Magnetic bead-based DNA detection with multi-layers quantum dots labeling for rapid detection of Escherichia coli O157:H7

A novel fluorescence immunoassay for the quantitative detection of florfenicol in animal-derived foods based on ZnCdSe/ZnS quantum dot labelled antibody

Florfenicol (F), an antimicrobial agent exclusive to veterinary use within the chloramphenicol class, is extensively applied as a broad-spectrum remedy for animal diseases. Despite its efficacy, concerns arise over potential deleterious residues in animal-derived edibles, posing threats to human health. This study pioneers an innovative approach, introducing a quantum dot fluorescence-based immunoassay (FLISA) for the meticulous detection of F residues in animal-derived foods and feeds. This method demonstrates heightened sensitivity, with a detection limit of 0.3 ng/mL and a quantitative detection range of 0.6-30.4 ng/mL. Method validation, applied to diverse food sources, yields recoveries from 90.4 % to 109.7 %, featuring RSDs within 1.3 % to 8.7 %, the results showed high consistency with the national standard HPLC-MS/MS detection method. These findings underscore the method's accuracy and precision, positioning it as a promising tool for swift and reliable F residue detection, with substantial implications for fortifying food safety monitoring.

On-site detection of OTA and AFB1 based on branched hybridization chain reaction coupled with lateral flow assay

Mycotoxins are widely prevalent in various agricultural commodities, whose excessive consumption can pose significant risks to human health. In this study, we developed a facile mycotoxin detection platform based on branched hybridization chain reaction coupled with lateral flow assay. Ochratoxin A/Aflatoxin B1 bind to aptamers triggering the release of initiators, which leads to bHCR amplification and forms three-dimensional dendritic DNA nanostructures. Using the functionalized quantum dots as a fluorescent label, by leveraging smartphones and handheld ultraviolet lamps, the qualitative and quantitative detection of OTA and AFB1 can be achieved with a significantly enhanced sensitivity level, surpassing that of commercial test strips by 2-3 orders of magnitude. The visual detection limits for OTA and AFB1 were 30 pg/mL and 4 pg/mL, respectively. This approach eliminates the necessity for enzyme catalysis or the preparation and purification of antibodies and/or hapten, thereby reducing testing expenses and streamlining operational procedures. Moreover, substituting aptamer and nucleic acid sequences can effectively expand the scope of detection targets. Consequently, the as-proposed strategy exhibits great potential as a versatile technique, suitable for various analytical scenarios due to its sensitivity, accuracy, simplicity, and portability.

Nanomaterials-based electrochemical biosensors for diagnosis of COVID-19

Since the outbreak of corona virus disease 2019 (COVID-19), this pandemic has caused severe death and infection worldwide. Owing to its strong infectivity, long incubation period, and nonspecific symptoms, the early diagnosis is essential to reduce risk of the severe illness. The electrochemical biosensor, as a fast and sensitive technique for quantitative analysis of body fluids, has been widely studied to diagnose different biomarkers caused at different infective stages of COVID-19 virus (SARS-CoV-2). Recently, many reports have proved that nanomaterials with special architectures and size effects can effectively promote the biosensing performance on the COVID-19 diagnosis, there are few comprehensive summary reports yet. Therefore, in this review, we will pay efforts on recent progress of advanced nanomaterials-facilitated electrochemical biosensors for the COVID-19 detections. The process of SARS-CoV-2 infection in humans will be briefly described, as well as summarizing the types of sensors that should be designed for different infection processes. Emphasis will be supplied to various functional nanomaterials which dominate the biosensing performance for comparison, expecting to provide a rational guidance on the material selection of biosensor construction for people. Finally, we will conclude the perspective on the design of superior nanomaterials-based biosensors facing the unknown virus in future.

