Whole cell FRET immunosensor based on graphene oxide and graphene dot for Campylobacter jejuni detection

Recent advances and challenges in graphene-based electrochemical biosensors for food safety

Ensuring food safety is a critical global concern, particularly in light of recent pandemics and rising contamination risks from pesticides, antibiotics, toxins, and allergens. These contaminants pose significant health hazards, including neurological disorders, endocrine disruption, antibiotic resistance, and carcinogenic effects. Regulatory agencies such as the Food and Agriculture Organization (FAO), the World Health Organization (WHO), and the United States Food and Drug Administration (FDA) have established strict maximum residue limits (MRLs) to mitigate these risks. However, enforcement remains challenging due to limitations in current detection methods. The increasing global population and limited food resources have exacerbated food security challenges, while contaminants can infiltrate food at various stages, including production, processing, and packaging. Despite consumer awareness, significant amounts of food are discarded due to quality concerns. To address these issues, researchers are actively developing low-cost, reliable sensing technologies for real-time food quality assessment and contamination detection. Among these, graphene-based electrochemical biosensors have emerged as a promising solution due to their high sensitivity, selectivity, and cost-effectiveness. This review provides an in-depth analysis of recent advancements in graphene-based electrochemical biosensors, focusing on their role in detecting foodborne hazards and improving food quality monitoring. By integrating selective layers, these sensors enhance detection efficiency and provide an innovative solution for safeguarding public health. The findings underscore the transformative potential of graphene-derived biosensors in food safety diagnostics, paving the way for more reliable and sustainable food monitoring systems.

Green emitting carbon dots-immunosensor on magnetic nanoparticles for detection of Nanog antigen as a cancer stem cell biomarker

BACKGROUND

Embryonic Nanog is recognized as a crucial controller of pluripotency. In the progression of cancer and the formation of metastasis, cancer cells with stem cell-like characteristics frequently express Nanog. Precisely identifying the Nanog antigen poses a significant challenge due to its low abundance in biofluids. The precise detection of the Nanog antigen originating from cancer cells has attracted growing interest for its potential uses in diagnostics and prognostics.

RESULTS

In this study, a novel fluorescence strategy utilizing green carbon dots was developed for the highly sensitive and specific detection of Nanog. This approach involved the use of fluoro-immunosensors based on magnetic nanoparticles (MNPs) and antibodies targeting the cancer Stem Cells (CSCs) biomarker, Nanog. In this study, the targeted Nanog was magnetically separated following its reaction with green carbon dots and magnetic nanoparticles, both conjugated with anti-nanog antibodies. The findings show a clear increase in fluorescence with the rising concentration of Nanog antigen in the sample. The linear range for Nanog, measured under optimal experimental conditions, was found to be 5.0 × 10 -11 g/L to 1.0 × 10 -9 g/L. The detection limit (LOD) was calculated to be 1.0 × 10 -11 g/L.

SIGNIFICANCE

This study introduces a fluoro-immunosensor employing magnetic nanoparticles (MNPs) and high quantum efficiency green-emitting carbon dots. This represents the first use of these carbon dots in this type of sensor. The biosensor has demonstrated effective detection of Nanog in biological samples. This developed biosensor, which is both convenient and highly sensitive, presents a significant opportunity for quantifying Nanog in biological research and clinical applications.

Dual-Mode RPA/CRISPR-Cas12a Biosensor Based on Silica and Magnetic Hybrid Nanobeads for Rapid Detection of Campylobacter jejuni

In this study, we developed a biosensor that makes use of recombinase polymerase amplification (RPA) along with a CRISPR/Cas12a system integrated with silica nanobeads and a magnetic nanoparticle nanohybrid complex that displayed peroxidase-mimicking properties. This nanohybrid nanozyme (NZ) integration with the CRISPR/Cas system allowed dual-mode fluorometric and colorimetric responses . The nanohybrid NZ was a conjugated ssDNA quencher probe sequence with inherent fluorometric properties. In the presence of target RPA amplicons, the CRISPR/Cas12a system gets activated, cleaving the probe sequence attached to the NZ complex and leading to fluorescence signal generation. Post-CRISPR/Cas12a assay, the presence of the NZ in the reaction mixture, after being cleaved away from the probe sequence, gave a colourimetric response directly proportional to the target DNA concentration, as the ssDNA probe sequence no longer hindered its catalytic activity. Therefore, the dual-mode detection using the CRISPR/Cas12a-based fluorometric response and NZ-based colorimetric detection conferred high sensitivity and selectivity toward Campylobacter detection. The developed sensor could detect the pathogenic DNA at concentrations as low as 0.98 pg/μL and 0.96 pg/μL via fluorescence and absorbance spectroscopy, respectively. In addition, our method was also tested in raw food analysis and showed good recovery.

