Nanobased Platforms for Diagnosis and Treatment of COVID-19: From Benchtop to Bedside

Human respiratory viral infections are the leading cause of morbidity and mortality around the world. Among the various respiratory viruses, coronaviruses (e.g., SARS-CoV-2) have created the greatest challenge and most frightening health threat worldwide. Human coronaviruses typically infect the upper respiratory tract, causing illnesses that range from common cold-like symptoms to severe acute respiratory infections. Several promising vaccine formulations have become available since the beginning of 2021. Nevertheless, achievement of herd immunity is still far from being realized. Social distancing remains the only effective measure against SARS-CoV-2 infection. Nanobiotechnology enables the design of nanobiosensors. These nanomedical diagnostic devices have opened new vistas for early detection of viral infections. The present review outlines recent research on the effectiveness of nanoplatforms as diagnostic and antiviral tools against coronaviruses. The biological properties of coronavirus and infected host organs are discussed. The challenges and limitations encountered in combating SARS-CoV-2 are highlighted. Potential nanodevices such as nanosensors, nanobased vaccines, and smart nanomedicines are subsequently presented for combating current and future mutated versions of coronaviruses.

Wearable Sweat Biosensors Refresh Personalized Health/Medical Diagnostics

Sweat contains a broad range of critical biomarkers including ions, small molecules, and macromolecules that may indirectly or directly reflect the health status of the human body and thereby help track disease progression. Wearable sweat biosensors enable the collection and analysis of sweat in situ, achieving real-time, continuous, and noninvasive monitoring of human biochemical parameters at the molecular level. This review summarizes the physiological/pathological information of sweat and wearable sweat biosensors. First, the production of sweat pertaining to various electrolytes, metabolites, and proteins is described. Then, the compositions of the wearable sweat biosensors are summarized, and the design of each subsystem is introduced in detail. The latest applications of wearable sweat biosensors for outdoor, hospital, and family monitoring are highlighted. Finally, the review provides a summary and an outlook on the future developments and challenges of wearable sweat biosensors with the aim of advancing the field of wearable sweat monitoring technology.

Single-Layered Graphene/Au-Nanoparticles-Based Love Wave Biosensor for Highly Sensitive and Specific Detection of Staphylococcus aureus Gene Sequences

In this work, a single-layered graphene (SLG)/Au-nanoparticles (NPs)-based Love wave biosensor was prepared for detection of Staphylococcus aureus (S. aureus) gene sequences. The annealing process was proposed to obtain a larger-area interface with ssDNA. The sensitivity was verified by detecting S. aureus gene sequences with a linear detection ranging from 0 to 10 nmol/L, where the limit of detection (LOD) was only 12.4 pg/mL. The stable state of the biosensors based on SLG/Au NPs in the liquid phase could be kept for more than 0.5 h (±0.1°), and the specificity was verified by detecting noncomplementary ssDNA and one- and three-base mismatched ssDNA. The results of our study suggest that a Love wave biosensor based on SLG/Au NPs hold great potential in clinical testing and diagnosis.

An aptamer-based shear horizontal surface acoustic wave biosensor with a CVD-grown single-layered graphene film for high-sensitivity detection of a label-free endotoxin

The thickness of the sensitive layer has an important influence on the sensitivity of a shear horizontal surface acoustic wave (SH-SAW) biosensor with a delay-line structure and lower layer numbers of graphene produce better sensitivity for biological detection. Therefore, a label-free and highly sensitive SH-SAW biosensor with chemical vapor deposition (CVD-)-grown single-layered graphene (SLG) for endotoxin detection was developed in this study. With this methodology, SH-SAW biosensors were fabricated on a 36° Y-90° X quartz substrate with a base frequency of 246.2 MHz, and an effective detection cell was fabricated using acrylic material. To increase the surface hydrophilicity, chitosan was applied to the surface of the SLG film. Additionally, the aptamer was immobilized on the surface of the SLG film by cross-linking with glutaraldehyde. Finally, the sensitivity was verified by endotoxin detection with a linear detection ranging from 0 to 100 ng/mL, and the detection limit (LOD) was as low as 3.53 ng/mL. In addition, the stability of this type of SH-SAW biosensor from the air phase to the liquid phase proved to be excellent and the specificity was tested and verified by detecting the endotoxin obtained from Escherichia coli (E. coli), the endotoxin obtained from Pseudomonas aeruginosa (P. aeruginosa), and aflatoxin. Therefore, this type of SH-SAW biosensor with a CVD-grown SLG film may offer a promising approach to endotoxin detection, and it may have great potential in clinical applications.

