Enzymatically Active Polydopamine @ Alkaline Phosphatase Nanoparticles Produced by NaIO4 Oxidation of Dopamine

Polydopamine (PDA) deposition, obtained from the oxidation of dopamine and other catecholamines is an universal way to coat all known materials with a conformal coating which can subsequently be functionalyzed at will. The structural analogies between polydopamine and eumelanin, the black-brown pigment of the skin, incited to produce stable polydopamine nanoparticles in solution instead of amorphous precipitates obtained from the oxidation of dopamine. Herein, we demonstrate that size controlled and colloidally stable PDA based nanoparticles can be obtained in acidic conditions, where spontaneous auto-oxidation of dopamine is suppressed, using sodium periodate as the oxidant and a protein like alkaline phosphatase as a templating agent. The size of the PDA@Alp  nanoparticles depends on the dopamine/enzyme ratio and the obtained particles display the enzymatic activity of alkaline phosphatase with an activity extending up to two weeks after particle synthesis. The PDA@ alkaline phosphatase (Alp) nanoparticles can be engineered in polyelectrolyte multilayered films to potentially design model biosensors.