Journal
ACS APPLIED BIO MATERIALS
Volume 3, Issue 10, Pages 7003-7010Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsabm.0c00873
Keywords
structural flexibility; rigid loop; DNAzyme; ssDNA region; gold nanoparticles; plasmonic detection
Funding
- Shandong Provincial Natural Science Foundation [ZR2019QC011]
- Shandong Provincial Soft Science Research Program [2019RKE29001]
- Fundamental Research Funds for the Central Universities
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Strains in biomolecules greatly restrict their structural flexibility. The effects of DNA's structural flexibility on nanoparticle stability have remained less explored in the field of plasmonic biosensors. In the present study, we discover the opposite effects of a rigid loop and a flexible single-stranded DNA (ssDNA) region in DNAzyme on the colloidal stability of gold nanoparticles (AuNPs), which afford turn-on plasmonic detection of Pb2+. In specific, DNAzyme-functionalized AuNPs undergo spontaneous assembly at high ionic strength upon hybridization to their substrate sequence because of a DNA base stacking interaction. In the presence of Pb2+, however, the DNAzyme grafted on the AuNP cleaves the substrate and forms an ssDNA region in the middle of the rigid loop. The induced structural flexibility of the surface-grafted DNAzyme by the ssDNA region in the middle helps elevate interparticle entropic repulsion, thereby bringing AuNP assemblies back to dispersion. We discover that this process can afford a dramatic increase of the AuNPs' plasmon resonance for determination of Pb2+ concentration. Under optimized conditions, a detection limit of 8.0 nM can be achieved for Pb2+ by this method with high selectivity. Its applicability to Pb2+ analysis in tap water samples has also been demonstrated.
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