胶体金核壳型沙丁胺醇分子印迹聚合物的光谱特征分析

为了解决饲料和动物产品中沙丁胺醇残留现场快速检测的难题,开发以分子印迹技术为基础的快速检测沙丁胺醇的新方法,使用沙丁胺醇做为模板分子,甲基丙烯酸(methacrylic acid,MA)作为功能单体,以本体聚合法为基础合成常规SAL分子印迹聚合物(molecularly imprinted polymer,MIPs)和非分子印迹聚合物(non imprinted polymer NIPs)。在此基础上,以胶体金粒子为引发核,制备出新型的核壳型沙丁胺醇MIPs。应用紫外吸收光谱(UV spectra)、傅里叶红外光谱(IR spectra)和拉曼光谱(Raman spectru)、扫描电镜(scanning electron microscopy,SEM)等技术手段获得两种印迹物及各种相关化合物的光谱图、电镜图等表征图像。由实验结果可知,SAL和MA上的羧基形成稳定又容易洗脱的1∶1型氢键配合物,化学结合常数K=-0.245×10~6 L^2·mol^(-2)。与MA的—COOH中氢原子形成氢键的可能结合位点是SAL C—O中的氧原子。MIPs与MA中—OH的吸收峰比较可知,前者明显红移;证明SAL作为模板分子与MA之间发生特定结合。未洗脱MIPs的C—O的伸缩振动产生的吸收峰红移;即能量损失明显,可知MA中—COOH的氢原子如果要生成氢键,可能的结合位点就是SAL分子内C—O中的氧原子。MIPs和NIPs中C—C,C—O,—OH等吸收明显的官能团峰型大致相同。将MIPs洗脱掉作为模板分子的SAL后,留下了含有特殊且确定结构官能团化学及空间构成均与SAL高度匹配的空穴,可与待测液中的目标检测分子SAL发生特异性识别和专一结合作用。而胶体金核壳型MIPs与常规MIPs相比,除具有以上相同特点外,其表面更加松散,表面孔穴明显增多。由此增加了吸附目标分子的有效面积,具有更优良的吸附性能。这两种印迹物的合成及光谱特征分析为建立基于分子印迹技术的快速检测SAL新方法奠定了理论和实践基础。

分子印迹聚合物及其在固相萃取中的应用

综述了分子印迹聚合物(MIPs)的制备原理、方法及其在固相萃取中的应用现状,特别分析了聚合物制备条件和工作条件对MIPs识别性能的影响,最后提出了改进MIPs性能需要进一步研究的方向。

基于可逆加成-断裂链转移聚合的孕酮分子印迹膜制备与检测

基于可逆加成-断裂链转移(reversible addition fragmentation chain transfer,RAFT)聚合原理,通过紫外光引发方式,以2-(十二烷基硫代碳酸酯基)-2-甲基丙烯酸(DDMAT)作为唯一的控制试剂,在DDMAT修饰的金膜表面合成了针对孕酮分子的分子印迹物聚合物(molecularly imprinted polymers,MIPs)薄膜,并作为表面等离子体共振(SPR)传感器的识别单元.通过现场原位监控MIPs薄膜生长动力学,使其厚度得到有效控制.聚合动力学研究表明,DDMAT在紫外光引发聚合过程中起到引发剂和链转移试剂双重作用.对MIPs薄膜表面进行接触角、红外光谱、扫面电子显微镜表征,结果表明通过紫外光引发的方式能够有效地将MIPs薄膜接枝到DDMAT修饰的金膜表面,且MIPs薄膜厚度均一,其表面布满的纳米尺寸孔径的孔穴,为识别孕酮分子提供了通道.在pH 7.4的PBS缓冲液中对浓度范围10^(-12)~10^(-7) mol/L的孕酮样品进行检测,结果表明该MIPs薄膜修饰的传感器对孕酮分子具有较高的灵敏度,检测限为3.24×10^(-13) mol/L(信噪比,S/N=3),且具有良好的选择识别性能和重复使用性能;稳定性实验结果显示,MIPs薄膜修饰的SPR传感器芯片在N_2气保护下,室温存储30 d对低浓度的孕酮分子样品仍具有良好的信号响应.实际水体及人工尿液中测得孕酮回收率为92.9%~96.5%,说明此传感器可用于实际样品测定.

