A single cell gene detection using micro-tweezers and the microchamber polymerase chain reaction for the fetal DNA analysis

Here, we described a method to analyze a single nucleated fetal erythrocyte by a microchamber array and micro-tweezers. For non-invasive prenatal diagnosis, an extremely small number of fetal nucleated red blood cells need to be properly obtained from the maternal circulation. Fluorescence-activated cell sorting, magnetic-activated cell sorting or charge flow separation is usually used for isolation of fetal cells from maternal blood. However, these methods have low recovery rates, and are plagued by difficulties in accurately isolating fetal cells from maternal cells. Therefore, in this study we used micro-tweezers which were fabricated using micromachining techniques for picking up single fetal cells. The micro-tweezers have two thin probes whose distance can be regulated by applying voltage, and is able to sandwich single cell. This is a manual procedure, and not a high-throughput technique. However, it can obtain single cells accurately, thereby avoiding false-positive results that can occur by including other cells and/or genomic DNA derived from maternal cells. Microchamber PCR was performed to analyze for single fetal cells placed onto a microchamber array by micro-tweezers. Using this method, we successfully amplified the Rhesus blood group D antigen (RhD) gene from a single fetal nucleated red blood cell.