Detecting Glucose Levels in Blood Plasma and Artificial Tear by Au(I) Complex on the Carbopol Polymer: A Microfluidic Paper-Based Method.

We report on a selective paper-based method and a microfluidic paper-based analytical device (µPAD) for the detection of human plasma glucose and tear glucose using carbopol polymer-encapsulated Au(I) complex (AuC2C6H4OMe)2(Ph2P(C6H4)3PPh2), (B5). To the best of our knowledge, this demonstrates for the first time the glucose sensing based on dual emission, i.e., fluorescence and phosphorescence, of a single type molecule on the carbopol polymer. Upon addition of human blood treated with anticoagulants to µPADs, plasma is separated from the blood and flows into the response region of the µPADs to react with carbopol polymer-encapsulated B5, in which the ratiometric luminescence is analyzed. The plasma glucose concentration can be quantitively detected at 1.0⁻50.0 mM on paper, and tear glucose can be detected at 0.1⁻4.0 mM on µPADs. Owing to the structural design, this device has superior ratiometric changes of dual emission over other Au(I) complexes for signal transduction. The encapsulation of carbopol polymer also offers long-term storage stability. In tear measurement, carbopol polymer is not only used to encapsulate enzyme to remain the enzyme's activity, but also played as a glue (or media) to connect microfluidic channel and response region. This further improves the sensitivity and limit of detection for glucose. Moreover, this sensor provides a faster response time, a wider range for glucose sensing than reported previously, and no statistical difference of the data from a commercial glucometer, allowing for practical diagnosis of diabetes and healthy individuals.

Ag@Au nanoprism-metal organic framework-based paper for extending the glucose sensing range in human serum and urine.

In this work, we present a Ag@Au nanoprism-metal-organic framework-paper based glucose sensor for rapid, sensitive, single-use and quantitative glucose determination in human serum. To achieve painless measurement of glucose with a non-invasive detection methodology, this biosensor was further tested in human urine. In this approach, a new hybrid-Ag@Au nanoprism loaded in close proximity to micrometer sized coordination polymers as phosphorescent luminophores significantly enhanced the emission intensity due to metal-enhanced phosphorescence and worked as reaction sites to support more dissolved oxygen. Reports of enhanced phosphorescence intensity are relatively rare, especially at room temperature. The true enhancement factor of Ag@Au-phosphorescent metal-organic frameworks on paper was deduced to be 110-fold, making it a better optical type glucose meter. The results demonstrate the validity of the intensity enhancement effect of the excitation of the overlap of the emission band of a luminophore with the surface plasmon resonance band of Ag@Au nanoprisms. Ag@Au nanoprisms were used not only to improve the detection limit of glucose sensing but also to extend the glucose sensing range by enhancing the oxygen oxidation efficiency. The oxidation of glucose as glucose oxidase is accompanied by oxygen consumption, which increases the intensity of the phosphorescence emission. The turn-on type paper-based biosensor exhibits a rapid response (0.5 s), a low detection limit (0.038 mM), and a wide linear range (30 mM to 0.05 mM), as well as good anti-interference, long-term longevity and reproducibility. Finally, the biosensor was successfully applied to the determination of glucose in human serum and urine.