Semiconductor quantum dots in photoelectrochemical sensors from fabrication to biosensing applications.

Semiconductor quantum dots (QDs) are a promising class of nanomaterials for developing new photoelectrodes and photoelectrochemistry systems for energy storage, transfer, and biosensing applications. These materials have unique electronic and photophysical properties and can be used as optical nanoprobes in displays, biosensors, imaging, optoelectronics, energy storage and energy harvesting. Researchers have recently been exploring the use of QDs in photoelectrochemical (PEC) sensors, which involve exciting a QD-interfaced photoactive material with a flashlight source and generating a photoelectrical current as an output signal. The simple surface properties of QDs also make them suitable for addressing issues related to sensitivity, miniaturization, and cost-effectiveness. This technology has the potential to replace current laboratory practices and equipment, such as spectrophotometers, used for testing sample absorption and emission. Semiconductor QD-based PEC sensors offer simple, fast, and easily miniaturized sensors for analyzing a variety of analytes. This review summarizes the various strategies for interfacing QD nanoarchitectures for PEC sensing, as well as their signal amplification. PEC sensing devices, particularly those used for the detection of disease biomarkers, biomolecules (glucose, dopamine), drugs, and various pathogens, have the potential to revolutionize the biomedical field. This review discusses the advantages of semiconductor QD-based PEC biosensors and their fabrication methods, with a focus on disease diagnostics and the detection of various biomolecules. Finally, the review provides prospects and considerations for QD-based photoelectrochemical sensor systems in terms of their sensitivity, speed, and portability for biomedical applications.

Biosensors for detecting viral and bacterial infections using host biomarkers: a review.

Viral and bacterial infections commonly occur by their transmission through air, contaminated food, water, body fluids or physical contact from person to person. They rapidly spread among the population causing millions of deaths worldwide. One of the major challenges in the diagnosis of infection is differential diagnosis of viral from bacterial infections. Constant viral mutations, reassortment and recombination give rise to the emergence of new and diverse viral populations which makes the diagnosis difficult. Antibiotics prescribed for patients suffering from viral infections are ineffective and a contributing factor to bacterial antibiotic resistance. Evaluating the existing biosensing platforms for early diagnosis of the bacterial etiology of infections enables researchers and clinicians to differentially diagnose viral infections. Over the last decade, many biosensors have been developed to detect a wide range of bacterial and viral markers and reduce the costs for healthcare. There has been considerable interest in finding diagnostic and prognostic biomarkers that can be detected in blood and predict bacterial and viral infections. This review provides an overview on the existing biosensor technology platforms for host biomarker detection that can be applied for differential diagnosis of viral and bacterial infections, as well as recommended considerations and future prospects of viral/bacterial infection detection technology.

In vitro HER2 protein-induced affinity dissociation of carbon nanotube-wrapped anti-HER2 aptamers for HER2 protein detection.

A new in vitro assay was developed to detect human epidermal growth factor receptor 2 (HER2) protein, based on affinity dissociation of carbon nanotube (CNT)-wrapped anti-HER2 ssDNA aptamers. First, we selected an anti-HER2 ssDNA aptamer (H2) using an in vitro serial evolution of ligands by an exponential enrichment (SELEX) process. Then the fluorescently labelled H2 ssDNAs were tightly packed on CNTs that had previously been coupled with magnetic microbeads (MBs), forming MB-CNT-H2 hybrids. The loading capacity of these MB-CNTs heterostructures (2.8 × 10(8)) was determined to be 0.025 to 3.125 µM of H2. HER2 protein-induced H2 dissociation occurred from MB-CNT-H2 hybrids, which was specifically induced by the target HER2 protein, with a dissociation constant (Kd) of 270 nM. The stoichiometric affinity dissociation ratio with respect to H2-to-HER2 protein was shown to be approximately 1 : 1. Our results demonstrated that the developed assay can be an effective approach in detecting native forms of disease biomarkers in free solutions or in biological samples, for accurate diagnosis.

