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In this study, ZnO samples were synthesized using zinc acetate and urea with a method containing sonication, sol-gel transition and calcination steps. Urea to zinc acetate mole ratio values were changed as 0, 0.5, 1, and 2 and corresponding calcined samples were denoted as UZ-0, UZ-0.5, UZ-1, and UZ-2, respectively. Scanning electron microscopy (SEM) images indicated globular and rod-like structures. Aspect ratios of the nanorods increased as urea to zinc acetate ratio increased from 0 to 1 whereas nanoparticles with sizes of 70 ± 20 nm were observed for UZ-2 sample. Brunauer, Emmett and Teller (BET) surface area values of the samples varied between 9 and 25 m2/g and increased as initial urea amount increased. Band gap energies of the samples ranged between 3.24 and 3.29 eV. Four major peaks at about 400, 420, 480 and 530 nm with different intensities were observed in the photoluminescence (PL) spectra of the samples. All the samples removed rhodamine B by both adsorption and photodegradation. The highest visible light induced photodegradation rate was exhibited by UZ-2 sample having the highest surface area and it is attributed to superior charge separation properties of this sample under visible light. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to develop a doxorubicin (DOX) carrier system based on a PEGylated TAT-derived cell penetrating peptide (G2RQR3QR3G2S) and to investigate drug release, self-assembly and stability properties of the carrier system. In the preparation of the drug delivery system, denoted as mPEG-peptide-oxime-DOX, methoxypolyethylene glycol (mPEG) with Mn=1900 Da was used. DOX was attached to the mPEG-peptide carrier system via acid cleavable oxime bond. Control drug delivery system, lack of the peptide (mPEG-oxime-DOX) was also synthesized to assess the effect of the peptide on the physicochemical and DOX release properties of the carrier system. mPEG-oxime-DOX exhibited a pH programmed DOX release with respective % DOX release values of ~68% and ~28% at pH 5.0 and at pH 7.4 at the end of 54 h. For the mPEG-peptide-oxime-DOX, on the other hand, quite low DOX release (~10-15 %) was observed for both pH values suggesting possible interactions between DOX and the peptide. Initial median size value (D50) of the mPEG-oxime-DOX was measured as ~24 nm, independent of pH. However, for the mPEG-peptide-oxime-DOX, quite lower D50 values (~3 nm and ~6 nm at pH 5.0 and pH 7.4, respectively) were obtained due to the repulsions between the arginines in the peptide sequence. Sizes of both drug delivery systems, tended to increase upon incubation at physiological conditions for 1 day suggesting that longer PEG chains should be used to enhance the stability of the mPEG-peptide-oxime-DOX and mPEG-oxime- DOX systems. [ABSTRACT FROM AUTHOR]

A drug delivery system (DDS) containing a cathepsin B degradable sequence and pH-responsive histidines was prepared by methoxypolyethylene glycol and peptide conjugation. Doxorubicin was attached to the carrier system using amide linkage to give the final form of the DDS, denoted as mPEG-AT3-DOX. mPEG-AT3-DOX exhibited a bimodal size distribution at about 15 and 30 nm independent of pH, whereas the size of the control DDS containing no peptide sequence, mPEG-DOX, was measured as ~ 15-20 nm. At the end of 72 h, % doxorubicin release from both of the DDSs was observed to be below 8.5 ± 3% in the absence of cathepsin B, and it increased to 17 ± 2% in the presence of cathepsin B for mPEG-AT3-DOX. Complete degradation of AT3 peptide within 3 h upon incubation with cathepsin B suggests that lower than expected doxorubicin release is likely due to the aggregation tendency of mPEG-AT3-DOX. Absolute IC50 values indicated that the cytotoxicity trend of the samples is in the order of free DOX ≤ mPEG-AT3-DOX >mPEG-DOX. Considering these results, PEG-peptide-doxorubicin conjugates can be promising candidates in cancer therapy if they are designed to have more pronounced pH-responsive behavior to increase the drug release rate. [ABSTRACT FROM AUTHOR]

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