Tumor ablation via photothermal effect (PTT)

Tumor ablation via photothermal effect, commonly known as photothermal therapy (PTT), is a minimally invasive cancer treatment modality that utilizes near-infrared (NIR) light-absorbing agents to generate localized hyperthermia for selective destruction of tumor cells. This approach is characterized by high specificity, minimal invasiveness, and precise spatial-temporal selectivity. The mechanism relies on photothermal agents (typically nanomaterials) that absorb NIR light and convert photon energy into heat through internal conversion and nonradiative relaxation processes. The generated heat induces various cellular responses depending on temperature, ranging from increased vascular permeability and protein denaturation at moderate temperatures to complete coagulative necrosis at high temperatures. PTT offers several advantages over conventional therapies including targeted tumor destruction with minimal damage to surrounding healthy tissue, non-invasive delivery, and the ability to trigger immunogenic cell death and antitumor immune responses. It has been successfully applied in treating various cancers including skin, colon, prostate, and breast cancer, and can be combined with other therapeutic modalities such as chemotherapy and immunotherapy to enhance overall treatment efficacy. Current research focuses on developing advanced nanomaterial-based photothermal agents with improved photothermal conversion efficiency, better tumor targeting capabilities, and strategies to overcome challenges such as heat resistance, limited tissue penetration, and heat shock protein upregulation.

Other names

Photothermal therapyPhotothermal ablationPTTNanophotothermal therapyNear-infrared photothermal therapyNIR-mediated photothermal therapy

Photothermal therapy works through internal conversion where photothermal agents absorb near-infrared (NIR) light energy and convert it into heat through nonradiative vibrational relaxation. Upon irradiation with specific wavelengths (typically NIR), electrons in the photothermal agent are excited from ground state to excited state, then undergo nonradiative relaxation through collisions with surrounding molecules, releasing kinetic energy as heat. This localized hyperthermia induces tumor cell death through multiple mechanisms depending on temperature: at 41-43°C causes protein aggregation and increased vascular permeability; at 43-45°C generates reactive oxygen species and protein denaturation; at 45-55°C causes comprehensive protein denaturation, membrane integrity loss, and programmed cell death; at 55-60°C leads to coagulative necrosis. Additionally, PTT can induce immunogenic cell death, trigger damage-associated molecular patterns (DAMPs), and enhance immune responses.