doi:10.1038/nindia.2014.122 Published online 7 September 2014
Researchers have fabricated a sensitive sensor that can detect minute traces of ferritin, a protein that stores iron in human blood1. They developed the sensor by modifying nanoparticles consisting of silver and cadmium sulphide with ferritin molecules.
This sensor is potentially useful for measuring blood ferritin levels, which can be used to diagnose anaemia, iron overload, cancers and other diseases.
Existing sensors for detecting ferritin have low sensitivities. To develop a high-sensitivity ferritin sensor, the researchers synthesized nanoparticles with silver cores and cadmium sulphide shells. They then modified these nanoparticles with cysteine and imprinted them with ferritin molecules. Finally, they coated a pencil graphite electrode with the ferritin-imprinted core–shell nanoparticles.
They compared the ferritin-sensing efficiency with that of a sensor without ferritin.The researchers performed electrochemical measurements on the sensor by exposing it to phosphate buffer solutions with various ferritin concentrations. They found that the ferritin molecules in the solution bound to cavities on the sensor surface, which caused the current to increase with increasing ferritin concentration up to a concentration of 23 micrograms per litre.
When ferritin concentrations exceeded 23 micrograms per litre, the current became constant, indicating that all available cavities on the sensor surface were occupied by ferritin molecules.In optical measurements, the researchers found that the fluorescence intensity of the sensor decreased with increasing ferritin concentration.The sensor retained 95% of its initial sensing ability after three weeks.
Furthermore, the sensor selectively detected ferritin even in the presence of interfering agents such as amino acids and salts, which are usually present in human blood. The researchers successfully used this sensor to measure ferritin levels in blood samples from five men and women, suggesting its potential application in a clinical set-up.