In order to open up a new application field of zinc oxide (ZnO), characteristics of polycrystalline ZnO‐based ion‐sensitive field‐effect transistors (ISFETs) and FET‐type biosensors are studied. These solution‐gate FETs were composed of a layered structure on a glass substrate; amorphous tantalum pentoxide (Ta2O5) for the gate insulator/polycrystalline ZnO doped with indium (ZnO:In) for the channel layer/glass substrate. The Ta2O5/ZnO:In bilayer was deposited by a newly developed facing‐target sputtering (FTS) method to reduce the damage on the depositing film by the bombardment of gamma electrons and negatively charged ions. The advantage of FTS, high‐quality film growth with sharp interface, enabled the use of such thin layers as 8‐nm‐thick Ta2O5 and 35‐nm‐thick ZnO:In for the ISFETs with acceptable performance. The ZnO‐based ISFET showed high pH sensitivity and high stability comparable to commercially available silicon‐based ISFETs with much lower photo‐induced error under visible‐ray illumination. By modifying biofunctional molecules on the gate electrode, the application of the ZnO‐based ISFET to two types of biosensors was demonstrated. One is an aptamer‐immobilized immuno FET specific for human immunoglobulin detection, and the other is a glucose oxidase‐immobilized enzyme FET for β‐D glucose detection. Both of the former and latter FET‐type biosensors showed high sensitivities in accordance with the Langmuir isotherm plot corresponding to monolayer absorption. These results stay at the preliminary stage at present, however, by considering the easy integration of these solution‐gate FETs on a chip, it is concluded that micro total analysis system chips for clinical use are promising application fields for ZnO devices as an ecologically and economically favorable semiconductor in the next generation.
The characteristics of an aptamer-modified Ta 2 O 5 /ZnO field-effect transistor as a prototype label-free immunosensor for the potentiometric electrical detection of immunoglobulin G (IgG) were studied. The Ta 2 O 5 /ZnO film was grown on a glass substrate by a facing-target sputtering method. Stable operation in electrolyte solution with a small hysteresis width and a low gate leakage current was realized. The immunosensor exhibited a proportional sensitivity to the logarithmic human IgG concentration in the range of 0.35-23 µmol&dm %3 with a rapid response time of >15 s.
Background Tracheal stenosis is a life-threatening condition, and management of a patient with a risk of tracheal stenosis is challenging for anesthesiologists. In this report, we describe a method for airway management using two gum elastic bougie method when removing a tracheal stent via a tracheostomy orifice with a risk of airway restenosis. Case presentation A 71-year-old man had an enlarged squamous cell carcinoma of the lung invading the upper mediastinum that had caused severe stenosis of the trachea. Two months after diagnosis, a tracheal stent had been placed to maintain tracheal patency. One month after stent placement, acute respiratory failure was induced by upper airway obstruction caused by subglottic airway edema due to mechanical stimulation of the cranial end of the stent, and the patient was rescued by oral tracheal intubation. Tracheal stent extraction was scheduled to relieve the laryngeal edema. Since there was a risk of tracheal restenosis because of the possibility of accidental evulsion of the orally tracheal tube which intubated to secure an emergency airway and tracheal stent extraction, two gum elastic bougies were inserted through the oral tracheal tube and tracheostomy orifice to facilitate re-intubation. After extraction of the tracheal stent, airway openness was maintained and tracheostomy was completed without any complication. Conclusion Successful management of tracheal stent extraction was performed using a double gum elastic bougie technique.
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