Nanodiamond particle complexes

A method of making a soluble complex comprising:

• mixing a nanodiamond particle with a therapeutic agent in the presence of an acid solution such that said therapeutic agent adsorbs to said nanodiamond particle thereby forming a soluble complex, wherein said therapeutic agent is inherently water-insoluble or poorly water soluble.

A composition comprising a nanodiamond-nucleic acid complex, wherein said complex comprises:

• a) nanodiamond particles comprising one or more surface polyethyleneimine molecules;
• and
• b) nucleic acid molecules, wherein said nucleic acid molecules and said nanodiamond particles form a nanodiamond-nucleic acid complex.

A composition comprising an alkaline-sensitive nanodiamond-protein complex, wherein said alkaline-sensitive nanodiamond complex comprises:

• a) a nanodiamond particle comprising one or more surface carboxyl or hydroxyl groups;
• and
• b) a protein, wherein said protein is adsorbed to said nanodiamond particle to form said alkaline-sensitive nanodiamond-protein complex, wherein said protein is configured to desorb from said nanodiamond particle only under sufficiently alkaline conditions.

A composition comprising a soluble complex, wherein said soluble complex comprises:

• a) a nanodiamond particle;
• and
• b) a therapeutic agent, wherein said therapeutic agent comprises an anthracycline-class compound or tetracycline-class compound.