Distribution of free and liposome-encapsulated cefoxitin in experimental intra-abdominal sepsis in rats

Effect of Liposomal Doxorubicin in Pressurized Intra-Peritoneal Aerosol Chemotherapy (PIPAC)

Background: This ex-vivo study was performed to compare the impact of doxorubicin vs. liposomal doxorubicin on penetration depth in peritoneal tissue during Pressurized Intra-Peritoneal Aerosol Chemotherapy (PIPAC) via microcatheter (MC). Methods: Fresh post mortem swine peritoneum was cut into proportional sections. One group of samples was treated with PIPAC with Doxorubicin (D), and the other was treated with PIPAC with liposomal doxorubicin (LD). Tissue specimens were placed as follows: at the bottom of the plastic box (1), at the side wall (2), at the top cover (3) and the side of the box covered by a plastic tunnel (4). In-tissue doxorubicin penetration was measured using fluorescence microscopy on frozen thin sections. Results: Medium penetration levels with D were 325 µm (1), 152 µm (2), 84 µm (3) and 71 µm (4), respectively. Medium penetration levels with LD were significantly lower with 10 µm (1), 2 µm (2), 0 µm (3) and 0 µm (4), respectively. In most samples that were treated with LD no doxorubicin could be detected at all. Conclusion: Our data indicate that liposomal coating of doxorubicin and possibly other chemotherapeutical drugs might inhibit their interaction with the peritoneal surface. This inhibition appears to be relatively strong, since doxorubicin is partially undetectable due to liposomal coating. Further studies are warranted to investigate this interaction and its potential benefit in peritoneal applications.

Biodegradable nanoparticles for intracellular delivery of antimicrobial agents

Biodegradable nanoparticles have emerged as a promising strategy for ferrying antimicrobial agents into specific cells due to their unique properties. This review discusses the current progress and challenges of biodegradable nanoparticles for intracellular antimicrobial delivery to understand design principles for the development of ideal nanocarriers. The intracellular delivery performances of biodegradable nanoparticles for diverse antimicrobial agents are first summarized. Second, the cellular internalization and intracellular trafficking, degradation and release kinetics of nanoparticles as well as their relation with intracellular delivery of encapsulated antimicrobial agents are provided. Third, the influences of nanoparticle properties on the cellular internalization and intracellular fate of nanoparticles and their payload antimicrobial agents are discussed. Finally, the challenges and perspectives of nanoparticles for intracellular delivery of antimicrobial agents are addressed. The review will be helpful to the scientists who are interested in searching for more efficient nanosystem strategies for intracellular delivery of antimicrobial agents.

The characterization and biodistribution of cefoxitin-loaded liposomes

To conquer the clinical restriction of relative short half-life and poor tissue retaining activities, liposomes containing cefoxitin were prepared using three methods in this study. The physicochemical properties including cefoxitin encapsulation percentage, vesicle size, stability, as well as the in vivo biodistribution were studied. The highest entrapment percentage was observed by using reverse phase evaporation method, and the molar ratio of cefoxitin to phospholipids was 1:3, DMPC to cholesterol was 2:1, respectively. From the result of stability, the freeze-drying powder and then stored in the frozen condition of cefoxitin-loaded liposome was an ideal storage state. Accordingly, the formulation by reverse-phase evaporation method was selected to investigate the biodistribution of cefoxitin-loaded liposome and compared to free cefoxitin in rats. It was observed that the cefoxitin levels and the duration retained in the liver, spleen, and pancreas of liposome-injected animals were higher and longer than that of free cefoxitin-injected animals. The drug concentrations of bile after post-injection of liposomal cefoxitin at 0.5, 1 and 2 h were all approximately 2.7 times higher than that of free cefoxitin injection group.

