A pair of 鈥渕icro tweezers鈥� that use an electric field to gently manipulate biological cells have been developed by US researchers. The tweezers cause less stress than conventional manipulation methods and could one day be used to manoeuvre nanoscale electronic components too.
The tweezers are made from a glass rod tapered to a tip measuring 3 microns across, with metal electrodes on either side. Running a current across the electrodes creates an electric field near the tip, which can be used to grab hold of and control cells, providing the voltage and frequency are tuned correctly.
鈥淭hey are gentler than mechanical methods,鈥� explains Tom Hunt, who developed the tweezers and is a member of Robert Westervelt鈥檚 nanoengineering research group at Harvard University in Massachusetts, US. 鈥淲ith our technology you don鈥檛 need to get so close to start with either,鈥� he told 快猫短视频. 鈥淥nce you switch them on, the cell is drawn to the tip.鈥�
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The tweezers exert a force on cells because they are polarised by the electric field more than the surrounding fluid. After grabbing a cell, the operator must lower the strength of the field to avoid attracting any other cells.
Precious eggs
Hunt tested the tweezers by attaching them to a mechanical micro-manipulator so that its movements could be controlled. He then looked through a microscope as he manipulated yeast cells. The cells were able to divide normally while held in the field, showing that the tweezers have no adverse effects.
Systems that sort cells using an electric field already exist, but Hunt realised the same effect could be used to manipulate individual cells. He says the tweezers could be particularly useful for fertility treatment, allowing an egg cell to be gently held so that a human sperm can be injected into it.
Currently, egg cells are held using a pipette that applies suction. 鈥淭hat exerts a significant force and puts quite a lot of stress on the egg鈥檚 membrane and internal structures,鈥� Hunt says. 鈥淓ven an expert can lose a good proportion of eggs, and they鈥檙e precious things.鈥�
Shrinking distances
Nicholas Green, who designs cell sorting devices at Southampton University, UK, believes the tweezers could have a range of biological uses. 鈥淚t is better than physical manipulation because cells are not adapted to be handled physically,鈥� he told 快猫短视频. 鈥淎 lot of standard techniques involve touching cells and that physical stress can cause shock and cell death.鈥�
Shrinking the distance between the tweezers鈥� electrodes further still could make them suitable for use in other areas. 鈥淭hey might be a good way to position nanowires,鈥� says Hunt, who has already developed smaller tweezers that can grasp nanowires just 50 nanometres wide.
鈥淐urrently, researchers use drops of fluid containing nanowires and hope they end up in the right place,鈥� he says. 鈥淯sing the tweezers and an atomic force microscope, it might be possible to pick and place them where you want.鈥�
