Sandwich-like electrochemical aptasensing of heat shock protein 70 kDa (HSP70): Application in diagnosis/prognosis of coronavirus disease 2019 (COVID-19).

In this research, by using aptamer-conjugated gold nanoparticles (aptamer-AuNPs) and a modified glassy carbon electrode (GCE) with reduced graphene oxide (rGO) and Acropora-like gold (ALG) nanostructure, a sandwich-like system provided for sensitive detection of heat shock protein 70 kDa (HSP70), which applied as a functional biomarker in diagnosis/prognosis of COVID-19. Initially, the surface of the GCE was improved with rGO and ALG nanostructures, respectively. Then, an aptamer sequence as the first part of the bioreceptor was covalently bound on the surface of the GCE/rGO/ALG nanostructures. After adding the analyte, the second part of the bioreceptor (aptamer-AuNPs) was immobilized on the electrode surface to improve the diagnostic performance. The designed aptasensor detected HSP70 in a wide linear range, from 5 pg mL-1 to 75 ng mL-1, with a limit of detection (LOD) of ∼2 pg mL-1. The aptasensor was stable for 3 weeks and applicable in detecting 40 real plasma samples of COVID-19 patients. The diagnostic sensitivity and specificity were 90% and 85%, respectively, compared with the reverse transcription-polymerase chain reaction (RT-PCR) method.

Disposable electrochemical microfluidic device for ultrasensitive detection of egg allergen in wine samples.

Food allergies have been increasing all over the world. Egg is an important component in the food industries and the second most common cause of food allergy, shortly after milk. In the wine industry, egg white is applied as a fining agent for tannin removal. In this study, a sandwich-based immunoassay for ultrasensitive detection of ovalbumin (OVA) in wine samples was developed. The assay involves the use of magnetic beads (MBs) decorated with a polyclonal anti-OVA antibody (Ab2) and horseradish peroxidase (HRP), used as label for the quantification in a disposable electrochemical microfluidic device (DEµD) here developed. The Ab2-MB-HRP prepared was applied to capture, separate, and pre-concentrate OVA from wine samples. In the DEµD, OVA was immune-magnetically captured (OVA-Ab2-MB-HRP), producing a sandwich structure (GO-Ab1-OVA-Ab2-MB-HRP) on the electrode's surface. This arrangement results in an ultrasensitive device, achieving the ultralow limit of detection of 0.2 fg mL-1 OVA. Five samples of wines were analyzed by using the immuno-magneto-assay which presents excellent accuracy compared with enzyme-linked immunosorbent assay (ELISA).

Copper removal using a heavy-metal resistant microbial consortium in a fixed-bed reactor.

A heavy-metal resistant bacterial consortium was obtained from a contaminated river in São Paulo, Brazil and utilized for the design of a fixed-bed column for the removal of copper. Prior to the design of the fixed-bed bioreactor, the copper removal capacity by the live consortium and the effects of copper in the consortium biofilm formation were investigated. The Langmuir model indicated that the sorption capacity of the consortium for copper was 450.0 mg/g dry cells. The biosorption of copper into the microbial biomass was attributed to carboxyl and hydroxyl groups present in the microbial biomass. The effect of copper in planktonic cells to form biofilm under copper rich conditions was investigated with confocal microscopy. The results revealed that biofilm formed after 72 h exposure to copper presented a reduced thickness by 57% when compared to the control; however 84% of the total cells were still alive. The fixed-bed bioreactor was set up by growing the consortium biofilm on granular activated carbon (GAC) and analyzed for copper removal. The biofilm-GAC (BGAC) column retained 45% of the copper mass present in the influent, as opposed to 17% in the control column that contained GAC only. These findings suggest that native microbial communities in sites contaminated with heavy metals can be immobilized in fixed-bed bioreactors and used to treat metal contaminated water.