Magnetic biosensors for identification of SARS-CoV-2, Influenza, HIV, and Ebola viruses: a review

Infectious diseases such as novel coronavirus (SARS-CoV-2), Influenza, HIV, Ebola, etc kill many people around the world every year (SARS-CoV-2 in 2019, Ebola in 2013, HIV in 1980, Influenza in 1918). For example, SARS-CoV-2 has plagued higher than 317 000 000 people around the world from December 2019 to January 13, 2022. Some infectious diseases do not yet have not a proper vaccine, drug, therapeutic, and/or detection method, which makes rapid identification and definitive treatments the main challenges. Different device techniques have been used to detect infectious diseases. However, in recent years, magnetic materials have emerged as active sensors/biosensors for detecting viral, bacterial, and plasmids agents. In this review, the recent applications of magnetic materials in biosensors for infectious viruses detection have been discussed. Also, this work addresses the future trends and perspectives of magnetic biosensors.

Nucleic acid amplification-free detection of DNA and RNA at ultralow concentration

The broad spectrum of approaches for nucleic acid amplification-free detection of DNA and RNA at single-digit attomolar (10^-18 M) concentration and lower is reviewed. These low concentrations correspond roughly to the most clinically desirable detection range for pathogen-specific nucleic acid as well as the detection limits of commercially available, nucleic acid amplification tests based primarily on polymerase chain reaction (PCR). The need for more rapid and inexpensive, yet still highly accurate tests, has become evident during the pandemic. It is expected that publication of reports describing improved tests will accelerate soon, and this review covers the wide variety of detection methods based on both optical and electrical measurements that have been conceived over recent years, enabled generally by the advent of nanotechnology.

A Review on Microfluidics: An Aid to Assisted Reproductive Technology

Infertility is a state of the male or female reproductive system that is defined as the failure to achieve pregnancy even after 12 or more months of regular unprotected sexual intercourse. Assisted reproductive technology (ART) plays a crucial role in addressing infertility. Various ART are now available for infertile couples. Fertilization in vitro (IVF), intracytoplasmic sperm injection (ICSI) and intrauterine insemination (IUI) are the most common techniques in this regard. Various microfluidic technologies can incorporate various ART procedures such as embryo and gamete (sperm and oocyte) analysis, sorting, manipulation, culture and monitoring. Hence, this review intends to summarize the current knowledge about the application of this approach towards cell biology to enhance ART.

Applications of electrowetting-on-dielectric (EWOD) technology for droplet digital PCR

Digital microfluidics is an elegant technique based on single droplets for the design, composition, and manipulation of microfluidic systems. In digital microfluidics, especially in the electrowetting on dielectric (EWOD) system, each droplet acts as an independent reactor, which enables a wide range of multiple parallel biological and chemical reactions at the microscale. EWOD digital microfluidics reduces reagent and energy consumption, accelerates analysis, enables point-of-care diagnostic, simplifies integration with sensors, etc. Such a digital microfluidic system is especially relevant for droplet digital PCR (ddPCR), thanks to its nanoliter droplets and well-controlled volume distribution. At low DNA concentration, these small volumes allow less than one DNA strand per droplet on average (limited dilution) so that after a fixed number of PCR cycles (endpoint PCR), only the DNA in droplets containing the sequence of interest has been amplified and can be detected by fluorescence to yield an accurate count of the sequences of interest using statistical models. Focusing on ddPCR, this article summarizes the latest development and research on EWOD technology for droplet PCR over the last decade.

An Overview of the Applications of Nanomaterials and Nanodevices in the Food Industry

The efficient progress in nanotechnology has transformed many aspects of food science and the food industry with enhanced investment and market share. Recent advances in nanomaterials and nanodevices such as nanosensors, nano-emulsions, nanopesticides or nanocapsules are intended to bring about innovative applications in the food industry. In this review, the current applications of nanotechnology for packaging, processing, and the enhancement of the nutritional value and shelf life of foods are targeted. In addition, the functionality and applicability of food-related nanotechnologies are also highlighted and critically discussed in order to provide an insight into the development and evaluation of the safety of nanotechnology in the food industry.

