Preparation of Alginic Acid/Poly(2‐Oxazoline) Hybrid Gels and Their Use in Cell Preservation

Abstract

AbstractA hybrid gel is developed aiming to extend the storage period for cell preservation compared with an alginate gel. The introduction of poly(2‐oxazoline)s into alginic acid promises to improve functional materials by changing their functional groups (e.g., poly(2‐isopropyl‐2‐oxazoline) has the lower critical solution temperature behavior). This study demonstrates chemical modification of a carboxylate of sodium alginate by 1,3‐diaminopropane‐terminated poly(2‐oxazoline)s using 3‐ethylcarbodiimide hydrochloride (EDC) and N‐hydroxy succinimide (NHS) as the condensation reagents for the aminations. The incorporated ratio of poly(2‐oxazoline)s side chains into the carboxylates estimated by 1H NMR is ca. 5–12% and the remaining pendent carboxylates are used for gelation by adding calcium salts (CaCl2). Gelation is observed within 30 min producing 93–99% gel fractions that swell in water. Similar gelation occurs in the cultivation medium of green‐fluorescence protein (GFP)‐encoded and COVID‐19 spike protein‐encoded DNA recombinant E.coli in both the absence and presence of isopropyl β‐D‐1‐thiogalactopyranoside (IPTG). Even in the presence of IPTG, fluorescence ascribed to GFP is not observed while the cells are kept at 25 °C for 3 weeks. After solvation by ethylenediaminetetraacetic acid (EDTA), fluorescence intensity at 508 nm is clearly observed and cell preservation at room temperature is thereby demonstrated.