NMR velocity imaging of the flow behaviour of hyaluronan solutions

Understanding hyaluronic acid induced variation of water structure by near-infrared spectroscopy

In order to understand the hydration effect of hyaluronic acid (HA) in aqueous solution, near-infrared (NIR) spectroscopy was used to investigate the HA aqueous solutions at different concentrations and temperature. As HA concentration was raised, there was a nonlinear change in absorption value in the first overtone region of OH, indicating the changes of hydration water. A reconstructed spectrum based on principal component analysis (PCA) was established and analyzed with the concept of aquaphotomics. The results showed that HA acted as a structure maker to make water molecules arranged in order. Water species with two hydrogen bonds (S2) and three hydrogen bonds (S3) showed the decrease at low concentration range of 0-40 mg/mL, but increased at higher concentration, indicating the difference in water species at different HA concentration. Meanwhile, HA had the ability to improve the thermal stability of water structure, suggesting a potential bio-protective function. This study provides a unique perspective on the molecular interactions between HA and water molecules, which is helpful for understanding the role of HA in life process and may serve as the basis for HA applications.

Comparative study of hyaluronic derivatives: rheological behaviour, mechanical and chemical degradation

Depolymerisation by oxytetracycline (OTC) as well as the progressive cleavage of hyaluronic acid induced by ultrasound was investigated in nine commercially available hyaluronic polymers. Sample solutions differed in molecular weight, from 500 to 7000 kDa, and in their source. The hyaluronic acid concentration in each sample was analysed by HPLC. The concentration range was over 8.39-10.18 mg ml(-1) in samples with a nominal concentration of 1%, and 14.05 mg ml(-1) in one sample with a nominal concentration of 1.5%. It was found that stability was dependent on both molecular weight and the concentration of the samples. The rheological parameters n (power law index) and K (consistency coefficient) were good predictors regarding the degradation behaviour. Although many factors are involved in obtaining a therapeutic response, the results obtained in this work support the notion that both mechanical and chemical degradation are reduced in hyaluronate solutions with low molecular weight, the final concentration of the product being a critical factor.