title: Magnetic capture from blood rescues molecular motor function in diagnostic nanodevices.
abstract: BACKGROUND
  Introduction of effective point-of-care devices for use in medical diagnostics is part of strategies to combat accelerating health-care costs. Molecular motor driven nanodevices have unique potentials in this regard due to unprecedented level of miniaturization and independence of external pumps. However motor function has been found to be inhibited by body fluids.
  
  
  RESULTS
  We report here that a unique procedure, combining separation steps that rely on antibody-antigen interactions, magnetic forces applied to magnetic nanoparticles (MPs) and the specificity of the actomyosin bond, can circumvent the deleterious effects of body fluids (e.g. blood serum). The procedure encompasses the following steps: (i) capture of analyte molecules from serum by MP-antibody conjugates, (ii) pelleting of MP-antibody-analyte complexes, using a magnetic field, followed by exchange of serum for optimized biological buffer, (iii) mixing of MP-antibody-analyte complexes with actin filaments conjugated with same polyclonal antibodies as the magnetic nanoparticles. This causes complex formation: MP-antibody-analyte-antibody-actin, and magnetic separation is used to enrich the complexes. Finally (iv) the complexes are introduced into a nanodevice for specific binding via actin filaments to surface adsorbed molecular motors (heavy meromyosin). The number of actin filaments bound to the motors in the latter step was significantly increased above the control value if protein analyte (50-60 nM) was present in serum (in step i) suggesting appreciable formation and enrichment of the MP-antibody-analyte-antibody-actin complexes. Furthermore, addition of ATP demonstrated maintained heavy meromyosin driven propulsion of actin filaments showing that the serum induced inhibition was alleviated. Detailed analysis of the procedure i-iv, using fluorescence microscopy and spectroscopy identified main targets for future optimization.
  
  
  CONCLUSIONS
  The results demonstrate a promising approach for capturing analytes from serum for subsequent motor driven separation/detection. Indeed, the observed increase in actin filament number, in itself, signals the presence of analyte at clinically relevant nM concentration without the need for further motor driven concentration. Our analysis suggests that exchange of polyclonal for monoclonal antibodies would be a critical improvement, opening for a first clinically useful molecular motor driven lab-on-a-chip device.
authors: School of Natural Sciences, Linnaeus University, Kalmar SE-391 82, Sweden.
authors: Saroj
authors: S
authors: Kumar
authors: Lasse
authors: L
authors: Ten Siethoff
authors: Malin
authors: M
authors: Persson
authors: Nuria
authors: N
authors: Albet-Torres
authors: Alf
authors: A
authors: Månsson
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D019719:Diagnostic Equipment; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D008280:Magnetics / Q000295:instrumentation*; D020409:Molecular Motor Proteins / Q000378:metabolism*; D015879:Myosin Subfragments / Q000378:metabolism; D036103:Nanotechnology / Q000295:instrumentation*; D011817:Rabbits; D044967:Serum / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D007074:Immunoglobulin G; D020409:Molecular Motor Proteins; D015879:Myosin Subfragments; D000205:Actomyosin
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