Smartphone-based electrochemical analysis integrated with NFC system for the voltammetric detection of heavy metals using a screen-printed graphene electrode

A smartphone sensing fluorescent detection of mercury ion based on silicon quantum dots in environment water

Mercury ion (Hg2+) pose a significant hazard to the natural environment. Conventional techniques like Inductively coupled plasma mass spectrometry, X-ray absorption spectroscopy, among others, pose some disadvantages as they demand a lot of money, need trained employees, and cannot provide on-site detection in real-time. A smartphone sensing technique based on silicon quantum dots (Si-QDs) was presented to detect Hg2+ in the environment without the usage of sophisticated equipment. Meanwhile, the technology was built by utilizing a smartphone to capture gray values of fluorescent images of the Si-QDs-Hg2+ system. Microwave-assisted Si-QDs with tiny particle size, high fluorescence, and good optical stability were created. The fluorescence of the Si-QDs was gradually quenched by raising the Hg2+ concentration from 0.5 μmol/L to 5.0 μmol/L for fluorescent detection with a detection limit of 28 nmol/L. The 94.8-97.1 % recovery demonstrated the viability of the Si-QDs approach for detecting Hg2+. Meanwhile, a smartphone sensing strategy was built by recording the gray value of the fluorescent images of the Si-QDs-Hg2+ systems using a smartphone, and the detection limit of the established approach was 3 nmol/L. The accuracy and reliability of the smartphone strategy were verified with the recovery rates of 80.3-92.5 % in tap water and 87.6-109 % in river water. Electron transfer quenching mechanism between Si-QDs and Hg2+ was evidenced by ultraviolet-visible spectroscopy, fluorescent decay curves, cyclic voltammetry, and Zeta potential. Finally, the suggested approach was used to detect Hg2+ in water samples from various environments.

3D Paper-Based Device Integrated with a Battery-Less NFC Potentiostat for Nonenzymatic Detection of Cholesterol

Portable electrochemical analytical devices such as cholesterol sensors are widely used for disease diagnosis. However, these tools are bulky and require bioreceptors for the specific detection of cholesterol. Herein, a novel 3D electrochemical paper-based analytical device (3D-ePAD) combined with a near-field communication (NFC) potentiostat was developed and applied to the nonenzymatic detection of cholesterol. This 3D-ePAD platform was designed so that all working operations are performed on a single device, which is separated into an origami PAD (oPAD) and an inset PAD (iPAD). β-Cyclodextrin (β-CD), which is immobilized on oPAD, is used as a specific material for the nonenzymatic detection of cholesterol. Through this device, cholesterol detection is integrated with a battery-free NFC potentiostat on a smartphone. The concentration of cholesterol was examined through a [Fe(CN)6]3-/4- current signal as a redox indicator, which was previously stored in the detection part of an iPAD. Under optimal conditions, 3D-ePAD/NFC exhibited a linear detection efficiency of 1-500 μM and a maximum detection limit of 0.3 μM for cholesterol detection. Moreover, the proposed sensor was successfully used to measure cholesterol in real serum samples from humans, and the results were consistent with those of a commercial cholesterol meter. Therefore, the new NFC-operated 3D-ePAD platform can be used as an alternative tool for the nonenzymatic quantification of various biomarkers. In addition, 3D-ePAD/NFC can support the diagnosis of other diseases in the future, as the device is inexpensive, portable, and disposable and functions with low sample volumes.

Sensitive and selective detection of heavy metal ions and organic pollutants with graphene-integrated sensing platforms

Graphene-based sensors have emerged as promising tools for environmental monitoring due to their exceptional properties such as high surface area, excellent electrical conductivity, and sensitivity to various analytes. This paper presents a review of recent advancements in the development and application of graphene-based sensors for the detection of heavy metal ions and organic pollutants. These sensors employ either graphene or its derivatives, often in combination with graphene hybrid nanocomposites, as the primary sensing material. The synthesis methods of graphene and sensing mechanisms of graphene-based sensors are discussed. Furthermore, performance metrics including the determination range and detection limits of these sensors are itemized. The potential challenges and future directions in the field of graphene-based sensors for environmental monitoring are also highlighted. Overall, this review provides valuable insights into the current state-of-the-art technologies and paves the way for the development of highly efficient and reliable sensors for environmental monitoring purposes.

Recent advancements of smartphone-based sensing technology for diagnosis, food safety analysis, and environmental monitoring

The emergence of computationally powerful smartphones, relatively affordable high-resolution camera, drones, and robotic sensors have ushered in a new age of advanced sensible monitoring tools. The present review article investigates the burgeoning smartphone-based sensing paradigms, including surface plasmon resonance (SPR) biosensors, electrochemical biosensors, colorimetric biosensors, and other innovations for modern healthcare. Despite the significant advancements, there are still scarcity of commercially available smart biosensors and hence need to accelerate the rates of technology transfer, application, and user acceptability. The application/necessity of smartphone-based biosensors for Point of Care (POC) testing, such as prognosis, self-diagnosis, monitoring, and treatment selection, have brought remarkable innovations which eventually eliminate sample transportation, sample processing time, and result in rapid findings. Additionally, it articulates recent advances in various smartphone-based multiplexed bio sensors as affordable and portable sensing platforms for point-of-care devices, together with statistics for point-of-care health monitoring and their prospective commercial viability.

