Light-mediated cancer therapies

Photothermal therapy (PTT) and photodynamic therapy (PDT) are innovative cancer treatments that harness the power of light to selectively target and destroy cancer cells, offering non-invasive alternatives to conventional therapies.

Photodynamic Therapy (PDT)

PDT involves the use of a photosensitizer (PS), a light-sensitive molecule, which is activated by specific wavelengths of light. Upon activation, the PS interacts with oxygen molecules in the surrounding tissue, producing reactive oxygen species (ROS). These ROS cause oxidative stress that damages cellular components, ultimately leading to the death of cancer cells. PDT can also disrupt tumor blood vessels, reducing the tumor’s blood supply and helping to shrink or destroy the tumor.

Photothermal Therapy (PTT)

In PTT, photothermal agents (often nanoparticles) are delivered to the tumor site and, upon irradiation with near-infrared (NIR) light, convert the light into heat. This heat raises the temperature of the tumor tissue, damaging or killing cancer cells. Tumor cells are particularly vulnerable to heat due to their irregular blood flow and oxygen supply. The key advantage of PTT is its precision, as the heat is generated only in areas exposed to the light.

Role of Nanoparticles in PTT and PDT

Nanoparticles (NPs) play a crucial role in enhancing the effectiveness and precision of both PTT and PDT. Here’s how:

  • Improved Tumor Targeting: Nanoparticles can passively accumulate in tumors due to the enhanced permeability and retention (EPR) effect, where the leaky vasculature of tumors allows NPs to penetrate and stay in the tumor tissue more easily. Additionally, surface-functionalized NPs can be designed to actively target cancer cells, minimizing damage to healthy cells.

  • Enhanced Absorption and Delivery: In PDT, nanoparticles can encapsulate or bind photosensitizers, increasing their local concentration in tumors, improving their solubility, and protecting them from degradation. For PTT, metal nanoparticles (such as gold or silver) are highly efficient at absorbing NIR light and converting it into heat, making the process more effective at lower light intensities.

  • Combination Therapies: NPs can combine both PTT and PDT, creating a dual treatment approach. Plasmonic nanoparticles, such as gold, are ideal for this because they can both generate heat (for PTT) and enhance ROS production (for PDT) when exposed to light. This combination improves overall treatment efficacy and can be tailored for different types of cancer.

  • Spatiotemporal Control: Nanoparticles allow for precise control over the timing and location of therapy. Light can be applied directly to the tumor site, ensuring that PTT or PDT occurs only where it’s needed, reducing off-target effects and minimizing damage to healthy tissue.