Refractive index sensor with asymmetrical tapered fiber based on evanescent field sensing

We report and demonstrate a single-mode asymmetric tapered fiber as a refractive index (RI) sensor based on evanescent field sensing. The proposed setup managed to sense the changes of RI when the tapered region was exposed to different concentrations of Sodium chloride (NaCl). This was possible due to the output interference spectrum shifting in response to the changes of RI. Different environmental sensitivities were achieved by manipulating the transition lengths of the tapered fiber. Experimental results depict RI sensitivities of 3914.7 nm/RIU (refractive index unit) and 3395.7 nm/RIU for taper profiles with down-taper transition lengths of 2 mm and 8 mm, respectively, which is higher than previously reported asymmetric taper RI sensors. Such findings may find itself beneficial in low cost, reliable and simplified sensors

Tapered multimode fiber sensor for salinity detection

A tapered multimode fiber as a salinity sensor was demonstrated. The sensitivity of the sensor could be enhanced by tapering the multimode fiber to a 10μm diameter size and 50mm of waist length. The tapered multimode fiber sensor was tested with the different concentration of sodium chloride (NaCl) which is diluted in the distilled water. The tapered multimode fiber sensor (TMFS) is easy to fabricate, compact, and simple. The sensitivity of the sensor achieved 0.1705 a.u/M. The findings demonstrated the capability of TMFS for salinity sensing and its potential application for detection of chemical sample

Sensitive and specific protein sensing using single-mode tapered fiber immobilized with biorecognition molecules

We examine and demonstrate a biosensor using single-mode tapered fiber that has been immobilized with biorecognition molecules to sense targeted proteins. Interaction of evanescent waves with the external medium surrounding the tapered region produces an interferometric-patterned spectrum, which shifts correspondingly to any changes of refractive index (RI) in the external medium. The proposed setup managed to obtain an RI sensitivity and concentration sensitivity of 2526.8 nm/RIU and 20.368 nm/μM, respectively, which, to our knowledge, is highly sensitive when compared with previous studies. The dynamic performance, good specificity, and high sensitivity of the proposed method highlight an immensely beneficial choice for immunological diagnostics

Label-free dengue E protein detection using a functionalized tapered optical fiber sensor

The surge of Dengue cases around the globe has intensified the demand for a reliable diagnostic method. The work demonstrates, to the best of our knowledge, the first label-free optical based sensor for detection of Dengue II E proteins. This was achieved by utilizing tapered optical fiber that has been functionalized with complementary recombinant antibodies. The fundamental concept of the sensor relies on the interaction between strong evanescent waves resulting from the dimensional change of the fiber and immune complex formed on the surface of the fiber when the virus is present. Sensitivity and detection limit values obtained with the sensor setup are 5.02 nm/nM and 1 pM, respectively, with a standard deviation value of no more than ±0.4. The compact and rapid sensor is a viable alternative for label-free and quantitative assessment of the infection, which may assist in providing better clinical management and understanding of the disease

Interaction between abomasal blood feeder Haemonchus contortus and intestinal mucosal browser Trichostrongylus colubriformis during co-infection in Boer goats

This study was conducted to investigate potential interactions between the abomasal blood feeder Haemonchus contortus and the intestinal mucosal browser Trichostrongylus colubriformis among deliberately infected Boer goats. Faecal and blood samples were collected twice a week for eight weeks from 25 parasite-naïve goats. Correlation analysis and multiple linear regression models were conducted to explore the association between phenotypic variables and variables taken at necropsy. Positive associations were identified between total FEC and log T. colubriformis number (r = 0.62, p < 0.05) as well as between IgA and peripheral eosinophil counts (r = 0.65, p < 0.05). A negative correlation was observed between T. colubriformis and log H. contortus number (r=-0.56, p < 0.05). Multiple linear regression models show that H. contortus and T. colubriformis interacted with each other. T. colubriformis appeared to contribute more significantly to the variation of FEC than H. contortus. Co-infection induced an IgA response which was only effective against T. colubriformis but not protective against H. contortus infection. This could be seen via significant associations of IgA with both nematode species but with the effect of IgA differing for H. contortus and T. colubriformis. In this study, H. contortus infection was not detrimental to the goats with no observed impact on PCV. This could be because the growth of T. colubriformis as represented by its length was associated with reduced number and composite burden of H. contortus during co-infection, or possibly due to low infection dosage. Improved understanding of the impact of H. contortus and T. colubriformis and their interaction from natural co-infection studies is beneficial for a better understanding of the goat-parasite interaction and its potential impacts on the health and productivity of animals

Endoscopy gender determination and reproductive hormone profiles of Painted Terrapins (<i>Batagur borneoensis</i>) subjected to <i>ex situ</i> incubation

Chelonian exhibit temperature dependent sex determination, and ex situ incubation of eggs in conservation hatcheries may render a gender bias. The gender of juvenile Painted terrapins (Batagur borneoensis) produced at a conservation hatchery in Malaysia was determined by endoscopy of the gonads. Circulating reproductive hormones (testosterone, progesterone and estradiol) were profiled for 31 juveniles and nine captive-reared non-breeding adult terrapins. Endoscopy revealed a gender bias of 96.8% (30/31) females. Testosterone levels in the juvenile females (2.49 ± 1.29) were significantly lower than that of the adult females (12.20 ± 4.29), and lower than values in the juvenile male (9.36) and adult males (27.60, 35.62). The progesterone levels in the juvenile females (107.12 ± 68.68) were significantly higher than that of the adult females (51.13 ± 24.67), but lower than values in the juvenile male (33.27) and adult males (3.43, 8.51). Estrogen levels were significantly lower in the juvenile females (1.57 ± 1.35) compared to the adult females (77.46 ± 53.45). Negative correlations were observed between levels of progesterone and testosterone, and progesterone and estrogen. A positive correlation was noted between estrogen and testosterone. The present study constitutes the first attempt to determine the gender and reproductive hormone profiles of juvenile Painted terrapins produced by ex situ incubation, and captive non-breeding adults. Endoscopy of the gonads is a useful techniques for gender determination among juvenile turtles, while the use of testosterone as a gender biomarker warrants further investigation