title: A factor VIII-derived peptide enables von Willebrand factor (VWF)-binding of artificial platelet nanoconstructs without interfering with VWF-adhesion of natural platelets.
abstract: There is substantial clinical interest in synthetic platelet analogs for potential application in transfusion medicine. To this end, our research is focused on self-assembled peptide-lipid nanoconstructs that can undergo injury site-selective adhesion and subsequently promote site-directed active platelet aggregation, thus mimicking platelet's primary hemostatic actions. For injury site-selective adhesion, we have utilized a coagulation factor FVIII-derived VWF-binding peptide (VBP). FVIII binds to VWF's D'-D3 domain while natural platelet GPIbα binds to VWF's A1 domain. Therefore, we hypothesized that the VBP-decorated nanoconstructs will adhere to VWF without mutual competition with natural platelets. We further hypothesized that the adherent VBP-decorated constructs can enhance platelet aggregation when co-decorated with a fibrinogen-mimetic peptide (FMP). To test these hypotheses, we used glycocalicin to selectively block VWF's A1 domain and, using fluorescence microscopy, studied the binding of fluorescently labeled VBP-decorated nanoconstructs versus platelets to ristocetin-treated VWF. Subsequently, we co-decorated the nanoconstructs with VBP and FMP and incubated them with human platelets to study construct-mediated enhancement of platelet aggregation. Decoration with VBP resulted in substantial construct adhesion to ristocetin-treated VWF even if the A1-domain was blocked by glycocalicin. In comparison, such A1-blocking resulted in significant reduction of platelet adhesion. Without A1-blocking, the VBP-decorated constructs and natural platelets could adhere to VWF concomitantly. Furthermore, the constructs co-decorated with VBP and FMP enhanced active platelet aggregation. The results indicate significant promise in utilizing the FVIII-derived VBP in developing synthetic platelet analogs that do not interfere with VWF-binding of natural platelets but allow site-directed enhancement of platelet aggregation when combined with FMP.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA. axs262@case.edu.
authors.forename: Hassan
authors.initials: H
authors.lastname: Haji-Valizadeh
authors.forename: Christa L
authors.initials: CL
authors.lastname: Modery-Pawlowski
authors.forename: Anirban
authors.initials: A
authors.lastname: Sen Gupta
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D005169:Factor VIII / Q000737:chemistry*; D006801:Humans; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008856:Microscopy, Fluorescence; D049329:Nanostructures / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D010973:Platelet Adhesiveness; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012310:Ristocetin / Q000737:chemistry; D014841:von Willebrand Factor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008081:Liposomes; D010455:Peptides; D019038:Platelet Glycoprotein GPIb-IX Complex; C094990:adhesion receptor; D014841:von Willebrand Factor; D012310:Ristocetin; D005169:Factor VIII