Yuhui Zhu

Knee joint loading regulates cartilage regeneration and degeneration, influencing both healing and osteoarthritis (OA) progression. Although defining the optimal range of loading is essential, in vivo measurement remains challenging because current nonbiodegradable sensors require removal surgeries, and computational models provide only indirect estimates. Here, we report a fully biodegradable, implantable piezoelectric pressure sensor composed of biocompatible materials and designed with a single-ended configuration, consisting of only one electrode. This configuration maintained stable performance for more than 2 months, which, to our knowledge, is among the longest functional lifetimes reported for biodegradable pressure sensors. Ex vivo studies simulating the in vivo environment demonstrated accurate monitoring of intracranial pressure and knee movement, while in vivo implantation in a rabbit model confirmed both robust biocompatibility and reliable monitoring of joint loading during natural activities. This platform could enable feedback-guided, personalized rehabilitation regimes for OA management by identifying optimal joint loading conditions.

The healing process of critical-sized bone defects urges for a suitable biomineralization environment. However, the unsatisfying repair outcome usually results from a disturbed intricate milieu and the lack of in situ mineralization resources. In this work, we have developed a composite hydrogel that mimics the natural bone healing processes and serves as a seedbed for bone regeneration. The oxidized silk fibroin and fibrin are incorporated as rigid geogrids, and amorphous calcium phosphate (ACP) and platelet-rich plasma serve as the fertilizers and loam, respectively. Encouragingly, the seedbed hydrogel demonstrates excellent mechanical and biomineralization properties as a stable scaffold and promotes vascularized bone regeneration in vivo. Additionally, the seedbed serves a succinate-like function via the PI3K-Akt signaling pathway and subsequently orchestrates the mitochondrial calcium uptake, further converting the exogenous ACP into endogenous ACP. Additionally, the seedbed hydrogel realizes the succession of calcium resources and promotes the evolution of the biotemplate from fibrin to collagen. Therefore, our work has established a novel silk-based hydrogel that functions as an in-situ biomineralization seedbed, providing a new insight for critical-sized bone defect regeneration.