An approach for batch preparation of liposome-functionalized microdevices is demonstrated for remotely controlled single-cell drug delivery. The liposome functionalized artificial bacterial flagella exhibit corkscrew swimming in 3D with micrometer positioning precision by applying an external rotating magnetic field. The devices are also capable of delivering water-soluble drugs to single cells in vitro.

Inspired by flagellar propulsion of bacterial such as E. coli, artificial bacterial flagella (ABFs) are magnetic swimming microrobots with helical shapes. ABFs can perform precise three-dimensional (3D) navigation in liquids under low-strength rotating magnetic fields making them attractive tools for drug delivery applications. Further functionalization of these swimming microrobots is necessary to optimize their performance of biomedical tasks. We report here for the first time the successful functionalization of titanium-coated ABFs with temperature-sensitive dipalmitoylphosphatidylcholine (DPPC) liposomes. Adsorption of intact liposomes on titanium was assessed using quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorption of fluorescently labeled liposomes on the surface of ABFs was confirmed with confocal laser scanning microscopy (CLSM) images. Functionalized ABFs (f-ABFs) can be loaded with both hydrophilic and hydrophobic drugs, and controlled drug release triggered by temperature. ABFs have a great potential to be used in targeted and controlled drug delivery and for in vivo sensing.

The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.