The Hydrodynamic Radii of Macromolecules and Their Effect on Red Blood Cell Aggregation

Abstract

The effects of nonionic polymers on human red blood cell (RBC) aggregation were investigated. The hydrodynamic radius (Rh) of individual samples of dextran, polyvinylpyrrolidone, and polyoxyethylene over a range of molecular weights (1,500-2,000,000) were calculated from their intrinsic viscosities using the Einstein viscosity relation and directly measured by quasi-elastic light scattering, and the effect of each polymer sample on RBC aggregation was studied by nephelometry and low-shear viscometry. For all three polymers, despite their different structures, samples with Rh <4 nm were found to inhibit aggregation, whereas those with Rh >4 nm enhanced aggregation. Inhibition increased with Rh and was maximal at approximately 3 nm; above 4 nm the pro-aggregant effect increased with Rh. For comparison, the Rh of 12 plasma proteins were calculated from literature values of intrinsic viscosity or diffusion coefficient. Each protein known to promote RBC aggregation had Rh >4 nm, whereas those with Rh <4 nm either inhibited or had no effect on aggregation. These results suggest that the influence of a nonionic polymer or plasma protein on RBC aggregation is simply a consequence of its size in an aqueous environment, and that the specific type of macromolecule is of minor importance.

Depletion interactions in polymer solutions promote red blood cell adhesion to albumin-coated surfaces

“…Secondly, RBC lack specific binding "sites" for dextran and whatever adsorption occurs is weak and non-specific, with the magnitude of any adsorption questionable due to measurement difficulties [18]. In addition we and others have shown that dextran is depleted from the RBC surface [8,12,19]. Consequently, our findings suggest that the observed attractive forces have their origin in polymer depletion near the RBC and coated glass surfaces.…”

Cellulose nanopapers as tight aqueous ultra-filtration membranes

“…From the graph, it can be seen that NFC-O exhibits the lowest MWCO, followed by NFC-K. For BC and CNC no MWCO could be determined within the range of standards tested. The MWCO for NFC-O was found to be 6 kDa, corresponding to a hydrodynamic radius of PEG, which represents the pore size, of 2.4 nm [36]. Thus, a MWCO close to the range of NF was observed.…”

“…Thus, a MWCO close to the range of NF was observed. For NFC-K nanopapers the MWCO was 25 kDa, which corresponds to a hydrodynamic radius of 5 nm [36]. It was demonstrated that it is possible to adjust the pore dimensions of the resulting nanopaper membranes by using cellulose nanofibrils of different diameters (see Fig.…”

Influence of hydrogel mechanical properties and mesh size on vocal fold fibroblast extracellular matrix production and phenotype

“…exceeding 20 kDa (data not shown). The 20 kDa dextran had a mean hydrodynamic radius of ~3.2 nm, whereas the next largest dextran investigated (40 kDa) had a mean hydrodynamic radius of ~4.5 nm [39]. Thus, the mesh size of the 30% 10 kDa hydrogel was taken to be ~(2 × 4.5) = 9 nm.…”