Ninhydrin as a novel DNA hybridization indicator applied to a highly reusable electrochemical genosensor for Candida auris

Recent advances in electrochemical aptasensors and genosensors for the detection of pathogens

In recent years, pathogenic microorganisms have caused significant mortality rates and antibiotic resistance and triggered exorbitant healthcare costs. These pathogens often have high transmission rates within human populations. Rapid diagnosis is crucial in controlling and reducing the spread of pathogenic infections. The diagnostic methods currently used against individuals infected with these pathogens include relying on outward symptoms, immunological-based and, some biomolecular ones, which mainly have limitations such as diagnostic errors, time-consuming processes, and high-cost platforms. Electrochemical aptasensors and genosensors have emerged as promising diagnostic tools for rapid, accurate, and cost-effective pathogen detection. These bio-electrochemical platforms have been optimized for diagnostic purposes by incorporating advanced materials (mainly nanomaterials), biomolecular technologies, and innovative designs. This review classifies electrochemical aptasensors and genosensors developed between 2021 and 2023 based on their use of different nanomaterials, such as gold-based, carbon-based, and others that employed other innovative assemblies without the use of nanomaterials. Inspecting the diagnostic features of various sensing platforms against pathogenic analytes can identify research gaps and open new avenues for exploration.

Innovative Biosensing Approaches for Swift Identification of Candida Species, Intrusive Pathogenic Organisms

Candida is the largest genus of medically significant fungi. Although most of its members are commensals, residing harmlessly in human bodies, some are opportunistic and dangerously invasive. These have the ability to cause severe nosocomial candidiasis and candidemia that affect the viscera and bloodstream. A prompt diagnosis will lead to a successful treatment modality. The smart solution of biosensing technologies for rapid and precise detection of Candida species has made remarkable progress. The development of point-of-care (POC) biosensor devices involves sensor precision down to pico-/femtogram level, cost-effectiveness, portability, rapidity, and user-friendliness. However, futuristic diagnostics will depend on exploiting technologies such as multiplexing for high-throughput screening, CRISPR, artificial intelligence (AI), neural networks, the Internet of Things (IoT), and cloud computing of medical databases. This review gives an insight into different biosensor technologies designed for the detection of medically significant Candida species, especially Candida albicans and C. auris, and their applications in the medical setting.

A highly reusable genosensor for late-life depression diagnosis based on microRNA 184 attomolar detection in human plasma

Late-Life Depression (LLD) is one of the most prevalent psychiatric disorders in elderly, causing significant functional impairments. MicroRNAs are small molecules involved in the post-transcriptional regulation of gene expression. Elderly individuals diagnosed with LLD present down regulation of miR-184 (hsa-miR-184) expression compared to healthy patients. Therefore, this miR-184 can be used as a biomarker to diagnose LLD. Current LLD diagnosis depends primarily on clinical subjective identification, based on symptoms and variable scales. This work introduces a novel and facile approach for the LLD diagnosis based on the development of an electrochemical genosensor for miR-184 detection in plasma, using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). DPV results presented a 2-Fold increase in current value for healthy patients, compared to individuals with LLD when monitoring ethidium bromide oxidation peak. For EIS, a 1.5-fold increase in charge transfer resistance for healthy elderly subjects was observed in comparison with depressed patients. In addition, the analytical performance of the biosensor was evaluated using DPV, obtaining a linear response ranging from 10^-9 mol L^-1 to 10^-17 mol L^-1 of miR-184 in plasma and a detection limit of 10 atomoles L^-1. The biosensor presented reusability, selectivity and stability, the current response remained 72% up to 50 days of storage. Thus, the genosensor proved to be efficient in the diagnosis of LLD, as well as the accurate quantification of miR-184 in real plasma samples of healthy and depressed patients.

Strategies for the preparation of non-amplified and amplified genomic dengue gene samples for electrochemical DNA biosensing applications

The application of electrochemical DNA biosensors in real genomic sample detection is challenging due to the existence of complex structures and low genomic concentrations, resulting in inconsistent and low current signals. This work highlights strategies for the treatment of non-amplified and amplified genomic dengue virus gene samples based on real samples before they can be used directly in our DNA electrochemical sensing system, using methylene blue (MB) as a redox indicator. The main steps in this study for preparing non-amplified cDNA were cDNA conversion, heat denaturation, and sonication. To prepare amplified cDNA dengue virus genomic samples using an RT-PCR approach, we optimized a few parameters, such as the annealing temperature, sonication time, and reverse to forward (R/F) primer concentration ratio. We discovered that the generated methylene blue (MB) signals during the electrochemical sensing of non-amplified and amplified samples differ due to the different MB binding affinities based on the sequence length and base composition. The findings show that our developed electrochemical DNA biosensor successfully discriminates MB current signals in the presence and absence of the target genomic dengue virus, indicating that both samples were successfully treated. This work also provides interesting information about the critical factors in the preparation of genomic gene samples for developing miniaturized PCR-based electrochemical sensing applications in the future. We also discuss the limitations and provide suggestions related to using redox-indicator-based electrochemical biosensors to detect real genomic nucleic acid genes.