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

Abstract

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.