No abstract

Optical fibers are widely used in biomedical applications for sensing, imaging, and therapies. Unlike existing solid-state optical fibers, soft polymer and hydrogel fibers offer physical and chemical properties well suited for functionalization with biomolecules and long-term implantation in the body. Here, hydrogel optical fibers are fabricated with glucose-sensitive moieties and the swelling-induced sensing is demonstrated. The core of the fiber is made of poly(acrylamide-co-poly(ethylene glycol) diacrylate) (p(AM-co-PEGDA)) hydrogel functionalized with phenylboronic acid. The complexation of the phenylboronic acid and cis diols of glucose molecules lowers the apparent pKa of the hydrogel network and increases the concentration of the boronate anions that enhances the Donnan osmotic pressure to swell and change the physical size of the hydrogel optical fiber. This mechanism is reversible through ester group dynamic covalent binding of the phenylboronic acid with glucose molecules. Dynamic changes in the effective RI of the hydrogel optical fiber are measured through light propagation loss. The sensor sensitivity to glucose concentration is 1.2 mmol L−1 over a physiological range of 1–12 mmol L−1. The biocompatible hydrogel optical fibers may be subcutaneously implanted for continuous monitoring of interstitial glucose concentrations.

Advances in photonics have stimulated significant progress in medicine, with many techniques now in routine clinical use. However, the finite depth of light penetration in tissue is a serious constraint to clinical utility. Here we show implantable light-delivery devices made of bio-derived or biocompatible, and biodegradable polymers. In contrast to conventional optical fibres, which must be removed from the body soon after use, the biodegradable and biocompatible waveguides may be used for long-term light delivery and need not be removed as they are gradually resorbed by the tissue. As proof of concept, we demonstrate this paradigm-shifting approach for photochemical tissue bonding (PTB). Using comb-shaped planar waveguides, we achieve a full thickness (>10 mm) wound closure of porcine skin, which represents ∼10-fold extension of the tissue area achieved with conventional PTB. The results point to a new direction in photomedicine for using light in deep tissues.