Thermo-responsive Layer-by-Layer Assemblies for Nanoparticle-based Drug Delivery
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Layer-by-layer (LbL) capsules, known for their versatility and smart response to environmental stimuli, have attracted great interest in drug delivery applications. However, achieving a desired drug delivery system with sustained and tunable drug release in response to temperature is still challenging. Here, a thermo-responsive drug delivery system of solid dexamethasone nanoparticles (DXM NPs) encapsulated in a model LbL assembly of strong polyelectrolytes poly (diallyldimethylammonium chloride)/poly (styrene sulfonate) (PDAC/PSS) was constructed. DXM NPs at an average size of 20196 nm were fabricated. ζ-potential measurements, X-ray photoelectron spectroscopy, and transmission electron microscopy conﬁrmed the successful adsorption of each layer. The influence of various parameters on drug release, such as number of layers, ionic strength of the adsorption solution, temperature and outer-most layer, has been investigated. Results have shown a controlled DXM release from LbL nanoshells by tuning number of layers and ionic strength of the adsorption solution. The DXM release from linearly growing LbL of PDAC/PSS (assembled without NaCl), which do not exhibit a glass transition, experienced a more temperature response than those from exponentially growing LbL of PDAC/PSS (assembled at 0.5 M NaCl), which exhibit a glass transition. Such a difference was attributed to be related with the free volume cavities within the assemblies. By tailoring the properties of those cavities, an ideal thermo-responsive drug delivery system may be obtained. This thermo-responsive NP-based drug delivery system with tunable permeability may possibly realize an “on” or “off” drug release mechanism in response to temperature, thus providing an alternative approach to delivery therapeutics with reduced toxic effects.
Zhou, Jing (2013). Thermo-responsive Layer-by-Layer Assemblies for Nanoparticle-based Drug Delivery. Master's thesis, Texas A & M University. Available electronically from