RESUMO
The bioceramic coating is fabricated on titanium alloy (Ti6Al4V) by laser cladding the preplaced wollastonite (CaSiO3) powders. The coating on Ti6Al4V is characterized by x-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy, and attenuated total reflection Fourier-transform infrared. The interface bonding strength is measured using the stretching method using an RGD-5-type electronic tensile machine. The microhardness distribution of the cross-section is determined using an indentation test. The in vitro bioactivity of the coating on Ti6Al4V is evaluated using the in vitro simulated body fluid (SBF) immersion test. The microstructure of the laser cladding sample is affected by the process parameters. The coating surface is coarse, accidented, and microporous. The cross-section microstructure of the ceramic layer from the bottom to the top gradually changes from cellular crystal, fine cellular-dendrite structure to underdeveloped dendrite crystal. The coating on Ti6Al4V is composed of CaTiO3, CaO, α-Ca2SiO4, SiO2, and TiO2. After soaking in the SBF solution, the calcium phosphate layer is formed on the coating surface.
Assuntos
Substitutos Ósseos/efeitos da radiação , Compostos de Cálcio/efeitos da radiação , Materiais Revestidos Biocompatíveis/efeitos da radiação , Lasers , Silicatos/efeitos da radiação , Titânio/efeitos da radiação , Ligas , Substitutos Ósseos/química , Compostos de Cálcio/química , Fenômenos Químicos , Materiais Revestidos Biocompatíveis/química , Teste de Materiais , Microscopia Eletrônica de Varredura , Silicatos/química , Espectrometria por Raios X , Espectroscopia de Infravermelho com Transformada de Fourier , Resistência à Tração , Titânio/química , Difração de Raios XRESUMO
BACKGROUND: The cytochrome P450 (CYP450) 2C19 681 genotypes affect the antiplatelet activity of clopidogrel. We investigated the correlation of CYP 2C19 681G > A mutation with clopidogrel resistance (CR). Additionally, we studied the effect of CR on clinical prognosis of patients with acute coronary syndrome (ACS). METHODS: One hundred ten ACS patients undergoing percutaneous coronary intervention, who were followed-up for 1 year, were included in the study. The patients were co-administered aspirin 100 mg/d and clopidogrel 75mg/d following a loading dose of 300 mg. CR was assessed on the basis of polymorphism observed in the CYP2C19 subgroup. RESULTS: Patients in GG genotype group exhibited greater inhibition of platelet aggregation than patients in GA and AA genotype groups (16.2 ± 10.1%; 10.2 ± 9.9%; 8.0 ± 5.9%, respectively, p < 0.01). CYP2C19 681GG genotype group was associated with lower CR than CYP2C19 681A allele (GA + AA) group (9/59 vs. (12+5)/51; p = 0.009). Over a follow-up of 12 months, the incidence of recurrent angina, acute myocardial infarction, and intra-stent thrombosis in CYP2C19 681 GG carriers was significantly lower than that in CYP2C19 681A allele (GA + AA) group (2/59 vs. 8/51, 1/59 vs. 6/51, 0 vs. 4/51, respectively, p < 0.05). CONCLUSION: CYP 2C19*2 is associated with reduced clopidogrel antiplatelet activity and might be an important marker for poor prognosis of ACS.
Assuntos
Síndrome Coronariana Aguda/genética , Citocromo P-450 CYP2C19/genética , Resistência a Medicamentos/genética , Inibidores da Agregação Plaquetária/farmacocinética , Polimorfismo de Nucleotídeo Único , Pró-Fármacos/farmacocinética , Ticlopidina/análogos & derivados , Ativação Metabólica/genética , Síndrome Coronariana Aguda/tratamento farmacológico , Síndrome Coronariana Aguda/cirurgia , Idoso , Alelos , Angina Pectoris/epidemiologia , Angina Pectoris/genética , Aspirina/uso terapêutico , Clopidogrel , Reestenose Coronária/epidemiologia , Reestenose Coronária/genética , Trombose Coronária/epidemiologia , Trombose Coronária/genética , Citocromo P-450 CYP2C19/fisiologia , Quimioterapia Combinada , Feminino , Seguimentos , Predisposição Genética para Doença , Genótipo , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/epidemiologia , Infarto do Miocárdio/genética , Intervenção Coronária Percutânea , Inibidores da Agregação Plaquetária/uso terapêutico , Pró-Fármacos/uso terapêutico , Prognóstico , Estudos Prospectivos , Recidiva , Stents , Ticlopidina/farmacocinética , Ticlopidina/uso terapêutico , Resultado do TratamentoRESUMO
Zirconia-toughened MgO-CaO-SiO2-P2O5-CaF2 glass-ceramics are prepared using sintering techniques, and a series of heat treatment procedures are designed to obtain a glass-ceramic with improved properties. The crystallization behavior, phase composition, and morphology of the glass-ceramics are characterized. The bending strength, elastic modulus, fracture toughness, and microhardness of the glass-ceramics are investigated, and the effect mechanism of heat treatments upon the mechanical properties is discussed. The bioactivity of glass-ceramics is then evaluated using the in vitro simulated body fluid (SBF) soaking test, and the mechanism whereby apatite forms on the glass-ceramic surfaces in the SBF solution is discussed. The results indicate that the main crystal phase of the G-24 sample undergoing two heat treatment procedures is Ca5(PO4)3F (fluorapatite), and those of the G-2444 sample undergoing four heat treatment procedures are Ca5(PO4)3F and ß-CaSiO3 (ß-wollastonite). The heat treatment procedures are found to greatly influence the mechanical properties of the glass-ceramic, and an apatite layer is induced on the glass-ceramic surface after soaking in the SBF solution.