A needle-like Cu2CdSnS4 alloy nanostructure-based integrated electrochemical biosensor for detecting the DNA of Dengue serotype 2

Rapid and label-free A2 peptide epitope decorated CoFe2O4-C60 nanocomposite-based electrochemical immunosensor for detecting Visceral Leishmaniasis

Diagnosis of Visceral Leishmaniasis is challenging due to the shared clinical features with malaria, typhoid, and tuberculosis. A CoFe2O4-C60 nanocomposite-based immunosensor decorated with a sensitive A2 peptide antigen was fabricated to detect anti-A2 antibodies for application in visceral leishmaniasis diagnosis. The flame-synthesised nanocomposite was characterised using Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. N terminated specific A2 peptide epitope antigen (NH2-QSVGPLSVGP-OH) was synthesised and characterised by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectroscopy (LC-MS). Using EDC/NHS, A2 peptide antigen (Apg) was immobilised on the CoFe2O4-C60-modified electrode. The performance of the immunosensor, Apg-CoFe2O4-C60NP/GCE, was evaluated by testing its ability to detect varying concentrations of anti-A2 antibody solution in PBS and spiked serum with 1 mM [Fe(CN)6]3-/4- in 0.01 M PBS (pH 7.4) as supporting electrolyte. using differential pulse voltammetry. The immunosensor showed excellent reproducibility and a linear range of 10-10-10-1 µg/mL, with an experimental detection limit of 30.34 fg/mL. These results suggest that the fabricated sensor has great potential as a tool for diagnosing visceral leishmaniasis.

Innovations in dengue virus detection: An overview of conventional and electrochemical biosensor approaches

Globally, people are in great threat due to the highly spreading of viral infectious diseases. Every year like 100-300 million cases of infections are found, and among them, above 80% are not recognized and irrelevant. Dengue virus (DENV) is an arbovirus infection that currently infects people most frequently. DENV encompasses four viral serotypes, and they each express comparable sign. From a mild febrile sickness to a potentially fatal dengue hemorrhagic fever, dengue can induce a variety of symptoms. Presently, the globe is being challenged by the untimely identification of dengue infection. Therefore, this review summarizes advances in the detection of dengue from conventional methods (nucleic acid-based, polymerase chain reaction-based, and serological approaches) to novel biosensors. This work illustrates an extensive study of the current designs and fabrication approaches involved in the formation of electrochemical biosensors for untimely identifications of dengue. Additionally, in electrochemical sensing of DENV, we skimmed through significances of biorecognition molecules like lectins, nucleic acid, and antibodies. The introduction of emerging techniques such as the CRISPR/Cas' system and their integration with biosensing platforms has also been summarized. Furthermore, the review revealed the importance of electrochemical approach compared with traditional diagnostic methods.

Recent Advances in the Role of Different Nanoparticles in the Various Biosensors for the Detection of the Chikungunya Virus

Humans contract the Chikungunya virus (CHIKV), an alphavirus transmitted by mosquitoes that induces acute and chronic musculoskeletal discomfort and fever. Millions of cases of the disease have been attributed to CHIKV in the Indian Ocean region since 2004, and the virus has since spread to Europe, the Middle East, and the Pacific. The exponential proliferation of CHIKV in recent times underscores the critical nature of implementing preventative measures and exploring potential control strategies. The principal laboratory test employed to diagnose infection in serum samples collected over six days after the onset of symptoms is the detection of CHIKV or viral RNA. Although two commercially available real-time reverse transcription-polymerase chain reaction products exist, data on their validity are limited. A diagnostic instrument that is rapid, sensitive, specific, and cost-effective is, therefore an absolute necessity, particularly in developing nations. Biosensors have demonstrated considerable potential in the realm of pathogen detection. The rapid and sensitive detection of viruses has been facilitated by the development of numerous types of biosensors, including affinity-based nano-biosensors, graphene affinity-based biosensors, optical nano-biosensors, surface Plasmon Resonance-based optical nano-biosensors, and electrochemical nano-biosensors. Furthermore, the utilization of nanomaterials for signal extension, including but not limited to gold and silver nanoparticles, quantum dots, and iron oxide NPs, has enhanced the precision and sensitivity of biosensors. The developed innovative diagnostic method is time-efficient, precise, and economical; it can be implemented as a point-of-care device. The technique may be implemented in diagnostic laboratories and hospitals to identify patients infected with CHIKV. Throughout this article, we have examined a multitude of CHIKV nano-biosensors and their respective properties. Following a discussion of representative nanotechnologies for biosensors, numerous NPs-assisted CHIKV nano-biosensors are summarized in this article. As a result, we anticipate that this review will furnish a significant foundation for advancing innovative CHIKV nano-biosensors.

