Updates on the Biofunctionalization of Gold Nanoparticles for the Rapid and Sensitive Multiplatform Diagnosis of SARS-CoV-2 Virus and Its Proteins: From Computational Models to Validation in Human Samples.

Since the outbreak of the pandemic respiratory virus SARS-CoV-2 (COVID-19), academic communities and governments/private companies have used several detection techniques based on gold nanoparticles (AuNPs). In this emergency context, colloidal AuNPs are highly valuable easy-to-synthesize biocompatible materials that can be used for different functionalization strategies and rapid viral immunodiagnosis. In this review, the latest multidisciplinary developments in the bioconjugation of AuNPs for the detection of SARS-CoV-2 virus and its proteins in (spiked) real samples are discussed for the first time, with reference to the optimal parameters provided by three approaches: one theoretical, via computational prediction, and two experimental, using dry and wet chemistry based on single/multistep protocols. Overall, to achieve high specificity and low detection limits for the target viral biomolecules, optimal running buffers for bioreagent dilutions and nanostructure washes should be validated before conducting optical, electrochemical, and acoustic biosensing investigations. Indeed, there is plenty of room for improvement in using gold nanomaterials as stable platforms for ultrasensitive and simultaneous "in vitro" detection by the untrained public of the whole SARS-CoV-2 virus, its proteins, and specific developed IgA/IgM/IgG antibodies (Ab) in bodily fluids. Hence, the lateral flow assay (LFA) approach is a quick and judicious solution to combating the pandemic. In this context, the author classifies LFAs according to four generations to guide readers in the future development of multifunctional biosensing platforms. Undoubtedly, the LFA kit market will continue to improve, adapting researchers' multidetection platforms for smartphones with easy-to-analyze results, and establishing user-friendly tools for more effective preventive and medical treatments.

Tumor microenvironment-responsive gold nanodendrites for nanoprobe-based single-cell Raman imaging and tumor-targeted chemo-photothermal therapy

Nanodendrite particles (NDs) with densely branched structures and biomimetic architectures have exhibited great promise in tumor therapy owing to their prolonged in vivo circulation time and exceptional photothermal efficiency. Nevertheless, traditional NDs are deficient in terms of specific surface modification and targeting tumors, which restricts their potential for broader clinical applications. Here, we developed coronavirus-like gold NDs through a seed-mediated approach and using silk fibroin (SF) as a capping agent. Our results demonstrate that these NDs have a favorable drug-loading capacity (∼65.25%) and light-triggered release characteristics of doxorubicin hydrochloride (DOX). Additionally, NDs functionalized with specific probes exhibited exceptional surface-enhanced Raman scattering (SERS) characteristics, enabling high-sensitivity Raman imaging of unstained single cells. Moreover, these NDs allowed for real-time monitoring of endocytic NDs for over 24 h. Furthermore, ND@DOX conjugated with tumor-targeting peptides exhibited mild hyperthermia, minimal cytotoxicity, and effective targeting towards cancer cells in vitro, as well as responsiveness to the tumor microenvironment (TME) in vivo. These unique properties led to the highest level of synergistic tumor-killing efficiency when stimulated by a near-infrared (NIR) laser at 808 nm. Therefore, our virus-like ND functionalized with SF presents a novel type of nanocarrier that exhibits significant potential for synergistic applications in precision medicine.

Organic Electrochemical Transistors (OECTs): Advancements and Exciting Prospects for Future Biosensing Applications

