Rapid detection of Campylobacter jejuni using fluorescent microspheres as label for immunochromatographic strip test

Lateral flow assay of pathogenic viruses and bacteria in healthcare

Healthcare-associated pathogenic viruses and bacteria can have a serious impact on human health and have attracted widespread global attention. The lateral flow assay is a unidirectional detection based on the binding of a target analyte and a bioreceptor on the device via lateral flow. With incredible advantages over traditional chromatographic methods, such as rapid detection, ease of manufacture and cost effectiveness, these test strips are increasingly considered the ideal form for point-of-care applications. This review explores lateral flow assays for pathogenic viruses and bacteria, with a particular focus on methodologies, device components, construction methods, and applications. We anticipate that this review could provide exciting opportunities for developing new lateral flow devices for pathogens and advance related healthcare applications.

Rapid quantitative detection of Klebsiella pneumoniae in infants with severe infection disease by point-of-care immunochromatographic technique based on nanofluorescent microspheres

Background: Klebsiella pneumoniae (KP, K. pneumoniae) is one of the most important nosocomial pathogens that cause severe respiratory infections. As evolutionary high-toxic strains with drug resistance genes increase year by year, the infections caused by it are often accompanied by high mortality, which may be fatal to infants and can cause invasive infections in healthy adults. At present, the traditional clinical methods for detecting K. pneumoniae are cumbersome and time-consuming, and the accuracy and sensitivity are not high. In this study, nanofluorescent microsphere (nFM)-based immunochromatographic test strip (ICTS) quantitative testing platform were developed for point-of-care testing (POCT) method of K. pneumoniae. Methods: 19 clinical samples of infants were collected, the genus-specific gene of mdh was screened from K. pneumoniae. Polymerase chain reaction (PCR) combined with nFM-ICTS based on magnetic purification assay (PCR-ICTS) and strand exchange amplification (SEA) combined with nFM-ICTS based on magnetic purification assay (SEA-ICTS) were developed for the quantitative detection of K. pneumoniae. The sensitivity and specificity of SEA-ICTS and PCR-ICTS were demonstrated by the existing used classical microbiological methods, the real-time fluorescent quantitative PCR (RTFQ-PCR) and PCR assay based on agarose gel electrophoresis (PCR-GE). Results: Under optimum working conditions, the detection limits of PCR-GE, RTFQ-PCR, PCR-ICTS and SEA-ICTS are 7.7 × 10^-3, 2.5 × 10^-6, 7.7 × 10^-6, 2.82 × 10^-7 ng/μL, respectively. The SEA-ICTS and PCR-ICTS assays can quickly identify K. pneumoniae, and could specifically distinguish K. pneumoniae samples from non-K. pneumoniae samples. Experiments have shown a diagnostic agreement of 100% between immunochromatographic test strip methods and the traditional clinical methods on the detection of clinical samples. During the purification process, the Silicon coated magnetic nanoparticles (Si-MNPs) were used to removed false positive results effectively from the products, which showed of great screening ability. The SEA-ICTS method was developed based on PCR-ICTS, which is a more rapid (20 min), low-costed method compared with PCR-ICTS assay for the detection of K. pneumoniae in infants. Only need a cheap thermostatic water bath and takes a short detection time, this new method can potentially serve as an efficient point-of-care testing method for on-site detection of pathogens and disease outbreaks without fluorescent polymerase chain reaction instruments and professional technicians operation.

Electrochemical Immuno- and Aptamer-Based Assays for Bacteria: Pros and Cons over Traditional Detection Schemes

Microbiological safety of the human environment and health needs advanced monitoring tools both for the specific detection of bacteria in complex biological matrices, often in the presence of excessive amounts of other bacterial species, and for bacteria quantification at a single cell level. Here, we discuss the existing electrochemical approaches for bacterial analysis that are based on the biospecific recognition of whole bacterial cells. Perspectives of such assays applications as emergency-use biosensors for quick analysis of trace levels of bacteria by minimally trained personnel are argued.

Visual upconversion nanoparticle-based immunochromatographic assay for the semi-quantitative detection of sibutramine

Immunochromatographic assay (ICA) has been used widely for the onsite monitoring of illegal additives due to its simplicity, speed, and low cost. However, a scanner is commonly required for ICA to achieve quantitative results. In this work, we developed a visual semi-quantitative ICA for sibutramine, a banned additive in diet foods, without the need for a scanner for measurement. Monoclonal antibodies specific for sibutramine were raised and conjugated with upconversion nanoparticles (UCNPs) as the luminescent tracer. ICA was developed by employing multiple test lines to achieve the semi-quantitative detection of sibutramine. Based on the optimal conditions, the cutoff levels (limit of quantitation, LOQ) of T1 line, T2 line, T3 line, and T4 line were 0.02 μg/mL, 0.15 μg/mL, 1.0 μg/mL, and 7.5 μg/mL, respectively, in buffer system. The ICA demonstrated a LOQ at 0.2 mg/kg for sibutramine in diet food samples. The assay (including pretreatment) can be finished within 30 min without the aid of other instruments, except a laser pen. No false positive or false negative results were observed. The results indicated that the proposed method was reliable, simple, and rapid for the screening of sibutramine abuse in diet food samples.

