Abstract
Gold nanorods (GNRs) are generally considered to be nontoxic to normal and cancer cells. They are usually accumulated at lysosomes after entering into cells, forming GNR clusters in which strong plasmonic coupling between GNRs is expected. We investigated the photothermal therapy of single cancer cells by exploiting the significantly enhanced two-photon-induced absorption of GNR clusters naturally created in the lysosomes of cancer cells. It was revealed numerically that the plasmonic coupling between GNRs in GNR clusters can effectively enhance the photothermal conversion efficiency. As a result, the thermal damage of single cancer cells can be induced by using pulse energy as low as ~70 pJ. In experiments, the locations of GNR clusters can be accurately determined through the detection of the two-photon-induced luminescence, which is also significantly enhanced, by using a confocal laser scanning microscope. The photothermal therapy was conducted by focusing femtosecond laser light on the targeted GNR clusters, generating bubbles and deforming cell membranes. The photothermal therapy proposed in this work can lead to the rapid and acute injury of single cancer cells. The dependence of the apoptosis time on the pulse energy of femtosecond laser light was also examined. Our findings suggest a novel strategy for the photothermal therapy of single cancer cells with ultralow energy.
Highlights
In recent years, rapid development in the synthesis and characterization of nanomaterials has stimulated the use of various nanomaterials as cancer nanomedicines [1], including novel twodimensional materials that have received intensive studies [2,3]
The mean separation between Gold nanorods (GNRs) becomes comparable to the length of GNRs, which is typical for the GNR clusters observed in the lysosomes of cells, as will be shown later
3.5 Photothermal therapy mediated by GNR clusters Different from the previous studies on GNR-based photothermal therapy, we investigated the photothermal therapy of single cells by exploiting the enhanced two-photon-induced absorption (TPA)/two-photon-induced luminescence (TPL) in GNR clusters
Summary
Rapid development in the synthesis and characterization of nanomaterials has stimulated the use of various nanomaterials as cancer nanomedicines [1], including novel twodimensional materials that have received intensive studies [2,3]. The cytotoxicity of GNRs has been extensively studied and GNRs with different aspect ratios are generally nontoxic to normal cells [33,34,35,36] This characteristic makes them a suitable nanomaterial for photothermal therapy. The existence of strong plasmonic coupling would change dramatically the linear and nonlinear absorption of GNR clusters, significantly enhancing the two-photon-induced absorption (TPA) and two-photon-induced luminescence (TPL) of GNR clusters [39] Such naturally-formed GNR clusters can be employed to realize the photothermal therapy of single cells with ultralow energy. It was found that the TPA and TPL of the GNR clusters are significantly enhanced, which in turn reduces the pulse energy used in the photothermal therapy of single cancer cells. The dependence of the apoptosis time on the irradiation time and energy was examined
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