Recent progress in electrochemical sensors for detection and quantification of malaria.

Malaria is still a major disease in sub-Saharan Africa and South-East Asia. This is despite different interventions by the World Health Organization (WHO), such as insecticide-treated mosquito net, antimalarial drugs, indoor residual spraying, and rapid diagnostic tools. In 2018, the mortality rate due to malaria was estimated to be 405 000, with children under five years accounting for 67% of all malaria deaths. Malaria can be prevented and treated using different strategies as recommended by WHO. However, the lack of rapid diagnostic tools with good selectivity and sensitivity is still a challenge. Therefore there is a need to develop rapid, low-cost, and portable analytical methods for quantifying malaria. This review focuses on the role of malaria biomarkers (Plasmodium falciparum Lactate Dehydrogenase (PfLDH), Plasmodium aldolase, Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP2), Plasmodium falciparum Glutamate dehydrogenase (PfGDH), and Hemozoin) in diagnosis. Recent developments in nanomaterial-based electrochemical and colorimetric biosensors for malaria diagnosis are discussed. Finally, the review concludes with closing remarks and future perspectives of electrochemical biosensors.

A poly(acrylic acid)-modified copper-organic framework for electrochemical determination of vancomycin.

A copper(II) benzene-1,3,5-tricarboxylate (BTC) metal-organic framework (MOF) was modified with poly(acrylic acid) (PAA) and then used in an electrochemical sensor for vancomycin. The MOF, synthesized via a single-pot method, has enhanced solubility and dispersibility in water as compared to HKUST-1 but without compromising its crystallinity and porosity. The MOF was placed on a glassy carbon electrode (GCE) where it shows enhanced electrocatalytic properties. This is assumed to be due to the presence of the poly(acrylic acid) that forms a network between various HKUST-1 crystals through dimer formation between the carboxy groups of BTC and PAA. This also led to better dispersion of the MOF and to improved interaction between MOF and vancomycin. The structural, spectral and electrochemical properties of the MOFs and their vancomycin complexes was characterized. The modified GCE is shown to be a viable tool for electrochemical determination (best at a working potential of 784 mV vs. Ag/AgCl) of the antibiotic vancomycin in spiked urine and serum samples. Response is linear in the 1-500 nM vancomycin concentration range, and the detection limit is 1 nM, with a relative standard deviation of ±4.3%. Graphical abstractSchematic representation of a method for determination of vancomycin. Poly(acrylic acid) modified HKUST-1 (P-HKUST-1) forms a complex with vancomycin [Van-P-HKUST-1] which is coated over glassy carbon electrode (GCE). The decrease in peak current is recorded as response to vancomycin via cyclic voltammetry.

Nanomaterial-based optical and electrochemical techniques for detection of methicillin-resistant Staphylococcus aureus: a review.

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for a number of life-threatening complications in humans. Mutations in the genetic sequence of S. aureus due to the presence of certain genes results in resistance against ß-lactamases. Thus, there is an urgent need for developing highly sensitive techniques for the early detection of MRSA to counter the rise in resistant strains. This review (142 refs.) extensively covers literature reports on nanomaterial-based optical and electrochemical sensors from the year 1983 to date, with particularly emphasis on recent advances in electrochemical sensing (such as voltammetry and impedimetric) and optical sensing (such as colorimetry and fluorometry) techniques. Among the electrochemical methods, various nanomaterials were employed for the modification of electrodes. Whereas, in optical assays, formats such as enzyme linked immunosorbent assay, lateral flow assays or in optical fiber systems are common. In addition, novel sensing platforms are reported by applying advanced nanomaterials which include gold nanoparticles, nanotitania, graphene, graphene-oxide, cadmium telluride and related quantum dots, nanocomposites, upconversion nanoparticles and bacteriophages. Finally, closing remarks and an outlook conclude the review. Graphical abstract Schematic of the diversity of nanomaterial-based methods for detection of methicillin-resistant Staphylococcus aureus (MRSA). AuNPs: gold nanoparticles; QDs: quantum dots; PVL: Panton-Valentine leukocidin; mecA gene: mec-gene complex encoding methicillin resistance.

One pot fabrication of diamino naphthalene -AuNPs decorated graphene nanoplatform for the MRSA detection in the biological sample.

Early monitoring of MRSA can effectively mitigate the disease risk by using Penicillin-binding protein 2a (PbP2a) biomarker. Diamino naphthalene-AuNPs decorated graphene (AuNPsGO-DN) nanocomposite was synthesized for a rapid and sensitive immunosensor detecting PbP2a. The synthesized AuNPsGO-DN nanocomposites were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray diffraction spectroscopy (XRD). Electrochemical characterization done with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrical impedance spectroscopy (EIS) techniques. Anti-PbP2a monoclonal antibodies immobilized at AuNPsGO-DN/GCE via covalent bonding. AuNPs enhanced the electrode surface area and the antibodies' loading. Mercaptopropionic acid (MPA) was a linker between the AuNPs and antibodies, orientated the antibodies as opposite to the PbP2a antigen, and improved the sensitivity and specificity. The antiPbP2a/MPA/AuNPsGO-DN/GCE electrode displayed sensitive and selective detection towards the PbP2a antigen in phosphate buffer saline (PBS pH 7.4). The broad linear range from 0.01 to 8000 pg/mL was obtained with LOD of 0.154 pg/mL and 0.0239 pg/mL, respectively. A label-free, simple, and sensitive immunosensor was developed with a 98-106 % recovery rate in spiked biological samples. It shows the potential applicability of the developed immunoelectrode.

