Geles autoensamblados de poloxaminas y poloxameros con ciclodextrinas

Zusammenfassung

Hydrogels are crosslinked polymeric networks with a soft and hydrophilic nature that makes them suitable in numerous biomedical applications such as matrices for drug delivery, wound healing, or tissue engineering. The self assembled hydrogels, i.e. those possessing a physical crosslinking, have attracted much attention lately because of their pharmaceutical and biological applications. During the gelation process, a protein, a peptide, or a drug can be added to the mixture so it will finally get immobilised inside the bulk of the gel. Consequently, these loaded gels can be used as potential substances release matrices. The phase behaviour of two types of poly(ethylene oxide)/ poly(propylene oxide) (PEO/PPO) copolymers, a reverse poloxamer (Pluronic 10R5) and a reverse poloxamine (Tetronic 90R4), in aqueous solutions was studied by dynamic light scattering, viscometry and infrared spectroscopy. The temperature-composition phase diagrams show that both copolymers tend to form aggregates in water. A series of supramolecular aggregates were prepared using the copolymers and cyclodextrins (CD). The combination of β-CD and each copolymer yields inclusion complexes (IC) with polypseudorotaxane structures. In contrast, when combining α-CD with the block copolymers, the observed effect is an increase in the viscosity of the mixtures yielding fluid (weak) gels. The mixtures were characterized using different techniques such as differential scanning calorimetry, viscometry and X-ray diffractometry. Gels and tablets prepared using Tetronic 90R4 and α-CD complexes were evaluated as release matrices. Two model molecules were tested: L-Tryptophan, and a protein (bovine serum albumin) in order to elucidate the erosion and diffusion mechanisms.