Effect of crystallinity of condensation polymers on platelet adhesion

Various polyamides and polyesters having different numbers of methylene groups in their repeating units have been synthesized and their blood compatibilities have been evaluated in terms of the adhesion behavior of blood platelets on the surface of these condensation polymers by a micro-sphere-column method. The number of methylene groups in the repeating units of polyamides and polyesters influenced the adhesion behavior of platelets and there was an optimum number of methylene groups each in polyamides and polyesters. Poly(hexamethylene terephthalamide) and poly(pentamethylene terephthalate) adsorbed platelets in the smallest number in the polyamide and polyester series, respectively. Blood platelets were adsorbed on polyamides in smaller numbers than on corresponding polyesters. It was found that the platelet adhesion on the surface of polyamides and polyesters was closely related to their crystallinities and the number of the adsorbed platelets decreased linearly with increasing their relative crystallinity.     

Syntheses of functional condensation polymers. II. A polyamide having epoxy groups and its ring-opening derivatives

Polyamides having epoxy groups and their ring-opening derivatives were prepared and characterized, and some of their properties were investigated. Reaction conditions for the low-temperature polycondensation of cis-2,3-epoxysuccinyl chloride (ESC) with aromatic diamines and the interfacial copolycondensation of ESC and adipyl chloride (AC) with aromatic diamines were established to obtain a high molecular weight polyamide having epoxy groups. In addition, the ring-opening reactions of the epoxy groups in the polyamides were carried out with various amines in order to obtain polyamides having hydrophilic pendent groups such as amino and hydroxyl. It was found that the polyamides prepared by ring-opening reaction of the epoxy group with ethylenediamine (EDA) or ethanolamine (EA) had a higher affinity for moisture than those with hexamethylenediamine (HMD) or n-butylamine (n-BA), which might be ascribed to the distance of hydrophilic groups from the polyamide chain. Those polyamides having hydrophilic pendent groups decomposed upon heating at less than 200°C.     

Chemical stability of some poly(amide imide) type polymers

The stability of some heterocyclic poly(amide imide)s in acidic and alkaline medium was compared to the structurally related polyimide and poly(amide imide)s without other heterocyclic groups. All the polymers have high stability in acidic medium. The introduction of additional heterocycles such as 1,3,4-0xadiazole or phenylquinoxaline into the macromolecular chain of a poly(amide imide) increases substantially the resistance to alkaline medium. Polyamides containing imide rings only in the side chain are more stable to hydrolysis than related polyamide having imide units in the main chain.     

Amphiphilic networks

Platelet adhesion to and blood coagulation activation by amphiphilic networks (i.e., water soluble acrylates crosslinked by hydrophobic polyisobutylene) have been investigated in reference to polyethylene (PE) and poly(vinyl chloride) (PVC) controls in vitro. Among the amphiphilic networks examined, that containing poly(N,N-dimethylacrylamide) exhibited lowest thrombogenicity and showed significantly lower platelet adhesion than PVC, i.e., the reference with the lowest thrombogenicity. The amphiphilic network containing poly(2-dimethylaminoethyl methacrylate) exhibited less thromboresistance as judged by the adherence of a large number of procoagulant platelets. According to these findings precisely tailored amphiphilic networks may give rise to materials with blood compatibility superior to those currently in use.     

Clotting Phenomena at the Blood-Polymer Interface and Development of Blood Compatible Polymeric Surfaces

In the past two decades many attempts have been made to relate surface and interfacial parameters with the blood compatibility of polymeric surfaces. It is however doubtful if by a single parameter the behaviour of blood on a surface can be predicted. Two major aspects of blood compatibility—the prevention of platelet adhesion and the deactivation of the intrinsic coagulation system are determined by the measure and nature of competitive blood protein adsorption on the foreign surface. The adhesion of blood platelets is promoted by adsorbed fibrinogen and gamma globulin, while adsorbed albumin inhibits platelet adhesion. Heparinised surfaces do not adsorb fibrin and consequently no adhesion of platelets takes place. Other surfaces with low platelet adhesion are the hydrogels, certain block copolyetherurethanes, polyelectrolyte complexes and biolised proteins. Heparinised surfaces of the cationically bonded type inhibit the intrinsic coagulation as well, however this may be due to unstable coatings and heparin leakage. In the authors laboratory a synthetic heparinoid was prepared with the structure - [CH₂ - C(CH₃ NHSO₃ Na - C(H) COONa - CH₂ -] x? with M?_w = (7.5 /pm 1.0) × 10⁵ and an in vivo anticoagulant activity of 50% of heparin. Its coatings on PVC, using tridodecylmethyl-ammonium chloride as a coupling agent, are stable in plasma and salt solutions and provide surfaces which show negligible platelet adhesion and a strong inhibition of the intrinsic coagulation on contact with blood. Similar results were found with polydimethylsiloxane surfaces coated with this heparinoid.     

