Biosensing platform based on graphene oxide via self-assembly induced by synergic interactions

Investigation and comparison of graphene nanoribbon and carbon nanotube based SARS-CoV-2 detection sensors: An ab initio study

The rapid detection of SARS-CoV-2, the pathogen of the Covid-19 pandemic, is obviously of great importance for stopping the spread of the virus by detecting infected individuals. Here, we report the ab initio analysis results of graphene nanoribbon (GNR) and carbon nanotube (CNT) based SARS-CoV-2 detection sensors which are experimentally demonstrated in the literature. The investigated structures are the realistic molecular models of the sensors that are employing 1-pyrenebutyric acid N-hydroxysuccinimide ester as the antibody linker. Density functional theory in conjunction with non-equilibrium Green's function formalism (DFT-NEGF) is used to obtain the transmission spectra, current-voltage and resistance-voltage characteristics of the sensors before and after the attachment of the SARS-CoV-2 spike protein. The operation mechanism of the GNR and CNT based SARS-CoV-2 sensors are exposed using the transmission spectrum analysis. Moreover, it is observed that GNR based sensor has more definitive detection characteristics compared to its CNT based counterpart.

In silico design of peptides with binding to the receptor binding domain (RBD) of the SARS-CoV-2 and their utility in bio-sensor development for SARS-CoV-2 detection

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected millions of people across the globe and created not only a health emergency but also a financial crisis. This virus attacks the angiotensin-converting enzyme 2 (ACE2) receptor situated on the surface of the host cell membrane. The spike protein of the virus binds to this receptor which is a critical step in infection. A molecule which can specifically stop this binding could be a potential therapeutic agent. In this study, we have tested 12 potential peptides which can bind to the receptor binding domain (RBD) of the spike protein of the virus and thus can potentially inhibit the binding of the latter on ACE2 receptors. These peptides are screened based on their binding with the RBD of the spike protein and aqueous stability, obtained using several atomistic molecular dynamic simulations. The potential of mean force calculation of peptides confirmed their binding to the RBD of the spike protein. Furthermore, two potential peptides were tested for use in a biosensing application for SARS-CoV-2 detection. Two types of biosensing platforms, a graphene sheet and a carbon nano tube (CNT) were tested. The peptides were modified in order to functionalize the graphene and CNT. Based on the interaction between the substrate, peptide and spike protein, the utility of the screened peptide for a given bio sensing platform is discussed and recommended.

The protocol for peptide design and testing for its usage as a sensor.

Flex-GO (Flexible graphene oxide) sensor for electrochemical monitoring lactate in low-volume passive perspired human sweat

In this work, a low volume, sweat lactate sensor functioning on passively expressed eccrine sweat was designed, fabricated and tested in human sweat and its performance was benchmarked against a standard reference; Lactate Plus meter. This novel sensor comprises of graphene oxide (GO) nanosheets integrated into a nanoporous flexible electrode system for low-volume (1-5 μL) ultrasensitive impedance based detection of lactate using non-faradaic electron-ionic charge transfer. Lactate oxidase (LOD) enzyme was immobilized on the surface of GO nanosheets towards developing an affinity biosensor specific to the physiological relevant range (4-80 mM) of lactate in perspired human sweat. Sensing was achieved by measuring impedance changes specific to lactate binding along the GO nanosheet interface using electrochemical impedance spectroscopy. The sensor demonstrated a dynamic range from 1 to 100 mM spiked in synthetic and human sweat with a limit of detection of 1 mM. A specificity study conducted using cortisol expressed in sweat revealed a negative response to the lactate oxidase. Continuous lactate sensing studies were performed during which the sensor was responsive to concentrations of lactate up to 138.6 mM. Correlation of the sensor response with actual lactate concentration (1.3-113.4 mM) was found to be 0.955.

Enhanced Electrochemiluminescence of One-Dimensional Self-Assembled Porphyrin Hexagonal Nanoprisms

In this work, we synthesized the one-dimensional nanostructure of zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP) via a self-assembly technique. Using sodium dodecyl sulfate (SDS) as "soft template", the self-assembled ZnTPyP (SA-ZnTPyP) had the morphology of hexagonal nanoprisms with a uniform size (diameter of 100 nm). The SA-ZnTPyP exhibited remarkably different spectral properties compared to those of the original ZnTPyP. The as-prepared SA-ZnTPyP was used to modify glassy carbon electrodes (GCE), and the electrochemiluminescence (ECL) behaviors of the SA-ZnTPyP/GCE were investigated. The hydrophilic carbon dots (C-dots) could efficiently prevent the dissolution of SA-ZnTPyP in DMF containing 0.1 mol L^-1 TBAP and, simultaneously, could accelerate electron transfer. Therefore, the enhanced ECL was realized by C-dots/SA-ZnTPyP/GCE by using H₂O₂ as co-reactant. This amplification of ECL was further studied by ECL spectroscopies and cyclic voltammetry, and the corresponding mechanism was proposed.

A novel electrochemical DNA biosensor based on a modified magnetic bar carbon paste electrode with Fe3O4NPs-reduced graphene oxide/PANHS nanocomposite

In this study, we have designed a label free DNA biosensor based on a magnetic bar carbon paste electrode (MBCPE) modified with nanomaterial of Fe3O4/reduced graphene oxide (Fe3O4NP-RGO) as a composite and 1- pyrenebutyric acid-N- hydroxysuccinimide ester (PANHS) as a linker for detection of DNA sequences. Probe (BRCA1 5382 insC mutation detection) strands were immobilized on the MBCPE/Fe3O4-RGO/PANHS electrode for the exact incubation time. The characterization of the modified electrode was studied using different techniques such as scanning electron microscopy (SEM), infrared spectroscopy (IR), vibrating sample magnetometer (VSM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry methods. Some experimental parameters such as immobilization time of probe DNA, time and temperature of hybridization process were investigated. Under the optimum conditions, the immobilization of the probe and its hybridization with the target DNA (Complementary DNA) were tested. This DNA biosensor revealed a good linear relationship between ∆Rct and logarithm of the complementary target DNA concentration ranging from 1.0×10(-18)molL(-1) to 1.0×10(-8)molL(-1) with a correlation coefficient of 0.9935 and a detection limit of 2.8×10(-19)molL(-1). In addition, the mentioned biosensor was satisfactorily applied for discriminating of complementary sequences from non-complementary sequences. The constructed biosensor (MBCPE/Fe3O4-RGO/PANHS/ssDNA) with high sensitivity, selectivity, stability, reproducibility and low cost can be used for detection of BRCA1 5382 insC mutation.