Sonochemically Synthesized ZnO Nanostructure-Based L-Lactate Enzymatic Sensors on Flexible Substrates
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.76
Sonochemically Synthesized ZnO NanostructureBased L-Lactate Enzymatic Sensors on Flexible Substrates
Fahmida Alam, Ahmed Hasnain Jalal, Raju Sinha, Yogeswaran Umasankar, Shekhar Bhansali, Nezih Pala Department of Electrical and Computer Engineering, Florida International University, Miami, Florida – 33174, United States.
ABSTRACT
We report on highly sensitive and flexible L-lactate enzymatic sensors. The sensing materials of this biosensor, two-dimensional (2D) zinc oxide nanoflakes (ZnO NFs), are synthesized on flexible gold(Au)-coated polyethylene terephthalate (PET) substrate using one step sonochemical approach for non-invasive lactate monitoring in human perspiration. ZnO NFs show high isoelectric points (IEP) and biocompatibility. Taking advantage of these unique properties, we immobilized Lactate oxidase (LOx) on the synthesized ZnO NFs. PET/Au/ZnO NFs sensors demonstrated detection of lactate in the range of 10 pM-10 μM for the electrode area of 0.5×0.5 cm2. The sensitivity of this linker free lactate sensor was found 2.23 ȣA/M /cm2 and shows 4 times better response than conventional Au electrode with linker.
INTRODUCTION Lactic acid (2-Hydroxypropanoic acid) is produced from pyruvic acid (PA) under anaerobic conditions in different organs such as skeletal muscles, brain and kidney. Production of lactate occurs in all skeletal tissues of the body with removal through metabolism and reconversion to pyruvate in oxygen rich environments [1]. Without proper removal through the kidney and liver, its accretion leads to increased concentrations in the blood causing lactic acidosis. Being a key molecule in the anaerobic energy system of humans, lactate is primarily considered as a biomarker for
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tissue oxidative stress when the energy demands of tissues cannot be met under normal aerobic conditions. Excess lactate in the body causes sepsis, anemia, hematoma, malignancy, diabetes, lever disease [2], endotoxic [3], system disorders, tissue hypoxia [4,5] ischemia, respiratory failure [6], renal failure and even arthritis. Monitoring of blood lactate levels has been seen to improve identification of patients requiring resuscitative care (93%) when compared to standard blood pressure monitoring (67%) [7]. Therefore, continuous lactate monitoring is integral to systemic healthcare in military and high-risk personnel [7], in clinical emergencies, sports, and general medicine. In intensive care units and operating rooms, lactate levels may act as an alarm signal for the diagnosis of patient conditions [8]. Different methods have been devised for lactate monitoring such as potentiometry, amperometry, chemiluminescence, microwave sensing and magnetic resonance spectroscopy. But for the reasons of simplici
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