Molecular Imprinting-Based Ratiometric Fluorescence Nanosensor and Kit for Rapid and Visual Detection of Folic Acid

Molecular imprinting-based ratiometric fluorescence (MI-RFL) nanosensors receive increasing concerns in various fields such as food security, owing to high selectivity and sensitivity, nondestruction, convenience, visualization, etc. Herein, a ternary-emission MI-RFL nanosensor was facilely constructed by postimprinting mixing (PIM) red-emission molecularly imprinted polymers (r-MIPs) and green MIPs (g-MIPs) for rapid and visual detection of folic acid (FA) in food samples. The two fluorescent MIPs were prepared using a sol–gel surface imprinting one-pot method, with FA as template molecules, SiO2 nanoparticles as supporting materials, 3-mercaptopropionic acid-modified red CdTe quantum dots (CdTe QDs), and glutathione-modified green CdTe QDs as fluorescence sources, respectively. Under the optimal conditions, a good linearity ranging from 0.05 to 50 ppm was attained accompanied by rich color evolution, and limit of detection was down to 0.005 ppm. Then, FA tablets and milk powder were tested, and almost consistent FA contents with that of actual results were found, and recoveries were 89.39–103.43% with relative standard deviations less than 3.37%. Furthermore, the nanosensor-based kit was fabricated to analyze FA tablets by observing color change in 9 min, indicating kit’s high accuracy and practicality. This study can provide a universal point-of-care testing method for on-site monitoring of targets in complicated matrices

Graphene Sensor Arrays for Rapid and Accurate Detection of Pancreatic Cancer Exosomes in Patients’ Blood Plasma Samples

Biosensors based on graphene field effect transistors (GFETs) have the potential to enable the development of point-of-care diagnostic tools for early stage disease detection. However, issues with reproducibility and manufacturing yields of graphene sensors, but also with Debye screening and unwanted detection of nonspecific species, have prevented the wider clinical use of graphene technology. Here, we demonstrate that our wafer-scalable GFETs array platform enables meaningful clinical results. As a case study of high clinical relevance, we demonstrate an accurate and robust portable GFET array biosensor platform for the detection of pancreatic ductal adenocarcinoma (PDAC) in patients’ plasma through specific exosomes (GPC-1 expression) within 45 min. In order to facilitate reproducible detection in blood plasma, we optimized the analytical performance of GFET biosensors via the application of an internal control channel and the development of an optimized test protocol. Based on samples from 18 PDAC patients and 8 healthy controls, the GFET biosensor arrays could accurately discriminate between the two groups while being able to detect early cancer stages including stages 1 and 2. Furthermore, we confirmed the higher expression of GPC-1 and found that the concentration in PDAC plasma was on average more than 1 order of magnitude higher than in healthy samples. We found that these characteristics of GPC-1 cancerous exosomes are responsible for an increase in the number of target exosomes on the surface of graphene, leading to an improved signal response of the GFET biosensors. This GFET biosensor platform holds great promise for the development of an accurate tool for the rapid diagnosis of pancreatic cancer