Resumen de Microestructura, propiedades y aplicaciones médicas de materiales poliméricos biodegradables
The framework of this thesis are the synthetic biodegradable polymers with biomedical applications.
Aliphatic polyesters are an attractive class of polymers, which can be used in biomedical and pharmaceutical applications. The study comprises the synthesis, microstructural analysis and properties of copolymers derived from glycolide and trimethylene carbonate, and the development of new and emerging applications such as the incorporation of drugs onto surgical sutures as well as the preparation of tissue scaffolds for tissue engineering.
The aim of the first part of the investigation is the study of bulk ring-opening copolymerization of glycolide with trimethylene carbonate under different conditions. The influence of the composition, temperature, reaction time, and initiator on the chain microstructure was studied by means of 1H and 13C NMR spectroscopy. The final microstructure was found to be highly dependent on the transesterification reactions. The thermal behavior was sensitive to the composition and to the length of the glycolyl microblocks. Differential scanning calorimetry and X-ray diffraction demonstrated that glycolyl-rich sequences could give rise to a single crystalline phase, whereas trimethylene carbonyl units were incorporated into the amorphous phase. The synthesis of copolymers from the melt-state transesterification of polyglycolide and poly(trimethylene carbonate) homopolymer mixtures was also studied. The hydrolytic degradation rate of the copolymers was found to depend on the microstructure and in general was enhanced with the degree of randomness.
The incorporation of drugs onto the thread surface of a braided surgical suture was also studied. Drugs are added to the surface of suture threads and its release is studied in different media with high performance liquid chromatography. The influence of the temperature, the diameter of the thread, the initial concentration of the antibacterial agent, and the applied procedure on the incorporation is also evaluated. The release rates depend on the medium. Partition and diffusion coefficients were also estimated. Biocompatibility and antibacterial efficacy of drug loaded sutures is also studied.
The preparation of mononofilamet sutures incorporating a drug is alos considered. Monofilament samples can be loaded by a molecular diffusion process using a swelling agent such as dichloromethane. The mechanical properties have been measured and have not shown a significant change for the drug loaded samples in knot tensile assays. The kinetics of both the loading process and the release have been investigated. The preparation of Poly-p-dioxanone tissue scaffolds is also considered. The influence of pore size, distribution and interconnectivity on mechanical properties, drug delivery and cell attachment is studied.
This material, with its outstanding flexibility, degradation period and biocompatibility, might be a good alternative to polyglycolide and polylactide scaffolds.
