Preparation Of A LDL-selective Adsorbens And Its Properties

Cerebrovascular disease is still the major one threatening the human health and life; artherosclerosis proves to be the close factor leading to the onset and exacerbation of the cerebrovascular ones; the abnormal increase of low-density lipoprotein (LDL) has been clinclally comfirmed to be an independent risk factor for the disease.At present, the current therapies for lowering the level of LDL are of medicine, alimentary control and blood purification. However, if the patient's level of LDL has abnormally increased over 300mg/dL, or for the familial hyperlipidemic patients, the therapy of blood purification is currently the most efficient one for this case. The LDL-apheresis, which utilizes separative membrance or selective adsorbens to remove LDL in vitro, can quickly lower the level of LDL to a safe and normal level, while the materials for LDL-apheresis is the key for the therapy. Currently, The most excellent technique of LDL-apheresis is the"HELP"which were developed by German, whose principle is based on the fact that Heparin, LDL and fibrinogen can form Hep-fib-LDL praecipitatum under PH=5.12, thus the aim to lower the LDL level can be achieved by filting the LDL-fib-Hep praecipitatum away. Unfortunately, there exists a potential unsafe side effect that the some subjects maybe prone to hemorrhagic hazard due to the excessive dose of Heparin. In this study, we tried to design and prepare a new, efficient and practical LDL-selective adsorbens, with an aim to keep the advantages of"HELP"technique and avoid its shortcome mentioned above, as well as has a feature of relatively easy to prepare and low cost.In this study, the principle of preparing the LDL-selective adsorbens is that the electronegative Heparin molecule can specifically bind to the electropositive LDL molecule by the electrostatic interaction, thus by solid-liquid phase and two-step synthetic technique the LDL-selective adsorbens was prepared by covalently immobilizing Heparin onto the surface of the support (PVA-1799) with the aid of bifunctional group linking agent.In this study, we investigated the effect of immobilization parameters (the ratio of reactants, the reaction time, the dose of castalyst, and so on) upon the immobilization amount of the ligand. By analyzing the its property, the ligand Heparin has been successfully and covalently immobilized onto the surface of the support PVA; over 18μg ligang Heparin could be immobilized onto 1 g of PVA-1799 granules; the adsorbens had a higher adsorptive efficiency for LDL under weak alk enviroment (PH7.2~9.5); under the ratio of 1 portion of the adsorbens to 4 portion of blent plasma ( 2 portion of plasma + 2 portion of diluent), the adsorptive effeciancy was about 60%, which suggested the adsorbens was efficient and the expected aim was achieved; the adsorbens has also affected other blood constituents, but the effects could be clinically accepted or neglectable.In this study, the safety and hemocompatibility of the adsorbens was evaluated according to the Governmental Standard of biological evaluation for medical apparatus and instrument. We have done the cell toxicity test, acute general toxicity test, vivo sensitivity test, pyrogenic test, endotoxin test, hemolysis test, thrombotest, platelet adherence test, blood conventional analysis, complement analysis, enzymology test, inorganic ion test and preliminary animal experiment, all the test results preliminarily suggested that the adsorbens was safe for clinical use.In this study, we also assayed the amount of hydroxy group on the surface of PVA solid film, the result showed the amount was about 10-7mol/cm2, it could be, therefore, inferred that the efficiency of surface modification is essentially very low.In this study, we made a contrast among different preparation technologies; the results showed different preparation technology had different effect on the spacial degree of freedom of the immobilized ligand Heparin, finding the higher the spacial degree of freedom of the immobilized Heparin the higher its adsorptive efficiency for LDL.To draw a conclusion, the LDL-selective adsorbens prepared in this study had a higher adsorptive effieciency for LDL, about 60%, under the given conditions; the results of preliminary safety assessments suggested the adsorbens was safe for clinical use; additionally, the feature of preparation technology was relateively easy to prepare and low in cost. All those results showed our expected goals were successfully achieved.