New Application Of Quantum Dot In Photodynamic Therapy

The thiol-capped CdTe quantum dots (QDs) with the average size of3.5nm were linked to Dopamines (DAs) forming DA-QD conjugates, with the characteristics of red-shifted photoluminescence (PL) peak and remarkably reduced PL lifetime. The QDs in the conjugates readily accept the electron from DAs when excited by the visible light, resulting in the oxidation of DAs and the production of singlet oxygen (1O2) with the yield comparable to that of sulfonated aluminum phthalocyanine (AlPcS), a popularly used photosensitizer. The DA-QD conjugate can quickly penetrate into human nasopharyngeal carcinoma (KB) cells and seriously destroy cells under the irradiation of visible lights, showing the potential to become a new kind of photosensitizers.The two-photon absorption cross sections (TPACS) of those matured and commonly used Photosensitizers (PSs) including the sulfonated aluminum phthalocyanine (AlPcS) are very low, so that those PSs are not suitable for two-photon photodynamic therapy (PDT). In this work, we prepared conjugates of quantum dots (QDs) and AlPcS by an electrostatic binding. The QDs have very high TPACS. The conjugated QDs were excited by the two-photon excitation (TPE) of an800nm femto-second (fs) laser and then transfered the energy to conjugated AlPcS via a way of fluorescence resonance energy transfer (FRET), with a high energy transfer efficiency of90%. The singlet oxygen (102) products were also produced by the QD-AlPcS under TPE via FRET mediated PDT. The FRET process of QD-AlPcS in both KB and Hela cells under TPE was confirmed. Moreover, the QD-AlPcS can destroy these cancer cells under the irradiation of an800nm unfocused fs laser beam via FRET mediated PDT, with a high killing efficiency which is comparable to that of common one-photon excitation (OPE) at visible wavelengths. These results highlight the potential of QD-AlPcS for TPE PDT with a near infrared wavelength.