The role of polyphosphate in the nucleation and progression of mineralization 

Negatively-charged polymers of inorganic phosphate (polyphosphates) can be found within body fluids (such as synovial fluid and blood) as well as a variety of mammalian cells (platelets, mononuclear cells, fibroblasts and osteoblasts). The specific function of polyphosphate have not been completely elucidated, however a variety of roles have been proposed. This project focuses on the role that polyphosphates may play as an alternative phosphate source for mineralization. The unique chemical properties of polyphosphate, allow it to chelate Ca++, and thus provide a local reservoir of biologically available phosphate and calcium. This project utilizes a combination of techniques: in vitro cell culture, lentivirus infection, chemical analysis, light and electron microscopy to explore whether polyphosphates are involved in any of the stages of physiological mineralization. Such understanding may provide perspective and possible novel therapeutics for regulation of normal and pathological mineralization. 

Project in collaboration with Dr. A. Nanci (UdeM) and Dr. S. Omelon (uOttawa)

Fast Blue staining of Lentiviral-induced alkaline phosphatase expression in HEK293 cells (scale bar = 50 microns)

The effect of nanoporous titanium surfaces on macrophage activity and morphology

Upon the surgical implantation of a biomaterial, a host of inflammatory cells, including macrophages, will initially interact with its surface. It is now recognized that the function and/or phenotype of a macrophage can be dictated not only by the cytokine and cellular environment of the wound site, but also by the material itself. Depending on which phenotypic spectrum is stimulated, the macrophage can promote healing by initiating appropriate tissue repair or defend the body by either degrading the material or creating a fibrous capsule around it. Studies on biomaterial biocompatibility often focus on the response of tissue specific cells (such as osteoblasts or fibroblasts); however because macrophages are one of the first cell types to interact with the biomaterial, they have the capacity to direct downstream cellular events. Therefore, understanding the influence of a biomaterial on macrophage signaling is essential to elucidate not only the immediate host response but ultimately also the long-term performance. It is becoming well established that cellular activity and function are influenced by the surface characteristics of the biomaterial. Since cell signaling occurs at the nanoscale level, surface modifications at the scale of the cell’s sensing apparatus have a great potential to influence signaling events. This project investigates the response of macrophages to machine polished titanium compared to surface modified titanium (generated by oxidative nanopatterning). Techniques used in this study include in vitro cell culture, immunofluorescence labeling and electron microscopy. Understanding how the physiochemical surface of a material alters macrophage behavior will aid in the intelligent design of biomaterials, which can be tailored for specific applications.

Project in collaboration with Dr. A. Nanci (UdeM)


D-U937s after treatment with H2O2 and stained for reactive oxygen species using CellROXTM (green) and actin (red)

D-U937s on a titanium surface

© 2013 by Fabio Variola. All rights reserved