Rapid One-Pot Microwave Assisted Green Synthesis Nitrogen Doped Carbon Quantum Dots as Fluorescent Precursor for Estimation of Modafinil as Post-Covid Neurological Drug in Human Plasma with Greenness Assessments.

The neuro-stimulant anti-narcoleptic drug as modafinil (MOD) is used to treatment neurological conditions caused by COVID-19. MOD was used to treatment narcolepsy, shift-work sleep disorder, and obstructive sleep apnea-related sleepiness. So, an innovative, quick, economical, selective, and ecologically friendly procedure was carried out. A highly sensitive N@CQDs technique was created from green Eruca sativa leaves in about 4 min using microwave synthesis at 700 w. The quantum yield of the synthesized N@CQDs was found to be 41.39%. By increasing the concentration of MOD, the quantum dots' fluorescence intensity was gradually quenched. After being excited at 445 nm, the fluorescence reading was recorded at 515 nm. The linear range was found to be in the range 50 - 700 ng mL-1 with lower limit of quantitation (LOQ) equal to 45.00 ng mL-1. The current method was fully validated and bio analytically according to (US-FDA and ICH) guidelines. Full characterization of the N@CQDs has been conducted by high resolution transmission electron microscope (HRTEM), Zeta potential measurement, fluorescence, UV-VIS, and FTIR spectroscopy. Various experimental variables including pH, QDs concentration and the reaction time were optimized. The proposed study is simply implemented for the therapeutic drug monitoring system (TDMS) and various clinical laboratories for further pharmacokinetic research.

A Novel Strategy for Rapid Fluorescence Detection of FluB and SARS-CoV-2.

Undoubtedly, SARS-CoV-2 has caused an outbreak of pneumonia that evolved into a worldwide pandemic. The confusion of early symptoms of the SARS-CoV-2 infection with other respiratory virus infections made it very difficult to block its spread, leading to the expansion of the outbreak and an unreasonable demand for medical resource allocation. The traditional immunochromatographic test strip (ICTS) can detect one analyte with one sample. Herein, this study presents a novel strategy for the simultaneous rapid detection of FluB/SARS-CoV-2, including quantum dot fluorescent microspheres (QDFM) ICTS and a supporting device. The ICTS could be applied to realize simultaneous detection of FluB and SARS-CoV-2 with one test in a short time. A device supporting FluB/SARS-CoV-2 QDFM ICTS was designed and had the characteristics of being safe, portable, low-cost, relatively stable, and easy to use, ensuring the device could replace the immunofluorescence analyzer in cases where there is no need for quantification. This device does not need to be operated by professional and technical personnel and has commercial application potential.

Novel approach based on GQD-PHB as anchoring platform for the development of SARS-CoV-2 electrochemical immunosensor.

In the present work, we report an innovative approach for immunosensors construction. The experimental strategy is based on the anchoring of biological material at screen-printed carbon electrode (SPE) modified with electrodeposited Graphene Quantum Dots (GQD) and polyhydroxybutyric acid (PHB). It was used as functional substract basis for the recognition site receptor-binding domain (RBD) from coronavirus spike protein (SARS-CoV-2), for the detection of Anti-S antibodies (AbS). SEM images and EDS spectra suggest an interaction of the protein with GQD-PHB sites at the electrode surface. Differential pulse voltametric (DPV) measurements were performed before and after incubation, in presence of the target, shown a decrease in voltametric signal of an electrochemical probe ([Fe(CN)6]3/4-). Using the optimal experimental conditions, analytical curves were performed in PBS and human serum spiked with AbS showing a slight matrix effect and a relationship between voltametric signal and AbS concentration in the range of 100 ng mL-1 and 10 µg mL-1. The selectivity of the proposed sensor was tested against yellow fever antibodies (YF) and the selective layer on the electrode surface did not interact with these unspecific antibodies. Eight samples of blood serum were analyzed and 87.5% of these total investigated provided adequate results. In addition, the present approach showed better results against traditional EDC/NHS reaction with enhancements in time and the possibility to develop an immunosensor in a single drop, since the proteins can be anchored prior to the electrode modification step.

A fluorescence digital image-based method using carbon quantum dots to evaluate the compliance of a biocidal agent.

