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  • 1
    Electronic Resource
    Electronic Resource
    “On–Off” Thermocontrol of Solute Transport. I. Temperature Dependence of Swelling of N-Isopropylacrylamide Networks Modified with Hydrophobic Components in Water (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 531-537 
    Details
    ISSN: 1573-904X
    Keywords: thermosensitivity ; hydrogels ; N-isopropylacrylamide ; interpenetrating polymer networks ; surface deswelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The swelling in water, as a function of temperature, of two series of N-isopropylacrylamide (NIPA Am) polymer networks was studied. In the first series, n-butylmethacrylate (BMA) was copolymerized with NIPA Am, and in the second, polytetramethylene ether glycol (PTMEG) was incorporated into NIPAAm network as a chemically independent interpenetrating network. With increasing BMA content in the poly(NIPAAm-co-BMA) network, the gel collapse point was lowered and the gels deswelled in a more gradual manner with increasing temperature. In the interpenetrating polymer networks (IPN) system, the gel collapse point was not significantly changed by the amount of incorporated PTMEG. In DSC thermograms of swollen samples, the shape and onset temperature of the endothermic peak corresponded to the gel deswelling behavior and gel collapse point. The temperature dependence of equilibrium swelling in water was shown to be a function of the gel composition in both network series. The synthesized networks formed a dense surface layer as the temperature increased past the gel collapse point. This dense layer retarded water efflux and thereby resulted in water pockets at the membrane surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015871732706
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    “On–Off“ Thermocontrol of Solute Transport. II. Solute Release from Thermosensitive Hydrogels (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 624-628 
    Details
    ISSN: 1573-904X
    Keywords: thermocontrol ; on–off release ; thermosensitive hydrogels ; interpenetrating polymer networks ; N-isopropylacrylamide ; polytetramethylene ether glycol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Poly(N-isopropylacrylamide) (NIPAAm)/polytetramethylene ether glycol (PTMEG) interpenetrating polymer networks (IPNs) were synthesized and their feasibility as thermosensitive hydrogels for drug release was investigated. The release of indomethacin incorporated into these matrices showed pulsatile patterns in response to temperature changes and was sensitive to a few degrees of temperature fluctuation. The temperature inducing on–off release deviated from the gel collapse temperature of unloaded gel, possibly because of solute effects on network properties. The lag time and release profile of indomethacin in the low-temperature region (on process) of each temperature cycle were affected by the gel composition and applied temperature. The results of this study demonstrate that solute release can be regulated by rapid deswelling of the surface of the gels in response to temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015860824953
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrogels: Swelling, Drug Loading, and Release (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 283-290 
    Details
    ISSN: 1573-904X
    Keywords: hydrogels ; swelling ; loading ; release kinetics ; functional polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrogels have been used by many investigators in controlled-release drug delivery systems because of their good tissue compatibility and easy manipulation of swelling level and, thereby, solute permeability. The desired kinetics, duration, and rate of solute release from hydrogels are limited to specific conditions, such as hydrogel properties, amount of incorporated drug, drug solubility, and drug–polymer interactions. This review summarizes the compositional and structural effects of polymers on swelling, loading, and release and approaches to characterize solute release behavior in a dynamic state. A new approach is introduced to compensate drug effects (solubility and loading) with the release kinetics by varying the structure of heterogeneous polymers. Modulated or pulsatile drug delivery using functional hydrogels is a recent trend in hydrogel drug delivery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015887213431
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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