Over the past few decades, the field of organic electronics has depicted proliferated growth, due to the advantageous characteristics of organic semiconductors, such as tunability through synthetic chemistry, simplicity in processing, cost-effectiveness, and low-voltage operation, to cite a few. Organic electrochemical transistors (OECTs) have recently emerged as a highly promising technology in the area of biosensing and flexible electronics. OECT-based biosensors are capable of sensing brain activities, tissues, monitoring cells, hormones, DNAs, and glucose. Sensitivity, selectivity, and detection limit are the key parameters adopted for measuring the performance of OECT-based biosensors. This article highlights the advancements and exciting prospects of OECTs for future biosensing applications, such as cell-based biosensing, chemical sensing, DNA/ribonucleic acid (RNA) sensing, glucose sensing, immune sensing, ion sensing, and pH sensing. OECT-based biosensors outperform other conventional biosensors because of their excellent biocompatibility, high transconductance, and mixed electronic-ionic conductivity. At present, OECTs are fabricated and characterized in millimeter and micrometer dimensions, and miniaturizing their dimensions to nanoscale is the key challenge for utilizing them in the field of nanobioelectronics, nanomedicine, and nanobiosensing.

Nanomaterials and Biosensing Technology for the SARS-CoV-2 Detection

The outbreak of corona virus disease 2019 (COVID-19) has aroused great attention around the world. SARS-CoV-2 possesses characteristics of faster transmission, immune escape, and occult transmission by many mutation, which caused still grim situation of prevention and control. Early detection and isolation of patients are still the most effective measures at present. So, there is an urgent need for new rapid and highly sensitive testing tools to quickly identify infected patients as soon as possible. This review briefly introduces general characteristics of SARS-CoV-2, and provides recentl overview and analysis based on different detection methods for nucleic acids, antibodies, antigens as detection target. Novel nano-biosensors for SARS-CoV-2 detection are analyzed based on optics, electricity, magnetism, and visualization. In view of the advantages of nanotechnology in improving detection sensitivity, specificity and accuracy, the research progress of new nano-biosensors is introduced in detail, including SERS-based biosensors, electrochemical biosensors, magnetic nano-biosensors and colorimetric biosensors. Functions and challenges of nano-materials in construction of new nano-biosensors are discussed, which provides ideas for the development of various coronavirus biosensing technologies for nanomaterial researchers.

Design and Development of Nanoscale Aptasensors for Viral Diagnostics

Viral infection may be a serious threat for human beings. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly transmissible virus causing coronavirus disease 2019 (COVID-19) in humans and creating a universal pandemic outbreak. The current methods for detection of SARS-CoV-2 include real-time reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and loop-mediated isothermal amplification (LAMP). Though the methods are widely used for the diagnosis of COVID-19, they too have their limitations such as time-consuming process, sophisticated instrumental setup, which requires highly skilled personnel for operation, and prevalence of false positive/negative reports. Therefore, there is a pressing need to develop alternative tools such as point-of-care testing (POCT) devices to detect SARS-CoV-2 rapidly, accurately, and user-friendly. Here, the authors propose a one-step diagnostic method using aptamer-based sensing technology. The intended design of aptamer-based biosensors (also known as aptasensors) utilizes the optical properties of gold nanoparticles (AuNP) conjugated with angiotensin-converting enzyme-2 (ACE-2) aptamers targeting SARS-CoV-2 using lateral flow assay (LFA). This study leads to the development of portable nanoscale aptasensors for viral diagnostics. © 2022 by the authors.

AuNP-Coated Cotton as VOC Sensor for Disease Detection from Breath

The COVID-19 pandemic outbreak, declared in March 2020, has led to several behavioral changes in the general population, such as social distancing and mask usage among others. Furthermore, the sanitary emergency has stressed health system weaknesses in terms of disease prevention, diagnosis, and cure. Thus, smart technologies allowing for early and quick detection of diseases are called for. In this framework, the development of point-of-care devices can provide new solutions for sanitary emergencies management. This work focuses on the development of useful tools for early disease diagnosis based on nanomaterials on cotton substrates, to obtain a low-cost and easy-to-use detector of breath volatiles as disease markers. Specifically, we report encouraging experimental results concerning acetone detection through impedance measurements. Such findings can pave the way to the implementation of VOCs (Volatile Organic Compounds) sensors into smart and user friendly diagnostic devices. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Metamaterial enhanced novel plasmonic biosensor for specific detection of SARS-CoV-2 spike protein

