Smart transformation of bowl shape chitosan nanomotors to disc shape in simulated biological media and consequent controlled velocity

The design of nanomotors appropriate for targeted drug delivery to cancer cells have been extensively investigated in recent years. By Pickering emulsion method, nanomotors based on platinum nanoparticles and chitosan chains were synthesized and placed on a substrate of SiO2 nanoparticles using a crosslinking agent containing a disulfide bond. The SiO2 fraction was removed, and the final chitosan-platinum nanomotor was prepared with a bowl-shaped structure. Platinum is the motor of this particle and leads to the movement of nanoparticles in the presence of H2O2 fuel. Therefore, it predicts this nanomotor can move toward the media with higher concentration of peroxide, like cancerous tissues. This nanomotor is designed in such a way that by reaching the media with higher concentration of dithiothreitol (DTT), it stops. This controllability is derived from the change in the morphology of nanomotors from bowl-shape to disc-shape. The results showed that the synthesized nanomotor could act as a biosensor for detecting cancer cells because it is sensitive to specific factors such as pH, H2O2, and DTT. The minimum required values of H2O2 and DTT needed to move the nanomotors were determined by chronoamperometry and found to be 0.1 and 2%, respectively. The release of quercetin as an anti-cancer drug from the nanomotor showed that at acidic pH, the presence of H2O2 and DTT increases the drug release compared to normal conditions. The result of the MTT assay also confirmed that the nanomotors showed more toxicity in the presence of more H2O2 in cancer cells.