Carbon nanotube enhanced mediator-type biosensor for real-time monitoring of glucose concentrations in fish

A Self-Powered Glucose Biosensor Operated Underwater to Monitor Physiological Status of Free-Swimming Fish

The changes in blood glucose levels are a key indicator of fish health conditions and are closely correlated to their stress levels. Here, we developed a self-powered glucose biosensor (SPGB) consisting of a needle-type enzymatic biofuel cell (N-EFC), which was operated underwater and connected to a charge pump integrated circuit (IC) and a light emitting diode (LED) as the indicator. The N-EFC consisted of a needle bioanode, which was inserted into the caudal area of a living fish (Tilapia) to access biofuels, and a gas-diffusion biocathode sealed in an airtight bag. The N-EFC was immersed entirely in the water and connected to a charge pump IC with a capacitor, which enabled charging and discharging of the bioelectricity generated from the N-EFC to blink an LED. Using a smartphone, the glucose concentration can be determined by observing the LED blinking frequencies that are linearly proportional to the blood glucose concentration within a detection range of 10–180 mg/dL. We have successfully demonstrated the feasibility of the SPGB used to continuously monitor the physiological status of free-swimming fish treated with cold shock in real time. The power generated by a free-swimming fish with an N-EFC inserted into its caudal area, swimming in a fish tank with a water temperature (Tw) of 25 °C, exhibited an open circuit voltage of 0.41 V and a maximum power density of 6.3 μW/cm2 at 0.25 V with a current density of 25 μA/cm2. By gradually decreasing Tw from 25 °C to 15 °C, the power generation increased to a maximum power density of 8.6 μW/cm2 at 0.27 V with a current density of 31 μA/cm2. The blood glucose levels of the free-swimming fish at 25 °C and 15 °C determined by the blinking frequencies were 44 mg/dL and 98 mg/dL, respectively. Our proposed SPGB provides an effective power-free method for stress visualization and evaluation of fish health by monitoring a blinking LED through a smartphone.

Development of supported liquid-phase microextraction probes for in vivo PK studies

BACKGROUND

A new sample preparation method termed supported liquid-phase microextraction is proposed. With this technique, the extraction phase is a liquid immobilized inside the pores of a membrane coated on a solid support.

METHODOLOGY

Supported liquid-phase microextraction probes were prepared by coating wires with porous polyacrylonitrile followed by saturation with 1-octanol. The probes were introduced inside hypodermic needles and used for in vivo extraction of oxybutynin from the blood and tissues of rabbits. The linear range of the method was from 0.5 to 500 ng/ml.

CONCLUSION

The proposed method was successfully applied to monitor the PK profile of oxybutynin. The drug followed a two-compartment model, with a volume of distribution of 14 l/kg and a half-life of 76 min.