Four electrode-based impedimetric biosensors for evaluating cytotoxicity of tamoxifen on cervical cancer cells

Sensitive and reliable lab-on-paper biosensor for label-free detection of exosomes by electrochemical impedance spectroscopy

A new, sensitive, and cost-effective lab-on-paper-based immunosensor was designed based on electrochemical impedance spectroscopy (EIS) for the detection of exosomes. EIS was selected as the determination method since there was a surface blockage in electron transfer by binding the exosomes to the transducer. Briefly, the carbon working electrode (WE) on the paper electrode (PE) was modified with gold particles (AuPs@PE) and then conjugated with anti-CD9 (Anti-CD9/AuPs@PE) for the detection of exosomes. Variables involved in the biosensor design were optimized with the univariate mode. The developed method presents the limit of detection of  8.7 × 102 exosomes mL-1, which is lower than that of many other available methods under the best conditions. The biosensor was also tested with urine samples from cancer patients with high recoveries. Due to this  a unique, low-cost, biodegradable technology is presented that can directly measure exosomes without labeling them for early cancer or metastasis detection.

Air-brush spray coated Ti3C2-MXene-graphene nanohybrid thin film based electrochemical biosensor for cancer biomarker detection

Cancer is a significant health hazard worldwide and poses a greater threat to the quality of human life. Quantifying cancer biomarkers with high sensitivity has demonstrated considerable potential for compelling, quick, cost-effective, and minimally invasive early-stage cancer detection. In line with this, efforts have been made towards developing an f-graphene@Ti3C2-MXene nanohybrid thin-film-based electrochemical biosensing platform for efficient carcinoembryonic antigen (CEA) detection. The air-brush spray coating technique has been utilized for depositing the uniform thin films of amine functionalized graphene (f-graphene) and Ti3C2-MXene nanohybrid on ITO-coated glass substrate. The chemical bonding and morphological studies of the deposited nanohybrid thin films are characterized by advanced analytical tools, including XRD, XPS, and FESEM. The EDC-NHS chemistry is employed to immobilize the deposited thin films with monoclonal anti-CEA antibodies, followed by blocking the non-specific binding sites with BSA. The electrochemical response and optimization of biosensing parameters have been conducted using CV and DPV techniques. The optimized BSA/anti-CEA/f-graphene@Ti3C2-MXene immunoelectrode showed the ability to detect CEA biomarker from 0.01 pg mL-1 to 2000 ng mL-1 having a considerably lower detection limit of 0.30 pg mL-1.

A Review on Microfluidics-Based Impedance Biosensors

Electrical impedance biosensors are powerful and continuously being developed for various biological sensing applications. In this line, the sensitivity of impedance biosensors embedded with microfluidic technologies, such as sheath flow focusing, dielectrophoretic focusing, and interdigitated electrode arrays, can still be greatly improved. In particular, reagent consumption reduction and analysis time-shortening features can highly increase the analytical capabilities of such biosensors. Moreover, the reliability and efficiency of analyses are benefited by microfluidics-enabled automation. Through the use of mature microfluidic technology, complicated biological processes can be shrunk and integrated into a single microfluidic system (e.g., lab-on-a-chip or micro-total analysis systems). By incorporating electrical impedance biosensors, hand-held and bench-top microfluidic systems can be easily developed and operated by personnel without professional training. Furthermore, the impedance spectrum provides broad information regarding cell size, membrane capacitance, cytoplasmic conductivity, and cytoplasmic permittivity without the need for fluorescent labeling, magnetic modifications, or other cellular treatments. In this review article, a comprehensive summary of microfluidics-based impedance biosensors is presented. The structure of this article is based on the different substrate material categorizations. Moreover, the development trend of microfluidics-based impedance biosensors is discussed, along with difficulties and challenges that may be encountered in the future.

