Crosslink-free Coating of MSNs Demonstrated at UNAM

Although the small sizes and large combined surface areas of nanoparticles make them promising agents for drug delivery, their clearance, uptake and targeting profiles may leave much to be desired. So is the case with mesoporous silica nanoparticles (MSNs for short) – their porous nature gives them an even larger volume to contain drugs or other therapeutic agents in, but a surface coat is often necessary to prevent their aggregation and increase their uptake by their target cells. This coat is often glued fast onto the nanoparticle through covalent crosslinks, the process to create which is costly, long and cumbersome – a non-covalent method of surface functionalization would be a welcome alternative. And UNAM’s Biomimetic Materials and Nanobiotechnology groups, headed by Drs. Mustafa Özgür Güler and Ayşe Begüm Tekinay, now propose a new method to provide that alternative.

Peptide amphiphiles combine the functional versatility of proteins with the synthetic potential of materials chemistry, and their self-assembling properties allow them to form highly complex and well-organized structures. This feature, often utilized to form fibrous or spherical networks, was put to another use by the group, who functionalized MSNs with octyl triethoxysilane (OTS) to direct the non-covalent assembly of a peptide layer onto the nanoparticles – interactions between hydrophobic and hydrophilic domains is the driving force behind self-assembly, and with a hydrophobic OTS coat, the MSNs could serve as an anchor point for the fatty acid residues of peptide amphiphile molecules. The functionalization process could be confirmed visually: OTS-coated MSNs normally aggregate into clusters, but an insulating layer of PAs turns them back into water-dispersible particles. Surface functionalization with a peptide amphiphile layer also increased the uptake of the MSNs, with 1.8-fold to 6.3-fold increases observed with various peptides and cell types.

In addition to preventing aggregation and increasing cellular uptake without covalent modification, peptide amphiphiles can also be designed to selectively target a specific type of receptor or cell, further extending the practical utility of mesoporous silica in biomedical applications. Melis Şardan, the lead author of the paper, is hopeful about the drug delivery applications of MSNs in particular, and suggests that the higher cellular uptake of the nanoparticles can be utilized to great effect in combined diagnostic-therapeutic approaches that further functionalize MSNs through the incorporation of magnetic nanoparticles.

The manuscript detailing the group’s findings has been published in the Journal of Materials Chemistry B and can be accessed at the following address:

http://pubs.rsc.org/en/Content/ArticleLanding/2014/TB/c4tb00037d

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