Mono-segment fixation of thoracolumbar burst fractures.

OBJECT: To investigate what benefits can be derived from a shorter construct length in the pedicle screw based surgical treatment of thoracolumbar burst fracture (TLBF). METHODS: A retrospective analysis was performed of clinical notes and radiology for patients who underwent surgical fixation of TLBFs between 2007 and 2012 in a single UK institution. Constructs either fixed the vertebra above the fracture to the vertebra below (short segment fixation - SSF) or fixed the vertebra above to the relatively well-preserved pedicles and inferolateral portions of the bodies of the fractured vertebra (mono-segment fixation - MSF). 11 patients in each group were included and length of operation, postoperative opiate use, time to mobilisation and length of hospital stay were recorded. Anterior vertebral height loss (AVHL) was measured from sagittal reconstructions of CT imaging and lateral radiographs. RESULTS: The mean operation time was 169 ± 10.4 min in the MSF group compared to 227 ± 13.3 minin the SSF group (p = 0.0028). Mean postoperative opiate use was 50.4 ± 17.9 mg in the MSF group compared to 126.6 ± 64.6 mgs in the SSF group (p = 0.3088, ns). Mean time to mobilisation was 1.3 ± 0.2 in the MSF group and 3.4 ± 1.3 in the SSF group (p = 0.1031, ns). There were no significant differences in progression of anterior vertebral height loss or hospital stay between the two groups. CONCLUSIONS: MSF for TLBFs is associated with shorter operative times than SSF. Strong trends are also demonstrated to quicker mobilisation, and lower opiate use. These advantages of a shorter construct length may result in cost saving and echo the advantages claimed by others for reducing spinal exposure in minimally invasive spinal surgery.

The role of CT body scans in the investigation of patients with newly diagnosed brain tumours.

OBJECTIVE: In the UK approximately 4000 patients are diagnosed with brain tumours each year. Many patients undergo CT scans of the chest, abdomen and pelvis as part of the investigation of such tumours. We aimed to determine the value of CT body scans in patients with newly diagnosed brain tumours. METHODS: We retrospectively reviewed the minutes of our neuro-oncology multidisciplinary team (MDT) meetings over a 12-month period to identify patients with a new radiological diagnosis of a brain tumour. Patients were divided into groups based on radiological diagnosis. Histology results were obtained for patients who underwent surgery. Results of CT body scans were obtained. RESULTS: A total of 261 patients were identified. Sixty percent had radiological primary brain tumours and 40% had secondary brain tumours. Concordance between radiological and histological diagnoses was high (97% for radiological primary brain tumours, and 83% for radiological secondary brain tumours). CT body scans demonstrated primary lesions in 90% of radiological secondary brain tumours. Thirty-four percent of patients with a radiological diagnosis of primary brain tumour underwent CT body scans. The majority of these scans were normal (78%). CONCLUSION: The ability of a specialist neuro-oncology MDT to correctly identify primary and secondary brain tumours on initial imaging is high. If the radiological diagnosis is of a secondary brain tumour, then CT body scans are essential. If the radiological diagnosis is of a primary brain tumour, then CT scans of the body are likely to add little to patient management.

Biosensors for detection of airborne pathogenic fungal spores: a review.

The excessive presence of airborne fungal spores presents major concerns with potential adverse impacts on public health and food safety. These spores are recognized as pathogens and allergens prevalent in both outdoor and indoor environments, particularly in public spaces such as hospitals, schools, offices and hotels. Indoor environments pose a heightened risk of pulmonary diseases due to continuous exposure to airborne fungal spore particles through constant inhalation, especially in those individuals with weakened immunity and immunocompromised conditions. Detection methods for airborne fungal spores are often expensive, time-consuming, and lack sensitivity, making them unsuitable for indoor/outdoor monitoring. However, the emergence of micro-nano biosensor systems offers promising solutions with miniaturized designs, nanomaterial integration, and microfluidic systems. This review provides a comprehensive overview of recent advancements in bio-nano-sensor system technology for detecting airborne fungal spores, while also discussing future trends in biosensor device development aimed at achieving rapid and selective identification of pathogenic airborne fungi.

