RESUMEN
The performance provided by graphene (Gr) and graphene oxide (GO) additives can be improved by achieving strong adhesion and uniform dispersion in the epoxy resin matrix. In this study, molecular modeling and simulation of DGEBA/DETA based epoxy nanocomposites containing Gr and GO additives were performed. Density functional theory and molecular dynamics simulations were used to investigate interfacial interaction energies and Young's Modulus. Improvement in the interaction energies was studied by controlling the epoxy:hardener ratio, type and the number of oxygen-containing functional groups on the GO, the mass percentage of Gr/GO filler in the epoxy matrix, size and dispersion of GO in the cell. It was demonstrated that functional groups with up to 10% oxygen content in GO significantly increase interfacial interaction energy for large size Gr/GO. Increasing DETA type amine ratio in the preparation of epoxy polymers increases the interaction energy for high oxygen content while decreasing the interaction energy for low oxygen content in GO for small size GO with edge functional groups. The performance of material dramatically decreased even at high DETA hardener and high GO mass percentages when the aggregation factor of Gr/GO was included in simulations that explain lower Gr/GO percentages in the experimental studies.
RESUMEN
INTRODUCTION: This prospective observational study aimed to assess the relevance of serial postoperative serum TNF-α, TNFR1 and TNFR2 measurements for predicting graft function and acute rejection episodes (AR) after transplantation. MATERIALS AND METHODS: We studied 50 kidney transplant recipients (31 female, 19 male; mean age: 38.36 ± 12.88). Blood samples were collected immediately before and after surgery at day 7, month 1 and month 3. Serum TNF-α, TNFR1 and TNFR2 levels were measured by ELISA using a commercial kit (Invitrogen ELISA). Serum cystatin-C levels were measured by particle-enhanced immunonephelometric method. Glomerular filtration rate (GFR) was estimated by Chronic Kidney Disease-Epidemiology (CKD-EPI) equation. Patients were assigned to their transplant outcomes in terms of acute rejection [AR(+) and AR(-)] and slow (SGF) or immediate graft function (IGF). RESULTS: Among 50 recipients, six had AR(+) and 44 had AR(-), depending on graft function: 17 had SGF and 33 had IGF. Serum creatinine, cystatin-C, TNF-α, TNFR1 and TNFR2 levels demonstrated consistent significantly decreases after transplantation while GFR values had consistent increases (p = 0.001). Pretransplant levels were not statistically different between AR(+) and AR(-) groups (TNF-α: 30.79 ± 5.96 vs. 27.95 ± 2.43 pg/mL, TNFR1: 55.96 ± 21.6 vs. 40.52 ± 7.41 ng/mL, TNFR2: 58.31 ± 8.06 vs. 50.9 ± 3.34 ng/mL, respectively) (p > 0.05). Serum TNF-α, TNFR1 and TNFR2 levels on day 7 and month 1 were also significantly higher in AR(+) group compared to AR(-) (p = 0.012, p = 0.049 for TNF-α, p = 0.001, p = 0.002 for TNFR1, p = 0.001, p = 0.002 for TNFR2). CONCLUSIONS: Our preliminary findings suggest that serum TNF-α, TNFR1 and TNFR2 levels might be considered useful markers of evaluating graft function after renal transplantation.