A comprehensive review of dengue with a focus on emerging solutions for precision and timely detection

Dengue is a global health problem, caused by the dengue virus (DENV), which belongs to the Flaviviridae family of viruses. The transmission of DENV occurs through vectors, Ae. aegypti and Ae. Albopictus mosquitoes, to the human host, classifying it as a vector-borne disease. The disease incidence is increasing at an alarming rate and needs to be tackled to reduce the morbidity and mortality caused by the disease. Environmental and clinical surveillance, detection of the virus, and diagnostics are critical tools to address this issue. In this comprehensive review, we explore various diagnostic techniques and the associated challenges within the context of dengue. While we briefly touch upon dengue's epidemiology, serotypes, and pathogenesis, our primary emphasis remains on diagnostics. We delve into the intricacies of these diagnostic methods, considering both the challenges they entail and the potential they hold in terms of accuracy and accessibility. It's important to note that the review does not extensively cover clinical aspects or regional variations of the disease.

Label-free genosensing of dengue serotypes with an electrodeposited reduced graphene oxide-tris(bipyridine)ruthenium(II)

Constructing a label-free electrochemical transducer platform without compromising inherent biocompatibility against specific bioreceptor remains challenging, particularly probing nucleic acid hybridization at electrode interface without external redox-mediator. Here, we show that electrochemically reduced graphene oxide-tris(bipyridine)ruthenium(II) (ErGO-TBR) nanosheets electrodeposited on carbon screen printed electrode can quantify hybridization of clinically important target sequences specific to serotypes of dengue virus (DENV) non-structural 1 (NS1) protein. Different variables including deposition potential, time, and electrolytic composition were optimized for fabrication of label-free transducer platform. Structural and electrochemical properties of ErGO-TBR/SPE were comprehensively elucidated using microscopic and spectroscopic techniques. Electrochemical quartz crystal microbalance (EQCM) analysis reveals the growth of electrodeposited redox-active species on the electrode interface. Surface functional group investigations suggested that TBR deposited on the basal and edges of ErGO substrate via electrostatic and π-π interactions. Functionalization of bio-affinity layer (B) on ErGO-TBR/SPE enables better loading of probe DNA (PDNA) toward specific detection of DENV target DNA (TDNA) with an ultralow detection limit promising for clinical diagnosis. Scalable chronoamperometry-based redox-active surface growth, customizable bioactivation strategy and external mediator-less probing of nucleic acid hybridization make the present system suitable for other translational application in healthcare diagnosis.

Spinal cord injury immunosensor: Sensitive detection of S100β on interdigitated electrode sensor

A spinal cord injury is damage to the nerves and cells that receive and provide a signal from the brain to the rest of the body. Spinal injury causes changes in movement, sensation, and strength, affect the body functions near the injury site, and may lead to paralysis. S100β was found as a suitable biomarker for identifying spinal cord injury and its causing problem. Herein, S100β immunoassay was developed on interdigitated electrode sensor to diagnose spinal cord injury. For effective anti-S100β antibody immobilization, the antibody was premixed with 3-Aminopropyl)triethoxsilane and then attached to the hydroxylated interdigitated electrode surface. This method of antibody immobilization enhanced the antibody attachment two-times than the method without premix. Antibody-attached surfaces increased current responses as S100 concentrations increased, and the limit of detection was seen to be 1 pg/mL on the linearity until 3000 pg/mL at an R2 value of 0.9907 [y = 7x - 6.4667]. Further, biofouling experiments with glial fibrillary acidic protein and γ-aminobutyric acid failed to enhance the current response, indicating the specific detection of S100β. This immunoassay identifies S100β at its lower level and helps to diagnose spinal cord injury and its related problem.

