Biophotonics - Imaging: X-ray, OCT, polarimetry, DOT, TIRF, photon migration, endoscopy, confocal microscopy, multiphoton microscopy, multispectral imaging - Biosensing: IR spectroscopy, fluorescence, luminescence, Raman scattering, surface plasmon resonance, polarimetry, evanescent wave-based detection - Laser-tissue interaction: ablation, coagulation, cutting, welding, PDT, optical trapping Biophotonics?? Fusion technologies of photonics and biotechnology and biomedical engineering enabled by information technology Advantages of the lightwave technology in biomedical engineering - Non-invasive/minimally invasive techniques (detection based on fiber-optics) - Real-time feedback for clinical diagnostics and visual guidance for surgery - High sensitivity and specificity: singlemoleculesensing, molecular tagging - Wide range of spatial scales that can be sampled: «m ~ cm - Abundance of intrinsic (hemoglobin) and extrinsic (fluorescent protein) chromophores
Bio-imaging Optical imaging for early detection and monitoring the progression of a disease Benefits of optical imaging: Non-invasive or minimally invasive No harmful radioactivity (vs. radioisotope imaging) Rapid real-time measurements (vs. MRI) High spatial resolution (vs. ultrasound) High sensitivity (vs. x-ray imaging) Portability and compactness In vitro, in vivo, andex vivo specimens References http://microscope.fsu.edu/primer/ http://bama.ua.edu/~hsmithso/class/bsc_656/websites/light.html
In vivo optical imaging?? Absorption of an electromagnetic wave Tissue absorption spectrum Extinction = Absorption + Scattering Absorption of an electromagnetic wave Scattering of an electromagnetic wave Rayleigh scattering elastic >> d, Mie scattering elastic Raman scattering inelastic (Stokes, anti-stokes) Scattering in tissues
Fluorescence, fluorophores, etc. Fluorescence Property of some atoms or molecules to absorb light of a particular wavelength and re-emit later at a longer wavelength. The interval between absorption and reemission: fluorescence lifetime Time Domain, Frequency Domain approaches Advantages: Proteins, dyes, and QDs available NIR available (ICG) : deeper tissue penetration Can be used for human Disadvantage: Auto-fluorescence, background noise Excitation & emission spectral overlap Photobleaching, phototoxicity Fluorescence: molecular fluorescence probes Green Fluorescent Protein (GFP) (1) Discovered in the jellyfish, Aequorea victoria, and adapted for transgenic and viral use (purified in 1962; GFP gene cloned in 1992). GFP allows targeted expression of a fluorescent marker that can be visualized in live cells. Weissleder, Nature Rev. Cancer, 2002
Green Fluorescent Protein (GFP) (2) Green fluorescent bunny (born in 2000 in France). When illuminated with blue light (488 nm), she glows with a bright green light (509 nm). Excitation Emission Transgenic Pets Drosophila Green Fluorescent Protein (GFP) (3) Transgenic Pets C. elegans
Bio-sensing: Gene Sequencing The fluorescently labeled fragments that migrate through gel are excited, which sends out light of a distinct color. The light is collected and focused by lenses into a spectrograph. Based on the wavelength, the spectrograph separates the light across a CCD camera. Each base has its own color, so the sequencer can detect the order of the bases in the sequenced gene. Bio-sensing: Flow Cytometry, Fluorescence Activated Cell Sorting (FACS) Bio-sensing: DNA Chip, Gene chip Microarray technology evolved from Southern Blotting, where fragmented DNA is attached to a substrate and then probed with a known gene or fragment. Bio-imaging: Fluorescence Correlation Spectroscopy (FCS) In a system where particles only undergo translational diffusion, fluctuations caused by diffusion of molecules depend on the size. Rapidly diffusing small molecules produce rapid intensity fluctuations. In contrast, large molecules and biopolymers (proteins and protein bound ligands) exhibit slowly fluctuating patterns of bursts of fluorescence.
Bio-imaging: Fluorescence Correlation Spectroscopy (FCS) Surface Plasmon Resonance (SPR): Concept E. Kretschmann, Z. Phys. 1971 Rothenhäusler et al., Nature 1988 Wilson, Science 2002 Surface Plasmon Resonance (SPR): Concept E. Kretschmann, Z. Phys. 1971 Rothenhäusler et al., Nature 1988 Wilson, Science 2002 Label-free Bio-sensing Using SPR DNA chip (1) (2) (3) (1) Bare Gold (2) Single stranded DNA immobilized Angle (3) Hybridized with the complementary strand Protein chip Cell/tissue chip http://www.tissue-array.com
Market Share of Worldwide Medical Sensor Major SPR Biosensor Companies (1) Major Biosensor Companies Major SPR Biosensor Companies (2)
Recent SPR Biosensors BiaCore (Sweden) BiaCore Sensor Chip Texas Instruments (U.S.) Spreeta
GWC Technologies (U.S.) HTS Biosystems (U.S.) SPR Imager Thickness sensitivity : 1 Å Scanning method : Detector rotating stage Spectral range : 600-1100 nm Incident Angle range : 40-70 deg (for different prism) High sensitivity Near IR CCD detector K-MAC (Korea) Fiber-based SPR RSlavik et alsensors and Actuators B
Micro-ring resonator biosensor Micro-ring resonator biosensor Bio-sensing: Pulse Oximetry (1) SO A B OD OD SO A B OD OD Nonin Medical
Bio-sensing: Pulse Oximetry (2) If Only
Bio-sensing: Pulse Oximetry (3) Implantable Cardioverter Defibrillator (ICD) Electrode ICD, data fusion. pulse oximetry, oximetry. Medtronic St. Jude Medical Guidant Bio-sensing: Fiber-Based Indicator-Mediated Fiber Optic Sensors - Evanescent wave - Fluorophores can be used to label antibodies. Bio-sensing: Glucose Monitoring Patch-type non-invasive NIRS Implantable NIRS SpectRx Animas Polarimetry based NIRS NIR Diagnostics Lifetrac Systems Retinal blood analyzer FoviOptics Various methods of optical analysis Conventional fluorescence imaging Phase contrast microscopy Dark-field microscopy Confocal microscopy Multiphoton microscopy Optical coherence tomography Total internal reflection fluorescence imaging Diffuse optical tomography Near-infrared spectroscopy Fluorescence resonance energy transfer Fluorescence lifetime imaging Fluorescence correlation spectroscopy Fluorescence activated cell sorting Surface plasmon resonance (imaging) Pulse oximetry Optical trapping Photodynamic therapy