ABSTRACT
Foods can be contaminated with foodborne pathogens through a variety of pathways, including water, air and soil. Food safety events caused by foodborne pathogens show a serious impact on human health. However, due to the diversity of foodborne pathogens and the complexity of food matrices, the rapid detection of foodborne pathogens was difficult. The conventional microbial culture and physiological and biochemical identification can hardly meet the need of rapid detection of foodborne pathogens in the field. It is necessary to develop rapid detection technologies for foodborne pathogens. Clustered regularly interspaced short palindromic repeats (CRISPR) and associated protein (Cas) are an adaptive immune systems of prokaryotes with specific recognition and cleavage of nucleic acid sequences, which shows good potential for development of nucleic acid detection and biosensing in the field. According to different forms of application, paper-based analytical devices can be categorized into test paper, lateral flow assay and microfluidic paper-based chips, etc. As a good simplicity and low-cost analytical testing tools, they show good prospects in the field of rapid testing. Therefore, the rapid and sensitive detection of foodborne pathogens can be realized by combining the efficient recognition ability of CRISPR/Cas system and the simplicity of paper-based analytical devices. In this paper, we briefly introduce an overview of the CRISPR/Cas system for nucleic acid detection, and this section focuses on an overview of the features and principles of the class 2 system, including types II, V and VI, which uses a single effector. The application of CRISPR/Cas system based test paper analysis, lateral flow assay and microfluidic paper-based chips for the detection of foodborne pathogens are highlighted in the paper, and finally the advantages, current challenges and future prospects of CRISPR/Cas system in combination with paper-based analytical devices to establish detection methods are discussed.
ABSTRACT
Immunoassays are widely used in medicine, food, environment and other fields due to having the advantages of simpleness, rapidness and accuracy. Combining immunoassays with nanomaterials can improve the performance of immunoassays. Compared with traditional nanomaterials, upconversion nanoparticles (UCNPs) have excellent optical properties such as good photostability, long luminescence lifetime and narrow and tunable emission bands, which can significantly reduce background noise and improve analytical sensitivity when combined with immunoassay. This paper briefly introduces the luminescence mechanism of UCNPs, summarizes the synthesis and surface modification methods of UCNPs. And then 5 UCNPs-based immunoassay techniques, namely, fluorescence resonance energy transfer, inner filter effect, magnetic separation technique, upconversion-linked immunosorbent assay and upconversion immunochromatography, are discussed in detail. These sensing protocols of UCNPs-based immunoassays have been successfully utilized to detect various targets, including small molecules, macromolecules, and pathogens, all of which closely related to food safety, human health, and environmental pollution. Finally, the challenges and prospects of this technique are summarized and prospected. Although the UCNPs immunoassays based on antibodies and antigens have made great progress, most of the research is still in the stage of laboratory, and there is a long way to go to realize its social applications. There is a series of challenges need to be overcome. (1) Designing excellent water soluble and dispersive upconversion nanomaterials is needed. Hydrophilic ligands are bound to smaller upconversion nanoparticles and removing hydrophobic surface ligands are the most widely used methods to improve solubility and dispersity. (2) Multi-detection technology platforms and multi-mode simultaneous detection platforms have great potential, which will improve the efficiency of point of care detection. (3) The researchers also need to focus on some important problems. For examples, the upconversion luminescence efficiency of UCNPs is difficult to maintain, the synthesis method is complex, and the surface modification degree and functionalization are difficult to control.
ABSTRACT
Gatifloxacin (GFX) is a kind of chiral fluoroquinolones compound due to the methyl group at the C-3 position of the piperazine ring[1]. Although the enantiomers of GFX show similar levels of antimicrobial activity and pharmacokinetics[2], the other biological activities (i.e., toxicity or enantioselective recognition to various receptors in vivo) of GFX enantiomers have not yet been studied. With this in mind, we developed a rapid and cost-effective high performance liquid chromatographic (HPLC) separation procedure for GFX enantiomers with a pre-column esterification strategy. With significant enhancement of drug solubility and optimization for chromatographic conditions, the proposed method was scaled up to preparative HPLC to obtain optical active S-(-)- and R-(+)-GFX. The antibacterial activities of GFX enantiomers after preparative separation were further verified by measuring the Minimum Inhibitory Concentration (MIC) values against Escherichia coli ATCC 25922. In addition, the binding selectivity of GFX enantiomers to protein receptor were evaluated by antibody using enzyme-linked immunosorbent assay (ELISA) for the first time.