The aim of this project
is to make new advances in the field of interfacial interaction between
nanomaterials and cells. Although many studies have been performed,
there is a striking lack of quantitative analyses. A central theme here
is to use gene expression analysis. Comprehensive analysis of gene expression
(for approximately 20,000 genes) in cells on nanomaterials will be of
tremendous benefit for the design of bionanointerfaces. The up- and
down-regulated genomic information is closely related to the transduction
of signals to cell nuclei and subsequent protein production. The control
of gene expression by well-defined nanointerfaces is the key bionanotechnology
needed to develop next-generation biomaterials, and the systematic investigation
of this control will produce new academic advancements and industrial
innovations.
We promote bionanotechnological projects in three fields: materials
science, surface science, and cell biology. Special attention is paid
to bone tissue regeneration processes. Bone tissue consists mainly of
hydroxyapatite and collagen, has a hierarchical self-assembled structure,
and contains a lot of cytokines and proteins.
The initial event occurred after implanting biomaterials in vivo is
the adsorption of proteins and glycoproteins on their surfaces. Then
the cells attach, migrate, and differentiate on the protein-adsorbed
surfaces. In this project we fabricate nanomaterials with specified
surface structures, analyze the complex protein adsorptions on nanomaterials,
and systematically collect comprehensive information about gene expression
in osteoclasts (cell dissolving bone) and osteoblasts (cells building
bone tissue). We optimize the nanosurface structure that can activate
the function of bone metabolism as follows.
First, nanotopographical/nanopatterned surfaces on calcium phosphates
and titanium, materials used in orthopedic and dental implants, are
fabricated by colloidal lithography and the dewetting or adsorbing processes
of proteins. The nanosurface thus produced is analyzed by atomic force
microscopy (AFM), scanning electron microscopy (SEM), X-ray photoemission
spectroscopy (XPS), contact angle measurements, and zeta potential measurements.
Second, the complex protein adsorption phenomena on the nanosized hydroxyapatites
are analyzed by using quart-crystal microbalance with dissipation monitoring
(QCM-D). We have developed a hydroxyapatite sensor and elucidated the
single-phase protein adsorption kinetics on it. Interfacial interaction
between hydroxyapatite and cells is analyzed by measuring changes of
viscoelastic properties using QCM-D sensors.
Third, the time-oriented comprehensive gene expression of isolated as
well as co-cultured osteoclasts and osteoblasts on nanomaterials with
modified nanostructures and protein adsorption properties is analyzed.
We have amassed a quantitative library of gene expression and established
reliable methods for rapidly evaluating the safety of biomaterials without
having to do animal experiments.