AuAgCu trimetallic nanoparticles based alloy: an advanced electrocatalyst for hydrogen evolution reaction in alkaline media.

Hydrogen production via cost-effective electrochemical water splitting is one of the most promising approaches to confront the energy crisis and to obtain clean fuels with high energy density. To address this concern, herein, we developed a simple one-step synthesis method for creating an AuAgCu trimetallic alloy using aspirin as a capping agent. This alloy shows potential for efficient electrocatalyst for hydrogen evolution reaction. The trimetallic nanoparticles based alloy exhibit an equiaxed grain-like morphology and a face-centred cubic phase. In HER experiments using a 1 M KOH electrolyte, the AuAgCu alloy shows nearly negligible overpotential compared to mono- and bimetallic catalysts, and the Tafel slope was 32.7 mV dec-1, which is the lowest ever achieved for alloy-based electrocatalysts and extremely close to a commercially available Pt/C with high stability for 21 days and no decrease in current density in alkaline media. Besides, with excellent HER activity and stability, the trimetallic AuAgCu-modified electrode possessed significant durability for over 1000 cycles in the selected range of potential from 0.5 to 0.8 V at different scan rates from 1 to 100 mV s-1. This simple, cost-effective and environmentally friendly methodology can pave the way for the exploitation of mixed metal alloy-based electrocatalysts not only for water splitting but also for other applications, such as fuel cells, lithium-ion batteries and supercapacitors.

Graphene-interfaced flexible and stretchable micro-nano electrodes: from fabrication to sweat glucose detection.

Flexible and stretchable wearable electronic devices have received tremendous attention for their non-invasive and personal health monitoring applications. These devices have been fabricated by integrating flexible substrates and graphene nanostructures for non-invasive detection of physiological risk biomarkers from human bodily fluids, such as sweat, and monitoring of human physical motion tracking parameters. The extraordinary properties of graphene nanostructures in fully integrated wearable devices have enabled improved sensitivity, electronic readouts, signal conditioning and communication, energy harvesting from power sources through electrode design and patterning, and graphene surface modification or treatment. This review explores advances made toward the fabrication of graphene-interfaced wearable sensors, flexible and stretchable conductive graphene electrodes, as well as their potential applications in electrochemical sensors and field-effect-transistors (FETs) with special emphasis on monitoring sweat biomarkers, mainly in glucose-sensing applications. The review emphasizes flexible wearable sweat sensors and provides various approaches thus far employed for the fabrication of graphene-enabled conductive and stretchable micro-nano electrodes, such as photolithography, electron-beam evaporation, laser-induced graphene designing, ink printing, chemical-synthesis and graphene surface modification. It further explores existing graphene-interfaced flexible wearable electronic devices utilized for sweat glucose sensing, and their technological potential for non-invasive health monitoring applications.

Intradural extramedullary meningeal melanocytoma: a case report and literature review.

Primary meningeal melanocytomas are extremely rare, benign tumours arising from the leptomeninges. While they are considered to be benign lesions, there is potential for their growth and transformation into malignant melanomas. They are commonly found in the cervical spine, with a decreased incidence in the thoracic and lumbar regions. We present a case report of a 56-year-old man who presented to our unit with a 4-month history of lower limb weakness and a sensory level at T6. Magnetic resonance imaging shows an intradural extramedullary tumour. The patient underwent a thoracic debulking of the lesion with neurophysiological monitoring. Histopathology confirmed the diagnosis of melanocytoma of meningeal origin, with a low mitotic count. Our patient recovered well post-operatively with no complications. Surgical resection is an effective method to manage this tumour; however, adjuvant radiotherapy is advised due to the risk of recurrence and malignant transformation.

