Quantitative determination of C3 fragments on the liposomal surface with anti-human C3 monoclonal antibodies.

Quantitative determination of human complement component 3 (C3) fragments on the liposomal surface is considered to give useful informations for speculation of the biological fate of liposomes. The determination method of C3 fragments on the liposomal surface with anti-human C3 monoclonal antibodies (MoAbs) is presented in this paper. Twelve MoAbs(KOCO2831∼2812) were prepared and two-site sandwich enzyme-linked immunospecific assay(Sandwich-ELISA) system was developed. It became apparent all antibodies obtained in this study recognize β-chain of C3 structure. KOCO2801 and biotinylated KOCO2804 gave an optimal combination for the ELISA system. C3 fragments bound to surface of cetyimannoside-modified liposome (Man-MLV) and non-modified liosomes (PC-MLV) were determined after incubation with fresh human plasma. After separation of liposomes from the plasma by centrifugation, lipids were removed by extraction with 1, 1, 2-Trichloro-1, 2, 2-trifluoroethane, and then C3 fragments were determined in the ELISA system. The results showed that C3 bound on the Man-MLV are more larger quantities than those of PC-MLV, This result confirmed that the ammount of C3 bound on liposomal surface correlates with the instability of the liposomes in the circulation and the enhancing hepatic uptake of the liposomes. Thus, this approach can be available for investigation of liposomal behaviour in the circulation.