Coating of commercially available materials with a new heparinizable material.

Different commercial materials, such as polyurethane (PU), plasticized PVC (PVC), glass, Gore-tex, and Dacron, were coated with a well-characterized biomaterial (PUPA) based on polyurethane and poly(amido-amine) components. Two different classes of coating were obtained due to the different characteristics of the substrates. In the case of PVC and polyurethane which are soluble in the solvent of the PUPA-coating solution, there was penetration and blending of the coating and underlying materials. In the case of glass, Gore-tex, and Dacron, which are insoluble in the solvent of the coating solution, only a superficial layer of PUPA could be obtained. The coating stability was investigated and the interaction between coating and underlying material studied by FT-IR. All the stable coatings showed the ability to bind as much heparin as PUPA material by itself.

Heparinized polyurethane surface through ionic bonding of heparin.

Surface heparinization through an ionic bond is one of the methods used to improve polyurethane blood compatibility. Chains of poly(amido-amine), a tertiary aminic polymer capable of forming stable complexes with heparin, were either surface-grafted on polyurethane or interconnected with polyurethane chains using hexamethylenediisocyanate as cross-linking agent. In the latter case, a new material (PUPA) is formed with a heparin adsorbing capacity higher than poly (amido-amine) surface-grafted polyurethane. By changing the percentages of the components, different series of PUPA materials can be obtained with different physico-chemical properties. The ATR/FT-IR technique was used to characterize the new materials in the native and in the heparinized state. PUPA solution was used to coat commercial biomedical devices and they were also characterized physicochemically using ATR/FT-IR.

Synthesis and physicochemical characterization of a new material (PUPA) based on polyurethane and poly(amido-amine) components capable of strongly adsorbing quantities of heparin.

The synthesis of new materials (PUPAs) based on a commercial polyurethane and a heparin-complexing polymer, poly(amido-amine), was studied. PUPAs are capable of adsorbing heparin because the basic nitrogens of poly(amido-amine), once protonated, interact with the negative charges carried by the heparin molecule. Six different samples of PUPA were synthesized having a varied ratio of the components. The quantity of basic nitrogen on the surface and the bound heparin for each sample was determined. Two different kinds of heparin are present on a PUPA surface: one is strongly bound but can be detached by 0.1 M NaOH solution, the other is physically adsorbed and is slowly released by a stream of saline solution. A relationship between the quantity of strongly bound heparin and basic nitrogen was found. SEM and FTIR-ATR analysis were performed on all the PUPA samples. The mechanical characteristics change according to chemical composition.

A material (PUPA) presenting both the properties of polyurethanes and the capacity of adsorbing a high quantity of heparin.

Polyurethanes are widely used for biomedical applications, but there is still a constant search for improved blood-compatible materials. We studied a material (PUPA) obtained by the interconnection between a poly(amido-amine), N2LL, capable of forming stable complexes with heparin and a commercial polyurethane, Pellethane 2363-80AE, using hexamethylenediisocyanate as the crosslinking agent. The amount of absorbed heparin (evaluated by biological tests) was generally much higher than that found on the poly(amido-amine) surface-grafted polyurethane.

Heparinizable graft copolymers from chlorosulphonated polyethylene with poly(amido-amine) segments.

The synthesis and the physical characterization of three graft copolymers (PES/PAA) obtained from chlorosulphonated polyethylene (PECS) and three different secondary amino end-capped poly(amido-amine)s are reported. The properties of these heparinizable materials appear to be suitable for constructing prosthetic devices for biomedical use. The heparin adsorbing ability and the stability of the complex with heparin of the three copolymers have been evaluated, by means of biological tests, as activated Partial Thromboplastin Time (PTT) and Thrombin Time (TT).

Heparinizable materials (IV). Surface-grafting on poly(ethylene terephthalate) of heparin-complexing poly(amido-amine) chains.

By a chemical process poly(amido-amine) chains have been grafted on the surface of poly(ethylene terephthalate) (Dacron) devices. After treatment, it was shown that the devices could adsorb significant amounts of heparin. Most of the adsorbed heparin can be recovered only by eluting at pH greater than 10 with NaOH solution.

Heparinizable materials (III). Heparin retention power of a poly(amido-amine) either as crosslinked resin, or surface-grafted on PVC.

The retentive power of a poly(amido-amine), in the form of a highly hydrophilic crosslinked resin, has been evaluated at different pH's. The resin releases heparin quantitatively in a very narrow pH range (10.8-11.4). This poly(amido-amine) has also been grafted on PVC tubes, and the heparin-adsorbing capacity of the materials so obtained has been tested biologically. In this case heparin is only released at pH greater than 10 so confirming the strong interaction between our polymer and heparin.