The in vivo performance of plasmonic nanobubbles as cell theranostic agents in zebrafish hosting prostate cancer xenografts

Abstract

Cell theranostics is a new approach that unites diagnosis, therapy and confirmation (guidance) of the results of therapy in one single process at cell level, thus principally improving both the rapidity and precision of treatment. The ideal theranostic agent will support all three of the above functions in vivo with cellular resolution, allowing individual assessment of disease state and the elimination of diseased cells while leaving healthy cells intact. We have developed and evaluated plasmonic nanobubbles (PNBs) as an in vivo tunable theranostic cellular agent in zebrafish hosting prostate cancer xenografts. PNBs were selectively generated around gold nanoparticles in cancer cells in the zebrafish with short single laser pulses. By varying the energy of the laser pulse, we dynamically tuned the PNB size in a theranostic sequence of two PNBs: an initial small PNB detected a cancer cell through optical scattering, followed by a second bigger PNB, which mechanically ablated this cell without damage to surrounding tissue, while its optical scattering confirmed the destruction of the cell. Thus PNBs supported the diagnosis and guided ablation of individual human cancer cells in a living organism without damage to the host.

Figure 1

PNB theranostics in vivo includes the generation and detection of the two sequential PNBs: (a) small PNB is generated (with green pump laser pulse) in zebrafish and in specific cell and detected (with red probe laser pulse) thus sensing the cell; (b) the next bigger PNB (generated with the second pulse of higher energy) destroys the cell, while optical scattering of the 2^nd PNB guides the destruction; (c) fluorescent image of the embryo shows prostate labeled cancer cells scattered through its body.

Figure 2

Experimental scheme for optical generation and detection of plasmonic nanobubbles in cells in vivo: Gold NP conjugate with a cell-specific antibodies form the clusters during their endocytosis, the NP clusters generate the PNBs upon absorption of the pump laser pulse and scatter the probe laser radiation that is detected with a side or forward photodetectors.

Figure 3

Scanning electron microscopy images of cancer cells after the incubation with gold NPs show their membrane coupling (a) and internalization (b), and the result of the exposure to a single pump laser pulse that resulted in the non-invasive PNB with the lifetime of 25±5 ns (c) and the ablative PNB with the lifetime of 300±42 ns (d). The inserts show the images of the whole cells.

Figure 4

Images of one prostate cancer cell incubated with gold NPs and DiI dye. I: before PNB, II: after the 1^st PNB, III: after the 2^nd PNB; (a–c): bright field images; (d–f): fluorescence of DiI ((d): before PNB, (e): after 1^st PNB, (f): after 2^nd PNB); (g–i): side scattering pulsed images of the cell (g), 1^st PNB (h) and 2^nd PNB (i); (j–l): corresponding time-responses obtained simultaneously with scattering images (g–i).

Figure 5

Images of the zebrafish embryo with prostate cancer cells incubated with gold NPs and DiI dye: I: before PNB, II: after the 1^st PNB, III: after the 2^nd PNB; (a–c): bright field images; (d–f): fluorescence of DiI ((d): before PNB, (e): after 1^st PNB, (f): after 2^nd PNB); (g–i): side scattering pulsed images of the cell (g), 1^st PNB (h) and 2^nd PNB (i); (j–l): corresponding time-responses obtained simultaneously with scattering images (g–i). Cancer cell shown with an arrow.