Covalent functionalization and electrochemical tuning of reduced graphene oxide for the bioelectrocatalytic sensing of serum lactate

Abstract

Lactate is a byproduct of glycolysis and serum lactate can be used as non-invasive biomarker to risk-stratifying patients in several life-threatening diseases. Herein, we describe the bioelectrocatalytic sensing of lactate using covalently functionalized reduced graphene oxide (rGO)-based material. The development of lactate biosensor involves the covalent functionalization of rGO with p-nitrophenyl moiety, electrochemical generation of surfaceconfined redox mediator and immobilization of L-lactate dehydrogenase (LDH). The covalently functionalized rGO was characterized by XRD, XPS, FTIR, Raman, resistivity and electrochemical measurements. The covalent attachment of nitrophenyl moiety on the basal plane of the carbon network significantly influences the capacitive property of the rGO.The chemically functionalized rGO was electrochemically tuned to generate the redox mediator (rGO-PhNHOH). Electrochemically generated redox couple (PhNHOH/PhNO) exhibits reversible voltammetric response at ~ -0.06 V with a surface coverage of 7.19±0.26 x 10 -9 molcm -2 . The redox couple efficiently mediates the oxidation of NADH at 0.04 V which is ~600 mV less positive potential than the unmodified electrode. The electrode is highly sensitive towards NADH and it could detect as low as 0.4 µM NADH at the potential of 40 mV in neutral pH without any interference from co-existing bioanalytes. Lactate biosensor was developed using the rGO-PhNHOH functional material and lactate dehydrogenase. The surface-confined redox mediator could successfully detect the enzymatically generated NADH at 40 mV. The biosensor is highly sensitive (10.57±0.38 nAµM -1 cm -2 ) and shows linear response up to 90 µM of Lactate. It could detect lactate as low as 2.5 µM without any interference from other analytes. This biosensor has been successfully used to quantify human serum lactate and the results are in excellent agreement with those obtained by the clinical method.

Cationization of cellulose/polyamide on UV protection, bio‐activity, and electro‐conductivity of graphene oxide‐treated fabric

“…The reduced peak intensity of O1s indicates a decrease in oxygen containing groups and partial restoration of the sp 2 graphitic network as the removal of the oxygen groups suggests the conversion of GO into reduced graphene . The peaks centered at 284.99, 284.95, and 285.00 eV show the binding energy of CC and CC . The N1s spectrum of cationized rGO fabric presents peak centered at 400.54 eV and corresponds to the nitrogen containing groups on the rGO sheets .…”

“…62 The peaks centered at 284.99, 284.95, and 285.00 eV show the binding energy of C@C and CAC. 61,63,64 The N1s spectrum of cationized rGO fabric presents peak centered at 400.54 eV and corresponds to the nitrogen containing groups on the rGO sheets. 64 Cationized rGO fabric after heating showed O1s band which was fitted by a single Gaussian-Lorentzian with peak at 532.80 eV.…”

“…61,63,64 The N1s spectrum of cationized rGO fabric presents peak centered at 400.54 eV and corresponds to the nitrogen containing groups on the rGO sheets. 64 Cationized rGO fabric after heating showed O1s band which was fitted by a single Gaussian-Lorentzian with peak at 532.80 eV. The lower intensity clearly reflects the total amount of oxygen, which was strongly reduced during the experiment whereas the position of the peak is quite close to the one assigned to single-bonded oxygen species.…”

Deposition of nanomaterials: A crucial step in biosensor fabrication

“…In addition, extensive efforts have been made to use the drop-casting method to deposit nanomaterials onto a desired electrode surface for sensing applications that include H2O2 [136][137][138][139][140][141][142][143], dopamine [144][145][146][147][148][149][150][151], uric acid [148][149][150][151][152][153][154][155][156][157][158], ascorbic acid [151,[158][159][160], epinephrine [154], L-glutamic acid [155], urea [70, 161,162], HIV gene detection [163], tryptophan [164], cholesterol [165], miRNA [166,167], cysteine [168], estriol [169], ractopamine [170], lactate [171], and ochratoxin A [172]. Several research groups have reviewed nanomaterial-based nonenzymatic and enzymatic biosen...…”

A Biofuel Cell Based on Biocatalytic Reactions of Lactate on Both Anode and Cathode Electrodes – Extracting Electrical Power from Human Sweat

“…The most recent advances in the design of biofuel cells have been achieved with the use of graphene‐containing materials as the electrode support . These graphene‐containing materials have been actively studied for various bioelectrochemical applications, including lactate biosensing ,,.…”