Adsorption of Fibrinogen and Lysozyme on Silicon Grafted with Poly(2-methacryloyloxyethyl Phosphorylcholine) via Surface-Initiated Atom Transfer Radical Polymerization

Abstract

Surfaces based on grafted poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) "brushes" with a constant graft density of 0.39 chain/nm2 and chain length from 5 to 200 monomer units were prepared by surface-initiated atom transfer radical polymerization (ATRP) on silicon wafers. The chain length and layer thickness of the poly(MPC) grafts were varied via the ratio of MPC to sacrificial initiator. The surfaces were characterized by water contact angle, XPS, and AFM. The effect of poly(MPC) chain length on fibrinogen and lysozyme adsorption was studied in TBS buffer at pH 7.4. The adsorption of both proteins on the poly(MPC)-grafted surfaces was greatly reduced compared to the unmodified silicon. Adsorption decreased with increasing chain length of the poly(MPC) grafts. Grafts of chain length 200 (MW 59 000) gave adsorption levels of 7 and 2 ng/cm2, respectively, for fibrinogen and lysozyme at 1 mg/mL protein concentration, corresponding to reductions of greater than 98% compared to the unmodified silicon. Adsorption experiments using mixtures of the two proteins showed that the suppression of protein adsorption on the poly(MPC)-grafted surfaces was not strongly dependent on protein size or charge.

Penetration and Saturation of Lysozyme in Phospholipid Bilayers

“…7 The adsorption of proteins to lipid layers is recognized as the first event following the implantation of biomaterials and has been shown to play an important role in determining subsequent events such as thrombus formation, foreign body reaction, and other undesirable responses. 8,9 The function of proteins is realized by their residues, whose capability is greatly affected by their local environment. It is of great importance to study the distribution of proteins in lipid membranes.…”

Controlled loop and graft formations of water-soluble polymers on SAMs for the design of biomaterials surfaces

“…1 Much effort has been devoted to the development of polymers to eliminate protein adsorption and the subsequent cellular responses on surfaces contacting blood or body fluid in a living body. 2,3 In particular, hydrophilic polymers such as poly(ethylene glycol) (PEG) [4][5][6][7][8] and phospholipid polymers [9][10][11][12][13] have been well developed and are some of the most promising candidates to eliminate protein adsorption. They have a suitable chain length and density, excluded volume effect, entropic repulsive force, surface wettability and hydration.…”

MPC polymer regulates fibrous tissue formation by modulating cell adhesion to the biomaterial surface

“…To the end of fabricating blood-compatible polymer surfaces, a novel coating material based on natural phospholipid cell membranes has been proposed 6) . 2-methacryloyloxyethyl phosphorylcholine (MPC), which has a phospholipid polar group that mimics a biomembrane, was synthesized as a novel coating material by Ishihara et al 7) .…”

“…However, MPC has several drawbacks, amongst which are poor mechanical properties caused by the introduction of water-soluble moieties, and in the case of coatings, weak bonding to the substrate leading to delamination 6) . To improve its mechanical properties and reduce the proneness to delamination, MPC may be copolymerized with other methacrylate monomers, such as n-butyl methacrylate (BMA), nhexyl methacrylate, and n-dodecyl methacrylate (DMA) 9) , through atom transfer radical polymerization (ATRP) or conventional free radical polymerization initiated by different methods 10) .…”

“…Huang et al used it in soft contact lenses to prevent protein adsorption 12) . The list goes on with MPC polymer being applied to myriad medical devices including biosensors 13) , drug carriers, vascular stents, and urological devices 6) . Owing to its ability to mimic the biomembrane, MPC polymer might possess the capacity to regulate unwanted fibrous tissue formation.…”