Functionalized Graphene Quantum Dots (GQDs) based Label-Free Optical Fluorescence Sensor for CD59 Antigen Detection and Cellular Bioimaging.

Cluster of differentiation (CD59), a cell surface glycoprotein, regulates the complement system to prevent immune damage. In cancer, altered CD59 expression allows tumors to evade immune surveillance, promote growth, and resist certain immunotherapies. Targeting CD59 could enhance cancer treatment strategies by boosting the immune response against tumors. Herein, we present a one-step synthesis of Polyethyleneimine (PEI) functionalized graphene quantum dots (Lf-GQDs) from weathered lemon leaf extract. The fabricated Lf-GQDs were successfully used for the quantitative detection of the cluster of CD59 antigen that is reported for its expression in different types of cancer. In this work, we utilized orientation-based attachment of CD59 antibody (Anti-CD59). Our findings reveal that, instead of using random serial addition of antigen or antibody, oriented conjugation saves accumulated concentration offering greater sensitivity and selectivity. The Anti-CD59@Lf-GQDs immunosensor was fabricated using the oriented conjugation of antibodies onto the Lf-GQDs surface. Besides, the fabricated immunosensor demonstrated detection of CD59 in the range of 0.01 to 40.0 ng mL-1 with a low detection limit of 5.3 pg mL-1. Besides, the cellular uptake potential of the synthesized Lf-GQDs was also performed in A549 cells using a bioimaging study. The present approach represents the optimal utilization of Anti-CD59 and CD59 antigen. This approach could afford a pathway for constructing oriented conjugation of antibodies on the nanomaterials-based immunosensor for different biomarkers 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.

Point-of-Care Devices for Viral Detection: COVID-19 Pandemic and Beyond.

The pandemic of COVID-19 and its widespread transmission have made us realize the importance of early, quick diagnostic tests for facilitating effective cure and management. The primary obstacles encountered were accurately distinguishing COVID-19 from other illnesses including the flu, common cold, etc. While the polymerase chain reaction technique is a robust technique for the determination of SARS-CoV-2 in patients of COVID-19, there arises a high demand for affordable, quick, user-friendly, and precise point-of-care (POC) diagnostic in therapeutic settings. The necessity for available tests with rapid outcomes spurred the advancement of POC tests that are characterized by speed, automation, and high precision and accuracy. Paper-based POC devices have gained increasing interest in recent years because of rapid, low-cost detection without requiring external instruments. At present, microfluidic paper-based analysis devices have garnered public attention and accelerated the development of such POCT for efficient multistep assays. In the current review, our focus will be on the fabrication of detection modules for SARS-CoV-2. Here, we have included a discussion on various strategies for the detection of viral moieties. The compilation of these strategies would offer comprehensive insight into the detection of the causative agent preparedness for future pandemics. We also provide a descriptive outline for paper-based diagnostic platforms, involving the determination mechanisms, as well as a commercial kit for COVID-19 as well as their outlook.

Gold nanoparticles modified reduced graphene oxide nanosheets based dual-quencher for highly sensitive detection of carcinoembryonic antigen.

In the current scenario, the dominance of cancer is becoming a disastrous threat to mankind. Therefore, an advanced analytical approach is desired as the need of the hour for early diagnosis to curb the menace of cancer. In this context, the present work reports the development of nano surface energy transfer (NSET) based fluorescent immunosensor for carcinoembryonic antigen (CEA) detection utilizing protein functionalized graphene quantum dots (anti-CEA/amine-GQDs) and a nanocomposite of nanostructured gold and reduced graphene oxide (AuNPs@rGO) as energy donor-acceptor pair, respectively. The obtained AuNPs@rGO nanocomposite has been characterized by different advanced analytical techniques. The functionality of the biosensor depends on quenching the fluorescence of anti-CEA/amine-GQDs donor species by AuNPs@rGO acceptor species, followed by the gradual recovery of GQDs' fluorescence after CEA addition. The efficient energy transfer kinetics have been envisaged by utilizing the AuNPs@rGO nanocomposite as a dual-quencher nanoprobe that revealed improved energy transfer and quenching efficiency (∼62 %, 88 %) compared to AuNPs (∼43 %, 81 %) as a single quencher. Further, the developed biosensing platform successfully detected CEA biomarker with notable biosensing parameters, including a wider linear detection range (0.001-500 ng mL-1), fast response time (24 min), and a significantly low detection limit (0.35 pg mL-1).

Sensing and 3D printing technologies in personalized healthcare for the management of health crises including the COVID-19 outbreak.