Electrophoretic Fabrication of ZnO/CuO and ZnO/CuO/rGO Heterostructures-based Thin Films as Environmental Benign Flexible Electrode for Supercapacitor.

Sustainable fabrication of flexible hybrid supercapacitor electrodes is extensively investigated during the current era to solve global energy problems. Herein, we used a cost-effective and efficient electrophoretic deposition (EPD) approach to fabricate a hybrid supercapacitor electrode. ZnO/CuO and ZnO/CuO/rGO heterostructure were prepared by sol-gel synthesis route and were electrophoretically deposited on indium tin oxide (ITO) substrate as a thin uniform layer using 1 V for 20 min at 50 mV/s. ZnO/CuO and ZnO/CuO/rGO heterostructure coated ITOs were then employed as the working electrode in a three-electrode setup for supercapacitor measurements. The fabricated electrodes have been investigated by Galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) to study their charge storage properties. ZnO/CuO revealed a specific capacitance of 1945 F g-1 at 2 mV/s and 999 F g-1 at 5 A g-1. However, an increased specific capacitance of 2305 F g-1 was measured for ZnO/CuO/rGO heterostructure at 2 mV/s and 1235 F g-1 at 5 A g-1. The lower internal resistance was observed for ZnO/CuO/rGO heterostructure, indicating good conductivity of the electrode material. Thus, the overall results of the current study suggest that EPD-assisted ZnO/CuO/rGO heterostructure hybrid electrode possess a substantial potential for energy storage as a supercapacitor.

Phyto-synthesized facile Pd/NiOPdO ternary nanocomposite for electrochemical supercapacitor applications.

Sustainable and effective electrochemical materials for supercapacitors are greatly needed for solving the global problems of energy storage. In this regard, a facile nanocomposite of Pd/NiOPdO was synthesized using foliar phyto eco-friendly agents and examined as an electrochemical electrode active material for supercapacitor application. The nanocomposite showed a mixed phase of a ternary nano metal oxide phase of rhombohedral NiO and tetragonal PdO confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and XPS (X-rays photoelectron spectroscopy). The optical (direct) energy value of the synthesized nanocomposite was 3.14 eV. The phyto-functionalized nanocomposite was studied for electrochemical supercapacitor properties and revealed a specific capacitance of 88 F g-1 and low internal resistance of 0.8 Ω. The nanoscale and phyto organic species functionalized nanocomposite exhibited enhanced electrochemical properties for supercapacitor application.

Probing chemical induced cellular stress by non-Faradaic electrochemical impedance spectroscopy using an Escherichia coli capacitive biochip.

A new capacitive biochip was developed using carboxy-CNT activated gold interdigitated (GID) capacitors immobilized with E. coli cells for the detection of cellular stress caused by chemicals. Here, acetic acid, H(2)O(2) and NaCl were employed as model chemicals to test the biochip and monitored the responses under AC electrical field by non-Faradaic electrochemical impedance spectroscopy (nFEIS). The electrical properties of E. coli cells under different stresses were studied based on the change in surface capacitance as a function of applied frequency (300-600 MHz) in a label-free and noninvasive manner. The capacitive response of the E. coli biochip under normal conditions exhibited characteristic dispersion peaks at 463 and 582 MHz frequencies. Deformation of these signature peaks determined the toxicity of chemicals to E. coli on the capacitive biochip. The E. coli cells were sensitive to, and severely affected by 166-498 mM (1-3%) acetic acid with declined capacitance responses. The E. coli biochip exposed to H(2)O(2) exhibited adaptive responses at lower concentrations (<2%), while at a higher level (882 mM, 3%), the capacitance response declined due to oxidative toxicity in cells. However, E. coli cells were not severely affected by high NaCl levels (513-684 mM, 3-4%) as the cells tend to resist the salt stress. Our results demonstrated that the biochip response at a particular frequency enabled the determination of the severity of the stress imposed by chemicals and it can be potentially applied for monitoring unknown chemicals as an indicator of cytotoxicity.

