ENVIRONMENTAL BIOTECHNOLOGY CRC Quantum Dots in Microbiology Quantum Dots in Microbiology Raquel Ibáñez and Peter Bergquist 21 February 2005

Environmental Biotechnology CRC 2 Physical Characterisation Physical Characterisation Absortion spectra Emission spectra Conventional Dyes Quantum Dots Narrow Absorption Asymmetric emission spectra Broad Absorption Narrow and symmetric emission spectra

Environmental Biotechnology CRC 3 Physical disposition of Quantum Dots and probes

Environmental Biotechnology CRC 4 Quantitative method: Qdots versus conventional fluors 5’-Biotin-AAAAAAAAAA-FITC 3’ FL1-H Control 1x 2x 3x 4x 5x 6x 7x 10x Histogram Red Qdot 655nm biotin modified Histogram Control 1x 2x 3x 4x 5x FL3-H 6x 7x7x 10x

Environmental Biotechnology CRC 5 BD LSR I : Results QDots dilution series Excitation: Blue Light ( 488nm ) Detector: FL3 ( 670nm Detector: FL3 ( 670nm ) Excitation: UV Light (325nm) Detector FL3: filter modified to detect 660

Environmental Biotechnology CRC 6 Results The minimum concentration to detect QDots using 488nm excitation (blue light) is 0.02pmol The minimum concentration to detect the same samples using 325nm excitation (UV light) is less than 0.001pmol QDots are approximately 10 times brighter under UV light excitation QDots are approx 20 times brighter than FITC

Environmental Biotechnology CRC 7 Physical Disposition of Quantum Dots A. Barcodes: QDs embedded into beads B. Using QDs as a target C. QDs Magnetic beads FITC Specific oligo Universal oligo Dynabead QD Specific oligo Dynabead QD/FITC Universal oligo Specific oligo

Environmental Biotechnology CRC 8Conclusions  QDs are brighter under higher energy excitation sources (UV light)  QDs are brighter than organic dyes under lower energy excitation sources (blue light)  QDs are more photostable than organic dyes  QDs bind successfully to biomolecules  New alternatives have to be investigate for using QDs for molecular analysis  QDs embedded into polymer microbeads  QDs need invasive methods to penetrate the bacterial membranes  QDs conjugated to antibodies to target the bacteria membrane Conclusions