Multiphoton fluorescence lifetime imaging of Karpas 299 cells using ACT1 antibody conjugated gold nanoparticles

Due to the unique optical properties, gold nanoparticles (NPs) can play a useful role in biological cellular imaging as biological probes. Using multiphoton microscopy and fluorescence lifetime imaging (FLIM) system, we recorded the images of Karpas 299 cells incubated without, or with gold NPs, and ACT1 antibodies conjugated with gold NPs. From the FLIM, we can easily discriminate the difference among different experiment conditions due to the distinct lifetime between cells and gold NPs. Our results present that nonconjugated gold NPs are accumulated inside cells, but conjugated gold NPs bind homogeneously and specifically to the surface of cancer cells. For single Karpas 299 cells, the signal is very week when the excitation power is about 10mw; while the power is approximately 28 mw, a very sharp cell imaging can be obtained. For the Karpas 299 incubated with ACT1 conjugated gold NPs, while the excitation power is 10mw, gold NPs have clear fluorescence signal so that the profile of cells can be detected; Signal of gold NPs is very strong when the power arrived in 20mw. These results suggest that the multiphoton lifetime imaging of antibody conjugated gold NPs can support a useful method in diagnosis of cancer.