A novel methodology for detecting variations in RBCs surface antigens by cell-tearing using optical tweezers

Abstract

Background: The quantitative analysis of cell surface antigens has attracted increasing attention due to the antigenic variation recognition that can facilitate diagnoses. The whole-cell-based analysis minimizes sample size, suggesting an alternative approach for detecting the variation in cell surface antigens. The optical tweezers (OT) are practical for precise single-cell manipulations, and has been widely used as a convenient tool in interdisciplinary fields. However, employing this technology as a biosensor using a "tearing" operation is still rare. Method:This paper presents a novel methodology based on the “tearing” operation of optical tweezers (OT) incorporated with the “dilution method” of antibodies to detect variations in red blood cell (RBC) surface antigens. The RBCs attach to the corresponding antibody-coated cover glass. Then, the binding firmness between an RBC and the functionalized surface is assayed by optically tearing using gradually reduced laser powers incorporated with serial antibody dilutions. Results:The experiment result shows that the higher dilution (lower antibody concentration), the lower power (lower optical force) needed to tear off the RBC binding from the functionalized surface, i.e., the antibody dilution fold is inversely proportional to the laser power. With the relative-quantitative analysis, the variation in RBC surface antigens can be intuitively estimated by comparing the maximum allowable dilution folds. The estimation gives that the antigens on the B3-type RBC are 35.7% of that on the B-type RBC, which is consistent with the literature findings using conventional biological methods. Conclusions:This study proposes a new application of the optical tweezers as a biosensor using the optically cell-tearing operation to estimate the variation in RBC surface antigens. With the proposed methodology, the detection of antigenic variation was successfully implemented without complicated optical force calculations and labored biological processing. One drop of blood from the fingertip is more than enough to obtain a satisfactory detection. It suggests an novel approach for antigenic variation analyses based on the whole-cell operation.