Liposomal entrapment of cefoxitin to improve cellular viability and function in human saphenous veins

Liposomal cefoxitin was prepared and applied to the pretreatment of human saphenous vein (HSV) for implantation. The possible use of liposomal cefoxitin to improve cellular viability and function and to maintain its potential sterilization effect was investigated. Entrapment efficiency and size distribution of liposomal cefoxitin were 75.7% and 652 +/- 75.7 nm, respectively. The weight ratio between cefoxitin and liposome was calculated at 1 : 40.6. When cefoxitin was entrapped with liposome, the released amount of cefoxitin was not affected by temperature conditions (37 degrees C, 25 degrees C, and 4 degrees C). The amount of free cefoxitin present in HSV reached 59% at 0.5 h and gradually decreased with time, while liposomal cefoxitin showed a maximum amount (63%) at 1.5 h, indicating that liposomal cefoxitin seemed to control the initial amount of cefoxitin present in HSV. Liposomal cefoxitin showed better viabilities of whole cells and endothelial cells dissociated from HSV than free cefoxitin and remarkably superior function of endothelial cells, as determined by Griffonia simplicifolia agglutinins-fluorescein isothiocyanate/propidium iodide double-staining methods combined with flow cytometry and endothelial nitric oxide synthase assay, respectively. In terms of sterilization effect, there was no significant difference between liposomal cefoxitin and free cefoxitin. These results suggest that liposomal entrapment of cefoxitin could improve cellular viability and functions and maintain the original sterilization effect.

A novel approach for the increased delivery of pharmaceutical agents to peritoneum and associated lymph nodes

A novel method for prolonging the retention of liposomes in the peritoneum while increasing liposome deposition in lymph nodes that drain the peritoneum is described. An aliquot (1 ml) of technetium-99m ((99m)Tc)-biotin-liposomes encapsulating blue dye was injected intraperitoneally in rats. Thirty minutes after administration of the (99m)Tc-blue-biotin-liposomes, five rats (experimental) were administered avidin (5 mg) intraperitoneally, whereas the remaining five rats served as controls. Scintigraphic images were acquired at baseline and 1 and 24 h after the liposome injection followed by a tissue biodistribution study. Images at 24 h clearly demonstrated very different distributions between the experimental and control animals. In experimental rats, most of the activity was visualized in the abdominal region, and in abdominal and mediastinal lymph nodes. The percentage of the injected dose (% ID) in the blood was significantly higher in the control group than in the experimental group (14.0 +/- 1.7 versus 0.17 +/- 0.03%; P < 0.001). The % ID in the spleen was also significantly greater for controls (23.3 +/- 3.9%) compared with the experimental group (0.78 +/- 0.8%; P = 0.001). Significant (99m)Tc activity was detected in blue-stained abdominal nodes (4.7%) and mediastinal nodes (2.3%) from the experimental animals, whereas no blue-stained nodes were detectable in the control animals. The intraperitoneal biotin-liposome/avidin delivery system described in this study could potentially be used for delivery of liposome-encapsulated drugs to disease processes that become disseminated in the peritoneum such as metastatic ovarian, gastric, and colorectal cancer, as well as infectious peritonitis.

Peritoneal cytokine concentrations and survival outcome in an experimental bacterial infusion model of peritonitis

OBJECTIVE

To correlate the dynamics of peritoneal cytokines with systemic concentrations and survival outcome.

DESIGN

Randomized, controlled study using a recently developed rat model of peritonitis.

SETTING

Government research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Infected animals (INF) received an intraperitoneal infusion of 6.5 x 10(8) colony-forming units of Escherichia coli over 12 hrs, whereas control rats (CON) received a sterile inoculum. Peritoneal fluid and plasma samples were obtained from all rats at the end of the 12-hr infusion period as well as from all animals that survived the 7-day study (SURV).

MEASUREMENTS AND MAIN RESULTS

Interleukin (IL)-1beta concentration in the peritoneal fluid at 12 hrs tended to be higher in nonsurvivors (NONSURV) than in SURV. Tumor necrosis factor-alpha and IL-6 peritoneal concentrations at 12 hrs were significantly greater in NONSURV than in SURV. There were no significant differences in IL-2 and IL-4 peritoneal concentrations at 12 hrs between SURV and NONSURV. Although the concentrations of IL-1beta and tumor necrosis factor-alpha in the peritoneal fluid of INF decreased gradually during the study, these concentrations remained significantly higher than those of CON at 7 days. In contrast, peritoneal IL-2 concentrations remained lower in INF than in CON for most of the experiment. Peritoneal IL-6 concentrations in INF were transiently elevated above those of CON for 12 hrs. Cytokine concentrations in the peritoneal fluid of INF were always higher than those in plasma, which remained relatively unchanged throughout the study. For most of the variables as. sessed, CON showed no significant changes compared with INF.

