Target aided self-assembly of DNA hyperbranched nanostructures for bacterial 16 S ribosomal DNA gene SERS detection

Quantity analysis of bacterial 16 S rDNA gene is still a challenge. Here we successfully achieved bacterial 16 S rDNA gene SERS analysis with target aided self-assembly of DNA hyperbranched nanostructures. Catalytic hairpin assembly (CHA) was first introduced for self-assembly of branched nanostructures, including target bacterial DNA served as trigger probe and three hairpin probes for further target activated cross opening. Rolling cycle amplification (RCA) was then introduced by using a circular DNA as template and single stranded branches of the formed branched nanostructures as primer, forming a concatemer containing multiple copies of tandem repeating segments with same sequences complementary to the circular templates. After that, thousands of Raman-Au nanoprobe would hybridize this long single stranded DNAs for DNA-AuNPs nanoaggretates assembly. By using SERS signal collection, target bacterial DNAs would be successfully analyzed with ultra-sensitivity as low as 15.0 fM. Furthermore, selectivity test for targets with mismatched DNA sequences and other bacterial 16 S rDNA genes show good results. This sensing method was extended to quantify target genes in human plasma samples, showing its excellent applicability in complex samples.