CIB2 and CIB3 Regulate Stereocilia Maintenance and Mechanoelectrical Transduction in Mouse Vestibular Hair Cells.

The mechanoelectrical transduction (MET) protein complex in the inner-ear hair cells is essential for hearing and balance perception. Calcium and integrin-binding protein 2 (CIB2) has been reported to be a component of MET complex, and loss of CIB2 completely abolishes MET currents in auditory hair cells, causing profound congenital hearing loss. However, loss of CIB2 does not affect MET currents in vestibular hair cells (VHCs) as well as general balance function. Here, we show that CIB2 and CIB3 act redundantly to regulate MET in VHCs, as MET currents are completely abolished in the VHCs of Cib2/Cib3 double knock-out mice of either sex. Furthermore, we show that Cib2 and Cib3 transcripts have complementary expression patterns in the vestibular maculae, and that they play different roles in stereocilia maintenance in VHCs. Cib2 transcripts are highly expressed in the striolar region, and knock-out of Cib2 affects stereocilia maintenance in striolar VHCs. In contrast, Cib3 transcripts are highly expressed in the extrastriolar region, and knock-out of Cib3 mainly affects stereocilia maintenance in extrastriolar VHCs. Simultaneous knock-out of Cib2 and Cib3 affects stereocilia maintenance in all VHCs and leads to severe balance deficits. Taken together, our present work reveals that CIB2 and CIB3 are important for stereocilia maintenance as well as MET in mouse VHCs.SIGNIFICANCE STATEMENT Calcium and integrin-binding protein 2 (CIB2) is an important component of mechanoelectrical transduction (MET) complex, and loss of CIB2 completely abolishes MET in auditory hair cells. However, MET is unaffected in Cib2 knock-out vestibular hair cells (VHCs). In the present work, we show that CIB3 could compensate for the loss of CIB2 in VHCs, and Cib2/Cib3 double knock-out completely abolishes MET in VHCs. Interestingly, CIB2 and CIB3 could also regulate VHC stereocilia maintenance in a nonredundant way. Cib2 and Cib3 transcripts are highly expressed in the striolar and extrastriolar regions, respectively. Stereocilia maintenance and balance function are differently affected in Cib2 or Cib3 knock-out mice. In conclusion, our data suggest that CIB2 and CIB3 are important for stereocilia maintenance and MET in mouse VHCs.

Highly sensitive visual detection of copper ions based on the shape-dependent LSPR spectroscopy of gold nanorods.

We have developed a novel approach to the rapid visual detection of Cu(2+) in natural samples based on the copper-mediated leaching of gold nanorods (GNRs). In the presence of hexadecyltrimethylammonium bromide, which can reduce the redox potential of Au(I)/Au, the GNRs are catalytically etched by Cu(2+) preferentially along the longitudinal direction. And as a result, the localized surface plasmon resonance extinction peak shifts to short wavelength, accompanied by a color change from blue to red. The leaching mechanism has been carefully discussed in a series of control experiments. Under optimal conditions, this sensor exhibits good sensitivity (LOD = 0.5 nM). Most importantly, the approach is highlighted by its high selectivity for and tolerance of interference, which enables the sensor to detect Cu(2+) directly in a complex matrix, especially in seawater. Moreover, such a nanoparticle-based sensor is also successfully applied to test paper for the visual detection of Cu(2+).

Fluorescent sensing of mercury(II) based on formation of catalytic gold nanoparticles.

A fluorescence assay for the highly sensitive and selective detection of Hg(2+) using a gold nanoparticle (AuNP)-based probe was proposed. The assay was based on the formation of Hg-Au alloys, which accelerated the oxidization of o-phenylenediamine by dissolved oxygen to produce 2,3-diaminophenazine, a fluorescent product.

[Synthesis and theoretical study on fluorescence property of 4- (2-hydroxybenzylideneamino) phenyl ethanone schiff base].

Using salicylaldehyde and 4-aminophenyl ethanone as raw material, a Schiff base derivative 4-(2-hydroxybenzylidene-amino) phenyl ethanone was synthesized by the solid phase reaction method at room temperature. The structure of the product was characterized by elemental analysis and 1 HNMR The UV spectra, fluorescence emission spectra and fluorescence quantum yield of the title Schiff base derivative were investigated. The results showed that this Schiff base displayed superior fluorescence property. The ground state configuration of the title Schiff base was optimized by density functional theory (DFT) method at the B3LYP/6-311G level. After vibrational analysis, there is no imaginary frequency, which indicates that the structure is stable. Then the ground state configuration was optimized to the excited state configuration by the method of single excited interactions CIS. Based on the optimized structure for the ground state and excited state time-dependent density functional theory (TD-DFT) calculations were carried out at the B3LYP/6-31G level to predict the absorption spectra and the fluorescence spectra. The results show that the computed spectra were comparable with the spectra from the experiments. The relationship between the molecular structure and the fluorescence property of 4-(2-hydroxybenzylideneamino) phenyl ethanone was also discussed. The results obtained may provide some theoretical guidance for the design of new fluorescence compounds.

