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This study aimed to identify N-acylhomoserine lactone (AHL) produced by Hafnia alvei H4, which was isolated from spoiled instant sea cucumber, and to investigate the effect of AHLs on biofilm formation. Two biosensor strains, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens KYC55, were used to detect the quorum sensing (QS) activity of H. alvei H4 and to confirm the existence of AHL-mediated QS system. Thin layer chromatography (TLC) and high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) analysis of the AHLs extracted from the culture supernatant of H. alvei H4 revealed the existence of at least three AHLs: N-hexanoyl-L-homoserine lactone (C6-HSL), N-(3-oxo-octanoyl)-L-homoserine lactone (3-oxo-C8-HSL), and N-butyryl-L-homoserine lactone (C4-HSL). This is the first report of the production of C4-HSL by H. alvei. In order to determine the relationship between the production of AHL by H. alvei H4 and bacterial growth, the β-galactosidase assay was employed to monitor AHL activity during a 48-h growth phase. AHLs production reached a maximum level of 134.6 Miller unites at late log phase (after 18 h) and then decreased to a stable level of about 100 Miller unites. AHL production and bacterial growth displayed a similar trend, suggesting that growth of H. alvei H4 might be regulated by QS. The effect of AHLs on biofilm formation of H. alvei H4 was investigated by adding exogenous AHLs (C4-HSL, C6-HSL and 3-oxo-C8-HSL) to H. alvei H4 culture. Biofilm formation was significantly promoted (p < 0.05) by 5 and 10 µM C6-HSL, inhibited (p < 0.05) by C4-HSL (5 and 10 µM) and 5 µM 3-oxo-C8-HSL, suggesting that QS may have a regulatory role in the biofilm formation of H. alvei H4. [ABSTRACT FROM AUTHOR]

Rod-like Sb2Se3 material prepared by a simple hydrothermal methodwas dispersed with ionic liquid (IL) to construct Sb2Se3/IL/GOx- CPE and Sb2Se3/IL/Cyt c -CPE for the detection of glucose and nitrate (NO- 2, respectively. Moreover, in the chain-type crystal structure of Sb2Se3, strong covalent bond along the c crystallographic axis and much weaker van der Waals bonding between the chains of the layered structure were existed, which facilitated the formation of rod-like Sb2Se3. This was why the rod-like Sb2Se3 could be used to immobilize GOx and Cyt c. With those remarkable advantages such as low cost, satisfactory reproducibility, stability and reliability, the V-VI binary chalcogenides such as rod-like Sb2Se3 material could be an option sensing platform for the extensive application of biosensors. [ABSTRACT FROM AUTHOR]- 2, respectively. Moreover, in the chain-type crystal structure of Sb2Se3, strong covalent bond along the c crystallographic axis and much weaker van der Waals bonding between the chains of the layered structure were existed, which facilitated the formation of rod-like Sb2Se3. This was why the rod-like Sb2Se3 could be used to immobilize GOx and Cyt c. With those remarkable advantages such as low cost, satisfactory reproducibility, stability and reliability, the V-VI binary chalcogenides such as rod-like Sb2Se3 material could be an option sensing platform for the extensive application of biosensors. [ABSTRACT FROM AUTHOR]

Strands of aligned silicon nanowires (SiNWs) with lengths over 2 mm and diameters of 35 nm were synthesized via a two-step controlled growth. The large dimensionality made it possible to fabricate an individual strand of SiNWs into an electrode for cyclic voltammetric detection of bovine serum albumin (BSA). The strand sensor with the immense surface area and electrical conductivity of SiNWs shows the highest sensitivity and widest linear range ever reported for BSA detection. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles (UCNPs) possess several unique features, but they suffer from surface quenching effects caused by the interaction between the UCNPs and fluorophore. Thus, the use of UCNPs for target-induced emission changes for biosensing and bioimaging has been challenging. In this work, fluorophore and UCNPs are effectively separated by a silica transition layer with a thickness of about 4 nm to diminish the surface quenching effect of the UCNPs, allowing a universal and efficient luminescence resonance energy transfer (LRET) ratiometric upconversion luminescence nanoplatform for biosensing applications. A pH-sensitive fluorescein derivative and Hg2+-sensitive rhodamine B were chosen as fluoroionphores to construct the LRET nanoprobes. Both showed satisfactory target-triggered ratiometric upconversion luminescence responses in both solution and live cells, indicating that this strategy may find wide applications in the design of nanoprobes for various biorelated targets. [ABSTRACT FROM AUTHOR]