Particle stability in polymer-assisted reverse colorimetric DNA assays

Weiming Zheng; Lin He
February 2009
Analytical & Bioanalytical Chemistry;Feb2009, Vol. 393 Issue 4, p1305
Academic Journal
“Reverse” colorimetric DNA detection by the formation of core-shell particles upon DNA hybridization is described. Specifically, the assay is based on a strategy to covalently link polymer reaction initiators to suspended nanoparticles upon DNA hybridization. These initiators then prompt polymer chain growth to form a thick polymer shell outside of particles, acting as the physical barrier to keep Au particles apart. Particles without DNA hybridization aggregate, accompanied by a pronounced solution color change from red to blue. The focus of this report is to address reaction kinetics of two co-occurring processes: polymer growth and particle aggregation during the reverse colorimetric DNA assay. The results show that Cu ions used as the polymerization catalyst bind strongly to the bases in DNA molecules, resulting in crosslinking of DNA-attached gold nanoparticles and their subsequent precipitation. Both Cu-ion-assisted particle aggregation and polymer growth are found to depend strongly on Cu ion concentration, salt concentration, and reaction temperature. Under the optimized conditions, faster polymer chain growth on the surface overcomes particle aggregation and preserves particle stability via steric stabilization.


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