Synthesis and electroanalytical behaviour of AgNPs/graphite conductive nano-ink towards biosensing of bacteria genome in human biofluids

Identification of pathogens and diagnosis of infections are imperative health challenges, mainly in the case of fastidious bacteria that are hard to grow.

Graphene Oxide-Based Biosensors for Liquid Biopsies in Cancer Diagnosis

Liquid biopsies use blood or urine as test samples, which are able to be continuously collected in a non-invasive manner. The analysis of cancer-related biomarkers such as circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), microRNA, and exosomes provides important information in early cancer diagnosis, tumor metastasis detection, and postoperative recurrence monitoring assist with clinical diagnosis. However, low concentrations of some tumor markers, such as CTCs, ctDNA, and microRNA, in the blood limit its applications in clinical detection and analysis. Nanomaterials based on graphene oxide have good physicochemical properties and are now widely used in biomedical detection technologies. These materials have properties including good hydrophilicity, mechanical flexibility, electrical conductivity, biocompatibility, and optical performance. Moreover, utilizing graphene oxide as a biosensor interface has effectively improved the sensitivity and specificity of biosensors for cancer detection. In this review, we discuss various cancer detection technologies regarding graphene oxide and discuss the prospects and challenges of this technology.

A review on carbon-based materials for heterogeneous sonocatalysis: Fundamentals, properties and applications

Contamination of water resources by refractory organic pollutants is of great environmental and health concern because these compounds are not degraded in the conventional wastewater treatment plants. In recent years, sonocatalytic treatment has been considered as a promising advanced oxidation technique for the acceptable degradation and mineralization of the recalcitrant organic compounds. For this purpose, various sonocatalysts have been utilized in order to accelerate the degradation process. The present review paper provides a summary of published studies on the sonocatalytic degradation of various organic pollutants based on the application of carbon-based catalysts, including carbon nanotubes (CNTs), graphene (GR), graphene oxide (GO), reduced graphene oxide (rGO), activated carbon (AC), biochar (BC), graphitic carbon nitride (g-C₃N₄), carbon doped materials, buckminsterfullerene (C60) and mesoporous carbon. The mechanism of sonocatalytic degradation of different organic compounds by the carbon-based sonocatalysts has been well assessed based on the literature. Moreover, the details of experimental conditions such as sonocatalyst dosage, solute concentration, ultrasound power, applied frequency, initial pH and reaction time related to each study have also been discussed in this review. Finally, concluding remarks as well as future challenges in this research field regarding new areas of study are also discussed and recommended.

Impact of nano-morphology, lattice defects and conductivity on the performance of graphene based electrochemical biosensors

Diverse properties of graphenic materials have been extensively explored to determine properties that make good electrochemical nanomaterial-based biosensors. These are reviewed by critically examining the influence of graphene nano-morphology, lattice defects and conductivity. Stability, reproducibility and fabrication are discussed together with sensitivity and selectivity. We provide an outlook on future directions for building efficient electrochemical biosensors.

Graphdiyne-Based One-Step DNA Fluorescent Sensing Platform for the Detection of Mycobacterium tuberculosis and Its Drug-Resistant Genes

The accurate and early detection of Mycobacterium tuberculosis (Mtb) is of great significance for the clinical diagnosis and treatment of tuberculosis. In this work, we report a facile method for the controllable synthesis of a novel few-layered two-dimensional graphdiyne nanosheet (GDY NS) with a thickness of only ∼0.9 nm via an electrochemical lithium-intercalation strategy, which possesses a prominent fluorescence quenching effect. The few-layered GDY NS with its strong adsorptivity for single-stranded DNA is first proposed as a new fluorescent sensing platform for the real-time detection of DNA with excellent specificity, multiplicity, and superhigh sensitivity (limit of detection as low as 25 pM). This sensing platform can be further applied for the Mtb detection from clinical samples and the identification of drug-resistant mutants with a low background and a high signal-to-noise ratio. Herein, we provide a potential basis for the clinical development of rapid, sensitive, and accurate substitutes for the molecular diagnosis of Mtb and its drug-resistant genes.

