Tewodros Asefa, Zhimin Tao

In this review, recent reports on the biocompatibility of mesoporous silica nanoparticles (MSNs) are reviewed, with special emphasis being paid to the correlations between MSNs' structural and compositional features and their biological effects on various cells and tissues. First, the different synthetic routes used to produce the most common types of MSNs and the various methods employed to functionalize their surfaces are discussed. This is, however, done only briefly because of the focus of the review being the biocompatibility of the materials. Similarly, the biological applications of MSNs in areas such as drug and gene delivery, biocatalysis, bioimaging, and biosensing are briefly introduced. Many examples have also been mentioned about the biological applications of MSNs while discussing the materials' biocompatibility. The cytotoxicity of different types of MSNs and the effects of their various structural characteristics on their biological activities, which are the focus of this review, are then described in detail. In addition, synthetic strategies developed to reduce or eliminate any possible negative biological effects associated with MSNs or to improve their biocompatibility, as necessary, are illustrated. At the same time, recent reports on the interactions between MSNs and various in vivo or in vitro biological systems, plus our opinions and remarks on what the future may hold for this field, are included.