Tadashi Kokubo & Hiroaki
Takadama talk with ScienceWatch.com and answer a few
questions about this month's Emerging Research Front Paper in
the field of Materials Science. The authors have also sent
along images of their work.
Article: How useful is SBF in predicting in vivo bone
bioactivity?
Authors: Kokubo, T;Takadama, H
Journal: BIOMATERIALS, 27 (15): 2907-2915, MAY 2006
Pictured top to bottom: Tadashi
Kokubo & Hiroaki Takadama
Why do you think your paper is highly
cited?
This paper describes how useful a simulated body fluid (SBF) is in
predicting the bone-bonding ability of a material. The principal property
required for bone substitutes is a bone-bonding ability.
Most of the scientists working in the field of biomaterials for bone
substitutes are interested primarily in the bone-bonding ability of the
material of their research subject. This paper provides a simple and
convenient method for evaluating the bone-bonding ability of a material.
Some researchers evaluate the bone-bonding ability of their material by
using SBF and cite this paper.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
This paper describes a new methodology for evaluating the bone-bonding
ability of a material. The bone-bonding ability of a material has been
exclusively examined by means of animal experiments. However, animal
experiments require special facilities, special technicians, and the
ongoing care and sacrifice of animals.
Transmission electron
micrograph of interface
between...
Scanning electron
micrograph of apatite
formed on silica
gel...
Transmission electron
micrograph of cross
section of apatite
layer...
In contrast to this, the method described in our paper provides a simple
and convenient method for evaluating the bone-bonding ability of a material
in a short period of time through the use of SBF, without the need to
perform animal experiments.
Would you summarize the significance of your paper
in layman’s terms?
1. The number of animals sacrificed can be considerably reduced by using
this method.
2. The bone-bonding ability of various kinds of materials with different
compositions and structures can be easily evaluated in a short period of
time through the use of this method. As a result, the relationship of the
bone-bonding ability of a material with its composition and structure is
revealed and the general principle governing the bone-bonding property of a
material is understood.
3. Based on this principle, a new kind of a bone-bonding material can be
developed. For example, bone-bonding Ti metal and its alloys were developed
through the use of this principle, and have been clinically used as
artificial hip replacement joints in Japan since 2007.
How did you become involved in this research and
were any particular problems encountered along the way?
Tadashi Kokubo: When I started my research on developing a new kind of
bone-bonding material with high mechanical strength, no guiding principle
for obtaining bone-bonding material had previously been known.
Each material was implanted into bone defects in animals such as rabbits,
and their bone-bonding abilities were mechanically tested several weeks
later. A period of at least 16 weeks and the sacrifice of numerous animals
were required for evaluating the bone-bonding ability of one material. It
was difficult to derive a general principle governing the bone-bonding
ability of a material from data gathered using only a few animal
experiments.
During a study of the bone-bonding mechanism of a glass-ceramic which we
synthesized, we found that it had bonded to living bone through an apatite
layer which was formed on its surface in the living body, and that this
apatite layer can be reproduced on its surface even in an acellular
simulated body fluid (SBF) with ion concentrations nearly equal to those of
human blood plasma.
Based on these findings, it was assumed that a material able to form
apatite on its surface in SBF forms the apatite on its surface in the
living body and bonds to living bone through the apatite layer.
It was confirmed for various kinds of different bone-bonding materials that
this assumption is valid. Then, it was proposed that the bone-bonding
ability of a material can be evaluated by examining apatite formation on
its surface in SBF.
However, there were only a few kinds of resorbable materials which bond to
living bone, without apparent apatite formation on their surfaces.
Therefore, the bone-bonding ability of a material must be finally examined
by the use of animal experiments.
Where do you see your research leading in the
future?
1. On the basis of our guiding principle for obtaining bone-bonding
material, various kinds of novel bone-bonding materials with different
functions could be developed.
2. The reason why material which forms apatite on its surface in the living
body bonds to living bone could be revealed on a molecular level.
3. The reason why there are only a few kinds of exceptional materials also
could be revealed on a molecular level.
Do you foresee any social or political
implications for your research?
1. Our research contributes to a reduction of animal sacrifice needed for
evaluating the bone-bonding ability of a material.
2. Our research contributes to a reduction of time and cost needed for
evaluating the bone-bonding ability of a material.
3. Our research contributes to the development of new kinds of novel bone
substitutes.
Dr. Tadashi Kokubo
Professor
Department of Biomedical Sciences
College of Life and Health Sciences
Chubu University
Kasugai, Japan
Dr. Hiroaki Takadama
Associate Professor
Department of Biomedical Sciences
College of Life and Health Sciences
Chubu University
Kasugai, Japan