698 Chem. Commun., 2011, 47, 698–700 This journal is c The Royal Society of Chemistry 2011 Controlled manipulation of multiple cells using catalytic microbotsw Samuel Sanchez,* a Alexander A. Solovev, a Sabine Schulze ab and Oliver G. Schmidt a Received 29th September 2010, Accepted 26th October 2010 DOI: 10.1039/c0cc04126b Self-propelled microjet engines (microbots) can transport multiple cells into specific locations in a fluid. The motion is externally controlled by a magnetic field which allows to selectively load, transport and deliver the cells. The development of useful micro- or nanomachines which could one day be manipulated inside the human body remains a challenging dream in nanotechnology and biomedicine. 1 Over the last five years, there has been substantial interest in the use of chemistry to propel tiny engines in a similar fashion that nature uses biochemistry to power biological motors. 2,3 Consequently, researchers have fabricated self-propelled nanomachines capable of performing useful tasks such as the transport of synthetic cargoes. 4,5 Artificial nanomachines that are able to swim along with biological matter such as cells have yet to be achieved. There are three main challenges that researchers try to conquer when engineering artificial nanomachines: (i) efficient self-propulsion, demonstrated by the catalytic breakdown of H 2 O 2 by Pt, 3,6 Ni 7,8 catalysts and catalase enzyme 9 contained in nanomotors; (ii) motion control, achieved by the incorporation of Ni or Fe segments and subsequently using external magnetic fields to orient the nanomotors 4,5,10,11 and; (iii) the development of useful task such as the transport of cargo like microparticles and nanoplates in a fluid. 4,5,12 To date, bimetallic nanomotors 4 and tubular microjet engines 5,12 have achieved these three requisites. However, the transport of a single spherical microparticle has been the last result accomplished by the nanomotors. 4 On the other hand, microjet engines (dubbed microbots) based on rolled-up nanotechnology have demonstrated the ability to transport multiple microobjects, not only colloidal microparticles but also metallic nanoplates. 5 Nonetheless, the transport of biological material such as cells by artificial nanomachines has not been achieved so far. Here we report on the pick-up, transport and release, of multiple neuronal CAD cells (cathecolaminergic cell line from the central nervous system) in a fluid by using catalytic microbots. Although ‘‘large’’ cells are loaded at the front end of the microbots, their motion is not totally halted. The microengines are self-propelled by the release of oxygen bubbles generated in the cavity of the microtubes (m-tubes) from the catalytic decomposition of peroxide used as fuel. Their motion is coordinated by an external magnetic field, which—once is turned rapidly—enables the release of the loaded cell at a desired target. To the best of our knowledge, this is the first report on the transportation of cells using any kind of artificial micro-nanomachine (nanomotor or micro- engine). The controlled transport of cells is of significant importance since it is clearly the next step towards the use of artificial nanomachines in future biomedical applications. Ti/Fe/Pt m-tubes were fabricated following the well- established rolled-up technique developed by our group. 13,14 First, silicon substrates were patterned with a photoresist layer of square structures of 50 mm  50 mm in size. Photoresist AR-P 3510 was spin-coated on Si wafers at 3500 rpm for 35 s, followed by a baking step and exposure to UV light with a Karl Suss MA-56 mask aligner. The subsequent structure was developed in an AR300-35 : H 2 O solution (1 : 1). The nanomembranes were then deposited by electron-beam (Ti and Fe) and magnetron sputtering (Pt), respectively. Thereafter, the structures were released from the substrate by removing the sacrificial layer (photoresist) with acetone, which causes the deposited nanomembranes to roll-up into m-tubes of 50 mm in length. A supercritical point drier is needed to avoid collapsing of the tube during drying due to the high surface tension of the etchant. On-demand and mass production of microbots is easily achieved with the rolled-up technique. In particular, the diameter of the m-tubes can be tailored by changing the thicknesses and the built-in strain of the deposited layers. 14,15 This versatility is of great interest concerning the transportation of cells with different diameters. For instance, the typical cell size varies from about 1 mm for some bacteria, 4 mm for yeast cells, 8 mm for red blood cells, 10 mm for animal cells or 100 mm for plant cells. Therefore, the fabrication of m-tubes with variable diameters is of significant importance in order to manipulate cells on-demand in an accurate manner. The murine CAD cells were grown in DMEM/F-12 medium (Dulbecco’s Modified Eagle Medium) supplemented with 10% FCS (Fetal Calf serum) and 1% penicillin/streptomycin. The cells were incubated in a humidified atmosphere with 5% CO 2 and were passaged every 3–4 days by trypsination and centrifugation at 4400 rpm for 5 min. After determination of cell numbers with a hemocytometer, CAD cells were plated at 10 5 cells per plate. A small amount of CAD cells (10 ml of B10 5 cells per ml) was suspended in 1.2 ml of the working solution containing the microbots and the chemical fuel to actuate them. The microbots are formed by a hollow tubular structure containing a thin Pt layer in their inside. When the m-tubes are immersed into a hydrogen peroxide solution, microbubbles are generated in one or more nucleation points of the Pt layer due a Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr 20, D-01069 Dresden, 01069, Germany. E-mail: s.sanchez@ifw-dresden.de; Fax: +49 351 4659 782; Tel: +49 351 4659 845 b Institute of Physiological Chemistry, Medical Faculty Carl Gustav Carus Dresden, University of Technology, Fiedlerstraße 42, D-01307 Dresden, Germany w Electronic supplementary information (ESI) available: Videos illustrating the microbot loading multiple CAD cells are available. COMMUNICATION www.rsc.org/chemcomm | ChemComm Downloaded by Freie Universitaet Berlin on 16 May 2011 Published on 19 November 2010 on http://pubs.rsc.org | doi:10.1039/C0CC04126B View Online