A549 Cell-Covered Electrodes as a Sensing Element for Detection of Effects of Zn2+ Ions in a Solution

Electrochemical-based biosensors have the potential to be a fast, label-free, simple approach to detecting the effects of cytotoxic substances in liquid media. In the work presented here, a cell-based electrochemical biosensor was developed and evaluated to detect the cytotoxic effects of Zn²⁺ ions in a solution as a reference test chemical. A549 cells were attached to the surface of stainless-steel electrodes. After treatment with ZnCl₂, the morphological changes of the cells and, ultimately, their death and detachment from the electrode surface as cytotoxic effects were detected through changes in the electrical signal. Electrochemical cell-based impedance spectroscopy (ECIS) measurements were conducted with cytotoxicity tests and microscopic observation to investigate the behavior of the A549 cells. As expected, the Zn²⁺ ions caused changes in cell confluency and spreading, which were checked by light microscopy, while the cell morphology and attachment pattern were explored by scanning electron microscopy (SEM). The ECIS measurements confirmed the ability of the biosensor to detect the effects of Zn²⁺ ions on A549 cells attached to the low-cost stainless-steel surfaces and its potential for use as an inexpensive detector for a broad range of chemicals and nanomaterials in their cytotoxic concentrations.

Forecasting the Post-Pandemic Effects of the SARS-CoV-2 Virus Using the Bullwhip Phenomenon Alongside Use of Nanosensors for Disease Containment and Cure

The COVID-19 pandemic has the tendency to affect various organizational paradigm alterations, which civilization hasyet to fully comprehend. Personal to professional, individual to corporate, and across most industries, the spectrum of transformations is vast. Economically, the globe has never been more intertwined, and it has never been subjected to such widespread disruption. While many people have felt and acknowledged the pandemic's short-term repercussions, the resultant paradigm alterations will certainly have long-term consequences with an unknown range and severity. This review paper aims at acknowledging various approaches for the prevention, detection, and diagnosis of the SARS-CoV-2 virus using nanomaterials as a base material. A nanostructure is a material classification based on dimensionality, in proportion to the characteristic diameter and surface area. Nanoparticles, quantum dots, nanowires (NW), carbon nanotubes (CNT), thin films, and nanocomposites are some examples of various dimensions, each acting as a single unit, in terms of transport capacities. Top-down and bottom-up techniques are used to fabricate nanomaterials. The large surface-to-volume ratio of nanomaterials allows one to create extremely sensitive charge or field sensors (electrical sensors, chemical sensors, explosives detection, optical sensors, and gas sensing applications). Nanowires have potential applications in information and communication technologies, low-energy lightning, and medical sensors. Carbon nanotubes have the best environmental stability, electrical characteristics, and surface-to-volume ratio of any nanomaterial, making them ideal for bio-sensing applications. Traditional commercially available techniques have focused on clinical manifestations, as well as molecular and serological detection equipment that can identify the SARS-CoV-2 virus. Scientists are expressing a lot of interest in developing a portable and easy-to-use COVID-19 detection tool. Several unique methodologies and approaches are being investigated as feasible advanced systems capable of meeting the demands. This review article attempts to emphasize the pandemic's aftereffects, utilising the notion of the bullwhip phenomenon's short-term and long-term effects, and it specifies the use of nanomaterials and nanosensors for detection, prevention, diagnosis, and therapy in connection to the SARS-CoV-2.

Ti3C2-MXene decorated with nanostructured silver as a dual-energy acceptor for the fluorometric neuron specific enolase detection

Nanohybrids of two-dimensional (2D) layered materials have shown fascinating prospects towards the fabrication of highly efficient fluorescent immunosensor. In this context, a nanohybrid of ultrathin Ti₃C₂-MXene nanosheets and silver nanoparticles (Ag@Ti₃C₂-MXene) has been reported as a dual-energy acceptor for ultrahigh fluorescence quenching of protein-functionalized graphene quantum dots (anti-NSE/amino-GQDs). The Ti₃C₂-MXene nanosheets are decorated with silver nanoparticles (AgNPs) to obsolete the agglomeration and restacking through a one-pot direct reduction method wherein the 2D Ti₃C₂-MXene nanosheets acted both as a reducing agent and support matrix for AgNPs. The as-prepared nanohybrid is characterized by various techniques to analyze the optical, structural, compositional, and morphological parameters. The quenching efficiency and energy transfer capability between the anti-NSE/amino-GQDs (donor) and Ag@Ti₃C₂-MXene (acceptor) have been explored through steady state and time-resolved spectroscopic studies. Interestingly, the Ag@Ti₃C₂-MXene nanohybrid exhibits better quenching and energy transfer efficiencies in contrast to bare Ti₃C₂-MXene, AgNPs and previously reported AuNPs. Based on optimized donor-acceptor pair, a fluorescent turn-on biosensing system is constructed that revealed improved biosensing characteristics compared to Ti₃C₂-MXene, graphene and AuNPs for the detection of neuron-specific enolase (NSE), including higher sensitivity (∼771 mL ng^-1), broader linear detection range (0.0001-1500 ng mL^-1), better LOD (0.05 pg mL^-1), and faster response time (12 min). Besides, remarkable biosensing capability has been observed in serum samples, with fluorescence recovery of ∼98%.