In this study, we theoretically propose a surface plasmon resonance (SPR) biosensor composed of a plasmonic gold film, double negative (DNG) metamaterial, graphene-MoS2-COOH Van der Waals heterostructures and gold nanoparticles (Au NPs). We use a novel scheme of Goos-Hanchen (GH) shift to study the biosensing performances of our proposed plasmonic biosensor. The calculation results show that, both an extreme low reflectivity of 8.52×10-10 and significantly enhanced GH sensitivity of 2.1530×107 μm/RIU can be obtained, corresponding to the optimal configuration: 32 nm Au film/120 nm metamaterial/4-layer graphene/4-layer MoS2-COOH. In addition, there is a theoretically excellent linear response between the concentration of target analytes (SARS-CoV-2 and S protein) and the change in differential GH shift. Our proposed biosensor promises to be a useful tool for performing the novel coronavirus detection. © 2023 SPIE.

Using low-cost disposable immunosensor based on flexible PET screen-printed electrode modified with carbon black and gold nanoparticles for sensitive detection of SARS-CoV-2.

To help meet the global demand for reliable and inexpensive COVID-19 testing and environmental analysis of SARS-CoV-2, the present work reports the development and application of a highly efficient disposable electrochemical immunosensor for the detection of SARS-CoV-2 in clinical and environmental matrices. The sensor developed is composed of a screen-printed electrode (SPE) array which was constructed using conductive carbon ink printed on polyethylene terephthalate (PET) substrate made from disposable soft drink bottles. The recognition site (Spike S1 Antibody (anti-SP Ab)) was covalently immobilized on the working electrode surface, which was effectively modified with carbon black (CB) and gold nanoparticles (AuNPs). The immunosensing material was subjected to a multi-technique characterization analysis using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) with elemental analysis via energy dispersive spectroscopy (EDS). The electrochemical characterization of the electrode surface and analytical measurements were performed using cyclic voltammetry (CV) and square-wave voltammetry (SWV). The immunosensor was easily applied for the conduct of rapid diagnoses or accurate quantitative environmental analyses by setting the incubation period to 10 min or 120 min. Under optimized conditions, the biosensor presented limits of detection (LODs) of 101 fg mL-1 and 46.2 fg mL-1 for 10 min and 120 min incubation periods, respectively; in addition, the sensor was successfully applied for SARS-CoV-2 detection and quantification in clinical and environmental samples. Considering the costs of all the raw materials required for manufacturing 200 units of the AuNP-CB/PET-SPE immunosensor, the production cost per unit is 0.29 USD.

A portable, low-cost and high-throughput electrochemical impedance spectroscopy device for point-of-care biomarker detection

This paper presents a portable, fast and accurate electrochemical impedance spectroscopy (EIS) device with 8-well interdigitated electrode chips for biomarker detection. The design adopts low crest factor multisine signal synthesis at low frequencies (<1 kHz) and single-tone signals at high frequencies (>1 kHz), which significantly increases measurement speed without sacrificing accuracy. In addition, the low excitation amplitude of 10 mV preserves impedance linearity and protects the biosamples. The system achieved an average magnitude accuracy error of 0.30% in the frequency range of interest and it requires only 0.46 s to scan 28 frequency points from 10 Hz to 1 MHz. Experiments were conducted to test the capability to detect antibodies against SARS-CoV-2. Gold nanoparticles bound with protein G (GNP-G) were employed as the conjugated secondary antibody probe to detect anti-SARS-CoV-2 IgG in serum. A highly statistical significance (p = 7×10−6) could be found in the impedance data at 10 kHz. The impedance magnitude alteration caused by the GNP-G of the positive and negative groups were 27.2%±13.6% and 4.1%±1.7%, respectively. The results imply that the proposed system enables rapid COVID-19 antibody biomarker detection. Moreover, the EIS system and GNPs have the potential to be modified to detect other biomarkers. © 2022 The Author(s)

