Nanoparticles, after incubation in biological fluids, adsorb several kinds of biomolecules like lipids, sugars and mainly proteins with high affinities for the nanoparticle surface and with long residence time, forming the so-called hard corona. The biological machinery, such as cellular barriers and membrane receptors can directly engage with the protein corona while the pristine surface may remain inaccessible. Here we isolate nanoparticles associated with strongly bound biomolecules from the unbound and loosely bound ones, by different approaches: centrifugation, size exclusion chromatography and magnetic isolation. The different separation methodologies, despite requiring diverse time and operating mechanisms, gave nanoparticle-hard corona complexes which were found to be remarkably similar in both dispersion properties and protein composition thus proving to be equally valid.