Researchers have successfully regenerated damaged skulls in mice by creating a free-standing biomimetic scaffold that combines a piezoelectric framework with the growth-promoting properties of a natural mineral. This new type of "bone bandage" has broad application prospects in bone regeneration and regenerative medicine.
Piezoelectric materials generate electrical charges when mechanical stress is applied. Bone is a piezoelectric material. Since bone has an electrical microenvironment, electrical signals play an important role in the bone repair process and can effectively promote bone regeneration. However, bone regeneration is a complex process that relies on mechanical, electrical, and biological components.
Current bone regeneration strategies, such as growth factor-releasing grafts or scaffolds, have their limitations, such as donor site complications, limited availability, and high cost. Now, researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed a groundbreaking method of bone regeneration that combines piezoelectricity with a mineral found naturally in bones.
Hydroxyapatite (HAp) is a mineral found in bones and teeth that plays a role in bone structure strength and regeneration. It is often added to toothpaste to remineralize tooth enamel and strengthen teeth. Studies have found that HAp can promote osteogenesis (bone formation) and provide a scaffold for new bone growth. It also has piezoelectric properties and a rough surface, making it an ideal material for making bone growth scaffolds.
Therefore, the researchers fabricated a free-standing biomimetic scaffold integrating HAp into a piezoelectric framework of a polymer film, polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)). This independent stent generates an electrical signal when pressure is applied, making this approach different from previous studies combining HAp and P(VDF-TrFE), which were limited to coatings on metal prostheses. The researchers' new approach provides a versatile platform for bone regeneration that goes beyond surface-bound applications, they say.
An in vitro comparison of scaffolds with and without HAp found that cell attachment rates on HAp scaffolds were 10% to 15% higher. After five days of cell culture, the cell proliferation rate on the HAp scaffold increased by 20% to 30%, and the osteogenesis level increased by approximately 30% to 40%. The findings show that HAp maximizes the piezoelectric properties of the scaffold and creates an environment similar to the human extracellular matrix, the noncellular component of all tissues that provides the basic physical structure and important cues needed for tissue regeneration.
The researchers then tested their HAp/P(VDF-TrFE) scaffold in mice, placing it over defects in the animals' skulls (lower leg bones). The stent lasted six weeks without deformation. All mice survived; no adverse effects, including infections or inflammatory reactions, were observed. Two, four, and six weeks after implantation, the bone regeneration capacity of mice equipped with HAp scaffolds was significantly enhanced compared with the control group without bone formation.
Seungbum Hong, one of the corresponding authors of the study, said: "We have developed a HAp-based piezoelectric composite material that can accelerate bone regeneration like a 'bone bandage'. This research not only proposes a new direction for the design of biomaterials, but is also of great significance in exploring the effects of piezoelectricity and surface properties on bone regeneration."
The research was published in the journal ACS Applied Materials and Interfaces.