A rapid and sensitive sandwich assay for the detection of Alicyclobacillus acidoterrestris in apple juice based on magnetosome immunomagnetic separation combined with quantum dots immunoassay technology

The contamination of apple juice by Alicyclobacillus acidoterrestris (A. acidoterrestris) can cause significant economic losses. Therefore, developing a rapid and sensitive method for detecting A. acidoterrestris is necessary. To address this issue, this study prepared magnetosome-monoclonal antibodies immunomagnetic microspheres (IMMs) as capture probes to enrich A. acidoterrestris (IMMs-Aa) and monoclonal antibodies-quantum dots (mAb-CdTeQDs) as detection probes for detecting A. acidoterrestris. The obtained IMMs-Aa-mAb-CdTeQDs "sandwich" structure was used to detect A. acidoterrestris based on the fluorescence intensity. The strategy presented a good linear correlation (y = 1048× + 1891, R2 = 0.995) between the fluorescence intensity and the concentration of A. acidoterrestris (101-105 CFU/mL) with a low detection limit of 25.4 CFU/mL within 50 min. The recovery rate of this strategy in spiked apple juice ranged from 88.16 % to 107.03 %. Thus, this study established an efficient and highly sensitive magnetic capture-enrichment-separation-detection method for A. acidoterrestris.

Rapid and sensitive whole cell E. coli detection using deep eutectic solvents/graphene oxide/gold nanoparticles field-effect transistor

Every year, millions of people suffer from gastrointestinal inflammation caused by E. coli. The increase of antibiotic-resistant strains and similar inflammatory and infectious syndromes symptoms have made rapid and sensitive diagnosis of this pathogen challenging. This study developed a Field-Effect Transistor based on deep eutectic solvents, graphene oxide, and gold nanoparticles (DES/GO/AuNPs-FET) to detect E. coli. Comparing the output current showed DES, which was a mixture of ethylene glycol and choline chloride, with ionic behavior, in addition to improving the electrical properties of GO, also led to the formation of AuNPs by self-assembly, which significantly increased the sensor's sensing performance. E. coli lipopolysaccharide aptamer immobilized on DES/GO/AuNPs-FET; capturing E. coli and changing the conformation caused changes in the charge carrier flow in the FET. This nanobiosensor detected E. coli in a completely selective manner in complex matrices like human blood serum. The excellent sensing performance of this nanobiosensor compared to other biosensors with a low detection limit (LOD = 3 CFU/ml), label-free, fast, and real-time detection showed that DES/GO/AuNPs-FET could be a reliable alternative to existing detection methods.

Graphene oxide-based fluorescent biosensors for pathogenic bacteria detection: A review

BACKGROUND

Pathogenic bacteria are widespread in nature and can cause infections and various complications, thereby posing a severe risk to public health. Therefore, simple, rapid, sensitive, and cost-effective methods must be developed to detect pathogenic bacteria. Biosensors are prominent platforms for detecting pathogenic bacteria owing to their high sensitivity, specificity, repeatability, and stability. With the development of nanotechnology, graphene oxide (GO) has been increasingly introduced into the construction of fluorescent biosensors to enhance their performance owing to its unique physicochemical properties.

RESULTS

This review systematically summarizes the development of GO-based fluorescent biosensors for the detection of pathogenic bacteria. First, we introduce the functionalization and modification of GO. The design and signal amplification strategies for GO-based fluorescent biosensors are also discussed. Finally, we explore the challenges and new perspectives associated with this field, with the aim of facilitating the development of GO-based fluorescent sensing technologies to prevent the spread of multidrug-resistant bacteria.

SIGNIFICANCE

This review will aid in the development of high-performance biosensors for pathogenic bacterial assays.

Machine learning supported single-stranded DNA sensor array for multiple foodborne pathogenic and spoilage bacteria identification in milk

Ensuring food safety through rapid and accurate detection of pathogenic bacteria in food products is a critical challenge in the food supply chain. In this study, a non-specific optical sensor array was proposed for the identification of multiple pathogenic bacteria in contaminated milk samples. Fluorescence-labeled single-stranded DNA was efficiently quenched by two-dimensional nanoparticles and subsequently recovered by foreign biomolecules. The recovered fluorescence generated a unique fingerprint for each bacterial species, enabling the sensor array to identify eight bacteria (pathogenic and spoilage) within a few hours. Four traditional machine learning models and two artificial neural networks were applied for classification. The neural network showed a 93.8 % accuracy with a 30-min incubation. Extending the incubation to 120 min increased the accuracy of the multiplayer perceptron to 98.4 %. This sensor array is a novel, low-cost, and high-accuracy approach for the identification of multiple bacteria, providing an alternative to plate counting and ELISA methods.

