Chapter 2: Inorganic Materials in Drug Delivery

Drug delivery systems are used to carry an active pharmaceutical ingredient (API) in order to improve its properties, for instance enhancing the precision of targeting, protecting it from degradation, or controlling the rate of release. A wide range of inorganic materials can be used to achieve these goals. This chapter will review the key recent developments in this field, with a focus on the four families of materials which have attracted most attention: 3D metal organic frameworks (MOFs), 3D mesoporous silicas (MSNs), 2D layered materials, and 0D inorganic nanoparticles (MNPs). These systems can have a very wide range of physical properties and chemical functionalities. For instance, MOFs and MSNs are porous and thus can offer high drug loadings, while stability varies significantly. MOFs often require functionalisation and protection from rapid degradation prior to cargo delivery, while MSNs and MNPs can persist in vivo. Layered materials also vary widely in stability but can result in effective targeting and extended release profiles. In all cases, the presence of an inorganic species in addition to the API can aid targeting and permit imaging to be performed concomitantly with drug delivery. Post-fabrication functionalisation is also possible, allowing further augmentation of tuning of properties. Inorganic systems thus have huge potential in drug delivery, but there are also very significant barriers to clinical adoption which need to be overcome to allow them to reach their full potential.