Double core Infrared (CdSeTe) / ZnS quantum dots conjugated to Papiloma virus antibodies
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Double core Infrared (CdSeTe) / ZnS quantum dots conjugated to Papiloma virus antibodies J.L. Casas Espinola1, T. V. Torchynska1, J. A. Jaramillo Gómez2, J. Douda2 and K. Gazarian3 ESFM– Instituto Politécnico Nacional, México D. F. 07738, México 2 UPIITA – Instituto Politécnico Nacional, México D. F. 07320, México 3 Instituto de Investigaciones Biomédicas, UNAM, México D.F. México 1
ABSTRACT The paper presents the photoluminescence (PL) study of the double core/shell infrared CdSeTe/ZnS quantum dots (QDs) in nonconjugated states and after the conjugation to the anti papiloma virus ( i) mouse anti-HPV 16-E7 or ii) mouse monoclonal [C1P5] to HPV16 E6 + HPV18 E6) antibodies. CdSeTe/ZnS QDs with infrared emission at nearly 800 nm (1.6 eV), have been investigated. PL spectra of nonconjugated QDs are characterized by one Gaussian shape PL band related to the exciton emission in CdSeTe cores. Raman scattering spectra have been studied with the aim to reveal the CdSeTe double core composition. The Raman scattering study has shown that the central part of the core in QDs has the composition CdSe0.5Te0.5 and the periphery part of the core has the composition CdSe0.7 Te0.3. PL spectra of bioconjugated QDs have changed: PL bands shift into the high energy and become asymmetric. The energy diagram of the double core/shell CdSeTe/ZnS QDs have been created for the nonconjugated QDs, which permits to explain the PL spectrum of nonconjugated QDs and its transformation at the bioconjugation to papiloma virus antibodies. It is shown that the PL spectrum transformation in bioconjugated QDs is promising for the study of the bioconjugation with specific antibodies and can be a powerful technique in biology and medicine. INTRODUCTION The application of II-VI core/shell QDs in biology and medicine is expected to produce major advances in molecular diagnostic [1], gene technology [2] and toxin detections [3]. Additionally, II-VI core/shell QDs are usually characterized by high PL quantum yield (up to 75%) and high resistance to photo- and metabolic degradation. Core/shell QDs of II-VI semiconductors as the luminescent markers have been investigated intensively during the last decade. The PL intensity in bioconjugated QDs decreased [4] or increased [5] owing to the energy exchange between QDs and biomolecules. The QD luminescence intensity depends on the concentration of attached bio-molecules, enabling QD application as a protein sensor [4, 5]. Unfortunately, the limits of protein detection are not sensitive enough. Thus, it is desirable to have additional spectroscopic confirmation of bioconjugation with a spectral shift of the QD emission or changing the PL band half width. Double core /shell CdSeTe QDs with IR emission (800 nm) are manufactured specially. This type of QDs is very interesting for the biological applications owing to the possibility of in vivo animal imaging, due to the lower absorption of IR light by animal tissues.
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EXPERIMENTAL DETAILS Commercially available double core/shell CdSeTe/ZnS QDs [6] covered by the am
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