Electrochemical Biosensing Interface Based on Carbon Dots-Fe3O4 Nanomaterial for the Determination of Escherichia coli O157:H7

Carbon dots for pathogen detection and imaging: recent breakthroughs and future trends

As a class of carbon-based nanomaterials, carbon dots (CDs) have gained a lot of interest for a variety of applications. They offer distinctive optical, chemical, and structural characteristics along with favourable attributes such as low cost, availability of abundant functional groups, remarkable chemical inertness, high stability, exceptional biocompatibility, and ecofriendliness. This review discusses synthesis methods, structural characteristics, and surface modifications of CDs, specific for pathogen detection. Furthermore, it delves into the mechanisms that govern the interaction between pathogens and CDs. In addition, the study explores the use of CDs in a number of detection modalities, such as optical, electrochemical, and electrochemiluminescence, emphasising real-time pathogen monitoring. Moreover, both the challenges and opportunities related to the application of CDs-based detection and imaging methods are highlighted in field and clinical contexts.

Electrochemical and optical biosensors for the detection of E. Coli

E. coli is a common pathogenic microorganism responsible for numerous food and waterborne illnesses. Traditional detection methods often require long, multi-step processes and specialized equipment. Electrochemical and optical biosensors offer promising alternatives due to their high sensitivity, selectivity, and real-time monitoring capabilities. Recent advancements in sensor development focus on various techniques for detecting E. coli, including optical (fluorescence, colorimetric analysis, surface-enhanced Raman spectroscopy, surface plasmon resonance, localized surface plasmon resonance, chemiluminescence) and electrochemical (amperometric, voltammetry, impedance, potentiometric). Herein, the latest advancements in optical and electrochemical biosensors created for identifying E. coli with an emphasis on surface modifications employing nanomaterials and biomolecules are outlined in this review. Electrochemical biosensors exploit the unique electrochemical properties of E. coli or its specific biomolecules to generate a measurable signal. In contrast, optical biosensors rely on interactions between E. coli and optical elements to generate a detectable response. Moreover, optical detection has been exploited in portable devices such as smart phones and paper-based sensors. Different types of electrodes, nanoparticles, antibodies, aptamers, and fluorescence-based systems have been employed to enhance the sensitivity and specificity of these biosensors. Integrating nanotechnology and biorecognition (which bind to a specific region of the E. coli) elements has enabled the development of portable and miniaturized devices for on-site and point-of-care (POC) applications. These biosensors have demonstrated high sensitivity and offer low detection limits for E. coli detection. The convergence of electrochemical and optical technologies promises excellent opportunities to revolutionize E. coli detection, improving food safety and public health.

Carbon dots-based fluorescent probe for detection of foodborne pathogens and its potential with microfluidics

Concern about food safety triggers demand on rapid, accurate and on-site detection of foodborne pathogens. Among various fluorescent probes for detection, carbon dots (CDs) prepared by carbonization of carbon-rich raw materials show extraordinary performance for their excellent and tailorable photoluminescence property, as well as their facilely gained specificity by surface customization and modification. CDs-based fluorescent probes play a crucial role in many pathogenic bacteria sensing systems. In addition, microfluidic technology with characteristics of portability and functional integration is expected to combine with CDs-based fluorescent probes for point-of-care testing (POCT), which can further enhance the detection property of CDs-based fluorescent probes. Here, this paper reviews CDs-based bacterial detection methods and systems, including the structural modulation of fluorescent probes and pathogenic bacteria detection mechanisms, and describes the potential of combining CDs with microfluidic technology, providing reference for the development of novel rapid detection technology for pathogenic bacteria in food.

