Handheld fluorometer for in-situ melamine detection via interference synthesis of dsDNA-templated copper nanoparticles

Development of a High-Accuracy, Low-Cost, and Portable Fluorometer with Smartphone Application for the Detection of Urinary Albumin towards the Early Screening of Chronic Kidney and Renal Diseases

This study presents the development of a portable fluorometer with a smartphone application designed to facilitate the early screening of chronic kidney and renal diseases by enabling the sensitive detection of urinary albumin. Utilizing a fluorescence-based aptasensor, the device achieved a linear calibration curve (0.001-1.5 mg/mL) with a linearity of up to 0.98022 and a detection limit of 0.203 µg/mL for human serum albumin (HSA). The analysis of 130 urine samples demonstrated comparable performance between this study's fluorometer, a commercial fluorometer, and the standard automated method. These findings validate the feasibility of the portable fluorometer and aptasensor combination as a reliable instrument for the sensitive and specific measurement of HSA in urine samples. Moreover, the fluorometer's portability offers potential applications in portable point-of-care testing, enhancing its utility in clinical settings for early disease screening.

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.

Portuino-A Novel Portable Low-Cost Arduino-Based Photo- and Fluorimeter

A novel portable low-cost Arduino-controlled photo- and fluorimeter for on-site measurements has been developed. The device uses LEDs as a light source and a phototransistor as a light sensor. The circuit is based on the discharge of a capacitor with the photocurrent from the phototransistor. Validation experiments for absorbance measurements were performed by measuring protein concentration using the Bradford method and measuring phosphate ions in water using a commercial test kit. The emission light of the excited fluorescent dyes rhodamine 6G and calcofluor white was measured to validate the usability of the device as a fluorescence photometer. In all validation experiments, similar correlation coefficients and limit of detection could be achieved with the portable photo- and fluorimeter and a laboratory spectrometer and fluorimeter. Real sample analysis was performed, measuring phosphate concentration in freshwater and concentration of green fluorescent protein, extracted from Escherichia coli.

Low-cost portable bioluminescence detector based on silicon photomultiplier for on-site colony detection

A low-cost, portable bioluminescence detector based on a silicon photomultiplier (SiPM) was developed for on-site colony detection, the main components of which are a low-noise photoelectric signal detection and processing circuit, power management module, and high-performance embedded microcontroller subsystem with peripheral circuits. Balanced chopper modulation and lock-in amplification techniques were adopted to improve the signal-to-noise ratio, and a zero-adjustment technique was used to eliminate the dark current of the SiPM to expand the dynamic range. Using this bioluminescence detector, adenosine triphosphate could be determined in the range of 3.6 × 10^-6 to 3.6 × 10^-11 mol/L, and bacterial colonies could be determined in the range of 1.0 × 10³ to 1.0 × 10⁹ CFU/mL, with a limit of quantitation of 1.0 × 10³ CFU/mL. Satisfactory recoveries and precision were obtained. Actual samples were accurately tested and the data were verified by comparison with those from the national standard method. The manufacturing cost of the bioluminescence detector was only $30, which is only approximately 1% of the price of current commercial instruments. This study provides a tool for rapid on-site detection of bacterial colonies, as well as a new concept for the development of low-cost portable detection equipment.

Allosteric Regulation of DNA Circuits Enables Minimal and Rapid Biosensors of Small Molecules

Detection of environmental pollutants is crucial to safeguard ecological and public health. Here, we report a modular biosensing approach for the detection of contaminants based on the regulation of a minimal DNA signal amplifier and transducer circuit by allosteric transcription factors and their cognate ligands. We leverage the competition between allosteric proteins and an endonuclease to modulate cascade toehold-mediated strand displacement reactions, which are triggered in the presence of specific effectors and sustained by the endonuclease. We built two optical biosensors for the detection of tetracyclines and macrolides in water using repressors TetR and MphR, respectively. We demonstrate that our minimal, fast, and single-step biosensors can successfully detect antibiotics in nanomolar levels and apply them to report the presence of spiked-in antibiotics in water samples in a matter of minutes, suggesting great potential for monitoring of water contaminants.

dsDNA-templated fluorescent copper nanoparticles for the detection of lipopolysaccharides

The introduction of lipopolysaccharides (LPS) or endotoxins that originate from Gram-negative bacteria into the human blood stream induces a severe immune response that can lead to septic shock, and even death. Hence, the accurate detection of LPS is of great importance in the medical and pharmaceutical sectors. This paper proposes a novel label-free fluorescence assay for the detection of LPS utilizing aptamers and the interference synthesis of dsDNA-templated copper nanoparticles. The assay can be performed at room temperature and does not require expensive reagents. The proposed assay has a limit of detection of 0.95 ng ml-1 of LPS, and the fluorescence emission from the copper nanoparticles was found to vary linearly with the concentration of LPS over a wide range (1 to 105 ng ml-1) with R2 = 0.9877.