Tuning the incorporation of electroactive metals into titanium phosphate nanoparticles and the reverse metal extraction process: Application as electrochemical labels in multiplex biosensing

•Titanium phosphate nanoparticles were modified with electroactive metals.•The amount of metal introduced into the nanoparticles could be tuned.•Acidic media were successfully used to extract and detect the metals.•Cu and Hg were the most promising metals (sensitivity and selectivity).•A multiplex biosensor was developed using the modified nanoparticles.

In this work, titanium phosphate nanoparticles were modified with different electroactive metals (cadmium, bismuth, copper, silver and mercury), by a cation-exchange reaction. The amount of metal introduced into the nanoparticles depended strongly on the counter-ion used during the exchange reaction and the type of metal. Nanoparticles with a high metallic load could be generated. The electrolytic medium played an important role in the detection of these metal-modified nanoparticles, since the use of acid makes it possible to extract a large part of the introduced metal by reversing the cation-exchange reaction. The application of these nanoparticles in electrochemical detection was evaluated, the nanoparticles modified with copper and mercury proving superior in terms of sensitivity and selectivity in multiplex detection. As a proof of concept, these nanoparticles were used as labels in a multiplex electrochemical biosensor for the simultaneous detection of two analytes.

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