Polymer - colloidal particle mixtures are encountered in many industrial products like paints, agricultural, home and personal care, and pharmaceutical products. Understanding the interactions and stability of such soft mater systems, where biopolymers are added both to alter material and particle surface properties, in many cases remains a challenging task. Here we present results on stabilisation of colloidal particles of sparingly soluble minerals by deposition of bio-polyeletrolytres. Because of the strong electrostatic interactions with ions, the bio-polyectrolytes can absorb on the particles, can partially dissolve the colloidal particles, and also form insoluble complexes with free ions. These interactions result in change of stability and material properties of the system.