Impact of nanotechnology on conventional and artificial intelligence-based biosensing strategies for the detection of viruses

Recent years have witnessed the emergence of several viruses and other pathogens. Some of these infectious diseases have spread globally, resulting in pandemics. Although biosensors of various types have been utilized for virus detection, their limited sensitivity remains an issue. Therefore, the development of better diagnostic tools that facilitate the more efficient detection of viruses and other pathogens has become important. Nanotechnology has been recognized as a powerful tool for the detection of viruses, and it is expected to change the landscape of virus detection and analysis. Recently, nanomaterials have gained enormous attention for their value in improving biosensor performance owing to their high surface-to-volume ratio and quantum size effects. This article reviews the impact of nanotechnology on the design, development, and performance of sensors for the detection of viruses. Special attention has been paid to nanoscale materials, various types of nanobiosensors, the internet of medical things, and artificial intelligence-based viral diagnostic techniques.

Quantitative detection of dengue serotypes using a smartphone-connected handheld lab-on-chip platform

Dengue is one of the most prevalent infectious diseases in the world. Rapid, accurate and scalable diagnostics are key to patient management and epidemiological surveillance of the dengue virus (DENV), however current technologies do not match required clinical sensitivity and specificity or rely on large laboratory equipment. In this work, we report the translation of our smartphone-connected handheld Lab-on-Chip (LoC) platform for the quantitative detection of two dengue serotypes. At its core, the approach relies on the combination of Complementary Metal-Oxide-Semiconductor (CMOS) microchip technology to integrate an array of 78 × 56 potentiometric sensors, and a label-free reverse-transcriptase loop mediated isothermal amplification (RT-LAMP) assay. The platform communicates to a smartphone app which synchronises results in real time with a secure cloud server hosted by Amazon Web Services (AWS) for epidemiological surveillance. The assay on our LoC platform (RT-eLAMP) was shown to match performance on a gold-standard fluorescence-based real-time instrument (RT-qLAMP) with synthetic DENV-1 and DENV-2 RNA and extracted RNA from 9 DENV-2 clinical isolates, achieving quantitative detection in under 15 min. To validate the portability of the platform and the geo-tagging capabilities, we led our study in the laboratories at Imperial College London, UK, and Kaohsiung Medical Hospital, Taiwan. This approach carries high potential for application in low resource settings at the point of care (PoC).

Detection Efficiency of Ag Nanoparticle Labels for a Heart Failure Marker Using Linear and Square-Wave Anodic Stripping Voltammetry

In this article, we compare linear sweep anodic stripping voltammetry (LASV) and square-wave anodic stripping voltammetry (SWASV) for detection of a nano metalloimmunoassay. Two separate immunoassays were examined: a model assay, based on interactions between antibodies, and a sandwich assay for the heart failure marker NT-proBNP. In both cases, one antibody is linked to a magnetic microbead, and one is linked to a spherical Ag nanoparticle label. Electrochemical detection is carried out on a paper device. The three analytical figures of merit studied were the precision of the measurements, the calibration sensitivity, and the limit of detection (LOD). For the NT-proBNP assay, the results show that after optimization of the pulse amplitude and frequency of the potential input for SWASV, the detection efficiency is substantially higher compared to LASV. Specifically, the calibration sensitivity increased by up to ~40 fold, the average coefficient of variation decreased by ~40%, and the (LOD) decreased to 300.0 pM. Finally, for a model immunoassay, a ~10-fold decrease in the LOD was observed for SWASV compared to LASV.

A sensitive electrochemical method for rapid detection of dengue virus by CRISPR/Cas13a-assisted catalytic hairpin assembly

Dengue fever caused by Dengue virus (DENV) infection has been widely popular, especially in tropical and subtropical areas. Rapid and sensitive diagnosis is the first priority for treatment of DENV infection. This work designed a signal amplification strategy for sensitive electrochemical detection of DENV by using a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas13a system for catalytic hairpin assembly on electrode surface. The presence of target RNA could activate the cleavage activity of the CRISPR/Cas13a system to release the blocker silenced swing arms, which then hybridized with hairpin 1 (H1) immobilized on electrode surface to expose the pre-locked toehold domain of H1 for the hybridization of ferrocene-labeled hairpin 2 (H2-Fc). Eventually, a large number of H2-Fc were captured to the electrode to produce amperometric signal for achieving signal amplification. This method showed a linear detection range from 5 fM to 50 nM with a detection limit of 0.78 fM. The proposed assay was successfully used to detect DENV type 1 in total RNA sample extracted, indicating great potential for application in early clinical diagnostic.

