Co-Delivery of Ciprofloxacin and Colistin in Liposomal Formulations with Enhanced <Emphasis Type="BoldItalic">In Vitro</Emphasis> Antimicrobial Activities against Multidrug Resistant <Emphasis Type="BoldItalic">Pseudomonas aeruginosa</Emphasis>

Purpose

This study aims to develop liposomal formulations containing synergistic antibiotics of colistin and ciprofloxacin for the treatment of infections caused by multidrug-resistant Pseudomonas aeruginosa.

Methods

Colistin (Col) and ciprofloxacin (Cip) were co-encapsulated in anionic liposomes by ammonium sulfate gradient. Particle size, encapsulation efficiency, in vitro drug release and in vitro antibiotic activities were evaluated.

Results

The optimized liposomal formulation has uniform sizes of approximately 100 nm, with encapsulation efficiency of 67.0% (for colistin) and 85.2% (for ciprofloxacin). Incorporation of anionic lipid (DMPG) markedly increased encapsulation efficiency of colistin (from 5.4 to 67.0%); however, the encapsulation efficiency of ciprofloxacin was independent of DMPG ratio. Incorporation of colistin significantly accelerated the release of ciprofloxacin from the DMPG anionic liposomes. In vitro release of ciprofloxacin and colistin in the bovine serum for 2 h were above 70 and 50%. The cytotoxicity study using A549 cells showed the liposomal formulation is as non-toxic as the drug solutions. Liposomal formulations of combinations had enhanced in vitro antimicrobial activities against multidrug resistant P. aeruginosa than the monotherapies.

Conclusions

Liposomal formulations of two synergistic antibiotics was promising against multidrug resistant P. aeruginosa infections.

     

In vitro and ex vivo methods predict the enhanced lung residence time of liposomal ciprofloxacin formulations for nebulisation

Liposomal ciprofloxacin formulations have been developed with the aim of enhancing lung residence time, thereby reducing the burden of inhaled antimicrobial therapy which requires multiple daily administration due to rapid absorptive clearance of antibiotics from the lungs. However, there is a lack of a predictive methodology available to assess controlled release inhalation delivery systems and their effect on drug disposition. In this study, three ciprofloxacin formulations were evaluated: a liposomal formulation, a solution formulation and a 1:1 combination of the two (mixture formulation). Different methodologies were utilised to study the release profiles of ciprofloxacin from these formulations: (i) membrane diffusion, (ii) air interface Calu-3 cells and (iii) isolated perfused rat lungs. The data from these models were compared to the performance of the formulations in vivo. The solution formulation provided the highest rate of absorptive transport followed by the mixture formulation, with the liposomal formulation providing substantially slower drug release. The rank order of drug release/transport from the different formulations was consistent across the in vitro andex vivo methods, and this was predictive of the profiles in vivo. The use of complimentary in vitro and ex vivo methodologies provided a robust analysis of formulation behaviour, including mechanistic insights, and predicted in vivo pharmacokinetics.     

Near-Infrared Image-Guided Delivery and Controlled Release Using Optimized Thermosensitive Liposomes

Purpose

To engineer optimized near-infrared (NIR) active thermosensitive liposomes to potentially achieve image-guided delivery of chemotherapeutic agents.

Methods

Thermosensitive liposomes were surface-coated with either polyethylene glycol or dextran. Differential scanning calorimetry and calcein release studies were conducted to optimize liposomal release, and flow cytometry was employed to determine the in vitro macrophage uptake of liposomes. Indocyanine green (ICG) was encapsulated as the NIR dye to evaluate the in vivo biodistribution in tumor-bearing mice.

Results

The optimized thermosensitive liposome formulation consists of DPPC, SoyPC, and cholesterol in the 100:50:30 molar ratio. Liposomes with dextran and polyethylene glycol demonstrated similar thermal release properties; however in vitro macrophage uptake was greater with dextran. Non-invasive in vivo NIR imaging showed tumor accumulation of liposomes with both coatings, and ex vivo NIR imaging correlated well with actual ICG concentrations in various organs of healthy mice.

Conclusions

The optimized thermosensitive liposome formulation demonstrated stability at 37?°C and efficient burst release at 40 and 42?°C. Dextran exhibited potential for application as a surface coating in thermosensitive liposome formulations. In vivo studies suggest that liposomal encapsulation of ICG permits reliable, real-time monitoring of liposome biodistribution through non-invasive NIR imaging.     

