IMPLICATIONS OF STORAGE CONDITIONS ON THE CHARACTERISTICS OF ALGINATE DIALDEHYDE AND ITS HYDROGELS

Abstract A review of recent literature reveals a spurt in the publications using alginate dialdehyde (ADA)‐based hydrogels. This study evaluates the stability and characteristics of ADA solutions stored at different temperatures (4 & −20 °C; designated as ADA 4°C & ADA −20°C ) and durations (1, 3, and 6 months), and gives valuable insights into the shelf life, a parameter important in a clinical setting. ADA solutions were characterized for their viscosity, aldehyde content, molecular weight, and chemical structure before and after storage. The solution viscosities of ADA 4°C showed a decreasing trend over 6 months while that of ADA‐ 20°C showed an increase. Compared to freshly prepared ADA, a significant reduction in aldehyde content, from 40.1±1.4 % to 37.1±1.01 %, was observed for ADA 4°C stored for 6 months, but the aldehyde content was stable for ADA −20°C stored for the same period. Molecular weight remained stable (~6800 g/mol) irrespective of the storage temperatures. Injectable hydrogels were prepared by reacting the stored ADA solutions with 20 % aqueous solutions of gelatin. Hydrogels prepared with ADA stored at 4 °C for 6 months showed a significant increase in gelation time from 4.3±1.5 to 8.79±0.1 min and a decrease in degree of crosslinking from 54.3±1.4 % to 29.2±2.3 %. A decreasing trend was observed for properties such as water uptake (from 470 to 961 %) and tensile strength (from 348 to 282 kPa). Hydrogels made with ADA −20°C demonstrated better retention of physicochemical properties over time. In vitro studies revealed that the hydrogels showed a non‐cytotoxic response towards L929 cells irrespective of the storage conditions. LIVE/DEAD assay and F‐Actin staining revealed good cell proliferation on the hydrogels. In conclusion, retention of the properties of ADA in its aqueous solution requires careful control of storage temperatures.