Search

Modern techniques for quantifying blood group antibody-antigen interactions are very limited, especially for weaker interactions which result from low antigen expression and/or partial expression of the antigen structure. Surface plasmon resonance (SPR) detection is often used to monitor and quantify bio-interactions. Previously, a regenerable, multi-fucntional platform for quantitative RBC phenotyping of normal antigen expression using SPR detection was reported. However, detection of weaker variants were not explored. Here, this sensitivity study used anti-human IgG antibodies immobilized to a gold sensor surface to two clinically important types of weaker D variants using SPR; weak D and partial D. Positive pre-sensitised cells bind to the anti-human IgG monolayer, and the response unit (RU) is reported (>100 RU). Unbound negative cells are directly eluted (<100 RU). Weak D cells were detected between a range of 180-580 RU, due to a lower expression of antigens. Partial D cells, category D VI, were also positively identified (352-1147 RU), similar to that of normal D antigens. The detection of two classes of weaker D variants was achieved for the first time using this fully regenerable SPR platform, opening up a new avenue to replace the current subjective and arbitrary methods for quantifying blood group antibody-antigen interactions.

Agglutinated blood transports differently onto paper than stable blood with well dispersed red cells. This difference was investigated to develop instantaneous blood typing tests using specific antibody-antigen interactions to trigger blood agglutination. Two series of experiments were performed. The first related the level of agglutination and the fluidic properties of blood on its transport in paper. Blood samples were mixed at different ratios with specific and nonspecific antibodies; a droplet of each mixture was deposited onto a filter paper strip, and the kinetics of wicking and red cell separation were measured. Agglutinated blood phase separated, with the red blood cells (RBC) forming a distinct spot upon contact with paper while the plasma wicked; in contrast, stable blood suspensions wicked uniformly. The second study analyzed the wicking and the chromatographic separation of droplets of blood deposited onto paper strips pretreated with specific and nonspecific antibodies. Drastic differences in transport occurred. Blood agglutinated by interaction with one of its specific antibodies phase separated, causing a chromatographic separation. The red cells wicked very little while the plasma wicked at a faster rate than the original blood sample. Blood agglutination and wicking in paper followed the concepts of colloids chemistry. The immunoglobin M antibodies agglutinated the red blood cells by polymer bridging, upon selective adsorption on the specific antigen at their surface. The transport kinetics was viscosity controlled, with the viscosity of red cells drastically increasing upon blood agglutination. Three arm prototypes were investigated for single-step blood typing.