NFC Smartphone-Based Electrochemical Microfluidic Device Integrated with Nanobody Recognition for C-Reactive Protein

Point-of-care testing (POCT) devices play a crucial role as tools for disease diagnostics, and the integration of biorecognition elements with electronic components into these devices widens their functionalities and facilitates the development of complex quantitative assays. Unfortunately, biosensors that exploit large conventional IgG antibodies to capture relevant biomarkers are often limited in terms of sensitivity, selectivity, and storage stability, considerably restricting the use of POCT in real-world applications. Therefore, we used nanobodies as they are more suitable for fabricating electrochemical biosensors with near-field communication (NFC) technology. Moreover, a flow-through microfluidic device was implemented in this system for the detection of C-reactive protein (CRP), an inflammation biomarker, and a model analyte. The resulting sensors not only have high sensitivity and portability but also retain automated sequential flow properties through capillary transport without the need for an external pump. We also compared the accuracy of CRP quantitative analyses between commercial PalmSens4 and NFC-based potentiostats. Furthermore, the sensor reliability was evaluated using three biological samples (artificial serum, plasma, and whole blood without any pretreatment). This platform will streamline the development of POCT devices by combining operational simplicity, low cost, fast analysis, and portability.

Unleashing inkjet-printed nanostructured electrodes and battery-free potentiostat for the DNA-based multiplexed detection of SARS-CoV-2 genes

Following the global COVID-19 pandemic triggered by SARS-CoV-2, the need for rapid, specific and cost-effective point-of-care diagnostic solutions remains paramount. Even though COVID-19 is no longer a public health emergency, the disease still poses a global threat leading to deaths, and it continues to change with the risk of new variants emerging causing a new surge in cases and deaths. Here, we address the urgent need for rapid, cost-effective and point-of-care diagnostic solutions for SARS-CoV-2. We propose a multiplexed DNA-based sensing platform that utilizes inkjet-printed nanostructured gold electrodes and an inkjet-printed battery-free near-field communication (NFC) potentiostat for the simultaneous quantitative detection of two SARS-CoV-2 genes, the ORF1ab and the N gene. The detection strategy based on the formation of an RNA-DNA sandwich structure leads to a highly specific electrochemical output. The inkjet-printed nanostructured gold electrodes providing a large surface area enable efficient binding and increase the sensitivity. The inkjet-printed battery-free NFC potentiostat enables rapid measurements and real-time data analysis via a smartphone application, making the platform accessible and portable. With the advantages of speed (5 min), simplicity, sensitivity (low pM range, ∼450% signal gain) and cost-effectiveness, the proposed platform is a promising alternative for point-of-care diagnostics and high-throughput analysis that complements the COVID-19 diagnostic toolkit.

Optimized porous carbon-fibre microelectrode for multiplexed, highly reproducible and repeatable detection of heavy metals in real water samples

This work demonstrates the simultaneous identification of four hazardous heavy metals in water samples, namely copper, lead, cadmium, and mercury. A simple yet selective electrode with the simplest fabrication procedure was used. The modified porous carbon threads coated with gold nanoparticles (AuNPs) was employed as a working electrode. The surface chemistry and morphology of the AuNPs deposited porous carbon thread surface were examined. The electrocatalytic activity of the metals on the Au-modified thread surface was observed using the differential pulse voltammetry (DPV) technique. Furthermore, all four metal ions were detected simultaneously, and no interference was observed. Individual and simultaneous experiments to test the impact of concentration revealed that the limit of detection (LoD) was observed to be 1.126 μM, 1.419 μM, 0.966 μM, 0.736 μM for the Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ metal ions respectively in a linear concentration range of 10-110 μM of each. Subsequently, the study of pH, interference with coexisting metal ions, repeatability study, and stability analysis was also performed. A real sample analysis utilising three different lake water samples is also carried out to further understand the application of the proposed sensor. A good recovery rate is achieved, and the results are reported. This work paves way for the on-field applicability of the present heavy metal detection platform.

Nanomaterials-based portable electrochemical sensing and biosensing systems for clinical and biomedical applications

Miniaturized electrochemical sensing systems are employed in day-to-day uses in the several area from public health to scientific applications. A variety of electrochemical sensor and biosensor systems may not be effectively employed in real-world diagnostic laboratories and biomedical industries due to their limitation of portability, cost, analytical period, and need of skilled trainer for operating devices. The design of smart and portable sensors with high sensitivity, good selectivity, rapid measurement, and reusable platforms is the driving strength for sensing glucose, lactate, hydrogen peroxide, nitric oxide, mRNA, etc. The enhancement of sensing abilities of such sensor devices through the incorporation of both novel sensitive nanomaterials and design of sensor strategies are evidenced. Miniaturization, cost and energy efficient, online and quantitative detection and multiple sensing ability are the beneficial of the nanostructured-material-based electrochemical sensor and biosensor systems. Owing to the discriminating catalytic action, solidity and biocompatibility for designing sensing system, nanoscale materials empowered electrochemical detection systems are accomplished of being entrenched into/combined with portable or miniaturized devices for specific applications. In this review, the advance development of portable and smart sensing/biosensing systems derived from nanoscale materials for clinical and biomedical applications is described.

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