Nanotechnology for ultrafast nucleic acid amplification

Nucleic acid detection has been one of the most valued tools in point-of-care diagnostics from life science, agriculture, food safety and environmental surveillance, because of its high sensitivity, great specificity and simple operation. Since polymerase chain reactions (PCR) were discovered, more and more researchers attach importance to exploring ultrafast nucleic acid amplification methods for further expediting the process of detection and curbing infectious diseases' high spread rate, especially after the coronavirus disease 2019 (COVID-19) worldwide pandemic event. Nowadays, nanotechnology as one of the most cut-ting-edge technologies has aroused growing attention. In this review, we describe new advances in na-notechnology research for ultrafast nucleic acid amplification. We have introduced commonly used nanotechnologies, namely nanofluidics, nanoporous materials, nanoparticles and so on. Recent advances in these nanotechnologies for ultrafast sample pretreatments, accelerated enzymatic amplification and rapid heating/cooling processes was summarized. Finally, challenges and perspectives for the future applications of ultrafast nucleic acid amplification are presented.(c) 2022 Elsevier Ltd. All rights reserved.

Nanomaterials and Biosensing Technology for the SARS-CoV-2 Detection

The outbreak of corona virus disease 2019 (COVID-19) has aroused great attention around the world. SARS-CoV-2 possesses characteristics of faster transmission, immune escape, and occult transmission by many mutation, which caused still grim situation of prevention and control. Early detection and isolation of patients are still the most effective measures at present. So, there is an urgent need for new rapid and highly sensitive testing tools to quickly identify infected patients as soon as possible. This review briefly introduces general characteristics of SARS-CoV-2, and provides recentl overview and analysis based on different detection methods for nucleic acids, antibodies, antigens as detection target. Novel nano-biosensors for SARS-CoV-2 detection are analyzed based on optics, electricity, magnetism, and visualization. In view of the advantages of nanotechnology in improving detection sensitivity, specificity and accuracy, the research progress of new nano-biosensors is introduced in detail, including SERS-based biosensors, electrochemical biosensors, magnetic nano-biosensors and colorimetric biosensors. Functions and challenges of nano-materials in construction of new nano-biosensors are discussed, which provides ideas for the development of various coronavirus biosensing technologies for nanomaterial researchers.

Recent Advances in Colorimetric Sensors Based on Gold Nanoparticles for Pathogen Detection.

Infectious pathogens cause severe threats to public health due to their frightening infectivity and lethal capacity. Rapid and accurate detection of pathogens is of great significance for preventing their infection. Gold nanoparticles have drawn considerable attention in colorimetric biosensing during the past decades due to their unique physicochemical properties. Colorimetric diagnosis platforms based on functionalized AuNPs are emerging as a promising pathogen-analysis technique with the merits of high sensitivity, low-cost, and easy operation. This review summarizes the recent development in this field. We first introduce the significance of detecting pathogens and the characteristics of gold nanoparticles. Four types of colorimetric strategies, including the application of indirect target-mediated aggregation, chromogenic substrate-mediated catalytic activity, point-of-care testing (POCT) devices, and machine learning-assisted colorimetric sensor arrays, are systematically introduced. In particular, three biomolecule-functionalized AuNP-based colorimetric sensors are described in detail. Finally, we conclude by presenting our subjective views on the present challenges and some appropriate suggestions for future research directions of colorimetric sensors.

Clinical translation of gold nanoparticles.

Gold nanoparticles display unique physicochemical features, which can be useful for therapeutic purposes. After two decades of preclinical progress, gold nanoconstructs are slowly but steadily transitioning into clinical trials. Although initially thought to be "magic golden bullets" that could be used to treat a wide range of diseases, current consensus has moved toward a more realistic approach, where gold nanoformulations are being investigated to treat specific disorders. These therapeutic applications are dictated by the pharmacokinetics and biodistribution profiles of gold nanoparticles. Here, we analyze the current clinical landscape of therapeutic gold nanoconstructs, discuss the shared characteristics that allowed for their transition from bench to bedside, and examine existing hurdles that need to be overcome before they can be approved for clinical use.

