Dopamine biosensors for blood samples was developed using chitosan at carbon dots (CHIT@CD) and the tyrosinase enzymes (Tyr) on the surface of screen-printed carbon electrode (SPCE) (SPCE/CHIT@CD/Tyr). CD were synthesized and tested by scanning electron microscope (SEM). It founds that the shape of CD like a tapered bar with the size of 2 x 5 micrometers. The other type is found in the sheet, which is approximately 5 x 5 micrometers. The energy-dispersive x-ray spectroscopy (EDX) study found the peak of the K-Carbon occurs at 0.25 keV with 61.94 weight percent of carbon as the main element. This CD was used as the center material for chitosan shelt stabilized as CHIT@CD.
The home-made SPCE has a resistance of 19.41 kilo-ohms. The SPCE/CHIT@CD/Tyr showed a good response, high repeatability and reproducibility. The developed biosensors provide high sensitivity to dopamine at 36.67 ?A mM-1. It has a wide linearity range (0.1 ?M – 0.10 mM), with a very low detection limit of 0.036 ?M and without interfered from ascorbic acid, ethanol, glucose and sucrose.
The stability test of the developed dopamine biosensor found that the current reduced to 90 percent at 17 times usage and still more than 50 percent when 25 times usage. It is meaning that the developed electrode is stable for 25 times. Moreover, the developed dopamine biosensors had been tested with real blood samples without having sample preparation. It provided a percentage recovery in the range of 99.79 – 104.82 percent.