Naked-eye detection of nucleic acids through rolling circle amplification and magnetic particle mediated aggregation

We are presenting a new method for sequence-specific and naked-eye detection of nucleic acids (NAs) through isothermal amplification and magnetic particle mediated aggregation. A padlock probe was designed to hybridize to specific sequence on target genes followed by ligation and rolling circle amplification (RCA). Magnetic particles (MPs) were then added into RCA products solution. MPs would physically combine with long linear DNA coils (such as products of RCA reaction) and form visible intertwined aggregates, while no aggregate was observed in the absence of high molecular weight NAs (>1kb). As little as 0.62amol (124fM) of target DNA molecules was detected by the naked eye. It was further applied to detect human papillomavirus type 18 gene in genomic DNA isolated from HeLa cells. This assay is sensitive and low-cost with minimal instrumentation, revealing great potential for molecular diagnostics in developing countries and regions with limited settings.