Effect of pH on the Interaction of Gold Nanoparticles with DNA and Application in the Detection of Human p53 Gene Mutation

Abstract

Gold nanoparticles (GNPs) are widely used to detect DNA. We studied the effect of pH on the assembly/disassembly of single-stranded DNA functionalized GNPs. Based on the different binding affinities of DNA to GNPs, we present a simple and fast way that uses HCl to drive the assembly of GNPs for detection of DNA sequences with single nucleotide differences. The assembly is reversible and can be switched by changing the solution pH. No covalent modification of DNA or GNP surface is needed. Oligonucleotide derived from human p53 gene with one-base substitution can be distinguished by a color change of the GNPs solution or a significant difference of the maximum absorption wavelength (lambda(max)), compared with wildtype sequences. This method enables detection of 10 picomole quantities of target DNA.

Figure 1

Zeta potentials (a) and λ_max(b) of GNPs and ssDNA–GNPs at different solution pH values. ssDNA: 273G–T

Figure 2

UV–vis spectra of GNPs solutions mixed with wildtype (wd) and mutant (mt) ssDNA upon addition of HCl (pH 1.0). ssDNA: 248C–T

Figure 3

Comparison of λ_maxof ssDNA–GNPs upon addition of HCl. The sequence numbers are indicated in Table 1. Each experiment was repeated at least five times.P < 0.05, Student’st-test for paired data

Figure 4

Reversible color change of GNPs solution. ssDNA: 273G–T

Figure 5

The absorption maximum for the ssDNA–GNPs conjugates as the solution pH is cycled between 7.0 and 1.0 by adding 1 M NaOH or 1 M HCl. ssDNA: 273G–T

Figure 6

TEM image ofaGNPs + HCl (pH 1.0),bssDNA–GNPs + HCl (pH 1.0). ssDNA: 273G–T. Scale bar: 100 nm