title: Monitoring of heparin and its low-molecular-weight analogs by silicon field effect.
abstract: Heparin is a highly sulfated glycosaminoglycan that is used as an important clinical anticoagulant. Monitoring and control of the heparin level in a patient's blood during and after surgery is essential, but current clinical methods are limited to indirect and off-line assays. We have developed a silicon field-effect sensor for direct detection of heparin by its intrinsic negative charge. The sensor consists of a simple microfabricated electrolyte-insulator-silicon structure encapsulated within microfluidic channels. As heparin-specific surface probes the clinical heparin antagonist protamine or the physiological partner antithrombin III were used. The dose-response curves in 10% PBS revealed a detection limit of 0.001 units/ml, which is orders of magnitude lower than clinically relevant concentrations. We also detected heparin-based drugs such as the low-molecular-weight heparin enoxaparin (Lovenox) and the synthetic pentasaccharide heparin analog fondaparinux (Arixtra), which cannot be monitored by the existing near-patient clinical methods. We demonstrated the specificity of the antithrombin III functionalized sensor for the physiologically active pentasaccharide sequence. As a validation, we showed correlation of our measurements to those from a colorimetric assay for heparin-mediated anti-Xa activity. These results demonstrate that silicon field-effect sensors could be used in the clinic for routine monitoring and maintenance of therapeutic levels of heparin and heparin-based drugs and in the laboratory for quantitation of total amount and specific epitopes of heparin and other glycosaminoglycans.
authors.affiliation: Biological Engineering Division, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Nebojsa M
authors.initials: NM
authors.lastname: Milovic
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Behr
authors.forename: Michel
authors.initials: M
authors.lastname: Godin
authors.forename: Chih-Sheng Johnson
authors.initials: CS
authors.lastname: Hou
authors.forename: Kristofor R
authors.initials: KR
authors.lastname: Payer
authors.forename: Aarthi
authors.initials: A
authors.lastname: Chandrasekaran
authors.forename: Peter R
authors.initials: PR
authors.lastname: Russo
authors.forename: Ram
authors.initials: R
authors.lastname: Sasisekharan
authors.forename: Scott R
authors.initials: SR
authors.lastname: Manalis
mesh_terms: D000327:Adsorption; D000925:Anticoagulants / Q000737:chemistry* / Q000494:pharmacology / Q000627:therapeutic use; D000990:Antithrombin III / Q000737:chemistry / Q000502:physiology; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D002240:Carbohydrate Sequence; D003124:Colorimetry; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring / Q000379:methods; D017984:Enoxaparin / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D015951:Factor Xa / Q000032:analysis; D000077425:Fondaparinux; D005544:Forecasting; D006493:Heparin / Q000737:chemistry* / Q000494:pharmacology / Q000627:therapeutic use; D006495:Heparin, Low-Molecular-Weight / Q000737:chemistry* / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D007700:Kinetics; D044085:Microfluidics; D011134:Polysaccharides / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D011479:Protamines / Q000037:antagonists & inhibitors / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012825:Silicon / Q000737:chemistry*
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D006495:Heparin, Low-Molecular-Weight; D011134:Polysaccharides; D011479:Protamines; D000990:Antithrombin III; D006493:Heparin; D015951:Factor Xa; D000077425:Fondaparinux; D012825:Silicon