A method for the preparation of a delivery drug delivery system comprising one or more active pharmaceutical ingredients having solubility in water of less than 1g in 30ml of water and nano-diamond, the method comprising the steps of (a) dissolving the active pharmaceutical ingredient(s) into a polar non-aqueous solvent to form a first mixture (b) dissolving a surfactant in deionized water to form a surfactant solution (c) adding a plurality of nano-diamond particles to the surfactant solution to disperse the nano-diamond particles in the surfactant solution thereby forming a nano-diamond dispersion (d) adding the first mixture to the nano-diamond dispersion whilst agitating the dispersion to form a second mixture and (e) drying the second mixture to produce a dry powder for use as a drug delivery system. A composition for medical treatment comprising: a plurality of nano-diamond particles and an active pharmaceutical ingredient having a solubility in water of less than 1g in 30ml of water wherein the composition is a dry powder having an average particle size in the range 500nm or less when dispersed in deionised water is also provided.
