Surface modification of a titanium alloy with a phospholipid polymer prepared by a plasma-induced grafting technique to improve surface thromboresistance

Abstract

To improve the thromboresistance of a titanium alloy (TiAl 6 V 4 ) surface which is currently utilized in several ventricular assist devices (VADs), a plasma-induced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out and poly(MPC) (PMPC) chains were covalently attached onto a TiAl 6 V 4 surface by a plasma induced technique. Cleaned TiAl 6 V 4 surfaces were pretreated with H 2 O-vapor-plasma and silanated with 3-methacryloylpropyltrimethoxysilane (MPS). Next, a plasma-induced graft polymerization with MPC was performed after the surfaces were pretreated with Ar plasma. Surface compositions were verified by X-ray photoelectron spectroscopy (XPS). In vitro blood biocompatibility was evaluated by contacting the modified surfaces with ovine blood under continuous mixing. Bulk phase platelet activation was quantified by flow cytometric analysis, and surfaces were observed with scanning electron microscopy after blood contact. XPS data demonstrated successful modification of the TiAl 6 V 4 surfaces with PMPC as evidenced by increased N and P on modified surfaces. Platelet deposition was markedly reduced on the PMPC grafted surfaces and platelet activation in blood that contacted the PMPC-grafted samples was significantly reduced relative to the unmodified TiAl 6 V 4 and polystyrene control surfaces. Durability studies under continuously mixed water suggested no change in surface modification over a one month period. This modification strategy shows promise for further investigation as a means to reduce the thromboembolic risk associated with the metallic blood-contacting surfaces of VADs and other cardiovascular devices under development.

Standardized methods to quantify thrombogenicity of blood‐contacting materials via thromboelastography

“…Other techniques involve measuring the effect of biomaterials on platelet cell activation, leukocyte activation, or quantifying the number of adhered platelets [through scanning electron microscopy and lactate dehydrogenase (LDH) assays] either in vitro or in vivo. [9][10][11][12] However, each of the above assays quantifies only one component of the entire cascade or either the Intrinsic or Extrinsic pathway. Due to the redundant nature of the coagulation process, either pathway can lead to clot formation and further there are redundancies within each pathway; therefore, it is possible to have a significant number of false positives and false negatives using these assays.…”

Simple surface modification of a titanium alloy with silanated zwitterionic phosphorylcholine or sulfobetaine modifiers to reduce thrombogenicity

“…Along these lines, we have recently demonstrated that a PC group-bearing polymer could be covalently bound to a titanium alloy (TiAl 6 V 4 ) surface by a condensation reaction or with plasma initiated graft polymerization after the TiAl 6 V 4 surface was treated with a functional silane coupling agent [20, 21]. However, the required pre-modification steps for these reactions may have resulted in diminished control of the uniformity and coverage of the PC groups on the modified surface.…”

The effect of different component ratios in block polymers and processing conditions on electrodeposition efficiency onto titanium

“…According to the binding energy, P 2p originating from PO 4 3− and N 1s peaks at about 402.5 eV originating from N + (CH 3 ) 3 appeared only in PMbA-Tis. This indicated that PMbAs were immobilized on Ti by electrodeposition.…”

“…It does not suffer from decomposition due to oxidation in the human body, which means that MPC is a more suitable material to modify surfaces of medical devices embedded long-term in the human body [2,3]. Moreover, approaches to immobilize polymers on metals utilizing the bonding SH, SS , or SiO group were examined [4]. MPC polymers immobilized on titanium reduce albumin adsorption [5] and platelet adhesion [6].…”