In Vitro Cell Integrated Impactor Deposition Methodology for the Study of Aerodynamically Relevant Size Fractions from Commercial Pressurised Metered Dose Inhalers

Purpose

The purpose of this study was to present a modified Andersen cascade impactor (ACI) as a platform to evaluate the deposition and subsequent transport of aerosol micropaticles across airway epithelial cells.

Methods

The impaction plate of an ACI was modified to accommodate up to eight Snapwells. Aerodynamic particle size distribution of the modified ACI was investigated with two commercially available formulations of Ventolin® (salbutamol sulphate) and QVAR® (beclomethasone dipropionate). Deposition and transport of these drug microparticles across sub-bronchial epithelial Calu-3 cells were also studied.

Results

The modified ACI demonstrated reproducible deposition patterns of the commercially available pressurised metered dose inhalers compared to the standard ACI. Furthermore, the Calu-3 cells could be placed in different stages of the modified ACI. No significant effect was observed among the transport rate of different particle sizes deposited on Calu-3 cells within the range of 3.3 to 0.4 μm.

Conclusions

The use of the cell compatible ACI to assess the fate of microparticles after deposition on the respiratory epithelia may allow for better understanding of deposited microparticles in vivo.     

Use of In Vitro�CIn Vivo Correlation to Predict the Pharmacokinetics of Several Products Containing a BCS Class 1 Drug in Extended Release Matrices

Purpose

To determine if an IVIVC model can predict PK profiles of varying formulations of a BCS Class 1 drug that is a salt of a weak base.

Method

An IVIVC model (Level A) was created by correlating deconvoluted in vivo absorption data obtained from oral administration of 50?mg, 100?mg, and 200?mg fast and slow extended release formulations with in vitro percent dissolved using residual regression analysis. The model was then used to predict the in vivo profile of five test products that varied in formulation characteristics.

Results

The model passed internal validation for predicted Cmax and AUC. For external validation, in vitro data of five different test formulations was utilized. The model passed external validation for two test formulations that were different but belonging to the same release mechanism as that of the reference formulation. Three formulations failed external validation because they belonged to either a mixed or different release mechanism. The model and results were further confirmed using GatstroPlus? simulation software.

Conclusions

These observations indicate that an IVIVC model for a BCS class I drug may be applicable to varying formulations if the principle of the drug release is similar.     

Tuning Ciprofloxacin Release Profiles from Liposomally Encapsulated Nanocrystalline Drug

Purpose

In order to attenuate the drug release rate, a single freeze-thaw step was previously shown to convert encapsulated drug into a single nanocrystal within each liposome vesicle. The goal of this study was to alter the nanocrystalline character, and thus the drug encapsulation state and release profile, by addition of surfactant prior to freeze-thaw.

Methods

A liposomal ciprofloxacin (CFI) formulation was modified by the addition of surfactant and frozen. After thawing, these formulations were characterized in terms of drug encapsulation by centrifugation-filtration, liposome structure by cryo-TEM imaging, vesicle size by dynamic light scattering, and in vitro release (IVR) performance.

Results

The addition of increasing levels of polysorbate 20 (0.05 to 0.4%) or Brij 30 (0.05 to 0.3%) to the CFI preparations followed by subsequent freeze-thaw, resulted in a greater proportion of vesicles without drug nanocrystals and reduced the extent of growth of the nanocrystals thus leading to modified release rates including an increase in the ratio of non-encapsulated to sustained release of drug.

Conclusions

This study provides another lever to achieve the desired release rate profile from a liposomal formulation by addition of surfactant and subsequent freeze-thaw, and thus may provide a personalized approach to treating patients.

     

Use of a Fundamental Approach to Spray-Drying Formulation Design to Facilitate the Development of Multi-Component Dry Powder Aerosols for Respiratory Drug Delivery

Purpose

A fundamental approach incorporating current theoretical models into aerosol formulation design potentially reduces experimental work for complex formulations. A D-amino acid mixture containing D-Leucine (D-Leu), D-Methionine, D-Tryptophan, and D-Tyrosine was selected as a model formulation for this approach.

