Microchip Cytometry for Multiplexed Single-Cell Protein Detection in a Low-Resource Setting toward Point of Care Diagnosis

Covalent immobilization of beta2 adrenergic receptor through trans-methylation reaction by SNAP-tag and its application in anti-asthmatic compound screening from Raphani Semen

Beta2-adrenergic receptor (β₂-AR) is believed as an attractive target for anti-asthmatic drugs. Its crystal structure and pharmacological activity have been clearly investigated. Yet the number of the approved anti-asthmatic drugs has declined in recent years. This work reports on the preparation of an immobilized β₂-AR column through the specific trans-methylation reaction between SNAP tag and the benzyl-guanine derivative and application in anti-asthmatic compound screening from Raphani Semen. The characterization of the immobilized β₂-AR was performed by scanning electron microscopy (SEM) and receptor-ligand interaction analysis by chromatographic methods. SEM analysis showed that the receptor has been successfully coated on the surface of PEGA amino microspheres. Binding constants of salbutamol and terbutaline calculated from frontal analysis within the temperature range of 10-30 ℃ confirmed the feasibility of the method in a thermodynamic viewpoint. Hydrogen bond was verified as the main driving force for drug-receptor interaction analysis. Sinapine was identified as the potential bioactive compound in Raphani Semen that specifically bind with β₂-AR with a specific binding site of Ser 207. Taking together, the immobilized β₂-AR column is promising in exploring drug-protein interaction analysis and anti-asthmatic drug screening.

The Intriguing Landscape of Single-Cell Protein Analysis

Profiling protein expression at single-cell resolution is essential for fundamental biological research (such as cell differentiation and tumor microenvironmental examination) and clinical precision medicine where only a limited number of primary cells are permitted. With the recent advances in engineering, chemistry, and biology, single-cell protein analysis methods are developed rapidly, which enable high-throughput and multiplexed protein measurements in thousands of individual cells. In combination with single cell RNA sequencing and mass spectrometry, single-cell multi-omics analysis can simultaneously measure multiple modalities including mRNAs, proteins, and metabolites in single cells, and obtain a more comprehensive exploration of cellular signaling processes, such as DNA modifications, chromatin accessibility, protein abundance, and gene perturbation. Here, the recent progress and applications of single-cell protein analysis technologies in the last decade are summarized. Current limitations, challenges, and possible future directions in this field are also discussed.

Modified ELISA for Ultrasensitive Diagnosis

An enzyme-linked immunosorbent assay (ELISA) can be used for quantitative measurement of proteins, and improving the detection sensitivity to the ultrasensitive level would facilitate the diagnosis of various diseases. In the present review article, we first define the term 'ultrasensitive'. We follow this with a survey and discussion of the current literature regarding modified ELISA methods with ultrasensitive detection and their application for diagnosis. Finally, we introduce our own newly devised system for ultrasensitive ELISA combined with thionicotinamide adenine dinucleotide cycling and its application for the diagnosis of infectious diseases and lifestyle-related diseases. The aim of the present article is to expand the application of ultrasensitive ELISAs in the medical and biological fields.

High-Throughput Single-Cell Extracellular Vesicle Secretion Analysis on a Desktop Scanner without Cell Counting

Single-cell EV (extracellular vesicle) secretion analysis is emerging for a better understanding of non-genetic cellular heterogeneity regulating human health and diseases through intercellular mediators. However, the requirements of expensive and bulky instrumentations hinder its widespread use. Herein, by combining gold nanoparticle-enhanced silver staining and the Poisson distribution, we reported the use of a home-use scanner to realize high-throughput single-cell EV secretion analysis without cell counting. We applied the platform to analyze the secretions of different EV phenotypes with the human oral squamous cell carcinoma cell line and primary cells from patients, which generated single-cell results comparable with those of the immunofluorescence approach. Notably, we also realized the quantification of the number of EVs secreted from every single cell using their respective titration curves obtained from population samples, making it possible to directly compare different EV phonotypes in regard to their secretion number, secretion rate, and so forth. The technology introduced here is simple, easy to operate, and of low cost, which make it a potential, easily accessible, and affordable tool for widespread use in both basic and clinical research.

Ultrasimple Single-Cell Detection of Multiple Cytokines by a Nanowell Chip Integrated with Encoded Microarrays

Cytokine production is often regarded as the marker of immune cells' activation status. The spectrum and temporal secretion of cytokines are dramatically varied between cell phenotypes and even within the same phenotype. Multiparameter analysis of individual immune cell's cytokine secretion has always been a challenging and complicated process that needs special facilities in a laboratory setting. Herein, we present an ultrasimple method with high sensitivity and high robustness to quantify cytokine expression at the single-cell resolution. A microchip is developed based on poly(dimethylsiloxane) nanowells on sticky tape, while each nanowell is integrated with a DNA-antibody convertible microarray. Only pipetting is needed for the whole single-cell analysis process. The sensitivity of the assay is evaluated by measuring various concentrations of six recombinant cytokine proteins, which was found comparable to conventional methods. Once single cells are loaded to nanowells and incubated there, a Fluorinert FC-40 is used to isolate nanowells; so, cytokines from those cells are captured by separate microarrays. The rest of the sandwich enzyme-linked immunosorbent assay detection process is also executed simply by pipetting of various reagents. This method is validated by measuring cytokine production from hundreds of single cells. It has simplified a typically sophisticated multiplex single-cell assay into an instrument-free, point-of-detection technology, and thus it may find a broad utility in clinical diagnostics.