Our aim is to broaden the dynamic range of target DNA detection by an Au nanoparticle (AuNP) sandwich assay based on complementary DNA hybridization. We conducted electrophoresis band analysis for different sizes and concentrations of AuNPs bearing different numbers of surface-conjugated probe DNA molecules. We found that the AuNP concentration is critical to determining the maximum quantification limit (upper limit of the dynamic range). The number of immobilized probe DNAs per AuNP was also optimized to prevent errors in determining the target DNA concentration and to raise the upper limit. We examined AuNPs with diameters ranging from 15 to 40 nm at different concentrations and demonstrated tunability of the dynamic ranges spanning two to three orders of magnitude. The use of both 15 and 40 nm AuNPs can cover a dynamic range of over four orders of magnitude.
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