title: Aluminum gallium nitride (GaN)/GaN high electron mobility transistor-based sensors for glucose detection in exhaled breath condensate.
abstract: BACKGROUND
  Immobilized aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) have shown great potential in the areas of pH, chloride ion, and glucose detection in exhaled breath condensate (EBC). HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. This technology offers the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology of detecting glucose in EBC without the need for clinical visits.
  
  
  METHODS
  HEMT structures, consisting of a 3-microm-thick undoped GaN buffer, 30-A-thick Al(0.3)Ga(0.7)N spacer, and 220-A-thick silicon-doped Al(0.3)Ga(0.7)N cap layer, were used for fabricating the HEMT sensors. The gate area of the pH, chloride ion, and glucose detection was immobilized with scandium oxide (Sc(2)O(3)), silver chloride (AgCl) thin film, and zinc oxide (ZnO) nanorods, respectively.
  
  
  RESULTS
  The Sc(2)O(3)-gated sensor could detect the pH of solutions ranging from 3 to 10 with a resolution of approximately 0.1 pH. A chloride ion detection limit of 10(-8) M was achieved with a HEMT sensor immobilized with the AgCl thin film. The drain-source current of the ZnO nanorod-gated AlGaN/GaN HEMT sensor immobilized with glucose oxidase showed a rapid response of less than 5 seconds when the sensor was exposed to the target glucose in a buffer with a pH value of 7.4. The sensor could detect a wide range of concentrations from 0.5 nM to 125 microM.
  
  
  CONCLUSIONS
  There is great promise for using HEMT-based sensors to enhance the detection sensitivity for glucose detection in EBC. Depending on the immobilized material, HEMT-based sensors can be used for sensing different materials. These electronic detection approaches with rapid response and good repeatability show potential for the investigation of airway pathology. The devices can also be integrated into a wireless data transmission system for remote monitoring applications. This sensor technology could use the exhaled breath condensate to measure the glucose concentration for diabetic applications.
authors.affiliation: Department of Chemical Engineering, University of Florida, Gainesville, Florida, USA.
authors.forename: Byung Hwan
authors.initials: BH
authors.lastname: Chu
authors.forename: Byoung Sam
authors.initials: BS
authors.lastname: Kang
authors.forename: Sheng Chun
authors.initials: SC
authors.lastname: Hung
authors.forename: Ke Hung
authors.initials: KH
authors.lastname: Chen
authors.forename: Fan
authors.initials: F
authors.lastname: Ren
authors.forename: Andrew
authors.initials: A
authors.lastname: Sciullo
authors.forename: Brent P
authors.initials: BP
authors.lastname: Gila
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Pearton
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D001944:Breath Tests / Q000295:instrumentation / Q000379:methods; D003199:Computer Systems; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D004583:Electrons; D045853:Exhalation; D005122:Exudates and Transudates / Q000737:chemistry; D005708:Gallium / Q000737:chemistry*; D005947:Glucose / Q000032:analysis*; D006801:Humans; D008954:Models, Biological; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods; D036103:Nanotechnology; D043942:Nanotubes / Q000737:chemistry; D014173:Transistors, Electronic; D014835:Volatilization
chemical_list: D017607:Aluminum Compounds; C513700:aluminum gallium nitride; C473348:gallium nitride; D005708:Gallium; D005947:Glucose