Dynamic in vitro hemocompatibility of oligoproline self-assembled monolayer surfaces

The blood compatibility of self-assembled monolayers (SAMs) of oligoproline, a nonionic antifouling peptide, was investigated using the cone-and-plate assay imitating arterial blood flow conditions. End-capped oligoprolines composed of 6 and 9 proline residues (Pro6 and Pro9) and a Cys residue were synthesized for preparing SAMs (Pro-SAMs) on Au-sputtered glass. The surface of Pro-SAMs indicated hydrophilic property with a smooth topology. The adsorption of blood components and the adhesion of blood cells, including leukocytes and platelets, were strongly suppressed on Pro-SAMs. Moreover, Pro9-SAM did not trigger the activation of platelets (i.e., the conformational change of GPIIb/IIIa and P-selectin (CD62P) expression on platelets and the formation of aggregates). Our results demonstrate that Pro9-SAM completely inhibited acute thrombogenic responses and the activation of platelets under dynamic conditions.

Biomimetic microcavity interfaces for a label-free capture of pathogens in the fluid bloodstream by vortical crossflow filtration

Bacterial sepsis is a lethal disease triggered by microbial pathogens. The blood pathogen load is a major contributor to both disease severity and mortality in patients with sepsis blood. Therefore, it is crucial to reduce the load of pathogens, in particular the drug-resistant pathogens. In this work, inspired by the crossflow filtration mechanism in suspension-feeding fish, we developed a biomimetic microcavity interface to mimic a porous gill-raker surface as a blood-cleansing dialyzer for sepsis therapy, which can rapidly, safely and efficiently clear bacteria from the fluidic blood. The microcavity interface consists of microcavity arrays, the innerface of which contains nanowire forests. By precisely controlling the pore size of the microcavity and directing the axial travel of the fluid, the bacteria can be isolated from the whole blood without disturbing any blood components or blocking the blood cell transportation. In addition, the three-dimensional nanowire forests assist in the formation of vortices with reduced blood flow velocity and increased resistance to bacterial deposition in situ. Functional modification is not required to recognize the bacteria specifically in our designed dialyzer. Moreover, the microcavity interface clears over 95% bacteria from a fluid blood sample without inducing protein adsorption or complement and platelet activation when contacting the fluid blood. The study supports this biomimetic microcavity interface to be a promising extracorporeal blood-cleansing device in clinical settings.

Polyrotaxane-based biointerfaces with dynamic biomaterial functions

The molecular mobility of cyclic molecules (e.g.α-cyclodextrins) threaded along a linear polymer chain (e.g. poly(ethylene glycol)) in polyrotaxanes is a unique feature for biomaterials with dynamic functionality. Surfaces with molecular mobility can be obtained by introducing polyrotaxanes. The molecular mobility of polyrotaxane-based surfaces can be modulated by changing the number of threaded cyclic molecules and modifying their functional groups. Biological ligands modified with α-cyclodextrins exhibit increased multivalent interactions with their receptors due to the molecular mobility of the latter. Furthermore, polyrotaxane-based surfaces not only improve the initial response of cells via multivalent interactions, but also affect cytoskeleton formation and the inherent quality of cells, including differentiation. Such polyrotaxane surfaces can emerge as new biointerfaces that can adapt to the dynamic biological nature.

Surface bound VEGF mimicking peptide maintains endothelial cell proliferation in the absence of soluble VEGF in vitro

Continuous glucose monitoring is an efficient method for the management of diabetes and in limiting the complications induced by large fluctuations in glucose levels. For this, intravascular systems may assist in producing more reliable and accurate devices. However, neovascularization is a key factor to be addressed in improving their biocompatibility. In this scope, the perennial modification of the surface of an implant with the proangiogenic Vascular Endothelial Growth Factor mimic peptide (SVVYGLR peptide sequence) holds great promise. Herein, we report on the preparation of gold substrates presenting the covalently grafted SVVYGLR peptide sequence and their effect on HUVEC behavior. Effective coupling was demonstrated using XPS and PM-IRRAS. The produced surfaces were shown to be beneficial for HUVEC adhesion. Importantly, surface bound SVVYGLR is able to maintain HUVEC proliferation even in the absence of soluble VEGF. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1425-1436, 2016.

Mobility of the Arg-Gly-Asp ligand on the outermost surface of biomaterials suppresses integrin-mediated mechanotransduction and subsequent cell functions

Mechanotransduction in the regulation of cellular responses has been previously studied using elastic hydrogels. Because cells interact only with the surface of biomaterials, we are focusing on the molecular mobility at the outermost surface of biomaterials. In this study, surfaces with the mobile Arg-Gly-Asp-Ser (RGDS) peptide have been constructed. Cell culture substrates were coated with ABA-type block copolymers composed of poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) segments (A) and a polyrotaxane (PRX) unit with RGDS bound to α-cyclodextrin (B). Adhesion, morphological changes and actin filament formation of human umbilical vein endothelial cells were reduced on the surfaces containing mobile PRX-RGDS in comparison to the immobile RGDS surfaces constructed from random copolymers with RGDS side groups (Prop-andom-RGDS). In the neurite outgrowth assay using rat adrenal pheochromocytoma cells (PC12), only ∼20% of adherent PC12 cells had neurites on PRX-RGDS surfaces, but more than 50% did on the Random-RGDS surface. The beating colony of dimethyl-sulfoxide-treated mouse embryonic carcinoma cells (P19CL6) were found 10 and 14 days after induction on PRX-RGDS and Random-RGDS surfaces, respectively. After 22 days, the beating colony disappeared on PRX-RGDS surfaces, but many colonies remained on Random-RGDS surfaces. These data suggest that the molecular mobility of the cell-binding ligand on the outermost surface of materials effectively suppresses the actin filament formation and differentiation of these functional cell lines, and may be used as a culture substrate for immature stem cells or progenitor cells.

Ligand capture and activation of human platelets at monolayer modified gold surfaces

The effect of RGD peptides, alkane and PEG in self assembled mixed monolayers on gold on platelet adhesion and activation is explored.

Fabrication of nonbiofouling metal stent and in vitro studies on its hemocompatibility

In recent years, there has been increasing interest for the surface modification of biomaterials in order to improve their surface properties. The bare metal stents surface based on 3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate polymers has shown an excellent antifouling and blood compatibility by using surface-initiated atom transfer radical polymerization. Surface structure, morphology, wettability, and element content were characterized by scanning electronic microscope, static water contact angles measurement, X-ray photoelectron spectroscopy measurement, respectively. The results showed zwitterionic brushes were successfully fabricated on bare metal stents. The blood compatibility of bare metal stents before and after modification was evaluated by platelet adhesion tests, hemolysis assay, morphological changes of red blood cells, coagulation time tests, plasma recalcification time assay, complement activation, and platelet activation at molecular level. Moreover, the cytotoxicity was also to be characterized. All assays showed after the modification with zwitterionic brush the metal stents displayed a property of excellent blood compatibility and low cytotoxicity.