Mesoporous silica is of current interest for therapeutic applications, such as drug delivery, because of its small size and internal pore structure into which small molecules can be adsorbed. However, while the toxicity literature is extensive for micron-sized crystalline silica due to occupational health concerns, there is relatively little information available for mesoporous silica. Here, solid silica and mesoporous silica particles are characterized using SEM, DLS, XRD, and BET analysis; and their toxicities assessed using a modified MTT assay for cell viability and DPPP assay for lipid peroxidation. On a mass basis, mesoporous silica reduces cell viability from 82 ± 8% to 73 ± 16% compared to solid silica, likely due to the decreased density and therefore increased number of particles and particle surface area. This modest increase in toxicity, compared to the dramatic 600X increase in total surface area for mesoporous silica, from both pore and particle surfaces, suggests that the toxicity mechanism depends on the surface area available to the cell and not the total surface area. DPPP results support this conclusion and indicate that membrane lipid peroxidation is involved.

Applications of self-assembled monolayers (SAMs) formed by the adsorption of alkanethiols onto gold surfaces have had a widespread growth in adhesion investigations, interfacial interaction investigations and other interfacial phenomena in recent years. As computational modelling showed that modified surfaces can segregate compliant microspheres, a microfluidic flow cell was designed to roll polymeric microcapsules on surfaces with different chemistries, in order to obtain experimental data to validate previous results. Particle image velocimetry showed that rolling speed of microcapsules is affected by surface chemistry. The velocity of vesicles rolling on thiol surfaces with positive of negative charged head groups was significantly lower than vesicles rolling on thiol surfaces with a hydrocarbon chain head group and pure gold surface respectively. Since fabrication of patterned SAMs with different thiol surfaces is possible through oxidation by UV light, our results point to a facile method for carrying out a continuous separation process.

Emulsions are usually metastable systems of two non-miscible phases stabilized by surface active species like surfactant molecules. Emulsions stabilized by solid colloidal particles adsorbed at the interface (Pickering emulsions) offer some competitive advantages with respect to classical emulsions. Most studies published up to now concern emulsions stabilized by inorganic (metallic oxides, exfoliated clays, carbonates and phosphates) or polymeric particles while biomass derived alternatives have only been explored to a limited extent. For the first time, we report the stabilization of emulsions by unmodified cellulose nanocrystals [1, 2] . Cellulose nanocrystals were produced from bacterial cellulose and used to form Pickering emulsions. We demonstrate by SEM that the nanocrystals are adsorbed at the oil/water interface. We also study the size distribution of the droplets that was found to range around 4μm in diameter with very narrow dispersity. The stability of the emulsions was also investigated. The fabrication of new armored microparticles exposing cellulose acicular nanocrystals from cellulose nanocrystals opens opportunities to build materials from low cost and environmental friendly resource.

To develop new functional fluorescence probe based on semiconductor nanoparticles, such as quantum dots (QD)s, we investigated polymer particle embedding QDs and covered with artificial cell membrane-biointerface. These nanoparticles were prepared by assembling 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer as a platform and biomolecules immobilized on the surface of the nanoparticles. The fluorescence property of QDs remained after embedding in the polymer nanoparticles. The MPC polymer surface showed high resistance to non-specific cellular uptake due to the phosphorylcholine groups in the side chain. On the other hand, when cell-penetration oligopeptide, octaarginine was immobilized on the surface, they could permeate the membrane of cells effectively and good fluorescence based on QDs could be observed. Cytotoxicity and inflammation reaction was not produced by these nanoparticles even after immobilization of octapeptide. In conclusion, we could obtain stable fluorescence polymer nanoparticles covered with artificial cell membrane, which are useful as an excellent bioimaging probe and as a novel evaluation tool for biomolecular function in the target cells.