Passive and active hepatoma tumor targeting of new N-(2-hydroxypropyl)methacrylamide copolymer conjugates: synthesis, characterization, and evaluation in vitro and in vivo.

Human hepatocellular carcinoma (HCC) is one of the major causes of death worldwide. To investigate the relative importance of active and passive targeting strategies, the synthesis, characterization, in vitro uptake, and in vivo biodistribution of specific sulfapyridine HPMA (HPMA: N-(2-hydroxypropyl methacrylamide)) copolymer (sulfapyridine: SPD) conjugates, nonspecific HPMA copolymer conjugates, and DTPA are described in this study. The poly(HPMA)-SPD-DTPA (DTPA: diethylenetriaminepentaacetic acid), poly(HPMA)-DTPA, and DTPA conjugates were radiolabeled with the radionuclide Tc-99m and tested for uptake by cultured H22 cells. The cellular accumulation of poly(HPMA)-SPD-DTPA-Tc-99m complex was found to be time-dependent. The poly(HPMA)-SPD-DTPA-Tc-99m tracer exhibited rapid uptake kinetics in cell culture with a t(1/2) of approximate to 5min. The uptake of poly(HPMA)-SPD-DTPA-Tc-99m was significantly higher than that of poly(HPMA)-DTPA-Tc-99m, indicating that the uptake of the poly(HPMA)-SPD-DTPA-T-99m was active binding. The uptake of poly(HPMA)-DTPA-Tc-99m was significantly higher than that of DTPA-Tc-99m, suggesting that the uptake of the poly(HPMA)-DTPA-T-99m was passive binding. Twenty-four hour necropsy data in the hepatocellular carcinoma tumor model showed significantly higher (p<0.001) tumor localization for poly(HPMA)-SPD-DTPA-Tc-99m (4.98 +/- 0.48%ID/g [percentage injected dose per gram tissue]) compared with poly(HPMA)-DTPA-Tc-99m (2.69 +/- 0.15% ID/g) and DTPA-Tc-99m (0.83 +/- 0.03%ID/g). Moreover, higher T/B for poly(HPMA)-SPD-DTPA-Tc-99m indicated reduced extravazation of the targeted polymeric conjugates in normal tissues. Specific molecular targeting and nonspecific vascular permeability are both significant in the relative tumor localization of poly(HPMA)-SPD-DTPA-Tc-99m. Extravascular leak in nonspecific organs appears to be a major factor in reducing the T/B for the sulfapyridine molecules. Thus, the poly(HPMA)-SPD-DTPA is expected to be used as the potential macromolecular targeting carrier for hepatoma carcinoma in mice.