Nanomaterials revolutionize biosensing: 0D-3D designs for ultrasensitive detection of microorganisms and viruses

Various diseases caused by harmful microorganisms and viruses have caused serious harm and huge economic losses to society. Thus, rapid detection of harmful microorganisms and viruses is necessary for disease prevention and treatment. Nanomaterials have unique properties that other materials do not possess, such as a small size effect and quantum size effect. Introducing nanomaterials into biosensors improves the performance of biosensors for faster and more accurate detection of microorganisms and viruses. This review aims to introduce the different kinds of biosensors and the latest advances in the application of nanomaterials in biosensors. In particular, this review focuses on describing the physicochemical properties of zero-, one-, two-, and three-dimensional nanostructures as well as nanoenzymes. Finally, this review discusses the applications of nanobiosensors in the detection of microorganisms and viruses and the future directions of nanobiosensors.

Rapid, Selective, and Ultra-Sensitive Field Effect Transistor-Based Detection of Escherichia coli

Escherichia coli (E. coli) was among the first organisms to have its complete genome published (Genome Sequence of E. coli 1997 Science). It is used as a model system in microbiology research. E. coli can cause life-threatening illnesses, particularly in children and the elderly. Possible contamination by the bacteria also results in product recalls, which, alongside the potential danger posed to individuals, can have significant financial consequences. We report the detection of live Escherichia coli (E. coli) in liquid samples using a biosensor based on a field-effect transistor (FET) biosensor with B/N co-coped reduced graphene oxide (rGO) gel (BN-rGO) as the transducer material. The FET was functionalized with antibodies to detect E. coli K12 O-antigens in phosphate-buffered saline (PBS). The biosensor detected the presence of planktonic E. coli bacterial cells within a mere 2 min. The biosensor exhibited a limit of detection (LOD) of 10 cells per sample, which can be extrapolated to a limit of detection at the level of a single cell per sample and a detection range of at least 10-108 CFU/mL. The selectivity of the biosensor for E. coli was demonstrated using Bacillus thuringiensis (B. thuringiensis) as a sample contaminant. We also present a comparison of our functionalized BN-rGO FET biosensor with established detection methods of E. coli k12 bacteria, as well as with state-of-the-art detection mechanisms.

Green-Synthesized Amino Carbons for Impedimetric Biosensing of E. coli O157:H7

This study describes the synthesis of amino-functionalized carbon nanoparticles derived from biopolymer chitosan using green synthesis and its application toward ultrasensitive electrochemical immunosensor of highly virulent Escherichia coli O157:H7 (E. coli O157:H7). The inherent advantage of high surface-to-volume ratio and enhanced rate transfer kinetics of nanoparticles is leveraged to push the limit of detection (LOD), without compromising on the selectivity. The prepared carbon nanoparticles were systematically characterized by employing CO2-thermal programmed desorption (CO2-TPD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-visible), and transmission electron microscopy (TEM). The estimated limit of detection of 0.74 CFU/mL and a sensitivity of 5.7 ((ΔRct/Rct)/(CFU/mL))/cm2 in the electrochemical impedance spectroscopy (EIS) affirm the utility of the sensor. The proposed biosensor displayed remarkable selectivity against interfering species, making it well suited for real-time applications. Moreover, the chitosan-derived semiconducting amino-functionalized carbon shows excellent sensitivity in a comparative analysis compared to highly conducting amine-functionalized carbon synthesized via chemical modification, demonstrating its vast potential as an E. coli sensor.

Recent advances in electrochemical aptasensors and genosensors for the detection of pathogens

In recent years, pathogenic microorganisms have caused significant mortality rates and antibiotic resistance and triggered exorbitant healthcare costs. These pathogens often have high transmission rates within human populations. Rapid diagnosis is crucial in controlling and reducing the spread of pathogenic infections. The diagnostic methods currently used against individuals infected with these pathogens include relying on outward symptoms, immunological-based and, some biomolecular ones, which mainly have limitations such as diagnostic errors, time-consuming processes, and high-cost platforms. Electrochemical aptasensors and genosensors have emerged as promising diagnostic tools for rapid, accurate, and cost-effective pathogen detection. These bio-electrochemical platforms have been optimized for diagnostic purposes by incorporating advanced materials (mainly nanomaterials), biomolecular technologies, and innovative designs. This review classifies electrochemical aptasensors and genosensors developed between 2021 and 2023 based on their use of different nanomaterials, such as gold-based, carbon-based, and others that employed other innovative assemblies without the use of nanomaterials. Inspecting the diagnostic features of various sensing platforms against pathogenic analytes can identify research gaps and open new avenues for exploration.