Methods

Formulation design targets were set, with the aim of producing a highly dispersible D-amino acid aerosol. Particle formation theory and a spray dryer process model were applied with boundary conditions to the design targets, resulting in a priori predictions of particle morphology and necessary spray dryer process parameters. Two formulations containing 60% w/w trehalose, 30% w/w D-Leu, and 10% w/w remaining D-amino acids were manufactured.

Results

The design targets were met. The formulations had rugose and hollow particles, caused by deformation of a crystalline D-Leu shell while trehalose remained amorphous, as predicted by particle formation theory. D-Leu acts as a dispersibility enhancer, ensuring that both formulations: 1) delivered over 40% of the loaded dose into the in vitro lung region, and 2) achieved desired values of lung airway surface liquid concentrations based on lung deposition simulations.

Conclusions

Theoretical models were applied to successfully achieve complex formulations with design challenges a priori. No further iterations to the design process were required.     

Brain-specific delivery of rifampin from lactyl stearate-coupled liposomes via monocarboxylic acid transporters

Background

The blood-brain barrier (BBB) is an obstacle for pharmacologists wishing to find treatments for patients with brain disorders. The BBB restricts the uptake of many valuable hydrophilic drugs and limits their efficacy because of the presence of tight junctions, a high metabolic capacity, low pinocytic vesicular traffic, and efficient efflux mechanisms.

Aim

The present study aimed to characterize lactyl stearate-coupled liposomes and their potential for the brain targeting of rifampin (rifampicin).

Method

A liposomal delivery system was prepared for achieving the brain-targeted delivery of rifampin in 21 albino rats utilizing the monocarboxylic acid transport system. Liposomes were prepared by the cast-film method using phosphatidylcholine and cholesterol. Similarly, lactyl stearate-coupled liposomal systems were prepared by casting lactyl stearate film with lipids. These liposomal formulations were characterized for entrapment efficiency, vesicle size, in vitro drug release (using dialysis membrane), and in vivo drug accumulation in various tissues.

Results

Coupling of lactyl stearate to liposomes had a profound influence on entrapment efficiency. Entrapment efficiency was reduced from 41.28 ± 2.02% in uncoupled liposomes to 34.23 ± 1.60% in coupled liposomes. The vesicle size was increased after coupling with lactyl stearate. The in vitro drug release for the uncoupled formulation LIPO-3 was 62.9 ± 3.01% after 24 hours, whereas that of the coupled formulation LIPO-3-Ls-III was 44.5 ± 2.09%. The percentage of rifampin dose recovered from the brain following administration of lactyl stearate-coupled liposomes to albino rats at different time intervals was about 6–8 times higher than with uncoupled liposomes and about 10–12 times higher than with the plain drug solution.

Conclusion

Lactyl stearate-coupled liposomes were better localized within the brain compared to uncoupled liposomes. Lactyl stearate-coupled liposomes could be an excellent carrier system for brain targeting of the hydrophilic drug rifampin.     

Pharmacological Characterization of 7-(4-(Piperazin-1-yl)) Ciprofloxacin Derivatives: Antibacterial Activity,Cellular Accumulation,Susceptibility to Efflux Transporters,and Intracellular Activity

Purpose

To evaluate pharmacological properties (antibacterial activity; accumulation in phagocytic cells; activity against intracellular bacteria; susceptibility to fluoroquinolone efflux transporters) of ciprofloxacin derivatives modified at C-7 of the piperazine ring.

Methods

N-acetyl- (1), N-benzoyl- (2), N-ethyl- (3), and N-benzyl- (4) ciprofloxacin were synthesized. MICs against Escherichia coli and Staphylococcus aureus were determined following CLSI guidelines. Cellular accumulation, subcellular distribution, and intracellular activity (towards S. aureus and Listeria monocytogenes) were determined in J774 mouse macrophages. Efflux in bacteria (NorA [S. aureus], Lde [L. monocytogenes]) and in macrophages (Mrp4) was assessed using the corresponding inhibitors reserpine and gemfibrozil, respectively.

Results

All derivatives were active, though less than ciprofloxacin. 2 and 3 accumulated 2–3 fold more than ciprofloxacin in mouse macrophages but remained substrates for efflux by Mrp4. 4 was insensitive to NorA and Lde, accumulated approx 50-fold more than ciprofloxacin in macrophages, was barely affected by Mrp4, localized in the soluble fraction of cells, and was equipotent to ciprofloxacin against intracellular bacteria.

