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Corinne Eenschooten; Novel Bacillus-derived Sodium Hyaluronate Hyasis® as Attractive and Flexible Ingredient for Ophthalmic Viscosurgical Devices. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2538.
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With a few exceptions a large fraction of today’s ophthalmic viscosurgical devices (OVDs) are based on hyaluronic acid (HA) of animal (rooster comb) or bacterial (Streptococcus) origin alone or in combination with other naturally occurring macromolecules. Novozymes Biopharma has developed a new bacterial fermentation technology based on Bacillus subtilis which does not employ any animal-derived raw materials or organic solvents. The resulting HA material Hyasis® with its high standards of purity and safety represents an attractive ingredient for OVDs. The purpose of this study was to evaluate the performance of Hyasis in model OVD compositions. To this end the properties of Hyasis formulated in typical OVD preparations were studied and compared to those of commercial products.
HA molecular weight (MW) was measured by Size Exclusion Chromatography - Multi Angle Light Scattering (SEC-MALS). Computations were performed using the Berry model with fit degree 2, a dn/dc value of 0.153 mL/g and a second virial coefficient of 2.3 10-3 mol.mL/g2. The rheological properties of the HA-based formulations were investigated with a rheometer (Physica MCR 301, Anton Paar) equipped with a Peltier temperature control system and mounted with a cone-plate geometry (1°, 0.051-mm gap).
The zero-shear viscosity of the formulations was an exponential function of the product of HA MW and concentration (C) while the shear-thinning character tended to increase with increasing this product. All formulations had low and comparable shear viscosity values at a shear rate of 1,000 s-1 indicating a good suitability for injection through conventional clinical needles. The frequency and modulus at crossover as well as the relaxation time were dependent on both MW and C while the modulus at crossover was an exponential function of C.
The results in agreement with previous literature present the advantage of exploring a wide range of molecular weights and concentrations. They also show that Hyasis-based formulations have rheological properties stretching over a large spectrum and meeting those of a number of currently available products. Hyasis can therefore be regarded as an attractive and flexible ingredient for a next generation of OVDs.
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