Evaluation of Cancer Cell Lines by Four-Point Probe Technique, by Impedance Measurements in Various Frequencies

Cell-based biosensors appear to be an attractive tool for the rapid, simple, and cheap monitoring of chemotherapy effects at a very early stage. In this study, electrochemical measurements using a four-point probe method were evaluated for suspensions of four cancer cell lines of different tissue origins: SK-N-SH, HeLa, MCF-7 and MDA-MB-231, all for two different population densities: 50 K and 100 K cells/500 μL. The anticancer agent doxorubicin was applied for each cell type in order to investigate whether the proposed technique was able to determine specific differences in cell responses before and after drug treatment. The proposed methodology can offer valuable insight into the frequency-dependent bioelectrical responses of various cellular systems using a low frequency range and without necessitating lengthy cell culture treatment. The further development of this biosensor assembly with the integration of specially designed cell/electronic interfaces can lead to novel diagnostic biosensors and therapeutic bioelectronics.

Development of low-cost planar electrodes and microfluidic channels for applications in capacitively coupled contactless conductivity detection (C4 D)

Electrochemical techniques are commonly applied to micro total analysis system (μTAS) devices mainly due to its high sensitivity and miniaturization capacity. Among many electrochemical techniques, capacitively coupled contactless conductivity detection (C⁴ D) stands out for not requiring direct electrode-solution contact, avoiding several problems such as electrolysis, bubble formation, and metal degradation. Furthermore, the instrumentation required for C⁴ D measurements is compact, low cost, and easy to use, allowing in situ measurements to be performed even by nonspecialized personal. Contrarily, the production of metallic electrodes and microchannels adequate for C⁴ D measurements commonly requires specialized facilities and workers, increasing the costs of applying these methods. We propose alternatives to batch manufacture metallic electrodes and polymeric microchannels for C⁴ D analysis using more straightforward equipment and lower-cost materials. Three devices with different dielectric layer compositions and electrode sizes were tested and compared regarding their analytical performance. The constructed platforms have shown a reduction of more than 64% in cost when compared to traditional techniques and displayed good linearity (R² ≥ 0.994), reproducibility (RSD ≤ 4.07%, n = 3), and limits of detection (≤0.26 mmol/L) when measuring standard NaCl samples. Therefore, the proposed methods were successfully validated and are available for further C⁴ D applications such as diagnosis of dry-eye syndrome.

Allium sativum derived carbon dots as a potential theranostic agent to combat the COVID-19 crisis

Coronavirus disease 2019 (COVID-19) is one of the worst pandemics to have hit the humanity. The manifestations are quite varied, ranging from severe lung infections to being asymptomatic. Hence, there is an urgent need to champion new tools to accelerate the end of this pandemic. Compromised immunity is a primary feature of COVID-19. Allium sativum (AS) is an effective dietary supplement known for its immune-modulatory, antibacterial, anti-inflammatory, anticancer, antifungal, and anti-viral properties. In this paper, it is hypothesized that carbon dots (CDs) derived from AS (AS-CDs) may possess the potential to downregulate the expression of pro-inflammatory cytokines and revert the immunological aberrations to normal in case of COVID-19. CDs have already been explored in the world of nanobiomedicine as a promising theranostic candidates for bioimaging and drug/gene delivery. The antifibrotic and antioxidant effects of AS are elaborated, as demonstrated in several studies. It is found that the most active constituent of AS, allicin has a highly potent antioxidant and reactive oxygen species (ROS) scavenging effect. The antibacterial, antifungal, and anti-viral effects along with their capability of negating inflammatory effects and cytokine storm are discussed. The synthesis of theranostic CDs from AS may provide a novel weapon in the therapeutic armamentarium for the management of COVID-19 infection and, at the same time, could act as a diagnostic agent for COVID-19.