Guanine-guided time-resolved luminescence recognition of DNA modification and i-motif formation by a terbium(III)-platinum(II) complex

Site-specific recognition of DNA modification or the formation of noncanonical structures has important applications in molecular biology, disease diagnosis, and gene expression analysis. In this study, we introduce a guanine-guided sensing tool using a terbium(III)-platinum(II) complex (TPC) as a time-resolved luminescence probe to site-specifically recognize DNA modification and i-motif formation in aqueous solution. The probe is composed of a Tb^III center as the luminescent reporter and two Pt^II units as the receptor for guanine (G) nucleobase. TPC exhibits remarkable reaction selectivity for guanine nucleotides over other nucleotides, giving rise to a significant increase in luminescence. The luminescence enhancement of TPC is mainly attributed to an energy transfer from G base to the Tb^III center after the specific coordination of Pt^II with N7 of guanine (N7-G), which would be facilitated by the phosphates through promoting the departure of coordinated water and bringing G closer to Tb^IIIvia noncovalent interactions. Based on such sensing feature, the enhanced luminescence of TPC sensitized by G nucleotides can correspondingly decrease upon N7-G modifications of DNA or i-motif formation through constructing simple guanine-guided sensing tools. This probe would provide a useful strategy for site-specific recognition of DNA for extensive purposes.

Quantitative and multiplexed detection for blood typing based on quantum dot-magnetic bead assay

Background

Accurate and reliable blood grouping is essential for safe blood transfusion. However, conventional methods are qualitative and use only single-antigen detection. We overcame these limitations by developing a simple, quantitative, and multiplexed detection method for blood grouping using quantum dots (QDs) and magnetic beads.

Methods

In the QD fluorescence assay (QFA), blood group A and B antigens were quantified using QD labeling and magnetic beads, and the blood groups were identified according to the R value (the value was calculated with the fluorescence intensity from dual QD labeling) of A and B antigens. The optimized performance of QFA was established by blood typing 791 clinical samples.

Results

Quantitative and multiplexed detection for blood group antigens can be completed within 35 min with more than 10⁵ red blood cells. When conditions are optimized, the assay performance is satisfactory for weak samples. The coefficients of variation between and within days were less than 10% and the reproducibility was good. The ABO blood groups of 791 clinical samples were identified by QFA, and the accuracy obtained was 100% compared with the tube test. Receiver-operating characteristic curves revealed that the QFA has high sensitivity and specificity toward clinical samples, and the cutoff points of the R value of A and B antigens were 1.483 and 1.576, respectively.

Conclusion

In this study, we reported a novel quantitative and multiplexed method for the identification of ABO blood groups and presented an effective alternative for quantitative blood typing. This method can be used as an effective tool to improve blood typing and further guarantee clinical transfusion safety.

Magnetic micro/nanoparticle flocculation-based signal amplification for biosensing

We report a time and cost efficient signal amplification method for biosensors employing magnetic particles. In this method, magnetic particles in an applied external magnetic field form magnetic dipoles, interact with each other, and accumulate along the magnetic field lines. This magnetic interaction does not need any biomolecular coating for binding and can be controlled with the strength of the applied magnetic field. The accumulation can be used to amplify the corresponding pixel area that is obtained from an image of a single magnetic particle. An application of the method to the Escherichia coli 0157:H7 bacteria samples is demonstrated in order to show the potential of the approach. A minimum of threefold to a maximum of 60-fold amplification is reached from a single bacteria cell under a magnetic field of 20 mT.

