Intracellular Delivery of Nanoparticles via Microelectrophoresis Technique: Feasibility demonstration

Nanoparticles with desirable properties and functions have been actively developed for various bio-medical research, such as in vivo and in vitro sensors, imaging agents and delivery vehicles of therapeutics. However, an effective method to deliver nanoparticles into the intracellular environment is a major challenge and critical to many biological studies. Current techniques, such as intracellular uptake, electroporation and microinjection, each have their own set of benefits and associated limitations (e.g., aggregation and endosomal degradation of nanoparticles, high cell mortality and low throughput). Here, the well-established microelectrophoresis technique is applied for the first time to deliver nanoparticles into target cells, which overcomes some of these delivery difficulties. Semiconductive quantum dots, with average hydrodynamic diameter of 24.4 nm, have been successfully ejected via small electrical currents (-0.2 nA) through fine-tipped glass micropipettes as an example, into living human embryonic kidney cells (roughly 20 - 30m in length). As proposed by previous studies, micropipettes were fabricated to have an average tip inner diameter of 206 nm for ejection but less than 500 nm to minimize the cell membrane damage and cell distortion. In addition, delivered quantum dots were found to stay monodispersed within the cells for approximately one hour. We believe that microelectrophoresis technique may serve as a simple and general strategy for delivering a variety of nanoparticles intracellularly in various biological systems.