In this review, we have summarised the synthesis and classification of common nanozymes and their applications in electrochemical biosensor development.

DNA methylation is one of the key epigenetic modifications of DNA that results from the enzymatic addition of a methyl group at the fifth carbon of the cytosine base. It plays a crucial role in cellular development, genomic stability and gene expression. Aberrant DNA methylation is responsible for the pathogenesis of many diseases including cancers. Over the past several decades, many methodologies have been developed to detect DNA methylation. These methodologies range from classical molecular biology and optical approaches, such as bisulfite sequencing, microarrays, quantitative real-time PCR, colorimetry, Raman spectroscopy to the more recent electrochemical approaches. Among these, electrochemical approaches offer sensitive, simple, specific, rapid, and cost-effective analysis of DNA methylation. Additionally, electrochemical methods are highly amenable to miniaturization and possess the potential to be multiplexed. In recent years, several reviews have provided information on the detection strategies of DNA methylation. However, to date, there is no comprehensive evaluation of electrochemical DNA methylation detection strategies. Herein, we address the recent developments of electrochemical DNA methylation detection approaches. Furthermore, we highlight the major technical and biological challenges involved in these strategies and provide suggestions for the future direction of this important field.

Ovarian cancer is the most aggressive of all gynaecological malignancies and is the leading cause of cancer-associated mortality worldwide.

Klebsiella pneumoniae is the second leading causative agent of UTI. In this study, a rapid combined polymerase chain reaction and restriction fragment length polymorphism analysis was developed to identify K. pneumoniae in women, infected with urinary tract infection in the Sylhet city of Bangladesh. Analysis of 11 isolates from women at the age range of 20–55 from three different hospitals were done firstly by amplification with K. pneumoniae specific ITS primers. All of the 11 collected isolates were amplified in PCR and showed the expected 136 bp products. Then, restriction fragment length polymorphism analysis of 11 isolates were conducted after PCR amplification by 16s rRNA universal primers, followed by subsequent digestion and incubation with two restriction enzymes, Pst1 and Alu1. Seven out of 11 isolates were digested by Pst1 restriction enzymes, six isolates digested by Alu1, and while others were negative for both enzymes. Data results reveal that, women at age between 25 and 50 were digested by both enzymes. A woman aged over than 50 was negative while bellow 20 was digested by only Pst1. The results could pave the tactic for further research in the detection of K. pneumoniae from UTI infected women.

from circulating biomarkers (CBs). CBs may be found in several minimally invasive bodily fluids including (but not limited to) blood, saliva, urine, pleural effusions, stool, and cerebrospinal fluid. CBs may include circulating tumor cells (CTCs), circulating tumor RNA/DNA (ctRNA/ctDNA), microRNAs (miRNAs), long non-coding RNAs (lncRNAs), proteins, exosomes, autoantibodies, all of which, are known for their diagnostic and prognostic potential. [1] Currently, clinicians and centralized hospitals practice tissue biopsy for diagnosis and characterization of the heterogeneity of the solid tumor which is crucial for personalized medicine. [1a] Despite the many decades of clinical practice, tissue-based biopsies are subject to sampling bias, suffer from the issue of low repeatability, and cause immense pain in patients as the process is invasive. One of the major concerns of biopsies, often ignored, is the entrance of tumor cells into the systemic circulation during the tissue-sampling process, leading to tumor metastasis. [2] To overcome these issues, the detection of CBs through liquid biopsy has shown promise as a potential replacement due to the rapid and semi or non-invasive sampling process and the repeated analysis of samples during therapeutic interventions aid in decision-making about a particular patient's progress.Due to the advancement of highly specific sequencing and gene amplification technologies, liquid biopsies can access more relevant cancer biomarkers, providing a much-needed alternative to tissue-based biopsy. [1b] These recent advances have led to the development of many miniaturized/ portable platforms. The clinical potential of these micro and nano devices is rapidly growing, but they face many challenges before transitioning to point-of-care (POC) platforms that are sensitive, rapid, and accurate, as discussed herein.Previously, our group [3] provided a critical review of circulating tumor DNA (ctDNA) and liquid biopsy opportunities, challenges, and recent advances in detection technologies. The review examines the potential of ctDNA as a marker in liquid biopsy, as well as the detection methods, challenges, and considerations. We further [1b] provided a comprehensive review of advanced liquid biopsy technologies for CBs detection. Others Liquid biopsy for the analysis of circulating cancer biomarkers (CBs) is a major advancement toward the early detection of cancer. In comparison to tissue biopsy techniques, liquid biopsy is relatively painless, offering multiple sampling opportunities across easily accessible bodily fluids such as blood, urine, and saliva. Liquid biopsy is also relatively inexpensive and simple, avoiding the requirement for specialized laboratory equipment or trained medical staff. Major advances in the field of liquid biopsy are attributed largely to developments in nanotechnology and microfabrication that enables the creation of highly precise chip-based platforms. These devices can overcome detection limitations of an individual biomarker by detecting multiple markers ...

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Dysregulated microRNA associated pathways contribute to the pathology of neurological disorders, hence presenting themselves as a potential candidate for motor neuron disease (MND) diagnosis. Herein, we reported an enzymatic amplification‐free approach for the electrochemical detection of exosomal microRNA (miR‐338‐3p) from preconditioned media of motor neurons obtained from amyotrophic lateral sclerosis (ALS) patients and healthy controls. Our assay utilizes a three‐step strategy that involves i) initial isolation and purification of exosomal miR‐338‐3p from patients and healthy controls using biotinylated complementary capture probe followed by heat‐release of the specific target, ii) direct adsorption of target miR‐338‐3p onto the gold‐loaded ferric oxide nanocatalyst (AuNP‐Fe2O3NC) through affinity interaction between microRNA and exposed gold surfaces within the AuNP‐Fe2O3NC, and iii) gold nanocatalyst‐induced electrocatalytic signal amplification through methylene blue‐ferricyanide redox cycling (MB/[Fe(CN)6]3−). The electrocatalytic signal is monitored by using chronocoulometry at the AuNP–Fe2O3NC‐modified screen‐printed carbon electrode (AuNP‐Fe2O3NC/SPCE). We demonstrated the detection of miR‐338‐3p as low as 100 aM in spiked buffer samples with a relative standard deviation of (%RSD) <5.0 % (n=5). We also demonstrate the successful detection of miR‐338‐3p from a small cohort of preconditioned media of motor neurons obtained from ALS patients and healthy controls. The sensor avoids the use of conventional recognition and transduction layers in hybridization‐based electrochemical miRNA biosensors, polymerase‐based amplifications. It is robust, fast (<2.5 h) and potentially applicable to a wide variety of RNA biomarker detection.

We present a novel amplification-free sandwich type platform assay for electrochemical detection of miRNA. The assay is based on T4 DNA polymerase mediated synthesis of p53 binding DNA sequence at...