The effect of ionotropic gelation residence time on alginate cross-linking and properties

• IGRT is the time of cross-linking, and deswelling and water migration (syneresis).
• Extent of alginate cross-linking can be determined using EDS.
• Surface and internal calcium concentration were determined separately.

The ability to engineer biocompatible polymers with controllable properties is highly desirable. One such approach is to cross-link carbohydrate polymers using ionotropic gelation (IG). Previous studies have investigated the effect of curing time on alginate cross-linking. Herein, we discuss a novel study detailing the effect of IG residence time (IGRT) on the cross-linking of alginate with calcium ions (Ca2+) along with water migration (syneresis) and their subsequent impact on the pharmaceutical properties of alginate particles. IGRT was shown to have a significant effect on particle size, porosity, density, mechanical strength and swelling of calcium alginate particles as well as drug release mechanism. Furthermore, we describe a novel application of electron dispersive spectroscopy (EDS), in conjunction with Fourier Transform- infra red (FT-IR) spectroscopy, to analyze and monitor the changes in Ca2+ concentration during cross-linking. A simple procedure to determine the concentration and distribution of the surface and internal Ca2+ involved in alginate cross-linking was successfully developed.