Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility.

Hemocompatible materials are needed for internal and extracorporeal biomedical applications, which should be realizable by reducing protein and thrombocyte adhesion to such materials. Polyethers have been demonstrated to be highly efficient in this respect on smooth surfaces. Here, we investigate the grafting of oligo- and polyglycerols to rough poly(ether imide) membranes as a polymer relevant to biomedical applications and show the reduction of protein and thrombocyte adhesion as well as thrombocyte activation.

Poly(ethylene glycol) grafting to poly(ether imide) membranes: influence on protein adsorption and thrombocyte adhesion.

The chain length and end groups of linear PEG grafted on smooth surfaces is known to influence protein adsorption and thrombocyte adhesion. Here, it is explored whether established structure function relationships can be transferred to application relevant, rough surfaces. Functionalization of poly(ether imide) (PEI) membranes by grafting with monoamino PEG of different chain lengths (Mn  =1 kDa or 10 kDa) and end groups (methoxy or hydroxyl) is proven by spectroscopy, changes of surface hydrophilicity, and surface shielding effects.

Dynamic in vitro hemocompatibility testing of poly(ether imide) membranes functionalized with linear, methylated oligoglycerol and oligo(ethylene glycol).

Linear, side-chain methylated oligoglycerols (OGMe) were recently reported as potential surface passivating molecules for improving the protein resistance of cardiovascular application relevant poly(ether imide) (PEI) membranes. A previously reported in vitro screening under static test conditions allowed an end-point evaluation of the adhesion and activation of adherent thrombocytes performed on the material surfaces and revealed similar levels of thrombogenicity on PEI membranes, functionalized with OGMe and oligo(ethylene glycol) (OEG) of similar molecular weight (Mn = 1,300 g·mol-1 - 1,800 g·mol-1). In the present study, we investigated the hemocompatibility of these materials in a dynamic closed loop system, in order to study time-dependent thrombocyte material interactions also of the circulating thrombocytes by mimicking in vivo relevant flow conditions in a dynamic test system with multiple material contacts.

Characterization of oligo(ethylene glycol) and oligoglycerol functionalized poly(ether imide) by angle-dependent X-ray photoelectron spectroscopy.

Purpose: Previous investigations have shown that poly(ether imide) (PEI) membranes can be functionalized with aminated macromolecules. In this study we explored whether the characterization of PEI functionalized with oligo(ethylene glycol) (OEG) or linear, side chain methylated oligoglycerols (OGMe), by angle-dependent X-ray induced photoelectron spectroscopy (XPS) can be used to prove the functionalization, give insight into the reaction mechanism and reveal the spatial distribution of the grafts.

Methods: PEI membranes were functionalized under alkaline conditions using an aqueous solution with 2 wt% of α-amino-ω-methoxy oligo(ethylene glycol) (Mn = 1,320 g·mol(-1)) or linear, side chain methylated monoamine oligoglycerols (Mn = 1,120, 1,800 or 2,270 g·mol(-1)), respectively.