Iron oxide nanoparticles based magnetic luminescent quantum dots (MQDs) synthesis and biomedical/biological applications: A review.

Combination of quantum dots (QDs) and magnetic nanoparticles (MNPs) as magnetic quantum dots (MQDs) has a broad range of applications as multifunctional nanoscale devices in biological imaging, medical nano-diagnostics and nanomedicine. MQDs derived from iron oxide nanoparticles and QDs possess excellent superparamagnetic and fluorescent properties, respectively making them multifunctional nanoprobes because of their; (a) strong magnetic strength with tunable functionality, such as rapid and simple magnetic separation, (b) intense and stable fluorescence from QDs combined with tunable biological functionality upon QDs' bio-activation, and (c) imaging/visualization by simple ultraviolet light exposure. These excellent features of MQD nanoprobes enable them to be used for magnetic resonance imaging (MRI) as contrast agents, nano-diagnostic systems for Point-of-Care (PoC) disease diagnosis, theranostics nanorobots and in other bio-medical applications. Most of MQDs are derived from iron based MNPs because of their abundancy, superparamagnetic properties, low cost and easy to synthesize. In this review, we present different methods employed for chemical synthesis of MQDs derived from iron oxide MNPs, their major chemical compositions and important parameters, such as precursor compositions, quantum yield and magnetic properties. The review also summarizes the most frequently used MQDs in applications such as bio-imaging, drug delivery, biosensor platforms and finally ends with future prospects and considerations for MQDs in biomedical applications.

Graphene and carbon nanotubes interfaced electrochemical nanobiosensors for the detection of SARS-CoV-2 (COVID-19) and other respiratory viral infections: A review.

Recent COVID-19 pandemic has claimed millions of lives due to lack of a rapid diagnostic tool. Global scientific community is now making joint efforts on developing rapid and accurate diagnostic tools for early detection of viral infections to preventing future outbreaks. Conventional diagnostic methods for virus detection are expensive and time consuming. There is an immediate requirement for a sensitive, reliable, rapid and easy-to-use Point-of-Care (PoC) diagnostic technology. Electrochemical biosensors have the potential to fulfill these requirements, but they are less sensitive for sensing viruses/viral infections. However, sensitivity and performance of these electrochemical platforms can be improved by integrating carbon nanostructure, such as graphene and carbon nanotubes (CNTs). These nanostructures offer excellent electrical property, biocompatibility, chemical stability, mechanical strength and, large surface area that are most desired in developing PoC diagnostic tools for detecting viral infections with speed, sensitivity, and cost-effectiveness. This review summarizes recent advancements made toward integrating graphene/CNTs nanostructures and their surface modifications useful for developing new generation of electrochemical nanobiosensors for detecting viral infections. The review also provides prospects and considerations for extending the graphene/CNTs based electrochemical transducers into portable and wearable PoC tools that can be useful in preventing future outbreaks and pandemics.

Label-free RNA aptamer-based capacitive biosensor for the detection of C-reactive protein.

In this study, we report a novel aptamer-based capacitive label-free biosensor for monitoring transducing aptamer-protein recognition events, based on charge distribution under the applied frequency by non-Faradaic impedance spectroscopy (NFIS). This approach to capacitive biosensors is reported for the first time in this study, is reagent-less in processing and is developed using gold interdigitated (GID) capacitor arrays functionalized with synthetic RNA aptamers. The RNA atpamers served as biorecognition elements for C-reactive protein (CRP), a biomarker for cardiovascular disease risk (CVR). The signal is generated as a result of the change in relative capacitance occurring as a result of the formation of an RNA-CRP complex on GID capacitors with the applied AC electrical frequency (50-350 MHz). The dispersion peak of the capacitance curve was dependent on the CRP concentration and tends to shift toward lower frequencies, accompanied by the increase in relaxation time due to the increased size of the aptamer-CRP complex. The dissociation constant (K(d)) calculated from the non-linear regression analysis of the relative capacitance change with the applied frequency showed that strong binding of CRP occurred at 208 MHz (K(d) = 1.6 microM) followed by 150 MHz (K(d) = 4.2 microM) and 306 MHz (K(d) = 3.4 microM) frequencies. The dynamic detection range for CRP is determined to be within 100-500 pg ml(-1). Our results demonstrates the behavior of an RNA-protein complex on GID capacitors under an applied electric field, which can be extended to other pairs of affinity biomolecules as well as for the development of electrical biosensor systems for different applications, including the early diagnosis of diseases.

