AVS 53rd International Symposium
    Biomaterial Interfaces Thursday Sessions
       Session BI-ThM

Invited Paper BI-ThM8
Semiconductor Quantum Dots for Bioimaging: Bandgap Engineering and Surface Engineering

Thursday, November 16, 2006, 10:20 am, Room 2014

Session: Plasmonic Methods and Sub-micron Structures for Biology and Medicine
Presenter: A.M. Smith, Georgia Institute of Technology and Emory University
Authors: A.M. Smith, Georgia Institute of Technology and Emory University
S. Nie, Georgia Institute of Technology and Emory University
Correspondent: Click to Email
The development of high-sensitivity and high-specificity probes beyond the intrinsic limitations of organic dyes and fluorescent proteins is of considerable interest to many areas of research, ranging from single-molecule biophysics to in-vivo medical imaging. Recent advances have shown that nanometer-sized semiconductor particles can be covalently linked with bioaffinity molecules such as peptides, antibodies, nucleic acids, and small-molecule inhibitors for use as fluorescent probes. In comparison with organic fluorophores, quantum dots (QDs) exhibit unique optical and electronic properties such as size- and composition-tunable fluorescence emission, large absorption coefficients, and significantly improved brightness and photostability. Despite their relatively large sizes (2-8 nm), bioconjugated QD probes behave like fluorescent proteins (4-6 nm), and do not suffer from serious kinetics or steric-hindrance problems. In this mesoscopic size range, QDs also have high surface area-to-volume ratios that can allow multivalent functionalization with many diagnostic (e.g., radioisotopic or magnetic) and therapeutic (e.g., anticancer) agents. We present recent developments in bioconjugated QD probes and their applications in ultrasensitive molecular and cellular imaging. We have generated new classes of QDs with tunable near-infrared emission (700-900 nm) for high-sensitivity imaging deep within living animals and in highly autofluorescent fixed tissue specimens. These QDs are brighter and have narrower emission bandwidths than comparable QDs reported in the literature, approaching the spectral properties of commonly used visible QDs. Using polymeric encapsulation, we have also engineered the surfaces of these and other QDs for ultra-high stability under a variety of harsh conditions, such as high salt buffers, acidic solutions, and oxidizing environments that would normally quench the QD fluorescence and potentially degrade the semiconductor core.