Builder performance in detergent formulations and biodegradability of partially dicarboxylated cellulose and amylose containing sugar residues in the backbone

Poly(sodium carboxylate)s containing varying amounts of unreacted sugar residues as biodegradable segments in the polymer backbone were prepared by the partial oxidation of amylose and cellulose using periodic acid/chlorite. It was found that dicarboxy polysaccharides containing sugar residues showed improved biodegradability comparing to those having no sugar blocks in the polymer chain, and their biodegradability varied according to the glucopyranose content or the degree of dicarboxylation. Dicarboxy polysaccharides containing more than 60% glucopyranose residues tended to biodegrade quickly. When compared on an equal glucopyranose content basis, the biodegradability of dicarboxy amylose (2b) was slightly superior to that of dicarboxy cellulose (2a) . The builder performance in detergents was dependent on the degree of dicarboxylation, and a clear relation between the detergency and the content of carboxylate groups was observed. Dicarboxy polysaccharides with more than 40% dicarboxylation showed better builder performance than those of disodium 3-oxapentanedioate and trisodium citrate, with some of them superior to that of sodium tripolyphosphate (STPP). The detergency of 2b was more effective than that of 2a . It was also found that the detergency was improved much by increasing the amount of polymeric builder.     

An inelastic electron tunnelling spectroscopy (IETS) study of poly(vinylacetate) poly(methyl methacrylate) and poly(vinylalcohol) adsorbed on aluminium oxide

IETS is used to investigate the adsorption of poly(vinylacetate) (PVA), poly(methylmethacrylate) (PMMA), and poly(vinylalcohol) (PVOH) on aluminium oxide. These polymers are of interest in the field of adhesion science, and until now synthetic macromolecules have not been studied in this way. Both commercially available polymers and those synthesized in our laboratory have been used. On the basis of IET spectra presented here, and existing i.r. spectra it is believed that PMMA and PVA undergo ester cleavage at the oxide surface leading to their subsequent adsorption. For PMMA this is thought to be via carboxylate anions generated on the polymer side groups, while PVA is expected to be adsorbed as PVOH. Bonding of PVOH to the oxide is not fully understood, but may occur by the formation of an AlOC bridge. Another possibility for the above polymers, that of intermolecular hydrogen bonding between polar polymer side groups, and adsorbed hydroxyl species present on the oxide surface, cannot be ruled out.     

Adhesive monomers to dental ceramics. II. Methacrylamide derivatives containing carboxyl and phenyl groups for effective adhesion of calcium metaphosphate ceramic

Twelve methacrylamide derivatives containing carboxyl and phenyl groups have been evaluated as adhesives for calcium metaphosphate ceramic, a promising but hard-to-adhere cast ceramic restoration material. Although methacrylamide monomers having a carboxyl group showed low adhesive tensile strength for the ceramic, contrary to the glycidyl methacrylate derivatives, the monomer having neighboring two carboxyl groups at the phenyl ring exhibited quite high adhesion. Moreover, the monomer proved to retain high adhesion strength for the surface-etched ceramic for a long period of time even in water and would thus be suitable for practical clinical applications. © 1994 John Wiley & Sons, Inc.     

Relationship between electron sensitivity and chemical structure of polymers as EB resists. I. Electron sensitivity of various polyamides

Polyamides containing double bonds or epoxy groups were synthesized and evaluated as electron beam (EB) resists, in order to find the relationship between electron beam sensitivity and chemical structure of the polyamides. It was found that polyamides containing double bonds, which have good solubility, are easily crosslinked by the electron beam exposure. The sensitivity of a polyamide with 70 mol% of the repeat units containing double bonds was equivalent to that of a 100% unsaturated polyamide which contained double bonds of 100% molar ratios, and thus it is not necessary that the polyamide be a homopolymer of unsaturated repeating units. The polyamides have good physical properties, and are adaptable to dry etching processes.     

