Laser-based assessment of nanoparticle effects on RBC aggregation: an in vitro study

Nanoparticles are increasingly used in biomedical research and clinical applications, including diagnostics, drug delivery, and theranostics, where systemic administration via the bloodstream is often required. As a result, nanoparticles inevitably interact with blood components, making the assessment of their hemocompatibility and potential effects on blood microrheology an important nanosafety issue. In this exploratory in vitro study, we examined how different nanoparticles influence red blood cell (RBC) aggregation using laser tweezers and laser aggregometry. Magnetic and non-magnetic nanodiamonds, as well as zinc oxide nanoparticles, were tested at various concentrations in human whole blood. Laser tweezers were used to measure pairwise RBC interactions, including aggregation forces and characteristic aggregation time, while laser aggregometry assessed the aggregation index and critical shear stress in large cell ensembles. The presence of nanoparticles altered the measured parameters under the present experimental conditions. This study was performed using blood from a single healthy donor; therefore, the findings should be considered preliminary and interpreted with caution with respect to inter-individual variability. The presence of nanoparticles significantly altered the microrheological parameters of blood. Concentration ranges that did not induce statistically significant changes in RBC aggregation parameters under the present in vitro conditions were identified: up to 40 μg/mL for non-magnetic nanodiamonds, 80 μg/mL for magnetic nanodiamonds, and 20 μg/mL for ZnO.