Synthesis and Solid Phase Extraction Performance Study of NNAL-specific Molecularly Imprinted Polymers Using Dummy Templates

Dummy molecularly imprinted polymers （DMIPs） for 4-（methylnitrosamino）-1-（3-pyridyl）-1-butanol （NNAL） were produced using three structural analogues as dummy template molecules. The chosen analogues were 4-（acetymethylamino）-1-（3-pyridyl）-butanol, 4- （methylamino）-1-（3-pyridyl）-1-butanol, and 1-（3-pyridyl）-1,4,-butanediol. The molecular recognition characteristics of the produced polymers were evaluated by X-ray photoelec- tron spectroscopy （XPS） and Fourier transform infrared spectroscopy （FT-IR）. Interactions between NNAL and methacrylic acid should be cooperative hydrogen bonds while the ni- trogen atom of the pyridine ring and the oxygen atom of the nitroso group in NNAL are two of the hydrogen-bond acceptors. It was further demonstrated that DMIP synthesized by 4-（acetymethylamino）-1-（3-pyridyl）-butanol had the best binding performance by XPS and FT-IR. Then dummy molecularly imprinted solid phase extraction （DMISPE） was developed for the determination of the analyte using the hit polymer as the sorbing material. Under optimal conditions, the recovery of NNAL dissolved in standard solution reached 93%. And the investigated polymer exhibited much higher binding of NNAL when nicotine was acted as the competitive molecule. Also the proposed method was applied to the measurement of NNAL spiked in blank urine samples with recoveries ranging from 87.2% to 101.2%.

Molecularly imprinted polymer based on upconversion nanoparticles for highly selective and sensitive determination of Ochratoxin A

A novel molecularly imprinted polymer (MIP) based on upconversion nanoparticles (UCNPs) was successfully synthesized for determination of Ochratoxin A (OTA). The MIP was developed on the silica-coated UCNPs using N-(1-hydroxy-2-naphthoyl amido)-(L)-phenylalanine (HNA-Phe) as the alternative template. The final composite combined the advantages of the high selectivity of MIP with the high fluorescence intensity of UCNPs which was selective and sensitive to OTA. Under the optimal condition, the fluorescence intensity of UCNPs@SiO2@MIP decreases linearly when the concentration of OTA increases from 0.05 to 1.0 mg/L. The detection limit of OTA with the method was 0.031 mg/L. At three spiked concentration levels (50, 100 and 200 μg/kg), the recovery ranges of OTA in corn, rice and feed are 88.0%–91.6%, 80.2%–91.6% and 89.2%–90.4%, respectively.

Molecularly Imprinted Polymers for Selective Extraction of Crystal Violet from Natural Seawater coupled with HighPerformance Liquid Chromatographic Determination

Molecularly imprinted polymers （MIPs） were prepared by the bulk polymerization using crystal violet as the template molecule, and the methacrylic acid and ethylene glycol dimetheacrylate as functional monomer and cross-linker, respectively. Sys- tematic investigations of synthetic conditions were conducted. The surface morphology and recognition mechanism of the obtained polymers were studied using scanning electron microscope and spectrophotometric analysis. MIPs showed high atTmity to template molecule and were successfully applied as special solid-phase extraction sorbent for selective extraction of crystal violet from natural seawater. An off-line molecularly imprinted solid-phase extraction （MISPE） method followed by high-performance liquid chroma- tography with diodearray detection for the analysis of crystal violet was also established. MISPE columns have good recoveries for crystal violet standard solutions and good linearity was obtained over the concentration range of 0-200 ~tg L-1 （R2 〉 0.99）. Finally, two natural seawater samples were investigated. The recoveries of spiked seawater on the MISPE columns were from 44.47% to 62.34%, the relative standard deviation （n=3） being in the range of 2.89%-5.96%.

Molecular Imprinting Technique and Its Application in Food Industry

As a novel technique, molecular imprinting technique are attracting more and more attention in recent years, due to its specific recognition function to im- printed molecules. This paper firstly introduced this technique from its history, princi- ple, classification and methods, and then reviewed the application in food industry, and presented possible future research orientations.

Development of Uric Acid Sensor Based on Molecularly Imprinted Polymetl^acrylic Acid-Modified Hanging Mercury Drop Electrode

Development of uric acid sensor based on molecularly imprinted polymer （MIP） was studi ed. The sensor was developed by coating the imprinted polymethacrylic acid on the surface of a hanging mercury drop ele, ctrode （HMDE） at -1 V （vs. Ag/AgCI） during 60 s. Uric acid was accumulated on the modified electrode at -1 V （vs. Ag/AgC1） during 60 s in acetate buffer pH = 5 and stripped at scan rate of 59 mV/s. Oxidation of uric acid on the surface of modified electrode is irreversible through the diffusion controlled process and polymethacrylic acid is a non-electrical conducting polymer. The current signal obtained from Ehe analysis of uric acid by using HMDE is higher than that of the HMD-palymethacrylic acid （polyMAA）, HMD-MIP and HMD-non imprinted polymer （NIP） electrode. The HMD-MIP has demonstrated its performance as a sensitive voltammetric sensor for uric acid. The modified electrode has been tested for the determination of uric acid in the serum sample with recovery percentage of 95.7% （n = 2）. The limit of detection obtained was 6.0 x 10-10 M.