Magnetic Lateral Flow Immunoassays

A new generation of magnetic lateral flow immunoassays is emerging as powerful tool for diagnostics. They rely on the use of magnetic nanoparticles (MNP) as detecting label, replacing conventional gold or latex beads. MNPs can be sensed and quantified by means of external devices, allowing the development of immunochromatographic tests with a quantitative capability. Moreover, they have an added advantage because they can be used for immunomagnetic separation (IMS), with improvements in selectivity and sensitivity. In this paper, we have reviewed the current knowledge on magnetic-lateral flow immunoassay (LFIA), coupled with both research and commercially available instruments. The work in the literature has been classified in two categories: optical and magnetic sensing. We have analysed the type of magnetic nanoparticles used in each case, their size, coating, crystal structure and the functional groups for their conjugation with biomolecules. We have also taken into account the analytical characteristics and the type of transduction. Magnetic LFIA have been used for the determination of biomarkers, pathogens, toxins, allergens and drugs. Nanocomposites have been developed as alternative to MNP with the purpose of sensitivity enhancement. Moreover, IMS in combination with other detection principles could also improve sensitivity and limit of detection. The critical analysis in this review could have an impact for the future development of magnetic LFIA in fields requiring both rapid separation and quantification.

Multi-residue fluorescent microspheres immunochromatographic assay for simultaneous determination of macrolides in raw milk

A rapid, reliable, sensitive, and quantitative multi-residue fluorescent microspheres immunochromatographic assay (FMCA) was developed for simultaneous detection of four macrolides in raw milk. The IC50 value of the optimized FMCA was 1.36, 1.22, 1.01, and 1.39 ng/mL for erythromycin (ERY), spiramycin (SPI), tilmicosin (TIM), and tylosin (TYL), respectively. The limits of detection (LODs) for the four macrolides was 0.13 ng/mL. The recoveries of ERY, SPI, TIM, and TYL from spiked raw milk ranged from 91.8-109.2, 89.6-114.4, 84.8-111.6, and 85.8-115.2%, respectively, with coefficients of variation (CVs) of 5.4-11.3, 7.9-15.7, 6.2-13.7, and 3.2-14.9%, respectively. The whole testing process was completed within 20 min. The antibody-mixed labeled method was successfully applied to the FMCA, which greatly simplified the operation steps and saved a lot of time. Compared with the immunogold chromatographic assay (IGCA), the FMCA is more sensitive and stable and has less antibody consumption. A parallel analysis in blind raw milk samples was conducted by liquid chromatography-tandem mass spectrometry (LC-MS/MS); the results showed good correlation (r(2) = 0.99) between the two methods. Therefore, the developed multi-residue FMCA is reliable and can be easily applied to other antibiotics or other contaminants.

Novel strategies to enhance lateral flow immunoassay sensitivity for detecting foodborne pathogens

Food contaminated by foodborne pathogens causes diseases, affects individuals, and even kills those affected individuals. As such, rapid and sensitive detection methods should be developed to screen pathogens in food. One current detection method is lateral flow immunoassay, an efficient technique because of several advantages, including rapidity, simplicity, stability, portability, and sensitivity. This review presents the format and principle of lateral flow immunoassay strip and the development of conventional lateral flow immunoassay for detecting foodborne pathogens. Furthermore, novel strategies that can be applied to enhance the sensitivity of lateral flow immunoassay to detect foodborne pathogens are presented; these strategies include innovating new label application, designing new formats of lateral flow immunoassay, combining with other methods, and developing signal amplification systems. With these advancements, detection sensitivity and detection time can be greatly improved.

Rapid methods for the detection of foodborne bacterial pathogens: principles, applications, advantages and limitations

The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Foodborne pathogens can be found in various foods and it is important to detect foodborne pathogens to provide safe food supply and to prevent foodborne diseases. The conventional methods used to detect foodborne pathogen are time consuming and laborious. Hence, a variety of methods have been developed for rapid detection of foodborne pathogens as it is required in many food analyses. Rapid detection methods can be categorized into nucleic acid-based, biosensor-based and immunological-based methods. This review emphasizes on the principles and application of recent rapid methods for the detection of foodborne bacterial pathogens. Detection methods included are simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray which classified as nucleic acid-based methods; optical, electrochemical and mass-based biosensors which classified as biosensor-based methods; enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay which classified as immunological-based methods. In general, rapid detection methods are generally time-efficient, sensitive, specific and labor-saving. The developments of rapid detection methods are vital in prevention and treatment of foodborne diseases.