Nanowire-based sensor electronics for chemical and biological applications

Detection and recognition of chemical and biological species via sensor electronics are important not only for various sensing applications but also for fundamental scientific understanding. In the past two decades, sensor devices using one-dimensional (1D) nanowires have emerged as promising and powerful platforms for electrical detection of chemical species and biologically relevant molecules due to their superior sensing performance, long-term stability, and ultra-low power consumption. This paper presents a comprehensive overview of the recent progress and achievements in 1D nanowire synthesis, working principles of nanowire-based sensors, and the applications of nanowire-based sensor electronics in chemical and biological analytes detection and recognition. In addition, some critical issues that hinder the practical applications of 1D nanowire-based sensor electronics, including device reproducibility and selectivity, stability, and power consumption, will be highlighted. Finally, challenges, perspectives, and opportunities for developing advanced and innovative nanowire-based sensor electronics in chemical and biological applications are featured.

Electrochemical biosensors for neglected tropical diseases: A review

A group of infectious and parasitic diseases with prevalence in tropical and subtropical regions of the planet, especially in places with difficult access, internal conflicts, poverty, and low visibility from the government and health agencies are classified as neglected tropical diseases. While some well-intentioned isolated groups are making the difference on a global scale, the number of new cases and deaths is still alarming. The development and employment of low-cost, miniaturized, and easy-to-use devices as biosensors could be the key to fast diagnosis in such areas leading to a better treatment to further eradication of such diseases. Therefore, this review contains useful information regarding the development of such devices in the past ten years (2010-2020). Guided by the updated list from the World Health Organization, the work evaluated the new trends in the biosensor field applied to the early detection of neglected tropical diseases, the efficiencies of the devices compared to the traditional techniques, and the applicability on-site for local distribution. So, we focus on Malaria, Chagas, Leishmaniasis, Dengue, Zika, Chikungunya, Schistosomiasis, Leprosy, Human African trypanosomiasis (sleeping sickness), Lymphatic filariasis, and Rabies. Few papers were found concerning such diseases and there is no available commercial device in the market. The works contain information regarding the development of point-of-care devices, but there are only at proof of concepts stage so far. Details of electrode modification and construction of electrochemical biosensors were summarized in Tables. The demand for the eradication of neglected tropical diseases is increasing. The use of biosensors is pivotal for the cause, but appliable devices are scarce. The information present in this review can be useful for further development of biosensors in the hope of helping the world combat these deadly diseases.

Microfluidic-based virus detection methods for respiratory diseases

With the recent SARS-CoV-2 outbreak, the importance of rapid and direct detection of respiratory disease viruses has been well recognized. The detection of these viruses with novel technologies is vital in timely prevention and treatment strategies for epidemics and pandemics. Respiratory viruses can be detected from saliva, swab samples, nasal fluid, and blood, and collected samples can be analyzed by various techniques. Conventional methods for virus detection are based on techniques relying on cell culture, antigen-antibody interactions, and nucleic acids. However, these methods require trained personnel as well as expensive equipment. Microfluidic technologies, on the other hand, are one of the most accurate and specific methods to directly detect respiratory tract viruses. During viral infections, the production of detectable amounts of relevant antibodies takes a few days to weeks, hampering the aim of prevention. Alternatively, nucleic acid-based methods can directly detect the virus-specific RNA or DNA region, even before the immune response. There are numerous methods to detect respiratory viruses, but direct detection techniques have higher specificity and sensitivity than other techniques. This review aims to summarize the methods and technologies developed for microfluidic-based direct detection of viruses that cause respiratory infection using different detection techniques. Microfluidics enables the use of minimal sample volumes and thereby leading to a time, cost, and labor effective operation. Microfluidic-based detection technologies provide affordable, portable, rapid, and sensitive analysis of intact virus or virus genetic material, which is very important in pandemic and epidemic events to control outbreaks with an effective diagnosis.

