Abstract
The application of fluorescent II-VI semiconductor quantum dots (QDs) as active photosensitizers in photodymanic inactivation (PDI) is still being evaluated. In the present study, we prepared 3 nm size CdTe QDs coated with mercaptosuccinic acid and conjugated them electrostatically with Zn(II) meso-tetrakis (N-ethyl-2-pyridinium-2-yl) porphyrin (ZnTE-2-PyP or ZnP), thus producing QDs-ZnP conjugates. We evaluated the capability of the systems, bare QDs and conjugates, to produce reactive oxygen species (ROS) and applied them in photodynamic inactivation in cultures of Candida albicans by irradiating the QDs and testing the hypothesis of a possible combined contribution of the PDI action. Tests of in vitro cytotoxicity and phototoxicity in fibroblasts were also performed in the presence and absence of light irradiation. The overall results showed an efficient ROS production for all tested systems and a low cytotoxicity (cell viability >90%) in the absence of radiation. Fibroblasts incubated with the QDs-ZnP and subjected to irradiation showed a higher cytotoxicity (cell viability <90%) depending on QD concentration compared to the bare groups. The PDI effects of bare CdTe QD on Candida albicans demonstrated a lower reduction of the cell viability (~1 log10) compared to bare ZnP which showed a high microbicidal activity (~3 log10) when photoactivated. The QD-ZnP conjugates also showed reduced photodynamic activity against C. albicans compared to bare ZnP and we suggest that the conjugation with QDs prevents the transmembrane cellular uptake of the ZnP molecules, reducing their photoactivity.
Highlights
Photodynamic therapy (PDT) is a relatively new type of therapy used for the treatment of tumorous cells/tissues and pathogenic microorganisms [1]
The results of indirect detection of reactive oxygen species show the potential of CdTe-mercaptosuccinic acid (MSA) quantum dots, ZnTE-2-PyP4+ porphyrin and their conjugates to generate ROS, the same behavior was not observed in the photodynamic inactivation tests involving Candida albicans
The CdTe quantum dots (QDs) showed no effect in reducing cell viability of this microorganism, even after photo-activation
Summary
Photodynamic therapy (PDT) is a relatively new type of therapy used for the treatment of tumorous cells/tissues and pathogenic microorganisms [1]. Since 2000, semiconductor QDs have been tested for ROS production and several advantages over the organic PS may be pointed out [2]: (i) a broader absorption band, enabling a more convenient excitation process; (ii) large extinction coefficients (from 105 to 106 M−1cm−1 at first excitonic band); (iii) narrow emission bands (bandwidth ~25–50 nm) with high quantum yield; (iv) a chemically active surface allowing therapeutic targeting and (v) a very high photostability This last optical property is especially appropriate for longer irradiation periods. This class of porphyrins presents emission bands in the red region allowing its PDI action in a deeper tissue profile
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