In this work, a simple, low-cost and easy-to-handle analytical procedure based on carbon quantum dots (CQDs) is proposed to check commercially available formulated microbicides that are used to mitigate the transmission of viruses, such as SARS-COV-2, or bacterial diseases. For this purpose, CQDs were synthesized via pyrolysis using citric acid and ethylenediamine as precursors to produce an intense fluorescence that is used to measure the concentration of hypochlorite, an important biocidal agent present in sanitizing mats, by quenching mechanisms. The characterization of the CQDs was performed using IR spectrophotometry, UV-Vis spectrophotometry, spectrofluorometry, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, X-ray diffraction, energy-dispersive spectroscopy, and zeta potential measurements. For analytical purposes, fluorescence was measured in a UV chamber irradiated using an LED with the maximum emission at 350 nm. A smartphone was coupled to the UV chamber to measure the fluorescence quenching due to the presence of hypochlorite, and further the digital images were decomposed by RGB data using free software. Tests of pH, CQD concentration and stability of the fluorescence emitted were performed. The stability study of the fluorescence emitted by the CQD solution showed a relative standard deviation lower than 5.0%. The fluorescence digital image-based (FDIB) method resulted in a linear range from 17.44 µmol L-1 to 90.0 µmol L-1 with an LOD of 3.30 µmol L-1 for the determination of hypochlorite using a microplate made of PLA (polylactic acid) customized using a 3D printer. Furthermore, the hypochlorite concentration was tested in situ for its compliance in a sanitizing mat, in a real use situation (daily, a group of four people, each one kept their feet on the mat for 30 s). After 2.5 h, the monitored concentration of hypochlorite was 0.04953% (w/v) or 7.63 mmol L-1, and therefore, it was inefficient to act as a sanitizing agent. Thus, for the first time in the literature, an FDIB method with CQDs is used to verify in situ microbicide practices with a fast and low-cost analytical procedure.

Surface plasmon resonance aptasensor based on niobium carbide MXene quantum dots for nucleocapsid of SARS-CoV-2 detection.

A novel label-free surface plasmon resonance (SPR) aptasensor has been constructed for the detection of N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots (Nb2C-SH QDs) as the bioplatform for anchoring N-gene-targeted aptamer. In the presence of SARS-CoV-2 N-gene, the immobilized aptamer strands changed their conformation to specifically bind with N-gene. It thus increased the contact area or enlarged the distance between aptamer and the SPR chip, resulting in a change of the SPR signal irradiated by the laser (He-Ne) with the wavelength (λ) of 633 nm. Nb2C QDs were derived from Nb2C MXene nanosheets via a solvothermal method, followed by functionalization with octadecanethiol through a self-assembling method. Subsequently, the gold chip for SPR measurements was modified with Nb2C-SH QDs via covalent binding of the Au-S bond also by self-assembling interaction. Nb2C-SH QDs not only resulted in high bioaffinity toward aptamer but also enhanced the SPR response. Thus, the Nb2C-SH QD-based SPR aptasensor had low limit of detection (LOD) of 4.9 pg mL-1 toward N-gene within the concentration range 0.05 to 100 ng mL-1. The sensor also showed excellent selectivity in the presence of various respiratory viruses and proteins in human serum and high stability. Moreover, the Nb2C-SH QD-based SPR aptasensor displayed a vast practical application for the qualitative analysis of N-gene from different samples, including seawater, seafood, and human serum. Thus, this work can provide a deep insight into the construction of the aptasensor for detecting SARS-CoV-2 in complex environments. A novel label-free surface plasmon resonance aptasensor has been constructed to detect sensitively and selectively the N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots as the scaffold to anchor the N-gene-targeted aptamer.

Ultrasensitive and Simultaneous Detection of Two Specific SARS-CoV-2 Antigens in Human Specimens Using Direct/Enrichment Dual-Mode Fluorescence Lateral Flow Immunoassay.

