We demonstrate the amplified detection of BRCAI gene based on the gold nanoparticle labeled DNA sensor. The sensor was based on a "sandwich" detection strategy, which involved an immobilized capture probe DNA (DNA-c), Target DNA (DNA-t) and gold nanoparticle conjugated reporter probe DNA (DNA-r.AuNP). The sensor surface was characterized by scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). Detection capability of the sensor was studied with I-V measurements using either scanning tunneling microscopy (STM) or Keithley 2400 Source Meter SMU Instrument. The DNA sensor could detect up to 1. fM DNA target (5.896. fg of BRCA 1. gene/ml) and exhibited excellent selectivity against noncomplementary sequences and three base mismatch complementary targets. Good reproducibility, high sensitivity, good stability and reusability of the developed sensor surface showed its application in early cancer diagnosis. {\textcopyright} 2014 Elsevier B.V.