Affinity binding macroporous monolithic cryogel as a matrix for extracorporeal apheresis medical devices

Cytapheresis is an extracorporeal separation technique widely used in medicine for elimination of specific classes of blood cells from circulating blood. It has been shown recently to have clinical efficacy in various disease states, such as leukaemia, autoimmune disorders, rheumatoid arthritis, renal allograft rejection and sickle–cell anaemia. The current study was undertaken to produce an affinity-binding column, based upon a macroporous monolithic cryogel with a structure of interconnected pores, with pore size and low flow resistance potentially suitable for use in cytapheresis. The affinity column was produced from poly (2-hydroxyethyl methacrylate) PHEMA cryogels synthesized by free radical polymerization at -12°C.This study involved assessing haemolytic potential, and functionalisation of polymer matrix with biological ligands. Haemolytic potential of poly (2-hydroxyethyl methacrylate) cryogel was established by measuring free haemoglobin after blood filtration through the column. The anti-human albumin (antibody) was chemically coupled to the epoxy derivatised monolithic cryogels and the binding efficiency of anti-human albumin (antibody) to the cryogel was determined. Our results show that approximately 100% of Red blood cells passed through the column with no evidence of haemolysis found in blood eluted. It was found that ~82% of human serum albumin was retained on the monolithic IgG anti-human albumin cryogel matrix. The obtained results suggest that poly (2-hydroxyethyl methacrylate) monolithic cryogel is a non-haemolytic material (haemocompatible matrix) capable of functionalisation with antibody and thus can be an appropriate matrix for use in extracorporeal apheresis system

Development of Cu-Modified PVC and PU for Catalytic Generation of Nitric Oxide

Nitric oxide (NO) generating surfaces are potentially promising for improving haemocompatibility of blood-contacting biomaterials. In the present report, Cu-modified poly(vinyl chloride) (PVC) and polyurethane (PU) were prepared via polydopamine (pDA)-assisted chelation. The copper content on the PVC and PU modified surfaces, assessed by inductively coupled plasma - optical emission spectrometry (ICP-OES), were about 3.86 and 6.04 nmol·cm−2, respectively. The Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) data suggest that copper is attached to the polymer surface through complex formation with pDA. The cumulative leaching of copper from modified PVC and PU during the five day incubation in phosphate buffered saline (PBS), measured by inductively coupled plasma mass spectrometry (ICP-MS), was about 50.7 ppb and 48 ppb, respectively which is within its physiological level. Modified polymers were tested for their ability to catalytically generate NO by decomposing of endogenous S-nitrosothiol (GSNO). The obtained data show that Cu-modified PVC and PU exhibited the capacity to generate physiological levels of NO which could be a foundation for developing new biocompatible materials with NO-based therapeutics

Adsorption of Bovine Serum Albumin on Carbon-Based Materials

The protein adsorption plays a very important role in biotechnology, biomolecular engineering and it is one of the main factors determining bio- and hemocompatibility of biomedical materials in medical applications, such as blood purification and wound healing. Here we report adsorption properties of two carbon-based materials, thermally expanded graphite (EGr) and graphene nanoplatelets (GnP), for bovine serum albumin (BSA), the most abundant blood plasma protein. The influence of the surface chemistry of expanded graphite on the mechanism of BSA adsorption was studied by using EGr modified with oxygen or nitrogen functionalities. Having low microporosity and the specific surface area in the range of 5 to 50 m2/g, the expanded graphite exhibits high protein adsorption capacity at high equilibrium concentrations, which makes this material a potential candidate for biomedical applications as a carrier for high molecular weight (HMW) drug delivery or adsorption of HMW metabolites. At low equilibrium concentrations, the effect of specific protein-surface functional groups interaction reveals the differences between the adsorption affinity of different surface modified EGr materials to BSA. The adsorption of BSA on GnP with a specific surface area of 286 m2/g and a developed micro-/mesoporous structure did not follow the same mechanism as seen with EGr materials. At low equilibrium concentration of BSA, GnP exhibits high adsorption efficiency. An important finding is that no release of nanoparticles from expanded graphite adsorbents was observed, which makes them potentially suitable for direct contact with blood and other tissues while very small nanoparticles were noticed in the case of graphene nanoplatelets

Poly (2 hydroxyethyl Methacrylate) Macroporous Cryogel For Extracorporeal Medical Devices

Poly (2-hydroxyethyl methacrylate) PHEMA monolithic cryogels were synthesized by free radical polymerization at -12°C for 18 hours and produced spongy, elastic and macroporous gel matrix. Scanning Electron Microscopy (SEM) measured structural properties of PHEMA monolithic cryogel matrix to visualize pore morphology. Mechanical properties of PHEMA monolithic cryogel such as storage modulus, compressive modulus, and creep test were measured with Dynamic mechanical analyzer (DMA). The PHEMA monolithic cryogel matrix shows ~ 97% recovery after 70% compression of cryogel and has a compressive modulus of 1.8kPa to 8.5kPa

Small angle neutron scattering study of globular proteins confined in porous carbons

International audienceThis article reports measurements of the concentration distribution of two model proteins adsorbed from aqueous solution by two different high surface area carbons, using small angle neutron and X-ray scattering (SANS and SAXS). The proteins investigated were bovine serum albumin (67 kDa), and bovine pancreatic trypsin inhibitor (BPTI), also known under the name aprotinin (6.5 kDa). The two carbon substrates were C1, an open structured carbon aerogel derived from a resorcinol– formaldehyde polymer aerogel, and C2, a commercial nanoporous carbon from MAST Carbon (UK). Although both C1 and C2 possess a high proportion of pores that are either closed or inaccessible to low temperature nitrogen vapour, the size distribution of the accessible pores is broad enough to accommodate BSA molecules. In C1, which is hydrophobic, the BSA molecules migrate individually into pores that are compatible with their size, whereas BPTI forms clusters having the same size as BSA. With C2, the hydrophilic internal surface limits the adsorption efficiency. The strong adhesion of proteins to hydrophilic surfaces prevents diffusion of either molecule into the micro-and nanopores. In this sample both BSA and BPTI form large clusters. These observations have relevance in biomedical applications, such as haemoperfusion or as a medium for protein storage

Synthesis of the polymerizable room temperature ionic liquid AMPS – TEA and superabsorbency for organic liquids of its copolymeric gels with acrylamide

A polymerizable room temperature ionic liquid (RTIL), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) – triethylamine (TEA), was synthesized by neutralization of AMPS with TEA in acetone followed by evaporation of the solvent under a reduced pressure at room temperature. The RTIL was characterized with fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and 1H NMR. Co-polymeric gels of the RTIL with acrylamide (AAm) were prepared by aqueous solution polymerization using N,N′-methylenebisacrylamide as a crosslinker, and ammonium persulfate as an initiator. Superabsorbency of the gels in aqueous and a series of organic liquids was investigated gravimetrically. DSC data showed that the glass transition temperature of AMPS – TEA was 59.4 °C. Poly (AMPS – TEA-co-AAm) gels exhibited superabsorbency in both water and a series of organic solvents. The mechanism for swelling in aqueous and organic media of the gels was critically discussed