Hyaluronan molecular weight and polydispersity in some commercial intra-articular injectable preparations and in synovial fluid

The polydispersity of seven Hyaluronan (HA) commercially available samples was investigated. The biological source of all seven HA samples was rooster comb or bacterial fermentation. It can be practically excluded that the polysaccharide, produced in vivo by any of the above biological systems, might be molecularly homogenous, “monodisperse”. At present, on producing the commercially available HA samples, a whole range of physico-chemical procedures has to be applied, such as protein enzymatic digestion, HA ion-pair precipitation, membrane/molecular ultrafiltration, HA non-solvent precipitation and/or lyophilization. Of these, at least the last mentioned procedure results in degradation of high molecular weight HA samples, and in the case of monodisperse polymers, this degradation is in turn invariably associated with an increase in their Mw/Mn parameters. Thus, we suppose that the true Mw/Mn values of the HA samples reported by Ghosh et al. in Inflammation Research 50 (2001) pp. 294 must be markedly higher than the reported ones, i.e. 1.04, 1.05, 1.06, 1.08. Along with a potentially improper separation performance of the Superose 6 column, another possible source of discrepancy might be the exploitation of the multi-angle light scattering (MALS) detector for the on-line estimation of the HA biopolymer Mn molecular weight values. There are namely several indications that the values of the Mw/Mn polydispersity parameters, determined by the GPC-MALS system are frequently underestimated. The Mw/Mn values generated by exploiting the GPC-MALS arrangement would thus require a more critical evaluation.