Sensitive point-of-care methods for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in clinical specimens are urgently needed to achieve rapid screening of viral infection. We developed a magnetic quantum dot-based dual-mode lateral flow immunoassay (LFIA) biosensor for the high-sensitivity simultaneous detection of SARS-CoV-2 spike (S) and nucleocapsid protein (NP) antigens, which is beneficial for improving the detection accuracy and efficiency of SARS-CoV-2 infection in the point-of-care testing area. A high-performance magnetic quantum dot with a triple-QD shell (MagTQD) nanotag was first fabricated and integrated into the LFIA system to provide superior fluorescence signals, enrichment ability, and detectability for S/NP antigen testing. Two detection modes were provided by the proposed MagTQD-LFIA. The direct mode was used for rapid screening or urgent detection of suspected samples within 10 min, and the enrichment mode was used for the highly sensitive and quantitative analysis of SARS-CoV-2 antigens in biological samples without the interference of the "hook effect." The simultaneous detection of SARS-CoV-2 S/NP antigens was conducted in one LFIA strip, and the detection limits for two antigens under direct and enrichment modes were 1 and 0.5 pg/mL, respectively. The MagTQD-LFIA showed high accuracy, specificity, and stability in saliva and nasal swab samples and is an efficient tool with flexibility to meet the testing requirements for SARS-CoV-2 antigens in various situations.

The Influence of UV Light on Photodegradation of Acetylsalicylic Acid.

Photodegradation of the aqueous solutions of acetylsalicylic acid, in the absence (ASA) and the presence of excipients (ASE), is demonstrated by the photoluminescence (PL). A shift of the PL bands from 342 and 338 nm to 358 and 361-397 nm for ASA and ASE in solid state and as aqueous solutions was reported. By exposure of the solution of ASA 0.3 M to UV light, a decrease in the PL band intensity was highlighted. This behavior was revealed for ASA in the presence of phosphate buffer (PB) having the pH equal to 6.4, 7, and 8 or by the interaction with NaOH 0.3 M. A different behavior was reported in the case of ASE. In the presence of PB, an increase in the intensity of the PL band of ASE simultaneously with a change of the ratio between the intensities of the bands at 361-364 and 394-397 nm was highlighted. The differences between PL spectra of ASA and ASE have their origin in the presence of salicylic acid (SAL). The interaction of ASE with NaOH induces a shift of the PL band at 405-407 nm. Arguments for the reaction of ASA with NaOH are shown by Raman scattering and FTIR spectroscopy.

Synthesis and characterisation of N-gene targeted NIR-II fluorescent probe for selective localisation of SARS-CoV-2.

Tracking the viral progression of SARS-CoV-2 in COVID-19 infected body tissues is an emerging need of the current pandemic. Imaging at near infrared second biological window (NIR-II) offers striking benefits over the other technologies to explore deep-tissue information. Here we design, synthesise and characterise a molecular probe that selectively targets the N-gene of SARS-CoV-2. Highly specific antisense oligonucleotides (ASOs) were conjugated to lead sulfide quantum dots using a UV-triggered thiol-ene click chemistry for the recognition of viral RNA. Our ex vivo imaging studies demonstrated that the probe exhibits aggregation induced NIR-II emission only in presence of SARS-CoV-2 RNA which can be attributed to the efficient hybridisation of the ASOs with their target RNA strands.

Duplex Shiny app quantification of the sepsis biomarkers C-reactive protein and interleukin-6 in a fast quantum dot labeled lateral flow assay.

Fast point-of-care (POC) diagnostics represent an unmet medical need and include applications such as lateral flow assays (LFAs) for the diagnosis of sepsis and consequences of cytokine storms and for the treatment of COVID-19 and other systemic, inflammatory events not caused by infection. Because of the complex pathophysiology of sepsis, multiple biomarkers must be analyzed to compensate for the low sensitivity and specificity of single biomarker targets. Conventional LFAs, such as gold nanoparticle dyed assays, are limited to approximately five targets-the maximum number of test lines on an assay. To increase the information obtainable from each test line, we combined green and red emitting quantum dots (QDs) as labels for C-reactive protein (CRP) and interleukin-6 (IL-6) antibodies in an optical duplex immunoassay. CdSe-QDs with sharp and tunable emission bands were used to simultaneously quantify CRP and IL-6 in a single test line, by using a single UV-light source and two suitable emission filters for readout through a widely available BioImager device. For image and data processing, a customized software tool, the MultiFlow-Shiny app was used to accelerate and simplify the readout process. The app software provides advanced tools for image processing, including assisted extraction of line intensities, advanced background correction and an easy workflow for creation and handling of experimental data in quantitative LFAs. The results generated with our MultiFlow-Shiny app were superior to those generated with the popular software ImageJ and resulted in lower detection limits. Our assay is applicable for detecting clinically relevant ranges of both target proteins and therefore may serve as a powerful tool for POC diagnosis of inflammation and infectious events.

