On the Biocompatibility of Bioactive Glasses (BGs)

Bioactive glasses (BGs) form a versatile class of biocompatible materials that can be utilized for various therapeutic strategies, including bone tissue engineering, soft tissue healing, and cancer therapy. Commonly, BGs are classified into three distinct categories, namely silicate, phosphate, and borate glasses. Several commercial BG-based products are now available on the market, and new generations with unique therapeutic features are also expected to introduce them in the near future. Due to their clinical significance, the biological behaviors of BGs have been one of the most interesting topics in tissue engineering and regenerative medicine. Although BGs are generally recognized as biocompatible materials in medicine, any new composition and formulation should be carefully tested through a series of standard in vitro and in vivo tests provided by international agencies (e.g., Food and Drug Administration (FDA)) and regulatory bodies (e.g., the International Organization for Standardization (ISO)). As a rule of thumb, the release of ionic dissolution products from BGs into the surrounding biological environment is regarded as the main parameter that modulates cellular and molecular phenomena. This process is even more crucial when specific elements (strontium, copper, etc.) are added to the basic composition of BGs to improve their physico-chemical properties, mechanical strength, and biological performance. Moreover, it is now well-established that some physical (e.g., the topography) aspects of BGs can directly affect their compatibility with the living systems (cells and tissues). Therefore, a multifaceted design and testing approach should be applied while synthesizing BGs in the laboratory, and the collaboration of materials and chemical engineers with biologists and medical experts can be really helpful for producing optimized formulations.