Modeling counterion partition in composite gels of BSA with gelatin following thermal treatment

- BSA and gelatin with added calcium chloride form phase separated gels.
- Blending law was adapted for the distribution of ionized calcium between the two phases.
- The formation of a continuous phase allows the polymer to hold preferentially ionized calcium.

This study deals with the distribution of added calcium ions and their effect on the phase behaviour of hydrogels made of bovine serum albumin and gelatin. Structural properties of single and mixed systems were identified using small-deformation dynamic oscillation in shear, microdifferential scanning calorimetry and scanning electron microscopy. The experimental procedure was designed to encourage formation of micro phase-separated materials, where i) a continuous gelatin matrix supported liquid BSA inclusions, ii) an inverted dispersion of gelled BSA was interspersed by liquid gelatin inclusions and iii) a rigid BSA phase supported softer filler particles of gelatin. The Lewis-Nielsen equations and a series of models developed by Takayanagi were adapted for predicting the phase behaviour of BSA/gelatin mixtures in the presence of added calcium chloride. As far as we are aware, this is the first attempt to model the partition of added counterions between polymeric phases in binary hydrogels based on classic blending law analysis.

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