Electrostatic binding of nanoparticles to mesenchymal stem cells via high molecular weight polyelectrolyte chains.

Combining stem cell transplantation with nanoparticle-mediated delivery of drugs and pharmaceuticals is envisioned to be one of the next major developmental steps in regenerative medicine. However, a major challenge would be to keep nanoparticles co-localized with stem cells upon transplantation or transfusion in situ. Since nanoparticles are physically much smaller in size than cells and would not specifically bind to extracellular matrix, it is easier for them to disperse from the transplantation site via the blood circulation. Conjugating nanoparticles directly to the cell membrane can potentially interfere with cellular function by physically obstructing cell surface receptors from interacting with the extracellular matrix, various growth factors and cytokines and other cells. Moreover, drug-loaded nanoparticles may be internalized into the cytoplasm via endocytosis or phagocytosis, which may wreak damage on the cellular machinery, leading to impaired physiological function or cell death. A novel solution may be to utilize high molecular weight polyelectrolyte chains to electrostatically bind nanoparticles to cells. For this purpose, hyaluronan, poly-L-lysine and chitosan are of special interest, because these molecules are generally recognized to be biocompatible for application in various pharmaceutical and surgical products. This study investigated the use of these molecules to bind nanoparticles to mesenchymal stem cells (MSCs), and a novel technique of conjugating half the cell surface with nanoparticles through the use of polyelectrolyte chains was also developed. This would avoid blocking MSC interaction with cytokines, growth factors, extracellular matrix and other cells within the recipient tissue/organ upon delivery in situ.