CONCLUSIONS

This model of peritonitis is associated with a significant and prolonged peritoneal inflammatory response that is adversely correlated with survival outcome. Our data would suggest that to be effective, novel immunotherapies should target mainly the peritoneal compartment.

Efficacy of liposomal antibiotic therapy in a rat infusion model of Escherichia coli peritonitis

OBJECTIVE

To compare the potential therapeutic effect of liposomal vs. free cefoxitin.

DESIGN

Randomized, controlled study, using a rat model of peritonitis.

SETTING

Government research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Rats were infused intraperitoneally with 6.5 x 10(8) colony forming units of Escherichia coli over 12 hrs. Animals were then randomized to receive intravenous saline, free cefoxitin, liposomal cefoxitin, or plain liposomes twice daily until they were killed.

MEASUREMENTS AND MAIN RESULTS

Free cefoxitin significantly reduced the number of E. coli after 24 hrs compared with saline treatment in both liver and spleen. However, liposomal cefoxitin further decreased the bacterial content by five-fold to ten-fold in these organs. Minimal bactericidal effect was observed in animals injected with plain liposomes. Although administration of liposomal cefoxitin for 7 days further reduced bacterial counts in liver and spleen, there was no apparent beneficial bactericidal effect of free cefoxitin over saline at 7 days. There was approximately a ten-fold reduction in bacterial content in the lungs after 24 hrs in all three treatments, but no further reduction was observed after 7 days. There was no difference in 7-day survival rate in animals treated with plain liposomes or saline (45% vs. 39%). Although survival tended to increase with free cefoxitin treatment (64%), this outcome was significantly improved with the use of liposomal cefoxitin (82%).

CONCLUSIONS

Liposomal cefoxitin enhanced bacterial killing in liver and spleen in this model of E. coli peritonitis. It also improved survival outcome relative to no treatment but not compared with free cefoxitin.

Distribution of free and liposomal cefoxitin in plasma and peritoneal fluid in a porcine intra-abdominal sepsis model

The plasma and peritoneal fluid pharmacokinetic parameters obtained after the intravenous administration of free and liposomal cefoxitin were studied in a porcine model of intraabdominal sepsis. No prior assumptions were made to predict the number of compartments pertaining to drug clearance from the administration of either cefoxitin formulation. The experimental data obtained were applied to fit mathematical models of multiexponential drug clearance and the pharmacokinetic data were found to best fit a two-compartment open model. Liposomal encapsulation significantly altered the plasma drug distribution pattern resulting in changes in the magnitude of a number of pharmacokinetic parameters examined. The mean post-distributive half-life of liposomal cefoxitin was substantially longer than that of free cefoxitin by at least 3 times. The peritoneal cavity appeared to provide a reservoir for the initial distributive phase of rapid drug clearance from the plasma compartment followed by a less-rapid post-distributive phase. The cumulative drug level, as determined by the area under the concentration curve (AUC) as a function of time, in the plasma of animals treated with liposomal cefoxitin was about 3-4 fold as high as that of animals treated with free cefoxitin. The differences in pharmacokinetic parameters appeared to account for the improved therapeutic efficacy of liposomal cefoxitin in this animal model.