A Hand-Held Point-of-Care Biosensor Device for Detection of Multiple Cancer and Cardiac Disease Biomarkers Using Interdigitated Capacitive Arrays.

This paper presents a hand-held point-of-care device that incorporates a lab-on-a-chip module with interdigitated capacitive biosensors for label-free detection of multiple cancer and cardiovascular disease biomarkers. The developed prototype is comprised of a cartridge incorporating capacitive biodetection sensors, a sensitive capacitive readout electronics enclosed in a hand-held unit, and data analysis software calculating the concentration of biomarkers using previously stored reference database. The capacitive biodetection sensors are made of interdigitated circular electrodes, which are preactivated with single (for detecting one biomarker) or multiple specific antibodies (for detecting multiple disease biomarkers). Detection principle of capacitive biosensor is based on measuring the level of capacitance change between interdigitated electrode pairs induced by the change in dielectric constant due to affinity-based electron exchange in between antibodies/antigens and electrodes. The more antibody-antigens binding occurs, the more capacitance change is measured due to the change in dielectric constant of the capacitance media. The device uses preactivated ready-to-use cartridges embedded with capacitive biosensors with shelf-life of three months under optimal conditions, and is capable of onsite diagnosis and can report the result in less than 30 min. The device is verified with real patient blood samples for six different disease biomarkers.

Low molecular weight heparin versus unfractionated heparin in the management of cerebral venous thrombosis: A systematic review and meta-analysis.

INTRODUCTION: There are two main choices of anti-coagulation in cerebral venous thrombosis: Unfractionated heparin versus low molecular weight heparin. A consensus is yet to be reached regarding which agent is optimal. Therefore the aim of this systematic review and meta-analysis was to identify which agent is most effective in treating CVT. METHODS: Databases Pubmed (MEDLINE), Google Scholar and hand-picked references from papers of interest were reviewed. Studies comparing the use of low molecular weight heparin and unfractionated heparin in adult patients with a confirmed diagnosis of cerebral vein thrombosis were selected. Data was recorded for patient mortality, functional outcome and haemorrhagic complications of therapy. RESULTS: A total of 2761 papers were identified, 74 abstracts were screened, with 5 papers being read in full text and three studies suitable for final inclusion. A total of 179 patients were in the LMWH group and 352 patients were in the UH group. Mortality and functional outcome trended towards favouring LMWH with OR [95% CI] of 0.51 [0.23, 1.10], p = 0.09 and 0.79 [0.49, 1.26] p = 0.32 respectively. There was no difference in extra-cranial haemorrhage rates between either agent with a OR [95% CI] of 1.00 [0.29, 3.52] p = 0.99. CONCLUSION: Trends towards improved mortality and improved functional outcomes were seen in patients treated with LMWH. No result reached statistical significance due to low numbers of studies available for inclusion. There is a need for further large scale randomized trials to definitively investigate the potential benefits of LMWH in the treatment of CVT.

Toxicity evaluation of e-juice and its soluble aerosols generated by electronic cigarettes using recombinant bioluminescent bacteria responsive to specific cellular damages.

