Evaluation of Phospholipidic Surface Coatings ex-vivo

Abstract

To evaluate the thromboresistant properties of phospholipidic surface coatings mimicking the lipid surface of blood cells, we studied four different types of phospholipids bound onto PVC tubings in comparison to uncoated as well as heparin bonded controls. The samples analyzed included diacetylenic phospholipid coated as a monomeric treatment (A), diacetylenic phospholipid polymerised prior to being coated (B), and two types of polymeric phospholipids made using methacrylate containing monomers (C and D). A bovine (bodyweight 67 ± 3 kg) left heart bypass model (pump flow 3.2 ±0.1 l/min) was selected and the surfaces were exposed to the blood stream up to 360 min without systemic heparinization. Thereafter another set of samples was exposed to stagnant blood over 20 min. Besides hemodynamic, hematologic and biochemical analyses, the macroscopic appearance of 119 blood exposed surface samples was graded semiquantitatively on a scale of 0 to 10: no macroscopic deposits = grade 0, 1 spot (1 mm diameter) = grade 1, 2 spots = grade 2, 5 or more spots = grade 5, up to 10% of the surface covered with clots = grade 6, 100% covered = grade 10 (p<0.05=∗): mean grade of deposits was 0.0 ± 0.0 for segments perfused and 0.0 ± 0.0 for segments exposed to stagnant blood with surfaces exposing to the blood either heparin, phopholipid A, or phospholipid B (NS). Phospholipids C and D were graded 0.0 ± 0.0 if perfused and 0.7 ± 1.2 if exposed to stagnant blood. Uncoated PVC control tubings however were graded 0.2 ± 0.8 for segments perfused and 2.7 ± 3.0 for segments exposed to stagnat blood (p<0.05 in comparison to all surfaces coated with phospholipids or heparin if perfused and if exposed to stagnant blood). Hence phospholipidic surface coatings expose significant antithrombotic properties which out perform todays standard for tubings in clinical perfusion (uncoated PVC).

Novel Biomimetic Surfactant: Synthesis and Micellar Characteristics

“…On the basis of this “bioinspired” approach, the phospholipid‐analogous vinyl polymer containing 2‐(methacryloyloxy)ethyl 2‐aminoethyl hydrogen phosphate and a very useful vinyl monomer, 2‐(methacryloyloxy)ethyl phosphorylcholine (MPC), was successfully synthesized 26,27. Since then a vast amount of work has extended the use of MPC, all of which has shown it to suppress protein adsorption,28,29 platelet adhesion,30 thrombus formation,31 and cell adhesion 32. Currently, solutions, hydrogels,33 and nanoparticles34 composed of PC‐polymers are being evaluated as delivery vehicles in cosmetics35,36 and pharmaceutical formulations 37…”

Do We Need Heparin Coating for Extracorporeal Membrane Oxygenation? New Concepts and Controversial Positions About Coating Surfaces of Extracorporeal Circuits

“…The aim is to directly reduce the protein and cell adhesion on the surface to minimize the possible adverse effects on blood biochemistry. PPC, by mimicking the membranes of endothelial cells, has a thromboresistance that has been already established .…”

“…The evidence suggests that PPC may allow a safe reduction of systemic heparinization and there are no cases of heparin‐specific complications using this coating; many studies have demonstrated that PPC can reduce blood loss and thromboembolic complications compared with uncoated circuits . Ranucci et al , in a retrospective study, evaluated PPC circuit versus heparin‐coated circuit and observed that PPC had better preservation of platelet count and lower postoperative bleeding than heparin coating.…”

Surface modification of polymeric biomaterials: Utilization of cyclodextrins for blood compatibility improvement

“…The coated surface properties are hypothesized to be mainly influenced by the underlying material surfaces 18. In addition to those modifications based on MPC copolymer, some different phospholipids have been bound onto PVC tubing19 to achieve improved blood compatibility. Researchers also applied albumin and heparin multilayer at the surface of medical device to improve the blood compatibility 20.…”