Confinement-enhanced microalgal individuals biosensing for digital atrazine assay

Probe-free and wash-free strategy for on-site testing of chloramphenicol in food based on differential encodable microspheres separation system

Real-time detection of chloramphenicol (CAP) in food can effectively safeguard food safety. However, traditional chloramphenicol detection methods require large testing equipment, specialized operators and long testing times, therefore portable and rapid CAP detection remain a challenge. Here, we present a differential encodable microspheres separation system based (DEMSs) rapid, portable and accurate detection of CAP. DEMSs utilize specific binding of CAP-Antibody in DEMSs to antigen (CAP) in sample and filtration separation using a customized microfluidic chip for probe-free and wash-free CAP immunoassays. Integrated microscopic optical system and smart counting algorithms based on Hough Circle Transform deployed on a smartphone app enable portable and on-site CAP detection. The experimental results showed that the limit of detection (LoD) of CAP is 24.3 pg/mL and the detection range is 30-50,000 pg/mL. The single testing time is only 16 min. The device offers a novel CAP immunoassay strategy. By replacing antibodies coupled to encoded microspheres in DEMSs, this system is expected to enable the detection of multiple substances in foods.

Portable and Flexible Hydrogel Sensor for On-Site Atrazine Assay on Agricultural Products

There is growing attention focused toward the problems of ecological sustainability and food safety raised from the abuse of herbicides, which underscores the need for the development of a portable and reliable sensor for simple, rapid, and user-friendly on-site analysis of herbicide residues. Herein, a novel multifunctional hydrogel composite is explored to serve as a portable and flexible sensor for the facile and efficient analysis of atrazine (ATZ) residues. The hydrogel electrode is fabricated by doping graphite-phase carbon nitride (g-C3N4) into the aramid nanofiber reinforced poly(vinyl alcohol) hydrogel via a simple solution-casting procedure. Benefiting from the excellent electroactivity and large specific surface area of the solid nanoscale component, the prepared hydrogel sensor is capable of simple, rapid, and sensitive detection of ATZ with a detection limit down to 0.002 ng/mL and per test time less than 1 min. After combination with a smartphone-controlled portable electrochemical analyzer, the flexible sensor exhibited satisfactory analytical performance for the ATZ assay. We further demonstrated the applications of the sensor in the evaluation of the ATZ residues in real water and soil samples as well as the user-friendly on-site point-of-need detection of ATZ residues on various agricultural products. We envision that this flexible and portable sensor will open a new avenue on the development of next-generation analytical tools for herbicide monitoring in the environment and agricultural products.

Gradient Hydrogels Spatially Trapped Optical Cell Profiling for Quantitative Blood Cellular Osmotic Analysis

The quantitative exploration of cellular osmotic responses and a thorough analysis of osmotic pressure-responsive cellular behaviors are poised to offer novel clinical insights into current research. This underscores a paradigm shift in the long-standing approach of colorimetric measurements triggered by red cell lysis. In this study, we engineered a purpose-driven optofluidic platform to facilitate the goal. Specifically, creating photocurable hydrogel traps surmounts a persistent challenge─optical signal interference from fluid disturbances. This achievement ensures a stable spatial phase of cells and the acquisition of optical signals for accurate osmotic response analysis at the single-cell level. Leveraging a multigradient microfluidic system, we constructed gradient osmotic hydrogel traps and developed an imaging recognition algorithm, empowering comprehensive analysis of cellular behaviors. Notably, this system has successfully and precisely analyzed individual and clustered cellular responses within the osmotic dimension. Prospective clinical testing has further substantiated its feasibility and performance in that it demonstrates an accuracy of 92% in discriminating complete hemolysis values (n = 25) and 100% in identifying initial hemolysis values (n = 25). Foreseeably, this strategy should promise to advance osmotic pressure-related cellular response analysis, benefiting further investigation and diagnosis of related blood diseases, blood quality, drug development, etc.