The encapsulation and intracellular delivery of trehalose using a thermally responsive nanocapsule

The thermally responsive wall permeability of an empty core–shell structured Pluronic nanocapsule (together with its temperature dependent size and surface charge) was successfully utilized for encapsulation, intracellular delivery, and controlled release of trehalose, a highly hydrophilic small (MW = 342 D) molecule (a disaccharide of glucose) that is exceptional for long-term stabilization of biologicals (particularly at ambient temperatures). It was found that trehalose can be physically encapsulated in the nanocapsule using a soaking–freeze-drying–heating procedure. The nanocapsule is capable of physically withholding trehalose with negligible release in hours for cellular uptake at 37 °C when its wall permeability is low. A quick release of the encapsulated sugar can be achieved by thermally cycling the nanocapsule between 37 and 22 °C (or lower). A significant amount of trehalose (up to 0.3 M) can be delivered into NIH 3T3 fibroblasts by incubating the cells with the trehalose-encapsulated nanocapsules at 37 °C for 40 min. Moreover, cytotoxicity of the nanocapsule for the purpose of intracellular delivery of trehalose was found to be negligible. Altogether, the thermally responsive nanocapsule is effective for intracellular delivery of trehalose, which is critical for the long-term stabilization of mammalian cells at ambient temperatures and the eventual success of modern cell-based medicine.