Quantification and biodegradability assessment of meso-2,3-dimercaptosuccinic acid adsorbed on iron oxide nanoparticles.

Many interesting applications of magnetic iron oxide nanoparticles (IONPs) have recently been developed based on their magnetic properties and promising catalytic activity. Depending on their intended use, such nanoparticles (NPs) are frequently functionalized with proteins, polymers, or other organic molecules such as meso-2,3-dimercaptosuccinic acid (DMSA) to improve their colloidal stability or biocompatibility. Although the coating strongly affects the colloidal properties and environmental behaviour of NPs, quantitative analysis of the coating is often neglected. To address this issue, we established an ion chromatographic method for the quantitative analysis of surface-bound sulfur-containing molecules such as DMSA. The method determines the amount of sulfate generated by complete oxidation of sulfur present in the molecule. Quantification of the DMSA content of DMSA-coated IONPs showed that reproducibly approximately 38% of the DMSA used in the synthesis was adsorbed on the IONPs. Tests for the biodegradability of free and NP-bound DMSA using a microbial community from a wastewater treatment plant showed that both free and NP-bound DMSA was degraded to negligible extent, suggesting long-term environmental stability of DMSA-coated IONPs.

Chitosan supraparticles with fluorescent silica nanoparticle shells and nanodiamond-loaded cores.

Spherical colloidal structures with a sparsely or densely packed shell of nanoparticles have been the subject of intense research efforts for more than a decade. Research has focused on the utilization of aqueous, soft, or solid cores mainly on the micron-scale. A synthesis route that combines a stabilizing biopolymer core in combination with small (15 nm) or ultrasmall (5 nm) nanoparticles templated on the surface is still missing and pivotal to push these structures further into bionanotechnological applications. Here, we present core-shell supraparticles with a nanodiamond-loaded chitosan core and a shell assembled from fluorescent silica nanoparticles with controlled packing density which feature final sizes significantly below one micrometer. The synthesis route is highly versatile and represents a general approach for the synthesis of sophisticated supraparticles with shells formed from distinct nanoparticle shells and biopolymer cores loaded with selective nanoparticles.