ABSTRACT:Interpenetrating polymer networks (lPNs) of poly(ethylene oxide-dimethyl siloxane-ethylene oxide) (PEO-PDMS-PEO) ABA triblock copolymer and poly(N-isopropyl acrylamide) (PIPAAm) has been synthesized as thermosensitive gels. Indomethacin andketoprofen were selected as model drugs and incorporated into thermosensitive gel. Pulsatile drug release produced from these thermosensitive gels was strongly influenced bytheswelling-deswelling kinetic properties of thermosensitive gels solubility dependence of drug as a function of temperature, and thetemperature applied. However, therelease behavior ofindomethacin andketoprofen at several fixed temperatures from the thermosensitive gel showed similar patterns. The exact initiation temperatures fordrug release of both drugs were similar andslightly below theswelling transition temperature of an unloaded gel.KEY WORDS Indomethacin / Ketoprofen / Pulsatile Drug Release / Solubility Dependence / Swelling Transition Temperature / Phase Continuity / Morphology / Swelling-Deswelling Kinetic / It is important to control drug release from delivery devices in order to produce a zero order release rate of sustained release. Therapeutically, the advantages of controlled release are ability to maintain drug levels constantly within an effective blood concentration range, to administer less drug to produce effective therapy and less frequent administration than with conventional dosage forms.Many efforts have been made to create new controlled release methods that sometimes emphasize the use of polymer.
ABSTRACT:Interpenetrating polymer networks (IPNs) composed of poly(ethylene oxidedimethyl siloxane-ethylene oxide) (PEO-PDMS-PEO) ABA triblock copolymer and poly(Nisopropyl acrylamide) (PIPAAm) were synthesized. Transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) studies of bulk IPNs revealed micro phase separation with partial phase mixing between two chemically independent networks. Aqueous equilibrium swelling curves were examined as a function of temperature. DSC thermograms of the swollen IPNs exhibited the same swelling transition temperature as that of PIPAAm, although the degree of swelling of IPNs was affected by polymer composition. These observations indicate that each network in the swollen IPNs exists independently and many have different morphology than the dried bulk state. The aqueous swelling-deswelling kinetics by temperature modulation of IPNs could be controlled by gel composition nd temperatures applied.KEY Crosslinked poIy( N -isopropyI aerylamide) (PIPAAm) demonstrates a sharp swelling transition (gel shrinking) around its LCST of 31-which may be unique among thermosensitive gels due to a relatively symmetric and sharp endothermic peak at the swelling transition temperature in DSC studies."Recently, crosslinked PIPAAm and its copolymer with a hydrophilic (HPL) componentPolym.
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