Crosslinking of polypropylene glycol with divalent metal salts of mono(hydroxyethyl) phthalate,anhydride, and bisepoxide

Crosslinking of polypropylene glycol with divalent metal salts of mono(hydroxyethyl) phthalate, anhydride, and bisepoxide is investigated. The anhydride and bisepoxide were hexahydrophthalic anhydride and bisphenol A diglycidyl ether. The metal carboxylate groups catalyzed the crosslinking reactions. The Mg carboxylate group showed higher catalytic activities than the Ca carboxylate group. The rubbers containing Mg showed much better physical properties than those containing Ca, due to higher interionic attraction of Mg⁺⁺ and better homogeneity. In addition, tensile strength of the cured rubbers at about the same soft block contents depended largely upon that of the hard block. Resistances to water and chemical attack, stress–relaxation, and thermal behavior are also discussed.     

Changes in Protein Adsorption/Desorption on Albuminated Surfaces Due to Cyclic-AMP Release

The major problem facing the development of a small diameter vascular graft (<5 rnm diameter) to be used for the replacement of a coronary artery is thrombogenicity at the interface. When blood comes in contact with an artificial surface, the initial event occurring is the adsorption of plasma proteins on the surface [1, 2], followed by adhesion of platelets and activation of the clotting mechanism resulting in thrombus formation [3,4]. The concentration of the various proteins adsorbed is largely dependent on the surface properties of the material.     

Adhesion of blood platelets under flow to wettability gradient polyethylene surfaces made in a shielded gas plasma

Adhesion and activation of platelets are important steps in the thrombosis of blood after contact with a biomaterial surface and are governed, in part, by the wettability of the surface. Since most implanted devices are in contact with blood under flow conditions, it is important to study the effect of wettability of device surfaces on the behavior of platelets also under flow. To this end, wettability gradient polyethylene surfaces were prepared through glow discharge with partial shielding over a length of 5 cm, with advancing water contact angles varying from 95 to 45 degrees and a contact angle hysteresis of 30 degrees. The role of blood flow on the adhesion of platelets was examined by incubating these gradient surfaces in anticoagulated, whole human blood under static conditions or in blood under a flow of 10 or 40 ml/min through a 3 mm diameter circuit or for 5 or 15 min with either the hydrophobic or hydrophilic end upstream. Generally, more platelets adhered on the hydrophilic end of the wettability gradient than on the hydrophobic end, although the increment along the wettability gradient was dependent on both the flow conditions and direction. More platelets adhered under a flow of 10 ml/min than under static conditions, due to higher mass transport. Especially when the hydrophilic end was upstream, there was a more pronounced adhesion. This can be explained in terms of immediate platelet activation by shear stress imposed at the upstream end. During flow of 40 ml/min, platelet adhesion on an upstream hydrophilic end was less than on a downstream hydrophilic end. We conclude that platelets detach from the hydrophilic end at high shear stress due to the spherical form of adhered platelets. Platelets on the hydrophobic end could withstand detachment by strong, flat shaped platelet-material contact.     

Crosslinking of partially neutralized carboxyl-terminated liquid rubbers with bisepoxide and anhydride

Crosslinking of partially neutralized carboxyl-terminated liquid rubbers (PNCTLR) with bisepoxide and anhydride was investigated by the PNCTLR–bisepoxide–anhydride reactions. The PNCTLR were prepared, by the partial neutralization with MgO and CaO, from a polymer of butadiene (Hycar CTB 2000X162) and a copolymer of butadiene–acrylonitrile (Hyca? CTBN 1300X8). As the bisepoxide, bisphenol-A diglycidyl ether was used, and hexahydrophthalic anhydride was the anhydride used. It was found that the metal carboxylate groups of PNCTLR catalyze the crosslinking reactions, and, further, the Mg carboxylate group showed higher catalytic activities than the Ca carboxylate group. As for the physical properties of the cured rubbers obtained, the rubbers containing Mg showed higher tensile strength and Shore A hardness than those containing Ca. In addition, the CTBN-series cured rubbers showed better physical properties than those of the CTB-series, because of a polarity effect of nitrile groups in the former rubbers. Resistances to water and chemical attack, thermal behavior, and stress relaxation are also discussed.     

