A simultaneous strategy with multiple-signal amplification and self-calibration for ultrasensitive assay of miRNA-21 based on 3D MNPs-IL-rGO-AuNPs.

MicroRNA-21 (miRNA-21) is a significant biomarker for the development and progression of diverse cancers but is present in relatively low concentrations. Detecting such low-abundance molecules accurately can be challenging, especially in early-stage cancers where the concentration may be even lower. Herein, a self-calibration biosensing platform based on 3D novel MNPs-IL-rGO-AuNPs nanocomposites was successfully established for the ultrasensitive detection of miRNA-21. Duplex-specific nuclease (DSN) was introduced to recognize perfectly matched duplexes and trigger target recycling, enhancing the specificity and sensitivity of the biosensor. DSN-assisted target recycling, in conjunction with magnetic separation enrichment and high-performance MNPs-IL-rGO-AuNPs, collectively formed a multiple-signal amplification strategy. The obtained biosensor could output dual signals in both electrochemical and fluorescent modes, enabling self-correcting detection to enhance the accuracy. The obtained dual-mode biosensor prepared exhibited a wide detection range from 5 fM to 100 nM with a remarkably low LOD of 1.601 fM. It accomplished the sensitive evaluation of miRNA-21 in total RNA extracted from various human cancer cell lines and normal cell lines. Additionally, the greatly satisfactory outcomes in the analysis of human serum samples suggested that the proposed biosensor was a powerful screening candidate in early clinical diagnosis of cancer.

All-in-one calcium nanoflowers for dual outputs biosensor: A simultaneous strategy for depression drug evaluation and non-invasive stress assessment.

Although enzyme-based signal amplification has been well developed for biosensors, their application in low-abundance biomarker under complicated conditions detection remains challenge. Cortisol is a steroid hormone and a quantitative evaluation of cortisol can objectively assess stress and depression. However, various factors can induce slight cortisol changes in body fluids, and this in turn sets a strict requirement for bedside testing of cortisol for evaluation of stress. Herein, all-in-one calcium nanoflowers (CaHPO4-AM-HRP-SA NFs) integrated with horseradish peroxidase (HRP), α-amylase (α-AM), and streptavidin (SA) have been synthesized to develop a simple but powerful biosensor for cortisol detection. High specific surface area and allosteric modulator provided by the hybrid nanoflowers as inherent advantages significantly boosted the catalytical ability and stability compared with the free enzymes. CaHPO4-AM-HRP-SA NFs also endowed the sensor with two output signals of one sample, leading the as-prepared sensor to realize self-calibration detection. Aside from using a traditional microplate reader to measure the signal, it could also be read out by a handheld blood glucose meter and a mobile phone. The sensor exhibited attractive simplicity and sensitivity with a low LOD of 98.5 pg mL-1. It accomplished the sensitive evaluation of cortisol in rat serum and assessed the antidepressant effects of different medications. The non-invasive and reliable cortisol detection is also achieved in human urine and saliva samples. Overall, we have demonstrated that the sensor can be deployed as a promising platform to evaluate drug efficiency and monitor stress in a simple and non-invasive manner.

Multifunctional amino acids empowering bifunctional biosensing platform for depression study.

Poor availability of objective approaches hinders effective diagnosis and treatment for depression. Biosensors provide a promising platform for the development of quantitative and practical methods for disease detection, as well as for drug discovery. Here, we developed an electrochemical biosensor has been established with the ability to simply and accurately detect the trace glucocorticoid receptor alpha (GRα), as a key biomarker of depression, in both hippocampus and blood cells. The integration of amino-ion graphene oxide (IL-rGO) and amino acid-coated gold nanoparticles (AA-AuNPs) via green synthesis remarkably magnifies the electrochemical signals, where amino acids play multiple roles as reducing agents, stabilizers, and bridging agents. After the optimization among AA-AuNPs@IL-rGO nanocomposites based on five typical amino acids, a biosensing surface has been constructed to implement analysis in real samples as a bifunctional platform. The obtained biosensor exhibited a remarkably low limit of detection (0.283 pg mL-1) and could thus sensitively identify the GRα differences in healthy and depressive rats with and without fluoxetine. The electrochemical biosensor developed herein was not only outstandingly sensitive but also simple to use and labor-saving, making it a promising all-in-one platform for depression diagnosis and drug discovery.

Electrochemical sensor based on magnetic nanohybrids of multiple phthalocyanine doped ferrites/CMWCNTs for detection of rosmarinic acid.

Ferrites have attracted considerable attention in biosensor developments owing to their favorable electrochemical and magnetic properties. Speedy and trace analysis can be succeeded by the sensors based on magnetic nanohybrids. In this work, we reported a novel method for one-step synthesis of magnetic ferrites composed of Fe and phthalocyanine. After hybridization with carbonylated multi wall carbon nanotubes, a sensor based on Fe3O4-Pc-CMWCNTs nanocomposites was fabricated for the detection of rosmarinic acid (RA), a bioactive phytochemical. The sensor can be constructed within 30s without any complicated process. A comparison of electrochemical activity between ZnFe2O4-Pc-CMWCNTs and Fe3O4-Pc-CMWCNTs nanohybrids also has been accomplished in this work. Compared with ZnFe2O4-Pc-CMWCNTs based on commonly used ferrites, Fe3O4-Pc-CMWCNTs/MGCE exhibited a higher catalytical ability for the detection of RA. The sensor modified with Fe3O4-Pc-CMWCNTs displayed a low LOD of 0.182 µM with a wide linear range from 0.2 to 400 µM, which was 30 times more sensitive than the one based on ZnFe2O4-Pc-CMWCNTs. The obtained sensor also owned an excellent selectivity, reproducibility, repeatability, and stability, which made it achieve the measurements in plant sample and human serum.