Femtomol SPR detection of DNA-PNA hybridization with the assistance of DNA-guided polyaniline deposition.
The inability of surface plasmon resonance (SPR) spectroscopy to detect extremely small refractive index changes has hindered its applications in ultrasensitive DNA analysis. In this study we report a signal amplification strategy that uses DNA-templated polyaniline deposition, suitable for DNA hybridization analysis with charge neutral peptide nucleic acid (PNA) being probes. Under acidic conditions, protonated aniline monomers are adsorbed on DNA backbones through electrostatic interaction. The microenvironment provided by the DNA facilitates oxidative aniline polymerization initialized by H(2)O(2) in the presence of horseradish peroxide. Under optimal conditions, the detection limit is lowered from 5nM for conventional SPR detection to 0.1pM. The significant sensitivity improvement is attributed to the in-situ polymer chain growth along DNA strands, which introduces drastic refractive index increases. This signal amplification approach does not involve secondary hybridization processes. The detection sensitivity obtained is much better than that of gold nanoparticle-based amplification involving a secondary hybridization process and labeled DNA detection probes.
Su
Xiaodi
X
Institute of Materials Research and Engineering, Singapore 117602, Singapore. zd-su@imre.a-star.edu.sg
Teh
Huey Fang
HF
Aung
Khin Moh Moh
KM
Zong
Yun
Y
Gao
Zhiqiang
Z
D000814:Aniline Compounds / Q000737:chemistry*; D004247:DNA / Q000032:analysis* / Q000235:genetics; D017403:In Situ Hybridization / Q000295:instrumentation* / Q000379:methods; D008832:Microchemistry / Q000295:instrumentation*; D020411:Oligonucleotide Array Sequence Analysis / Q000295:instrumentation*; D020135:Peptide Nucleic Acids / Q000032:analysis* / Q000235:genetics*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
D000814:Aniline Compounds; D020135:Peptide Nucleic Acids; C416807:polyaniline; D004247:DNA