Final Report: Engineered Magnetic Nanoparticles for Advanced Biosensor Signal Processing and Detection of Waterborne PathogensEPA Contract Number: EPD06083
Title: Engineered Magnetic Nanoparticles for Advanced Biosensor Signal Processing and Detection of Waterborne Pathogens
Investigators: Hartman, Nile
Small Business: nGimat Co.
EPA Contact: Manager, SBIR Program
Project Period: April 1, 2006 through June 30, 2007
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2006) Recipients Lists
Research Category: Nanotechnology , SBIR - Nanotechnology , Small Business Innovation Research (SBIR)
This project sought to advance the ReliaSense™ integrated optic chip (IOC) sensor for detection/identification of waterborne bacterial and viral pathogens, and toxins. nGimat proposed the use of magnetic nanoparticles to enable an advanced signal processing scheme that enhances optical biosensor detection sensitivity through magnetic field-induced nanoscale displacements of tethered magnetic particles immobilized on the waveguide surface. The nanoparticle displacement is intended to induce a phase shift in the output of a waveguide interferometer that can be utilized to discriminate noise from the collected signal through signal processing. nGimat expects the technology to build on the base optical sensor technology and to be ultimately capable of real-time, direct detection (no labeling, additional chemistry steps or reagents) of multiple biomolecules (proteins, toxins, nucleic acids) in the femtomolar concentration range and pathogens (bacteria, viruses) at concentrations of < 100 organisms/mL.
Phase modulation of guided optical waves was successfully demonstrated during the course of this project. Superparamagnetic nanoparticles (MNP) embedded in a polymer bead were attached to the surface of nGimat’s ReliaSense™ integrated optic waveguide interferometric sensor chip. Using an oscillating magnetic field gradient, the displacement of the MNP beads could be continuously varied relative to the waveguide surface. Because of the overlap of the beads with the evanescent field associated with the guided wave, the phase velocity of the guided wave also varied directly with the relative displacement of the MNP beads and the waveguide surface. The output of the waveguide interferometer was, in turn, modulated at the same frequency as the oscillating magnetic field gradient. The success of this program was dependent on the development of an attachment chemistry providing a tether length that allowed the MNP bead to move on the order of subnanometer dimensions. Analysis indicates motion of only a few tenths of a nanometer are sufficient to modulate the phase velocity of a guided optical wave. These results represent the first known demonstration of phase modulation of a guided optical wave using magnetic field induced motion of super paramagnetic nanoparticles tethered to an optical waveguide surface. The observed modulation rates in the Hertz should ideally be in the tens of Hertz range, and it is likely this will be achievable with further improvements to the attachment chemistry and the methods used to generate a magnetic field gradient. While phase modulation was demonstrated, the goal of demonstrating detection of a biological agent was not realized due to added efforts associated with the attachment chemistry development. Primary accomplishments of the Phase II program include:
- Verified optical waveguiding with magnetic nanoparticles attached to a waveguide surface.
- Developed a surface attachment chemistry with variable tether length.
- Designed and demonstrated a permanent magnet-based system providing an oscillating strength magnetic field gradient.
- Demonstrated continuously variable phase modulation of a guided optical using super paramagnetic nanoparticle beads attached to an optical waveguide surface.
- Proved Angstrom level motion of an attached magnetic nanoparticles can modulate the phase of a guided optical wave.
Developed a waveguide design offering the required sensitivity for magnetic bead induced phase modulation of a guided optical wave.
This project has demonstrated phase modulation of guided optical light beams using magnetic nanoparticles tethered to an optical waveguide surface. Satisfactory guiding was observed with the nanoparticles in very close proximity to the waveguide surface, alleviating concerns regarding optical absorption. This demonstration establishes the basis for a signal processing technique capable of enhancing the detection sensitivity for biological agents through dramatic signal-to-noise ratio improvement.