Ultrasensitive detection of pathogenic viruses with electrochemical biosensor: State of the art

Last few decades, viruses are a real menace to human safety. Therefore, the rapid identification of viruses should be one of the best ways to prevent an outbreak and important implications for medical healthcare. The recent outbreak of coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered coronavirus which belongs to the single-stranded, positive-strand RNA viruses. The pandemic dimension spread of COVID-19 poses a severe threat to the health and lives of seven billion people worldwide. There is a growing urgency worldwide to establish a point-of-care device for the rapid detection of COVID-19 to prevent subsequent secondary spread. Therefore, the need for sensitive, selective, and rapid diagnostic devices plays a vital role in selecting appropriate treatments and to prevent the epidemics. During the last decade, electrochemical biosensors have emerged as reliable analytical devices and represent a new promising tool for the detection of different pathogenic viruses. This review summarizes the state of the art of different virus detection with currently available electrochemical detection methods. Moreover, this review discusses different fabrication techniques, detection principles, and applications of various virus biosensors. Future research also looks at the use of electrochemical biosensors regarding a potential detection kit for the rapid identification of the COVID-19.

Recent advances and challenges in electrochemical biosensors for emerging and re-emerging infectious diseases

The rise of emerging infectious diseases (EIDs) as well as the increase in spread of existing infections is threatening global economies and human lives, with several countries still fighting repeated onslaught of a few of these epidemics. The catastrophic impact a pandemic has on humans and economy should serve as a reminder to be better prepared to the advent of known and unknown pathogens in the future. The goal of having a set of initiatives and procedures to tackle them is the need of the hour.

Rapid detection and point-of-care (POC) analysis of pathogens causing these diseases is not only a problem entailing the scientific community but also raises challenges in tailoring appropriate treatment strategies to the healthcare sector. Among the various methods used to detect pathogens, Electrochemical Biosensor Technology is at the forefront in the development of POC devices. Electrochemical Biosensors stand in good stead due to their rapid response, high sensitivity and selectivity and ease of miniaturization to name a few advantages.

This review explores the innovations in electrochemical biosensing based on the various electroanalytical techniques including voltammetry, impedance, amperometry and potentiometry and discusses their potential in diagnosis of emerging and re-emerging infectious diseases (Re-EIDs), which are potential pandemic threats.

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This review offers a detailed description of the latest developments in electrochemical biosensors for emerging and re-emerging infectious diseases.

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Advantages and limitations of various types of electrochemical biosensor techniques are demonstrated.

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Discusses the latest electrochemical biosensors for COVID-19.

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Challenges and future prospects of electrochemical biosensors have been discussed in this review.

New equiatomic quaternary Heusler compounds without transition metals KCaBX (X = S and Se): Robust half-metallicity and optical properties

It is known that high spin-polarization and magnetism can be found even in materials with neither transition metals nor rare earths. In this paper, we report results of the structural design, electronic structure, magnetic and optical properties of new equiatomic quaternary Heusler (EQH) KCaBX (X = S and Se) compounds. Electron exchangecorrelation interactions are described by the Wu-Cohen (WC) functional and Tran-Blaha modified Becke-Johnson exchange (mBJ) potential. Ferromagnetic ordering is stable for the cubic structure of space group F43 m in which the K, Ca, B and X atoms are located at 4c, 4d, 4a and 4b Wyckoff positions, respectively. Quaternaries at hand exhibit a perfect spin-polarization around the Fermi level, which is a result of the half-metallicity with metallic spin-up channel and semiconductor spin-dn channel. The ferromagnetic half-metallic and spin-flip band gaps are 2.648(2.470) and 0.673(0.526), respectively, for KCaBS(KCaBSe). Both studied compounds have a total magnetic moment of 2.000 μ_B. Additionally, the strain effect on the electronic and magnetic properties is also examined. Finally, the optical properties of the KCaBX alloys are investigated for energies up to 25 eV. Optical spectra show the metallic behavior at extremely low energies and semiconductor nature at higher energies. Interestingly, KCaBS and KCaBSe exhibit prospective absorption properties with a quite large absorption coefficient in the ultraviolet regime.

Rapid and specific DNA detection by magnetic field-enhanced agglutination assay

The detection of DNA molecules by agglutination assays has suffered from a lack of specificity. The specificity can be improved by introducing a hybridization step with a specific probe. We developed a setting that captured biotinylated DNA targets between magnetic nanoparticles (MNPs) grafted with tetrathiolated probes and anti-biotin antibodies. The agglutination assay was enhanced using a series of magnetization cycles. This setting allowed to successfully detect a synthetic single stranded DNA with a sensitivity as low as 9 pM. We next adapted this setting to the detection of PCR products. We first developed an asymmetric pan-flavivirus amplification. Then, we demonstrated its ability to detect dengue virus with a limit of detection of 100 TCID₅₀/mL. This magnetic field-enhanced agglutination assay is an endpoint readout, which benefits from the advantages of using nanoparticles that result in particular from a very reduced duration of the test; in our case it lasts less than 5 min. This approach provides a solution to develop new generation platforms for molecular diagnostics.

