Surface modification of biomaterials: a quest for blood compatibility.

UCL Centre for Nanotechnology & Regenerative Medicine, University College London, Pond Street, London NW3 2QG, UK.
International Journal of Biomaterials 01/2012; 2012:707863. DOI: 10.1155/2012/707863
Source: PubMed

ABSTRACT Cardiovascular implants must resist thrombosis and intimal hyperplasia to maintain patency. These implants when in contact with blood face a challenge to oppose the natural coagulation process that becomes activated. Surface protein adsorption and their relevant 3D confirmation greatly determine the degree of blood compatibility. A great deal of research efforts are attributed towards realising such a surface, which comprise of a range of methods on surface modification. Surface modification methods can be broadly categorized as physicochemical modifications and biological modifications. These modifications aim to modulate platelet responses directly through modulation of thrombogenic proteins or by inducing antithrombogenic biomolecules that can be biofunctionalised onto surfaces or through inducing an active endothelium. Nanotechnology is recognising a great role in such surface modification of cardiovascular implants through biofunctionalisation of polymers and peptides in nanocomposites and through nanofabrication of polymers which will pave the way for finding a closer blood match through haemostasis when developing cardiovascular implants with a greater degree of patency.

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    ABSTRACT: The hypothesis was that anti-fouling diamond-like carbon polydimethylsiloxane hybrid (DLC-PDMS-h) surface impairs early and late cellular adhesion and matrix-cell interactions. The effect of hybrid surface on cellular adhesion and cytoskeletal organization, important for osteogenesis of human mesenchymal stromal cells (hMSC), where therefore compared with plain DLC and titanium (Ti). hMSCs were induced to osteogenesis and followed over time using scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR), and hydroxyapatite (HA) staining. SEM at 7.5 hours showed that initial adherence and spreading of hMSC was poor on DLC-PDMS-h. At 5 days some hMSC were undergoing condensation and apoptotic fragmentation, whereas cells on DLC and Ti grew well. DAPI-actin-vinculin triple staining disclosed dwarfed cells with poorly organized actin cytoskeleton-focal complex/adhesion-growth substrate attachments on hybrid coating, whereas spread cells, organized microfilament bundles, and focal adhesions were seen on DLC and in particular on Ti. Accordingly, at day one ToF-SIMS mass peaks showed poor protein adhesion to DLC-PDMS-h compared with DLC and Ti. COL1A1, ALP, OP mRNA levels at days 0, 7, 14, 21, and/or 28 and lack of HA deposition at day 28 demonstrated delayed or failed osteogenesis on DLC-PDMS-h. Anti-fouling DLC-PDMS-h is a poor cell adhesion substrate during the early protein adsorption-dependent phase and extracellular matrix-dependent late phase. Accordingly, some hMSCs underwent anoikis-type apoptosis and failed to complete osteogenesis, due to few focal adhesions and poor cell-to-ECM contacts. DLC-PDMS-h seems to be a suitable coating for non-integrating implants/devices designed for temporary use. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2014.
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    12/2013; 7(2).
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    ABSTRACT: The usefulness of nanoscale topography in improving vascular response in vitro was previously established in our study on hydrothermally modified titanium surfaces. To propose this strategy of surface modification for clinical translation onto metallic stents, it is imperative that the surface be also hemocompatible - an essential attribute for any blood contacting device. The present in vitro study focuses on a detailed hemocompatibility evaluation of titania nanostructures created through an alkaline hydrothermal route on metallic Ti stent prototypes. Direct interactions of TiO2 nanocues of varied morphologies with whole blood were studied under static conditions as well as using an in vitro circulation model mimicking arterial flow, with respect to polished Ti control. Nanomodified stent surfaces upon contact with human blood showed negligible hemolysis under constant shear and static conditions. Coagulation profile testing indicated that surface roughness of nanomodified stents induced no alterations in the normal clotting times, with insignificant thrombus formation and minimal inflammatory reaction. Endothelialized nanomodified Ti surfaces were found to inhibit both activation as well as aggregation of platelets compared to the control surface, with the endothelium formed on the nanosurfaces having an increased expression of anti-thrombogenic genes. Such a nanotextured Ti surface which is anti-thrombogenic and promotes endothelialization would be a cost-effective option to drug eluting stents or polymer coated stents for overcoming in-stent restenosis.
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