Electrophoretic Deposition of Chitosan–Hydroxyapatite Films and Their Electrochemical Behavior in Artificial Plasma

The electrochemical behavior of chitosan–hydroxyapatite films deposited on Ti CP was evaluated. Hydroxyapatite was synthesized from eggshell at different precipitation pH conditions. The films were deposited on the Ti CP surface from chitosan–hydroxyapatite solutions by means of electrophoretic deposition. The hydroxyapatite content of the solutions varied from 0 to 20 g/L. The different films obtained were evaluated by means of electrochemical measurements such as polarization curves, open circuit potential measurements, polarization resistance, and electrochemical impedance. The results obtained showed that regardless of the precipitation pH, it is possible to obtain pure hydroxyapatite from a waste such as eggshell. The incorporation of hydroxyapatite within the chitosan structure allows for improvement of the electrochemical performance of the bare Ti CP surface. It was observed that the passive zone was achieved at lower current densities, and that the stability zone of the passive layer increased. Electrochemical impedance analyzes showed that there is an improvement in corrosion resistance due to a more controlled growth of the passive layer that allows for the formation of a dense and compact film

Pathogenesis of Chagas' Disease: Parasite Persistence and Autoimmunity

Summary: Acute Trypanosoma cruzi infections can be asymptomatic, but chronically infected individuals can die of Chagas' disease. The transfer of the parasite mitochondrial kinetoplast DNA (kDNA) minicircle to the genome of chagasic patients can explain the pathogenesis of the disease; in cases of Chagas' disease with evident cardiomyopathy, the kDNA minicircles integrate mainly into retrotransposons at several chromosomes, but the minicircles are also detected in coding regions of genes that regulate cell growth, differentiation, and immune responses. An accurate evaluation of the role played by the genotype alterations in the autoimmune rejection of self-tissues in Chagas' disease is achieved with the cross-kingdom chicken model system, which is refractory to T. cruzi infections. The inoculation of T. cruzi into embryonated eggs prior to incubation generates parasite-free chicks, which retain the kDNA minicircle sequence mainly in the macrochromosome coding genes. Crossbreeding transfers the kDNA mutations to the chicken progeny. The kDNA-mutated chickens develop severe cardiomyopathy in adult life and die of heart failure. The phenotyping of the lesions revealed that cytotoxic CD45, CD8+ γδ, and CD8α+ T lymphocytes carry out the rejection of the chicken heart. These results suggest that the inflammatory cardiomyopathy of Chagas' disease is a genetically driven autoimmune disease