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Electrically-transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high-performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical perspective, are summarized for four different groups of analytes: gases, volatile compounds, ions, and biomolecules. The sensing performance is discussed in the context of the molecular design, structure-property relationships, and device fabrication technology. The outlook of challenges and opportunities for 2D nanomaterials for the future development of electrically-transduced sensors is also presented.

Recent advances in graphene-based biosensor technology with applications in life sciences

Graphene's unique physical structure, as well as its chemical and electrical properties, make it ideal for use in sensor technologies. In the past years, novel sensing platforms have been proposed with pristine and modified graphene with nanoparticles and polymers. Several of these platforms were used to immobilize biomolecules, such as antibodies, DNA, and enzymes to create highly sensitive and selective biosensors. Strategies to attach these biomolecules onto the surface of graphene have been employed based on its chemical composition. These methods include covalent bonding, such as the coupling of the biomolecules via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide reactions, and physisorption. In the literature, several detection methods are employed; however, the most common is electrochemical. The main reason for researchers to use this detection approach is because this method is simple, rapid and presents good sensitivity. These biosensors can be particularly useful in life sciences and medicine since in clinical practice, biosensors with high sensitivity and specificity can significantly enhance patient care, early diagnosis of diseases and pathogen detection. In this review, we will present the research conducted with antibodies, DNA molecules and, enzymes to develop biosensors that use graphene and its derivatives as scaffolds to produce effective biosensors able to detect and identify a variety of diseases, pathogens, and biomolecules linked to diseases.

Graphene oxide electrochemistry: the electrochemistry of graphene oxide modified electrodes reveals coverage dependent beneficial electrocatalysis

The modification of electrode surfaces is widely implemented in order to try and improve electron transfer kinetics and surface interactions, most recently using graphene related materials. Currently, the use of 'as is' graphene oxide (GO) has been largely overlooked, with the vast majority of researchers choosing to reduce GO to graphene or use it as part of a composite electrode. In this paper, 'as is' GO is explored and electrochemically characterized using a range of electrochemical redox probes, namely potassium ferrocyanide(II), N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), dopamine hydrochloride and epinephrine. Furthermore, the electroanalytical efficacy of GO is explored towards the sensing of dopamine hydrochloride and epinephrine via cyclic voltammetry. The electrochemical response of GO is benchmarked against pristine graphene and edge plane-/basal plane pyrolytic graphite (EPPG and BPPG respectively) alternatives, where the GO shows an enhanced electrochemical/electroanalytical response. When using GO as an electrode material, the electrochemical response of the analytes studied herein deviate from that expected and exhibit altered electrochemical responses. The oxygenated species encompassing GO strongly influence and dominate the observed voltammetry, which is crucially coverage dependent. GO electrocatalysis is observed, which is attributed to the presence of beneficial oxygenated species dictating the response in specific cases, demonstrating potential for advantageous electroanalysis to be realized. Note however, that crucial coverage based regions are observed at GO modified electrodes, owing to the synergy of edge plane sites and oxygenated species. We report the true beneficial electrochemistry of GO, which has enormous potential to be beneficially used in various electrochemical applications 'as is' rather than be simply used as a precursor to making graphene and is truly a fascinating member of the graphene family.

Nanomaterial-based biosensors for detection of pathogenic virus

Viruses are real menace to human safety that cause devastating viral disease. The high prevalence of these diseases is due to improper detecting tools. Therefore, there is a remarkable demand to identify viruses in a fast, selective and accurate way. Several biosensors have been designed and commercialized for detection of pathogenic viruses. However, they present many challenges. Nanotechnology overcomes these challenges and performs direct detection of molecular targets in real time. In this overview, studies concerning nanotechnology-based biosensors for pathogenic virus detection have been summarized, paying special attention to biosensors based on graphene oxide, silica, carbon nanotubes, gold, silver, zinc oxide and magnetic nanoparticles, which could pave the way to detect viral diseases and provide healthy life for infected patients.

