Title : Biosensor with acetyl-choline-esterase enzymatic receptor and si-nanoporous layer as entrapping element - Extrapolated to para-sympathomimetic pesticides
Abstract:
The Acetyl-cholinesterase enzyme, also noted AcHE, has the code - EC 3.1.1.7, being an enzyme that degrades by hydrolysis the acetylcholine (AcH) neurotransmitter in choline and acetate. In vivo, this enzyme is found at neuromuscular junction or cholinergic synapses from the central nervous system. The AcHE has a high catalytic activity — each molecule of AcHE can degrade about 25000 molecules of acetylcholine per second, [1]. This operation principle was extrapolated to the para-sympathomimetic pesticides. They work through the inhibition of AcHE, permitting acetylcholine to transfer nerve impulses indefinitely and causing a variety of symptoms such as weakness or paralysis. They operate by disrupting the sodium/potassium balance of the nerve fiber, forcing to a continuously transmission through the nerve. Paraoxon is a novel generation of para-sympathomimetic pesticide, acting as an inhibitor for AcHE. Chemicals from this group can act on two directions: (i) directly - stimulating the nicotinic or muscarinic receptors, or (ii) indirectly - by the cholinesterase inhibition and supporting the acetylcholine releasing. In this way, Paraoxon prevents the acetylcholine breaking, favoring the time action of this neurotransmitter, so that the entire control of the parasympathetic nervous system can be transferred against the pests, [2].
Using some monitoring tools, like electronic biosensors, the pesticides can be put under control. Microelectronics offers some convenient transducers. Borrowing micro-technological processes, the enzymatic biosensors can be integrated onto the Silicon wafers. This work depicts in details the key-technological processes from a Clean Microelectronic Room to produce a Paraoxon biosensor. The key processes must be compatible both with the enzymatic membrane deposition and the Si-technology. In this way, a high series production of biosensors at lower cost is possible. A good entrapping occurs if the enzyme is captured on a nano-porous thin layer by adsorption combined with other cross-link methods. A main advantage of the Si-nano-porous layer directly grown on a wafer consists in strong anchoring to the Si-substrate. Converting p-type Si in Si-porous by anodization, is a solution. Then some technological steps, with tests and microscopy analysis are presented. Finally, the preliminary tests of the developed biosensor with the AcHE enzyme immobilized onto the Si-nano-porous layer are discussed.
Audience Take Away
- How a biosensor of pesticides using AcHE enzyme and Si-substrate can be co-integrated
- Si nano-porous structure action is presented
- The presented technique can be used to expand the research field of neurotransmitters biosensors
- The issue provide a practical solution to co-integrate biomaterials near electronic devices
- The presented solutions could improve the accuracy of a biosensor design
