A review of the role of carbon nanotubes for cancer treatment based on photothermal and photodynamic therapy techniques

Carbon nanostructures have special optical characteristics that confer them with effective light-to-heat conversion ability. They can also increase the local temperature by activating surface plasmons (collective electron oscillations), thereby localizing the heat treatment of nanoscale carbon catalysts. Accordingly, nanotheranostic platforms combining multiple antitumour therapies under the guidance of multimodal imaging have become a research hotspot in cancer therapy because of their improved therapeutic effect and tumour specificity, decreased drug resistance, convenient and accurate tumour lesion detection and treatment monitoring, and enhanced therapeutic effect. As nanomedicine has rapidly advanced, various treatment modalities have been explored. Phototherapy has drawn particularly strong interest because of its low invasiveness, high tumour selectivity, outstanding spatial/temporal controllability, and low toxicity. The two primary types of phototherapy are photodynamic therapy (PDT) and photothermal therapy (PTT). In PDT, reactive oxygen species kill the tumour cells under light irradiation. In PTT, tumour death occurs via local hyperthermia induced by photothermal agents under light irradiation. Mutlipurpose nanoparticles owing to their surface plasmon resonance capability and porous architectures for synergistic therapy with other modalities, PDT and PTT have been combined in various ways in PTT.