title: Microfluidic assay of platelet deposition on collagen by perfusion of whole blood from healthy individuals taking aspirin.
abstract: BACKGROUND
  Microfluidic devices can create hemodynamic conditions for platelet assays. We validated an 8-channel device in a study of interdonor response to acetylsalicylic acid (ASA, aspirin) with whole blood from 28 healthy individuals.
  
  
  METHODS
  Platelet deposition was assessed before treatment or 24 h after ingestion of 325 mg ASA. Whole blood (plus 100 μmol/L H-d-Phe-Pro-Arg-chloromethylketone to inhibit thrombin) was further treated ex vivo with ASA (0-500 μmol/L) and perfused over fibrillar collagen for 300 s at a venous wall shear rate (200 s(-1)).
  
  
  RESULTS
  Ex vivo ASA addition to blood drawn before aspirin ingestion caused a reduction in platelet deposition [half-maximal inhibitory concentration (IC50) approximately 10-20 μmol/L], especially between 150 and 300 s of perfusion, when secondary aggregation mediated by thromboxane was expected. Twenty-seven of 28 individuals displayed smaller deposits (45% mean reduction; range 10%-90%; P < 0.001) from blood obtained 24 h after ASA ingestion (no ASA added ex vivo). In replicate tests, an R value to score secondary aggregation [deposition rate from 150 to 300 s normalized by rate from 60 to 150 s] showed R < 1 in only 2 of 28 individuals without ASA ingestion, with R > 1 in only 3 of 28 individuals after 500 μmol/L ASA addition ex vivo. At 24 h after ASA ingestion, 21 of 28 individuals displayed poor secondary aggregation (R < 1) without ex vivo ASA addition, whereas the 7 individuals with residual secondary aggregation (R > 1) displayed insensitivity to ex vivo ASA addition. Platelet deposition was not correlated with platelet count. Ex vivo ASA addition caused similar inhibition at venous and arterial wall shear rates.
  
  
  CONCLUSIONS
  Microfluidic devices quantified platelet deposition after ingestion or ex vivo addition of aspirin.
authors.affiliation: Institute for Medicine and Engineering, Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
authors.forename: Ruizhi
authors.initials: R
authors.lastname: Li
authors.forename: Susanne
authors.initials: S
authors.lastname: Fries
authors.forename: Xuanwen
authors.initials: X
authors.lastname: Li
authors.forename: Tilo
authors.initials: T
authors.lastname: Grosser
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D001241:Aspirin / Q000494:pharmacology* / Q000627:therapeutic use; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D003094:Collagen; D051545:Cyclooxygenase 1 / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes; D006801:Humans; D008297:Male; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D008875:Middle Aged; D010973:Platelet Adhesiveness / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D010979:Platelet Function Tests; D012016:Reference Values; D012039:Regional Blood Flow; D015398:Signal Transduction; D013314:Stress, Mechanical; D013928:Thromboxane A2 / Q000378:metabolism; D055815:Young Adult
chemical_list: D005456:Fluorescent Dyes; D010975:Platelet Aggregation Inhibitors; D013928:Thromboxane A2; D003094:Collagen; D051545:Cyclooxygenase 1; D001241:Aspirin