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.

Recent Progress in Nanomaterial-Based Fluorescence Assays for the Detection of Food-Borne Pathogens

Food safety is of great concern, and food-borne bacterial infections and diseases are a major crisis for health. Therefore, it is necessary to develop rapid detection techniques for the prevention and recognition of food safety hazards caused by food-borne pathogens. In recent years, the fluorescence assay has become a widely utilized detection method due to its good signal amplification effect, high detection sensitivity, high stability, and short detection time. In this review, the different kinds of fluorescence materials were concentrated, including quantum dots (QDs), carbon dots (CDs), metal-organic frameworks (MOFs), and upconversion nanoparticles (UCNPs). The optical properties and applications of different kinds of fluorescent materials were analyzed and compared. Furthermore, according to the biosensing components, different fluorescence biosensors are reviewed, including label-free based fluorescence probes, aptamer-based biosensors, and antibody-based biosensors. Finally, we focused our attention on the discussion of fluorescent detection techniques combined with other techniques and their applications. The review presents future trends in fluorescence sensors, providing new sights for the detection of food-borne pathogens.

Biosensor in smart food traceability system for food safety and security

The burden of food contamination and food wastage has significantly contributed to the increased prevalence of foodborne disease and food insecurity all over the world. Due to this, there is an urgent need to develop a smarter food traceability system. Recent advancements in biosensors that are easy-to-use, rapid yet selective, sensitive, and cost-effective have shown great promise to meet the critical demand for onsite and immediate diagnosis and treatment of food safety and quality control (i.e. point-of-care technology). This review article focuses on the recent development of different biosensors for food safety and quality monitoring. In general, the application of biosensors in agriculture (i.e. pre-harvest stage) for early detection and routine control of plant infections or stress is discussed. Afterward, a more detailed advancement of biosensors in the past five years within the food supply chain (i.e. post-harvest stage) to detect different types of food contaminants and smart food packaging is highlighted. A section that discusses perspectives for the development of biosensors in the future is also mentioned.

Biosensors for Monitoring, Detecting, and Tracking Dissemination of Poultry-Borne Bacterial Pathogens Along the Poultry Value Chain: A Review

The poultry industry plays a crucial role in global food production, with chickens being the most widely consumed as a rich protein source. However, infectious diseases pose significant threats to poultry health, underscoring the need for rapid and accurate detection to enable timely intervention. In recent years, biosensors have emerged as essential tools to facilitate routine surveillance on poultry farms and rapid screening at slaughterhouses. These devices provide producers and veterinarians with timely information, thereby promoting proactive disease management. Biosensors have been miniaturized, and portable platforms allow for on-site testing, thereby enhancing biosecurity measures and bolstering disease surveillance networks throughout the poultry supply chain. Consequently, biosensors represent a transformative advancement in poultry disease management, offering rapid and precise detection capabilities that are vital for safeguarding poultry health and ensuring sustainable production systems. This section offers an overview of biosensors and their applications in detecting poultry diseases, with a particular emphasis on enteric pathogens.

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.

Bacterial detection based on Förster resonance energy transfer

The huge economic loss and threat to human health caused by bacterial infection have attracted the public's concern, and there is an urgent need to relieve and improve the tough problem. Therefore, it is significant to establish a facile, rapid, and sensitive method for bacterial detection considering the shortcomings of existing methods. Förster resonance energy transfer (FRET)-based sensors have exhibited immense potential and applicability for bacterial detection given their high signal-to-noise ratio and high sensitivity. This review focuses on the development of FRET-based fluorescence assays for bacterial detection. We summarize the principle of FRET-based assays, discuss the commonly used recognition molecules and further introduce three frequent construction strategies. Based on the strategies and materials, relevant applications are presented. Moreover, some restrictions of FRET fluorescence sensors and development prospects are discussed. Suitable donor-acceptor pairs and stable recognition molecules are the essential conditions for sensors to play their roles, and there is still some room for development. Besides, applying FRET fluorescence sensors to point-of-care detection is still difficult. Future developments could focus on near-infrared fluorescent dyes and simultaneous detection of multiple analytes.

Graphene oxide mediated CdSe quantum dots fluorescent aptasensor for high sensitivity detection of fluoroquinolones

In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5-96.9 % and 90.3-95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection.

