Biocompatible and Implantable Hydrogel Optical Waveguide with Lens-Microneedles for Enhancing Light Delivery in Photodynamic Therapy

The finite penetration depth of light in biological tissues is a practical constraint in light-induced therapies, such as antimicrobial light therapy, photothermal therapy, and photodynamic cancer therapy. Herein, a biocompatible and implantable device, termed hydrogel planar waveguide with lens-microneedles, for light delivery in deep tissue is demonstrated. The prototype device, integrated planar waveguide and lens-microneedles, is fabricated by press-molding polyethylene glycol diacrylate polymers. The optical beams through the lens-microneedles are focused at a specific point to realize the optimal intensity profile in the tissue. The adequate treatment depth and region for the hydrogel planar waveguide with five lens-microneedles are extended to 24 mm and 3.1 cm². The photoswitchable chemotherapeutic against colorectal cancer cells is switched by using different hydrogel waveguides. The performances of hydrogel-waveguide-enabled photoswitching are characterized by the dose responses from the optical microscope, crystal violet staining, and MTT assays. The anticancer drug activated by the hydrogel planar waveguide with five lens-microneedles is shown to be twice as effective as the other fibers and waveguides in causing cancer cell death. The proposed biodegradable waveguide can be utilized for long-term light delivery and does not require to be removed as it is gradually resorbed by the tissue. The results point to a new paradigm for widespread use in photomedicine.