Christien Oussoren

Lymphatic uptake and biodistribution of liposomes after subcutaneous injection.: II. Influence of liposomal size, lipid composition and lipid dose

The present paper reports on the results of a systematic study on liposome variables potentially affecting lymphatic disposition and biodistribution of liposomes after sc injection. Liposomal size was found to be the most important factor influencing lymphatic uptake and lymph node localization of sc administered liposomes. Lymphatic uptake from the s.c. injection site of small liposomes (about 0.04 microm) was relatively high (76% of the injected dose (%ID)) as compared to large, non-sized liposomes, which remained almost completely at the site of injection. Small liposomes were less efficiently retained by regional lymph nodes than larger liposomes. Liposomal lipid composition did not influence lymphatic uptake with one exception: Lymphatic uptake was decreased in case of neutral liposomes composed of (DPPC). Lymph node localization was substantially enhanced by inclusion of phosphatidylserine (PS) into the liposomal bilayers. Saturation of lymphatic uptake and lymph node localization did not occur over a large liposomal lipid dose range, illustrating the efficient performance of lymph nodes in capturing s.c. administered particles.

Liposomes to target the lymphatics by subcutaneous administration

Liposomes have been proposed as carriers for the delivery of therapeutic and diagnostic agents to the lymphatic system. Subcutaneous (s.c.) injection is the route of administration most extensively studied for this purpose. Decisive factors influencing lymphatic absorption and lymph node uptake of s.c. administered liposomes are liposome size and the anatomical site of injection. Generally, other factors such as lipid composition, charge and the presence of a hydrophilic PEG-coating on the liposome surface do not substantially affect lymphatic absorption and lymph node uptake of s.c. administered liposomes. Studies on the intranodal fate of liposomes demonstrate that phagocytosis by macrophages is the most important mechanism for lymph node uptake of liposomes. The observation of relatively high uptake of liposomes in regional lymph nodes after s.c. administration has stimulated research on lymphatic targeting of liposomes for diagnostic and therapeutic applications.

Steric stabilization of poly(2-(dimethylamino)ethyl methacrylate)-based polyplexes mediates prolonged circulation and tumor targeting in mice

Efficient tumor targeting of polymeric gene transfer systems (polyplexes) represents a major challenge. To establish tumor targeting after intravenous (IV) administration, the circulation lifetime of these systems should be sufficiently long. Since naked polyplexes are rapidly eliminated from the circulation after IV adminstration, strategies have to be developed to improve their pharmacokinetics.

Lymphatic uptake and biodistribution of liposomes after subcutaneous injection: III. Influence of surface modification with poly(ethyleneglycol).

AbstractPurpose. The aim of the present paper was to assess the effect of inclusion of distearoylphosphatidylethanolamine-poly(ethyleneglycol) (DSPE-PEG) into liposomal bilayers on the lymphatic uptake and lymph node localization of liposomes after subcutaneous administration. Methods. [3H]-Cholesteryloleylether labeled liposomes of various composition and sizes were injected s.c. into the dorsal side of the foot of rats. At several time-points after injection, blood levels of liposomes were determined. Lymphatic uptake from the s.c. site of injection and lymph node localization in regional lymph nodes were determined at the end of the 52 h observation period. Results. The results demonstrate that inclusion of DSPE-PEG into several types of liposomes has only a modest effect on lymphatic uptake. Also lymph node localization is only slightly affected by PEG-mediated steric stabilization. Conclusions. Factors other than the presence of a steric barrier are more important in determining lymphatic uptake from the s.c. injection site. The observation that lymph node localization was only slightly affected by PEG-coating strongly suggests that macrophage uptake is not the only important mechanism of lymph node localization of s.c. administered liposomes.

Release and absorption rates of intramuscularly and subcutaneously injected pharmaceuticals (II)

Abstract The rate and extent of intramuscular (i.m.) and subcutaneous (s.c.) drug absorption are very erratic and variable. The lipophilicity of the compound plays an important role. Aqueous drug solutions and suspensions of the more lipophilic compounds are often absorbed incompletely within the therapeutically relevant time. More hydrophilic compounds are absorbed completely. Injection depth, drug concentration and vehicle volume, pH-p K a relation, vehicle, cosolvents and surfactants have strong influences on the absorption profile of lipophilic drugs. Aqueous solutions of hydrophilic drugs are less sensitive to these factors. Drug solutions in oil and even suspensions in oil are often thought to be sustained release preparations. In fact, rapid absorption has often been observed. Slow release is not a property of the oily vehicle but is achieved by a high lipophilicity of the dissolved or suspended compound. Liposomal preparations are currently under investigation as i.m. and s.c. injectable sustained release preparations. Factors that induce drug release at the injection sites are the proteins and especially lipoproteins in the interstitial fluids, originating from serum filtrate and from turnover of inflammatory cells. Phagocytosis by macrophages and fat cells may play an important role in the local clearance of liposomal material from the injection site. Sustained release of some pharmaceuticals with normal or long half-lives appeared in specific cases preferable to rapid release. In addition, high arterial drug concentrations during the absorption phase may result in undesired effects even when venous drug concentrations are within the safe range.

The fate of poly(2-dimethyl amino ethyl)methacrylate-based polyplexes after intravenous administration.