Rhodamine B functionalized silver nanoparticles paper discs as turn-on fluorescence sensor, coupled with a smartphone for the detection of microbial contamination in drinking water

The precise detection of pathogenic microorganisms is crucial for the reduction of water-borne diseases. Herein, a filter-paper-based florescent chemosensor was fabricated for the detection of Escherichia coli and Staphylococcus aureus contamination exploiting protein-DNA interaction between the target and a specific probe. The sensing mechanism involved the self-assembly of Rhodamine B (RhB) on silver nanoparticles (AgNPs) surface that was labeled with a single-stranded DNA probe. This causes the fluorescence quenching of RhB by a distant-dependant process. The hybridization between pathogen-specific probe and bacterial surface protein causes the release of fluorescence of RhB, which was observed under UV light. For paper-based bio-surface preparation, the mixture comprising RhB-AgNP-ssDNA was drop-casted on filter paper discs. The conditions were optimized using isolated genomic DNA of the microbes. The method was applied for E.coli detection using an eae gene-based probe targeting intimin protein and S. aureus detection using tuf gene-based probe targeting EF-tuf protein on the microbe's surface. The chemosensor had a notable specificity and selectivity for E.coli, and S. aureus, with detection limits of 0.6 × 108 and 0.37 × 103 CFU/mL respectively. Moreover, the sensor was tested on real water samples, which presented excellent reproducibility of results (RSD ≤ 0.24%). Furthermore, the gradient change of fluorescence was captured by a smartphone, which allows direct detection of pathogens in a sensitive semi-quantitative way without the need for expensive instruments. The designed chemosensor can serve as a simple, inexpensive, and rapid method for the on-site detection of microbial contamination in drinking water.

Fluorescence Resonance Energy Transfer (FRET)-Based Sensor for Detection of Foodborne Pathogenic Bacteria: A Review

Sensitive and rapid determination of foodborne pathogenic bacteria is of practical importance for the control and prevention of foodborne illnesses. Nowadays, with the prosperous development of fluorescence assays, fluorescence resonance energy transfer (FRET)-derived diagnostic strategies are extensively employed in quantitative analysis of different pathogenic bacteria in food-related matrices, which displays a rapid, simple, stable, reliable, cost-effective, selective, sensitive, and real-time way. Considering the extensive efforts that have been made in this field so far, we here discuss the up-to-date developments of FRET-based diagnostic approaches for the determination of key foodborne pathogens like Staphylococcus aureus, Escherichia coli, Vibrio parahaemolyticus, Salmonella spp., Campylobacter spp., and Bacillus cereus in complex food-related matrices. Moreover, the principle of this technology, the choosing standards of acceptor-donor pairs, and the fluorescence properties are also profiled. Finally, the current prospects and challenges in this field are also put forward.

Recent Advances in Optical Sensing for the Detection of Microbial Contaminants

Microbial contaminants are responsible for several infectious diseases, and they have been introduced as important potential food- and water-borne risk factors. They become a global burden due to their health and safety threats. In addition, their tendency to undergo mutations that result in antimicrobial resistance makes them difficult to treat. In this respect, rapid and reliable detection of microbial contaminants carries great significance, and this research area is explored as a rich subject within a dynamic state. Optical sensing serving as analytical devices enables simple usage, low-cost, rapid, and sensitive detection with the advantage of their miniaturization. From the point of view of microbial contaminants, on-site detection plays a crucial role, and portable, easy-applicable, and effective point-of-care (POC) devices offer high specificity and sensitivity. They serve as advanced on-site detection tools and are pioneers in next-generation sensing platforms. In this review, recent trends and advances in optical sensing to detect microbial contaminants were mainly discussed. The most innovative and popular optical sensing approaches were highlighted, and different optical sensing methodologies were explained by emphasizing their advantages and limitations. Consequently, the challenges and future perspectives were considered.

Synthesis, properties and potential applications of photoluminescent carbon nanoparticles: A review

Photoluminescent-carbon nanoparticles (PL-CNPs) are a new class of materials that received immense interest among researchers due to their distinct characteristics, including photoluminescence, high surface-to-volume ratio, low cost, ease of synthesis, high quantum yield, and biocompatibility. By exploiting these outstanding properties, many studies have been reported on its utility as sensors, photocatalysts, probes for bio-imaging, and optoelectronics applications. From clinical applications to point-of-care test devices, drug loading to tracking of drug delivery, and other research innovations demonstrated PL-CNPs as an emerging material that could substitute conventional approaches. However, some of the PL-CNPs have poor PL properties and selectivity due to the presence of impurities (e.g., molecular fluorophores) and unfavourable surface charges by the passivation molecules, which impede their applications in many fields. To address these issues, many researchers have been paying great attention to developing new PL-CNPs with different composite combinations to achieve high PL properties and selectivity. Herein, we thoroughly discussed the recent development of various synthetic strategies employed to prepare PL-CNPs, doping effects, photostability, biocompatibility, and applications in sensing, bioimaging, and drug delivery fields. Moreover, the review discussed the limitations, future direction, and perspectives of PL-CNPs in possible potential applications.

