The in vivo fate of drugs conjugated to macromolecules inevitably depends on that of macromolecules. However, the in vivo fate of macromolecules also may be altered by conjugation to drugs. For the ...efficient design of carboxymethyldextran (CMD) conjugates of a new analgesic drug, DA5018, we investigated whether the chemical modifications alter the pharmacokinetics and tissue distribution of CMD itself. 14 CCMD, oxidized 14 CCMD (14 COCMD), 14 COCMD conjugates of DA5018 (14 COCMD-DA5018) and 14 COCMD conjugates of ethanolamine (14 COCMD-EA) were prepared and their molecular sizes were compared by size exclusion HPLC. The pharmacokinetics, biliary excretion, and tissue distribution of total radioactivity were compared after intravenous administration of each CMD derivative, 2.0 MBq/kg, to rats. The effective molecular sizes of CMD derivatives decreased in the order of 14 CCMD, 14 COCMD-DA5018, 14 COCMD, and 14 COCMD-EA. After administration of each derivative, the mean AUC values of total radioactivity decreased with the decrease in the effective molecular size. The values of CL, Vss, and the amount of total radioactivity excreted in 24-hr urine increased considerably with the decrease in the effective molecular size. The tissue-to-plasma ratios of total radioactivity remaining in heart, liver, lung, kidney, and spleen at 24 hr also increased in the opposite order of the effective molecular size. Taken together, all these results demonstrate that the chemical modifications and physicochemical properties of attached chemicals can alter the pharmacokinetics and tissue distribution of CMD. One possible reason might be the difference in the effective molecular size of various CMD derivatives. Our study demonstrates that it may be necessary to consider the effect of chemical modification on the in vivo fate of macromolecules in designing macromolecular drug conjugates.
Transferrin receptor (TFR) levels in proliferating malignant cells have often been found to be far higher than in the corresponding normal cells. Cisplatin(cis-diamminedichloroplatinum (II) : CDDP) ...was complexed via an intermediate carboxymethyl dextran (CMD) to transferrin (TF) which recognizes TFR on the cell surface. CMD was first conjugated to TF by a modified water-soluble carbodiimide method in which N-hydroxysuccinimide was used to enhance the coupling reaction. Conjugates of TF and CMD of differing molar ratios (TF/CMD 1 : 0.4, 1 : 1.4 and 1 : 1.6) were prepared by this method. Spectrophotometric titration of the conjugates with Fe3+ showed that the ferric ion binding activity of apo-TF-CMD was reduced as the molar ratio of CMD to TF increased. CDDP was complexed to the TF-CMD resulting in complexes (TF-CMD-CDDP) carrying up to 8 w/w % of the drug which was reversibly released from the carrier conjugate. Diferric-TF-CMD-CDDP consisted of 0.4 mol of CMD per 1 mol of TF and 3.6 w/w % of CDDP retained cytotoxic activity against human leukemia cell lines, HL60 and K562. The LD50 values of the diferric-TF-CMD-CDDP and CMD-CDDP were 21.0 μM and 29.5 μM in HL60, and were 40.0 μM and 62.0 μM in K562, respectively, suggesting that the specific complex showed preferential cytotoxicity for the tumor cells in comparison to the nonspecific CMD-CDDP.
Le présent travail est destiné à acquérir un ensemble de données expérimentales et quantitatives cohérentes sur le comportement physico-chimique d'un système constitué d'un polysaccharide linéaire, ...flexible et chimiquement fonctionnalisé en groupements carboxyliques, le carboxyméthyl-dextrane (CMD) et d'un milieu ionique comportant des cations d'affinité variée pour ces fonctions : Na+, Ca2+ et Cd2+. La densité de sites et leur constante de dissociation - complexation ont été déterminées par titrage potentiométrique avec des électrodes spécifiques (proton et cadmium). Les propriétés électro-hydrodynamiques et les transitions conformationnelles ont été étudiées en combinant la conductimétrie, l'électrophorèse, la diffusion dynamique de lumière et la viscosimétrie. Enfin, la stabilité colloïdale en relation avec les interactions intermoléculaires a été étudiée par turbidimétrie et diffusion dynamique de lumière. En présence d'ions monovalents, le comportement du CMD, typique d’une particule microgel molle, est déterminé par la force ionique et la concentration en polysaccharide. A basse force ionique, le CMD est en condition de bon solvant lorsqu'il est peu concentré tandis que le recouvrement des doubles-couches électriques autour des macromolécules détermine les propriétés électro-hydrodynamiques du CMD en régime concentré. A haute salinité, les interactions électrostatiques intramoléculaires et interparticulaires sont négligeables, et la macromolécule a un comportement caractéristique de polymère en mauvais solvant à haute fraction volumique. En présence de cations divalents, le calcium, et plus encore le cadmium, entrent en compétition avec le proton pour l’occupation des sites carboxyliques, ce qui s’accompagne par une réorganisation locale des chaînes polymères. A haute force ionique, la taille élevée des agrégats, la vitesse initiale d'agrégation élevée, ainsi que la persistance d'une forte turbidité au maximum d'effet, suggèrent que les agrégats sont formés en régime de type agrégation limitée par la diffusion des particules (DLA)
The present work focused on the acquisition of experimental and quantitative data on the physico-chemical properties of a linear, flexible and chemically functionalized polysaccharide by carboxymethyl grafting, yielding carboxymethyldextran macromolecules (CMD) and an aqueous electrolyte containing various ions Na+, Ca2+ et Cd2+ with different chemical affinity for these chemical functions. Charge density and complexation – dissociation constants have been evaluated using specific electrodes-based potentiometric titration. The electro-hydrodynamic properties and the conformational transitions were examined through electrical conductivity increment measurements, electrophoresis, dynamic light scattering and viscosimetry. Also, colloidal stability has been investigated by means of turbidimetry and dynamic light scattering. In the presence of monovalent ions, the behaviour of CMD, typically that of a soft microgel particle, is strongly depending on ionic strength and polysaccharide content. For low ionic strengths and in dilute regime, CMD is in situation of good solvent while in concentrated regime, overlapping double layers that develop around macromolecules governs the electro-hydrodynamic features of CMD. For sufficiently high ionic strengths, intermolecular and intramolecular electrostatic interactions are nearly suppressed, and CMD behaves as a polymer in bad solvent upon increase of its concentration in the medium. In the presence of divalent ions, calcium ions and cadmium ions are in competition with hydronium ions to occupy the carboxylic sites, and this situation is concomitantly accompanied by local reorganization of polymer chains. The large size of formed clusters, the high initial aggregation rate and the increased turbidity all suggest that aggregates are generated according to a diffusion limited aggregation (DLA) type of mechanism
PDF
