Hydrogel-coated optical fiber derived from controllable hydrolysis chemistry for phototherapy in deep tissue

Conventional medical optical fibers, typically composed of SiO₂, are inherently rigid and may damage healthy tissues during in vivo photomedical therapies. In contrast, hydrogel optical fibers offer improved biocompatibility and flexibility, rendering them more suitable for in vivo phototherapy. However, the current hydrogel optical fibers suffer from the problems of low relative refractive index contrast (Δn), suboptimal light transmission efficiency, susceptibility to swelling, and complex fabrication processes. Herein, to address these limitations, this research develops an in-situ hydrolysis-based hydrogel optical fiber (ISHOF) using a silicone-crosslinked poly(2-hydroxyethyl acrylate) (PDMHEA) matrix. The ISHOF possesses a tissue-matched modulus (17 kPa), high relative refractive index contrast (Δn = 0.131), low light attenuation (0.19 dB/cm), swelling stability (3.2%), robust mechanical strength (380 MPa), and rapid fabrication (2 min). Furthermore, its long-term in vivo applicability is validated through a sustained postoperative photodynamic therapy (PDT) experiment. These results establish ISHOF as a promising platform for next-generation hydrogel optical fibers, enabling sustained in vivo phototherapy and advancing the engineering of high-performance therapeutic biomaterials. STATEMENT OF SIGNIFICANCE: Hydrogels optical fibers are promising medium for in vivo phototherapy due to their excellent biocompatibility. However, conveniently achieving hydrogels optical fibers with comprehensive properties remains a significant challenge. Here, we propose a strategy to build core-sheath hydrogel optical fiber by in situ hydrolysis, utilizing high refractive index silicone-crosslinked polymer to grow low refractive index hydrogel cladding on its surface under acid treatment. The fiber shows unified properties of rapid fabrication, high relative refractive index contrast, swelling resistance, tissue-matched modulus, and low light attenuation. The proposed concept and strategy may inspire the design of high-performance material for sustainable in vivo application.