Researchers from Texas A&M University Biomedical Engineering and the Sao Carlos Institute of Physics at University of São Paulo announced on July 20 that dissolving microneedles could improve both drug and light delivery in photodynamic therapy (PDT) for skin cancer. PDT is a treatment that uses a light-sensitive drug and specific wavelengths of light to destroy cancer cells, but its effectiveness is limited by the challenge of delivering both the drug and sufficient light deep into tissue.
The team published their findings in the Journal of Biomedical Optics. They reported that arrays of pyramid-shaped, biodegradable microneedles not only help drugs penetrate more deeply into skin tumors but also spread incoming laser light more evenly within tissue. Previous studies by this group showed that aminolevulinic acid (ALA)-loaded microneedles resulted in more uniform production of the active compound responsible for killing cancer cells compared to traditional creams.
In this new study, researchers illuminated hundreds of these tiny structures with a green laser and analyzed how they redirected light through internal reflections and scattering. The experiments revealed that instead of allowing light to travel straight through, the microneedles distributed it in multiple directions. Light emerging from their tips maintained similar intensity across various angles, suggesting a nearly uniform pattern ideal for biological tissues where surface illumination can leave some regions underexposed.
The team also developed a mathematical model indicating that thousands of such tips could reduce rapid loss of light intensity typically seen with standard directed illumination methods. This broader scattering pattern may allow more treatment light to reach areas otherwise difficult to illuminate using conventional approaches. The researchers said this could be significant because successful PDT depends on even activation of the photosensitive drug throughout lesions; uneven exposure risks leaving some cancer cells untreated.
Potential applications include using one set of microneedle arrays for drug delivery followed by another designed specifically for improved light distribution or developing a single system capable of performing both functions simultaneously. However, they cautioned that their optical measurements were conducted in simplified laboratory setups rather than living tissue models, and additional research will be required to confirm whether these effects translate into better outcomes during actual treatments.