Fertilization of Mouse Gametes in Vitro Using a Digital Microfluidic System

We demonstrated in vitro fertilization (IVF) using a digital microfluidic (DMF) system, so-called electrowetting on dielectric (EWOD). The DMF device was proved to be biocompatible and the DMF manipulation of a droplet was harmless to the embryos. This DMF platform was then used for the fertilization of mouse gametes in vitro and for embryo dynamic culture based on a dispersed droplet form. Development of the embryos was instantaneously recorded by a time-lapse microscope in an incubator. Our results indicated that increasing the number of sperms for IVF would raise the rate of fertilization. However, the excess of sperms in the 10 μL culture medium would more easily make the embryo dead during cell culture. Dynamic culture powered with EWOD can manipulate a single droplet containing mouse embryos and culture to the eight-cell stage. The fertilization rate of IVF demonstrated by DMF system was 34.8%, and about 25% inseminated embryos dynamically cultured on a DMF chip developed into an eight-cell stage. The results indicate that the DMF system has the potential for application in assisted reproductive technology.

Nucleic-acid testing, new platforms and nanotechnology for point-of-decision diagnosis of animal pathogens

Accurate disease diagnosis in animals is crucial for animal well-being but also for preventing zoonosis transmission to humans. In particular, livestock diseases may constitute severe threats to humans due to the particularly high physical contact and exposure and, also, be the cause of important economic losses, even in non-endemic countries, where they often arise in the form of rapid and devastating epidemics. Rapid diagnostic tests have been used for a long time in field situations, particularly during outbreaks. However, they mostly rely on serological approaches, which may confirm the exposure to a particular pathogen but may be inappropriate for point-of-decision (point-of-care) settings when emergency responses supported on early and accurate diagnosis are required. Moreover, they often exhibit modest sensitivity and hence significantly depend on later result confirmation in central or reference laboratories. The impressive advances observed in recent years in materials sciences and in nanotechnology, as well as in nucleic-acid synthesis and engineering, have led to an outburst of new in-the-bench and prototype tests for nucleic-acid testing towards point-of-care diagnosis of genetic and infectious diseases. Manufacturing, commercial, regulatory, and technical nature issues for field applicability more likely have hindered their wider entrance into veterinary medicine and practice than have fundamental science gaps. This chapter begins by outlining the current situation, requirements, difficulties, and perspectives of point-of-care tests for diagnosing diseases of veterinary interest. Nucleic-acid testing, particularly for the point of care, is addressed subsequently. A range of valuable signal transduction mechanisms commonly employed in proof-of-concept schemes and techniques born on the analytical chemistry laboratories are also described. As the essential core of this chapter, sections dedicated to the principles and applications of microfluidics, lab-on-a-chip, and nanotechnology for the development of point-of-care tests are presented. Microdevices already applied or under development for application in field diagnosis of animal diseases are reviewed.

Rapid pathogen detection with bacterial-assembled magnetic mesoporous silica

We report rapid and accurate pathogen detection by coupling with high efficiency magnetic separation of pathogen by Ni(2+)-heterogeneous magnetic mesoporous silica (Ni-HMMS) and real time-polymerase chain reaction (RT-PCR) technique. Ni-HMMS was developed with a significant incorporation of Fe particles within the silica mesopores by programmed thermal hydrogen reaction and functionalized with Ni(2+) ion on the surface by the wet impregnation process. High abundant Ni(2+) ions on the Ni-HMMS surface were able to assemble with cell wall component protein NikA (nickel-binding membrane protein), which contains several pathogenic bacteria including Escherichia coli O157:H7. NikA protein expression experiment showed the outstanding separation rate of the nikA gene-overexpressed E. coli (pSY-Nik) when comparing with wild-type E. coli (44.5 ± 13%) or not over-expressed E. coli (pSY-Nik) (53.2 ± 2.7%). Moreover, Ni-HMMS showed lower obstacle effect by large reaction volume (10 mL) than spherical core/shell-type silica magnetic nanoparticles functionalized with Ni(2+) (ca. 40 nm-diameters). Finally, the Ni-HMMS was successfully assessed to separate pathogenic E. coli O157:H7 and applied to direct and rapid RT-PCR to quantitative detection at ultralow concentration (1 Log10 cfu mL(-1)) in the real samples (milk and Staphylococcus aureus culture broth) without bacterial amplification and DNA extraction step.

