br Introduction Glucose is the most widely

Introduction Glucose is the most widely distributed monosaccharide in nature and plays a very important role in the fields of life science [1], biology [2–4], clinical analysis [5], and food industry [6]. As a major source of prolyl hydroxylase inhibitor for living cells, the glucose acts as an indispensable metabolic intermediate in various metabolic processes of animals and plants. Furthermore, an abnormal glucose level in human blood or urine is commonly considered as a sign of diabetes or hypoglycemia [7]. Thus, rapid and accurate determination of glucose level in human blood and urine is essential for diagnosis and management of diabetes, which is affecting about 150 million people worldwide [8]. Millions of diabetics need a daily test of blood glucose level, which made the glucose become the most commonly tested analyte. Glucose oxidase (GOD) is widely applied to optical and electrochemical determination of glucose based on the enzyme-catalyzed oxidation mechanism [9–14], but phosphorescence-based detection of blood glucose is not very common [15–18]. Quantum dots (QDs) and GOD were connected through a coupling agent to construct glucose detection sensors [18,19], which were based on the fact that H2O2 can quench QDs. Generally speaking, these sensors require complex conjugation between QDs and GOD, which may damage the properties or functions of QDs and GOD in different degrees. Meanwhile, the tedious process and high sample consumption may limit their practical application. In this study, we constructed a rapid and sensitive detection of glucose by using room-temperature phosphorescent (RTP) QDs without conjugation between QDs and GOD. Complex pretreatments are not required in this method, and a great potential for glucose detection was indicated as it was free from the interference of autofluorescence and scattering light. As so much focus is given to RTP QDs detection recently, it is widely applied to the fields of sensors, especially biomolecular sensors [18,20–31]. Owing to the longer lifetime of phosphorescence than fluorescence, RTP QDs detection shows high reliability and stability without the interference from autofluorescence or scattered light [18,20,22,23]. Moreover, the detection selectivity can be further enhanced since the phosphorescence is not as common as fluorescence [21]. Bright prospect is shown in the development of RTP sensors [18,20–31], any other complicated sample pretreatments are not required for developed biosensors [18,22,28]. In this paper, we reported an RTP glucose detection method without conjugation GOD with QDs based on the principle as follows: GOD decomposed glucose and released H2O2, then H2O2 obtained electrons from 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS QDs to form H2O and O2, finally, quenched RTP of MPA-capped Mn-doped ZnS QDs via Photoinduced Electron Transfer (PIET) (Fig. 1), thus a new method was established for quantitative detection of glucose accordingly, which can be used to detect glucose in biological fluids.
Experimental
Results and discussion
Conclusions In this paper, room-temperature phosphorescent (RTP) detection of glucose was realized without conjugation between GOD and quantum dots (QDs). Sophisticated conjugation is not required in this method, which can avoid the interference from autofluorescence and scattered light in biological fluids. GOD specifically decomposed the glucose and released H2O2, and then quenched the phosphorescence of MPA-capped Mn-doped ZnS QDs through Photoinduced Electron Transfer (PIET) process. MPA-capped Mn-doped ZnS QDs can be used in quantitative detection of glucose via the quenching of RTP. Thus, a new method for glucose detection was built on these bases consequently. The sensor for glucose has a detection limit of 0.0029mM and two linear ranges from 0.005 to 0.1mM and from 0.1 to 0.4mM. Combined the advantage of other nanomaterials-based glucose detection methods, which including simple operation, high sensitivity and no interference from the background fluorescence of biological fluids, the glucose detection ability was improved, which further certificated that this method can be used to detect the glucose content in body fluid.