MMC Activities..............1
Overseas Trends............5
Members’ Profiles .........6Information..................8

MMC Activities

Reports on Research Conducted under the 9thMicromachine Technology Research Grants (Part 2)
The research grant program began inviting applications in 1993 as a part of the independent activities of MMC. The purpose of theprogram is to assist college and university staff engaged in basic research on micromachines, and to promote further development of
micromachine technology and communication between academics and people in the industrial world.
Of the 9 themes selected for the 9th (2001) research grants, summaries are provided below of the research results for 2 projects carriedover from fiscal 2000 and 3 projects newly selected for fiscal 2001.
NO.

Subjects

Leader andCo-Worker

Affiliations

PeriodCarried-Over Projects Granted for Fiscal 2000

5Creation of PEGylated Gold Nanoparticles for New
Prof. Yukio Nagasaki
Diagnostic System

Professor, Department of Materials Science, Science Universityof Tokyo

2 Years

6Surface Micromachining on Three-Dimensional
Dr. Minoru Sasaki
Bulk Si Structures

Associate Professor, School of Engineering, Tohoku University

2 Years

Research Projects Newly Selected for Fiscal 2001
Basic Study for Microactuator Controled by Wetting Prof. Izumi Hirasawa
and Driven by Capillary Force between LiquidLiquid-Gas Interfaces
Dr. Masato Sakurai

Professor, Department of Applied Chemistry, Waseda University

12Study on a Cuff Microelectrode Using MEMS
Dr. Shoji Takeuchi
Technology

Associate Professor, Center for International Research on Micromechatronics(CIRMM), Institute of Industrial Science (IIS), The University of Tokyo

1 Year3

Study on Heart-Emulating Microactuators Using
Dr. Ryo Yoshida
Self-Oscillating Gel

Associate Professor, Graduate School of Engineering, The
University of Tokyo

1 Year

1 YearSenior Researcher, Space Technology Research Center, NationalAerospace Laboratory of Japan

Affiliations as of May, 2003

Creation of PEGylated Gold Nanoparticles for New Diagnostic System
Yukio Nagasaki, Professor, Department of Materials Science, Science University of Tokyo
It is known that small gold particles on the order of several to tens of nanometers
can be generated by reducing a chloroauric acid (HAuCl 3) using a reducing agent,such as citric acid. Gold nanoparticles obtained in this way disperse stably in an
aqueous solution because like particles do not aggregate due to an ion-ion repulsion
from the citric acid adsorbed on the surface of the gold nanoparticles. However,under the severe conditions of high ion concentrations or the like, the ionic repulsionof these adsorbed molecules generates an electrostatic shield that remarkably reduces
dispersion, facilitating agglutination. In order to improve stability, we performed anexperiment to add starch or other water-soluble polymers to form a protective colloid.
Murray, et al., succeeded in coordinating a very stable particle dispersion by adding
polyethylene glycol having a mercapto group (PEG-SH) to the surfaces of the gold
nanoparticles. However, this method suffers from many problems including a drop instability when investigating functionality, due to the conflicting relationship between
stabilizing nanoparticle dispersion and surface functionality.
From the conventional perspective of biomaterial surface treatment, the authors
synthesized polyethylene glycol (HeteroPEG) with a different functional group on
both ends (Scheme 1). The gold nanoparticles were stabilized using HeteroPEG
having a highly configurable mercapto group and polyamine chain on the surface ofthe gold particles (Scheme 2). Since the PEG was coordinated in a brush formationon the surface layer of the gold nanoparticles and the opposing end possessed afunctional group in which a ligand can be introduced, this compound holds promise asa tool for resolving the above problems.
We attempted to functionalize particles using sugar and lectin or biotin andavidin, which are well known for use in specific molecular recognition. Fig. 2 shows
photos of a solution of dispersed lactose-conjugated gold nanoparticles when an RCA
lectin protein was added to selectively interact with galactose therein. The dispersed
nanoparticles agglutinated by the interaction between lactose on the particle surface
and lectin, turning the solution a purple color. When free galactose is added to thisform, the solution returns to a pink color, indicating that this interaction is reversible.
Fig. 3 is a graph showing the relationship between the concentration of RCA120 lectinand changes in absorbency for two nanoparticles prepared with lactose and mannose
introduced onto the PEG terminals of the respective gold nanoparticles. While thegold nanoparticles modified with mannose, which does not show interaction with theRCA120 lectin, do not indicate any changes in absorbency, the lactose-conjugated gold
nanoparticles were confirmed to change dependent of concentration. Based on theresults of Figs. 2 and 3, this system enables the confirmation of molecular recognition
with the naked eye and an accurate assessment of concentration using a simple
spectroscope. This novel material will allow us to perform bedside diagnoses oftoday's extremely serious infectious diseases and highly sensitive diagnoses that wereimpossible before now.

Internet Home Page : http://www.mmc.or.jp/Scheme 1PEG
Gold nanoparticlesSHPEG

Ionic strengthPEGstabilization

HSThiol

PEG mixtureGold nanoparticles
Ligands

timeScheme 2Fig. 1 Dispersion stability of PEGylated goldnanoparticles

Disease factors(protein)

Dispersed

AgglutinatedFig. 2 Lactose PEGylated gold nanoparticles Fig. 3 Degree of gold nanoparticle agglutinationand lactin mixture
in relation to lactose concentration