One-pot synthesis of ß-cyclodextrin modified silver nanoparticles for highly sensitive detection of ciprofloxacin.

This study emphases on electrochemical detection of ciprofloxacin in sheep serum and runoff water using silver nanoparticle modified ß-cyclodextrin (Ag-ß-CD) composite. The Ag-ß-CD composite was synthesized via a hydrothermal route, which resulted in a high product yield. Morphological and spectral characterizations of the Ag-ß-CD composite were carried out. The Ag-ß-CD composite was used to detect ciprofloxacin by employing differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The Ag-ß-CD modified electrode displayed excellent specificity towards the electro-oxidation of ciprofloxacin. Further, the sensor gave the best response towards the electro-oxidation of ciprofloxacin near the human physiological pH of 7.5. A linear response was obtained between the concentration range of 0.1 nM to 50 nM and the limit of detection (LOD) at 0.028 nM with high sensitivity and selectivity towards ciprofloxacin oxidation. The current work has a rationally synthesized and characterized nanocomposite with a very high potential for rapid and sensitive detection of ciprofloxacin in spiked sheep blood serum and domestic runoff water samples. High sensitivity and low LOD results illustrate good practicability for the detection of ciprofloxacin in such samples in the near future.

Rationally engineered nanosensors: A novel strategy for the detection of heavy metal ions in the environment.

Heavy metal ions (HMIs) have been mainly originated from natural and anthropogenic agents. It has become one of biggest societal issues due to their recognised accumulative and toxic effects in the environment as well as biological media. Key measures are required to reduce the risks posed by toxic metal pollutants existing in the environment. The increased research activities of HMIs detection, and use of technologies based on electrochemical detection that combine with engineered nanomaterials, is a key promising and innovative strategy that can potentially confine heavy metal poisoning. Deep understanding of the characteristics of the physicochemical properties of nanomaterials is highly required. It is also important to interpret the parameters at the nano-bio interface level that merely affect cross-interactions between nanomaterials and HMIs. Therefore, the authors outlined the state-of-the-art techniques that used engineeringly developed nanomaterials to detect HMIs in the environment. The possible novel applications of extensive and relatively low-cost HMIs monitoring and detection are discussed on the basis of these strengths. Finally, it is concluded by providing gist on acquaintance with facts in the present-day scenario along with highlighting areas to explore the strategies to overcome the current limitations for practical applications is useful in further generations of nano-world.

Prostate cancer biomarkers detection using nanoparticles based electrochemical biosensors.

Prostate cancer (PCa) is the most prevalent cancer with a high mortality rate. The early and accurate detection of PCa can significantly reduce mortality and saves lives. Hence, the nanomaterials based electrochemical nano-biosensors for PCa biomarkers will be the excellent alternative for diagnosis, detection and management of disease condition. In this review, we present a concise summary of the latest attainment and advancement in the use of nanoparticles for the diagnosis of PCa biomarkers. This review highlighted the importance of applying specific biomarkers along with nanomaterials like gold, magnetic, carbon nanotubes, and many other materials for developing electrochemical nanobiosensors in PCa detection. In addition to a summary on PCa detection, we further ensure future perspectives in PCa biomarkers detection, sensitivity, simplicity, rapidity, accuracy, cost-effectiveness and succeeding optimizations of novel technologies for more feasibility. Finally, closing remarks and an outlook conclude the review.

A highly dispersed multi-walled carbon nanotubes and poly(methyl orange) based electrochemical sensor for the determination of an anti-malarial drug: Amodiaquine.

A glassy carbon electrode modified with electrochemically polymerized methyl orange (PMO) and multi-walled carbon nanotubes (MWCNT) was developed. The morphologies of the fabricating materials (PMO and MWCNT) were investigated by field-emission scanning electron microscopy (FE-SEM). The designed sensor was used for the sensitive determination of amodiaquine (AQ), an anti-malaria drug. AQ was developed as an alternative to chloroquine because of its activity against chloroquine-resistant Plasmodium falciparum (P. falciparum) parasites. The modified electrode was employed to study the electrochemical oxidation of AQ using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Under optimal experimental conditions, DPV exhibited a linear response in the concentration range from 1.0 × 10-7 to 3.5 × 10-6 mol L-1 with a limit of detection (LOD) of 8.9 × 10-8 mol L-1. Furthermore, the number of electrons and protons involved in the electrochemical study of AQ was also calculated and a plausible mechanism for the electro-oxidation of AQ was deduced. The developed sensor demonstrated analytical applicability as it was successfully employed to determine the drug AQ in pharmaceutical formulations and human urine samples.