During the last decade several articles have shown that two-photon scattering properties can be enhanced (106 to 109) in magnitude by using metal nanoparticle-surfaces, which is comparable to the very large enhancement of surface-enhanced Raman scattering.22–26,28,37 Here we show that an anti-PSMA aptamer based TPS ruler can be used for ultrasensitive detection of PSMA (+) LNCaP prostate cancer cells. This evidence concerns the gene FOLH1 and prostate cancer.