No abstract

In the development of the diagnostic kit, it was favorable to have a low antigen concentration due to the difficulty of antigen preparedness and purification. However, it can cause the coffee-ring effect, producing different pattern formations on the selected membrane. It can lead to a false interpretation of the result. Thus, the immobilization of protein solution (lysozyme) as a model protein for antigen, with the addition of hydrosoluble polymer additive onto a membrane, was evaluated to suppress the coffee-ring effect. This research aims to evaluate the effect of polyethylene glycol on the protein solution for coffee-ring effect suppression and to analyze the image of the coffee-ring effect. From the experimental studies, 5 different concentrations (v/v%) of PEG which are 3.0, 2.0, 1.0, 0.1 and 0.01 v/v% is added at 4.0 mg/mL of lysozyme solution before being spotted onto nitrocellulose membrane. The color intensity of the dried spot, together with the formation of the coffee-ring effect, is analyzed by Image-J software. It is the approach to measure the suppression of the ring effect, in which 0.01 v/v% concentration portrays the most faded ring effect on nitrocellulose membrane. This effect occurs due to a surface tension gradient that causes the solute particles to accumulate at the edge of the droplet. As Marangoni flow has been altered, the coffee-ring effect is successfully suppressed; thus, uniform pattern deposition is achieved.