title: Development of a Microsphere-Based System to Facilitate Real-Time Insulin Monitoring.
abstract: The speed of insulin absorption after subcutaneous delivery is highly variable. Incorrect assumptions about insulin pharmacokinetics compromise effective glycemic regulation. Our ultimate goal is to develop a system to monitor insulin levels in vivo continuously, allowing pharmacokinetic parameters to be calculated in real time. We hypothesize that a bead-based detection system can be run on a flow-through microfluidic platform to measure insulin in subcutaneous fluid sampled via microdialysis. As a first step in development, we focused on microsphere-based measurement of insulin.
  
  
  
  Polystyrene microspheres coated with an anti-insulin monoclonal antibody were exposed to insulin-containing solutions, and after addition of a fluorescently labeled anti-insulin monoclonal antibody with a distinct epitope, bead-associated fluorescence was detected by fluorescence microscopy in 96-well plates or in a flow-through, microfluidic platform.
  
  
  
  The bead detection system in plates had a linear range in buffer for regular human insulin (RHI), insulin lispro, and insulin aspart of 15-1115 µIU/ml, 14-976 µIU/ml, and 25-836 µIU/ml, respectively. Measurement on plasma samples demonstrated proportionality between basal and peak insulin levels similar to the laboratory reference method. Preliminary results in a polydimethylsiloxane-based, flow-through, microfluidic platform showed a strong signal at peak insulin levels.
  
  
  
  We have developed a microsphere-based system to rapidly measure levels of insulin and insulin analogs. We have further demonstrated proof of concept that this bead detection system can be implemented in a lab-on-a-chip format, which will be further developed and combined with microdialysis for real-time monitoring of insulin in vivo.
authors.affiliation: Department of Biotechnology Engineering, Ben Gurion University of the Negev, Beer Sheva, Israel Diabetes Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Lindy
authors.initials: L
authors.lastname: Kahanovitz
authors.affiliation: Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, Shriners Burns Institute, Boston, MA, USA Department of Electrical and Computer Engineering, University of California, Davis, Davis, CA, USA.
authors.forename: Erkin
authors.initials: E
authors.lastname: Seker
authors.affiliation: Department of Biotechnology Engineering, Ben Gurion University of the Negev, Beer Sheva, Israel.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Marks
authors.affiliation: Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, Shriners Burns Institute, Boston, MA, USA.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Yarmush
authors.affiliation: Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, Shriners Burns Institute, Boston, MA, USA Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA.
authors.forename: Tania
authors.initials: T
authors.lastname: Konry
authors.affiliation: Diabetes Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA sjrussell@mgh.harvard.edu.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Russell
mesh_terms: D006801:Humans; D007004:Hypoglycemic Agents / Q000097:blood*; D007328:Insulin / Q000097:blood*; D056656:Lab-On-A-Chip Devices; D046210:Microfluidic Analytical Techniques; D008863:Microspheres
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin
keywords: insulin; insulin analogs; microfluidic; microsphere; pharmacokinetics