Label-free electrochemical immunosensor based on Nile blue A-reduced graphene oxide nanocomposites for carcinoembryonic antigen detection.

In this article, a novel, label-free, and inherent electroactive redox immunosensor for carcinoembryonic antigen (CEA) based on gold nanoparticles (AuNPs) and Nile blue A (NB) hybridized electrochemically reduced graphene oxide (NB-ERGO) is proposed. The composite of NB-graphene oxide (NB-GO) was prepared by π-π stacking interaction. Then, chronoamperometry was adopted to simultaneously reduce HAuCl4 and nanocomposites of NB-GO for synthesizing AuNPs/NB-ERGO. The immunosensor was fabricated by capturing CEA antibody (anti-CEA) at this nanocomposite modified electrode. The immunosensor determination was based on the fact that, due to the formation of antigen-antibody immunocomplex, the decreased response currents of NB were directly proportional to the concentrations of CEA. Under optimal conditions, the linear range of the proposed immunosensor was estimated to be from 0.001 to 40 ng ml(-1) and the detection limit was estimated to be 0.00045 ng ml(-1). The proposed immunosensor was used to determine CEA in clinical serum samples with satisfactory results. The proposed method may provide promising potential application in clinical immunoassays with the properties of facile procedure, stability, high sensitivity, and selectivity.

[Comparison of edge fitness and metal-ceramic bonding force of base metal crowns performed using two methods].

PURPOSE: To compare the marginal fitness and metal-ceramic bonding strength between laser printing metal crown and cast cobalt-chromium alloy crown. METHODS: Cobalt-chromium alloy crowns (n=10)(group A) were made by laser printing and another 10 by traditional casting (group B), respectively. All the first molar crowns were metal substitutes, and the basal crowns were placed in the standard substitutes. The marginal fitness of the basal crown was assessed by observing the margin of the basal crown and the shoulder gap of the substitution under stereomicroscope. Shear test of the basal crown was carried out by universal tester to evaluate the bonding strength between the metal and the porcelain. The differences of the marginal fitness and the bonding strength between the two methods of making basal crown were compared. SPSS 25.0 sofware package was used to analyze the data. RESULTS: The gap between the metal base crown and the generation shoulder of group A was significantly smaller than that of group B[（48.52±5.26)µm vs (76.25±8.37)µm, P<0.05]. The intensity was significantly higher than that of group B [（11.35±3.29）N vs （7.24±2.07）N, P<0.05]. Under electron microscope, the metal layer of group A was more closely combined with the porcelain layer. CONCLUSIONS: The marginal fitness and bonding strength of metal base crowns made by laser printing and traditional casting methods are acceptable. Laser printing metal base crowns have better marginal fitness and stronger bonding strength between metal and porcelain, which is an ideal technology for metal base crowns.