Abstract: Oxygen-sensing materials and methods are disclosed. The materials include oxygen-sensing chromophores embedded in a solid matrix including silk fibroin in an amount by weight of at least 50% of the total weight of the solid matrix. The solid matrix possesses at least partial transparency at relevant wavelengths. The solid matrix is biocompatible and biodegradable. The solid matrix is not a hydrogel. The chromophores are distributed throughout the solid matrix. Tissue oxygenation can be estimated from phosphorescence measurements made from oxygen-sensing materials implanted in subject.