A General Strategy of Designing NIR-II Emissive Silk for In Vivo Monitoring of Implanted Stent Model Beyond 1500 nm

Silk fibroin-based materials spun by silk worm present excellent biocompatible and biodegradable properties, endowing their wide applications for in vivo implanted devices. Therefore, it is highly desirable to explore a general strategy for functionalization of silk with additional optical bioimaging function for directly in-situ monitoring the status of the implanted devices in vivo. Herein, a new type of silk material with second near-infrared (NIR-II, 1000-1700 nm) emission is explored for real-time observation of biological scaffolds model by a general route of feeding larval silkworms with lanthanide-based NaYF4: Gd3+ Yb3+ Er3+@SiO2 nanocrystals. After feeding lanthanide nanocrystals, the silk spun by silkworms holds efficient NIR-II emission beyond 1500 nm. Moreover, NIR-II bioimaging-guided biological stent model monitoring presents superior signal-to-noise (S/N) ratio than the traditional optical imaging by utilizing the first NIR (NIR-I) region. The successful generation of NIR-II emissive NaYF4-embedded silk natural materials by a in vivo feeding method may open up the possibilities of designing NIR-II optically functionalized silk materials for highly sensitive and deep-tissue monitoring the in vivo state of the implanted devices.