Recent Advances in Fluorescent Nanoprobes for Food Safety Detection

Fluorescent nanoprobes show similar fluorescence properties to traditional organic dyes, but the addition of nanotechnology accurately controls the size, shape, chemical composition, and surface chemistry of the nanoprobes with unique characteristics and properties, such as bright luminescence, high photostability, and strong biocompatibility. For example, modifying aptamers or antibodies on a fluorescent nanoprobe provides high selectivity and specificity for different objects to be tested. Fluorescence intensity, life, and other parameters of targets can be changed by different sensing mechanisms based on the unique structural and optical characteristics of fluorescent nanoprobes. What's more, the detection of fluorescent nanoprobes is cost-saving, simple, and offers great advantages in rapid food detection. Sensing mechanisms of fluorescent nanoprobes were introduced in this paper, focusing on the application progress in pesticide residues, veterinary drug residues, heavy metals, microbes, mycotoxins, and other substances in food safety detection in recent years. A brief outlook for future development was provided as well.

Microfluidic biosensor for one-step detection of multiplex foodborne bacteria ssDNA simultaneously by smartphone

As a major threat to food safety due to their pathogenicity, foodborne bacteria have received much attention. In this paper, we present a one-step and wash-free microfluidic biosensor platform by smartphone for simultaneous multiple foodborne bacteria target single-stranded DNA (ssDNA) detection. This technology is based on the fluorescence resonance energy transfer (FRET) between the graphene oxide (GO) and fluorescence molecules modified capture ssDNA of the target bacteria ssDNA (ctDNA) which were coated on the microfluidic chips. The fluorescence recovery was recorded by a smartphone fluorescent detector. With an optimal analytical performance, the platform realized the detection of four kinds of bacteria ssDNA simultaneously within 5 min, with the limits of detection (LODs) of 0.17, 0.18, 0.27, and 0.17 nM, respectively. And the throughput analysis of trace amounts of foodborne bacteria ssDNA in milk and water samples were successfully detected. This one-step and wash-free microfluidic biosensor can be used as a tool for food safety analysis.

A review of graphene quantum dots and their potential biomedical applications

Today, nanobiotechnology is a pioneering technology in biomedicine. Every day, new nanomaterials are synthesized with elevated physiochemical properties for better diagnosis and treatment of diseases. One advancing class of materials is the Graphene family. Among different kinds of graphene derivatives, graphene quantum dots (GQDs) show fantastic optical, electrical, and electrochemical features originating from their unique quantum confinement effect. Due to the distinct properties of GQD, including large surface-to-volume ratio, low cytotoxicity, and easy functionalization, this nanomaterial has gone popular in biomedical field. Herein, a short overview of different strategies developed for GQD synthesis and functionalization is discussed. In the following, the most recent progress of GQD based nanomaterials in different biomedical fields, including bio-imaging, drug/gene delivery, antimicrobial, tissue engineering, and biosensors, are reviewed.

Two-dimensional nanostructures based '-onics' and '-omics' in personalized medicine

With the maturing techniques for advanced synthesis and engineering of two-dimensional (2D) materials, its nanocomposites, hybrid nanostructures, alloys, and heterostructures, researchers have been able to create materials with improved as well as novel functionalities. One of the major applications that have been taking advantage of these materials with unique properties is biomedical devices, which currently prefer to be decentralized and highly personalized with good precision. The unique properties of these materials, such as high surface to volume ratio, a large number of active sites, tunable bandgap, nonlinear optical properties, and high carrier mobility is a boon to 'onics' (photonics/electronics) and 'omics' (genomics/exposomics) technologies for developing personalized, low-cost, feasible, decentralized, and highly accurate medical devices. This review aims to unfold the developments in point-of-care technology, the application of 'onics' and 'omics' in point-of-care medicine, and the part of two-dimensional materials. We have discussed the prospects of photonic devices based on 2D materials in personalized medicine and briefly discussed electronic devices for the same.

