Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

Abstract

The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

Materials for Immunotherapy

“…Though tremendous effort has been expended to use MSNs in immunotherapies, a lingering concern of silica nanoparticles is their poor degradability, accumulation, and potential toxicity. To abate these concerns, Khashab and co‐workers recently published an expansive review that covers the mechanisms driving degradation and the effect of dosages, material subtypes, and physical characteristics (e.g., particle shape, size, pore size, coating, and concentration) on degradation and clearance of MSNs that may pave a way to advance these materials into clinical practice as a material for immunotherapy …”

Organosilica Nanoparticles for Gemcitabine Monophosphate Delivery in Cancer Cells

“…These nanoparticles are prepared from polytrialkoxysilylated organic precursors, which are condensed in mild conditions using the sol‐gel procedure, without the presence of any silica source. Recent studies have shown the excellent biocompatibility of these nanoparticles . Of interest are their porous analogues, which have also been reviewed and are particularly suitable for theranostic applications and drug delivery .…”

Mesoporous Silica‐Based Materials with Bactericidal Properties

“…Silica‐based NP is hydrolytically unstable and is gradually converted to silicic acid or polysilicic acid, which are nontoxic and can safely be excreted/absorbed by the human body . Moreover, today it is possible to design highly biodegradable MS NPs .…”

“…Apart from the mentioned PCPs, surfactant removal method can also have significant impact on biodegradation of MS NPs . Similar to other biosafety parameters discussed above, excretion of MS NPs is highly dependent on their PCPs …”