A chip for detecting Alzheimer's disease
Posted: 07 Apr 2011 10:16 AM PDT
A test to diagnose the onset of Alzheimer's disease at an early stage is under consideration. The goal is to allow, in the case of a positive test, to establish a therapy, if prophylactic least likely to slow the progression of the disease in its initial phase.
The protein "tau" is necessary for brain activity, but in people with Alzheimer's disease is found in excessive amounts in the cerebrospinal fluid. By detecting changes in concentrations, but also structures of this protein, it might be possible to diagnose the onset of the disease, which would allow for early management of patients and improve their quality of life. Is the axis on which Prof. Jiri Homola work , the Institute of Photonics and Electronics, Academy of Sciences of the Czech Republic  and his colleagues Daniela Ripova  Zdena Kristofikova  of the Prague Psychiatric Center . They are keen to develop a biosensor that can detect rapidly and precisely protein "tau" in its different forms. This is part of a research project supported by the Ministry of Health Czech has provided funding over 3 years.
"The key to the system resides in a chip coated with gold," said Katerina Hegnerova , which works with Jiri Homola. This chip, hardly larger than a SIM card and is made of quartz coated with a thin gold layer with a thickness of 55 nm. Bioactive molecules (bio-sensors), whose role is to recognize and capture the analyte, are distributed on the surface of the chip. An appropriate solution is used so that these molecules can retain their biological activity until they are used in the tests.
Hegnerova Katerina says: "Our work is very delicate. Each biosensor requires operational conditions of its own. There are various methods for molecular receptors to adhere to the plate of gold. It depends on the pH, ionic strength and many other factors. Develop technical attachment of a bio-sensor may take several weeks. "
The device also includes a glass prism, fixed to the chip. The surface of the latter is applied against a special flow chamber, in which one can flow from the cerebrospinal fluid. Directing a light beam onto the prism glass, the gold surface of the chip may be a "special electromagnetic wave", called "surface plasmon". The velocity of this phenomenon can be followed on monitors. The presence of Tau proteins congregating bio-sensors induces a decrease in this velocity. Distortions in the spectrum of light reflected from the prism are indicators of such delays. Jiri Homola for the developed device is highly sensitive, so "it can detect a concentration of Tau protein similar to a grain of salt dissolved in a pool of fifty meters long."