Conclusions

Benzyl substitution at C7 markedly affects the pharmacological profile of ciprofloxacin with respect to recognition by efflux transporters and cellular accumulation. N-benzyl-ciprofloxacin may serve as basis for designing molecules with higher intrinsic activity while remaining poorly susceptible to efflux.     

Prolonged-release ciprofloxacin

Prolonged-release ciprofloxacin (ciprofloxacin PR) is a novel oral formulation of the fluoroquinolone antibacterial that allows once-daily administration. The polymeric matrix of the tablet particles swells so that the particles are retained in the fed stomach. The particles erode on contact with gastric acid, releasing approximately 90% of a 500mg ciprofloxacin PR dose at a near constant rate to the upper gastrointestinal tract over a 6-hour period.

The bactericidal activity of ciprofloxacin PR is similar to that of immediate-release ciprofloxacin (ciprofloxacin IR). Both formulations showed similar in vitro activity against common uropathogens, including Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. In patients with ciprofloxacin-susceptible uncomplicated urinary tract infections, bacterial eradication rates for each of these uropathogens were similar with ciprofloxacin PR or ciprofloxacin IR.

Oral ciprofloxacin PR 500mg once daily produces similar systemic exposure to that of ciprofloxacin IR 250mg twice daily, but the time to maximum plasma concentration is prolonged and the initial peak in drug concentration is higher than with ciprofloxacin IR. A similar pattern is seen in terms of urinary excretion. Other pharmacokinetic parameters are similar to those of ciprofloxacin IR.

In 523 evaluable women with ciprofloxacin-susceptible uncomplicated urinary tract infection, 3 days’ treatment with ciprofloxacin PR 500mg once daily had similar efficacy to ciprofloxacin IR 250mg twice daily. Initial bacterial eradication rates were ≥90% and initial clinical cure rates were ≥86% for either formulation.

Ciprofloxacin PR was well tolerated in clinical trials in women with acute cystitis. Fungal infection (mostly vaginal yeast infection) was the most common adverse event possibly related to ciprofloxacin PR treatment. A tolerability advantage for ciprofloxacin PR over ciprofloxacin IR was seen in terms of nausea and diarrhea, which occurred significantly less often with ciprofloxacin PR.

     

Nano Composite Emulsion for Sustained Drug Release and Improved Bioavailability

Purpose

To propose a novel composite nanoemulsion formulation that contains no surfactant, but offers great stability and improved oral absorption capabilities.

Methods

The nanoemulsions were prepared by dispersing the oil phase into aqueous solutions containing different amounts of the PMMA/silica composite nanoparticles. The stability was tested under extreme conditions. The structure features of the nanoemulsion droplets were investigated using Electron microscope. The in vitro drug release and in vivo drug absorption profiles after oral administration were investigated using Cyclosporin A as a model drug.

Results

The composite nanoemulsion demonstrated great stability under various disruptive conditions. Electron microscopy studies indicated the existence of internal and surface domains in the nano-droplet structure. In vitro drug release and in vivo uptake characterizations also confirmed the unique interfacial properties of such nanoemulsion structures.

Conclusions

The novel nanoemulsion formulation may have modulated drug release profiles and alternative oral absorption mechanisms, which could offer significant advantages compared to traditional emulsion formulations.     

Liposomal Aerosols of Nitric Oxide (NO) Donor as a Long-Acting Substitute for the Ultra-Short-Acting Inhaled NO in the Treatment of PAH

Purpose

This study seeks to develop a liposomal formulation of diethylenetriamine NONOate (DN), a long acting nitric oxide (NO) donor, with a goal to replace inhaled NO (iNO) in the treatment of pulmonary arterial hypertension (PAH).

Methods

Liposomal formulations were prepared by a lipid film hydration method and modified with a cell penetrating peptide, CAR. The particles were characterized for size, polydispersity index (PDI), zeta potential, entrapment efficiency, storage and nebulization stability, and in-vitro release profiles. The cellular uptake and transport were assessed in rat alveolar macrophages (NR8383) and transforming growth factor β (TGF-β) activated rat pulmonary arterial smooth muscle cells (PASMCs). The fraction of the formulation that enters the systemic circulation, after intratracheal administration, was determined in an Isolated Perfused Rat Lung (IPRL) model. The safety of the formulations were assessed using an MTT assay and by measuring injury markers in the bronchoalveolar lavage (BAL) fluid; the pharmacological efficacy was evaluated by monitoring the changes in the mean pulmonary arterial (mPAP) and systemic pressure (mSAP) in a monocrotaline (MCT) induced-PAH rat model