Electronic-cigarettes (e-cigarette) are widely used as an alternative to traditional cigarettes but their safety is not well established. Herein, we demonstrate and validate an analytical method to discriminate the deleterious effects of e-cigarette refills (e-juice) and soluble e-juice aerosol (SEA) by employing stress-specific bioluminescent recombinant bacterial cells (RBCs) as whole-cell biosensors. These RBCs carry luxCDABE-operon tightly controlled by promoters that specifically induced to DNA damage (recA), superoxide radicals (sodA), heavy metals (copA) and membrane damage (oprF). The responses of the RBCs following exposure to various concentrations of e-juice/SEA was recorded in real-time that showed dose-dependent stress specific-responses against both the e-juice and vaporized e-juice aerosols produced by the e-cigarette. We also established that high doses of e-juice (4-folds diluted) lead to cell death by repressing the cellular machinery responsible for repairing DNA-damage, superoxide toxicity, ion homeostasis and membrane damage. SEA also caused the cellular damages but the cells showed enhanced bioluminescence expression without significant growth inhibition, indicating that the cells activated their global defense system to repair these damages. DNA fragmentation assay also revealed the disintegration of total cellular DNA at sub-toxic doses of e-juice. Despite their state of matter, the e-juice and its aerosols induce cytotoxicity and alter normal cellular functions, respectively that raises concerns on use of e-cigarettes as alternative to traditional cigarette. The ability of RBCs in detecting both harmful effects and toxicity mechanisms provided a fundamental understanding of biological response to e-juice and aerosols.

Graphene-interfaced electrical biosensor for label-free and sensitive detection of foodborne pathogenic E. coli O157:H7.

E. coli O157:H7 is an enterohemorrhagic bacteria responsible for serious foodborne outbreaks that causes diarrhoea, fever and vomiting in humans. Recent foodborne E. coli outbreaks has left a serious concern to public health. Therefore, there is an increasing demand for a simple, rapid and sensitive method for pathogen detection in contaminated foods. In this study, we developed a label-free electrical biosensor interfaced with graphene for sensitive detection of pathogenic bacteria. This biosensor was fabricated by interfacing graphene with interdigitated microelectrodes of capacitors that were biofunctionalized with E. coli O157:H7 specific antibodies for sensitive pathogenic bacteria detection. Here, graphene nanostructures on the sensor surface provided superior chemical properties such as high carrier mobility and biocompatibility with antibodies and bacteria. The sensors transduced the signal based on changes in dielectric properties (capacitance) through (i) polarization of captured cell-surface charges, (ii) cells' internal bioactivity, (iii) cell-wall's electronegativity or dipole moment and their relaxation and (iv) charge carrier mobility of graphene that modulated the electrical properties once the pathogenic E. coli O157:H7 captured on the sensor surface. Sensitive capacitance changes thus observed with graphene based capacitors were specific to E. coli O157:H7 strain with a sensitivity as low as 10-100 cells/ml. The proposed graphene based electrical biosensor provided advantages of speed, sensitivity, specificity and in-situ bacterial detection with no chemical mediators, represents a versatile approach for detection of a wide variety of other pathogens.

Nanomaterial resistant microorganism mediated reduction of graphene oxide.

In this study, soil bacteria were isolated from nanomaterials (NMs) contaminated pond soil and enriched in the presence of graphene oxide (GO) in mineral medium to obtain NMs resistant bacteria. The isolated resistant bacteria were biochemically and genetically identified as Fontibacillus aquaticus. The resistant bacteria were allowed to interact with engineered GO in order to study the biotransformation in GO structure. Raman spectra of GO extracted from culture medium revealed decreased intensity ratio of ID/IG with subsequent reduction of CO which was consistent with Fourier transform infrared (FTIR) results. The structural changes and exfoliatied GO nanosheets were also evident from transmission electron microscopy (TEM) images. Ultraviolet-visible spectroscopy, high resolution X-ray diffraction (XRD) and current-voltage measurements confirmed the reduction of GO after the interaction with resistant bacteria. X-ray photoelectron spectroscopy (XPS) analysis of biotransformed GO revealed reduction of oxygen-containing species on the surface of nanosheets. Our results demonstrated that the presented method is an environment friendly, cost effective, simple and based on green approaches for the reduction of GO using NMs resistant bacteria.