Fujitsu and Nagoya University Develop Technology Enabling High-Speed Detection of Toxic Proteins Using DNA Aptamers

Kawasaki and Nagoya, Japan, August 02, 2010

Fujitsu Laboratories Ltd. and Nagoya University today announced the development of technology that enables high-speed detection of toxic proteins⁽¹⁾ that cause food poisoning. A new sensor that detects the presence of toxic proteins was manufactured, by employing a combination of artificial antibodies (DNA aptamers) which capture the toxic proteins, with a signal converter which converts those "capturing events" of captured toxins into optical signals. The new sensor enables detection of toxic proteins 100 times faster than with previous methods. This new technology can be used for shipment inspections of various foods to enable faster and more accurate inspections, thus contributing to better food safety.

Development of this technology was partially funded by Special Coordination Funds for Promoting Science and Technology from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan⁽²⁾.

About Toxic Proteins

In addition to building parts of the human body, including muscles and organs, proteins play a variety of important roles in digestion, movement, immunity, and genetics. There are thought to be anywhere from tens of thousands to tens of millions of different types of proteins. Snake and scorpion venoms, botulinum toxins, and staphylococcus aureus (staphylococcal enterotoxins) are all toxic proteins that are poisonous to the human body. When toxic proteins are especially potent, they can even cause death.

About Artificial Antibodies and DNA Aptamers

Antibodies are a type of protein that are present in blood and bodily fluids, and which have the function of recognizing specific proteins. Artificial antibodies based on DNA materials have the same molecule-recognition properties as conventional antibodies - as artificial antibodies can be quickly synthesized chemically in test tubes, they hold considerable promise for application in therapeutic medicines and diagnostic reagents. Since 2001, Fujitsu Laboratories has been developing artificial antibody technologies for DNA material chemically modified to feature characteristics resembling amino acids (DNA aptamers)⁽³⁾, and have succeeded in strengthening the affinity between artificial antibodies and proteins. Compared to conventional antibodies, Fujitsu's artificial antibodies can be chemically synthesized in a short period of time as there is no need to employ a mammalian immune system to synthesize the artificial antibodies, and molecule-recognition can be easily enhanced.

Background

Food poisoning occurs when food has been contaminated by pathogenic bacteria - one effective method for dealing with such bacterial contamination is heat sterilization of the food, in order to kill the bacteria. Toxic proteins produced by such bacteria, however, can remain in the food even after heating, leading to toxin-based food poisoning. Thus, even after heat sterilization, food contaminated by heat-resistant toxic proteins can still cause food poisoning. By detecting the presence of minute quantities of such toxic proteins, food poisoning can be prevented.

Technological Challenges

Detection of toxic protein requires specific antibodies to be employed. Conventional antibodies require the employment of a mammalian immune system in order to be developed, thus being costly and not amenable to maintaining a fixed level of quality. Furthermore, conventional measuring technologies do not feature high accuracy when measuring minute quantities of toxic proteins – such conventional measuring technologies require that bacteria be cultured in order to increase the amount of toxic proteins, leading to longer time required for measurement.

Newly Developed Technology

Fujitsu Laboratories and Nagoya University (specifically, the research groups of Professor Emeritus Michio Ohta and Professor Yoshinobu Baba of Nagoya University) have co-developed a new sensor that enables high-speed detection of the presence of toxic proteins. The sensor is comprised of artificial antibodies that capture toxic proteins, combined with a signal converter that converts the "capturing events" of captured proteins into optical signals.

Features of the technologies developed for the new sensor are as follows:

1. Selection of artificial antibodies to capture toxic proteins

Using DNA - which is stable and easy to handle - and side-chains resembling amino acids to modify the DNA, artificial antibody material featuring strong affinity with proteins was developed. The artificial antibody material was then randomly connected, resulting in successful inexpensive creation of an artificial antibody library comprised of 10¹⁴ types of various multi-array artificial antibodies. From within this vast library of artificial antibodies, through collaboration, Fujitsu Laboratories and Nagoya University (Professor Emeritus Michio Ohta's research group) were able to select the artificial antibodies which feature strong affinity with toxic proteins, and also verified that the selected artificial antibodies can be applied to conventional biochemical testing methods⁽⁴⁾.

2. Signal converter that converts "capturing events" of captured proteins into optical signals

The DNA-based signal converter employs results of a collaboration between Fujitsu Laboratories and the Walter Schottky Institute at the Technische Universität München⁽⁵⁾ (specifically, Professor Dr. Gerhard Abstreiter's research group). Artificial antibodies featuring strong affinity to bond with the targeted proteins were attached to the tip of a signal converter, to which fluorescent dye was applied. When the proteins bond with these artificial antibodies, the fluorescence of the dye darkens. By observing fluctuations in the fluorescence of the dye, the presence of and amount of the targeted toxic proteins can be accurately measured.

3. Mechanism to enable the sensor to efficiently capture proteins

In order to enable artificial antibodies on the sensor to capture proteins present in sample fluid, sample fluid is led into the sensor as flow. So that the sensor captures proteins efficiently, Fujitsu Laboratories collaborated with Nagoya University (Professor Yoshinobu Baba's research group) to co-develop a technology that controls the flow of sample fluid that flows onto the sensor surface. This makes it possible for the sensor to rapidly capture approximately 90% of proteins present in the fluid.

Results

In comparison with previous measuring technologies for detecting toxic proteins, the new technologies from Fujitsu and Nagoya University make it possible to quickly detect toxic proteins 100 times faster than in the past, thus significantly shortening the time required to measure the presence of toxic proteins. By applying the technologies to facilitate faster inspection for shipment of highly perishable foods such as dairy products, it will be possible to deliver such foods with a higher level of freshness and more safely.

Future Developments

Fujitsu plans to continue developing methods to leverage the high protein-affinity and low cost accompanying these artificial-antibody (DNA aptamer) technologies, so that some of the conventional antibodies used in food and disease testing can be replaced with artificial antibodies. In May 2010, Fujitsu Laboratories and Fujitsu Asia Pte. Ltd. jointly established a new research laboratory in Singapore⁽⁶⁾, which will conduct trials aimed at commercializing artificial antibodies.