A major threat that has surrounded human civilization since the beginning of the year 2020 is the outbreak of coronavirus disease 2019 (COVID-19). It has been declared a pandemic by the World Health Organization and significantly affected populations globally, causing medical and economic despair. Healthcare chains across the globe have been under grave stress owing to shortages of medical equipments necessary to address a pandemic. Furthermore, personal protective equipment supplies, mandatory for healthcare staff for treating severely ill patients, have been in short supply. To address the necessary requisites during the pandemic, several researchers, hospitals, and industries collaborated to meet the demand for these medical equipments in an economically viable manner. In this context, 3D printing technologies have provided enormous potential in creating personalized healthcare equipment, including face masks, face shields, rapid detection kits, testing swabs, biosensors, and various ventilator components. This has been made possible by capitalizing on centralized large-scale manufacturing using 3D printing and local distribution of verified and tested computer-aided design files. The primary focus of this study is, "How 3D printing is helpful in developing these equipments, and how it can be helpful in the development and deployment of various sensing and point-of-care-testing (POCTs) devices for the commercialization?" Further, the present study also takes care of patient safety by implementing novel 3D printed health equipment used for COVID-19 patients. Moreover, the study helps identify and highlight the efforts made by various organizations toward the usage of 3D printing technologies, which are helpful in combating the ongoing pandemic.

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%.

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.

Optimization, fabrication, and characterization of four electrode-based sensors for blood impedance measurement.

In this work, an optimized, non-invasive four electrode-based impedimetric sensors have been designed, fabricated, and characterized for measuring the impedance of a biological cell. The impedimetric sensors having four mono-polar electrodes were fabricated utilizing the photolithography technique with gold as the electrode material. Furthermore, the impedance of the electrolyte/electrode interface was simulated by optimizing different parameters, including applied voltage, PBS thickness, and diameter, using COMSOL Multiphysics software for a frequency range of 100 Hz to 1 MHz. Next, the impedance of the fabricated device was measured experimentally using the electrochemical impedance spectroscopy (EIS) technique. Then, the COMSOL data was equated with the impedance obtained from the fabricated devices to realize the feasibility and error percentage (RSE < 5%) of the sensor. The equivalent circuit model for the measured impedance data of PBS was obtained utilizing the ZsimpWin software. Besides, the mathematical relations between the impedance, phase angle and the area of the electrode were interpreted for the fabricated impedimetric sensors. Later on, a real blood sample was also characterized to demonstrate the feasibility and the validity of the proposed technique and the fabricated devices in cell diagnosis.

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

In the current study, novel four electrode-based impedimetric biosensors have been fabricated using photolithography techniques and utilized to evaluate the cytotoxicity of tamoxifen on cervical cancer cell lines. The cell impedance was measured employing the electric cell-substrate impedance sensing (ECIS) method over the frequency range of 100 Hz to 1 MHz. The results obtained from impedimetric biosensors indicate that tamoxifen caused a significant reduction in the number of HeLa cells on the electrode surfaces in a dose-dependent manner. Next, the impedance values recorded by the fabricated biosensors have been compared with the results obtained from the different conventional techniques such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), live-dead cell assay, and flow cytometric analysis to estimate the cytotoxicity of tamoxifen. The impedimetric cytotoxicity of tamoxifen over the growth and proliferation of HeLa cells correlates well with the traditional methods. In addition, the IC50 values obtained from impedimetric data and MTT assay are comparable, signifying that the ECIS technique can be an alternative method to assess the cytotoxicity of different novel drugs. The working principle of the biosensor has been examined by scanning electron microscopy, indicating the detachment of cells from gold surfaces in a dose-dependent manner, signifying the decrease in impedance at higher drug doses.

Biofunctionalized Graphene Quantum Dots Based Fluorescent Biosensor toward Efficient Detection of Small Cell Lung Cancer.

Quantitative detection of cancer biomarkers with higher accuracy and sensitivity provides an effective platform for screening, monitoring, early diagnosis, and disease surveillance. The present work demonstrates the fabrication and application of fluorescent turn-on biosensor for ultrasensitive detection of small cell lung cancer biomarker utilizing biofunctionalized graphene quantum dots as the energy donor and gold nanoparticles (AuNPs) as the energy acceptor. One-pot and the bottom-up hydrothermal route have been employed for the synthesis of in situ amine-functionalized and nitrogen-doped graphene quantum dots (amine-N-GQDs) and further characterized experimentally by different analytical techniques. The molecular simulation studies were performed using the Material Studio software for optimizing the possible chemical structure of synthesized amine-N-GQDs, a comprehensive analysis of experimental results to validate the presence of potential N-doping and amine functionalization sites. Then monoclonal neuron-specific enolase antibodies (anti-NSE) were covalently immobilized to amine-N-GQDs to provide the biofunctionalized GQDs (anti-NSE/amine-N-GQDs). A label-free and efficient fluorescent biosensor based on nanosurface energy transfer (NSET) between anti-NSE/amine-N-GQDs and AuNPs has been developed for neuron-specific enolase (NSE) detection. The fluorescence response studies of anti-NSE/amine-N-GQDs@AuNPs nanoprobe conducted as a function of NSE antigen exhibited fast response time (16 min), broader linear detection range (0.1 pg mL-1 to 1000 ng mL-1), and remarkably low detection limit (0.09 pg mL-1). Additionally, the fluorescent biosensor exhibited excellent performance in real samples, with an average recovery value of 94.69%.