An artificial bone window for long-term photoacoustic monitoring of bone recovery

Blood vessels that deliver nutrients and oxygen over the entire body is essential for bone homeostasis. Especially, for the bone recovery, long-term in vivo vascular imaging is desirable. Here, we propose an optical and ultrasonic transparent bone window, which allows repeated, chronic monitoring of bone angiogenesis in mouse tibia defect. A metal ring with an outer diameter of 2 mm and an inner diameter of 1 mm is bonded with a silicone-based polydimethylsiloxane (PDMS) film and cover the bone surface, which can effectively eliminate the inflammation caused by repeated wound opening before imaging. We make a bone defect model in mouse tibia, and employ an optical resolution photoacoustic microscopy (ORPAM) to provide a high-resolution, label-free, long-term, in vivo observation of the bone vascularization during the bone defect healing. The results suggest that the artificial bone window can remain stable for inspection and play positive role for bone repair.