Advanced Science | Real-Time Functional Assay of Volumetric Muscle Loss Injured Mouse Masseter Muscl

Skeletal muscle has a remarkable regeneration capacity to recover its structure and function after injury, except for the traumatic loss of critical muscle volume, called volumetric muscle loss (VML). Although many extremity VML models have been conducted, craniofacial VML has not been well-studied due to unavailable in vivo assay tools. Here, this paper reports a wireless, noninvasive nanomembrane system that integrates skin-wearable printed sensors and electronics for real-time, continuous monitoring of VML on craniofacial muscles. The craniofacial VML model, using biopsy punch-induced masseter muscle injury, shows impaired muscle regeneration. To measure the electrophysiology of small and round masseter muscles of active mice during mastication, a wearable nanomembrane system with stretchable graphene sensors that can be laminated to the skin over target muscles is utilized. The noninvasive system provides highly sensitive electromyogram detection on masseter muscles with or without VML injury. Furthermore, it is demonstrated that the wireless sensor can monitor the recovery after transplantation surgery for craniofacial VML. Overall, the presented study shows the enormous potential of the masseter muscle VML injury model and wearable assay tool for the mechanism study and the therapeutic development of craniofacial VML.

Figure 1.Overview of real-time functional assay of craniofacial VML in mouse using wireless nanomembrane electronics. A) Schematic illustration of awireless electronic system on the skin of a mouse for a functional quantification of craniofacial VML of the masseter muscle. The mouse’s EMG of thecheek area is continuously monitored on the mobile device. Inset shows the process of punch-induced VML of masseter and transplantation to treatVML of the masseter. Masseter muscle was injured by biopsy punching as a model of craniofacial VML. VML-injured masseter muscles are transplantedwith a biopsied piece of tibialis anterior (TA) or masseter muscles to fill the injured area. B) Schematic illustration of a multilayered structure of asoftcircuit (left) and stretchable sensor (right). C) Muscle biopsy to create VML in masseter muscles. The middle of the masseter muscles is biopsied by a3 mm biopsy punch. Arrow indicates a muscle piece from a biopsy. D) Optical image of an active mouse with the device during mastication. E) Flowchart capturing the quantitative metrics of analyzing muscle fun