New trends in impedimetric biosensors for the detection of foodborne pathogenic bacteria

The development of a rapid, sensitive, specific method for the foodborne pathogenic bacteria detection is of great importance to ensure food safety and security. In recent years impedimetric biosensors which integrate biological recognition technology and impedance have gained widespread application in the field of bacteria detection. This paper presents an overview on the progress and application of impedimetric biosensors for detection of foodborne pathogenic bacteria, particularly the new trends in the past few years, including the new specific bio-recognition elements such as bacteriophage and lectin, the use of nanomaterials and microfluidics techniques. The applications of these new materials or techniques have provided unprecedented opportunities for the development of high-performance impedance bacteria biosensors. The significant developments of impedimetric biosensors for bacteria detection in the last five years have been reviewed according to the classification of with or without specific bio-recognition element. In addition, some microfluidics systems, which were used in the construction of impedimetric biosensors to improve analytical performance, are introduced in this review.

Electrochemical biosensor for rapid and sensitive detection of magnetically extracted bacterial pathogens

Biological defense and security applications demand rapid, sensitive detection of bacterial pathogens. This work presents a novel qualitative electrochemical detection technique which is applied to two representative bacterial pathogens, Bacillus cereus (as a surrogate for B. anthracis) and Escherichia coli O157:H7, resulting in detection limits of 40 CFU/mL and 6 CFU/mL, respectively, from pure culture. Cyclic voltammetry is combined with immunomagnetic separation in a rapid method requiring approximately 1 h for presumptive positive/negative results. An immunofunctionalized magnetic/polyaniline core/shell nano-particle (c/sNP) is employed to extract target cells from the sample solution and magnetically position them on a screen-printed carbon electrode (SPCE) sensor. The presence of target cells significantly inhibits current flow between the electrically active c/sNPs and SPCE. This method has the potential to be adapted for a wide variety of target organisms and sample matrices, and to become a fully portable system for routine monitoring or emergency detection of bacterial pathogens.

Microchip integrating magnetic nanoparticles for allergy diagnosis

We report on the development of a simple and easy to use microchip dedicated to allergy diagnosis. This microchip combines both the advantages of homogeneous immunoassays i.e. species diffusion and heterogeneous immunoassays i.e. easy separation and preconcentration steps. In vitro allergy diagnosis is based on specific Immunoglobulin E (IgE) quantitation, in that way we have developed and integrated magnetic core-shell nanoparticles (MCSNPs) as an IgE capture nanoplatform in a microdevice taking benefit from both their magnetic and colloidal properties. Integrating such immunosupport allows to perform the target analyte (IgE) capture in the colloidal phase thus increasing the analyte capture kinetics since both immunological partners are diffusing during the immune reaction. This colloidal approach improves 1000 times the analyte capture kinetics compared to conventional methods. Moreover, based on the MCSNPs' magnetic properties and on the magnetic chamber we have previously developed the MCSNPs and therefore the target can be confined and preconcentrated within the microdevice prior to the detection step. The MCSNPs preconcentration factor achieved was about 35,000 and allows to reach high sensitivity thus avoiding catalytic amplification during the detection step. The developed microchip offers many advantages: the analytical procedure was fully integrated on-chip, analyses were performed in short assay time (20 min), the sample and reagents consumption was reduced to few microlitres (5 μL) while a low limit of detection can be achieved (about 1 ng mL(-1)).

Label free DNA detection based on gold nanoparticles quenching fluorescence of Rhodamine B

A novel and sensitive label free DNA detection method using gold nanoparticles (GNPs) and Rhodamine B (RB) has been developed. The assay is based on the following two properties. One is the different adsorption properties of single-stranded and double-stranded DNA on GNPs in colloidal solution. The other is the different quenching ability of aggregated GNPs and dispersed GNPs on RB. Un-aggregated GNPs could effectively quench the fluorescence of RB. However, the quenching ability greatly decreases after GNPs aggregated. The hybridization of probe DNA and target DNA is monitored by the fluorescence detection after the RB is added to the solution. Under the optimal experimental conditions, the detection limit of this assay is 2.9×10(-13) mol L(-1).

