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Gelatin is a biocompatible, biodegradable, cheap, and nontoxic material, which is already used for pharmaceutical applications. Nanoparticles from gelatin (GNPs) are considered a promising delivery system for hydrophilic and macromolecular drugs. Mechanical properties of particles are recognized as an important parameter affecting drug carrier interaction with biological systems. GNPs offer the preparation of particles with different stiffness. GNPs were loaded with Fluorescein isothiocyanate-labeled 150 kDa dextran (FITC-dextran) yielding also different elastic properties. GNPs were visualized using atomic force microscopy (AFM), and force–distance curves from the center of the particles were evaluated for Young’s modulus calculation. The prepared GNPs have Young’s moduli from 4.12 MPa for soft to 9.8 MPa for stiff particles. Furthermore, cytokine release (IL-6 and TNF-α), cell viability, and cell uptake were determined on macrophage cell lines from mouse (RAW 264.7) and human (dTHP-1 cells, differentiated human monocytic THP-1 cells) origin for soft and stiff GNPs. Both particle types showed good cell compatibility and did not induce IL-6 and TNF-α release from RAW 264.7 and dTHP-1 cells. Stiffer GNPs were internalized into cells faster and to a larger extent.

Tuning the elastic properties of nanoparticles intended to be used in drug delivery is of great interest. To this end, different potential formulations are developed since the particle elasticity is affecting the in vitro and in vivo performance of the nanoparticles. Here we present a method to determine the elasticity of single gelatin nanoparticles (GNPs). Furthermore, we introduce the possibility of tuning the elastic properties of gelatin nanoparticles during their preparation through crosslinking time. Young’s moduli from 5.48 to 14.26 MPa have been obtained. Additionally, the possibility to measure the elasticity of single nanoparticles revealed the influence of loading a macromolecular model drug (FITC-dextran) on the mechanical properties, which decreased with raising amounts of loaded drug. Loaded particles were significantly softer, with Young’s moduli between 1.06 and 5.79 MPa for the same crosslinking time, than the blank GNPs. In contrast to this, lysozyme as a crosslinkable macromolecule did not influence the mechanical properties. A good in vitro cell compatibility was found investigating blank GNPs and FITC-dextran-loaded GNPs in viability assays with the cancer cell line A549 and the human primary cell-derived hAELVi cell line.

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Background: Microorganisms commonly employed in food industry, such as Lactobacillus plantarum and Saccharomyces cerevisiae, are also excellent natural nanotechnologists. They reduce selenite (SeO3 2- ) to form nanoparticles of red selenium (Se0 ) of exceptional quality and with interesting physical and (bio-)chemical properties. Objectives: The production of these nanoparticles has been studied in several relevant microorganisms to gain a better picture of the overall properties and quality of these particles, possible differences between producers, ease of production and, in particular, biological activity. Methods: Several common microorganisms, namely L. plantarum, S. cerevisiae and Escherichia coli have been cultured under standard conditions and 1mM concentrations of SeO3 2- have been converted to red particles of elemental selenium. These particles have been characterized extensively with respect to uniformity, size, shape, consistency and, in particular, biological activity against infectious microbes. Results: Highly uniform amorphous spherical particles of 100 nm to 200 nm in diameter could be produced by several microorganisms, including Lactobacillus. Although originating in bacteria and yeast, these particles exhibit antimicrobial activity when employed at concentrations of around 100 µM. This activity may in part be due to the inherent chemistry of selenium and /or of the protein coating of the particles. Interestingly, yeast also forms larger rod-like structures. These micro-needles with around 85 nm in diameter and up to 3 µm in length exhibit considerable antibacterial activity, possibly resulting from additional, physical interactions with cellular structures. Conclusion: Common microorganisms traditionally employed in the preparation of food produce nanoparticles of selenium which may be harvested and explored as natural antimicrobial agents or antioxidants. These particles provide a fine example of and lead for natural nanotechnology with biological activity and applications in food and food supplementation, medicine, agriculture and cosmetics.