title: Fiber-coupled fluorescence affinity sensor for 3-day in vivo glucose sensing.
abstract: BACKGROUND
  To evaluate the feasibility of an implantable fiber-coupled fluorescence affinity sensor (FAS) for glucose monitoring in humans, we studied the acute and chronic in vivo performance in hairless rats and pigs.
  
  
  METHODS
  The implantable fiber-coupled FAS was constructed by filling a dialysis chamber made of a regenerated cellulose membrane mounted to the distal tip of an optical fiber with fluorescent chemistry based on concanavalin A. Blood sugar changes in animals were induced by injections of insulin and dextrose. Determination of interstitial glucose concentrations in skin tissue was facilitated by measuring the fluorescence response of the FAS.
  
  
  RESULTS
  The acute in vivo response of the fiber-coupled FAS exhibited good correlation coefficients (>0.77) with blood sugar changes and minimal lag times (2-10 min) after 2 hours of sensor implantation. Equilibrium of the sensor signal with interstitial fluid was required less than 60 min after implantation. For both rats and pigs, chronic response of the FAS to blood sugar modulations measured during the third day of implantation successfully demonstrated proof-of-concept for short-term glucose monitoring. A slight decrease in sensitivity after 3 days in the small animal model was assumed to be caused by excessive mechanical forces on the implanted device because of high animal motility.
  
  
  CONCLUSIONS
  Overall, the chronic in vivo performance of the FAS in two different animal models over 3 days was clinically acceptable and comparable to other continuous glucose monitoring platforms. The major benefit of the FAS is the absence of "autodestructive" side products and any device-related warm-up time after sensor reconnection.
authors.affiliation: BioTex, Inc., Houston, Texas 77054, USA. ralph@biotexmedical.com
authors.forename: Ralph
authors.initials: R
authors.lastname: Ballerstadt
authors.forename: Colton
authors.initials: C
authors.lastname: Evans
authors.forename: Ashok
authors.initials: A
authors.lastname: Gowda
authors.forename: Roger
authors.initials: R
authors.lastname: McNichols