Magnetic nanoparticles for pathogen detection.

Instant and sensitive detection of pathogen at ultralow concentrations without time-consuming procedures, such as culture or amplification by PCR, offer obvious advantages. However, there is currently no general and satisfactory assay that could detect bacteria at concentrations of < 100 cfu/mL without pre-enrichment via a culture process. Compared to magnetic beads (1-5 μm in diameter) used in biological separation, magnetic nanoparticles (<10 nm in diameter) promise high performance because of the large surface/volume ratios and easy entry into cells. In 2003, the speaker together with B Xu and Hongwei Gu invented and patented (US7754444B2) an approach involving magnetic iron-platinum nanoparticle and vancomycin as a ligand for bacterial capture for the detection of both Gram positive and Gram negative bacteria at ultra-low concentrations (10-20 cfu/mL). Subsequently, another group has demonstrated that this concept can be implemented on an integrated PCR free microfluidic system for rapid detection of pathogen within 30 minutes. Emerging approaches using magnetic nanoparticles for pathogen detection in clinical, food and environmental samples will be discussed.