(516aw) Improved Stability Of Cysteine Modified Haemocompatible Polymer

A cysteine modified haemocompatible polymer was made by attaching cysteine on the polymer surface. Previous studies showed that this polymer can use endogenous nitric oxide (NO) resource (S-nitrosothiol) to inhibit platelet adhesion on the polymer surface through the transnitrosation and S-nitrosocysteine self-decomposition reaction. NO is well known for its platelet inhibition effect.

The previous attaching method utilized the imine bond formation between the amine group of cysteine and the glutaraldehyde grafted polymer. However, this bond is unstable in the water and tends to be hydrolyzed thus causing cysteine being detached from the polymer in the aqueous solution. An improved method for attaching the polymer was developed by peptide bond formation between the amine group on the polymer and carboxylic group of cysteine. Chemiluminescence method showed taht this peptide bond is stable in both water and acidic condition. And cysteine is no longer detached from the polymer surface. Further study showed that cysteine on the new polymer can be regenerated by DTT solution after being oxidized.

Another potential problem of the previous cysteine modified polymer is the surface cracks. The polymer has to be aminolyzed and then modified by glutaraldehyde. The aminolysis process caused a lot of cracks on the polymer thus interfere with the mass transfer between the cysteine on the polymer and nitroso-albumine in the solution. A modified method was developed by introducing carboxylic group on the polymer and then forming peptide bone between the polymer and the cysteine. This method can also form stable cysteine on the polymer but has lower cysteine surface concentration.

Future studies include optimizing the peptide bond formation procedure to maximize the cysteine surface concentration and the kinetics study of the transnitrosation reaction between the cysteine modified polymer and the nitroso-albumine.