NMR velocity imaging of the flow behaviour of hyaluronan solutions

Hyaluronan (hyaluronic acid) solutions are widely used in medicinal applications due to their biological compatibility and rheological properties. This work uses the technique NMR velocity imaging to study the flow behaviour of hyaluronan solutions pumped through Teflon tubing. Three commercially available hyaluronan solutions, (Healon®, Healon® GV and Healon®5) were investigated along with a set of samples with concentrations ranging from 1 to 23 mg ml−1 and weight average molecular weight, M̄w, between 0.3 and 5.2×106. The shape of the velocity profiles were found to vary significantly with M̄w, concentration and apparent shear rate. Transitions were observed from near Newtonian flow to shear thinning to wall slip with increasing M̄w and concentration. Solutions with the highest M̄w and concentration showed possible ‘shear banding’ effects in addition to wall slip with a distinctive region of high shear with an annulus of around 50 μm at the edge of the tube.