A SERS bioassay based on vancomycin-modified PEI-interlayered nanocomposite and aptamer-functionalized SERS tags for synchronous detection of Acinetobacter baumannii and Klebsiella pneumoniae

Klebsiella pneumoniae (KP) and Acinetobacter baumannii (AB) are two important gram-negative bacteria that cause pneumonia and have been recently known to be associated with food. The rapid detection of these pathogens in food is important to minimize their colonization of the gut and stop new threats of the disease from spreading across the food chain. Herein, a double-edged sword aptasensor was developed for the synchronous detection of KP and AB in food and clinical samples. A highly sensitive, selective, specific, and synchronous detection of the target bacteria was achieved, and the limit of detection (LOD) was 10 cells/mL with a liner range of 50 to 10⁵ cells/mL. The total assay time was 1.5 h. This study does not only provide a new tool for the detection of the target bacteria, but also serves as a promising tool for food safety and pneumonia diagnosis.

Assays to Estimate the Binding Affinity of Aptamers

Aptamers have become coming-of-age molecular recognition elements in both diagnostic and therapeutic applications. Generated by SELEX, the 'quality control' of aptamers, which involves the validation of their binding affinity against their respective targets is pivotal to ascertain their potency prior to use in any downstream assays or applications. Several aptamers have been isolated thus far, however, the usage of inappropriate validation assays renders some of these aptamers dubitable in terms of their binding capabilities. Driven by this need, we provide an up-to-date critical review of the various strategies used to determine the aptamer-target binding affinity with the aim of providing researchers a better comprehension of the different analytical approaches in respect to the molecular properties of aptamers and their intended targets. The techniques reported have been classified as label-based techniques such as fluorescence intensity, fluorescence anisotropy, filter-binding assays, gel shift assays, ELISA; and label-free techniques such as UV-Vis spectroscopy, circular dichroism, isothermal titration calorimetry, native electrospray ionization-mass spectrometry, quartz crystal microbalance, surface plasmon resonance, NECEEM, backscattering interferometry, capillary electrophoresis, HPLC, and nanoparticle aggregation assays. Hybrid strategies combining the characteristics of both categories such as microscale thermophoresis have been also additionally emphasized. The fundamental principles, complexity, benefits, and challenges under each technique are elaborated in detail.

Current and future envision on developing biosensors aided by 2D molybdenum disulfide (MoS2) productions

Two-dimensional (2D) layered nanomaterials have triggered an intensive interest due to the fascinating physiochemical properties with the exceptional physical, optical and electrical characteristics that transpired from the quantum size effect of their ultra-thin structure. Among the family of 2D nanomaterials, molybdenum disulfide (MoS₂) features distinct characteristics related to the existence of direct energy bandgap, which significantly lowers the leakage current and surpasses other 2D materials. In this overview, we expatiate the novel strategies to synthesize MoS₂ that cover techniques such as liquid exfoliation, chemical vapour deposition, mechanical exfoliation, hydrothermal reaction, and Van Der Waal epitaxial growth on the substrate. We extend the discussion on the recent progress in biosensing applications of the produced MoS₂, highlighting the important surface-to-volume of ultrathin MoS₂ structure, which enhances the overall performance of the devices. Further, envisioned the missing piece with the current MoS₂-based biosensors towards developing the future strategies.

Quantitative Peptidomics with Isotopic and Isobaric Tags

In differential peptidomics, peptide profiles are compared between biological samples and the resulting expression levels are correlated to a phenotype of interest. This, in turn, allows us insight into how peptides may affect the phenotype of interest. In quantitative differential peptidomics, both label-based and label-free techniques are often employed. Label-based techniques have several advantages over label-free methods, primarily that labels allow for various samples to be pooled prior to liquid chromatography-mass spectrometry (LC-MS) analysis, reducing between-run variation. Here, we detail a method for performing quantitative peptidomics using stable amine-binding isotopic and isobaric tags.