title: Micromotor-based lab-on-chip immunoassays.
abstract: Here we describe the first example of using self-propelled antibody-functionalized synthetic catalytic microengines for capturing and transporting target proteins between the different reservoirs of a lab-on-a-chip (LOC) device. A new catalytic polymer/Ni/Pt microtube engine, containing carboxy moieties on its mixed poly(3,4-ethylenedioxythiophene) (PEDOT)/COOH-PEDOT polymeric outermost layer, is further functionalized with the antibody receptor to selectively recognize and capture the target protein. The new motor-based microchip immunoassay operations are carried out without any bulk fluid flow, replacing the common washing steps in antibody-based protein bioassays with the active transport of the captured protein throughout the different reservoirs, where each step of the immunoassay takes place. A first microchip format involving an 'on-the-fly' double-antibody sandwich assay (DASA) is used for demonstrating the selective capture of the target protein, in the presence of excess of non-target proteins. A secondary antibody tagged with a polymeric-sphere tracer allows the direct visualization of the binding events. In a second approach the immuno-nanomotor captures and transports the microsphere-tagged antigen through a microchannel network. An anti-protein-A modified microengine is finally used to demonstrate the selective capture, transport and convenient label-free optical detection of a Staphylococcus aureus target bacteria (containing proteinA in its cell wall) in the presence of a large excess of non-target (Saccharomyces cerevisiae) cells. The resulting nanomotor-based microchip immunoassay offers considerable potential for diverse applications in clinical diagnostics, environmental and security monitoring fields.
authors.affiliation: Department of Nanoengineering, University of California-San Diego, La Jolla, CA 92093, USA.  josephwang@ucsd.edu.
authors.forename: Miguel
authors.initials: M
authors.lastname: García
authors.forename: Jahir
authors.initials: J
authors.lastname: Orozco
authors.forename: Maria
authors.initials: M
authors.lastname: Guix
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.forename: Sirilak
authors.initials: S
authors.lastname: Sattayasamitsathit
authors.forename: Alberto
authors.initials: A
authors.lastname: Escarpa
authors.forename: Arben
authors.initials: A
authors.lastname: Merkoçi
authors.forename: Joseph
authors.initials: J
authors.lastname: Wang
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation*; D007118:Immunoassay / Q000295:instrumentation*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D009038:Motion; D012371:Robotics / Q000295:instrumentation*