Papers by Author: Raluca Petronela Dumitriu

Abstract: Different types of stimuli responsive polymers that respond with a property change to a variation in the environmental conditions are an attractive class of materials for advanced applications in biomedical or pharmaceutical fields. Three types of responsive biocompatible and biodegradable polymer matrices are presented as potential biomaterials for medical application as carriers for various drugs and tissue engineering substitutes. Hybrid hydrogels based on collagen/ N-isopropyl acrylamide containing montmorillonite nanoparticles are promising materials for tissue engineering and also as carriers for norfloxacin, a chemotherapeutic antibacterial agent. Semi-interpenetrated hydrogels based either on substituted anhydride modified collagen and 2-hydroxyethyl methacrylate or on alginate and poly (N-isopropylacrylamide) were tested as matrices for the controlled delivery of bisoprolol fumarate, an antihypertensive drug and respectively of ketoprofen, a non-steroidal anti-inflammatory drug.

Abstract: Stimuli responsive hydrogels are very attractive for applications in sustained and/or targeted drug delivery systems. As the release of drugs is related to the swelling behavior of hydrogels, the swelling kinetic studies become of great importance to appreciate the release kinetics from hydrogel matrices. Hydrogels with high performance properties have been prepared from N-isopropylacryl amide (NIPAAm) and sodium alginate, crosslinked with N,N`-methylene-bis-(acrylamide) (MBAAm). This study is focused on the investigation of swelling and drug release kinetics, coupled by morphological studies. The kinetic parameters of the swelling at different temperatures for hydrogels samples have been evaluated and confirmed their temperature-responsive behavior. The swelling rate constant (ksw) decreases of with increasing temperature and slight increases with the alginate content in the samples. The drug release kinetic study from the prepared hydrogel matrices was performed in twice-distilled water and ethanol for bioactive agents as vanillin and ketoprofen, respectively. An increase of alginate content results in a slower rate and smaller percentage of vanillin and ketoprofen released. It has been established that the ketoprofen occurs according with case II of transport and vanillin release behavior occurs by an anomalous transport mechanism. The values of the release rate constant (kr) decreased by increasing swelling degree in case of 75/25 NIPAAm/alginate hydrogels and decreased also by increasing content of alginate in hydrogels with various compositions. Morphological studies performed by environmental scanning electron microscopy (ESEM) evidenced a relaxed network at high relative humidity, which explain both swelling and release profiles.