Jun 26, 2009
Pluronic nanocapsule carries molecules into living cells
Researchers at the University of South Carolina, US, have developed a thermally responsive nanocapsule-mediated approach to deliver a significant amount of trehalose (342 Dalton) into eukaryotic mammalian cells (NIH 3T3 fibroblasts). The empty core-shell structured Pluronic-PEI (polyethylenimine) nanocapsule was synthesized using a modified emulsification-interfacial crosslinking solvent evaporation/dialysis method.
The nanocapsule's size changes with temperature. The group determined that the permeability to trehalose of the crossed-linked Pluronic-PEI nanocapsule wall is high at room temperature and very low at 37 °C.
To encapsulate the trehalose, the researchers soak the nanocapsules in an aqueous trehalose solution at room temperature and then freeze dry the particles to remove the water. After being heated and dissolved in a cell culture medium to incubate with cells at 37 °C, the small, positively charged, trehalose (blue dots) encapsulated nanocapsules (1) absorb onto the negatively charged cell plasma membrane and gradually become enwrapped in a membrane pit (2) that pinches off to form the early endosome (3), as shown schematically in the figure.
When the solution is cooled from 37 °C to room temperature, the nanocapsule expands (from ~150 nm in diameter to ~250 nm). The increase in volume breaks the endosome (4) and allows the nanocapsule to escape. Trehalose (dissolved in water sucked into the nanocapsule during volume expansion) is expelled from the nanocapsule into the cytosol when the temperature is returned to 37 °C (5).
Uptake and cell survival
A significant amount of trehalose (up to 0.3 M) was taken up by NIH 3T3 fibroblasts during a short incubation (40 min). The cells loaded with trehalose were found to survive well, proliferate normally, and function (collagen production) as usual.
The researchers are developing protocols to preserve important mammalian cells loaded with trehalose using the nanocapsule mediated approach at both cryogenic and ambient temperatures for future use as a therapeutic tool. They are also performing studies to deliver small but membrane-impermeable therapeutic molecules into cancer cells using the nanocapsule to enhance cancer treatment.
About the author
Wujie Zhang is a doctoral student in the Biothermostability Engineering Laboratory under the direction of Dr Xiaoming He in the Department of Mechanical Engineering and Biomedical Engineering Program at the University of South Carolina, Columbia, SC, US. Zhang worked on nanomaterial synthesis closely with Dr Jianhua Rong, who was a visiting scholar in Dr Qian Wang's Lab in the Department of Chemistry and Biochemistry and Nano Center at the University of South Carolina. The overall research objective of Dr Wang's lab is to develop hierarchically structured nanomaterials for studying cell–cell interactions and the cooperative response of cells to extracellular matrixes. Research in Dr He's lab has been focused on understanding and controlling the thermal stability of biologicals by micro/nano encapsulation and multiscale modeling. The goal is to stabilize important biologicals such as stem cells or destabilize unwanted biologicals, for example cancer cells, for the treatment of diseases.