The interaction of 0.5 ug/mL TPT with 50 ug/mL dsDNA was also investigated in solution phase using SWCNT=PGEs. The average signals of TPT and guanine were found to be 10.2 +- 2.8 uA respectively before interaction process. There were 42% and 88% decreases at the TPT and guanine signals after interaction in the solution phase. Concerning the decrease % at the TPT signal. 5 min interaction time had a similar behavior by means of the interaction performed both at the electrode surfave and in the solution phase. However, the surface confined interaction was required a less sample solution compared to the interaction performed in solution phase.