Nanoengineered structures for holding and manipulating liposomes and cells

We describe the fabrication of nanoengineered holding pipets with concave s eating surfaces and fine pressure control. These pipets were shown to exhib it exceptional stability in capturing, transporting, and releasing single c ells and liposomes 1-12 mum in diameter, which opens previously inaccessibl e avenues of research. Three specific examples demonstrated the, utility an d versatility of this manipulation system. In the first, carboxyrhodaminie was selectively incorporated into individual cells by electroporation, afte r which nearly all the medium (hundreds of microliters) surrounding the doc ked and tagged cells was rapidly exchanged (in seconds) and the cells were subsequently probed by laser-induced fluorescence (LIF). In the second stud y, a single liposome containing carboxyrhodamine was transported to a dye-f ree solution using a transfer pipet, docked to a holding pipet, and held fi rmly during physical agitation and interrogation by LIF. In the third study , pairs of liposomes were positioned between two microelectrodes, held in c ontact, and selectively electrofused and the resulting liposomes undocked i ntact.