DNA-wrapped multi-walled carbon nanotube modified electrochemical biosensor for the detection of Escherichia coli from real samples

This paper introduces DNA-wrapped multi-walled carbon nanotube (MWCNT)-modified genosensor for the detection of Escherichia coli (E. coli) from polymerase chain reaction (PCR)-amplified real samples while Staphylococcus aureus (S. aureus) was used to investigate the selectivity of the biosensor. The capture probe specifically recognizing E. coli DNA and it was firstly interacted with MWCNTs for wrapping of single-stranded DNA (ssDNA) onto the nanomaterial. DNA-wrapped MWCNTs were then immobilised on the surface of disposable pencil graphite electrode (PGE) for the detection of DNA hybridization. Electrochemical behaviors of the modified PGEs were investigated using Raman spectroscopy and differential pulse voltammetry (DPV). The sequence selective DNA hybridization was determined and evaluated by changes in the intrinsic guanine oxidation signal at about 1.0V by DPV. Numerous factors affecting the hybridization were optimized such as target concentration, hybridization time, etc. The designed DNA sensor can well detect E. coli DNA in 20min detection time with 0.5pmole of detection limit in 30µL of sample volume.

Highly sensitive bacteria quantification using immunomagnetic separation and electrochemical detection of guanine-labeled secondary beads

In this paper, we report the ultra-sensitive indirect electrochemical detection of E. coli O157:H7 using antibody functionalized primary (magnetic) beads for capture and polyguanine (polyG) oligonucleotide functionalized secondary (polystyrene) beads as an electrochemical tag. Vacuum filtration in combination with E. coli O157:H7 specific antibody modified magnetic beads were used for extraction of E. coli O157:H7 from 100 mL samples. The magnetic bead conjugated E. coli O157:H7 cells were then attached to polyG functionalized secondary beads to form a sandwich complex (magnetic bead/E. coli secondary bead). While the use of magnetic beads for immuno-based capture is well characterized, the use of oligonucleotide functionalized secondary beads helps combine amplification and potential multiplexing into the system. The antibody functionalized secondary beads can be easily modified with a different antibody to detect other pathogens from the same sample and enable potential multiplexing. The polyGs on the secondary beads enable signal amplification up to 10⁸ guanine tags per secondary bead (7.5 x 10⁶ biotin-FITC per secondary bead, 20 guanines per oligonucleotide) bound to the target (E. coli). A single-stranded DNA probe functionalized reduced graphene oxide modified glassy carbon electrode was used to bind the polyGs on the secondary beads. Fluorescent imaging was performed to confirm the hybridization of the complex to the electrode surface. Differential pulse voltammetry (DPV) was used to quantify the amount of polyG involved in the hybridization event with tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)3(2+)) as the mediator. The amount of polyG signal can be correlated to the amount of E. coli O157:H7 in the sample. The method was able to detect concentrations of E. coli O157:H7 down to 3 CFU/100 mL, which is 67 times lower than the most sensitive technique reported in literature. The signal to noise ratio for this work was 3. We also demonstrate the use of the protocol for detection of E. coli O157:H7 seeded in waste water effluent samples.

Detection of short oligonucleotide sequences of hepatitis B virus using electrochemical DNA hybridisation biosensor

A novel, sensitive and selective electrochemical hybridisation biosensor was developed for the detection of the hepatitis B virus (HBV) using a manganese(II) complex as electrochemical indicator and a DNA probe-modified carbon paste electrode as the biosensor (DNA/CPE). The results showed that this complex could be accumulated electrochemically the immobilised dsDNA layer rather than in the single-stranded DNA (ssDNA) layer. On the basis of this, the manganese complex was used as an electrochemical hybridisation indicator for the detection of oligonucleotides related to HBV. The hybridisation event was evaluated on the basis of the difference between the reduction signals of the manganese(II) complex with the probe DNA prior to and post hybridisation with a target sequence using a differential pulse mode. Several factors affecting the immobilisation and hybridisation of oligonucleotides as well as the indicator’s accumulation were investigated. Experiments with a noncomplementary and mismatch sequences demonstrated the good selectivity of the biosensor. Using this approach, the HBV target oligonucleotide’s sequence could be quantified over arange from 0.22 ng L

Highly sensitive and synergistic detection of guanine and adenine based on poly(xanthurenic acid)-reduced graphene oxide interface