Antibacterial efficacy against an in vivo Salmonella typhimurium infection model and pharmacokinetics of a liposomal ciprofloxacin formulation

The fluoroquinolone antibiotic ciprofloxacin has been encapsulated into large unilamellar vesicles (LUV) at efficiencies approaching 100%. Drug accumulation proceeded in response to a transmembrane gradient of methylammonium sulfate and occurred concomitantly with the efflux of methylamine. A mechanism for the encapsulation process is described. LUV composed of dipalmitoylphosphatidylcholine-cholesterol (DPPC/chol), distearoylphosphatidylcholine-cholesterol (DSPC/chol), or sphingomyelin-cholesterol (SM/chol) increased the circulation lifetime of ciprofloxacin after intravenous (i.v.) administration by > 15-fold. The retention of ciprofloxacin in liposomes in the circulation decreased in the sequence SM/chol > DSPC/chol > DPPC/chol. Increased circulation lifetimes were associated with enhanced delivery of the drug to the livers, spleens, kidneys, and lungs of mice. Encapsulation of ciprofloxacin also conferred significant increases in the longevity of the drug in the plasma after intraperitoneal administration and in the lungs after intratracheal administration in comparison to free ciprofloxacin. The efficacy of a single i.v. administration of an SM/chol formulation of ciprofloxacin was measured in a Salmonella typhimurium infection model. At 20 mg of ciprofloxacin per kg of body weight, the encapsulated formulation resulted in 10(3)- to 10(4)-fold fewer viable bacteria in the livers and spleens of infected mice than was observed for animals treated with free ciprofloxacin. These results show the utility of liposomal encapsulation of ciprofloxacin in improving the pharmacokinetics, biodistribution, and antibacterial efficacy of the antibiotic. In addition, these formulations are well suited for i.v., intraperitoneal, and intratracheal or aerosol administration.

Drug distribution and a pulmonary adverse effect of intraperitoneally administered doxorubicin niosomes in the mouse

Niosomes (non-ionic surfactant vesicles) prepared from C16G2 (a hexadecyl-diglycerol ether), and loaded with doxorubicin, were administered intraperitoneally to male AKR mice at dose levels of 0, 2.5, 5.0, and 10.0 mg kg-1. Free drug was given at 10.0 mg kg-1 by the intraperitoneal route. At a dose level of 10.0 mg kg-1, peak doxorubicin levels in the central compartment were attained faster with the free drug than with the niosome formulation. However, the peak plasma levels were similar for the free drug and the niosome preparation at the 10 mg kg-1 dose level. With doxorubicin administered as the niosome preparation by the intraperitoneal route at 2.5, 5.0, and 10.0 mg kg-1, mean peak plasma concentrations of the drug showed a tendency to be dose-related although the differences were not significant. Over the 24 h period of the experiment, with doxorubicin at 10 mg kg-1, the niosome formulation delivered significantly more drug to the plasma compartment than the free drug (p < 0.05). When doxorubicin was given in niosomes at 2.5, 5.0 and 10.0 mg kg-1 by the intraperitoneal route, the resulting levels of doxorubicin in cardiac tissue were not dose related and the differences not significant and, although the mean peak cardiac-tissue concentration was higher in animals receiving the free drug at 10.0 mg kg-1 intraperitoneally than in mice given intraperitoneal doxorubicin niosomes at this dose level, the differences were again not significant. There were clinical signs of toxicity in mice given doxorubicin-containing niosomes intraperitoneally at 5.0 and 10.0 mg kg-1, and at post-mortem an accumulation of fluid in the pleural cavity was evident. These changes were not seen in mice dosed intraperitoneally with free drug at 10 mg kg-1, or in animals given doxorubicin niosomes intraperitoneally at 2.5 mg kg-1. In mice dosed intraperitoneally with doxorubicin niosomes at 12.0 mg kg-1 and at a dose volume of 0.2-0.4 mL, histological examination of the lungs demonstrated a congestion of the alveolar capillaries, and an increased number of acute inflammatory cells in the alveolar walls. There was no histological evidence of lung toxicity in mice dosed with doxorubicin niosomes at 12.0 mg kg-1 when the formulation was administered with the higher dose volume of 1.8-2.0 mL. Importantly there was no histological evidence of lung toxicity in mice dosed with empty niosomes intraperitoneally or with doxorubicin niosomes given intravenously at 12.0 mg kg-1.