Liquid Crystal-Based Proton Sensitive Glucose Biosensor

Abstract

A transmission electron microscopy (TEM) grid filled with 4-cyno-4-pentylbiphenyl (5CB) on the octadecyltrichloro silane-coated glass in an aqueous medium was developed to construct a glucose biosensor by coating poly(acrylicacid-b-4-cynobiphenyl-4-oxyundecylacrylate) (PAA-b-LCP) at the aqueous/5CB interface and immobilizing glucose oxidase (GOx) covalently to the PAA chains. The glucose was detected from a homeotropic to planar orientational transition of 5CB by polarized optical microscopy under crossed polarizers. The maximum immobilization density of the GOx, 1.3 molecules/nm(2) obtained in this TEM grid cell enabled the detection of glucose at concentrations as low as 0.02 mM with a response time of 10 s. This liquid crystal-based glucose sensor provided a linear response of birefringence of the 5CB to glucose concentrations ranging from 0.05 to 2 mM with a Michaelis-Menten constant (Km) of 0.32 mM. This new and sensitive glucose biosensor has the merits of low production cost and easy detection through the naked eye and might be useful for prescreening the glucose level in the human body.

Biosensor utilizing a liquid crystal/water interface functionalized with poly(4-cyanobiphenyl-4′-oxyundecylacrylate-b-((2-dimethyl amino) ethyl methacrylate))

“…Because of their high sensitivity and rapid response with respect to orientation, small-molecule LCs are an attractive medium for detecting chemical/biochemical events occurring at an interface as a result of optical changes that can be viewed with the aid of a polarized optical microscopy [28][29][30][31]. An optical change can occur as a result of a change in orientation of the LCs from vertical to parallel alignments at the water/LC interface upon adsorption of biomaterials [32].…”

Specific detection of avidin–biotin binding using liquid crystal droplets

“…Formation of LC droplets was carried out using the same method previously reported by Khan et al [24]. Briefly, the liquids were supplied to a microfluidic device via a flexible plastic tubing (Norton, USA, I.D.…”

Bienzyme liquid-crystal-based cholesterol biosensor

“…Previous studies have revealed that the response of 5CB can be tuned to external stimuli by functionalizing it with surfactant and polyelectrolytes [19,20]; for example, 5CB functionalized with pH-responsive poly(acrylic acid) (PAA) brushes as a support for immobilization of glucose oxidase has been used as a glucose biosensor. This sensor showed improved sensitivity in glucose detection as a result of the fast response of 5CB to changes in the local pH caused by the enzymatic reaction of glucose [21]. Similarly, a cholesterol oxidase (ChO)-immobilized LC/aqueous interface, with co-immobilization of horseradish peroxidase (HRP), can be used as a cholesterol biosensor, based on a similar enzymatic reaction.…”