Lecture 19 Biosensors (continued).pdf

文档介绍：Molecular Principles of Biomaterials Spring 2003
Lecture 19: Biosensors (continued)
Last time: biosensor device classes
Gene array biosensors
Today: detection methods
Detection Elements
o Readout
ƒ Macroscopic fluorescence, diffraction, or interference
• what
ƒ Optical bar-coding4
• Example: quantum dot-loaded microsphere capture agents5
ƒ QDs show size-dependent luminescence
ƒ Narrow emission bands from mon excitation wavelength
ƒ Stable against photobleaching
ƒ Approach:
ƒ Load polymer microspheres with different amounts of several colors of
QDs to obtain a unique fluorescence signature
• 6 colors at 10 possible intensities allows for > 106 possible
‘codes’
ƒ Capture molecule on surface of beads grabs labeled analyte
(Han et al, 2001)
Lecture 19 – Biosensors
Molecular Principles of Biomaterials Spring 2003
Excitation of bar-code and target fluorochrome by same wavelength
Microscope-based
spectrophotometer for detection
of emission spectra from
individual beads
ƒ Optical absorption (colorimetric)
• what
ƒ Surface plasmon resonance and SPR arrays
• mercially later 1980’s (Cooper 2002)
• Typically, receptor is immobilized and free ligand is passed over sensor chip
ƒ Both ways possible, small ligands simply interfere with binding if immobilized
(Cooper 2002)
Lecture 19 – Biosensors
Molecular Principles of Biomaterials Spring 2003
Biacore sensor chips
Lecture 19 – Biosensors
Molecular Principles of Biomaterials Spring 2003
(Cooper 2002)
ƒ Optical fiber-based
• Single cell analysis optical fiber probes6
Advantages/disadvantages
ƒ Pros
o Fast measurements
o Sensitive
ƒ Cons
o
Cannot perform detection on turbid solutions
Electrochemical
Electrochemical readouts7
o Conductometric
o Measure changes in the conductance of the ponent arising between a pair of metal
electrodes d