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Owing to the importance of α‐amylase in industry, it is necessary to develop a more simple and practical approach to measure α‐amylase activity. Herein, a fluorescence method was established for the detection of α‐amylase activity based on hydroxyproply‐β‐cyclodextrin‐curcumin inclusion complex (HP‐β‐CDs‐Cur). Curcumin was utilized as a signal probe, while hydroxyproply‐β‐cyclodextrin (HP‐β‐CDs) was employed both as a substrate of α‐amylase and the carrier of curcumin. α‐amylase is capable to hydrolyse α‐1,4‐glycosidic bond on the HP‐β‐CDs ring, facilitating the detection of its activity through the measurement of the decrease of fluorescence intensity caused by the release of curcumin into the aqueous. The results showed that there was a good linear relationship between fluorescence intensity and α‐amylase concentration in the range of 0.065~1.365 U mL−1, and the detection limit was 0.0065 U mL−1. The successful application of this method to evaluate the activities of multiple commercial α‐amylases underscores its robustness and reliability. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowhiskers were fabricated in a [bmim][BF4] ionic liquid. The minimal size of the nanowhiskers is only 0.2 nm, and the size matches the thickness of a PEDOT single-molecular chain. They were successfully used as the electron transfer channels between the active center of hemoglobin (Hb) and an underlying electrode. The direct electron transfer process between Hb and the underlying electrode was realized without any electron mediator. Compared to that of a gold nanoparticle (AuNP)–Hb composite electrode, the catalytic current of a PEDOT nanowhiskers–AuNPs–Hb composite electrode for detecting H2O2 is increased 7 fold. A novel model of a H2O2 biosensor based on the PEDOT nanowhiskers–AuNPs–Hb composites was fabricated. The detection limit was estimated to be 0.6 μM at a signal/noise (S/N) ratio of 3, and the linear range of H2O2 concentration was from 1 μM to 1100 μM. Three constructed models of the biosensors showed a good stability, and all of them retained nearly 90% of their initial signals for 1 mM H2O2 when they were stored at 4 °C after 60 days. H2O2 concentration in contact lens nursing liquid was measured by the biosensor, and the results were in good agreement with the values provided by the supplier. It is shown that the PEDOT nanowhiskers can provide a new opportunity for the design of sensitive biosensors with long-term stability. [ABSTRACT FROM AUTHOR]

Lipase is a neglected enzyme in the field of gold nanoparticle-based enzyme assays. This paper reports a novel colorimetric probe to rapidly visualize lipase activities by using Tween 20 functioned GNPs (Tween 20-GNPs) as a reporter. The present strategy hence could overcome the limitations caused by the heterogeneous interface in lipase assay. Catalytic hydrolytic cleavage of the ester bond in Tween 20-GNPs by lipase will trigger the rapid aggregation of GNPs at a high salt solution. The color change from red to purple could be used to sense the activity of lipase. The detection limit (3σ) is as low as 2.8 × 10-2 mg/mL. A preliminary enzyme activity screening was carried out for seven commercially purchased lipase samples. It also has been successfully applied to detecting lipase in fermentation broth of Bacillus subtilis without any pretreatment.

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowhiskers were fabricated in a [bmim][BF 4 ] ionic liquid. The minimal size of the nanowhiskers is only 0.2 nm, and the size matches the thickness of a PEDOT single-molecular chain. They were successfully used as the electron transfer channels between the active center of hemoglobin (Hb) and an underlying electrode. The direct electron transfer process between Hb and the underlying electrode was realized without any electron mediator. Compared to that of a gold nanoparticle (AuNP)-Hb composite electrode, the catalytic current of a PEDOT nanowhiskers-AuNPs-Hb composite electrode for detecting H 2 O 2 is increased 7 fold. A novel model of a H 2 O 2 biosensor based on the PEDOT nanowhiskers-AuNPs-Hb composites was fabricated. The detection limit was estimated to be 0.6 μM at a signal/noise (S/N) ratio of 3, and the linear range of H 2 O 2 concentration was from 1 μM to 1100 μM. Three constructed models of the biosensors showed a good stability, and all of them retained nearly 90% of their initial signals for 1 mM H 2 O 2 when they were stored at 4 °C after 60 days. H 2 O 2 concentration in contact lens nursing liquid was measured by the biosensor, and the results were in good agreement with the values provided by the supplier. It is shown that the PEDOT nanowhiskers can provide a new opportunity for the design of sensitive biosensors with long-term stability.

A novel electrochemical biosensing strategy based on a three-dimensional fishnet of DNA-linked nanoparticle supramolecular structure triggered by the analyst for detection of Hg(2+) has been designed. The detection limit is 7.38 pM and the sensor's selectivity and facility have been significantly improved.