A Label-Free Impedimetric Genosensor for the Nucleic Acid Amplification-Free Detection of Extracted RNA of Dengue Virus

Developing rapid and sensitive diagnostic methods for dengue virus (DENV) infection is of prime priority because DENV infection is the most prevalent mosquito-borne viral disease. This work proposes an electrochemical impedance spectroscopy (EIS)-based genosensor for the label-free and nucleic acid amplification-free detection of extracted DENV RNA intended for a sensitive diagnosis of DENV infection. A concentration ratio of 0.04 mM 6-mercaptohexanoic acid (MHA) to 1 mM 6-mercapto-1-hexanol (MCH) was selected to modify thin-film gold electrodes as a link to control the coverage of self-designed probe DNA (pDNA) at a density of 4.5 ± 0.4 × 10¹¹ pDNA/cm². The pDNA/MHA/MCH-modified genosensors are proven to improve the hybridization efficiency of a synthetic 160-mer target DNA (160mtDNA) with a 140-mer electrode side overhang as compared to other MHA/MCH ratio-modified genosensors. The MHA(0.04 mM)/MCH(1 mM)-modified genosensors also present good hybridization efficiency with the extracted DENV serotype 1 (DENV1) RNA samples, having the same electrode side overhangs with the 160mtDNA, showing a low detection limit of 20 plaque forming units (PFU)/mL, a linear range of 10²–10⁵ PFU/mL and good selectivity for DENV1. The pDNA density-controlled method has great promise to construct sensitive genosensors based on the hybridization of extracted DENV nucleic acids.

Titanium dioxide-mediated resistive nanobiosensor for E. coli O157:H7

A titanium dioxide nanoparticle (TiO₂ NP)-mediated resistive biosensor is described for the determination of DNA fragments of Escherichia coli O157:H7 (E. coli O157:H7). The sol-gel method was used to synthesize the TiO₂ NP, and microlithography was applied to fabricate the interdigitated sensor electrodes. Conventional E. coli DNA detections are facing difficulties in long-preparation-and-detection-time (more than 3 days). Hence, electronic biosensor was introduced by measuring the current-voltage (I-V) DNA probe without amplification of DNA fragments. The detection scheme is based on the interaction between the electron flow on the sensor and the introduction of negative charges from DNA probe and target DNA. The biosensor has a sensitivity of 1.67 × 10¹³ Ω/M and a wide analytical range. The limit detection is down to 1 × 10^-11 M of DNA. The sensor possesses outstanding repeatability and reproducibility and is cabable to detect DNA within 15 min in a minute-volume sample (1 μL). Graphical abstract Fig. (a) Graphical illustration of electronic biosensor set up and (b) relationship between limit of detection (LOD) and the unaffected poultry samples on E. coli O157:H7.

The detection and identification of dengue virus serotypes with quantum dot and AuNP regulated localized surface plasmon resonance

The dengue hemorrhagic fever or dengue shock syndrome has become a severe human fatal disease caused by infection with one of the four closely related but serologically distinct dengue viruses (DENVs). All four dengue serotypes are currently co-circulating throughout the subtropics and tropics. Since the fatality rate increases severely when a secondary infection occurs by a virus serotype different from that of the initial infection, serotype identification is equally important as virus detection. In this study, the development and validation of a rapid and quantitative DENV serotype-specific (serotypes 1-4) biosensor are reported by optimizing the stable system between cadmium selenide tellurium sulphide fluorescent quantum dots (CdSeTeS QDs) and gold nanoparticles (AuNPs). Four different nanoprobes are designed using each primer-probe serotype-specific hairpin single-stranded DNA covalently bound at different positions to CdSeTeS QDs, which generates an altered fluorescence signal for each serotype of DENV. In fourplex reactions with free functionalized AuNPs and the four nanoprobes, the standard dilutions of the target virus DNA from 10^-15 to 10^-10 M were successfully detected. The limit of detection was found to be in the femtomolar range for all four serotypes, where the serotype detection ability was undoubtedly established. To confirm the applicability of this sensing performance in long chained complex RNAs, the sensor was also applied successfully to RNAs extracted from DENV culture fluids for serotype identification as well as quantification, which can lead to a potential diagnostic probe for point-of-care detection.