Study on thermoplastic polyurethane/polypropylene (TPU/PP) blend as a blood bag material

Blends with different ratios of thermoplastic polyurethane/polypropylene (TPU/PP) were prepared by melt mixing using an internal Haake mixer. Properties of the blends were investigated using SEM micrographs of cryofractures and measurement of the mechanical strength, water absorption, cell culture, and platelet adhesion in vitro tests, which were compared with those of PVC blood bags. The effect of the addition of the ethylene–vinyl acetate (EVA) copolymer on the TPU/PP blend properties was investigated. The results indicated that a TPU/PP/EVA = 80/20/5 blend can be used as a new blood bag material. It was observed that the blend is homogeneous with higher mechanical strength than that of the commercial PVC blood bag. This blend also showed a compatible cell response in contact with L929 fibroblast cells and fewer tendencies to interaction with platelets compared to the PVC blood bag. Although the blends were immissible and no chemical reaction at the interface could be found, the blood compatibility of the blends were improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2496–2501, 2003     

The correlation between froth flotation response and collector adsorption from aqueous solution. Part I. Titanium dioxide and ferric oxide conditioned in oleate solutions

Samples of pure ferric oxide and titanium dioxide have been conditioned in aqueous oleate solutions over the pH range 2–12. The extent of oleate adsorption was determined from the heat of combustion of the adsorbed film, using DTA. Adsorption isotherms have been constructed at pH values above and below both the pK of oleic acid and the isoelectric points of the oxide surfaces.It appears that at low oleate concentrations, adsorption is due to negatively charged carboxylate ions interacting with positively charged surface sites. When sufficient surface has been covered with hydrophobic hydrocarbon chains, froth flotation becomes possible. With increasing oleate concentration, competition for positive sites forces the adsorbed ions into a vertical orientation, thereby exposing some previously covered surface. Once the positive sites have been “neutralised”, subsequent adsorption must occur at neutral or negative parts of the surface. This is likely to involve mutual attraction between the hydrocarbon groups of vertically adsorbed oleate ions, and those of oleate ions in solution. Newly adsorbed oleate ions would then be expected to be oriented with their negatively charged carboxylote groups away from the surface. Hence, increasing adsorption, as the collector concentration is increased, will lead to the surface becoming progressively less hydrophobic, and froth flotation may cease.     

Flocculation Mechanism of Synthetic Goethite Suspension Using Hydroxamated Polymer and Sodium Polyacrylate

The flocculation effects of homemade hydroxamated flocculant(HPAA)and commercially available sodium polyacrylate(PAAS)on synthetic goethite suspensions with different solid contents were studied.The adsorption mechanism of HPAA or PAAS on the surfaces of goethite was investigated.The settling rate of 50 g/L goethite suspension with HPAA(1.74 m/h)was faster than that with PAAS(0.54 m/h),which indicated that HPAA exhibits better flocculation performance than PAAS does.It could be found that the stretching vibration of carbonyl band in hydroxamic acid groups of HPAA was downshifted from 1 654 cm~(-1) to 1 645 cm~(-1) and a new adsorption band appeared at 1 455 cm-1,which demonstrated that a five-membered ring chelate may be formed among iron atoms of goethite surfaces,the hydroxyl groups and the carbonyl groups in hydroxamic acid groups of HPAA.In the case of PAAS,the separation of the asymmetric and symmetric stretches of the carboxylate groups in adsorbed PAAS was 163 cm-1,which was greater than that of unadsorbed PAAS with 157 cm~(-1).There was no indication of a contribution from the monodentate adsorption between iron atoms of goethite surfaces and carboxylate groups of PAAS,but there may exist a bi-dentate bridging structure.Compared with synthetic goethite,XPS curve fittings of Fe 2p spectra showed that the binding energies of the main Fe 2p3/2 and Fe 2p1/2 resolved peaks on HPAA-treated goethite surfaces were correspondingly decreased by 0.9 and 0.7 e V,while those on PAAS-treated goethite surfaces were correspondingly decreased by 0.7 and 0.3 e V.The characteristic N 1s peak of HPAA and C 1s peak of PAAS were correspondingly detected on HPAA-treated and PAAS-treated goethites,and a binding energy change of N 1s spectrum of adsorbed HPAA was observed.The relative atomic ratios of C/Fe,N/Fe and O/Fe on HPAA-treated and PAAS-treated goethite surfaces were increased.All the results suggested that HPAA or PAAS was adsorbed on the goethite surfaces by the chemisorption,and a stronger adsorption of HPAA on the goethite surfaces happened than that of PAAS.     

