Impacts of Cross-Linkers on Biological Effects of Mesoporous Silica Nanoparticles

Abstract

Chemically synthesized cross-linkers play decisive roles in variable cargos attached to nanoparticles (NPs). Previous studies reported that surface properties, such as the size, charge, and surface chemistry, are particularly important determinants influencing the biological fate and actions of NPs and cells. Recent studies also focused on the relationship of serum proteins with the surface properties of NPs (also called the protein corona), which is recognized as a key factor in determining the cytotoxicity and biodistribution. However, there is concern that cross-linkers conjugated onto NPs might induce undesirable biological effects. Cell responses induced by cross-linkers have not yet been precisely elucidated. Herein, using mesoporous silica nanoparticles (MSNs) the surfaces of which were separately conjugated with four popular heterobifunctional cross-linkers, i.e., N-[α-maleimidoacetoxy]succinimide ester (AMAS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), and maleimide poly(ethylene glycol) succinimidyl carboxymethyl ester (MAL-PEG-SCM), we investigated cross-linker-conjugated MSNs to determine whether they can cause cytotoxicity, or enhance reactive oxygen species (ROS) generation, nuclear factor (NF)-κB activation, and p-p38 or p21 protein expressions in RAW264.7 macrophage cells. Furthermore, we also separately conjugated two biomolecules containing TAT peptides and bovine serum albumin (BSA) as model systems to study their cell responses in detail. Finally, in vivo mice studies evaluated the biodistribution and blood assays (biochemistry and complete blood count) of PEG-derivative NPs, and results suggested that TAT peptides caused significant white blood cell (WBC)-related cell and platelet abnormalities, as well as liver and kidney dysfunction compared to BSA when conjugated onto MSNs. The results showed that attention to cross-linkers should be considered an issue in the surface modification of NPs. We anticipate that our results could be helpful in developing biosafety nanomaterials.

Protease-Responsive Targeted Delivery of Doxorubicin from Bilirubin-BSA-Capped Mesoporous Silica Nanoparticles against Colon Cancer

“…One study demonstrates that the BSA corona over the functionalized mesoporous silica nanoparticles has led to preferable cellular uptake with higher drug biodistrubution in the cancer cells . Further, there are reports which focus on the cytotoxicity information and biological effects of the cross-linkers, utilized over the surface of nanoparticles for bioconjugation . Herein, we introduce a heme byproduct bilirubin as a natural cross-linker which inherits brilliant biocompatibility and binding abilities with BSA.…”

Biological Effects of Nanoparticles on Macrophage Polarization in the Tumor Microenvironment

“…However, surface glycosylation of MSNs reduced the magnitude of the observed M1 polarization effects. In another study, macrophage treatment with TAT peptide-functionalized or bovine serum albumin-functionalized MSNs was found to increase ROS generation in macrophages compared to unmodified MSN treatments due to increased cellular uptake 65. Taken together, these reports indicate that increasing the size of silica particles can reduce their cellular uptake and minimize their M1 polarizing capabilities, and surface modifications to MSNs can further control their cellular uptake and modulate their polarization effects.…”

Understanding nanoparticle endocytosis to improve targeting strategies in nanomedicine

“…For example, several serum proteins (immunoglobulins, albumin and fibrinogen) can act as ligands for macrophage receptors. 295,296 Human monocytes (THP-1) were treated with the following cytokines to generate specific phenotypes: IFN-g/LPS for M1 and IL-4/ IL-13 for M2. Cellular uptake of SiO 2 NPs (50, 100, 200, 500 and 1000 nm) was investigated with or without the presence of human serum in the cell culture medium.…”