Role of Förster Resonance Energy Transfer in Graphene-Based Nanomaterials for Sensing

Förster resonance energy transfer (FRET)-based fluorescence sensing of various target analytes has been of growing interest in the environmental, bioimaging, and diagnosis fields. Graphene-based zero- (0D) to two-dimensional (2D) nanomaterials, such as graphene quantum dots (GQDs), graphene oxide (GO), reduced graphene oxide (rGO), and graphdiyne (GD), can potentially be employed as donors/acceptors in FRET-based sensing approaches because of their unique electronic and photoluminescent properties. In this review, we discuss the basics of FRET, as well as the role of graphene-based nanomaterials (GQDs, GO, rGO, and GD) for sensing various analytes, including cations, amino acids, explosives, pesticides, biomolecules, bacteria, and viruses. In addition, the graphene-based nanomaterial sensing strategy could be applied in environmental sample analyses, and the reason for the lower detection ranges (micro- to pico-molar concentration) could also be explained in detail. Challenges and future directions for designing nanomaterials with a new sensing approach and better sensing performance will also be highlighted.

Nanoarchitectonics of graphene based sensors for food safety monitoring

Since the desire for the real-time food quality monitoring, plenty of research effort has been made to develop novel tools and to offer extremely efficient detection of food contaminants. Unique electrical, mechanical, and thermal properties make graphene an important material in the field of sensor research. The material can be manufactured into flakes, sheets, films and with its oxidized derivatives could be almost used for a limitless set of application. Herein, current graphene-based sensors for food quality monitoring, novel designs, sensing mechanisms and elements of sensor systems and potential challenges will be outlined and discussed.

Branched poly(ethylenimine) carbon dots-MnO2 nanosheets based fluorescent sensory system for sensing of malachite green in fish samples

Malachite green (MG) is an organic dye compound that is frequently used as a fungicide and antiseptic in aquaculture. However, human or animal exposure to MG causes carcinogenic, teratogenic and mutagenic effects. Herein, a novel fluorescent assay was designed for the detection of MG using manganese dioxide nanosheets (MnO₂ NS) as an energy acceptor to quench the fluorescence of branched poly(ethylenimine) carbon dots (BPEI-CDs) via Förster resonance energy transfer. When butyrylcholinesterase is introduced to form thiocholine in the presence of S-butyrylthiocholine iodide, MnO₂ NS can be recovered by thiocholine to Mn²⁺, resulting in restoration of the fluorescence of BPEI-CDs. Exploiting these changes in fluorescence intensity in the above system, a fluorescence probe was successfully developed for the quantitative detection of MG. Besides, this assay was applied to fish samples, verifying the high potential for practical application of the proposed sensor for the monitoring of MG in aquatic products.

Cerium functionalized graphene nano-structures and their applications; A review

Graphene-based nanomaterials with remarkable properties, such as good biocompatibility, strong mechanical strength, and outstanding electrical conductivity, have dramatically shown excellent potential in various applications. Increasing surface area and porosity percentage, improvement of adsorption capacities, reduction of adsorption energy barrier, and also prevention of agglomeration of graphene layers are the main advantages of functionalized graphene nanocomposites. On the other hand, Cerium nanostructures with remarkable properties have received a great deal of attention in a wide range of fields; however, in some cases low conductivity limits their application in different applications. Therefore, the combination of cerium structures and graphene networks has been widely invesitaged to improve properties of the composite. In order to have a comprehensive information of these nanonetworks, this research reviews the recent developments in cerium functionalized graphene derivatives (graphene oxide (GO), reduced graphene oxide (RGO), and graphene quantum dot (GQD) and their industrial applications. The applications of functionalized graphene derivatives have also been successfully summarized. This systematic review study of graphene networks decorated with different structure of Cerium have potential to pave the way for scientific research not only in field of material science but also in fluorescent sensing, electrochemical sensing, supercapacitors, and catalyst as a new candidate.

Multifunctional carbon nanomaterials for diagnostic applications in infectious diseases and tumors

Infectious diseases (such as Corona Virus Disease 2019) and tumors pose a tremendous challenge to global public health. Early diagnosis of infectious diseases and tumors can lead to effective control and early intervention of the patient's condition. Over the past few decades, carbon nanomaterials (CNs) have attracted widespread attention in different scientific disciplines. In the field of biomedicine, carbon nanotubes, graphene, carbon quantum dots and fullerenes have the ability of improving the accuracy of the diagnosis by the improvement of the diagnostic approaches. Therefore, this review highlights their applications in the diagnosis of infectious diseases and tumors over the past five years. Recent advances in the field of biosensing, bioimaging, and nucleic acid amplification by such CNs are introduced and discussed, emphasizing the importance of their unique properties in infectious disease and tumor diagnosis and the challenges and opportunities that exist for future clinical applications. Although the application of CNs in the diagnosis of several diseases is still at a beginning stage, biosensors, bioimaging technologies and nucleic acid amplification technologies built on CNs represent a new generation of promising diagnostic tools that further support their potential application in infectious disease and tumor diagnosis.