A Critical Review on Detection of Foodborne Pathogens Using Electrochemical Biosensors

An outbreak of foodborne pathogens would cause severe consequences. Detecting and diagnosing foodborne diseases is crucial for food safety, and it is increasingly important to develop fast, sensitive, and cost-effective methods for detecting foodborne pathogens. In contrast to traditional methods, such as medium-based culture, nucleic acid amplification test, and enzyme-linked immunosorbent assay, electrochemical biosensors possess the advantages of simplicity, rapidity, high sensitivity, miniaturization, and low cost, making them ideal for developing pathogen-sensing devices. The biorecognition layer, consisting of recognition elements, such as aptamers, antibodies and bacteriophages, and other biomolecules or polymers, is the most critical component to determine the selectivity, specificity, reproducibility, and lifetime of a biosensor when detecting pathogens in a biosample. Furthermore, nanomaterials have been frequently used to improve electrochemical biosensors for sensitively detecting foodborne pathogens due to their high conductivity, surface-to-volume ratio, and electrocatalytic activity. In this review, we survey the characteristics of biorecognition elements and nanomaterials in constructing electrochemical biosensors applicable for detecting foodborne pathogens during the past five years. As well as the challenges and opportunities of electrochemical biosensors in the application of foodborne pathogen detection are discussed.

Recent advances and perspectives of functionalized carbon dots in bacteria sensing

Bacterial infectious diseases are severe threats to human health and increase substantial financial burdens. Nanomaterials have shown great potential in timely and accurate bacterial identification, detection, and monitoring to improve the cure rate and reduce mortality. Recently, carbon dots have been evidenced to be ideal candidates for bacterial identification and detection due to their superior physicochemical properties and biocompatibility. This review outlines the detailed recognition elements and recognition strategies with functionalized carbon dots (FCDs) for bacterial identification and detection. The advantages and limitations of different kinds of FCDs-based sensors will be critically discussed. Meanwhile, the ongoing challenges and perspectives of FCDs-based sensors for bacteria sensing are put forward.

Metal-organic frameworks/metal nanoparticles as smart nanosensing interfaces for electrochemical sensors applications: a mini-review

Metal-organic frameworks (MOFs) are porous materials with huge specific surface area and abundant active sites, which are composed of metal ions or clusters and organic ligands in the form of coordination bonds. In recent years, MOFs have been successfully applied in many fields due to their excellent physical, chemical, and biological properties. Electrochemical sensors have advantages such as economy, portability, and sensitivity, making them increasingly valued in the field of sensors. Many studies have shown that the electrode materials will affect the performance of electrochemical sensors. Therefore, the research on electrode materials is still one of the hotspots. MOFs are also commonly used to construct electrochemical sensors. However, electrochemical sensors prepared from single MOFs have shortcomings such as insufficient conductivity, low sensitivity, and poor electrochemical catalytic ability. In order to compensate for these defects, a new type of nanocomposite material with very ideal conductivity was formed by adding metal nanoparticles (MNPs) to MOFs. The combination of the two is expected to be widely applied in the field of sensors. This review summarizes the applications of various MNPs/MOFs composites in the field of electrochemical sensors and provides some references for the development of MNPs/MOFs composites-based electrochemical sensors in the future.

