Narrow Results

Two zinc(II) phthalocyanines (ZnPcs) were conjugated with a monoclonal antibody (MAb) directed against carcinoembryonic antigen (CEA), using an in situ activated carboxylic acid on the ZnPcs. The bioconjugate with the highest ZnPc/MAb ratio of 3 was investigated in vitro for its ability to target and fluorescently label human colorectal HT-29 cells. The ZnPc-CEA MAb 2 was observed to efficiently target HT-29 cells, about 37 times more than unconjugated ZnPc. Furthermore, in the presence of a 4-fold excess of unlabelled anti-CEA antibody, the fluorescence signal of 2 was reduced by ~90% showing that the targeting is CEA-mediated. These studies further confirm the high specificity of Pc-antibody conjugates for antigens over-expressed on tumor cells and warrant further investigations of these immunoconjugates and their derivatives for imaging of colorectal cancer.

An ultrasensitive electrochemical immunosensor based on Nb-doped titanium dioxide was developed for detection of carcinoembryonic antigen (CEA). The electrochemical signal enhancement was due to the synergistic effect by NbT and nanogold. The influence factors (pH, temperature and incubation time) were investigated in detail. Under optimal conditions, the immunosensor was able to detect the concentration of CEA in the range of 0.5 ng ⋅ mL^-1 to 150 ng ⋅ mL^-1, with a lower detection limit of 8.95 pg ⋅ mL^-1. The proposed immunosensor showed high sensitivity, excellent selectivity and good stability.

A novel electrochemical immunosensor for determination of carcinoembryonic antigen (CEA) in human serum was fabricated by depositing Mo–Mn₃O₄/MWCNTs/Chits nanocomposite onto an indium-tin oxide (ITO) electrode. Mo-doped Mn₃O₄ (MMO) was synthesized by sol–gel method and the presence of molybdenum improved its electrochemical properties. The MMO/MWCNTs/Chits nanocomposite could accelerate the electron transfer rate and enlarge the surface area to capture a large number of Carcinoembryonic Antigen (CEA). The factors influencing the performance of the immunosensor were investigated, such as incubation time, incubation temperature and pH. Under optimal conditions, the electrochemical immunosensor could detect CEA in a linear range from 0.1ng$\cdot$mL${}^{-1}$ to 125ng$\cdot$mL${}^{-1}$ with a detection limit of 4.9pg$\cdot$mL${}^{-1}$ ($S∕N=$$3$). In addition, it exhibited high sensitivity and acceptable stability on a promising immobilization platform for signal amplification, which could be extended to other labeled recognition systems. This electrochemical immunosensor may provide potential applications for the clinical diagnosis.

The sandwich-type immunoassays have been developed by using electrochemical and surface-enhanced Raman scattering (SERS) techniques for the detection of carcinoembryonic antigen (CEA). Nile blue as a kind of Raman dye has been decorated on nanospheres with polydopamine resin (PDR) via $\pi$-stacking interaction. The Nile blue displays the strong SERS signals as well as a characteristic electrochemical reduction peak at $-$0.33V (versus Ag/AgCl). The implementation of the PDR nanospheres mixing with Au nanoparticles (AuNPs/PDR) exhibits a better electrical conductivity and large SERS enhancement. The immunoassays based on Nile blue-labeled AuNPs/PDR nanospheres have been fabricated by using electrochemical and SERS techniques for the detection of CEA. The proposed immunoassay shows higher sensitivity, high selectivity, lower detection limit and long-term stability. The performances of the electrochemical immunoassay are better than that of SERS immunoassay. For the electrochemical immunoassay, the linear range occurs from 1pg/mL to 100ng/mL ($R=0.995$) with a detection limit of 0.68pg/mL and signal-to-noise ratio of 3 in the detection of CEA. The data for the analysis of human serum samples by using the electrochemical method are acceptably consistent with those obtained from the enzyme-linked immunosorbent assay (ELISA). The proposed immunoassay exhibits a promising potential for application in clinical diagnosis.