Surface functionalized barium sulfate nanoparticles: controlled in situ synthesis and application in bone cement

The controlled synthesis of surface functionalized BaSO₄ nanoparticles with a diameter below 50 nm is achieved by combining the in situ generation of SO₄ ^2- and the use of a difunctional surface modification agent, (2-(methacryloyloxy)ethyldimethyl-(3-sulfopropyl)ammoniumhydroxide (MSAH). Particularly, a pre-decomposition process of the SO₄ ^2- precursor (S₂O₈ ^2-) is applied to decouple the in situ generation of SO₄ ^2- and precipitation of BaSO₄. As a result, the nucleation and growth of the BaSO₄ particles is manipulated, which significantly reduces the particle size. Different combinations of the pre-decomposition time and MSAH/BaCl₂ molar ratios showed a remarkable influence on the morphology and surface functionality of the BaSO₄ particles. Furthermore, the morphology control by using other difunctional surface modification agents e.g. 3-sulfopropylmethacrylate potassium salt (SMPS) and 2-acrylamido-2-methylpropane sulfonic acid (AMSA) is examined. The MSAH-functionalized BaSO₄ nanoparticles, used as s filler in bone cements, effectively improved the bending modulus and compressive strength of the poly (methyl methacrylate), PMMA, bone cements. The bone cement with MSAH-functionalized BaSO₄ nanoparticles exhibited good radiopacity. Moreover, in vitro cell culture experiments demonstrated an improved biocompatibility compared to the bare BaSO₄ particles. The MSAH-functionalized BaSO₄ nanoparticles may be an ideal candidate material as a bone cement filler.