Universal colorimetric detection of nucleic acids based on polydiacetylene (PDA) liposomes

A universal colorimetric method for the detection of nucleic acids, based on ionic interactions by polydiacetylene (PDA) liposomes, is described. Primary and quaternary amine-modified diacetylene monomers were synthesized and used to generate positively charged PDA liposomes. The resulting PDA sensors showed a dramatic color change from blue to red upon the addition of nucleic acids amplified by using the polymerase chain reaction (PCR) due to the stimuli caused by ionic interactions between the positively charged PDA and negatively charged phosphate backbone of the nucleic acids. The color change that takes place can be simply detected by the naked eye. Compared with quaternary amine-functionalized PDA vesicles, the primary amine-functionalized PDA underwent a more intense color transition under optimized conditions. By using the PDA-based colorimetric sensor, nucleic acids amplified by common PCR reaction, whose typical concentration is around 100 nM, can be readily detected. Since implementation of this universal colorimetric method is simple, rapid and does not require any sophisticated instrumentation, it should have greatly enhanced applications as a technology for DNA diagnosis.