title: Contact activation of blood coagulation on a defined kaolin/collagen surface in a microfluidic assay.
abstract: Generation of active Factor XII (FXIIa) triggers blood clotting on artificial surfaces and may also enhance intravascular thrombosis. We developed a patterned kaolin (0 to 0.3 pg/μm(2))/type 1 collagen fibril surface for controlled microfluidic clotting assays. Perfusion of whole blood (treated only with a low level of 4 μg/mL of the XIIa inhibitor, corn trypsin inhibitor) drove platelet deposition followed by fibrin formation. At venous wall shear rate (100 s(-1)), kaolin accelerated onset of fibrin formation by ~100 sec when compared to collagen alone (250 sec vs. 350 sec), with little effect on platelet deposition. Even with kaolin present, arterial wall shear rate (1000 s(-1)) delayed and suppressed fibrin formation compared to venous wall shear rate. A comparison of surfaces for extrinsic activation (tissue factor TF/collagen) versus contact activation (kaolin/collagen) that each generated equal platelet deposition at 100 s(-1) revealed: (1) TF surfaces promoted much faster fibrin onset (at 100 sec) and more endpoint fibrin at 600 sec at either 100 s(-1) or 1000 s(-1), and (2) kaolin and TF surfaces had a similar sensitivity for reduced fibrin deposition at 1000 s(-1) (compared to fibrin formed at 100 s(-1)) despite differing coagulation triggers. Anti-platelet drugs inhibiting P2Y1, P2Y12, cyclooxygenase-1 or activating IP-receptor or guanylate cyclase reduced platelet and fibrin deposition on kaolin/collagen. Since FXIIa or FXIa inhibition may offer safe antithrombotic therapy, especially for biomaterial thrombosis, these defined collagen/kaolin surfaces may prove useful in drug screening tests or in clinical diagnostic assays of blood under flow conditions.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Shu
authors.initials: S
authors.lastname: Zhu
authors.affiliation: Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: sld@seas.upenn.edu.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation; D001777:Blood Coagulation / Q000187:drug effects* / Q000276:immunology*; D001780:Blood Coagulation Tests / Q000295:instrumentation* / Q000379:methods; D002478:Cells, Cultured; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis / Q000494:pharmacology; D003094:Collagen / Q000737:chemistry / Q000494:pharmacology*; D004867:Equipment Design; D004868:Equipment Failure; D005434:Flow Cytometry / Q000295:instrumentation*; D006801:Humans; D007616:Kaolin / Q000737:chemistry / Q000494:pharmacology*; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D054802:Molecular Imprinting / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties
chemical_list: D020099:Coated Materials, Biocompatible; D007616:Kaolin; D003094:Collagen
keywords: Contact pathway; Kaolin; Microfluidics