Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 412478
Title Time-resolved fluorescence and fluorescence anisotropy of fluorescein-labeled poly(N-isopropylacrylamide) incorporated in polymersomes
Author(s) Lee, J.S.; Koehorst, R.B.M.; Amerongen, H. van; Feijen, J.
Source The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 115 (2011)45. - ISSN 1520-6106 - p. 13162 - 13167.
Department(s) Biophysics
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) energy migration - molecular-weight - phase-transition - temperature-dependence - gel - vesicles - spectroscopy - stability - hydrogels - systems
Abstract The phase behavior of fluorescein isothiocyanate (FITC) labeled poly(N-isopropylacrylamide) (PNIPAAm) incorporated in polymersomes (Ps) was studied by monitoring the fluorescence lifetime (FL) and the time-resolved fluorescence anisotropy (TRFA) as a function of temperature at pH 7.4. Ps containing FITC-labeled PNIPAAm with a diameter less than 200 nm were prepared by injecting a THF solution of poly(ethylene glycol)-b-poly(d,l-lactide) (mPEG-PDLLA) and FITC tagged PNIPAAm (FITC-N) into phosphate buffered saline (PBS, pH 7.4). Solutions of free FITC (2 µM) and FITC-N (2 µM) in PBS were used as controls. The polarized fluorescence decay curves of FITC were fitted with one rotational correlation time (¿1) and the corresponding amplitude (ß1), while those for FITC-N were fitted with two rotational correlation times (¿1,2) and their corresponding amplitudes (ß1,2). Short rotational correlation times, ¿1, correspond with the rotation of the FITC molecule itself, whereas ¿2 corresponds to FITC-segmental rotation. FITC-N encapsulated in Ps (FITC-N/Ps) showed a decrease of the rotational motion upon increasing the temperature. The long rotational correlation time (¿2) of FITC-N increased 3 fold, going from 15 to 40 °C, reflecting a reduced rotational mobility. The residual anisotropy (ß8) of FITC-N/Ps at pH 7.4 showed a gradual increase, going from 15 to 25 °C followed by a gradual decrease at higher temperatures. These results are explained by a transition from coil to globule, a gradual increase of intermolecular aggregation, and possibly phase separation and hydrogel formation
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