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Avermectin (AVM) has been widely used in agriculture and animal husbandry on the basis of its broad spectrum of effective anthelmintic activity and specificity targets. However, AVM induction of cytotoxicity through DNA damage is remains elusive. Here we investigate the cytotoxic effects of AVM in human nontarget cells in vitro. We clarify that AVM inhibited the viability of HeLa cells and enhanced apoptosis. We have used alkaline comet assay and γH2AX foci formation to detect DNA damage of HeLa cells. As expected, we found AVM caused DNA double-strand breaks in HeLa cells, as measured by significance of comet assay parameters (e.g., tail DNA) and increases of γH2AX foci in HeLa cells. Moreover, established assays of cytotoxicity were performed to characterize the mechanism of AVM toxicity on HeLa cells. The results demonstrated the collapse of mitochondrial membrane potential, and up-regulating the expression level of Bax/Bcl-2 resulted in a release of cytochrome c into cytosol as well as the activation of caspase-9/-3 and cleavage of poly(ADP-ribose) polymerase (PARP). We conclude that AVM has a potential risk to human health by inducing human cell DNA damage and mitochondria-associated apoptosis.

A surface plasmon resonance sensor based on doublesided polished microstructured optical fiber with hollow core is put forward for refractive index sensing. Two gold films parallel to each other attached to the polished surface act as microfluidic sensing channels for the analyte. The artificially introduced air hole can facilitate the phase matching between the core mode and the plasmon mode. The sensitivities of the proposed sensor are investigated by the wavelength, amplitude and phase interrogation methods when the analyte refractive index increases from 1.33 to 1.34. In contrast to the D-shaped design, the double-sided polished structure demonstrates narrower resonance spectral width and greater phase sensitivity. Moreover, the numerical results indicate that the proposed sensor shows a good stability in the fabrication tolerances of ±5% of the thickness of gold film and the depth of polishing, respectively. Index Terms-Fiber optics sensors, surface plasmon resonance, microstructured optical fiber, refractive index sensors. I. INTRODUCTION S URFACE plasmon resonance (SPR) is the excitation of the surface plasmon coupled with the oscillations of free electron density between the metal and dielectric [1]-[5].

A twin-resonance-coupling phenomenon and the sensing characteristics of a selectively fluid-filled microstructured optical fiber (SFMOF) are proposed and demonstrated. The SFMOF is realized by selectively infiltrating refractive index fluid into a single air hole located at the second ring near the core of the MOF. Twin-resonance dips are observed in the transmission spectrum. Theoretical and experimental investigations reveal that the twin-resonance dips both result from the coupling between LP(01)(C) silica core mode and LP(01)(L) liquid rod mode. Their sensitivities strongly depend on the dispersion curves of the silica and fluid material. Sensitivities of 290 nm/°C (739,796 nm/RIU) and 591.84 nm/N (701.2 pm/µɛ) are achieved, which are the highest for a SFMOF-based device to date, to our best knowledge. Furthermore, the twin-resonance dips appear to shift in the opposite directions with changes in temperature or axial strain, providing a method to achieve two- or multi-parameter measurement in such a compact structure.

A tunable optofluidic microring dye laser within a tapered hollow core microstructured optical fiber was demonstrated. The fiber core was filled with a microfluidic gain medium plug and axially pumped by a nanosecond pulse laser at 532 nm. Strong radial emission and low-threshold lasing (16 nJ/pulse) were achieved. Lasing was achieved around the surface of the microfluidic plug. Laser emission was tuned by changing the liquid surface location along the tapered fiber. The possibility of developing a tunable laser within the tapered simplified hollow core microstructured optical fiber presents opportunities for developing liquid surface position sensors and biomedical analysis.

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A tunable microstructure optical fiber for different orbital angular momentum states generation is proposed and investigated by simulation. The microstructure optical fiber is composed of a high refractive index ring and a hollow core surrounded by four small air holes. The background material of the microstructure fiber is pure silica. The hollow core and the surrounded four small air holes are infiltrated by optical functional material whose refractive index can be modulated via physical parameters, leading to the conversion between circular polarized fundamental mode and different orbital angular momentum states at tunable operating wavelengths. A theoretical model is established and the coupling mechanism is systematically analyzed and investigated based on coupled mode theory. The fiber length can be designed specifically to reach the maximum coupling efficiency for every OAM mode respectively, and can also be fixed at a certain value for several OAM modes generation under tunable refractive index conditions. The proposed fiber coupler is flexible and compact, making it a good candidate for tunable OAM generation and sensing systems.

A compact in-line modal interferometer based on a long period grating (LPG) inscribed in water-filled photonic crystal fiber (PCF) is proposed and demonstrated. The interferometer works from the interference between fundamental core mode and different vector components of LP(11) core mode. The LPG is especially inscribed to realize the energy exchange between the fundamental core mode and different vector components of LP(11) core mode in the PCF. We build a complete theoretical model and systematically analyze the multi-component-intermodal-interference mechanism of the interferometer based on coupled-mode theory. Due to the asymmetric index distribution over the cross section of the PCF caused by CO(2)-laser side illumination, the dispersion curves and temperature sensitivities referring to different vector components of LP(11) core mode are quite different. Thus the interferometer is polarization-dependent and the adjacent interference fringes according to different components of LP(11) mode show greatly discrimination in sensitivities of temperature and strain, making it a good candidate for multiple physics parameters measurements.