Allergen screening bioassays: recent developments in lab-on-a-chip and lab-on-a-disc systems.

Allergies occur when a person's immune system mounts an abnormal response with or without IgE to a normally harmless substance called an allergen. The standard skin-prick test introduces suspected allergens into the skin with lancets in order to trigger allergic reactions. This test is annoying and sometimes life threatening. New tools such as lab-on-a-chip and lab-on-a-disc, which rely on microfabrication, are designed for allergy testing. These systems provide benefits such as short analysis times, enhanced sensitivity, simplified procedures, minimal consumption of sample and reagents and low cost. This article gives a summary of these systems. In particular, a cell-based assay detecting both the IgE- and non-IgE-type triggers through the study of degranulation in a centrifugal microfluidic system is highlighted.

Detection of Panton-Valentine Leukocidin DNA from methicillin-resistant Staphylococcus aureus by resistive pulse sensing and loop-mediated isothermal amplification with gold nanoparticles.

This report describes a novel diagnostic assay for rapid detection of the Panton-Valentine Leukocidin (PVL) toxin of methicillin-resistant Staphylococcus aureus (MRSA) utilizing resistive pulse sensing (RPS), loop-mediated isothermal DNA amplification (LAMP) in combination with gold nanoparticles (AuNPs). The PVL DNA from MRSA was specifically amplified by LAMP using four primers at one temperature (65 °C). The DNA products with biotin were then conjugated to a first AuNP1 (55±2 nm) through biotin-avidin binding. A second AuNP2 (30±1.5 nm) coated with a specific DNA probe hybridized with the LAMP DNA products at the loop region to enhance assay sensitivity and specificity, to generate supra-AuNP1-DNA-AuNP2 assemblies. Scanning electron microscopy confirmed the presence of these supra-assemblies. Using RPS, detection and quantitation of the agglomerated AuNPs were performed by a tunable fluidic nanopore sensor. The results demonstrate that the LAMP-based RPS sensor is sensitive and rapid for detecting the PVL DNA. This technique could achieve a limit of detection (LOD) up to about 500 copies of genomic DNA from the bacteria MRSA MW2 and the detection can be completed within two hours with a straightforward signal-to-readout setup. It is anticipated that this LAMP-based AuNP RPS may become an effective tool for MRSA detection and a potential platform in clinical laboratory to report the presence or absence of other types of infectious agents.