Silica based nanoparticles toxicity

Based on well established silica chemistry, the surface of silica nanomaterials can be modified to introduce a variety of functionalizations [3, 11, 118]. The toxicity of surface-modified nanomaterials is largely determined by their surface functional groups. As an example, Kreuter reported that an apolipoprotein coating on silica nanoparticles aided their endocytosis in brain capillaries through the LDL-receptor [122-124]. Overall, silica nanomaterials are low-toxicity materials, although their toxicity can be altered by surface modifications. 

The toxicity is not only based on the amount or size of silica nanoparticles, but also on the cell line [95]. Cancer cell lines (A549, MKN-28) had a higher viability and resistance to silica nanoparticles than did normal cell lines (MRC-5, WS1 and CCD-966sk) [111]. Similarly, a previous study showed that A549 cells were more resistant to the treatment of silica nanoparticles than were macrophages [113]. 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

In conclusion, metal atom clusters such as Moe-based cluster units are promising light emitters for the preparation of luminescent silica nanoparticles, hi addition, a magnetic property can be added in a simple one-pot microemulsion process by the co-encapsulation of cluster units with y-Fe203 nanocrystals. Then, already luminescent and magnetic nanoparticles can also be rendered plasmonic by growing gold nanocrystals on their surface. Finally we showed that the silica matrix efficiently prevent plants or human cells from the toxicity of the clusters. 

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