Poly(2-dimethyl amino ethyl) methacrylate (pDMAEMA) cationic polymers have been shown to be efficient vectors for gene delivery in vitro. This contribution deals with the in vivo properties of polyplexes based on this polymer. In mice, pDMAEMA/[32P]-pLuc complexes distributed primarily to the lungs. The gene expression profile matched the biodistribution profile. In vitro turbidity experiments in serum showed severe aggregation upon addition of cationic polyplexes, pointing out the involvement of aggregates in the dominant lung uptake of the positively charged polyplexes. Incubations of polyplexes with albumin yielded a decline of the zeta potential of the complexes to negative values, making an electrostatic mechanism in the dominant lung uptake less likely. Hemagglutination experiments showed that the polyplexes induce the formation of extremely large structures when incubated with washed erythrocytes. Altogether, the present data indicate that aggregate formation and trapping of the formed aggregates in the lung capillary bed is probably responsible for the dominant lung uptake and transfection. Poly(ethylene)glycol (PEG) of the polymeric structures prevented the increase in the observed turbidity in serum seen with polyplexes and was also able to reduce interactions with erythrocytes. Currently, the in vivo fate of the PEGylated polyplexes is under investigation.

Lymphatic uptake and biodistribution of liposomes after subcutaneous injection - IV. Fate of liposomes in regional lymph nodes

The ability of clodronate-containing liposomes to deplete lymph nodes of macrophages was used as a tool to investigate the fate of liposomes in regional lymph nodes after subcutaneous (s.c.) administration. Reduced lymph node localization of liposomes in macrophage-depleted lymph nodes confirmed that phagocytosis by macrophages plays an important role in lymph node retention of liposomes. Depletion of macrophages had less effect on lymph node localization of small liposomes than on the lymph node localization of large liposomes. Inclusion of distearoylphosphatidylethanolamine (DSPE)-poly(ethyleneglycol) (PEG-PE) into the liposomes, which is known to oppose macrophage uptake, did not affect lymph node localization in macrophage-depleted or control lymph nodes. We conclude that PEG-liposomes retained by lymph nodes are also taken up by lymph node macrophages. Morphological observations visualizing the uptake of PEG-liposomes by lymph node macrophages support this conclusion.

Effect of Liposome Characteristics and Dose on the Pharmacokinetics of Liposomes Coated with Poly(amino acid)s

Long-circulating liposomes, such as PEG-liposomes, are frequently studied for drug delivery and diagnostic purposes. In our group, poly(amino acid) (PAA)-based coatings for long-circulating liposomes have been developed. These coatings provide liposomes with similar circulation times as compared to PEG-liposomes, but have the advantage of being enzymatically degradable. For PEG-liposomes it has been reported that circulation times are relatively independent of their physicochemical characteristics. In this study, the influence of factors such as PAA grafting density, cholesterol inclusion, surface charge, particle size, and lipid dose on the circulation kinetics of PAA-liposomes was evaluated after intravenous administration in rats. Prolonged circulation kinetics of PAA-liposomes can be maintained upon variation of liposome characteristics and the lipid dose given. However, the use of relatively high amounts of strongly charge-inducing lipids and a too large mean size is to be avoided. In conclusion, PAA-liposomes represent a versatile drug carrier system for a wide variety of applications.

Lymphatic Uptake and Biodistribution of Liposomes after Subcutaneous Injection I. Influence of the Anatomical Site of Injection

AbstractLiposomes have been proposed as carriers for the delivery of therapeutic and diagnostic agents to the lymphatic system. Subcutaneous (s.c.) injection is the route of administration most extensively studied for this purpose. To establish the influence of the anatomical site of s.c. injection on lymphatic uptake of liposomes, we have examined the pharmacokinetics and biodistribution of small (0.10 μm) [3H]-labeled liposomes administered at three different s.c. sites of the rat. Lymphatic uptake of liposomes from the s.c. site of injection, lymph node localization and biodistribution in liver, spleen and kidneys were highly dependent on the site of injection. s.c. injection into the dorsal side of the foot or in the footpad resulted in relatively high uptake of liposomes from the site of injection as compared to uptake from the s.c. injection site at the flank. Moreover, injection into the dorsal side of the foot or in the footpad resulted in relatively high levels of radioactivity in regional lymph ...

Effect of Repeated Intravenous Administration on the Circulation Kinetics of Poly(Ethyleneglycol)-Liposomes in Rats

AbstractThe use of sterically stabilized poly(ethyleneglycol)-coated liposomes (PEG-liposomes) is becoming increasingly important and several preparations based on long-circulating liposomes are already commercially available. From a clinical point of view, it is of importance to study the effect of multiple i.v. administration of PEG-liposomes on their pharmacokinetic behavior. Sterically stabilized liposomes were obtained by incorporation of PEG conjugated to distearoylethanolamine (DSPE) into the liposomal bilayers. Rats received 4 i.v. injections of small (0.12 um) PEG-liposomes at 24 or 48 h dosing intervals. Blood levels of liposomal label were determined at several time-points after injection. Our findings demonstrate that, under the chosen conditions, i.v. injection of PEG-liposomes has no effect on the blood circulation kinetics of subsequent doses of similar liposomes given at 24 or 48 h dosing intervals. These findings suggest that PEG-liposomes are suitable as drug carriers for diagnostic and ...