Suppression of Coffee-Ring Effect on Nitrocellulose Membrane: Effect of Polyethylene Glycol

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.

Suppression of Coffee-ring Effect (CRE) in the Development of Low-cost Diagnostic Kit

“…The addition of polymer or any other additives is one of the approaches done previously where it can alter the particle deposition of colloidal solution. From all mentioned above, one of the most applicable strategies is the manipulation of the protein concentration via additional solutes, such as chitosan (Wilkinson et al, 2021), polyethylene glycol (PEG) (Shahruddin et al, 2022), NaCl (Gorr et al, 2012) and sucrose (Shimobayashi et al, 2018) in protein's solvent. NaCl seems a promising choice among the additives due to its characteristics, such as non-toxic, cheap, and abundant availability.…”

“…Image acquisition of the dot blot was performed through EPSON L220 3-in-1 (Scanner function) with the following setting: 16>8-bit grayscale and 3200 dpi resolution. Image J (Version Java 1.8) was used for the membrane surface analysis to measure the relative color intensity and the total surface area using the 'line intensity' option (Shahruddin et al, 2022). However, the image analysis by ImageJ provides only relative measurement between the samples for comparison purposes.Figure 1 shows the flow chart for analysis of protein immobilization.…”