Rapid colorimetric analysis of multiple microRNAs using encoded hydrogel microparticles

Real-Time Signal Analysis with Wider Dynamic Range and Enhanced Sensitivity in Multiplex Colorimetric Immunoassays Using Encoded Hydrogel Microparticles

The simultaneous quantification of multiple proteins is crucial for accurate medical diagnostics. A promising technology, the multiplex colorimetric immunoassay using encoded hydrogel microparticles, has garnered attention, due to its simplicity and multiplex capabilities. However, it encounters challenges related to its dynamic range, as it relies solely on the colorimetric signal analysis of encoded hydrogel microparticles at the specific time point (i.e., end-point analysis). This necessitates the precise determination of the optimal time point for the termination of the colorimetric reaction. In this study, we introduce real-time signal analysis to quantify proteins by observing the continuous colorimetric signal change within the encoded hydrogel microparticles. Real-time signal analysis measures the "slope", the rate of the colorimetric signal generation, by focusing on the kinetics of the accumulation of colorimetric products instead of the colorimetric signal that appears at the end point. By developing a deep learning-based automatic analysis program that automatically reads the code of the graphically encoded hydrogel microparticles and obtains the slope by continuously tracking the colorimetric signal, we achieved high accuracy and high throughput analysis. This technology has secured a dynamic range more than twice as wide as that of the conventional end-point signal analysis, simultaneously achieving a sensitivity that is 4-10 times higher. Finally, as a demonstration of application, we performed multiplex colorimetric immunoassays using real-time signal analysis covering a wide concentration range of protein targets associated with pre-eclampsia.

Dual amplification-based ultrasensitive and highly selective colorimetric detection of miRNA

In this study, we combined a Pradeep Kumar (PK)-probe with a ligation-transcription-ramified RCA (LTR) dual-amplification system for the isothermal colorimetric detection of miRNA 25-3P, where the PK-probe transformed from its pink color to colorless in the presence of the amplification byproduct pyrophosphate (PPi), thereby allowing the simple naked-eye qualitative detection of the miRNA. Through this double-amplification strategy, the limit of detection reached as low as 91.4 aM-quite extraordinary sensitivity for a colorimetric miRNA detection system based on absorbance readings. Our detection system also operated with high specificity, the result of using two different target-selective ligation steps (linear DNA ligation and circular DNA ligation) mediated by SplintR ligase, and so could discriminate single-mismatched from perfectly matched target sequences. We suspect that this ultrasensitive and selective PK-probe/LTR dual-amplification system should be a great colorimetric diagnostic for the detection of any miRNA with high efficiency.

Advances in Point-of-Care Testing of microRNAs Based on Portable Instruments and Visual Detection

MicroRNAs (miRNAs) are a class of small noncoding RNAs that are approximately 22 nt in length and regulate gene expression post-transcriptionally. miRNAs play a vital role in both physiological and pathological processes and are regarded as promising biomarkers for cancer, cardiovascular diseases, neurodegenerative diseases, and so on. Accurate detection of miRNA expression level in clinical samples is important for miRNA-guided diagnostics. However, the common miRNA detection approaches like RNA sequencing, qRT-PCR, and miRNA microarray are performed in a professional laboratory with complex intermediate steps and are time-consuming and costly, challenging the miRNA-guided diagnostics. Hence, sensitive, highly specific, rapid, and easy-to-use detection of miRNAs is crucial for clinical diagnosis based on miRNAs. With the advantages of being specific, sensitive, efficient, cost-saving, and easy to operate, point-of-care testing (POCT) has been widely used in the detection of miRNAs. For the first time, we mainly focus on summarizing the research progress in POCT of miRNAs based on portable instruments and visual readout methods. As widely available pocket-size portable instruments and visual detection play important roles in POCT, we provide an all-sided discussion of the principles of these methods and their main limitations and challenges, in order to provide a guide for the development of more accurate, specific, and sensitive POCT methods for miRNA detection.