[Recent advances in applications of fragment/dummy molecularly imprinted polymers]

Recent Advances in Molecularly Imprinted Polymers for Antibiotic Analysis

The abuse and residues of antibiotics have a great impact on the environment and organisms, and their determination has become very important. Due to their low contents, varieties and complex matrices, effective recognition, separation and enrichment are usually required prior to determination. Molecularly imprinted polymers (MIPs), a kind of highly selective polymer prepared via molecular imprinting technology (MIT), are used widely in the analytical detection of antibiotics, as adsorbents of solid-phase extraction (SPE) and as recognition elements of sensors. Herein, recent advances in MIPs for antibiotic residue analysis are reviewed. Firstly, several new preparation techniques of MIPs for detecting antibiotics are briefly introduced, including surface imprinting, nanoimprinting, living/controlled radical polymerization, and multi-template imprinting, multi-functional monomer imprinting and dummy template imprinting. Secondly, several SPE modes based on MIPs are summarized, namely packed SPE, magnetic SPE, dispersive SPE, matrix solid-phase dispersive extraction, solid-phase microextraction, stir-bar sorptive extraction and pipette-tip SPE. Thirdly, the basic principles of MIP-based sensors and three sensing modes, including electrochemical sensing, optical sensing and mass sensing, are also outlined. Fourthly, the research progress on molecularly imprinted SPEs (MISPEs) and MIP-based electrochemical/optical/mass sensors for the detection of various antibiotic residues in environmental and food samples since 2018 are comprehensively reviewed, including sulfonamides, quinolones, β-lactams and so on. Finally, the preparation and application prospects of MIPs for detecting antibiotics are outlined.

The Evolution of Molecular Recognition: From Antibodies to Molecularly Imprinted Polymers (MIPs) as Artificial Counterpart

Molecular recognition is a useful property shared by various molecules, such as antibodies, aptamers and molecularly imprinted polymers (MIPs). It allows these molecules to be potentially involved in many applications including biological and pharmaceutical research, diagnostics, theranostics, therapy and drug delivery. Antibodies, naturally produced by plasma cells, have been exploited for this purpose, but they present noticeable drawbacks, above all production cost and time. Therefore, several research studies for similar applications have been carried out about MIPs and the main studies are reported in this review. MIPs, indeed, are more versatile and cost-effective than conventional antibodies, but the lack of toxicity studies and their scarce use for practical applications, make it that further investigations on this kind of molecules need to be conducted.

共价有机框架分子印迹聚合物复合材料的制备及其用于牛奶中痕量诺氟沙星的选择性富集

诺氟沙星(NFX)作为一种常见的喹诺酮类兽药,被广泛应用于畜牧业中,但其会残留在动物体内,进而对人体健康造成危害,为此有许多国家和组织均对NFX残留量进行了严格限制。为实现对复杂体系中痕量NFX残留的准确与可靠分析,该文制备了一种以共价有机框架(COFs)为载体的分子印迹聚合物(MIPs)。首先,在室温条件下,以金属三氟酸盐为催化剂,对苯二甲醛和3,3'-二氨基联苯为原料快速合成了“席夫碱”型共价有机框架(DP-COF)。然后将NFX、甲基丙烯酸、乙二醇二甲基丙烯酸酯与DP-COF混合,利用偶氮二异丁腈引发聚合反应,即可得到DP-COF@MIPs。整个制备过程条件温和,耗时仅5 h。采用场发射扫描电镜、傅里叶红外光谱、X射线衍射仪、BET比表面积测试仪等对其进行了表征。结果证实成功制备出了DP-COF@MIPs,该材料表面粗糙,拥有介孔范围的孔径(17.79 nm)。通过吸附实验、重复使用性实验对材料性能进行评估,结果表明该材料表观吸附容量高达41.57 mg/g,对NFX具有良好的特异性和选择性识别能力,且重复使用率令人满意。结合HPLC-UV-Vis,实现对牛奶样品中痕量NFX的检测。在3个加标水平下(0.03、0.1、0.3 mg/L),平均回收率为88.8%~92.9%,相对标准偏差小于1.7%。结果表明,该方法可以实现在复杂基质中对兽药残留高选择性、高灵敏度及准确性的检测。

[Advances in solid-phase extraction for bisphenols in environmental samples]

Owing to the strict restrictions on the production and use of bisphenol A (BPA), bisphenol analogs (e. g., bisphenol S and bisphenol F) are gradually coming to use in many fields. BPA and these bisphenol analogs are so-called bisphenols (BPs). BPs as a class of endocrine disrupters are widely distributed in the environment (water, sediments, sludge, and aquatic products). BPs enter the human body through various routes, leading to endocrine disruption, cytotoxicity, genotoxicity, reproductive toxicity, dioxin-like effects, and neurotoxicity. The Canadian government has identified BPs as substances for further scoping/problem formulation. Because of the widespread attention paid to BPs in the environmental field, research is being expanded to cover water, sediment, dust, and biological samples, and other media. Given the significant differences in the complexity and pollution concentration of environmental samples, the development of pretreatment methods that afford high extraction efficiency, good purification selectivity, strong universality, operational simplicity, and high-throughput extraction and purification, are necessary to realize the highly sensitive detection of BPs in environmental media. In recent years, solid-phase extraction (SPE), accelerated solvent extraction (ASE), microwave-assisted extraction (MAE), and dispersion liquid-liquid-microextraction (DLLME) as new pretreatment technologies have gradually replaced the traditional liquid-liquid extraction and Soxhlet extraction. SPE has seen rapid development for the extraction and purification of BPs in various environmental samples, overcoming the bottlenecks related to time, energy, and solvent consumption in traditional methods while extending technical support for the analysis of emerging pollutants. The physicochemical properties, usage, and environmental hazards of typical BPs were briefly reviewed, with emphasis on the application of SPE products, development of new adsorbents, and transformation of the SPE mode. Commercialized SPE products are universally applicable in the field of environmental monitoring, while products suitable for the pretreatment of BPs are limited. The development of new adsorbents mainly focused on their adsorption capacity and selectivity. For example, ordered mesoporous silicon, carbon nanomaterials, metal-organic frameworks, and cyclodextrins have large surface areas, good adsorption performance, and regular pore structures, which improve the adsorption capacity of BPs. Molecularly imprinted polymers (MIPs) and mixed-mode ion-exchange polymers are mainly used to improve the selectivity of BPs in the purification process. In addition, MIPs have high chemical, mechanical, and thermal stabilities, which ensures their widespread application in the extraction, preconcentration, and separation of BPs. A variety of new SPE adsorbents can partially meet the diverse needs for detection. There is a consensus that the current challenges in analytical chemistry include the determination of contaminants at low concentration levels, but at the same time, more efficient and environment-friendly methodologies are required. With the introduction of high-sensitivity instruments in the market, the SPE model is seeing gradual development in terms of miniaturization, automation, and simplification. This in turn has minimized solvent consumption, analysis time, and labor cost, resulting in more efficient and affordable analytical methods such as QuEChERS, solid-phase microextraction (SPME), and magnetic solid-phase extraction (MSPE) to adapt to the new development scenario.