Critical increment of Lewis blood group antigen in serum by cancer found by photothermal immunoassay

New photothermal immunoassay of human chorionic gonadotropin using Prussian blue nanoparticle-based photothermal conversion

A new near-infrared-based photothermal immunosensing strategy was developed for the sensitive and feasible detection of human chorionic gonadotropin (HCG) by use of a Prussian blue nanoparticle-based photothermal conversion system. Prussian blue nanospheres synthesized by the one-pot method were used for the labeling of anti-HCG detection antibody. A sandwich-type immunoreaction was initially conducted on a monoclonal anti-HCG antibody-coated microplate with a nanoparticle-labeled signal antibody. Accompanying formation of the sandwiched immunocomplex, Prussian blue nanospheres caused photothermal conversion under 980-nm laser irradiation, thereby resulting in an increase of the temperature of the detection system measured by a portable digital thermometer. The properties and factors influencing the analytical performance of the photothermal immunoassay were studied in detail. Under the optimal conditions, the Prussian blue nanoparticle-based photothermal immunoassay exhibited good temperature responses relative to target HCG concentrations within the dynamic range of 0.01-100 ng mL^-1 at a low detection limit of 5.8 pg mL^-1. This system also displayed good anti-interference behavior with regard to other cancer biomarkers, good reproducibility, and relatively long storage stability. The method accuracy was evaluated for analysis of human serum specimens, giving results that matched well with those obtained with a commercial HCG enzyme-linked immunosorbent assay kit. Importantly, this protocol is promising for advanced development of photothermal immunoassays. Graphical abstract.

Differentiation of isomeric Lewis blood groups by positive ion electrospray tandem mass spectrometry

Lewis histo-blood group antigens are one of the major classes of biologically active oligosaccharides. In this work, underivatized Lewis blood groups were studied by electrospray tandem mass spectrometry (ESI-MS(n)) in the positive mode with three different mass analyzers: Q-TOF (quadrupole time-of-flight), QqQ (triple quadrupole), and LIT (linear ion trap). It was observed that, under collision-induced fragmentations, type 1 Lewis antigens (Le(a) and Le(b)) could be distinguished from type 2 (Le(x) and Le(y)) on the basis of specific fragmentations of the GlcNAc unit. Whereas O-4-linked sugars of the GlcNAc are lost as residues, the O-3-linked sugars undergo fragmentation both as sugar units and as sugar residues (unit -18Da). Type 2 Lewis antigens also showed a characteristic cross-ring cleavage (0,2)A(2) of the GlcNAc. As a result, the product ions at m/z 388 and 305, characteristic of Le(x), and m/z 372, characteristic of Le(a), are proposed to distinguish the trisaccharide isomers Le(x)/Le(a). Also, the product ions at m/z 534 and 305, characteristic of Le(y), and m/z 372, characteristic of Le(b), are proposed to distinguish the tetrasaccharide isomers Le(b)/Le(y). These diagnostic fragment ions were further applied in the identification of Lewis type 2 antigens (Le(x) and Le(y)) in the lipopolysaccharide of the human gastric pathogen, Helicobacter pylori.

Detection and measurement of a single blood cell surface antigen by thermal lens microscopy

A highly sensitive method for detection of antigens on the surface of a single blood cell using thermal lens microscopy is described. Colloidal gold, coated with antibody, was used to stain membrane antigens of leukocytes. Human leukocyte antigens on the lymphocytes and mononuclear leukocytes were observed by new thermal lens microscopy, which involves spectrometry using a laser-induced thermal-lens effect. Antigens of HLA-A, -B, and -C loci on the lymphocytes were identified and quantitated using a single cell. The image of HLA-A, -B, and -C antigen distribution on a mononuclear leukocyte was obtained. Our laser microscope, newly devised for measuring convex surface cells, is a powerful analytical tool for detecting and quantitating localized antigens in a single cell and/or cell-surface-associated molecules.