Azo-polysiloxane micelles charged with nifedipine

Abstract

Abstract Abstract One recent aspect of the research study on polymers is their capability to respond to external stimuli. Of importance are photosensitive polymers due to their application in drug delivery systems, sensors, therapeutic devices or optoelectronic switches. The present paper focuses on the azo-polysiloxane micelles capacity charged with hydrophobic drugs, such as nifedipine. Azo-polysiloxanes modified with quaternary ammonium groups and which are capable to generate photo-sensitive micelles were synthesized and characterized by 1H-NMR, UV-VIS and fluorescence spectroscopy. The critical concentration of the micellar aggregation (CCA) was evaluated as was the nifedipine embedding capacity. The CCA values were influenced only by the hydrophobic/hydrophilic balance and not by the chemical structure of the quaternary ammonium groups. The disaggregation capacity of the micelles under UV irradiation was investigated as well, and the best results were obtained for the samples with higher azobenzene content. The DLS measurements evidenced micelles diameters situated in the optimum range domain (70–130 nm). The capacity to incorporate nifedipine inside the micelles was demonstrated. The micelles proved to be stable in time, 21 days after preparation with the diameter having constant values. Graphical abstract