Results

Liposome size, zeta potential, and entrapment efficiency were 171?±?4 nm, -37?±?3 mV, and 46?±?5%, respectively. The liposomes released 70?±?5% of the drug in 8 h and were stable when stored at 4°C. CAR-conjugated-liposomes were taken up more efficiently by PASMCs than liposomes-without-CAR; the uptake of the formulations by rat alveolar macrophages was minimal. DN-liposomes did not increase lung weight, protein quantity, and levels of injury markers in the BAL fluid. Intratracheal CAR-liposomes reduced the entry of liposomes from the lung to blood; the formulations produced a 40% reduction in mPAP for 180 minutes.

Conclusion

This study establishes the proof-of-concept that peptide modified liposomal formulations of long-acting NO donor can be an alternative to short-acting iNO.

     

Antimicrobial Drugs Encapsulated in Fibrin Nanoparticles for Treating Microbial Infested Wounds

Purpose

In vitro evaluation of antibacterial and antifungal drugs encapsulated fibrin nanoparticles to prove their potential prospect of using these nanocomponent for effective treatment of microbial infested wounds.

Methods

Surfactant-free oil-in-water emulsification-diffusion method was adopted to encapsulate 1 mg/ml each of antimicrobial drugs (Ciprofloxacin and Fluconazole) in 4 ml of aqueous fibrinogen suspension and subsequent thrombin mediated cross linking to synthesize drug loaded fibrin nanoparticles.

Results

Ciprofloxacin loaded fibrin nanoparticles (CFNPs) showed size range of 253?±?6 nm whereas that of Fluconazole loaded fibrin nanoparticles (FFNPs) was 260?±?10 nm. Physico chemical characterizations revealed the firm integration of antimicrobial drugs within fibrin nanoparticles. Drug release studies performed at physiological pH 7.4 showed a release of 16% ciprofloxacin and 8% of fluconazole while as the release of ciprofloxacin at alkaline pH 8.5, was 48% and that of fluconazole was 37%. The antimicrobial activity evaluations of both drug loaded systems independently showed good antibacterial activity against Escherichia coli (E.coli), Staphylococcus aureus (S. aureus) and antifungal activity against Candida albicans (C. albicans). The in vitro toxicity of the prepared drug loaded nanoparticles were further analyzed using Human dermal fibroblast cells (HDF) and showed adequate cell viability.

Conclusion

The efficacies of both CFNPs and FFNPs for sustained delivery of encapsulated anti microbial drugs were evaluated in vitro suggesting its potential use for treating microbial infested wounds (diabetic foot ulcer).     

Microstructural Elucidation of Self-Emulsifying System: Effect of Chemical Structure

Purpose

Self-emulsifying systems (SES) emulsify spontaneously to produce fine oil-in-water emulsion when introduced into aqueous phase. The self-emulsification process plays an important role during formation of emulsion. The objective of current work was to understand and explore the inner structuration of SES through controlled hydration and further to study the influence of additive on the same which ultimately governs performance of final formulation in terms of droplet size.

Methods

Droplet size of final formulations containing structural analogues of ibuprofen was determined. Microstructural properties of intermediate hydrated regimes of SES were investigated using techniques such as small angle X-ray scattering, differential scanning calorimetry and rheology.

Results

The current work established inverse relationship between droplet size of the formulations containing structural analogues of ibuprofen and their Log P values. Microstructural analysis of intermediate hydrated regimes of the prepared samples showed formation of local lamellar structure. Structural analogues of ibuprofen significantly altered microstructure of lamellae which was well correlated with the droplet size of final formulations. In vitro drug release study showed increase in dissolution rate of lipophillic drugs when formulated as SES.

Conclusion

The current work emphasizes the fact that tailor-made formulations can be prepared by controlling the properties of intermediate regimes.

The Extracellular Microenvironment Explains Variations in Passive Drug Transport Across Different Airway Epithelial Cell Types

Purpose

We sought to identify key variables in cellular architecture and physiology that might explain observed differences in the passive transport properties of small molecule drugs across different airway epithelial cell types.

