Impedimetric transduction of swelling in pH-responsive hydrogels

Abstract

A pH-responsive hydrogel composed of an aliphatic diamine cross-linked with polyethylene glycol diglycidyl ether (PEGDGE) using a single, rapid polymerisation step has been used to detect glucose by entrapping glucose oxidase (GOx) within its cationic network. The swelling response of hydrogel disks on exposure to glucose were optimised through variation of factors including the cross-linking density of the network, GOx loading and the addition of catalase. Hydrogel-modified carbon cloth electrodes were also prepared and characterised using voltammetric and impedimetric techniques. Non-faradaic electrochemical impedance spectroscopy (EIS) and gravimetry were both employed to track the swelling response of the gels quantitatively. The clear potential of utilising impedance to transduce hydrogel swelling was demonstrated where a linear decrease in gel resistance (Rgel) corresponding to the swelling response was observed in the range 1 to 100 μM. A dramatic increase in the limit of detection of six orders of magnitude over the gravimetric measurement was achieved (from 0.33 mM to 0.08 μM). This increased sensitivity, coupled with the textile-based electrode substrate approach opens the potential applicability of this system for monitoring glucose concentration via the skin by sweat or interstitial fluid (ISF).

Screen‐printed Tattoo Sensor towards the Non‐invasive Assessment of the Skin Barrier

“…Poly(ethylene glycol)diglycidyl ether (PEDGE) -J effamine hydrogels of approx. 10 mm depth were used in all experiments.T hese were prepared using ap rotocolp reviously reported [36].T his was prepared by weighingo ut and mixing 9.426 gP EDGE, 14.923 gd eionised water (DIW) and 2.651 gJ effamine EDR-148a nd stirred for 5min to get ah omogenous mixture.T his mixture was pouredinto asmall crystallizing dish and placed in the refrigerator (4 8C) overnight to cure.…”

“…10 mm depth were used in all experiments. These were prepared using a protocol previously reported . This was prepared by weighing out and mixing 9.426 g PEDGE, 14.923 g deionised water (DIW) and 2.651 g Jeffamine ® EDR‐148 and stirred for 5 min to get a homogenous mixture.…”

Remote Microwave and Field-Effect Sensing Techniques for Monitoring Hydrogel Sensor Response

“…Various transduction techniques, such as optical, electrical, and mechanical techniques, have been developed in the past to monitor hydrogel response to chemicals and biomolecules [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. The optical transduction technique measure changes in optical and dimensional properties of the hydrogels with optical methods.…”

“…However, the major drawback of the optical technique is the bulkiness of the readout instrumentation needed to capture the optical response of the hydrogel. The electrical technique for measuring the hydrogel’s response to chemicals and stimuli relies on measuring hydrogel conductance [ 11 ], resistance or impedance [ 12 ]. This electrical technique has the advantage of high sensitivity and it can be used with compact read-out instrumentation.…”

Desenvolvimento de dispositivos microfluídicos para análise de sistemas líquidos complexos

“…interesse em hidrogéis para sensores em um gráfico de trabalhos publicados ao longo dos últimos 19 anos. Estes sensores podem ser colorimétricos [48], eletroquímicos [49], ópticos [50] e elétricos [51]. Uma parte do trabalho de doutorado envolveu o estudo de sensores com hidrogéis funcionalizados com ácido borônico, tema da próxima seção.…”