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.