Probing the path for achieving a broad temperature plateau of the figure of merit in thermoelectric nanocomposite materials

The efficiency of a thermoelectric device depends directly on the average figure of merit (zT) of the material. A high average zT requires a broad temperature plateau with a high zT, but state-of-the-art thermoelectric materials display a peaked zT over a narrow temperature range due to a strong temperature dependence of transport properties. In this work, using Boltzmann transport theory, we systematically investigate the underlying physics and propose a strategy for attaining a broad temperature plateau of zT through proper engineering of the interfacial barrier height in PbTe nanocomposite material. The optimized barrier height (U _constantzT) not only enhances the zT but also maintains its high value over a wide temperature range [T_min :T_max ]. It has been found that for p = 2.8 × 10²⁰ cm^-3, the U _constantzT is 0.112 eV at which zT varies between 1.9-2.14 over a wide temperature range of 550-850 K, resulting in a high average zT of 2.02 in comparison to a bulk value of 1.22. Also, for p = 5 × 10¹⁹ cm^-3, U_constantzT is 0.102 eV at which zT varies between 1.046-1.435 for a temperature range of 300-600K, resulting in a high average zT of 1.27 over a bulk value of 0.844. The above results show that the range [T_min :T_max ] depends on carrier concentration which, in turn, determines the position of the Fermi level (E_f ) and Fermi window at T_min and T_max . To obtain a broad temperature plateau of zT, the findings show that at T_min, E_f should lie inside the band and zT should show strong variation with barrier height, whereas at T_max , E_f should lie in the band gap and zT should have little variation with barrier height. This trend allows us to choose U_constantzT which synergistically optimizes the transport properties at T_min with T_max to give a broad temperature plateau of zT. This work proposes a new advantage of interfacial scattering which enhances the average zT and also provides necessary guidelines to experimentalists for synthesizing a highly efficient thermoelectric device.

Electrochemical virus detections with nanobiosensors

Infectious diseases are caused from pathogens, which need a reliable and fast diagnosis. Today, expert personnel and centralized laboratories are needed to afford much time in diagnosing diseases caused from pathogens.

Recent progress in electrochemical studies shows that biosensors are very simple, accurate, precise, and cheap at virus detection, for which researchers find great interest in this field. The clinical levels of these pathogens can be easily analyzed with proposed biosensors. Their working principle is based on affinity between antibody and antigen in body fluids. The progress still continues on these biosensors for accurate, rapid, reliable sensors in future.

Electrochemical biosensing of mosquito-borne viral disease, dengue: A review

Dengue virus is a mosquito-borne, single positive-stranded RNA virus that spread human being through infected female Aedes mosquito bite and causes dengue fever. The demand for early detection of this virus has increased to control the widespread of infectious diseases and protect humankind from its harmful effects. Recently, biosensors are found to the potential tool to detect and quantify the virus with fast detection, relatively cost-effective, high sensitivity and selectivity than the conventional diagnostic methods such as immunological and molecular techniques. Mostly, the biosensors employ electrochemical detection technique with transducers, owing to its easy construction, low-cost, ease of use, and portability. Here, we review the current trends and advancement in the electrochemical diagnosis of dengue virus and discussed various types of electrochemical biosensing techniques such as; amperometric, potentiometric, impedometric, and voltammetric sensing. Apart from these, we discussed the role of biorecognition molecules such as nucleic acid, antibodies, and lectins in electrochemical sensing of dengue virus. In addition, the review highlighted the benefits of the electrochemical approach in comparison with traditional diagnostic methods. We expect that these dengue virus diagnostic techniques will continue to evolve and grow in future, with exciting new possibilities stemming from advancement in the rational design of electrochemical biosensors.

