Heparin-poly protein

Surface block-graft-copolymerization, based on the photochemistry of N, AT-diethyldithiocarbamate has been applied to precisely design biocompatible and functional surfaces (patterns of immobilized heparin or proteins), as well as block-grafted surfaces on polystyrene [83]. Polystyrene surfaces have also been patterned by immobilization of poly(Af-isopropylacrylamide) by photolithography, and subsequently used for regiospecific cell attachment [84]. Surface modification of polydimethylsiloxane microfluidic devices by UV induced polymer grafting improved the stability of the electroosmotic mobility and improved electrophoretic resolution of peptides [85]. 

Implanted polymeric materials can also adsorb and absorb from the body various chemicals that could also effect the properties of the polymer. Lipids (triglycerides, fatty acids, cholesterol, etc.) could act as plasticizers for some polymers and change their physical properties. Lipid absorption has been suggested to increase the degradation of silicone rubbers in heart valves (13). but this does not appear to be a factor in nonvascular Implants. Poly(dimethylsiloxane) shows very little tensile strength loss after 17 months of implantation (16). Adsorbed proteins, or other materials, can modify the interactions of the body with the polymer this effect has been observed with various plasma proteins and with heparin in connection with blood compatibility. 

The excellent sorption capacity of the hypercrosslinked mesoporous poly-DVB with respect to selective removal of P2M from its mixtures with albumin and other semm proteins, combined with superior hemocompat-ibility of the beads surface modified with poly(N-vinyl)pyrrolidone, justified the manufacturing of an experimental batch of the material for initial clinical studies. The polymer was named BetaSorb (RenalTech International, USA) and was used in 300 mL cylindrical polysrdfone devices that were steam-sterilized and filled with normal saline containing 1000 lU heparin. The device was placed in line with the dialysis circuit, upstream of the dialyzer, in order to not affect the pressure drop across the dialyzer membrane. The blood flow was maintained at the customary value of 400 mL/ min, again the optimal flow rate for the dialyzer. The complete setup of the combined hemoperfusion-hemodialysis treatment [361] is displayed in Fig. 15.2. 

Heparin, a natural protein, is an important constituent of blood and contributes to blood clotting. When circulatory assist devices were first proposed, it was found that the artificial surfaces promoted unnatural thrombosis. An important proposed solution to the problem involved grafting heparin to the surfaces of the materials involved, including such polymers as poly(vinyl chloride) and poly(dimethyl siloxane) (Artificial Heart Program, 1968 Lyman, 1966 Sears, 1965). 

Cellulose acetate membrane [69] and cellulose fiber [70] were coated on PPy to remove gold iodide and Cr(VI), respectively. Ionic exchange was ascribe for the gold iodide removal and the reduction of Cr(VI) to Cr(III), followed by adsorption. A covalently immobilized heparin-PPy/ poly(ethylene glycol) methacrylate composite was also fabricated for biological applications to reduce the protein and thrombus formation [71]. 

Jeon O, Song SJ, Kang SW. Enhancement of ectopic bone formation by bone morphogenetic protein-2 released from a heparin-conjugated poly (L-lactic-co-glycolic acid) scaffold. Biomaterials 2007 28 2763-71. 

Addition of low concentrations of various macromolecular polyanions [notably poly-L-glutamate, poly-L-aspartate, or heparin at pH 7.4, or poly(A) at pH 6.5] under conditions that do not result in nonenzymatic precipitation of vesicular secretion proteins markedly enhances... 

Our laboratory has been involved in the identification and characterization of the transcription factors for RNA polymerase I (Pol I)-directed transcription of ribosomal RNA genes (rDNA). To this end, we initially isolated and partially purified a transcriptionally active protein complex which contains RNA polymerase I and the essential Pol I transcription factors (1). Such a fraction was obtained from whole ceU extracts (1) or from nuclear extracts (2). Subsequently, we demonstrated that a fraction obtained during chromatography of the cell extract on a heparin sepharose coliunn could prevent nonrandom transcription of cloned rat rDNA in an in vitro system (3). The major protein in this fraction exhibited characteristics of purified poly(ADP-ribose) polymerase. The present report summarizes the properties of this protein, and describes experiments showing the dramatic appearance of accurately initiated transcript in an unfiractionated whole ceU extract or nuclear extract from a tissue foUowing addition of the protein factor. 

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