Fluorescent sensor based on quantum dots and nano-porphyrin for highly sensitive and specific determination of ethyl carbamate in fermented food

BACKGROUND

Ethyl carbamate (EC) is a potentially toxic carcinogen produced during fermentation and storage of fermented foods, and many countries have set thresholds for its content in food. Therefore, sensitive, rapid and accurate detection of EC is meaningful to ensure the quality of fermented food.

RESULTS

This study introduces a CdTe quantum dots/nano-5,10,15,20-tetrakis (4-methoxyphenyl)-porphyrin (nano TPP-OCH₃ ) fluorescence sensor system detection of EC. The specificity of this sensing mainly relies on a photo-induced electron transfer and electrostatic force interaction between EC and nano TPP-OCH₃ . This sensor presented a linear range of 10 to 1000 μg L^-1 (R²  = 0.9903) with a low detection limit of 7.14 μg L^-1 . Meanwhile, the recovery (91.19-101.09%) and precision [relative standard deviation (RSD) = 0.64-3.05%] of the sensor for the analysis of fermented food (yellow rice wine, soy sauce, Chinese spirits, Pu-erh tea) samples were good and could meet the requirements of practical detection. Moreover, the detection results of fermented food (yellow rice wine, soy sauce, Chinese spirits, Pu-erh tea) samples by this sensor are basically consistent with those of high-performance liquid chromatography with fluorescence detector (HPLC-FLD).

CONCLUSION

This method was expected to provide a potential platform for sensitive and accurate detection of EC in food safety monitoring, which would provide knowledge of the flavor and quality related to fermented food. © 2021 Society of Chemical Industry.

Recent progress on graphene quantum dots-based fluorescence sensors for food safety and quality assessment applications

The versatile photophysicalproperties, high surface-to-volume ratio, superior photostability, higher biocompatibility, and availability of active sites make graphene quantum dots (GQDs) an ideal candidate for applications in sensing, bioimaging, photocatalysis, energy storage, and flexible electronics. GQDs-based sensors involve luminescence sensors, electrochemical sensors, optical biosensors, electrochemical biosensors, and photoelectrochemical biosensors. Although plenty of sensing strategies have been developed using GQDs for biosensing and environmental applications, the use of GQDs-based fluorescence techniques remains unexplored or underutilized in the field of food science and technology. To the best of our knowledge, comprehensive review of the GQDs-based fluorescence sensing applications concerning food quality analysis has not yet been done. This review article focuses on the recent progress on the synthesis strategies, electronic properties, and fluorescence mechanisms of GQDs. The various GQDs-based fluorescence detection strategies involving Förster resonance energy transfer- or inner filter effect-driven fluorescence turn-on and turn-off response mechanisms toward trace-level detection of toxic metal ions, toxic adulterants, and banned chemical substances in foodstuffs are summarized. The challenges associated with the pretreatment steps of complex food matrices and prospects and challenges associated with the GQDs-based fluorescent probes are discussed. This review could serve as a precedent for further advancement in interdisciplinary research involving the development of versatile GQDs-based fluorescent probes toward food science and technology applications.

Recent advances in FRET-Based biosensors for biomedical applications

Fluorescence resonance energy transfer (FRET)-based biosensors are effective analytical tools extensively used in fields of biomedicine, pharmacology, toxicology, and food sciences. Ratiometric imaging of substantial cellular processes, molecular components, and biological interactions is widely performed by these biosensors. A variety of FRET-based biosensors have provided comprehensive insights into underlying mechanisms of pathological conditions in live cells, tissues, and organisms. Moreover, integration of FRET-based biosensors with the current bioanalytical techniques allows for accurate, rapid, and sensitive diagnosis and proposes the advanced strategies for treatment. Precise analysis of ligand-receptor interactions by FRET-based biosensors has presented a basis for determination of novel therapeutic agents. Therefore, this study was designed to review the recent developments in FRET-based biosensors and their biomedical applications. In addition, characteristics, challenges, and outlooks of these biosensors were discussed.

