title: Enhancing the sensitivity of needle-implantable electrochemical glucose sensors via surface rebuilding.
abstract: OBJECTIVE
  Needle-implantable sensors have shown to provide reliable continuous glucose monitoring for diabetes management. In order to reduce tissue injury during sensor implantation, there is a constant need for device size reduction, which imposes challenges in terms of sensitivity and reliability, as part of decreasing signal-to-noise and increasing layer complexity. Herein, we report sensitivity enhancement via electrochemical surface rebuilding of the working electrode (WE), which creates a three-dimensional nanoporous configuration with increased surface area.
  
  
  METHODS
  The gold WE was electrochemically rebuilt to render its surface nanoporous followed by decoration with platinum nanoparticles. The efficacy of such process was studied using sensor sensitivity against hydrogen peroxide (H2O2). For glucose detection, the WE was further coated with five layers, namely, (1) polyphenol, (2) glucose oxidase, (3) polyurethane, (4) catalase, and (5) dexamethasone-releasing poly(vinyl alcohol)/poly(lactic-co-glycolic acid) composite. The amperometric response of the glucose sensor was noted in vitro and in vivo.
  
  
  RESULTS
  Scanning electron microscopy revealed that electrochemical rebuilding of the WE produced a nanoporous morphology that resulted in a 20-fold enhancement in H2O2 sensitivity, while retaining >98% selectivity. This afforded a 4-5-fold increase in overall glucose response of the glucose sensor when compared with a control sensor with no surface rebuilding and fittable only within an 18 G needle. The sensor was able to reproducibly track in vivo glycemic events, despite the large background currents typically encountered during animal testing.
  
  
  CONCLUSIONS
  Enhanced sensor performance in terms of sensitivity and large signal-to-noise ratio has been attained via electrochemical rebuilding of the WE. This approach also bypasses the need for conventional and nanostructured mediators currently employed to enhance sensor performance.
authors.affiliation: Biorasis Inc. Technology Incubation Program, University of Connecticut, Storrs, CT 06269, USA.
authors.forename: Santhisagar
authors.initials: S
authors.lastname: Vaddiraju
authors.forename: Allen
authors.initials: A
authors.lastname: Legassey
authors.forename: Liangliang
authors.initials: L
authors.lastname: Qiang
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Diane J
authors.initials: DJ
authors.lastname: Burgess
authors.forename: Fotios
authors.initials: F
authors.lastname: Papadimitrakopoulos
mesh_terms: D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation* / Q000379:methods; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis / Q000737:chemistry; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods; D004567:Electrodes, Implanted; D004595:Electroplating / Q000379:methods*; D006046:Gold / Q000737:chemistry; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry; D009339:Needles; D010984:Platinum / Q000737:chemistry; D019919:Prosthesis Implantation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties
chemical_list: D001786:Blood Glucose; D020099:Coated Materials, Biocompatible; D010984:Platinum; D006046:Gold