DNA Hybridization Detection using Fluorescent Zinc Selenide Quantum Dots
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0951-E03-01
DNA Hybridization Detection using Fluorescent Zinc Selenide Quantum Dots Jun Wang1, Pedro Lei2, Stelios Andreadis2, Tracy Heckler1, Bing Mei1, Qi (Grace) Qiu1, and T J Mountziaris1 1 Chemical Engineering, University of Massachusetts, Amherst, MA, 01003 2 Chemical and Biological Engineering, University at Buffalo - SUNY, Buffalo, NY, 14260
ABSTRACT This work focuses on the development of biological analysis tools using zinc selenide quantum dots (ZnSe QDs). Conjugating water-dispersible ZnSe QDs with oligonucleotides of increasing length was found to increase their photoluminescence (PL) intensity monotonically up to a certain length. Varying the sequence of the oligonucleotide without changing its length does not produce any measurable PL intensity change. The stability of QDs in water was significantly enhanced after conjugation with oligonucleotides. DNA hybridization was studied using QDs functionalized with complementary oligonucleotides. Hybridization of complementary QDoligonucleotide complexes causes significant PL intensity amplification and a measurable red shift of the PL emission peak. The QD-oligo complexes are very stable in water under ambient dark conditions. Finally, a size-dependent optimal dilution of free QDs was discovered, corresponding to an optimal inter-QD-spacing that results in the highest PL emission intensity from as-prepared QD dispersions. Ongoing experiments in our laboratory aim to develop multiplexed DNA probes and immunoassays by employing luminescent QDs emitting at different wavelengths. INTRODUCTION Semiconductor nanocrystals or quantum dots (QDs) are small crystalline grains of a few hundred to a few thousand atoms with diameters less than 10 nanometers. They have recently attracted significant attention arising from interest in understanding the transition of material properties from bulk to molecular-like clusters and from numerous potential applications[1,2]. QDs exhibit size-dependent properties, including size-dependent luminescence, and both their absorption onset and emission peak shift to smaller wavelengths with decreasing size. In addition, QDs have symmetric and narrow emission peaks and their emission spectrum does not change with the excitation frequency because of their continuous absorption spectrum [3]. Due to their unique properties, QDs have potential applications in many fields, such as display devices, microelectronics, lasers, and solar cells, etc. However, the most promising applications of luminescent QDs thus far are in the field of clinical diagnostics, where they can be used as luminescent tags for biomolecules [4,5]. Traditional tagging of biomolecules that employs organic fluorophores has significant limitations when compared to tagging using QDs [6,7]. Organic fluorophores tend to have narrow excitation spectra, and often exhibit broad emission spectra with red tailing. This prevents the simultaneous quantitative evaluation of multiple probes present in the same sample, due to significant spectral overlap. It also makes difficult to obs
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