Sensitive and Simultaneous Detection of SARS-CoV-2-Specific IgM/IgG Using Lateral Flow Immunoassay Based on Dual-Mode Quantum Dot Nanobeads.

A rapid and accurate method for detection of virus (SARS-CoV-2)-specific antibodies is important to contain the 2019 coronavirus disease (COVID-19) outbreak, which is still urgently needed. Here, we develop a colorimetric-fluorescent dual-mode lateral flow immunoassay (LFIA) biosensor for rapid, sensitive, and simultaneous detection of SARS-CoV-2-specific IgM and IgG in human serum using spike (S) protein-conjugated SiO2@Au@QD nanobeads (NBs) as labels. The assay only needs 1 µL of the serum sample, can be completed within 15 min, and is 100 times more sensitive than the colloidal gold-based LFIA. Two detection modes of our biosensor are available: the colorimetric mode for rapid screening of the patients with suspected SARS-CoV-2 infection without any special instrument and the fluorescent mode for sensitive and quantitative analyses to determine the concentrations of specific IgM/IgG in human serum and detect the infection early and precisely. We validated the proposed method using 16 positive serum samples from patients with COVID-19 and 41 negative samples from patients with other viral respiratory infections. The results demonstrated that combined detection of virus-specific IgM and IgG via SiO2@Au@QD LFIA can identify 100% of patients with SARS-CoV-2 infection with 100% specificity.

Quantum Dot-Conjugated SARS-CoV-2 Spike Pseudo-Virions Enable Tracking of Angiotensin Converting Enzyme 2 Binding and Endocytosis.

The first step of SARS-CoV-2 infection is binding of the spike protein's receptor binding domain to the host cell's ACE2 receptor on the plasma membrane. Here, we have generated a versatile imaging probe using recombinant Spike receptor binding domain conjugated to fluorescent quantum dots (QDs). This probe is capable of engaging in energy transfer quenching with ACE2-conjugated gold nanoparticles to enable monitoring of the binding event in solution. Neutralizing antibodies and recombinant human ACE2 blocked quenching, demonstrating a specific binding interaction. In cells transfected with ACE2-GFP, we observed immediate binding of the probe on the cell surface followed by endocytosis. Neutralizing antibodies and ACE2-Fc fully prevented binding and endocytosis with low nanomolar potency. Importantly, we will be able to use this QD nanoparticle probe to identify and validate inhibitors of the SARS-CoV-2 Spike and ACE2 receptor binding in human cells. This work enables facile, rapid, and high-throughput cell-based screening of inhibitors for coronavirus Spike-mediated cell recognition and entry.

Human virus detection with graphene-based materials.

Our recent experience of the COVID-19 pandemic has highlighted the importance of easy-to-use, quick, cheap, sensitive and selective detection of virus pathogens for the efficient monitoring and treatment of virus diseases. Early detection of viruses provides essential information about possible efficient and targeted treatments, prolongs the therapeutic window and hence reduces morbidity. Graphene is a lightweight, chemically stable and conductive material that can be successfully utilized for the detection of various virus strains. The sensitivity and selectivity of graphene can be enhanced by its functionalization or combination with other materials. Introducing suitable functional groups and/or counterparts in the hybrid structure enables tuning of the optical and electrical properties, which is particularly attractive for rapid and easy-to-use virus detection. In this review, we cover all the different types of graphene-based sensors available for virus detection, including, e.g., photoluminescence and colorimetric sensors, and surface plasmon resonance biosensors. Various strategies of electrochemical detection of viruses based on, e.g., DNA hybridization or antigen-antibody interactions, are also discussed. We summarize the current state-of-the-art applications of graphene-based systems for sensing a variety of viruses, e.g., SARS-CoV-2, influenza, dengue fever, hepatitis C virus, HIV, rotavirus and Zika virus. General principles, mechanisms of action, advantages and drawbacks are presented to provide useful information for the further development and construction of advanced virus biosensors. We highlight that the unique and tunable physicochemical properties of graphene-based nanomaterials make them ideal candidates for engineering and miniaturization of biosensors.