Polymer indicator displacement assay (PIDA) with boronic acid receptors on graphene foam electrodes for self-optimised impedimetric lactic acid determination

Wikeley, Simon M.; Lozano-Sánchez, Pablo; Caffio, Marco; James, Tony D.; Marken, Frank

doi:10.1016/j.snb.2022.133089

Cited by 4 publications

(9 citation statements)

References 27 publications

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“…It has been estimated that the roughness factor for these types of electrodes is approximately 100 with a geometric surface area of 12 × 10 −2 cm 2 . 10 Therefore, the specific capacitance for graphene foam can be estimated as 0.6 μF cm −2 , which is low for graphene but consistent with previous reports 24 (typically for glassy carbon the capacitance is 20 μF cm −2 without activation, 25 and the theoretical/measured limit suggested for graphene in high ionic strength environments 26 is approximately 21 μF cm −2 ). In previous studies of graphene foam electrode capacitance, similar capacitance values were reported and the effect of surface oxidation on increasing pseudocapacitance was pointed out.…”

Section: ■ Results and Discussionsupporting

confidence: 89%

“…The capacitance 7.0 μF is associated with the pristine graphene foam. It has been estimated that the roughness factor for these types of electrodes is approximately 100 with a geometric surface area of 12 × 10 –2 cm 2 . Therefore, the specific capacitance for graphene foam can be estimated as 0.6 μF cm –2 , which is low for graphene but consistent with previous reports (typically for glassy carbon the capacitance is 20 μF cm –2 without activation, and the theoretical/measured limit suggested for graphene in high ionic strength environments is approximately 21 μF cm –2 ).…”

Section: Resultssupporting

confidence: 86%

“…The amount of T1 (5 μg, 10 nmol or approximately 21 Å 2 per molecule) has been optimized to represent approximately one monolayer (with slight excess) of the pyrene-appended molecule on the graphene surface. 10 Functionalization of a bare graphene foam electrode with the pyrene-appended pyridinium boronic acid molecule T1 causes an approximately 10-fold increase in capacitance at the graphene foam electrode surface when compared to the capacitance of the nonfunctionalized electrode. This effect is not pH dependent (investigated from pH 2 to 12) when monitored using EIS at 0.0 V vs Ag/AgCl.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Boronic acid-modified 3D-graphene foam electrode sensors were prepared via drop–casting of a boronic acid (T1, precursor molecular weight 486.21 g mol –1 ; equiv 2) solution (1 mg/mL, 5 μL) onto the working electrode disc, yielding a 5 μg (or 10 nmol) surface coverage. In previous work, it was shown that a lower amount of T1 decreased the sensor response and a higher amount of T1 caused blocking and loss of performance. , The modified sensor was then rinsed using deionized water before drying and stored before use. For lactic acid sensing using EIS, a droplet (approximately 100 μL) of lactic acid in phosphate buffer at the required pH was added to a freshly prepared boronic acid-modified electrode, ensuring all electrodes were covered.…”

Section: Methodsmentioning

confidence: 99%

“…A precursor molecule with protected boronic acid is synthesized, attached to a graphene surface, and then employed for the sensor (see Figure ) by neopentylglycol release in contact with aqueous media. In recent work, it was shown that T1 can be adsorbed onto graphene foam film electrodes for the voltammetric detection of glucose or for the detection of lactic acid . In these studies, a redox-active polymer was employed to modulate Faradaic current responses related to analyte binding in a polymer indicator displacement assay (PIDA).…”

mentioning

confidence: 99%

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Pyrene-Appended Boronic Acids on Graphene Foam Electrodes Provide Quantum Capacitance-Based Molecular Sensors for Lactate

Wikeley,

Przybylowski,

Gardiner

et al. 2024

ACS Sens.

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Molecular recognition and sensing can be coupled to interfacial capacitance changes on graphene foam surfaces linked to double layer effects and coupled to enhanced quantum capacitance. 3D graphene foam film electrodes (Gii-Sens; thickness approximately 40 μm; roughness factor approximately 100) immersed in aqueous buffer media exhibit an order of magnitude jump in electrochemical capacitance upon adsorption of a charged molecular receptor based on pyrene-appended boronic acids (here, 4-borono-1-(pyren-2-ylmethyl)pyridin-1-ium bromide, or abbreviated T1). This pyrene-appended pyridinium boronic acid receptor is employed here as a molecular receptor for lactate. In the presence of lactate and at pH 4.0 (after pH optimization), the electrochemical capacitance (determined by impedance spectroscopy) doubles again. Lactic acid binding is expressed with a Hillian binding constant (K lactate = 75 mol–1 dm3 and α = 0.8 in aqueous buffer, K lactate = 460 mol–1 dm3 and α = 0.8 in artificial sweat, and K lactate = 340 mol–1 dm3 and α = 0.65 in human serum). The result is a selective molecular probe response for lactic acid with LoD = 1.3, 1.4, and 1.8 mM in aqueous buffer media (pH 4.0), in artificial sweat (adjusted to pH 4.7), and in human serum (pH adjusted to 4.0), respectively. The role of the pyrene-appended boronic acid is discussed based on the double layer structure and quantum capacitance changes. In the future, this new type of molecular capacitance sensor could provide selective enzyme-free analysis without analyte consumption for a wider range of analytes and complex environments.

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