[Theoretical study on geometrical structure and spectrum of 4-(2-nitrobenzylideneamino) phenyl ethanone Schiff base].

The UV absorption spectra, fluorescence emission spectra and fluorescence quantum yield of the title Schiff base were studied by experiment. The results showed that this compound displayed superior fluorescence properties. Geometrical optimization of the title compound was carried out by employing density functional theory (DFT) method at the B3LYP/6-311G(d) level. The calculation results indicated that the title compound has comparatively stronger aromaticity and larger conjugate system. For the optimal configuration, there is no imaginary frequency after vibrational analysis, which indicates that the structure is stable. Based on the optimized structure for the ground state time-dependent density functional theory (TD-DFT) calculations were carried out at the B3LYP/6-311G level to predict the absorption spectra. The single-excitation configuration interaction (CIS) method was used to optimize the structure of the first excited state, and then TD-DFT calculations were carried out to predict the emission spectra. The results indicated that the wavelengths of the absorption and emission spectra are consistent with the experimental data.

Highly sensitive label-free colorimetric sensing of nitrite based on etching of gold nanorods.

A simple colorimetric method with high sensitivity and selectivity was developed for sensing of nitrite as low as 4.0 µM by naked eyes, which is based on etching of gold nanorods accompanied by shape changes in aspect ratios (length/width) and a visible color change from bluish green to red and then to colorless with the increase of nitrite.

Label-free colorimetric sensing of cobalt(II) based on inducing aggregation of thiosulfate stabilized gold nanoparticles in the presence of ethylenediamine.

As a sensitive and selective analytical technique, gold nanoparticles-based colorimetric sensing was characterized by its simplicity and cost-effectiveness. Specific methods have been extensively developed for different targets in diverse samples. In this study, a label-free method for sensing Co(2+) in aqueous solutions was described. The target was achieved by the induced aggregation of thiosulfate (S(2)O(3)(2-)) stabilized gold nanoparticles (AuNPs) in the presence of ethylenediamine (en). Co(2+) first reacted with en and formed complexes of Co(en)(3)(2+) in aqueous solutions, which was followed by the oxidation of Co(en)(3)(2+) to Co(en)(3)(3+) by dissolved oxygen. Co(en)(3)(3+) then attacked S(2)O(3)(2-) ligands adsorbed on the AuNPs' surfaces, forming positively charged (en)(2)CoS(2)O(3)(+) on the AuNPs' surfaces, which reduced the surface charges of AuNPs and induced the aggregation of AuNPs. The process was accompanied by a red-shift in the adsorption spectrum and a visible colour change from wine red to blue. Potential effects of relevant experimental conditions, including pH, concentrations of S(2)O(3)(2-) and en, and incubation time were evaluated for optimization of the method. The proposed method is sensitive (LOD = 0.0 4 µM or 2.36 ppb) and selective (by at least 100-fold over other metal ions except for Cu(2+)) toward Co(2+) with a linear range from 0.1 to 0.7 µM. The cost-effective method allows rapid and simple determination of the concentrations of Co(2+) ions in drinking water.

Label free colorimetric sensing of thiocyanate based on inducing aggregation of Tween 20-stabilized gold nanoparticles.

Based on inducing the aggregation of gold nanoparticles (AuNPs), a simple colorimetric method with high sensitivity and selectivity was developed for the sensing of thiocyanate (SCN(-)) in aqueous solutions. Citrate-capped AuNPs were prepared following a classic method and Tween 20 was subsequently added as a stabilizer. With the addition of SCN(-), citrate ions on AuNPs surfaces were replaced due to the high affinity between SCN(-) and Au. As a result, Tween 20 molecules adsorbed on the AuNPs surfaces were separated and the AuNPs aggregated. The process was accompanied by a visible color change from red to blue within 5 min. The sensing of SCN(-) can therefore be easily achieved by a UV-vis spectrophotometer or even by the naked eye. The potential effects of relevant experimental conditions, including concentration of Tween 20, pH, incubation temperature and time, were evaluated to optimize the method. Under optimized conditions, this method yields excellent sensitivity (LOD = 0.2 µM or 11.6 ppb) and selectivity toward SCN(-). Our attempt may provide a cost-effective, rapid and simple solution to the inspection of SCN(-) ions in saliva and environmental aqueous samples.

