Here we report our investigations of the formation conditions and photophysical properties of complexes between luminescent semiconducting nanoparticles (quantum dots, QDs) and the photosensitizer chlorin e6, which is widely used for the photodynamic therapy. In our complexes, bovine serum albumin (BSA), the most abundant protein in blood serum, was used as a linker between QDs and chlorin e6 molecules. The influence of BSA on the optical properties of Ce6 and QDs in complexes was properly examined using spectral-luminescent methods. It was found that BSA passivated QD surface and substantially QD quantum yield of luminescence was increased. In addition, BSA prevented the aggregation of chlorin e6 molecules in complexes with QDs. We demonstrated that the use of BSA as a linker allows to create functional QD-chlorin e6 complexes with effective photoexcitation energy transfer from QDs to the molecules.
Photophysical properties of complexes of semiconductor quantum dots with conventional photosensitizers for photodynamic therapy (tetrapyrroles) were investigated. A luminescent study of complexes in aqueous solutions was performed using spectral- and time-resolved luminescence spectroscopy. It was found that increasing the photosensitizer relative concentration in complexes resulted in sharp drop of the nonradiative energy transfer efficiency and the quantum yield of the photosensitizer photoluminescence. This fact indicates that additional channels of nonradiative energy dissipation may take place in the complexes. Using complexes of Al(OH)-sulphophthalocyanine with CdSe/ZnS quantum dots in the aqueous solution as an typical example, we have demonstrated that new channels of the energy dissipation may arise due to aggregation of the photosensitizer molecules upon formation of the complexes with quantum dots. We also demonstrated that use of methods of complex formation preventing aggregation of photosensitizers allows to conserve the high energy transfer efficiency and quantum yield of the acceptor photoluminescence in complexes in wide range of the photosensitizer concentrations. We believe that our study allows obtaining new information about the physical mechanisms of nonradiative energy transfer in quantum dots-tetrapyrrole complexes perspective for photodynamic therapy.
New biocompatible complexes based on manganese-doped core/shell ZnS/ZnS quantum dots (ZnS:Mn<sup>2+</sup>/ZnS) and drug "Photoditazin" were formed and compared to traditional complexes with CdSe/ZnS quantum dots. Complexes with ZnS:Mn/ZnS quantum dots show some advantages in their photophysical properties. At the same time they demonstrate evident difference in their photophysical properties that may be associated with various location of trap states in places where drug molecule bounds with quantum dot.
We investigate electrical photoresponse of multilayer graphene decorated with CdSe/ZnS quantum dots. It was found that photoresponse of these hybrid structures depends on quantum dot photoluminescence quantum yield. We demonstrate in uence of external factors (light exposure and treatment with ammonia vapors) on photoluminescence quantum yield of quantum dots and electrical photoresponse of the hybrid structures.
In present study complexes between non-toxic ZnSe/ZnS quantum dots and chlorin e6 molecules that are widely used as photosensitizers in photodynamic therapy were formed. It was found that in aqueous solution cationic ZnSe/ZnS quantum dots and chlorin e6 formed stable complexes that exhibit efficient photoexcitation energy transfer from quantum dots to molecules. Spectroscopic methods were applied to evaluate the energy transfer efficiency. Stoichiometry of these complexes was studied. Additionally, the photodynamic therapy efficacy of the quantum dotchlorin e6 complexes was in vitro assessed against Ehrlich ascites carcinoma cancer cell line using a trypan blue assay. We found that complex offered an improved cancer cell photodynamic destruction effect as compared to that of free chlorin e6.