Caracterización de nanoestructuras de quitosano, fibroína de seda y oro como liberadores de fármacos

Résumé

One of the main problems when using drug delivery systems is their tendency to aggregate under physiological conditions. Polymers have been proposed as stabilizing agents for avoiding this issue. Among them, chitosan (CS) is a polycationic polyelectrolyte in solution, which has shown good abilities in the stabilization of several negatively charged nanostructures. The objectives of this work were sinthesizing and characterizing nanodispositives for drug delivery in which medium molecular weight (MMW) CS acts as stabilizing agent for different negatively charged nanostructures. Concretely, nanodispositives composed of MMW CS and gold nanopartícles coated with gold (AuNP) and MMW CS and silk fibroin nanoparticles (SFN). Evaluating the citotoxicity of MMW CS, AuNP, SFN, and the nanostructures developed, MMW CS:AuNP and MMW CS:SFN, in HeLa cell cultures. Finally, characterize complex nanodispositives composed of MMW CS and other complex biopolymers as alginate, dextran sulfate and polyethylene glycol 4000, among others. And, evaluate them as drug delivery systems using insulin as a model. In order to characterize nanostructures, hydrodynamic diameter by dynamic light scattering (DLS), Z potential, UV-Vis spectrophotometric analysis, and photocentrifugation analysis were developed. Trasmission electron microscopy and scanning electron microscopy were used to visualize nanostructures. Citotoxicity of the nanodispositives was evaluated by tetrazolium salt reduction (MTT) by HeLa cell cultures. High performance liquid chromatography (HPLC) was used to evaluate the insulin released by polysacharide complex nanodevices. The results obtained in this work let conclude 1. CS MMW in solution at 10-5 g/mL and pH lower than 6.5 shows mainly nanometric size. When increased ionic strength, this nanostructures diminished their size as a result of the screening effect. 2. CS MMW in acidic solution is a polycationic polymer capable of stabilizing polyanionic nanostructures. Its derivatives as glycol CS keep the stabilizing properties of the polyelectrolyte. 3. Properties of the nanostructures obtained as a result of the interaction of MMW CS and negatively charged nanoparticles depended on the polyelectrolyte concentrations and the proportions among the biopolymer and polyanionic nanoparticles. 4. MMW CS acts as scaffold in which AuNP got immobilized and protected from aggregation at low pH of high ionic strength conditions. 5. MMW CS is placed on the surface of SFN avoiding their aggregation at high ionic strength. SFN can be stabilized at high ionic strength by using MMW CS or glycol CS. Thus, SFN is a promising biomaterial for nanotechnology. 6. MMW CS modulated the size and the aggregation of the complex polyssacharyde nanodevices. 7. MMW CS, AuNP, SFN and nanodevices composed of MMW CS:AuNP and MMW CS:SFN showed biocompatibility in HeLa cell cultures.