nanoporous silica particles were synthesized and characterized as described previously and as detailed in supplementary figure 1 and the supplementary methods section . particles larger than 150-nm in diameter were removed via differential centrifugation or size - exclusion chromatography ( see supplementary figs . 1a and 1d ) . protocells were formed by fusing 120-nm liposomes to the nanoporous core as reported previously , and the composition of the slb was optimized to reduce non - specific binding associated with cationic and , to a lesser extent , anionic lipids ( see supplementary fig . 5 ) . zwitterionic lipids ( dopc or dppc ) with 5 wt% phosphatidylethanolamine ( dope or dppe , respectively ) , 5 wt% peg-2000 pe ( 18:0 or 16:0 , respectively ) , and 30 wt% cholesterol were used in all further studies ; pegylated lipids were incorporated into the liposomes used for fusion and are , therefore , expected to be present on both the inner and outer leaflets of the slb . the size of the nanoporous core was also optimized to attain a balance between achievable cargo capacity and the rate of protocell internalization ( see supplementary fig . 9 ) ; nanoparticles 100- to 150-nm in diameter were employed in the delivery of drugs , drug cocktails , sirna cocktails , and protein toxins . the nanoporous cores were soaked in a 10 mm solution of cargo(s ) for 1 - 12 hours prior to liposome fusion ; individual components of the surrogate cargo mixture ( fig . the rates of cargo release were optimized by incorporating various percentages of aeptms , an amine - containing silane , into the sol used to form nanoporous cores ( see supplementary fig . particles containing 15 wt% aeptms were used to deliver drugs and drug cocktails ( fig . 6 ) , while particles containing 20 wt% aeptms were used to deliver the multicomponent mixture ( fig . 5 ) , the sirna cocktail ( supplementary figs . 13 and 14 ) , and diphtheria toxin a - chain ( supplementary figs . 15 and 16 ) .