Function-Oriented Graphene Quantum Dots Probe for Single Cell in situ Sorting of Active Microorganisms in Environmental Samples

Functional microorganisms play a vital role in removing environmental pollutants because of their diverse metabolic capability. Herein, a function-oriented fluorescence resonance energy transfer (FRET)-based graphene quantum dots (GQDs-M) probe was developed for the specific identification and accurate sorting of azo-degrading functional bacteria in the original location of environmental samples for large-scale culturing. First, nitrogen-doped GQDs (GQDs-N) were synthesized using a bottom-up strategy. Then, a GQDs-M probe was synthesized based on bonding FRET-based GQDs-N to an azo dye, methyl red, and the quenched fluorescence was recovered upon cleavage of the azo bond. Bioimaging confirmed the specific recognition capability of GQDs-M upon incubation with the target bacteria or environmental samples. It is suggested that the estimation of environmental functional microbial populations based on bioimaging will be a new method for rapid preliminary assessment of environmental pollution levels. In combination with a visual single-cell sorter, the target bacteria in the environmental samples could be intuitively screened at the single-cell level in 17 bacterial strains, including the positive control Shewanella decolorationis S12, and were isolated from environmental samples. All of these showed an azo degradation function, indicating the high accuracy of the single-cell sorting strategy using the GQDs-M. Furthermore, among the bacteria isolated, two strains of Bacillus pacificus and Bacillus wiedmannii showed double and triple degradation efficiency for methyl red compared to the positive control (strain S12). This strategy will have good application prospects for finding new species or high-activity species of specific functional bacteria.

Sensitive detection of S. Aureus using aptamer- and vancomycin -copper nanoclusters as dual recognition strategy

The proposed aptamer- and antibiotic-based dual detection sensor, combines copper nanoclusters (CuNCs) as an effective approach for the recognition and quantification of Staphylococcus aureus (S. aureus) as a pathogenic bacteria. A facile method for CuNCs based on vancomycin as the template using a fluorescence platform was proposed for the recognition of the S. aureus whole cells via antibiotic and aptamer. Using dual receptor functionalized CuNCs linked to vancomycin and a specific aptamer and during aggregation induce emission process enhanced fluorescence signal linearly with S. aureus concentrations between 10²-10⁸ CFU/mL, and the detection limit was 80 CFU/mL after 45 min as the optimum incubation time. Non-target bacteria generated negative results, proving the high specificity of the presented sensor. This strategy showed recoveries ranging 86%-98% in milk as real sample and can be used for the development of universal detection platforms for efficient and specific S. aureus detection with great potential applications for monitoring pathogenic bacteria.

Advances in airborne microorganisms detection using biosensors: A critical review

Humanity has been facing the threat of a variety of infectious diseases. Airborne microorganisms can cause airborne infectious diseases, which spread rapidly and extensively, causing huge losses to human society on a global scale. In recent years, the detection technology for airborne microorganisms has developed rapidly; it can be roughly divided into biochemical, immune, and molecular technologies. However, these technologies still have some shortcomings; they are time-consuming and have low sensitivity and poor stability. Most of them need to be used in the ideal environment of a laboratory, which limits their applications. A biosensor is a device that converts biological signals into detectable signals. As an interdisciplinary field, biosensors have successfully introduced a variety of technologies for bio-detection. Given their fast analysis speed, high sensitivity, good portability, strong specificity, and low cost, biosensors have been widely used in environmental monitoring, medical research, food and agricultural safety, military medicine and other fields. In recent years, the performance of biosensors has greatly improved, becoming a promising technology for airborne microorganism detection. This review introduces the detection principle of biosensors from the three aspects of component identification, energy conversion principle, and signal amplification. It also summarizes its research and application in airborne microorganism detection. The new progress and future development trend of the biosensor detection of airborne microorganisms are analyzed.

Metabolic integration of azide functionalized glycan on Escherichia coli cell surface for specific covalent immobilization onto magnetic nanoparticles with click chemistry

A method for specific immobilization of whole-cell with covalent bonds was developed through a click reaction between alkyne and azide groups. In this approach, magnetic nanoparticle Fe₃O₄@SiO₂-NH₂-alkyne was synthesized with Fe₃O₄ core preparation, SiO₂ coating, and alkyne functionalization on the surface. The azides were successfully integrated onto the cell surface of the recombinant E. coli harboring glycerol dehydrogenase, which was employed as the model cell. The highest immobilization yield of 83% and activity recovery of 94% were obtained under the conditions of 0.67 mg mg^-1 cell-support ratio, pH 6.0, temperature 45 °C, and 20 mM Cu²⁺ concentration. The immobilized cell showed good reusability, which remained over 50% of initial activity after 10 cycles of utilization. Its activity was 9.7-fold higher than that of the free cell at the condition of pH 8.0 and each optimal temperature. Furthermore, the immobilized cell showed significantly higher activity, operational stability, and reusability.