Abstract
Lactate detection by an in situ sensor is of great need in clinical medicine, food processing, and athletic performance monitoring. In this paper, a flexible, easy to fabricate, and low-cost biosensor base on lactate oxidase is presented. The fabrication processes, including metal deposition, sol-gel IrOx deposition, and drop-dry enzyme loading method, are described in detail. The loaded enzyme was examined by scanning electron microscopy. Cyclic voltammetry was used to characterize the sensors. Durability, sensibility, and selectivity of the biosensors were examined. The comparison for different electrode sizes and different sensing film materials was conducted. The sensor could last for four weeks with an average surface area normalized sensitivity of 950 nA/(cm2 mM) and 9250 nA/(cm2 mM) for Au-based electrodes, and IrOx-modified electrodes respectively, both with an electrode size of 100 × 50 μm. The self-referencing method to record noises simultaneously with the working electrode greatly improved sensor sensitivity and selectivity. The sensor showed little response to interference chemicals, such as glutamate and dopamine.
Highlights
Lactate is a common analyte due to its wide variety of applications
Transient lactic acidosis can occur due to excessive lactate production from tissue hypoxia or increased cellular metabolism caused by strenuous exercise [10,11,12]
We propose a flexible, lightweight, micro-sized lactate sensor which can be integrated to our previously demonstrated wearable wireless module for data transduction [33]
Summary
Lactate is a common analyte due to its wide variety of applications. In the field of food processing, L-lactate is present in the fermentation of cheese, yoghurt, butter, pickles, sauerkraut, and other food products [1,2]. Schabmueller et al demonstrated a micromachined lactate sensor using a titanium-latinum working electrode and titanium-platinum-iridium oxide reference electrode on a double-sided silicon-on-insulator wafer [23]. Elie et al demonstrated an amperometric sensor with arrayed platinum electrodes on a glass substrate, with linearity up to 90 mM lactate [26]. Revzin et al have demonstrated a lactate/glucose/pyruvate sensor array using deposited gold electrodes on a Mylar substrate. Weltin et al have demonstrated a lactate and glutamate sensor using a deposited platinum/titanium electrode on polyimide foil [29]. We propose a flexible, lightweight, micro-sized lactate sensor which can be integrated to our previously demonstrated wearable wireless module for data transduction [33]. To further improve the sensor performance, we modify the working electrode with the inert and bio-compatible material iridium oxide. The sensor could be used for a variety of test-and-dispose applications, such as food processing tests, daily ex vivo tests for patients, infants, and seniors, and emergency response use, without causing secondary pollution to the subjects
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