Biomedical Engineering Reference
In-Depth Information
15
Photoelectric Biosensors: Fundamentals and
Innovative Designs
Felix T. Hong
CONTENTS
15.1 Introduction ....................................................................................................................385
15.2 AC and DC Photoelectric Effects ..................................................................................387
15.3 Electron as a Charge Carrier: An Artificial Light-Driven Electron Pump ..............388
15.4 Proton as a Charge Carrier: Bacteriorhodopsin Membranes ..................................394
15.4.1 Mechanistic Aspects of Signal Generation ....................................................395
15.4.2 Component Analysis ........................................................................................397
15.4.3 DC Photoelectric Effect: The Null-Current Method ....................................404
15.5 Generalization to Other Photoelectric Systems ..........................................................412
15.6 Prototype Molecular Sensors Based on Photoelectric Effects ..................................418
15.6.1 Two Ways of Configuring Photoelectric Sensors ........................................418
15.6.2 A Light Sensor Based on the AC Photoelectric Effect ................................418
15.6.3 Specific Ion Sensors Based on the DC Photoelectric Effect ........................420
15.7 Bioelectronic Interfacing ................................................................................................421
15.8 Discussions and Concluding Remarks ........................................................................423
Acknowledgments ....................................................................................................................429
References ....................................................................................................................................429
15.1
Introduction
The molecular machines for vision and for photosynthesis are Nature's optoelectronic
devices. Both devices comprise a membrane with two planar layers of phospholipid mol-
ecules (lipid bilayers) in which oriented light-sensitive molecules are embedded. The
photosynthetic membrane and the visual membrane serve two radically different biolog-
ical functions: the former converts light energy into electrochemical energy for the pur-
pose of sustaining life (photon energy converter) whereas the latter detects light signals
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