title: Blood-induced interference of glucose sensor function in vitro: implications for in vivo sensor function.
abstract: BACKGROUND
  Although tissue hemorrhages, with resulting blood clots, are associated with glucose sensor implantation, virtually nothing known is about the impact of red blood cells and red blood cell clots on sensor function in vitro or in vivo. In these studies, we tested the hypothesis that blood can directly interfere with glucose sensor function in vitro.
  
  
  METHODS
  To test this hypothesis, heparinized human whole blood (HWB) and nonheparinized human whole blood (WB) were obtained from normal individuals. Aliquots of HWB and WB samples were also fractionated into plasma, serum, and total leukocyte (TL) components. Resulting HWB, WB, and WB components were incubated in vitro with an amperometric glucose sensor for 24 hours at 37 degrees C. During incubation, blood glucose levels were determined periodically using a glucose monitor, and glucose sensor function (GSF) was monitored continuously as nanoampere output.
  
  
  RESULTS
  Heparinized human whole blood had no significant effect on GSF in vitro, nor did TL, serum, or plasmaderived clots from WB. Sensors incubated with WB displayed a rapid signal loss associated with clot formation at 37 degrees C. The half-life was 0.8 +/- 0.2 hours (n = 16) for sensors incubated with WB compared to 3.2 +/- 0.5 (n = 12) for sensors incubated with HWB with a blood glucose level of approximately 100 mg/dl.
  
  
  CONCLUSIONS
  These studies demonstrated that human whole blood interfered with GSF in vitro. These studies further demonstrated that this interference was related to blood clot formation, as HWB, serum, plasma-derived clots, or TL did not interfere with GSF in vitro in the same way that WB did. These in vitro studies supported the concept that the formation of blood clots at sites of glucose sensor implantation could have a negative impact on GSF in vivo.
authors.affiliation: Center for Molecular Tissue Engineering, University of Connecticut, Farmington, Connecticut 06030, USA. klueh@nso.uchc.edu
authors.forename: Ulrike
authors.initials: U
authors.lastname: Klueh
authors.forename: Zenghe
authors.initials: Z
authors.lastname: Liu
authors.forename: Tianmei
authors.initials: T
authors.lastname: Ouyang
authors.forename: Brian
authors.initials: B
authors.lastname: Cho
authors.forename: Ben
authors.initials: B
authors.lastname: Feldman
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Henning
authors.forename: Don
authors.initials: D
authors.lastname: Kreutzer