Blood group antigen studies using CdTe quantum dots and flow cytometry

Abstract

New methods of analysis involving semiconductor nanocrystals (quantum dots [QDs]) as fluorescent probes have been highlighted in life science. QDs present some advantages when compared to organic dyes, such as size-tunable emission spectra, broad absorption bands, and principally exceptional resistance to photobleaching. Methods applying QDs can be simple, not laborious, and can present high sensibility, allowing biomolecule identification and quantification with high specificity. In this context, the aim of this work was to apply dual-color CdTe QDs to quantify red blood cell (RBC) antigen expression on cell surface by flow cytometric analysis. QDs were conjugated to anti-A or anti-B monoclonal antibodies, as well as to the anti-H ( Ulex europaeus I) lectin, to investigate RBCs of A 1 , B, A 1 B, O, A 2 , and A weak donors. Bioconjugates were capable of distinguishing the different expressions of RBC antigens, both by labeling efficiency and by flow cytometry histogram profile. Furthermore, results showed that RBCs from A weak donors present fewer amounts of A antigens and higher amounts of H, when compared to A 1 RBCs. In the A group, the amount of A antigens decreased as A 1 > A 3 > A X = A el , while H antigens were A X = A el > A 1 . Bioconjugates presented stability and remained active for at least 6 months. In conclusion, this methodology with high sensibility and specificity can be applied to study a variety of RBC antigens, and, as a quantitative tool, can help in achieving a better comprehension of the antigen expression patterns on RBC membranes.

Highly fluorescent and superparamagnetic nanosystem for biomedical applications

“…The redshift probably results from the QD surface modification promoted by covalent coupling. These findings have already been previously reported for QD conjugation [13,82]. In addition, after BNP washing, using a NdFeB magnet, the absorption spectrum of the supernatant did not present any peak characteristic of the QD suspension (figure 9(c)).…”

“…On the other hand, QDs have also played a significant role in photonic and biomedical applications due to their broad absorption band, narrow emission spectra, high photoluminescence intensity, high photostability, and active surface [11]. Due to the wide range of QD biological applications as fluorescent probes with chemical specificity, different synthetic routes and conjugation strategies have been reported [11][12][13].…”

A report on a modified protocol for flow cytometry‐based assessment of blood group erythrocyte antigens potentially suitable for analysis of weak ABO subgroups

“…21 Although the advanced FC method already demonstrated the feasibility of antigen detection in those weak variants, 8 we thought that technical difficulties might still exist in many laboratories, as exemplified by the recent report, which described a failure in distinguishing an A el phenotype from the O-type samples even with the quantum dots-based sensitive FC assay. 22 Therefore, we tested whether our established RBC-FC analysis could identify small numbers of positive events in the weak ABO variant samples.…”

“…Regarding the ABO variants characterized by small amounts of antigens, for example, the A el and B m subtypes, it is generally believed that their presence can only be demonstrated by an adsorption‐elution test, which is the most sensitive serological technique 21 . Although the advanced FC method already demonstrated the feasibility of antigen detection in those weak variants, 8 we thought that technical difficulties might still exist in many laboratories, as exemplified by the recent report, which described a failure in distinguishing an A el phenotype from the O‐type samples even with the quantum dots‐based sensitive FC assay 22 . Therefore, we tested whether our established RBC‐FC analysis could identify small numbers of positive events in the weak ABO variant samples.…”

Mannose-binding lectin conjugated to quantum dots as fluorescent nanotools for carbohydrate tracing

“…(ii) UEA I (Ulex europaeus I) to study the expression of human erythrocyte antigens [24]; (iii) Cramoll (Cramoll 1,4) from Cratylia mollis to elucidate the glucose/ mannose profile in normal, benign, and malignant breast tissues [25]; and (iv) with jacalin to study leukemia cells [26]. Typical conjugation strategies involving lectins and QDs include adsorption or covalent binding between carboxyl moieties on the QD surface and amine groups in the proteins [27].…”