1. Department of Biology and Microbiology , Rīga Stradiņš University , 16 Dzirciema Str., Rīga , LV- 1007 , Latvia
2. Faculty of Medicine, Rīga Stradiņš University , 16 Dzirciema Str., Rīga , LV- 1007 , Latvia
3. Rūdolfs Cimdiņš Rīga Biomaterial Innovations and Development Centre , Rīga Technical University , 3 Pulka Str., Rīga , LV- 1007 , Latvia
4. Faculty of Material Science and Applied Chemistry , Rīga Technical University , 3/7 Paula Valdena Str., Rīga , LV- 1048 , Latvia