Methods

Propranolol (PR) was selected as a weakly basic, model compound to compare the transport properties of primary (NHBE) vs. tumor-derived (Calu-3) cells. Differentiated on Transwell? inserts, the architecture of pure vs. mixed cell co-cultures was studied with confocal microscopy followed by quantitative morphometric analysis. Cellular pharmacokinetic modeling was used to identify parameters that differentially affect PR uptake and transport across these two cell types.

Results

Pure Calu-3 and NHBE cells possessed different structural and functional properties. Nevertheless, mixed Calu-3 and NHBE cell co-cultures differentiated as stable cell monolayers. After measuring the total mass of PR, the fractional areas covered by Calu-3 and NHBE cells allowed deconvoluting the transport properties of each cell type. Based on the apparent thickness of the unstirred, cell surface aqueous layer, local differences in the extracellular microenvironment explained the measured variations in passive PR uptake and permeation between Calu-3 and NHBE cells.

Conclusion

Mixed cell co-cultures can be used to compare the local effects of the extracellular microenvironment on drug uptake and transport across two epithelial cell types.     

Novel Topical Ophthalmic Formulations for Management of Glaucoma

Purpose

Preparation of topical ophthalmic formulations containing brimonidine-loaded nanoparticles prepared from various biodegradable polymers—PCL, PLA and PLGA—for sustained release of brimonidine as a once daily regimen for management of glaucoma.

Methods

Nanoparticles were prepared using spontaneous emulsification solvent diffusion method then characterized regarding their particle size, zeta potential, morphology and drug contents. Brimonidine-loaded nanoparticles were incorporated into eye drops, temperature-triggered in situ gelling system and preformed gel and characterized regarding their pH, viscosity, uniformity of drug contents, in vitro release study, in vitro cytotoxicity and in vivo intraocular pressure (IOP) lowering effects.

Results

The results of optimized brimonidine-loaded PCL-, PLGA- and PLA-NPs respectively, are: particle sizes of 117.33?±?4.58 nm, 125.67?±?5.15 nm and 131.67?±?3.79 nm; zeta potentials of ?18.5?±?2.87 mV, ?21.82?±?2.7 mV and ?28.11?±?2.21 mV; and encapsulation efficiencies of 77.97?±?1.38%, 68.65?±?3.35% and 73.52?±?2.92%. TEM analyses revealed that all NPs have spherical shapes with dense core and distinct coat. In vitro release data showed a sustained release without any burst effect with Higuchi non-Fickian diffusion mechanism. Cytotoxicity studies revealed that all formulations are non-toxic. Also all formulations possessed a sustained IOP lowering effect compared to Alphagan® P eye drops.

Conclusions

Our formulations showed prolonged management of glaucoma that should meet with better patient compliance as a once-daily formulation.     

Nano-Encapsulation of Plitidepsin: In Vivo Pharmacokinetics,Biodistribution, and Efficacy in a Renal Xenograft Tumor Model

Purpose

Plitidepsin is an antineoplasic currently in clinical evaluation in a phase III trial in multiple myeloma (ADMYRE). Presently, the hydrophobic drug plitidepsin is formulated using Cremophor®, an adjuvant associated with unwanted hypersensitivity reactions. In search of alternatives, we developed and tested two nanoparticle-based formulations of plitidepsin, aiming to modify/improve drug biodistribution and efficacy.

Methods

Using nanoprecipitation, plitidepsin was loaded in polymer nanoparticles made of amphiphilic block copolymers (i.e. PEG-b-PBLG or PTMC-b-PGA). The pharmacokinetics, biodistribution and therapeutic efficacy was assessed using a xenograft renal cancer mouse model (MRI-H-121 xenograft) upon administration of the different plitidepsin formulations at maximum tolerated multiple doses (0.20 and 0.25 mg/kg for Cremophor® and copolymer formulations, respectively).

Results

High plitidepsin loading efficiencies were obtained for both copolymer formulations. Considering pharmacokinetics, PEG-b-PBLG formulation showed lower plasma clearance, associated with higher AUC and Cmax than Cremophor® or PTMC-b-PGA formulations. Additionally, the PEG-b-PBLG formulation presented lower liver and kidney accumulation compared with the other two formulations, associated with an equivalent tumor distribution. Regarding the anticancer activity, all formulations elicited similar efficacy profiles, as compared to the Cremophor® formulation, successfully reducing tumor growth rate.

