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

• Naked-eye detection of nucleic acids based on magnetic particle mediated aggregation.
• Long DNA strands (>1 kb) could be visible while short DNA strands could not.
• As little as 0.62 amol (124 fM) of DNA molecules was detected by the naked eye.
• Attempts have been made to detect human papillomavirus type 18 gene in cell lines and blood samples.

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 (>1 kb). As little as 0.62 amol (124 fM) 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.

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