Protein-Templated Biomimetic Silica Nanoparticles

Biomimetic silica particles can be synthesized as a nanosized material within minutes in a process mimicked from living organisms such as diatoms and sponges. In this work, we have studied the effect of bovine serum albumin (BSA) as a template to direct the synthesis of silica nanoparticles (NPs) with the potential to associate proteins on its surface. Our approach enables the formation of spheres with different physicochemical properties. Particles using BSA as a protein template were smaller (∼250–380 nm) and were more monodisperse than those lacking the proteic core (∼700–1000 nm) as seen by dynamic light scattering (DLS), scanning electron microscopy (SEM), and environmental scanning electron microscopy (ESEM) analysis. The absence of BSA during synthesis produced silica nanoparticles without any porosity that was detectable by nitrogen adsorption, whereas particles containing BSA developed porosity in the range of 4 to 5 nm which collapsed on the removal of BSA, thus producing smaller pores. These results were in accordance with the pore size calculated by high-resolution transmission electron microscopy (HTEM). The reproducibility of the BSA-templated nanoparticle properties was determined by analyzing four batches of independent synthesizing experiments that maintained their properties. The high positive superficial charge of the nanoparticles facilitated adsorption under mild conditions of a range of proteins from an <i>E. coli</i> extract and a commercial preparation of laccase from <i>Trametes versicolor</i>. All of the proteins were quantitatively desorbed. Experiments conducted showed the reusability of the particles as supports for the ionic adsorption of the biomolecules. The protein loading capacity of the BSA-based biomimetic particles was determined using laccase as 98.7 ± 6.6 mg·g^–1 of particles

Monosaccharides <i>versus</i> PEG-Functionalized NPs: Influence in the Cellular Uptake

Magnetic nanoparticles (NPs) hold great promise for biomedical applications. The core composition and small size of these particles produce superparamagnetic behavior, thus facilitating their use in magnetic resonance imaging and magnetically induced therapeutic hyperthermia. However, the development and control of safe <i>in vivo</i> applications for NPs call for the study of cell–NP interactions and cell viability. Furthermore, as for most biotechnological applications, it is desirable to prevent unspecific cell internalization of these particles. It is also crucial to understand how the surface composition of the NPs affects their internalization capacity. Here, through accurate control over unspecific protein adsorption, size distribution, grafting density, and an extensive physicochemical characterization, we correlated the cytotoxicity and cellular uptake mechanism of 6 nm magnetic NPs coated with several types and various densities of biomolecules, such as glucose, galactose, and poly(ethylene glycol). We found that the density of the grafted molecule was crucial to prevent unspecific uptake of NPs by Vero cells. Surprisingly, the glucose-coated NPs described here showed cellular uptake as a result of lipid raft instead of clathrin-mediated cellular internalization. Moreover, these glucose-functionalized NPs could be one of the first examples of NPs being endocytosed by caveolae that finally end up in the lysosomes. These results reinforce the use of simple carbohydrates as an alternative to PEG molecules for NPs functionalization when cellular uptake is required