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Digital Imaging-based Colourimetry for Enzymatic Processes in Transparent Liquid Marbles.

Chemphyschem : a European journal of chemical physics and physical chemistry (2020-11-10)
Nhat-Khuong Nguyen, Pradip Singha, Jun Zhang, Hoang-Phuong Phan, Nam-Trung Nguyen, Chin Hong Ooi
ABSTRACT

Liquid marbles are a promising microreactor platform that recently attracts significant research interest owing to their ability to accommodate a wide range of micro reactions. However, the use of destructive and ex-situ methods to monitor reactions impairs the potential of liquid-marble-based microreactors. This paper proposes a non-destructive, in situ, and cost-effective digital-imaging-based colourimetric monitoring method for transparent liquid marbles, using the enzymatic hydrolysis of starch as an illustrative example. The colourimetric reaction between starch and iodine produces a complex that exhibits a dark blue colour. We found that the absorbance of red channel of digital images showed a linear relationship with starch concentration with high sensitivity and repeatability. This digital-imaging-based colourimetric method was used to study the hydrolysis of starch by α-amylase. The results show high accuracy and applicability of first-order kinetics for this reaction. The demonstration of digital-imaging-based colourimetry indicates the potential of liquid marble-based microreactors.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Lugol solution, for microscopy (Bact., Bot.)
Sigma-Aldrich
α-Amylase from Bacillus licheniformis, Type XII-A, saline solution, ≥500 units/mg protein (biuret)
Sigma-Aldrich
Starch, soluble, ACS reagent
Sigma-Aldrich
Maltose solution, BioReagent, for molecular biology, ~20% in H2O