Relationship between blood compatibility and water structure—Comparative study between 2-methoxyethylacrylate- and 2-methoxyethylmethacrylate-based random copolymers

Graphene-based materials: the key for the successful application of pHEMA as a blood-contacting device

Thrombosis and infection are the leading causes of blood-contacting device (BCD) failure, mainly due to the poor performance of existing biomaterials. Poly(2-hydroxyethyl methacrylate) (pHEMA) has excellent hemocompatibility but the weak mechanical properties impair its use as a bulk material for BCD. As such, pHEMA has been explored as a coating, despite the instability and difficulty of attachment to the underlying polymer compromise its success. This work describes the hydrogel composites made of pHEMA and graphene-based materials (GBM) that meet the biological and mechanical requirements for a stand-alone BCD. Five GBM differing in thickness, oxidation degree, and lateral size were incorporated in pHEMA, revealing that only oxidized-GBM can reinforce pHEMA. pHEMA/oxidized-GBM composites are cytocompatible and prevent the adhesion of endothelial cells, blood platelets, and bacteria (S. aureus), thus maintaining pHEMA's anti-adhesive properties. As a proof of concept, the thrombogenicity of the tubular prototypes of the best formulation (pHEMA/Graphene oxide (GO)) was evaluated in vivo, using a porcine arteriovenous-shunt model. pHEMA/GO conduits withstand the blood pressure and exhibit negligible adhesion of blood components, revealing better hemocompatibility than ePTFE, a commercial material for vascular access. Our findings reveal pHEMA/GO, a synthetic and off-the-shelf hydrogel, as a preeminent material for the design of blood-contacting devices that prevent thrombosis and bacterial adhesion.

Photochemically Controlled Drug Dosing from a Polymeric Scaffold

Purpose

To develop the first photoactive biomaterial coating capable of controlled drug dosing via inclusion of synthesised drug-3,5-dimethoxybenzoin (DMB) conjugates in a poly(2-methyoxyethyl acrylate) (pMEA) scaffold.

Methods

Flurbiprofen- and naproxen-DMB conjugates were prepared via esterification and characterised via NMR spectroscopy and mass spectrometry following chromatographic purification. Conjugate photolysis was investigated in acetonitrile solution and within the pMEA matrix following exposure to low-power 365 nm irradiation. Photo-liberation of drug from pMEA into phosphate buffered saline was monitored using UV-vis spectroscopy.

Results

The synthetic procedures yielded the desired drug conjugates with full supporting characterisation. Drug regeneration through photolysis of the synthesised conjugates was successful in both acetonitrile solution and within the pMEA scaffold upon UV irradiation. Conjugates were retained within the pMEA scaffold with exclusive drug liberation following irradiation and increased drug dose with increasing exposure. Multi-dosing capacity was demonstrated though the ability of successive irradiation periods to generate further bursts of drug.

Conclusion

This study demonstrates the first application of photochemically controlled drug release from a biomaterial coating and the feasibility of using pMEA as a scaffold for housing the photoactive drug-DMB conjugates.

Polymer Brushes Containing Sulfonated Sugar Repeat Units: Synthesis, Characterization and In Vitro Testing of Blood Coagulation Activation

A new polymer brush chemistry containing sulfonated carbohydrate repeat units has been synthesized from silicon substrates using ATRP methods and characterized both in bulk and using surface analysis. The polymer brush was designed to act as a mimic for the naturally occurring sulfonated glycosaminoglycan, heparin, commonly used for modifying blood-contacting surfaces both in vitro and in vivo. Surface analysis showed conversion of brush saccharide precursor chemistry to the desired sulfonated polymer product. The sulfonated polymer brush surface was further analyzed using three conventional in vitro tests for blood compatibility -- plasma recalcification times, complement activation, and thrombin generation. The sulfonated polymer brush films on silicon oxide wafers exhibited better assay performance in these blood component assays than the unsulfonated sugar functionalized polymer brush in all tests performed.