Apoferritin-templated synthesis of encoded metallic phosphate nanoparticle tags

Encoded metallic phosphate nanoparticle tags, with distinct encoding patterns, have been prepared using an apoferritin template. A center cavity structure as well as the dissociation and reconstructive characteristics of apoferritin at different pH environments provides a facile route for preparing such encoded nanoparticle tags. Encapsulation and diffusion approaches have been investigated during the preparation. The encapsulation approach, which is based on the dissociation and reconstruction of apoferritin at different pHs, exhibits an effective route to prepare such encoded metallic phosphate nanoparticle tags. The compositionally encoded nanoparticle tag leads to a high coding capacity with a large number of distinguishable voltammetric signals, reflecting the predetermined composition of the metal mixture solution (and hence the nanoparticle composition). Releasing the metal components from the nanoparticle tags at pH 4.6 acetate buffer avoids harsh dissolution conditions, such as strong acids. Such a synthesis of encoded nanoparticle tags, including single-component and compositionally encoded nanoparticle tags, is substantially simple, fast, and convenient compared to that of encoded metal nanowires and semiconductor nanoparticle (CdS, PbS, and ZnS) incorporated polystyrene beads. The encoded metallic phosphate nanoparticle tags thus show great promise for bioanalytical or product-tracking/identification/protection applications.