Good control of the morphology, particle size, uniformity and dispersity of mesoporous silica nanoparticles (MSNs) is of increasing importance to their use in catalyst, adsorption, polymer filler, optical devices, bio-imaging, drug delivery, and biomedical applications. This review discusses different synthesis methodologies to prepare well-dispersed MSNs and hollow silica nanoparticles (HSNs) with tunable dimensions ranging from a few to hundreds of nanometers of different mesostructures. The methods include fast self-assembly, soft and hard templating, a modified Stöber method, dissolving–reconstruction and modified aerogel approaches. In practical applications, the MSNs prepared by these methods demonstrate good potential for use in high-performance catalysis, antireflection coating, transparent polymer–MSNs nanocomposites, drug-release and theranostic systems.

Modern nanomedicine aims at delivering drugs or cells specifically to defective cells; therefore, this calls for developing multifunctional nanocarriers for drug delivery and cell-tracking. Mesoporous silica nanoparticles (MSNs) are well suited for this task. In this feature article, we highlight the strategies in the synthesis and functionalization of small, uniform and colloidal stable MSNs. We then discuss cell uptake of MSNs and tracking cells, as both aspects are closely related to the efficacy of drug delivery and theranostics. Some examples of stimulated drug delivery are described. For application considerations, toxicity and pharmacokinetics are critical issues and in vivo studies are summarized.