With the advancement of drug delivery systems based on mesoporous silica nanoparticles (MSNs), a simple and efficient method regulating the drug release kinetics is needed. We developed redox-responsive release systems with three levels of hindrance around the disulfide bond. A model drug (rhodamine B dye) was loaded into MSNs' mesoporous voids. The pore opening was capped with beta-cyclodextrin in order to prevent leakage of drug. Indeed, in absence of a reducing agent the systems exhibited little leakage, while the addition of dithiothreitol cleaved the disulfide bonds and enabled the release of cargo. The release rate and the amount of released dye were tuned by the level of hindrance around disulfide bonds, with the increased hindrance causing a decrease in the release rate as well as in the amount of released drug. Thus, we demonstrated the ability of the present mesoporous systems to intrinsically control the release rate and the amount of the released cargo by only minor structural variations. Furthermore, an in vivo experiment on zebrafish confirmed that the present model delivery system is nonteratogenic.
COBISS.SI-ID: 26701351
Fe-Pd alloys have many potential applications because of their unique chemical and magnetic properties, which can be tailored by changing their composition. In this study we have investigated the kinetic parameters for depositing Fe and Pd and their influence on the Fe-Pd alloy’s composition, while performing the deposition on a flat Au electrode and into an Au-sputtered porous alumina template. The electrodeposition of Fe and Pd was found to be irreversible and diffusion-controlled. Diffusion coefficients and charge-transfer coefficients were determined by cyclic voltammetry. The exchange current densities for both metallic ions in the porous alumina template and on the flat electrode were determined via a Butler-Volmer analysis. The diffusion coefficient was found to be lower for both metallic ions, by 2-3 times, when the template was used as a working electrode. Due to the hydrogen evolution overlapping with the reduction of the Fe2+, the kinetics of the Fe and of the Pd deposition was calculated using the Butler-Volmer model. We found that the exchange current densities, i.e., the rate of the deposition reaction, are comparable for Fe2+ and Pd2+ on both working electrodes. This indicates that the kinetics of the electrodeposition process is not influenced by the electrode geometry. Because of similar diffusion-coefficient ratios and similar kinetics on both the investigated working electrodes, using the same deposition conditions (i.e., solution and applied potential) results in Fe-Pd-based thin films and nanowires having similar compositions.
COBISS.SI-ID: 27452967