Potassium hexacyanoferrate 2 trihydrate k4 fe cn 6 3h2o

Potassium hexacyanoferrate (II) trihydrate (K₄[Fe(CN)₆]·3H₂O) and iron (III) chloride hexahydrate (Fe(Cl)₃·6H₂O) were purchased from Sigma-Aldrich. All synthetic procedures were conducted using deionized (DI) water for synthesis purchased from Sigma-Aldrich (catalog #848333). Prussian blue nanoparticles (PBNPs) were synthesized using a scheme as described previously [6 (link),40 (link),41 (link)], and characterized for uniformity (Figure S1). Briefly, an aqueous solution of 1.0 mM FeCl₃·6H₂O in 20 mL of DI water was added under vigorous stirring to an aqueous solution containing 1.0 mM of K₄Fe(CN)₆·3H₂O in 20 mL of DI water. After stirring for 15 min, the precipitate was isolated by centrifugation in equal parts DI water and acetone (10,000× g for 10 min) at room temperature, and rinsed by sonication (5 s, 40% amplitude) in DI water using a Q500 sonicator (QSonica LLC, Newton, CT, USA). The isolation and rinsing steps were repeated three times before the particles were resuspended by sonication in DI water. To measure the physical properties of the nanoparticles, size (hydrodynamic diameter) and charge distributions (zeta potential) were measured using dynamic light scattering on a Zetasizer Nano ZS (Malvern Instruments, Malvern, UK).

PBNCs were synthesized according to methods described previously²⁶ . 150 mL of 0.04% (w/v) dextran-coated iron oxide (Fe₃O₄) nanoparticles in deionized ultra-filtered water were vigorously mixed with 5 mL of 5% w/v potassium hexacyanoferrate(II) trihydrate (K₄Fe(CN)₆·3H₂O, Sigma-Aldrich, St. Louis, MO, USA). After one minute, 2.496 mL of 1.85% (v/v) hydrochloric acid (HCl, Sigma-Aldrich, St. Louis, MO, USA) was added. To alter PBNC size, the diameter of the iron oxide nanoparticles was altered. Dextran-coated iron oxide nanoparticles with a diameter of 10 nm (Ocean NanoTech, San Diego, CA, USA) produced 200 nm PBNCs. Iron oxide nanoparticles with a diameter of 2 nm produced 20 nm PBNCs. Transmission electron microscopy (TEM) (Hitachi HT7700 TEM, IEN/IMAT Materials Characterization Facility, Georgia Institute of Technology) was used to visualize particle size and shape (Supplementary Fig. 1). PBNCs were sterilized under UV light for at least 12 hours prior to all experiments.