Removal of cytokines from HAS-containing solutions by adsorption onto silica

Interaction of biologically relevant proteins with ZnO nanomaterials: A confounding factor for in vitro toxicity endpoints

The results of in vitro toxicological studies for manufactured nanomaterials (MNs) are often contradictory and not reproducible. Interference of the MNs with assays has been suggested. However, understanding for which materials and how these artefacts occur remains a major challenge. This study investigated interactions between two well-characterized ZnO MNs (NM-110 and NM-111) and lactate dehydrogenase (LDH), and two interleukins (IL-6 and IL-8). Particles (10 to 640 μg/mL) and proteins were incubated for up to 24 h in routine in vitro assays test conditions. LDH activity (OD_LDH), but not interleukins concentrations, decreased sharply in a dose-dependent manner within an hour after exposure (OD_LDH < 60% of OD_ref for both MNs at 10 μg/mL). A Freundlich adsorption isotherm was successfully applied, indicating multilayer adsorption of LDH. ZnO MNs and LDH had neutral to slightly negative surface charges in dispersion, precluding electrostatic attachment. Particle sedimentation was not a limiting factor. Fast dissolution of ZnO MNs was shown and Zn²⁺ could play a role in the OD_LDH drop. To summarize, ZnO MNs quickly reduced OD_LDH due to concentration-dependent adsorption and LDH inhibition by interaction with dissolved Zn. The control of particle interference in toxicological in vitro assays should become mandatory to avoid misleading interpretation of results.

Adsorption of charged non-albumin bound drugs by amorphous silica

We investigated the in vitro drug adsorption of PQ 10150 sodium silicate gel (AIS, Santa Clara, CA) with particle size of 230 microns and surface area of 400 m2/g. We observed 99% to 88% adsorption of gentamicin; a mean 91% of disopyramide; a mean 89% of quinidine at low concentration, falling to 75% at higher concentration. Insulin was 88% adsorbed at low concentrations but less so (65%) at higher concentrations. We observed a mean 83% adsorption of procainamide, a mean 84% of N-acetyl procainamide, 74% of lidocaine, 73% of amitriptyline, and 44% of desipramine. We found an average of 14% reduction of total digoxin concentration when serum containing digoxin (2 to 33 ng/mL) was exposed to sodium silicate, while the reduction in free digoxin concentration was 16%. Five percent ethosuximide was also removed. The adsorption of theophylline, phenobarbital, acetaminophen, phenytoin, ethylene glycol, methotrexate, salicylate, thiocyanate and diazepam was minimal and not significant. We conclude that significant amounts of charged, non-albumin bound drugs can be removed by PQ 10150 sodium silicate gel.