Detection of creatinine using surface-driven ordering transitions of liquid crystals

ABSTRACT

Determining creatinine levels in blood is of great importance in the detection of high risk for renal failure. Here, we report a simple methodology for real-time monitoring of creatinine employing surface-driven ordering transitions in liquid crystals (LCs) by changing pH in presence of creatinine deiminase enzyme. It is found that when 5CB (4-Cyano-4ʹ-pentylbiphenyl) LC doped with 4ʹ-hexyl-biphenyl-4-carboxylic acid, a bright optical appearance was observed (at aqueous–LC interface) which is not disturbed in presence of creatinine, consistent with a planar/tilted orientation of the LC molecules at those interface. Interestingly, in presence of creatinine deiminase, an ordering transition was observed resulting from enzymatic reactions (giving rise to NH₄⁺ ions) that can change the local pH values and lead to dark optical appearance of the LC. Presence of different amounts of creatinine would lead varied ordering transition that can be monitored in real time in presence of creatinine deiminase. Our approach could detect the creatinine levels as low as that of the healthy adult (~50 µM) and can be successfully applied to measure higher concentration of creatinine in real time using dynamic optical response of the LC.

GRAPHICAL ABSTRACT

KEYWORDS:

• Liquid crystals
• biosensors
• creatinine
• ordering transition

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This work was carried out with the financial support from IISER Mohali and Department of Atomic Energy (DAE-BRNS), Key Project 2012/20/34/7/BRNS ‘Passive Sensor Materials based on Liquid Crystals.’ I. Verma and S. Sidiq acknowledge the receipt of a graduate fellowship from IISER Mohali and UGC, respectively.