Colorimetric detection of caprine arthritis encephalitis virus (CAEV) through loop-mediated isothermal amplification (LAMP) with gold nanoprobes

Lucero L, Andreus V. Mangahas J, A. Villanueva M, N. Mingala C. Application of Noble Metals in the Advances in Animal Disease Diagnostics

The advent of molecular biology and biotechnology has given ease and comfort for the screening and detection of different animal diseases caused by bacterial, viral, and fungal pathogens. Furthermore, detection of antibiotics and its residues has advanced in recent years. However, most of the process of animal disease diagnostics is still confined in the laboratory. The next step to conduct surveillance and prevent the spread of animal infectious diseases is to detect these diseases in the field. Through the discovery and continuous development in the field of nanobiotechnology, it was found that incorporation of noble metal nanoparticles to biotechnology tools such as the loop-mediated isothermal amplification (LAMP), lateral flow assays (LFAs) and dipsticks provided a promising start to conduct point-of-care diagnostics. Moreover, the modification and application of nanoparticle noble metals has increased the stability, effectiveness, sensitivity and overall efficacy of these diagnostic tools. Thus, recent advances in disease diagnostics used these noble metals such as gold, silver and platinum.

Nanotechnology-based Colorimetric Approaches for Pathogenic Virus Sensing: A review

Fast and inexpensive virus identification protocols are paramount to hinder the further extent of pandemic diseases, minimize economic and social damages, and expedite proper clinical rehabilitation. Until now, various biosensors have been fabricated for the identification of pathogenic particles. But, they offer many difficulties. Nanotechnology resolves these difficulties and offers direct identification of pathogenic species in real-time. Among them, nanomaterial based-colorimetric sensing approach of pathogenic viruses by the naked eye has attracted much awareness because of their simplicity, speed, and low cost. In this review, the latest tendencies and advancements are overviewed in detecting pathogenic viruses using colorimetric concepts. We focus on and reconsider the use of distinctive nanomaterials such as metal nanoparticles, carbon nanotubes, graphene oxide, and conducting polymer to form colorimetric pathogenic virus sensors.

Ultraviolet-induced in situ gold nanoparticles for point-of-care testing of infectious diseases in loop-mediated isothermal amplification

The present study investigated ultraviolet-induced in situ gold nanoparticles (AuNPs) coupled with loop-mediated isothermal amplification (LAMP) for the point-of-care testing (POCT) of two major infectious pathogens, namely, Coronavirus (COVID-19) and Enterococcus faecium (E. faecium spp.). In the process, gold ions in a gold chloride (HAuCl4) solution were reduced using trisodium citrate (Na3Ct), a reducing agent, and upon UV illumination, red-colored AuNPs were produced in the presence of LAMP amplicons. The nitrogenous bases of the target deoxyribonucleic acid (DNA) acted as a physical support for capturing gold ions dissolved in the sample. The high affinity of gold with the nitrogenous bases enabled facile detection within 10 min, and the detection limit of COVID-19 plasmid DNA was as low as 42 fg μL-1. To ensure POCT, we designed a portable device that contained arrays of reagent chambers and detection chambers. In the portable device, colorimetric reagents such as HAuCl4 and Na3Ct were contained in the reagent chambers; these reagents were subsequently transferred to the detection chambers where LAMP amplicons were present and thus allowed convenient sample delivery and multiplex detection. Owing to the high sensitivity of the in situ AuNPs, simplicity of portable device fabrication, and rapid colorimetric detection, we strongly believe that the fabricated portable device could serve as a kit for rapid POCT for instantaneous detection of infectious diseases, and could be readily usable at the bedside.

Visual detection of in vitro nucleic acid replication by submicro- and nano-sized materials

The rapid growth of in vitro nucleic acid replication has offered a powerful tool for clinical diagnosis, food safety detection and environmental monitorning. Successful implementation of various isothermal nucleic acid amplification methods enables rapid replication of target sequences without the participant of a thermal cycler. Point-of-need analysis possesses great superiorities in user-friendly, instant results analysis, low manufacturing, and consumable costs. To meet the great challenge of point-of-need analysis, developing simple and rapid visual methods becomes crucial. Submicro- and nanomaterials possess unique surface properties, which enables their rapid response to DNA amplicons. Their unique optical, magnetic, catalytic, and other physical/chemical properties have been frequently employed for the visual detection of in vitro nucleic acid replications. Herein, we aim to review the submicro- and nanomaterials-based visual methods for detection of nucleic acid amplification. The visual methods are classified according to the designing strategies (e.g. LSPR, bridging flocculation, luminescence, catalytic reaction, separation, etc.). The basic principles, merits and drawbacks of each strategy are described. The application in analysis of nucleic acid targets and non-nucleic acid targets are discussed. The main challenges and future research directions are also highlighted in this rapidly emerging field.

Colorimetric biosensors for point-of-care virus detections

Colorimetric biosensors can be used to detect a particular analyte through color changes easily by naked eyes or simple portable optical detectors for quantitative measurement. Thus, it is highly attractive for point-of-care detections of harmful viruses to prevent potential pandemic outbreak, as antiviral medication must be administered in a timely fashion. This review paper summaries existing and emerging techniques that can be employed to detect viruses through colorimetric assay design with detailed discussion of their sensing principles, performances as well as pros and cons, with an aim to provide guideline on the selection of suitable colorimetric biosensors for detecting different species of viruses. Among the colorimetric methods for virus detections, loop-mediated isothermal amplification (LAMP) method is more favourable for its faster detection, high efficiency, cheaper cost, and more reliable with high reproducible assay results. Nanoparticle-based colorimetric biosensors, on the other hand, are most suitable to be fabricated into lateral flow or lab-on-a-chip devices, and can be coupled with LAMP or portable PCR systems for highly sensitive on-site detection of viruses, which is very critical for early diagnosis of virus infections and to prevent outbreak in a swift and controlled manner.