Fluorescently imaged particle counting immunoassay for sensitive detection of DNA modifications

Modifications of genomic DNA may change gene expression and cause adverse health effects. Here we for the first time demonstrate a particle counting immunoassay for rapid and sensitive detection of DNA modifications using benzo[a]pyrenediol epoxide (BPDE)-DNA adducts as an example. The BPDE-adducted DNA is specifically captured by immunomagnetic particles and then isolated from unmodified DNA by applying an external magnetic field. By taking advantage of the fluorescence signal amplification through multiple labeling of captured DNA by OliGreen dye, the captured BPDE-DNA adducts can be quantified by particle counting from fluorescence imaging. This clearly demonstrates that the number of fluorescently countable particles is proportional to the modification content in genomic DNA. It is interesting to note that the background fluorescence signal caused by nonspecific adsorption of OliGreen dye can be more effectively quenched than that induced by the binding of OliGreen dye to ssDNA, allowing for significant reduction in the background fluorescence and further enhancing the detection sensitivity. The developed method can detect trace BPDE-DNA adducts as low as 180 fM in the presence of 1 billion times more normal nucleotides in genomic DNA and has a dynamic range over 4 orders of magnitude. By using anti-5-methylcytosine antibody, the method is extended to the detection of global DNA methylation. With high sensitivity and specificity, this rapid and easy-to-perform analytical method for DNA modifications shows a broad spectrum of potential applications in genotoxical and epigenetic analysis.

Magnetic beads based rolling circle amplification-electrochemiluminescence assay for highly sensitive detection of point mutation

The identification of point mutations is particularly essential in the fields of medical diagnosis and prognosis of many pathogenic and genetic diseases. In this study, an rolling circle amplification (RCA) based electrochemiluminescence (ECL) assay for highly sensitive point mutation detection was developed. In the assay, an allele-discriminating padlock probe was designed for targeting the sequence in the p53 oncogene locus. A circular template generated by enzymatic ligation upon the recognition of a point mutation (CGT to CAT) on the oncogene could be amplified isothermally by Phi 29 DNA polymerase. The elongated products, containing hundreds of copies of the circular DNA template sequence, were hybridized with Ru(bpy)(3)(2+) (TBR)-tagged probes and then captured onto streptavidin-coated paramagnetic beads. The resulting products were analyzed by magnetic bead based ECL platform. As low as 2 amol of mutated strands was detected by this assay, which could be attributed to the high amplification efficiency of Phi 29 DNA polymerase and current magnetic bead based ECL detection platform. In addition, the positive mutation detection was achieved with a wild-type to mutant ratio of 10000:1, due to the high fidelity of DNA ligase in differentiating mismatched bases at the ligation site. It is demonstrated that this proposed method provides a highly sensitive and specific approach for point mutation detection.

Sensitivity enhancement in DNA hybridization assay using gold nanoparticle-labeled two reporting probes

A simple and sensitive method for DNA detection using gold nanoparticle (AuNP) two-probe detection system (AuNP-TP) was developed. Preliminary experiment was carried out by optimizing slide types, blocking agents and hybridization times. Fluorescent-labeled probes were used along with AuNP-labeled probes to confirm specific binding event between target DNA and probes. The sensitivities between AuNP single-probe (AuNP-SP) and AuNP-TP systems using sandwich-typed assay were compared. The AuNP-TP on epoxide-coated (EP) slides increased sensitivity 1000-fold at the detection limit of 100fM when compared to the AuNP-SP. This result indicates that the assay sensitivity was simply enhanced by simultaneous adding two AuNP labeled probes which selectively recognize different regions of the target DNA. The concept of AuNP-TP could potentially be applied to a macroarray format to detect multiple DNA targets simultaneously; thereby making the assay becomes more affordable and more sensitive.