Simulation of stimuli-triggered release of molecular species from halloysite nanotubes
| Autor: | Pedro A. Derosa, Divya Narayan Elumalai, Yuri Lvov, Joshua Tully |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Surface diffusion
Chemistry Diffusion Burst phase General Physics and Astronomy Nanotechnology 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Electrostatics 01 natural sciences 0104 chemical sciences Diffusion process Chemical physics Phase (matter) Zeta potential 0210 nano-technology Saturation (chemistry) |
| Zdroj: | Journal of Applied Physics. 120:134311 |
| ISSN: | 1089-7550 0021-8979 |
| DOI: | 10.1063/1.4964259 |
| Popis: | A Monte Carlo model is used to study the effect of environmental variables (pH and temperature) on the transport and release of dexamethasone molecules from Halloysite Nanotubes (HNTs) in a dielectric fluid medium. The model used for this study was introduced elsewhere and it is based on basic physics interactions without experimental parameters for these interactions. An intermediate phase between the burst and saturation phase is found and explained. Molecules experience a 1-D diffusion process that is different from the diffusion in the burst phase or the surface diffusion experienced by molecules attached to the wall. It is predicted that this phase exists when the molecule-wall interaction is attractive but not always noticeable in the release profile. In this work, it is shown that an agreement with the experiment better than previously reported is obtained when simulated delivery curves are produced by the weighted average of the release profiles from a collection of HNTs with diameters and lengths distributed according to the experimental sample, highlighting the relevance of HNTs' morphology in the release. HNTs are suitable for environment-triggered release and thus the effect of temperature, molecule zeta potential, and pH is studied. It is observed that for temperatures that significantly differ from room temperature (by 100's of degrees), the release profile changes significantly, increasing the delivery speed at high temperature and reducing that speed at low temperature. Finally, it is observed that as the pH becomes more acidic, both the molecule and inner wall surface become more positive (or less negative) with both eventually becoming positive leading to a repulsive interaction; thus, molecules are pushed out by electrostatic repulsion. On the contrary, as the pH becomes more basic, positive molecules become more positive while the wall becomes less negative, but even at pH 12, the wall remains negative and the interaction is attractive. Changes in pH between different regions may act as a trigger for delivery or as a control in the delivery rate. |
| Databáze: | OpenAIRE |
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