BAIAP2L2 Inactivation Does Not Affect Stereocilia Development or Maintenance in Vestibular Hair Cells.

Hair cells are mechanosensitive cells in the inner ear, characterized by dozens to hundreds of actin-based stereocilia and one tubulin-based kinocilium on the apical surface of each cell. Two types of hair cells, namely cochlear hair cells and vestibular hair cells (VHCs), are responsible for the sensation of sound and balancing information, respectively. In each hair cell, the stereocilia are organized into rows of increasing heights with the mechano-electrical transduction (MET) channels localized at the tips of shorter-row stereocilia. A so-called "row 2 protein complex" also localizes at the tips of shorter-row mechanotransducing stereocilia, which plays important roles in the maintenance of mechanotransducing stereocilia. Recently, we and others identified BAIAP2L2 as a new component of row 2 complex. Baiap2l2 inactivation causes degeneration of the mechanotransducing stereocilia in cochlear hair cells, and leads to profound hearing loss in mice. In the present work, we examined the role of BAIAP2L2 in the VHC stereocilia. Confocal microscopy reveals that BAIAP2L2 immunoreactivity is localized at the tips of shorter-row stereocilia in VHCs. However, stereocilia development and maintenance are unaffected in Baiap2l2-/- VHCs. Meanwhile, MET function of VHCs as well as vestibular functions are also unaffected in Baiap2l2-/- mice. Further investigations show that the stereociliary tip localization of CAPZB2, another known row 2 complex component, is not affected in Baiap2l2-/- VHCs, consistent with the unaltered stereocilia morphology. Taken together, our present data show that BAIAP2L2 inactivation does not affect vestibular hair cell stereocilia.

On-site visual detection of hydrogen sulfide in air based on enhancing the stability of gold nanoparticles.

We have described a simple and low-cost visual method for on-site detection of hydrogen sulfide (H2S) in air based on the antiaggregation of gold nanoparticles (AuNPs). The bubbling of H2S into a weak alkaline buffer solution leads to the formation of HS-, which can stabilize the AuNPs and ensure the AuNPs maintain their red color even in a Tris buffer solution containing 80 mM NaCl with the presence of Tween 80. The stabilization of the AuNPs is attributed to the adsorption of negatively charged S2- on the AuNPs surface. In contrast, without the bubbling of H2S, AuNPs aggregate and change color from red to blue. Under optimal conditions, the proposed method exhibits excellent visual sensitivity with a naked-eye detectable limit of 0.5 ppm (v/v), making the on-site detection of H2S possible. This method also possesses good selectivity toward H2S over other gases by using a simple SO2 removal device. The successful determination of the concentrations of H2S in local air indicates the potential application of this cost-effective method.

Colorimetric sensing of copper(II) based on catalytic etching of gold nanoparticles.

Based on the catalytic etching of gold nanoparticles (AuNPs), a label-free colorimetric probe was developed for the detection of Cu(2+) in aqueous solutions. AuNPs were first stabilized by hexadecyltrimethylammonium bromide in NH3-NH4Cl (0.6M/0.1M) solutions. Then thiosulfate (S2O3(2-)) ions were introduced and AuNPs were gradually dissolved by dissolved oxygen. With the further addition of Cu(2+), Cu(NH3)4(2+) oxidized AuNPs to produce Au(S2O3)2(3-) and Cu(S2O3)3(5-), while the later was oxid-ized to Cu(NH3)4(2+) again by dissolved oxygen. The dissolving rate of AuNPs was thereby remarkably promoted and Cu(2+) acted as the catalyst. The process went on due to the sufficient supply of dissolved oxygen and AuNPs were rapidly etched. Meanwhile, a visible color change from red to colorless was observed. Subsequent tests confirmed such a non-aggregation-based method as a sensitive (LOD=5.0 nM or 0.32 ppb) and selective (at least 100-fold over other metal ions except for Pb(2+) and Mn(2+)) way for the detection of Cu(2+) (linear range, 10-80 nM). Moreover, our results show that the color change induced by 40 nM Cu(2+) can be easily observed by naked eyes, which is particularly applicable to fast on-site investigations.