Visual detection of SARS-CoV-2 with a CRISPR/Cas12b-based platform

The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic, highlighting the unprecedented demand for rapid and portable diagnostic methods. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) proteins-based platforms have been used for the detection of pathogens. However, in further applications and research, due to multiple steps needed, many methods showed an increased risk of cross-reactivity. The thermostable Cas12b enables the combination of isothermal amplification and CRISPR-mediated detection, which could decrease the risk of cross-contamination. In this study, we developed a portable and specific diagnostic method that combined the gold nanoparticle (AuNP) with thermal stable CRISPR/Cas12b-enhanced reverse transcription loop-mediated isothermal amplification (RT-LAMP), which is called SCAN, to distinguish the N gene of SARS-CoV-2 from flu gene. We validated our method using RNA from cells transfected by plasmids. We could easily distinguish the positive results by the naked eye based on the strong molar absorption coefficient of AuNP. Moreover, SCAN has the potential for high-throughput tests owing to its convenient operation. In sum, SCAN has broken the site and equipment restrictions of traditional detection methods and could be applied outside of hospitals and clinical laboratories, greatly expanding the test of COVID-19. [Display omitted] • The CRISPR/Cas12 b was employed to realize one-tube detection. • The SCAN assay is isothermal that requires minimal equipment. • The SCAN assay has a high-throughput potential for large-scale population screening. [ FROM AUTHOR]

Detection of COVID-19 DNA using Förster Resonance Energy Transfer between upconversion and gold nanoparticles

FRET is ascribed to the spectral overlapping of upconversion luminescence and the absorption of AuNPs. This experiment enables early-stage coronavirus detection. The results show a sensitivity of 100 fM for the detection of COVID-19 DNA. © 2022 The Author(s)

Gold-binding peptide as a selective layer for electrochemical detection of SARS-CoV-2 antibodies.

Electrochemical immunosensors are excellent alternatives to prepare portable platforms used for rapid and inexpensive diagnostic of infectious diseases such as the recently emerged COVID-19. Incorporating synthetic peptides as selective recognition layers combined with nanomaterials such as gold nanoparticles (AuNPs) can significantly enhance the analytical performance of immunosensors. In the present study, an electrochemical immunosensor based on solid-binding peptide was built and evaluated towards SARS-CoV-2 Anti-S antibodies detection. The peptide used as recognition site has two important portions: one based on the viral receptor binding domain (RBD), capable of recognizing antibodies of the spike protein (Anti-S), and another suitable for interacting with gold nanoparticles. Gold-binding peptide (Pept/AuNP) dispersion was used directly to modify a screen-printed carbon electrode (SPE). The voltammetric behavior of the [Fe(CN)6]3-/4- probe after every construction and detection step was recorded using cyclic voltammetry by assessing the stability of the Pept/AuNP as a recognition layer onto the electrode surface. Differential pulse voltammetry was used as a detection technique, and a linear working range from 75 ng mL-1 to 15 µg mL-1 was established, with 1.059 µA dec-1 of sensitivity and R2 = 0.984. The response selectivity against SARS-CoV-2 Anti-S antibodies was investigated in presence of concomitant species. The immunosensor was used to detect SARS-CoV-2 Anti-spike protein (Anti-S) antibodies in human serum samples, successfully differentiating between negative and positive responses of samples at a 95% confidence level. Therefore, the gold-binding peptide is a promising tool to be applied as a selective layer for antibody detection.

Engineering gold nanoparticles for molecular diagnostics and biosensing.

