The sensor is not sensitive to the pH of the environment and it can be used at all pH values, including physiologic pH. It has many applications in clinics and hospitals to diagnose the disease.
Heparin plays an important role in the clotting of blood, and its performance depends on its concentration in the blood. Therefore, it is highly important to measure the amount of this material in blood plasmon in patients who suffer from cardiovascular illnesses.
Heparin is a polyanion chemical compound that has negative charges. In the previous methods to measure heparin by using gold nanoparticles, the environment pH had to become acidic so the nanoparticles would have positive charges. According to Coulomb interaction between the positive charges of nanoparticles and negative charges of heparin, the colloidal nanoparticles aggregated and the space between them was very small. As a result, the color of the solution changed due to the changes in gold resonance plasmon spectrum. Ionic liquid based on imidazole were used in this research instead of the common filling agents. By controlling the concentration of ionic liquids, positive charges are formed on the surface of nanoparticles. Interestingly, the positive charge is independent of pH value, and this characteristic was used in this research.
The produced sensor is very sensitive to heparin and it can be used in in-situ analysis. The most important characteristic of the sensor is its functionality at physiologic pH. Results of the research also showed the possibility of the use of a camera to take photos to analyze heparin instead of using spectrophotometer device.