A soft and flexible biosensor using a phospholipid polymer for continuous glucose monitoring

A flexible biosensor using a phospholipid polymer to immobilization of glucose oxidase (GOD) was fabricated and tested. At first, an enzyme membrane formed by immobilizing GOD onto a porous polytetrafluoroethylene (PTFE) membrane using the phospholipid polymer (2-methacryloyloxyethyl phosphorylcholine (MPC) copolymerized with 2-ethylhexylmethacrylate (EHMA) : PMEH) was evaluated. According to the result of amperometric measurement, average density of GOD to be immobilized was optimized to 38.9 units cm⁻². Temperature and pH dependences were also investigated. Then, a flexible glucose sensor was fabricated by immobilizing GOD onto a flexible hydrogen peroxide electrode using PMEH. The flexible glucose sensor showed a linear relationship between output currents and glucose concentration in 0.05–1.00 mmol L⁻¹, with a correlation coefficient of 0.999. The calibration range covered the normal tear glucose level of 0.14–0.23 mmol L⁻¹. This indicates that the flexible biosensor is considered to be useful for monitoring of glucose in tear fluids.     

A flexible transcutaneous oxygen sensor using polymer membranes

A wearable and flexible oxygen sensor for transcutaneous blood gas monitoring was fabricated and tested. The sensor has a laminar film-like structure, which was fabricated by pouching KCl electrolyte solution by both non-permeable (metal weldable) sheet and gas-permeable membrane with Pt- and Ag/AgCl-electrodes patterned using microfabrication process. The electrolyte solution was fixed only by heat-sealing the edges of the weldable membranes without any chemical adhesives. The wearable oxygen sensor (thickness: 84 μm) was applied to the electrochemical measurement with a constant potential of −600 mV vs. Ag/AgCl, thus obtaining the calibration range to dissolved oxygen (DO) from 0.0 to 7.0 mg/l with a correlation coefficient of 0.998 and the quick response time (53.4 s to 90% of a steady-state current), which operate similarly to a commercially available oxygen electrode. The sensor was also utilized to transcutaneous oxygen monitoring for healthy human subject. The sensing region of the wearable oxygen sensor was attached onto the forearm-skin surface of the subject inhaling various concentrations of oxygen. As a result of physiological application, the output current was varied from −6.2 μA to −7.8 μA within 2 min when the concentration of inhaling oxygen was changed from atmospheric air to 60% oxygen. Thus, the transcutaneous oxygen was successfully monitored without any inconveniences such as skin inflammation, etc.     

A flow-injection chemiluminescent biomimetic immunoassay method using a molecularly imprinted polymer as a biomimetic antibody for the determination of trichlorfon

In this study, a molecularly imprinted polymer (MIP) was synthesized using trichlorfon as a template molecule. The MIP exhibited a high adsorption capacity toward trichlorfon. Using bovine serum albumin as a carrier, trichlorfon hapten was indirectly labeled with luminol, which competed with free trichlorfon for the combination with a biomimetic antibody of MIP. Based on this direct competitive format, a high throughput flow-injection chemiluminescent biomimetic immunoassay method was developed for fast detection of trace trichlorfon. The influencing factors were investigated and optimized. Under the optimal condition, a lower limit of detection (IC₁₅) of 0.0024?mg/L was obtained using this method. This method was also used to detect the trichlorfon spiked in carrot and cabbage samples, and the results were also verified using the method of gas chromatography.     

A new hydrophilic polymer for biomaterial coatings with low protein adsorption

BIOPOL® polyurethane polymers, an extension of the HYPOL® Polymer series of foamable hydrophilic polymers, have been developed which exhibit improved performance for selected biomedical applications. Members of the BIOPOL polyurethane polymer series, with molecular weights in the range of 7000 to 30000, are larger molecules than HYPOL polymers (MW < 3000) and produce hydrogels, rather than foams, when mixed with water. The prototype material in this series, BIOPOL XP-5, is a liquid prepolymer which chain extends in water and forms a hydrogel which can contain >85% water. The time required for polymerization with water was dependent on the prepolymer : water ratio. This prepolymer was coated onto silica and medical grade tubing and then cured in place with water to form a stable coating which was resistant to non-specific protein binding. In addition, soluble, isocyanate-free forms of the prepolymer were tested for toxicity and shown to produce no adverse effects when injected intravenously into mice or when applied to a chicken chorioallantoic membrane. BIOPOL polymers can be useful in applications where protein adsorption is an undesirable event.     

Poly lactic acid-caprolactone copolymer tube with a denatured skeletal muscle segment inside as a guide for peripheral nerve regeneration: A morphological and electrophysiological evaluation of the regenerated nerves

A biodegradable copolymer of poly L-lactic acid and ε-caprolactone (PLAC) was manufactured into a tube, in which a denatured skeletal muscle segment was placed longitudinally. This model tube was implanted as a guide to promote nerve regeneration across a 5 cm gap in the rabbit sciatic nerve. Five months after implantation, good nerve regeneration was found throughout the graft and in the distal host nerve. The population (29.6/16 x 10^p2 μm^p2) of regenerated nerves in the graft was higher than that of the contralateral normal sciatic nerve (18.0/16 x 10^p2 μm^p2). Regenerated nerve fibers extended to the distal host nerve. The number of myelinated fibers was 13.7/16 x 10^p2 μm^p2 at a level 1.5 cm from the distal suture. The diameters (below 2 μm) of most regenerated myelinated nerves in the graft and in the distal host nerve were much smaller than those (6-8 μm) of normal nerves. Electrophysiological evaluation showed that the hindlimb muscle (gastrocnemius) was innervated by motor nerves in all animals 5 months after implantation. These results indicate that the PLAC tube with a denatured muscle segment inside provided good conditions for nerve fiber regrowth. The PLAC tube is thought to protect the denatured muscle segment from rapid dissociation in the host tissue.