Advances in nanotechnology and medical science have spurred the development of engineered nanomaterials and nanoparticles with particular focus on their applications in biomedicine. In particular, gold nanoparticles (AuNPs) have been the focus of great interest, due to their exquisite intrinsic properties, such as ease of synthesis and surface functionalization, tunable size and shape, lack of acute toxicity and favorable optical, electronic, and physicochemical features, which possess great value for application in biodetection and diagnostics purposes, including molecular sensing, photoimaging, and application under the form of portable and simple biosensors (e.g., lateral flow immunoassays that have been extensively exploited during the current COVID-19 pandemic). We shall discuss the main properties of AuNPs, their synthesis and conjugation to biorecognition moieties, and the current trends in sensing and detection in biomedicine and diagnostics. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > In Vitro Nanoparticle-Based Sensing Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Awareness On Role of Kabasura Kudineer on Immunity Among Adult Population

Introduction: Kabasura kudineer is a concoction prepared as a siddha product which is effective against respiratory infection (1). It is made with the use of 15 herbs which includes ginger, clove, Piper Longum, Dusparsha, Akarakarabha, Kokilaksha, haritaki, Malabar nut, ajwain, Kusta, guduchi, Kalamegha,Raja pata, musta and Bharani (2). Each and every ingredient has its own importance like ginger promotes digestion and helps in treatment of respiratory ailments (3), Pippalli can treat indigestion, asthma and cough, clove helps to kill bacteria and promote liver health etc. Thus the aim of the study is to analyze the knowledge and awareness on the role of Kabasura kudineer on immunity among the adult population. Materials and methods: Self-administered structured questionnaires were designed based on the knowledge and awareness of the role of Kabasura kudineer on immunity among adults. The questionnaire was distributed through online google forms link, the study population included 100 dental students in Chennai.The data was collected and statistically analysed in SPSS of version 26.0.The study was approved by the Institutional Review Board. Results: Majority of 19 year old (52%) individuals had responded whereas 35% of 17 year old respondents among them nearly 97% were females and 88% were aware of kabasura kudineer. It was appreciable that 83% of respondents were aware that kabasura kudineer was a siddha formulation and only 50% were aware it was administered as concoction among whom 78% of individuals knew that it is a perfect remedy for respiratory ailments. Majority (52%) respondents were aware about the herbal ingredients used. Conclusion: Thus majority of adults were not aware about the properties of Kabasura kudineer. More awareness programmes have to be done to make Kabasura kudineer a prophylactic agent world wide.

A microchamber-free and enzyme-free digital assay based on ultrabright fluorescent microspheres

Digital analysis is an effective single-molecule detection method and has attracted extensive attention in the field of bioassays. However, most digital assays require microchambers for signal compartmentalization. Herein, we developed a microchamber-free and enzyme-free digital assay by labeling paramagnetic beads directly with ultrabright fluorescent microspheres. In this assay, a DNA sandwich analysis was firstly performed on the bead to label a fluorescent microsphere. Then, the beads were loaded on the glass slide to form a monolayer film for signal readout. The whole analysis process does not require the participation of enzymes and the preparation of microchambers, which greatly simplifies the experimental steps and saves the costs. Furthermore, by introducing non-enzymatic hybridization chain reaction (HCR) and biotinylated DNA-conjugated gold nanoparticles (Au NPs-Bio), the capture efficiency and analytical sensitivity were improved. As a proof of concept, single-stranded DNA (ssDNA) of SARS-CoV-2 fragment was chosen as a model, and a detection limit of 1.5 fM was achieved. Spiked and recovery experiments on human serum and saliva samples validated the good performance of the proposed digital assay in real biological samples. The proposed assay provides a facile way of signal generation and readout for digital analysis. © 2023 Elsevier B.V.

Detection of COVID-19 DNA using Förster Resonance Energy Transfer between upconversion and gold nanoparticles

FRET is ascribed to the spectral overlapping of upconversion luminescence and the absorption of AuNPs. This experiment enables early-stage coronavirus detection. The results show a sensitivity of 100 fM for the detection of COVID-19 DNA. © 2022 The Author(s)