The present invention relates to semi-permeable microcapsules, which exhibit an increased resistance to mechanical stresses as well as an increased resistance to chemical degradation. More specifically, this semi-permeable microcapsule has a bead enclosing a material such as living cells, covalently linked to a semi-permeable layer, made of a polycation cross-linking derivative, covering the bead. The present invention is also directed to a pharmaceutical composition comprising the above-mentioned semi-permeable microcapsules. The present invention is also directed to the use of such microcapsule in a method for microencapsulating a beaded material and in a method for treating diabetes in a subject.