Center-concave nanosheets of core-shell WO3@Prussian blue based handheld microchip-devices for ultrasensitive lysine determination

Abstract

Lysine is one of the essential amino acids for human body, and its imbalance is a major cause to anemia, aging process, leukemia cell proliferation and tumor growth. Therefore, its monitoring is dominative to the prevention the disease progress and guidance to the clinical treatment. However, traditional in-hospital detection methods, such as colorimetry and fluorometric, often suffer the disadvantages of high cost and long time-consuming. These drawbacks show a difficulty in the home-in and dairy monitoring for the lysine regulation in body. In this study, we have proposed an ultrasensitive microchip-based portable device to achieve the onsite and precise determination of lysine within only 10 s. This microchip was functionalized through constructing a center-concave nanosheet of core-shell WO3@Prussian blue (WO3@PB) to remarkably strengthen the generation and transfer of the detection signal. In this special architecture, the core WO3 nanosheet can be exposed at the center region of this nanocomposite to effectively promote the enzymatic oxidation, while the PB shell enables to strongly reduce the H2O2 produced by the enzymatic reaction. Under above synergetic effects, a handheld device was designed to support the plug-and-play microchip, which performed an outstanding accuracy for the lysine detection in blood.

1. Introduction

Lysine is the second largest amino acid in the world amino acid industry after glutamic acid, and it is also one of the essential amino acids for human body [1]. Lysine is known as one of “lack of amino acids”, which is essential for the human body but cannot be synthesized by themselves [2]. During the human metabolism, lysine is helpful for the absorption of calcium and the protection of the kidney, so it is often used as a nutritional supplement [3]. Lysine is the precursor of carnitine synthesis, and carnitine is necessary for long-chain fatty acids to be transported to mitochondria to produce energy and metabolic functions [4]. Through increasing the release of growth hormone by oral or intravenous injection of lysine, muscle mass would be increased [5e7]. People who don't get enough lysine from their diet will lead to mental and physical retardation [8]. If not treated properly, it may cause other problems, such as loss of appetite, fatigue or emotional changes, nausea, dizziness, hair loss and reproductive system disorders [9]. The level of lysine in blood is related to anemia, aging process, leukemia cell proliferation and tumor growth [10]. Hence, a convenient and precise determination technique and device of lysine is always desired in clinical diagnosis and food industry [11].

At present, the lysine detection often adopts colorimetric method [12,13], mass spectrometry [14], fluorescent probes [15,16] and luminescent sensors [17]. However, these methods have shortcomings such as sample pretreatments, bulky instruments, complex operations, and low sensitivity. Compared with above techniques, the electrochemical biosensor is promising to realize the onsite and rapid detection of lysine due to its fast response, easy miniaturization, and high selectivity [18e21].