Intrinsic NA Detection Using Hybridization

One of the most unambiguous molecular recognition events is the hybridization of a NA to its complementary target. The SERS biosensors for DNA hybridization with 

On the other hand, intrinsic (label-free) SERS detection of DNA hybridization is obstructed by poor spectral reproducibility plus the fact that the spectral signatures of hybridized and unhybridized sequences are highly similar. To overcome these issues, two approaches were applied. First, the idea was to remove adenine from the captured strand by replacing it with isomer (2-aminopurine— 2-AP) which had different spectrum but preserved the same hybridization efficiency (Baihoumi and Halas 2010). This concept is depicted in Fig. 5.4. Spectrum a shows the SERS spectmm of thermally pretreated DNA on Au nanoshells dominated by the adenine peak at 736 cm . Spectrum b represents the SERS spectmm of DNA having 2-AP substitution attached to the Au nanoshells through a thiol moiety on its 5 -end. In this spectmm, a peak at 807 cm of the 2-AP instead of an adenine peak at 736 cm was observed. The 736 cm peak was a marker for hybridization between the native/unlabelled DNA target strand (left in the inset with A—adenine) and the 

T thymine (adapted with permission from Barhoumi and Halas 2010. Copyright 2010 American Chemical Society) 

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