Detection of lead ion binding on bifunctional chelating/ion‐exchange resins by cross‐polarization/magic‐angle spinning solid‐state nuclear magnetic resonance

Solid‐state nuclear magnetic resonance (S‐NMR) can reveal much useful information, including conformations, stereoregularity, defect structures, and comonomer sequence. S‐NMR is especially useful for revealing microstructural differences that can alter local polymer chains. A series of bifunctional chelating/ion‐exchange resins, containing differing ratios of iminodiacetic acid to acetic acid, were synthesized. Cross‐polarization magic‐angle spinning (CP/MAS) ¹³C‐NMR was employed to measure conformation changes both before and after the bonding of ligands and lead ion adsorbed on bifunctional chelated/ion‐exchange resins in this investigation. From the ¹³C‐NMR spectra, as the lead ion was adsorbed by the iminodiacetic acid chelating group, the motion of molecular chain would be inhibited and the resonance peaks of the carboxylate anion at 170 ppm would shift downfield. Compared to the FTIR results, the downfield shift of the resonance peaks indicated that the bonding of carboxylate anion and lead ion adsorbed displayed an ionic trend. Furthermore, the bonding of the carboxylic group and lead ion adsorbed changed from ionic to covalent as the chelating group in bifunctional/ion‐exchange resins decreased. The linear relationship between the areas of those resonance peaks and the amount of lead ion adsorbed was obtained from the spectra fitting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 919–928, 2002     

Study of hemocompatibility and endothelial cell interaction of tecoflex-based electrospun vascular grafts

Abstract

Ensuring long-term functioning and efficient endothelialization of small diameter vascular grafts (VG) is an urgent task of tissue engineering. A solution may be to use electrospun VGs prepared from blends polyurethane with gelatin and/or bivalirudin. Here, properties of 3D matrices were explored by SEM, contact angle measurements and IR spectroscopy, and their interaction with blood and endothelial cells was studied. Introduction of gelatin into matrices enhanced adhesion and proliferation of endotheliocytes and enabled adhesion of platelets, whereas bivalirudin inhibited platelet adhesion while having no negative effect on the adhesion and proliferation of endothelial cells.     

Adhesion Between Rubber Compounds and Copper-film-coated Steel Plates

Three copper-film-coated steel plates (abbreviated hereafter as copper-coated plate) with different thicknesses of copper film 30 to 90 nm were prepared and their adhesion properties to rubber compounds were examined. The high adhesion of copper-coated plates to the rubber compound containing resinous bonding additives was obtained at normal and over-cure conditions The copper-coated plate containing an amount of copper coating sufficient to plate the surface with a uniform copper layer showed better adhesion than that having a small amount of copper coating on its surface. The stability against green humidity aging and the cause for the high adhesion of the copper-coated plate were discussed compared with those of the brass plate.     

Adhesion Between Rubber Compounds and Copper-film-coated Steel Plates

Three copper-film-coated steel plates (abbreviated hereafter as copper-coated plate) with different thicknesses of copper film 30 to 90 nm were prepared and their adhesion properties to rubber compounds were examined. The high adhesion of copper-coated plates to the rubber compound containing resinous bonding additives was obtained at normal and over-cure conditions The copper-coated plate containing an amount of copper coating sufficient to plate the surface with a uniform copper layer showed better adhesion than that having a small amount of copper coating on its surface. The stability against green humidity aging and the cause for the high adhesion of the copper-coated plate were discussed compared with those of the brass plate.