ONE-POT COLORIMETRIC DIFFERENTIATION OF POLYNUCLEOTIDES WITH SINGLE-BASE IMPERFECTIONS USING GOLD NANOPARTICLE PROBES

Selective colorimetric polynucleotide detection based on Au nanopartic le probes which align in a ''tail-to-tail'' fashion onto a target poly nucleotide is described. In this new nanoparticle-based detection syst em, Au particles (similar to 13 nm diameter), which are capped with 3' - and 5'-(alkanethiol)oligonucleotides, are used to complex a 24-base polynucleotide target. Hybridization of the target with the probes res ults in the formation of an extended polymeric Au nanoparticle/polynuc leotide aggregate, which triggers a red to purple color change in solu tion. The color change is due to a red shift in the surface plasmon re sonance of the Au nanoparticles. The aggregates exhibit characteristic , exceptionally sharp ''melting transitions'' (monitored at 260 or 700 nm), which allows one to distinguish target sequences that contain on e base end mismatches, deletions, or an insertion from the fully compl ementary target. When test solutions are spotted onto a C18 reverse-ph ase thin-layer chromatography plate, color differentiation is enhanced and a permanent record of the test is obtained, thereby providing a b etter method for distinguishing the aforementioned target sequences. S ignificantly, one-per colorimetric detection of the target in the pres ence of four strands with single base imperfections can be accomplishe d with this new probe system.