In order to achieve the large direct electrochemical signals of guanine and adenine, an urgent request to explore novel electrode materials and interfaces has been put forward. In this paper, a poly(xanthurenic acid, Xa)-reduced graphene oxide (PXa-ERGNO) interface, which has rich negatively charged active sites and accelerated electron transfer ability, was fabricated for monitoring the positively charged guanine and adenine. Scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectra, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry were adopted to characterize the morphology and prove the electrochemical properties of the prepared interface. The PXa-ERGNO interface with rich negative charge and large electrode surface area was an excellent sensing platform to prompt the adsorption of the positively charged guanine and adenine via strong π-π* interaction or electrostatic adsorption. The PXa-ERGNO interface exhibited prominent synergistic effect and good electrocatalytic activity for sensitive determination of guanine and adenine compared with sole PXa or ERGNO modified electrode. The sensing platform we built could be further applied in the adsorption and detection of other positively charged biomolecules or aromatic molecules.

Chitosan-graphene oxide based aptasensor for the impedimetric detection of lysozyme

An impedimetric detection of lysozyme (LYS) was performed for the first time in this study at the surface of chitosan-graphene oxide (CHIT-GO) modified sensor based on the specific interaction process between DNA aptamer and its cognate protein, LYS. The amino linked DNA aptamer (APT) was covalently immobilized without using any chemical agents onto the surface of pencil graphite electrode (PGE). These PGEs are inexpensive and simple to use, and thus, they can be furtherly developed for a single-use application in a portable protein chip device. The electrochemical impedance spectroscopy (EIS) technique was used herein to analyze (i) the surface characterization of unmodified PGE and CHIT-GO modified PGE, and also (ii) the interaction between APT and LYS. The limit of detection (DL) was found as 0.38 μg/mL (equals to 28.53 nM). This impedimetric LYS aptasensor exhibited a higher selectivity toward thrombin and bovine serum albumin, even in the mixture samples.

Amplified impedimetric aptasensor based on gold nanoparticles covalently bound graphene sheet for the picomolar detection of ochratoxin A

An amplified electrochemical impedimetric aptasensor for ochratoxin A (OTA) was developed with picomolar sensitivity. A facile route to fabricate gold nanoparticles covalently bound reduced graphene oxide (AuNPs-rGO) resulted in a large number of well-dispersed AuNPs on graphene sheets with tremendous binding sites for DNA, since the single rGO sheet and each AuNP can be loaded with hundreds of DNA strands. An aptasensor with sandwich model was fabricated which involved thiolated capture DNA immobilized on a gold electrode to capture the aptamer, then the sensing interface was incubated with OTA at a desired concentration, followed by AuNPs-rGO functionalized reporter DNA hybridized with the residual aptamers. By exploiting the AuNPs-rGO as an excellent signal amplified platform, a single hybridization event between aptamer and reporter DNA was translated into more than 10(7) redox events, leading to a substantial increase in charge-transfer resistance (Rct) by 7~ orders of magnitude compared with that of the free aptamer modified electrode. Such designed aptasensor showed a decreased response of Rct to the increase of OTA concentrations over a wide range of 1 pg mL(-1)-50 ng mL(-1) and could detect extremely low OTA concentration, namely, 0.3 pg mL(-1) or 0.74 pM, which was much lower than that of most other existed impedimetric aptasensors. The signal amplification platform presented here would provide a promising model for the aptamer-based detection with a direct impedimetric method.

Synthesis and characterization of water-insoluble statistical copolymer and its application in the development of electrochemical DNA sensor

Water-insoluble statistical copolymer was synthesized by copolymerization of methyl methacrylate (MMA) with 2-(dimethylamino)ethyl methacrylate (DMA) via group transfer polymerization (GTP). The DMA residues of the precursor P(MMA-co-DMA) statistical copolymer were then quaternized by reacting with methyl iodide under mild conditions to get well-defined P(MMA-co-QDMA) cationic copolymer. Then, P(MMA-co-QDMA) copolymer was successfully used for surface modification of pencil graphite electrode (PGE) to develop a disposable DNA sensor. This P(MMA-co-QDMA) copolymer modified electrode (q-PGE) was examined for electrochemical monitoring of DNA by using differential pulse voltammetry (DPV) in contrast to unmodified one. The effect of both DNA concentration and sonication time was also examined based on the response of q-PGE. The detection limit was calculated to be 8.06 μg/mL at q-PGE. Electrochemical impedance spectroscopy (EIS) was used for the characterization of the surface modification of q-PGE and consequently, the results were found to be in good agreement with the voltammetric measurements.