Large pore raspberry textured phosphonate@silica nanoparticles for protein immobilization

This paper reports the synthesis of large pore (11 nm) monodisperse raspberry textured phosphonate@silica nanoparticles (70-90 nm) with high capacity for protein immobilization. The raspberry nanoparticles denoted RNP_PME(2.5) with phosphonate loading 2.5 mmol g^-1, formed using an organosilanephosphonate (MeO)₃SiCH₂CH₂PO(OMe)₂, as silica surface modifier and structure directing agent. Specific reaction conditions including temperature and concentration of phosphonate, base, surfactant and co-solvent were required for RNP_PME(2.5) formation. Rhodamine B labelled RNP_PME(2.5) was readily internalised by HeLa cells with no deficit of cell viability. Aqueous dispersions of RNP_PME(2.5) were stable over several months. In protein immobilization studies using BSA, bovine serum albumin, with RNP_PME(2.5), smaller pore (∼3 nm) phosphonate@silica nanoparticles NP_PME(1.0) and NP_PME(0.2) and mesoporous silica nanoparticles, MSN, the large pore RNP_PME(2.5) gave highest BSA loading 266 mg g^-1, formed the most stable aqueous dispersions (BSA@MSN was unstable and precipitated) and gave the best protection against BSA structural distortion at pH 7.4.