Tra Vinikoor

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.

Osteoarthritis affects millions of people worldwide but current treatments using analgesics or anti-inflammatory drugs only alleviate symptoms of this disease. Here, we present an injectable, biodegradable piezoelectric hydrogel, made of short electrospun poly-L-lactic acid nanofibers embedded inside a collagen matrix, which can be injected into the joints and self-produce localized electrical cues under ultrasound activation to drive cartilage healing. In vitro, data shows that the piezoelectric hydrogel with ultrasound can enhance cell migration and induce stem cells to secrete TGF-β1, which promotes chondrogenesis. In vivo, the rabbits with osteochondral critical-size defects receiving the ultrasound-activated piezoelectric hydrogel show increased subchondral bone formation, improved hyaline-cartilage structure, and good mechanical properties, close to healthy native cartilage. This piezoelectric hydrogel is not only useful for cartilage healing but also potentially applicable to other tissue regeneration, offering a significant impact on the field of regenerative tissue engineering.

Amino acid crystals are an attractive piezoelectric material as they have an ultrahigh piezoelectric coefficient and have an appealing safety profile for medical implant applications. Unfortunately, solvent-cast films made from glycine crystals are brittle, quickly dissolve in body fluid, and lack crystal orientation control, reducing the overall piezoelectric effect. Here, we present a material processing strategy to create biodegradable, flexible, and piezoelectric nanofibers of glycine crystals embedded inside polycaprolactone (PCL). The glycine-PCL nanofiber film exhibits stable piezoelectric performance with a high ultrasound output of 334 kPa [under 0.15 voltage root-mean-square (Vrms)], which outperforms the state-of-the-art biodegradable transducers. We use this material to fabricate a biodegradable ultrasound transducer for facilitating the delivery of chemotherapeutic drug to the brain. The device remarkably enhances the animal survival time (twofold) in mice-bearing orthotopic glioblastoma models. The piezoelectric glycine-PCL presented here could offer an excellent platform not only for glioblastoma therapy but also for developing medical implantation fields.

A biodegradable piezoelectric scaffold excited by exercise promotes chondrogenesis and cartilage regeneration in rabbit osteochondral defects.