Flow injection analysis of binding reaction between fluorescent lectin and cells

Prior studies have explored lectin-cell interactions using fluorescence and labeling techniques. However, quantifying the exact number of bound lectins has remained a challenge. Existing methods often rely on indirect measurements, such as the avidin-biotin system, which can introduce inaccuracies. The inability to directly measure bound biotin molecules limits the precision of these approaches. Researchers have sought alternatives that provide more reliable quantification of binding events. The need for a simpler and faster method has persisted in the field. Fluorescent labeling has been used to track lectin binding, but fluorescence stability during binding has not been fully characterized. This gap motivated the development of a new technique that could directly estimate bound lectin amounts.

The goal was to develop a direct and sensitive method to quantify the binding of fluorescent lectins to cells. The previous method using the avidin-biotin system failed to determine the true bound lectin amount. This study aimed to overcome that limitation by using a flow injection system. The researchers wanted to measure the number of binding sites on cells accurately. They also aimed to assess the binding kinetics and affinity of different lectins. The method needed to be rapid and simple for practical application. The study focused on yeast cells as a model system. The ultimate purpose was to provide an alternative to radioactive labeling methods.

The researchers used a flow injection system to analyze lectin-cell binding. Fluorescently labeled lectins were prepared and tested for linearity. Cell suspensions were injected directly into the flow system after binding. The fluorescence of the lectins was monitored during the process. The method did not require prior separation of bound and free lectins. Binding reactions were allowed to reach equilibrium within 10 minutes. Scatchard analysis was used to calculate binding site numbers and affinities. The method was tested on yeast, bacteria, and mouse spleen cells.

The labeled lectins showed linear fluorescence responses between 20 and 1000 ng. Fluorescence intensity remained stable after binding to cells. Binding equilibrium was achieved within 10 minutes for all tested lectins. Scatchard analysis revealed 1.3-1.6 x 10^8 binding sites per yeast cell. Affinity constants ranged from 3.2 to 4.7 x 10^6 M^-1. The method was applied to bacteria and mouse spleen cells successfully. The procedure required less than an hour to complete. The method provided a sensitive and rapid alternative to radioisotope labeling.

The flow injection method enables accurate quantification of lectin-cell binding. The method avoids the limitations of the avidin-biotin system. Fluorescence stability during binding supports reliable measurements. Binding kinetics were rapid and consistent across different lectins. The number of binding sites per cell was determined precisely. The method is applicable to various cell types beyond yeast. The procedure is simple and suitable for high-throughput analysis. The authors propose this method as a viable alternative to radioactive labeling.