Strategies in the optimization of DNA hybridization conditions and its role in electrochemical detection of dengue virus (DENV) using response surface methodology (RSM)

In recent years, limited research has been conducted on enhancing DNA hybridization-based biosensor approaches using statistical models. This study explores the application of response surface methodology (RSM) to improve the performance of a DNA hybridization biosensor for dengue virus (DENV) detection. The biosensor is based on silicon nanowires decorated with gold nanoparticles (SiNWs/AuNPs) and utilizes methylene blue as a redox indicator. The DNA hybridization process between the immobilized DNA probe and the target DENV gene was monitored using differential pulse voltammetry (DPV) based on the reduction of methylene blue. Fourier-transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS) were employed to confirm successful DNA hybridization events on the modified screen-printed gold electrode (SPGE) surface. Several parameters, including pH buffer, NaCl concentration, temperature, and hybridization time, were simultaneously optimized, with NaCl concentration having the most significant impact on DNA hybridization events. This study enhances the understanding of the role of each parameter in influencing DNA hybridization detection in electrochemical biosensors. The optimized biosensor demonstrated the ability to detect complementary oligonucleotide and amplified DENV gene concentrations as low as 0.0891 ng µL^-1 (10 pM) and 2.8 ng µL^-1, respectively. The developed biosensor shows promise for rapid clinical diagnosis of dengue virus infection.

Potential Environmental and Health Implications from the Scaled-Up Production and Disposal of Nanomaterials Used in Biosensors

Biosensors often combine biological recognition elements with nanomaterials of varying compositions and dimensions to facilitate or enhance the operating mechanism of the device. While incorporating nanomaterials is beneficial to developing high-performance biosensors, at the stages of scale-up and disposal, it may lead to the unmanaged release of toxic nanomaterials. Here we attempt to foster connections between the domains of biosensors development and human and environmental toxicology to encourage a holistic approach to the development and scale-up of biosensors. We begin by exploring the toxicity of nanomaterials commonly used in biosensor design. From our analysis, we introduce five factors with a role in nanotoxicity that should be considered at the biosensor development stages to better manage toxicity. Finally, we contextualize the discussion by presenting the relevant stages and routes of exposure in the biosensor life cycle. Our review found little consensus on how the factors presented govern nanomaterial toxicity, especially in composite and alloyed nanomaterials. To bridge the current gap in understanding and mitigate the risks of uncontrolled nanomaterial release, we advocate for greater collaboration through a precautionary One Health approach to future development and a movement towards a circular approach to biosensor use and disposal.

Recent Progresses in Electrochemical DNA Biosensors for SARS-CoV-2 Detection

Coronavirus disease 19 (COVID-19) is still a major public health concern in many nations today. COVID-19 transmission is now controlled mostly through early discovery, isolation, and therapy. Because of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the contributing factor to COVID-19, establishing timely, sensitive, accurate, simple, and budget detection technologies for the SARS-CoV-2 is urgent for epidemic prevention. Recently, several electrochemical DNA biosensors have been developed for the rapid monitoring and detection of SARS-CoV-2. This mini-review examines the latest improvements in the detection of SARS-COV-2 utilizing electrochemical DNA biosensors. Meanwhile, this mini-review summarizes the problems faced by the existing assays and puts an outlook on future trends in the development of new assays for SARS-CoV-2, to provide researchers with a borrowing role in the generation of different assays.

Recent Advances in Carbon Dots for In Vitro/Vivo Fluorescent Bioimaging: A Mini-Review

As a new type of "zero-dimensional" fluorescent carbon nanomaterials, carbon dots (CDs) have some unique optical and chemical properties, they are being explored for a variety of applications in bio-related fields, such as bioimaging, biosensors, and therapy. This review mainly summarizes the recent progress of CDs in bioimaging. The overview of this review can be roughly divided into two categories: (1) In vitro bioimaging based on CDs in different cells and important organelles. (2) The distribution, imaging and application of CDs in mice and zebrafish. In addition, this review also points out the potential advantages and future development directions of CDs for bioimaging, which may promote the development of CDs in the field of bioimaging.