Low density lipoprotein adsorption on sol-gel derived alumina for blood purification therapy

Among the clinical treatments of Familial Hyper cholesterolemia patients to reduce the concentration of low density lipoprotein (LDL), blood purification therapy is most suitable in which a blood-compatible adsorbent is employed. In the present study, alumina powders were prepared via a sol-gel route to develop a LDL-adsorbent Aluminum tri2-propoxide was hydrolyzed and subsequently calcined up to 1200°C. Surface charge density and pore size distribution were measured, and the phases were identified. The alumina calcined above 400°C had excellent blood compatibility in terms of endogenous clotting parameters, i.e., partial thromboplastin time: (PTT), prothrombin time: (PT), and the amount of fibrinogen: (Fib). The amount of LDL-adsorption (ΔW_LDL) increased with the calcining temperature, showing a good linear correlation to surface charge density. The 1200°C sample consisted only of α-alumina, and was greatest in ΔW_LDL. All samples involved pores smaller than 20 nm but not the pores large enough to accommodate LDL molecules (20-25 nm). From those results, it was concluded for the present alumina particles that the surface charge density was the primary factor and that the chemical activity of α-alumina also contributed to the excellent LDL-adsorption for the 1200°C sample, while entrapping LDL in the pores was not an active mechanism.