Dengue virus: a review on advances in detection and trends - from conventional methods to novel biosensors

Dengue virus is an important arbovirus infection which transmitted by the Aedes female mosquitoes. The attempt to control and early detection of this infection is a global public health issue at present. Because of the clinical importance of its detection, the main focus of this review is on all of the methods that can offer the new diagnosis strategies. The advantages and disadvantages of reported methods have been discussed comprehensively from different aspects like biomarkers type, sensitivity, accuracy, rate of detection, possibility of commercialization, availability, limit of detection, linear range, simplicity, mechanism of detection, and ability of usage for clinical applications. The optical, electrochemical, microfluidic, enzyme linked immunosorbent assay (ELISA), and smartphone-based biosensors are the main approaches which developed for detection of different biomarkers and serotypes of Dengue virus. Future efforts in miniaturization of these methods open the horizons for development of commercial biosensors for early-diagnosis of Dengue virus infection. Graphical abstract Transmission of Dengue virus by the biting of an Aedes aegypti mosquito, the symptoms of Dengue hemorrhagic fever and the structure of Dengue virus and application of biosensors for its detection.

Localized surface plasmon resonance (LSPR) biosensor based on thermally annealed silver nanostructures with on-chip blood-plasma separation for the detection of dengue non-structural protein NS1 antigen

Early diagnosis of dengue biomarkers by employing a technology that is less labor- and time-intensive and offers higher sensitivity and lower limits of detection would find great significance in the developing world. Here, we report the development of a biosensor that exploits the localized surface plasmon resonance (LSPR) effect of silver nanostructures, created via thermal annealing of thin metal film, to detect dengue NS1 antigen, which appears as early as the onset of infection. The biosensor integrates membrane-based blood-plasma separation to develop lab-on-chip device that facilitates rapid diagnosis (within 30 min) of dengue NS1 antigen from a small volume (10 µL) of whole blood. The refractive index (RI) sensitivity of the LSPR biosensor was verified by using aqueous glycerol (0-100 wt%) which showed that it is sufficiently sensitive to detect 10^-3 change in RI, which is comparable to that observed with protein-protein interaction. The RI sensitivity was utilized to demonstrate protein binding by using bovine serum albumin and detection of antibody-antigen immune reaction by binding human chorionic gonadotropin antigen to immunoglobulin antibody immobilized in our LSPR biosensor. Next, we demonstrated the detection of NS1 in plasma obtained via centrifugation and in plasma separated on-chip. From 10 µL of whole blood spiked with NS1 antigen, our biosensor reliably detects 0.06 µg/mL of NS1, which lies within the clinical limit observed during the first seven days of infection, with a sensitivity of 9 nm/(µg/mL). These results confirm that the proposed LSPR biosensor can potentially be used in point-of-care dengue diagnostics.

Diagnosing Perioperative Cardiovascular Risks in Noncardiac Surgery Patients

Every year, over 200 million adults are undergoing noncardiac surgery. These noncardiac surgery patients may face the risk of cardiac mortality and morbidity during the perioperative and recovery periods. Around ten million patients who underwent noncardiac surgery experience cardiac complications within the first 30 days of the postoperative period; the complications are myocardial infarction, cardiac death, and cardiac arrest. This cardiovascular risk is mostly faced by the patients having cerebrovascular or cardiac disease and the patients with the age greater than 50 years. Monitoring and treating cardiac diseases with a suitable biomarker during the perioperative period is necessary for the early recovery of noncardiac surgery patients. This review discussed the risk factors and the key guidelines to avoid the cardiovascular risks during the perioperative period of noncardiac surgery patients. In addition, the biomarkers and identification strategies for cardiac diseases are discussed.

Designing probe from E6 genome region of human Papillomavirus 16 for sensing applications

Human Papillomavirus (HPV) is a standout amongst the most commonly reported over 100 types, among them genotypes 16, 18, 31 and 45 are the high-risk HPV. Herein, we designed the oligonucleotide probe for the detection of predominant HPV type 16 for the sensing applications. Conserved amino acid sequences within E6 region of the open reading frame in the HPV genome was used as the basis to design oligonucleotide probe to detect cervical cancer. Analyses of E6 amino acid sequences from the high-risk HPVs were done to check the percentage of similarity and consensus regions that cause different cancers, including cervical cancer. Basic local alignment search tools (BLAST) have given extra statistical parameters, for example, desire values (E-values) and score bits. The probe, 'GGG GTC GGT GGA CCG GTC GAT GTA' was designed with 66.7% GC content. This oligonucleotide probe is designed with the length of 24 mer, GC percent is between 40 and 70, and the melting point (Tm) is above 50°C. The probe needed an acceptable length between 22 and 31 mer. The choice of region is identified here can be used as a probe, has implications for HPV detection techniques in biosensor especially for clinical determination of cervical cancer.