(198q) Nanoharvesting and Nanodelivery of Bioactive Materials Using Engineered Silica Nanoparticles

Authors: 
Khan, M. A., University of Kentucky
Littleton, J. M., Naprogenix
Rankin, S. E., University of Kentucky
Knutson, B. L., University of Kentucky
Functionalized mesoporous silica nanoparticles (MSNP) possess surfaces that can be readily modified with specific functional groups for targeted binding interaction, in addition to ample pore space for loading of bioactive materials to be transported through cellular walls and membranes. Engineered silica nanoparticles (ESNPs) have been used extensively to deliver bio-active materials to target intracellular sites (nanodelivery). These materials have been fairly well explored as non-viral vectors for nucleic acid (DNA/RNA) delivery such as for siRNA induced interference. On the other hand, the reverse process guided by the same principles is called “nanoharvesting”, where valuable biomolecules are carried out and separated from living and functioning organisms using nanocarriers, which are designed to enter the cells and be expelled without inducing significant toxicity. This work focuses on the interaction (uptake/secretion) of ESNPs with eukaryotic cells especially lipid membrane penetration and intracellular localization to achieve a common ESNP design principles for both nanoharvesting and nanodelivery.

Nanoharvesting of polyphenolic flavonoids (a model class of therapeutics) from plant hairy roots is demonstrated using ESNPs (mean particle diameter ~170 nm) in which titania and amine functional groups are used as specific binding sites and a source of positive surface charge source, respectively. Intracellular uptake and localization of fluorescently tagged particles inside of hairy root cells are visualized by fluorescent microscopy, and isolation of therapeutics is confirmed by increased pharmacological activity of solutes recovered from the particles. After nanoharvesting, roots are found to be viable and capable of therapeutic re-synthesis, suggesting non-toxic nature of the designed ESNPs. The combination of both amines and titania binding sites is found to be necessary for uptake and metabolite binding, respectively.

In order to identify the underlying nanoparticle uptake/expulsion mechanism, the titania content of the plant roots was quantified as a function of time with exposure to nanoparticles. Fluorescence uptake and particle exchange experiments, in which fluorescently labeled ESNPs were taken up by plant cell cultures and then recovered in solution were also used to quantify ESNP uptake and recovery. Temperature (4 °C and 23 °C) dependent experiments showed similar uptake and recovery for both temperature indicating an energy independent process (inactive transport) for this particle size and surface functionalization.

While seemingly diverse, the highly tunable nature of ESNPs and their interactions with eukaryotic cells are broadly applicable, and enable facile nanodelivery based on a continuous uptake-expulsion mechanism.