Physicochemical features of ultra-high viscosity alginates

The physicochemical characteristics of the ultra-high viscosity and highly biocompatible alginates extracted from Lessonia nigrescens (UHVN) and Lessonia trabeculata (UHVT) were analyzed. Fluorescence and 1H NMR spectroscopies, viscometry, and multi-angle light scattering (MALS) were used for elucidation of the chemical structure, molar mass, and coil size. The sequential structures from NMR spectroscopy showed high guluronate content for UHVT, but low for UHVN. Intrinsic viscosity [η] measurements exhibited unusual high values (up to 2750 mL/g), whereas [η] of a commercial alginate was only about 970 mL/g. MALS batch measurements of the UHV-alginates yielded ultra-high values of the weight average molar mass (Mw up to 1.1 × 106 g/mol) and of the z-average gyration radius (〈RG〉z up to191 nm). The Mw and 〈RG〉z distributions of UHV-alginates and of ultrasonically degraded fractions were determined using size exclusion chromatography combined with MALS and asymmetrical flow-field-flow fractionation. The Mw dependency of [η] and 〈RG〉z could be described by [η] = 0.059 × Mw0.78 and 〈RG〉z = 0.103 × Mwx. (UHVN: x = 0.52; UHVT: x = 0.53) indicating that the monomer composition has no effect on coil expansion. Therefore, the equations can be used to calculate Mw and 〈RG〉z values of UHVT- and UHVN-alginate mixtures as used in immunoisolation. Furthermore, the simple and inexpensive capillary viscometry can be used for real-time validation of the extraction and purification process of the UHV-alginates.

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