A synthetic method for the fabrication of colloidal mesoporous silica nanoparticles of a tunable mesopore size is presented. These nanoparticles form stable colloidal suspensions, have narrow particle size distributions in the 50-300 nm range and exhibit a framework-confined porosity made up of large mesopores with a diameter of up to 9 nm. The size of the rnesopores was enlarged by means of two different swelling agents (SA), i.e. 1,3,5-trimethylbenzene (TMB) and N,N-dimethylhexadecylamine (DMHA). Colloidal mesoporous silica nanoparticles exhibit a strong affinity for the adsorption of hemoglobin (Hb) and the immobilization of lysozyme (Lz). These nanoparticles can adsorb up to 2080 mg Hb g(-1) support and 690 mg Lz g(-1) support. Moreover, the adsorption of these biomolecules on silica nanoparticles occurs very quickly and most of what is adsorbed is accommodated on the external surface area of the silica nanoparticles. (C) 2010 Elsevier Inc. All rights reserved.