Molecular imprinting and cladding produces antibody mimics with significantly improved affinity and specificity

Molecularly imprinted polymers(MIPs),as important mimics of antibodies,are chemically synthesized by polymerization in the presence of a target compound.MIPs have found wide applications in important fileds.However,the current molecular imprinting technology suffers from a dilemma;there is often a compromise between the best affinity and the best specificity for MIPs prepared under optimized condi-tions.Herein,we proposed a new strategy called molecular imprinting and cladding(MIC)to solve this issue.The principle is straightforward;after molecular imprinting,a chemically inert cladding thinlayer is generated to precisely cover non-imprinted area.We further proposed a special MIC approach for con-trollably engineering protein binders.The prepared cladded MIPs(cMIPs)exhibited significantly improved affinity and specificity.The general applicability of the proposed strategy and method was ver-ified by engineering of cMIPs for the recognition of a variety of different proteins.The feasibility of cMIPs for real applications was demonstrated by fluorescence imaging of cancer cells against normal cells and immunoassay of C-peptide in human urine.This study opened up a new avenue for controllably engi-neering protein-specific antibody mimics with excellent recognition properties,holding great prospective in important applications such as disease diagnosis and nanomedicine.

Molecularly imprinted polymers as the extracted sorbents of clenbuterol ahead of liquid chromatographic determination

A pre-treatment methodology for clenbuterol hydrochloride （CLEN） isolation and enrichment in a complex matrix environment was developed through exploiting molecularly imprinted polymers （MIPs）. CLEN-imprinted pol- ymers were synthesized by the combined use of ally-β-cyclodextrin （ally-13-CD） and methacrylic acid （MAA）, allyl-β-CD and acrylonitrile （AN）, and allyl-β-CD and methyl methacrylate （MMA） as the binary functional monomers. MAA-linked allyl-β-CD MIPs （M-MAA） were characterized by Fourier transform-infrared （FT-IR） spectroscopy and a scanning electron microscope （SEM）. Based upon the results, M-MAA polymers generally proved to be an excellent selective extraction compared to its references： AN-linked allyl-β-CD MIPs （M-AN） and MMA-linked allyl-β-CD MIPs （M-MMA）. M-MAA polymers were eventually chosen to run through a molecularly imprinted solid-phase extraction （MISPE） micro-column to enrich CLEN residues spiked in pig livers. A high recovery was achieved, ranging from 91.03% to 96.76% with relative standard deviation （RSD） ≤4.45%.

Molecularly imprinted polymer for pre-concentration of esculetin from tobacco followed by the UPLC analysis

Molecularly imprinted polymers(MIPs)for solid-phase extraction and pre-concentration of esculetin have been successfully prepared by the bulk polymerization method using esculetin as a template molecule.Polymers of varying composition were prepared using different monomers(4-vinylpyridine,methacrylic acid,and acrylamide),ethylene glycol dimethacrylate as the cross-linker,2,2-azobis(2-methylpropinitrile)as the initiator,and different porogen solvents(ethanol,acetone/methanol,and acetonitrile).The best polymer was obtained when 4-vinylpyridine was used as the monomer and acetone/methanol(3:2)as the porogen solvent,whereas the template:-monomer:-cross-linker ratio was 1:4:20.The imprinting factor of the selected MIPs for esculetin was 3.77.The polymers were evaluated according to their selective recognition properties for esculetin and structurally-related compounds(esculin,scopoletin,coumarin,and 7-methoxycoumarin).Chemical and morphological characterizations of the polymers were investigated by FTIR and scanning electron microscope,which confirmed a high degree of polymerization.Surface area,pore volume,and pore size of the polymer were investigated by Brunauer-Emmett-Teller analysis.MIPs were also successfully used as solid-phase adsorbent materials for the extraction of esculetin from tobacco leaves.Esculetin contents in dried tobacco leaves were found to be(9.27±0.17)μg g-1.

Surface-imprinted polymers in microfluidic devices

Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices.