Nanoparticulate compositions

A topical dosage form comprising a dispersed phase and a diluent, wherein the dispersed phase comprises a plurality of oxidic nanoparticles, the oxidic nanoparticles having an elemental composition, as measured by atomic emission spectroscopy (AES), comprising:

• 10-50 wt % Si, when calculated as SiO2,
• 0-30 wt % Ca and/or Sr, when calculated as CaO and/or SrO,
• 5-30 wt % Na, when calculated as Na2O,
• 0-10 wt % P, when calculated as P2O5,
• 0-10 wt % Zn, when calculated as ZnO,
• 10-90 wt % Ce, when calculated as CeO2,
• 0-10 wt % Ag when calculated as Ag,
• 0-50 wt % Zr;
• when calculated as ZrO2, and
• 0-90 wt % Mn, when calculated as MnO2;
• wherein the oxidic nanoparticles have a hydrodynamic diameter of 10-2000 nm as measured by dynamic light scattering (DLS);
• wherein the oxidic nanoparticles comprise a first phase and a second phase, the first phase and the second phase being spatially separated, wherein
• the first phase is an amorphous phase, predominantly containing oxides of Si, optionally Ca and/or SR, Na, P and Zn, as determined by powder X-Ray diffraction analysis (XRD);
• and
• the second phase is a crystalline phase, predominantly containing Ceria and optionally Ag or Zr, as determined by powder XRD;
• and
• wherein the diluent comprises:
• water,
• citric acid,
• and optionally further pharmaceutically acceptable additives;
• and
• wherein a ratio of the oxidic nanoparticles:
• citric acid is from 0.1 to 100 wt/wt.