Electron Spin Resonance Study on the Dynamics of Polymeric Nanocapsules
Abstract:The aim of the present work was to make a contribution to the better understanding of nanocapsules by means of electron spin resonance spectroscopy. The main focus lay on the protection capacity and dynamics of distribution processes of the colloidal drug carriers, since these are key parameters for their performance. For this purpose, lipophilic spin probes were encapsulated in poly(D,L-lactide) and PEG-PLA nanocapsules. Polymer deposition after solvent displacement was used as the production method. First, the molecular mobility (spectral shape) and the polarity of the molecular environment (hyperfine splitting constant aN) of the spin probes was studied. Since nanocapsules undergo dilution during both experimental work and in-vivo application, this dynamical process was studied to monitor the distribution kinetics of the spin probe between the nanocapsules and the water phase. A reallocation of the spin probe within a minute was observed. Ten percent of the incorporated molecules diffused into the polar, aqueous environment. Finally the resistance of the incorporated spin probe to reduction with ascorbic acid was measured, depending on a change in the shell material. The spin probes inside PEG-PLA nanocapsules were protected to a higher degree than the ones incorporated into poly(D,L-lactide) nanocapsules. In conclusion, this ESR study provides information about the kinetics of distribution phenomena and the accessibility of the incorporated spin probes to the aqueous outer phase in a noninvasive manner in real time.
Document Type: Research Article
Publication date: June 1, 2005
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- Journal of Biomedical Nanotechnology (JBN) is a peer-reviewed multidisciplinary journal providing broad coverage in all research areas focused on the applications of nanotechnology in medicine, drug delivery systems, infectious disease, biomedical sciences, biotechnology, and all other related fields of life sciences.
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