution of MIP on the electrode surface is repeatedly perform for electrochemical sensor, which consumes much time, leading to low detection efficiency. Based on these issues, we adopt facile surface imprinted methods to contstruct a series of MIPs for electrochemical sensors. The main points are summarized as follows:(1) Au NWs@IL was prepared by directly reducing HAuCl4 with sodium citrate in ionic liquid(IL, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]) aqueous solution. Porous platinum nanoparticles (Pt NPs) were well embedded in Au NWs@IL due to the adhesion of IL to form Pt NPs-Au NWs@IL suspension, which was coated on a carboxyl graphene (COOH-r-GO) modified glassy carbon electrode (GCE) to construct a porous three-dimensional networks modified electrode. Then, MIP was prepared by cyclic voltammetry at the modified electrode, using cefotaxime (CEF) as template and o-phenylenediamine(o-PD) as monomer. The factors concerning this assay strategy were carefully investigated. Under the optimal conditions, the electrochemical sensor offers an excellent response for CEF, the linear response range was 3.9 × 10-9-8.9 x 10-6mol L-1 and the detection limit was 1.0 × 10-10mol L-1. The electrochemical sensor was applied to the determination of CEF in real samples with satisfactory results.(2) A novel molecularly imprinted electrochemical sensor was constructed for the determination of lidocaine, which had porous and three-dimensional nanostructure. Firstly, the dendritic Pt-Pd NPs and porous Pt NWs were prepared by using hexadecylpyridinium chloride (HDPC) as structure-directing agent. Then, the dendritic Pt-Pd NPs were embedded on porous Pt NWs and the resultant mixture was coated on a COOH-r-GO modified GCE. Afterwards, the suspension of aminated-multiwalled carbon nanotubes(NH2-MWCNTs) loaded with dendritic Pt-Pd NPs was dropped on the modified electrode surface to reinforce such porous NWs and enlarge electrode surface area. Subsequently, a MIP film was fabricated by cyclic voltammetry at the modified electrode, using lidocaine as template and o-PD as monomer. The obtained electrochemical sensor offered an excellent response for lidocaine, the linear response range was 5.0 x 10-9-4.8 x 10-6 mol L-1 and the detection limit was 1.0 x 10-10 mol L-1. It also possessed high selectivity and practicability.(3) IL (i.e.3-propyl-l-vinylimidazolium bromide, C3VimBr) was grafted onto multiwalled carbon nanotubes (MWCNTs) surface to form MWCNTs@IL by using an ionic exchange strategy. Then, the resulting MWCNTs@IL was used as monomer to synthesize MWCNTs@MIP for amoxicillin (AMOX). Meanwhile, dendritic Pt-Pd bimetallic NP was prepared by using HDPC and hexamethylenetriamine as synergetic structure-directing agents, and then it was dispersed into single walled carbon nanotubes (SWCNTs) suspension. After that, the hybrid suspension was dropped on a GCE, followed by coating with MWCNTs@MIP. The obtained sensor presented linear response to AMOX in the ranges of 1.0 × 10-9-1.0 × 10-6mol L-1 and 1.0 × 10-6-6.0 × 10-6mol L-1, respectively, and its detection limit was 8.9 ×l0"10mol L-1. This sensor was used to detect AMOX in real honey and milk samples with satisfactory results.(4) Firstly,3-hexadecyl-l-vinylimidazolium chloride (C16VimC1) was synthetized by using 1-vinylimidazole and 1-chlorohexadecane as precursors. Then, C16VImCl was used to improve the dispersion of MWCNTs and as monomer to prepare MIP on MWCNTs surface to obtain MWCNTs@MIP for chloramphenicol (CAP). After that, the obtained MWCNTs@MIP was coated on the mesoporous carbon (CKM-3) and porous grephene (P-r-GO) modified glassy carbon electrode to construct an electrochemical sensor for the determination of CAP. As a result, the electrochemical sensor offered an excellent response for CAP. The linear response ranges were 5.0 × 10-9-5 ×10-7mol-1 and 5.0 × 10-7-4.0 × 10-6mol L-1, respectively, and the detection limit was 1.0×l0-10mol L-1. At the same time, the sensor performed excellent repeatability and selectivity.(6) Au NP was prepared by reducing HAuCl4 with sodium citrate. Then, C3 VimBr was added into Au NPs solution to achieve Au NPs@IL by self-assembling. In succession, the Au NPs@IL was used as monomer to synthesize Au NPs@MIP. After that, the resultant Au NPs@MIP was coated on CKM-3 and P-r-GO modified electrode. Thus, an electrochemical sensor was constructed for the determination of dimetridazole. Experimental conditions were carefully optimized. In this case, the electrochemical sensor presented excellent response for dimetridazole, and its linear ranges were 2.0 x 10-9-0.25 × 10-7mol L-1 and 0.25 × 10-7-3.0 × 10-6mol L-1, respectively, and its detection limit was 5.0 × 10-10mol L-1. The electrochemical sensor was applied to determine dimetridazole in real food samples with satisfactory results.(7) We designed a novel magnetic-controlled glassy carbon electrode(MCGCE), which made the immobilization and removal of magnetic-MIP (mag-MIP) on electrode surface were freely controllable. The mag-MIP was used to recognize and preconcentrate metronidazole (MDZ) from sample solutions to obtain mag-MIP-MDZ. Then, the mag-MIP-MDZ was separated from the solution using an external magnet, rinsed and dispersed in little buffer solution by ultrasound, and part of the suspension was immediately dropped on the r-GO/MCGCE for electrochemical detection. As a result, the recognition, detection and elution were independent Thus, the detection efficiency was enhanced greatly in comparison with the conventional electrochemical MIP serisor. By this way, the linear detection range was 3.2 × 10-8-3.4 × 10-6mol L-1 and the detection limit was 1.2 × 10-9 mol L-1. It was used to detect MDZ with satisfactory results.