Magnus Willander

Expression of concern for ‘Electrochemical genosensor based on gold nanostars for the detection of Escherichia coli O157:H7 DNA’ by Nasrin Razmi et al., Anal. Methods, 2022, 14, 1562–1570, https://doi.org/10.1039/D2AY00056C.

Electrochemical genosensor based on gold nanostars for E. coli O157:H7 detection constructed. Application of GNSs along with SWV technique provided a fast response for DNA detection of E. coli O157:H7 with a low limit of quantification of 0.01 zM.

In this minireview, we discuss the emerging optical biosensing and bioimaging techniques that leverage the unique optical properties of gold nanoparticles.

Escherichia coli O157:H7 (E. coli O157:H7) is a pathogenic strain of Escherichia coli which has issued as a public health threat because of fatal contamination of food and water. Therefore, accurate detection of pathogenic E. coli is important in environmental and food quality monitoring. In spite of their advantages and high acceptance, culture-based methods, enzyme-linked immunosorbent assays (ELISAs), polymerase chain reaction (PCR), flow cytometry, ATP bioluminescence, and solid-phase cytometry have various drawbacks, including being time-consuming, requiring trained technicians and/or specific equipment, and producing biological waste. Therefore, there is necessity for affordable, rapid, and simple approaches. Electrochemical biosensors have shown great promise for rapid food- and water-borne pathogen detection. Over the last decade, various attempts have been made to develop techniques for the rapid quantification of E. coli O157:H7. This review covers the importance of E. coli O157:H7 and recent progress (from 2015 to 2020) in the development of the sensitivity and selectivity of electrochemical sensors developed for E. coli O157:H7 using different nanomaterials, labels, and electrochemical transducers.

Procalcitonin (PCT) protein has recently been identified as a clinical marker for bacterial infections based on its better sepsis sensitivity. Thus, an increased level of PCT could be linked with disease diagnosis and therapeutics. In this study, we describe the construction of the photoelectrochemical (PEC) PCT immunosensing platform based on it situ grown photo-active CuWO₄ nanospheres over reduced graphene oxide layers (CuWO₄@rGO). The in situ growth strategy enabled the formation of small nanospheres (diameter of 200 nm), primarily composed of tiny self-assembled CuWO₄ nanoparticles (2–5 nm). The synergic coupling of CuWO₄ with rGO layers constructed an excellent photo-active heterojunction for photoelectrochemical (PEC) sensing. The platform was then considered for electrocatalytic (EC) mechanism-based detection of PCT, where inhibition of the photocatalytic oxidation signal of ascorbic acid (AA), subsequent to the antibody–antigen interaction, was recorded as the primary signal response. This inhibition detection approach enabled sensitive detection of PCT in a concentration range of 10 pg·mL⁻¹ to 50 ng.mL⁻¹ with signal sensitivity achievable up to 0.15 pg·mL⁻¹. The proposed PEC hybrid (CuWO₄@rGO) could further be engineered to detect other clinically important species.

Zero dimensional (0D) nanostructured CuO material is prepared by low temperature aqueous chemical growth method using riboflavin as soft template. CuO nanostructures are characterized by scanning electron microscopy (SEM), X-ray diffraction crystallography (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The oval like zero dimensional nanostructures as obtained are few microns in size. CuO nanomaterial is of high purity as confirmed by XRD and XPS. The functional CuO nanomaterial was used for the development of urea biosensor using immobilization of urease on them via physical adsorption method. The developed biosensor has wide linear range of urea detection from 0.01–50 mM with a sensitivity of 93 mV/decade. The fabricated biosensor is selective, stable, reproducible, and repeatable. The proposed analytical device is highly promising and can be used as an alternative tool for monitoring of urea from real samples. Ensuring the practicality of presented urea biosensor, it was successfully applied for the quantification of urea from real samples and the obtained results are highly satisfactory. The CuO nanostructures can also be used for the different applications such as lithium ion batteries, supercapacitors and solar cells.

It is always demanded to prepare a nanostructured material with prominent functional properties for the development of a new generation of devices. This study is focused on the synthesis of heart/dumbbell-like CuO nanostructures using a low-temperature aqueous chemical growth method with vitamin B₁₂ as a soft template and growth directing agent. CuO nanostructures are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. CuO nanostructures are heart/dumbbell like in shape, exhibit high crystalline quality as demonstrated by XRD, and have no impurity as confirmed by XPS. Apparently, CuO material seems to be porous in structure, which can easily carry large amount of enzyme molecules, thus enhanced performance is shown for the determination of uric acid. The working linear range of the biosensor is 0.001 mM to 10 mM with a detection limit of 0.0005 mM and a sensitivity of 61.88 mV/decade. The presented uric acid biosensor is highly stable, repeatable, and reproducible. The analytical practicality of the proposed uric acid biosensor is also monitored. The fabrication methodology is inexpensive, simple, and scalable, which ensures the capitalization of the developed uric acid biosensor for commercialization. Also, CuO material can be used for various applications such as solar cells, lithium ion batteries, and supercapacitors.

The step toward the fabrication of nanodevices with low cost and improved performance is of high demand; therefore, in the present study, different flexible substrates like common paper, textile fabric, plastic and aluminum foil have been utilized to harvest electrical energy. ZnO nanorods (NRs) were grown by using low-temperature aqueous chemical growth method. The obtained ZnO NRs were highly dense, well aligned, uniformly distributed over the substrates and exhibited good crystal quality. The structural study was carried out by using X-ray powder diffraction and scanning electron microscopy. The piezoelectric properties of ZnO NRs were investigated by the help of an atomic force microscope using contact mode. The measurements of generated piezoelectricity were around 16.2 mV, 23.2 mV, 38.5 mV and 43.3 mV for common paper, textile fabric, plastic and aluminum foil, respectively. This investigation is an important step in order to study the effect of different substrates influencing the magnitude of the output voltage under identical growth and measurement conditions. We expect that this study will help identify the most suitable flexible substrate for harvesting energy. It also offers a promising alternative powering source for the next generation nanodevices using non-conventional substrates like aluminum foil. Moreover, the use of aluminum foil as flexible and low cost substrate may pave the way to develop devices in different fields including energy harvesting.

Advances in the miniaturization and portability of the chemical sensing devices have always been hindered by the external power supply problem, which has focused new interest in the fabrication of self-powered sensing devices for disease diagnosis and the monitoring of analytes. This review describes the fabrication of ZnO nanomaterial-based sensors synthesized on different conducting substrates for extracellular detection, and the use of a sharp borosilicate glass capillary (diameter, d = 700 nm) to grow ZnO nanostructures for intracellular detection purposes in individual human and frog cells. The electrocatalytic activity and fast electron transfer properties of the ZnO materials provide the necessary energy to operate as well as a quick sensing device output response, where the role of the nanomorphology utilized for the fabrication of the sensor is crucial for the production of the operational energy. Simplicity, design, cost, sensitivity, selectivity and a quick and stable response are the most important features of a reliable sensor for routine applications. The review details the extra- and intra-cellular applications of the biosensors for the detection and monitoring of different metallic ions present in biological matrices, along with the biomolecules glucose and cholesterol.