UNDERSTANDING BONE MINERAL PRECURSORS IN OSTEOBLASTIC CELLS
Dongbo Wang1, Wojtek Tutak2, Ming Tung2, Alex Fernandez-Martinez3, Adam Wallace4 , Marcus Cicerone1, Sheng Lin-Gibson1, Young Lee1
1 NIST Biosystems and Biomaterials Division, Gaithersburg, Maryland
2 American Dental Association Foundation, Gaithersburg, Maryland
3 Institut des Sciences de la Terre, Grenoble, France
4 Berkeley National Labs, Berkeley, California
Formation of mineralized tissues – bone and teeth – are ubiquitous among mammalian organisms. Bone is a primary focus of tissue engineered approaches for treatment of diseased or damaged tissue. Our primary focus is to understand the cells responsible for bone formation – osteoblasts – and quantify their biomineralization process. Evidence from in vivo and cell culture systems shows that osteoblasts concentrate ions as stabilized amorphous calcium phosphate (ACP) precursors prior to the formation of the bone mineral, apatite. This evidence points to the importance of a condensed phase for the formation of mineralized tissues, however the details remain largely unclear. We are focusing on two specific problems: 1) understanding the spatial (intra and extra cellular) and temporal distribution of ACP and apatite in osteoblastic cells; 2) understanding the composition, reactivity and structure of the intracellular ACP phase. To address the first problem we are using Broadband Coherent Anti Stokes Raman Spectroscopy (CARS) imaging. This technique allows us to spectroscopically identify osteoblast produced mineral (ACP or apatite) along with relevant organelles such as nuclei and matrix vesicles. To address the second problem, we are synthesizing ACP of different chemical compositions and comparing them to the cellular ACP with Raman spectroscopy. In order to understand the structural variation of ACP as a function of composition we will use synchrotron based scattering and Pair Distribution Function analysis.