Technion researchers have developed an innovative technology that enables detection of DNA sequences at a sensitivity over 1, 000 times higher than that of existing methods. The principles of the study could enable the development of a wide range of simple and relatively inexpensive medical diagnostic systems, for example in order to identify known mutations in DNA. The study is highlighted on the back cover article of the leading journal Advanced Functional Materials.
The research is a multidisciplinary collaborative effort of the research groups of Associate Professor Ester Segal (Faculty of Biotechnology and Food Engineering) and Assistant Professor Moran Bercovici (Faculty of Mechanical Engineering). Doctoral student Rita Vilensky, who conducted the study under their guidance, built a lab-on-a-chip device combining (1) a biosensor for optical detection of DNA molecules; and (2) a system of microchannels enabling the concentration of DNA by applying electric currents on the chip.
Professor Segal’s laboratory is developing optical biosensors based on silicon chips with nano-scale pores. The resulting perforated chip has a typical optical characteristic in the visible spectrum, ” explains Professor Segal. “We bind to it one of the complementary strands comprising the DNA molecule that we want to identify. When we expose the chip to many sequences we can specifically identify the recognition reaction between the complementary DNA sequences.”
“Specific capture of DNA molecules within the silicon nanostructure causes a change in the spectrum of light reflected from the chip and enables us to easily identify and quantify these molecules, thereby ‘catching’ the sequence and knowing how much of it we have.”
According to Professor Segal, one of the main limitations of this process is the sensitivity of the sensors, which is sometimes insufficient, especially for medical diagnostics applications. At this point, Professor Bercovici, who is developing microfluidic-based methods for increasing concentrations of biological molecules, joined the study. “By using the appropriate chemistry and applying electric fields, we can concentrate the DNA molecules in tiny volumes and transport them to the sensor, ” explains Professor Bercovici. “This way we ‘‘trick’ the sensor, presenting it with DNA concentrations that are 10, 000 times higher than the natural concentrations in the sample.”
Through precise design of the silicon’s structure and controlled growth of insulating oxide layers, the researchers were able to apply high electric voltages on the chip while preserving its unique nanostructure. “Combining the technologies has enabled us to improve the sensor’s sensitivity by a factor of between 1, 000 and 10, 000 compared with existing devices.”