DOPAMINE DETECTION VIA SURFACE ENHANCED RAMAN SCATTERING FOR PARKINSON’S DISEASE
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Abstract
Motion is controlled via the excitatory or inhibitory responses of the motor pathway by receptors in Substantia Nigra of the brain, modulated by a main neurotransmitter dopamine (DA). Parkinson’s Disease (PD) is the neurological disorder effecting many attributes resulting from brain tissue damage, with the main impact on the human kinetic behavior and estimated statistics of patients with PD at 7-10 million people worldwide. PD occurs when misfolded protein α-synuclein aggregates destroy the neuron cells at their synapse, where they disrupt the DA pathway from neuron to neuron, thus resulting in depletion of the DA the cellular communication system. The degree of PD can be monitored by focusing on DA levels, this goal requires a biofriendly scheme with high sensitivity and specificity design features. Here we present a nanoprobe utilizing the design for PD recognition by a DNA aptamer stem loop that will recognize small specific regions of the DA via a specific nucleotide complementary sequence. The DNA is sequenced with thiol that covalently bonds to gold nanoparticles (GNPs) coated with tannic acid. GNPs perform a plasmonic enhancement capable of 10^10 signal increase. The gold operates as a plasmonic enhancer to increase the response signaling of the probe. When a DA molecule is within proximity of the nanoprobe, the DNA binds the DA to the probe to create a signal change. The signal itself is a Raman Spectra induced laser that measures emission frequencies of the targeted area. Validation of probe components was indicated by Dark Field for GNP immobilization onto platform with 7mm^2 surface area with homogeneous or aggregated (by CuSO4) plasmonic effect, gel electrophoresis for bioreceptor DNA bonding to biotarget DA, and fluorescence Well Plate for DNA coupling to GNP. The two main SERS elements are GNPs and DA, SERS of GNPs demonstrated a broad band between 1200-1700cm^-1 with a sharp band inside between 1500-1700cm^-1 while SERS of DA shows target peaks at 1287cm^-1, 1456cm^-1 and 1611cm^-1. Expected sensitivity illustrates a limit of detection (LOD) of DA at 0.75nM with a linear range (LR) corresponding toward high accuracy range of signal output and DA concentration changes at 1nM-1µM. Expected selectivity illustrates the probe bioreceptor can distinguish between similar DA molecules norepinephrine and tyrosine, two molecules present with DA in brain tissue or patient samples, with an average higher binding rate toward DA. In conclusion, the nanoprobe utilizes a DNA aptamer as a bioreceptor and a gold nanoparticle (GNP) for signal enhancement. producing a SERS plasmonic enhancement 10^10 fold. Results indicate nanoprobe sensitivity is expected to relay a linear range of 1nM-1µM with a limit of detection at 0.75nM while selectivity of probe is expected to relay stronger bonding toward DA against similar structured molecules. Future plans include in vitro neuron chip coated with PD neurons and DA-probe to measure DA levels for neuron-neuron communication.