No abstract

Quartz crystal microbalance (QCM) biosensors were developed for the sensitive and specific detection of microRNA-21 (miR-21) through the formation of miR-21–DNA hybrid duplexes and non-specific intercalation of surface-modified pyrene molecules.

We report here on novel biosensors for the highly sensitive and specific enzymatic analysis of glycated hemoglobin (HbA1c), which we measured primarily to identify three‐month average plasma glucose concentrations. Hydrogen peroxide (H2O2) was generated in this enzymatic measuring of glycated hemoglobin from oxidative cleavage of fructosyl valine by fructosyl amino acid oxidase, and we then used the generated hydrogen peroxide as a reducing agent of gold (III) ion to synthesize gold (0) as a nanoparticle. We were able to measure the gold nanoparticles obtained from this novel approach using colorimetry under a UV–VIS spectrophotometer. For this colorimetric detection, we analyzed 96‐well plates for glycated hemoglobin, and this system worked very well, with a detection limit of 0.142% and coefficient of variation below 10%. Finally, this method can measure glycated hemoglobin in patients with diabetes.

We present electrochemical biosensors for the analysis of a target miR-155 that work through the formation of miRNA-DNA hybrid duplexes by hybridization of miR-155 with its complementary DNA and through the subsequent intercalation of appropriate intercalating agents on gold electrodes. In the first method, the electrochemical behavior of methylene blue intercalated to the miRNA-DNA hybrid duplex, formed between miR-155 and its complementary DNA, on the gold electrode was measured. In the second method, the miRNA-DNA hybrid duplex formed between ferrocene-labeled DNA and miR-155 in solution is intercalated to the pyrenes immobilized on the electrode surface. This lead to an electrochemical signal being generated from the oxidized ferrocene accumulated on the electrode surface. For each method, the limit of detections for the detection of miR-155 were determined to be 0.96 and 2.22 pM, respectively. In addition, the developed electrochemical biosensors were effective in the quantitation of miR-155 in serum sample.