#hydroxyapatite

Detailed molecular picture of tooth enamel reveals adaptations to diet

From chewing to chomping to grinding, teeth suffer from a lifetime of repeated mechanical stress. It makes sense, then, that enamel is one of the hardest natural materials. University of Wisconsin-Madison physics professor Pupa Gilbert and colleagues previously showed that the hydroxyapatite nanocrystals that make up enamel are arranged perfectly parallel to one another, like hairs in a ponytail, but their crystal lattices are not co-oriented—a structure that contributes to the biomaterial's resistance to fracture, also known as toughness. In a new study published in the journal Nature, Gilbert and her colleagues developed a technique to quantitatively measure enamel nanocrystal orientation angles across human and non-human primate enamel from different epochs, finding a strong correlation between how tough food is and the misorientation angle.

Monocyte, Microlith, Mineral?

Every breath can be a struggle if you have the rare lung disease pulmonary alveolar microlithiasis. It’s caused by a faulty protein in the membranes of cells that line alveoli, tiny air sacs that fill your lungs. This causes mineral structures called hydroxyapatite microliths to form inside alveoli. Researchers now investigate this process by analysing RNA – a marker for gene activity – in lung tissue from human patients and a mouse model of the disease. Looking at immune cells called monocytes, which can develop into bone-degrading cells called osteoclasts, the team found that osteoclast-related genes were activated in alveolar monocytes. They also found that microliths, pictured using scanning electron microscopy at different resolutions in human (top) and mouse (bottom) lung tissue, contained osteoclast enzymes. This suggests that in response to microliths forming, osteoclast-like cells kickstart into action. This may present a new research avenue for pulmonary alveolar microlithiasis therapies.

Written by Lux Fatimathas

Image adapted from work by Yasuaki Uehara and colleagues

Department of Internal Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, March 2023

Engineered nanoparticles show enhanced intrinsic luminescence for biomedical imaging and cancer treatment

The Nanomedicine and Nanotoxicology Group (GNano) at the University of São Paulo's São Carlos Institute of Physics (IFSC-USP) in Brazil has discovered a way to transform hydroxyapatite, a bioceramic material, into a nanoparticle with enhanced intrinsic luminescence. This paves the way for the use of biocompatible, low-cost nanomaterials in biomedical imaging techniques. "We've demonstrated that the incorporation of carbonate groups into the hydroxyapatite structure increases the concentration of crystal defects, which are responsible for enhancing the intrinsic luminescence of the material. After functionalization with citrate, which improves colloidal stability in aqueous media, these calcium phosphate nanoparticles can be used as luminescent agents for cellular bioimaging," Thales Rafael Machado, first author of both studies, explained to Agência FAPESP.

A modified glue gun squirts a material to help heal broken bones

The handheld device applied antibiotic grafts onto fractured bones in rabbits

A repurposed glue gun has helped repair broken bones in rabbits. Instead of a regular glue stick, it melts a material that helps bones heal. Some breaks in bones need a little help to mend. So surgeons sometimes take a bit of bone from elsewhere in the body to make a patch called a graft. Or they can use a synthetic — human-made — material that mimics bone. Synthetic grafts are often 3-D printed. Usually, X-ray scans and measurements of injuries are needed to make sure the graft will fit just right. Designing and making the graft takes time and can delay repairs. But the glue gun method doesn’t require images of the fracture. And it doesn’t need any special graft design. The handheld device can simply squirt the graft material right onto a break.

Surface-modified apatite nanoparticles use pH control to improve biocompatibility of implants

Medical implants have transformed health care, offering innovative solutions with advanced materials and technologies. However, many biomedical devices face challenges like insufficient cell adhesion, leading to inflammatory responses after their implantation in the body. Apatite coatings, particularly hydroxyapatite (HA)—a naturally occurring form of apatite found in bones, have been shown to promote better integration with surrounding tissues. However, the biocompatibility of artificially synthesized apatite nanoparticles often falls short of expectations, primarily due to the nanoparticles' limited ability to bind effectively with biological tissues. To overcome this challenge, researchers at Nagaoka University of Technology, Japan have developed a method for synthesizing surface-modified apatite nanoparticles that results in improved cell adhesion, offering new possibilities for the next generation of biocompatible medical implants.

Scientists fabricate composites that combine high strength and bioactivity inspired by the cortical bone

Researchers have created scaffolds with enhanced strength by fabricating 20 vol% polydopamine-modified nano hydroxyapatite (pDA-nHA), featuring a distinctive lamellar structure. These scaffolds were then immersed in a polyetherketoneketone (PEKK) synthesis system for reinforcement, offering an innovative approach to both augment the mechanical robustness of the material and enhance the bioactivity of PEKK. Nano hydroxyapatite (nHA), the primary inorganic component of bone widely utilized in bone tissue engineering, suffers from poor mechanical properties when used alone. Conversely, polyetherketoneketone (PEKK), a high-performance polymer approved by the US Food and Drug Administration (FDA) and used in dentistry and biomaterial science, struggles with bioinertia, affecting its osteogenesis applications. In a study published in the journal Supramolecular Materials, researchers from Sichuan University, China, introduced pDA-nHA/PEKK composites that combine high strength and bioactivity.

At Last: New Synthetic Tooth Enamel Is Harder and Stronger Than the Real Thing

Delivering what has been so challenging to produce, researchers present an engineered analog of tooth enamel – an ideal model for designing biomimetic materials – designed to closely mimic the composition and structure of biological teeth’s hard mineralized outer layer. It demonstrates exceptional mechanical properties, they say.

Natural tooth enamel – the thin outer layer of our teeth – is the hardest biological material in the human body. It is renowned for its high stiffness, hardness, viscoelasticity, strength, and toughness and exhibits exceptional damage resistance, despite being only several millimeters thick.

Tooth enamel’s unusual combination of properties is a product of its hierarchical architecture – a complex structure made up of mostly hydroxyapatite nanowires interconnected by an amorphous intergranular phase (AIP) consisting of magnesium-substituted amorphous calcium phosphate. However, accurately replicating this type of hierarchical organization in a scalable abiotic composite has remained a challenge.