Immediate Identification

Dr. Ester Segal and her research group at the Faculty of Biotechnology and Food Engineering have developed a new method for rapid Detection of bacterial contaminations

Dr. Ester Segal

By Noam Bercovitz

The first years of young faculty at the Technion are among the most critical ones of their careers. These are the years in which they set up their research laboratories, recruit research assistants, and begin publishing papers, which at the end of the day by virtue of their quality and quantity, determine whether these academicians get tenure. In parallel, they must also focus on raising research grants, demanding teaching responsibilities, and carry out many faculty and institutional duties.

Dr. Ester Segal, a faculty member of the Faculty of Biotechnology and Food Engineering for the past two and a half years, is in the midst of this critical period. She recently published a significant paper in the area of biological sensors or biosensors, the result of a research project she started upon her arrival to the Technion. The research paves a way for major broadening of the use of biosensors for detecting harmful bacteria contaminations. But above all, it demonstrates to Segal that she is well on her way to achieving her sought after tenure.

Silicon is also biotech

Biosensors are analytical devices used to detect materials through a mechanism of biological identification. The technology that Segal uses is based on silicon chips that are densely perforated with nanometer-sized pores. Porous Silicon  has become the focus of vast research since it was discovered that it in contrast to “conventional” Silicon, it degrade into non-toxic species in the body. Moreover, researchers found that the material is also biocompatible. These and other synthetic characteristics make it an excellent candidate material for many applications in areas such as biosensors, biomaterials and drug delivery.

Dr. Segal prepares the porous Silicon in her lab using an electrochemical synthesis. The process enables the researcher to control the density of the minuscule pores, their diameter – which can range from several nanometers to hundreds of nanometers – and to provide them with various geometric characteristics in order to cause them to adsorb different materials in a selective manner. When different molecules enter the pore space, a change in the optical surface characteristics commences in one of two ways: through photoluminescence – emission of light from the surface, or through a change in the refractive index of porous material that may result in a visual change in its color.

Using existing methods for detecting harmful bacteria contaminations, scientists must collect samples in the field, and then return to a lab to culture them for analysis - a process that takes a minimum of 24 hours. The identification and quantification in the lab, while accurate, requires a lot of time, skilled manpower and the use of complex and expensive equipment. Dr. Ester Segal and her graduate students, Naama Massad-Ivanir and Giorgi Shtenberg have sped up the process of analyzing bacterial concentrations to a few minutes, through the development of new porous Silicon-based biosensors that enable in-field rapid-detection.  The porous Si biosensor chip is programmed to exhibit an optical characteristic in the range of visible light,” explains Dr. Segal. “We attach a polymer arm to the chip, which serves to connect specific antibodies to the bacterium. This special structure traps bacteria on the silicon surface. The ‘trapped’ bacteria cause changes in the light spectrum reflected back from the chip, enabling us to determine its concentration in real time”.

In a paper recently published in the scientific journal, Advanced Functional Materials, Dr. Segal reported about the success of her research.  The biosensors are sensitive enough to identify within minutes an infection by E. Coli. bacteria in concentrations of 10³-10⁵ units per mL^-1. The new biosensor represents a field-portable alternative to more expensive procedures, particularly where larger-scale, expensive equipment is not readily accessible. This method can also be efficient against biological terror threats and for identifying contamination in drinking water, food and the environment.

All included

Dr. Segal’s vision is to develop an “all inclusive” chip that will contain many tests in parallel, that is – will be able to identify different bacteria and toxins that are liable to be found in drinking water or food. The chip would transmit the data to a data bank that analyzes the results and sends appropriate warnings to users. There is a way to go before such a chip is feasible, but Dr. Segal believes that by identifying and defining the vision, the research gets channeled into a practical direction.

An additional field with a practical aspect, which also occupies Segal, is sensors for identifying phospho-organic molecules of nerve gas. This research is likely to be greatly significant for the defense industry.

Dr. Segal explains that there is not necessarily a tension between a practical-orientated research and a basic research and that the two complement each other. In order to get funding there is sometimes a need, according to her, to think in terms of practical applications. Nonetheless, the way for implementation must always pass through basic research. At the end of the day, the questions that occupy and excite her on a daily basis are basic research issues. In her field of study, this is expressed in the attempt to understand the interface between a synthetic transducer and the material being tested. This is a complex and fascinating field, which also has “practical” implications, says Segal.

It is difficult to finish a conversation with a young faculty without asking about her teaching experience. “Teaching is a demanding aspect of a faculty career” admits Segal with a smile. “On the one hand, I ascribe great importance to teaching, I see it as a mission, and certainly want to succeed in it. Teaching is very demanding, and it is not so simple to find the time needed in parallel to all the other tasks I have. I can work till five in the morning in order to prepare a high quality lecture and at the end; the students will complain that the lecture was not uploaded on time to the course website so they could print it out before the class. But I am determined to find the right way. For example, one of the courses that I teach  deals with food packaging and I combine current issues and ideas that I support such as using recyclable materials and the principles of sustainability. This gives every topic added value, in my opinion.”