Conclusions

Although the nanoparticle formulations present equivalent anticancer activity, compared to the Cremophor® formulation, they show improved biodistribution profiles, presenting novel tools for future plitidepsin-based therapies.     

Liposomal Irinotecan Accumulates in Metastatic Lesions,Crosses the Blood-Tumor Barrier (BTB), and Prolongs Survival in an Experimental Model of Brain Metastases of Triple Negative Breast Cancer

Purpose

The blood-tumor barrier (BTB) limits irinotecan distribution in tumors of the central nervous system. However, given that the BTB has increased passive permeability we hypothesize that liposomal irinotecan would improve local exposure of irinotecan and its active metabolite SN-38 in brain metastases relative to conventional irinotecan due to enhanced-permeation and retention (EPR) effect.

Methods

Female nude mice were intracardially or intracranially implanted with human brain seeking breast cancer cells (brain metastases of breast cancer model). Mice were administered vehicle, non-liposomal irinotecan (50 mg/kg), liposomal irinotecan (10 mg/kg and 50 mg/kg) intravenously starting on day 21. Drug accumulation, tumor burden, and survival were evaluated.

Results

Liposomal irinotecan showed prolonged plasma drug exposure with mean residence time (MRT) of 17.7 ± 3.8 h for SN-38, whereas MRT was 3.67 ± 1.2 for non-liposomal irinotecan. Further, liposomal irinotecan accumulated in metastatic lesions and demonstrated prolonged exposure of SN-38 compared to non-liposomal irinotecan. Liposomal irinotecan achieved AUC values of 6883 ± 4149 ng-h/g for SN-38, whereas non-liposomal irinotecan showed significantly lower AUC values of 982 ± 256 ng-h/g for SN-38. Median survival for liposomal irinotecan was 50 days, increased from 37 days (p<0.05) for vehicle.

Conclusions

Liposomal irinotecan accumulates in brain metastases, acts as depot for sustained release of irinotecan and SN-38, which results in prolonged survival in preclinical model of breast cancer brain metastasis.

     

The Potential Efficacy of R8-Modified Paclitaxel-Loaded Liposomes on Pulmonary Arterial Hypertension

Purpose

In this paper, a novel liposomal formulation of paclitaxel modified with octaarginine (R8) was fabricated and the therapeutic efficacy of it on pulmonary arterial hypertension was evaluated.

Methods

Octaarginine-modified stealth liposomes loaded with PTX (R8-PTX-LIP) were prepared and characterized. Vector cytoxicity and anti-proliferation ability of different formulations on primary cultured VSMCs were determined with MTT assay. The uptake capacity of VSMCs on different formulations were evaluated by flow cytometry, and the influences on cytoskeletons of liposomes were investigated by cytoskeleton staining with rhodamine-phalloidin. The biodistribution of liposomes were imaged by a CCD camera using a near-infrared fluorophore DiD. The therapeutic efficacy of different PTX-formulations of PAH was evaluated by hemodynamic measurement, right ventricular hypertrophic parameters and vessel diameters.

Results

The cellular uptake of R8 modified liposomes (R8-LIP) was improved noticeably compared with other groups. All liposomes did not exert cytotoxicity on VSMCs in 24 h. R8-PTX-LIP exhibited the strongest inhibitory effect on the proliferation of VSMCs among all the formulations (p?<?0.001). R8-PTX-LIP could reverse the phenotype transformation, and inhibit cell migration. mPAP, (RV/LV+S) and the wall thickness of small distal pulmonary arteries of rats treated with R8-PTX-LIP were significantly lower than those from other groups (p?<?0.001).

Conclusions

In conclusion, the drug delivery system of R8-modified paclitaxel-loaded liposomes we established showed pronounced inhibitory effect over VSMCs proliferation and cytoskeleton formation in vitro, a stronger pulmonary delivery ability in vivo, and was effective on PAH, showing the potential for pulmonary drug delivery system for PAH treatment.     

PLGA/Liposome Hybrid Nanoparticles for Short-Chain Ceramide Delivery

Purpose

Rapid premature release of lipophilic drugs from liposomal lipid bilayer to plasma proteins and biological membranes is a challenge for targeted drug delivery. The purpose of this study is to reduce premature release of lipophilic short-chain ceramides by encapsulating ceramides into liposomal aqueous interior with the aid of poly (lactic-coglycolicacid) (PLGA).

Methods

BODIPY FL labeled ceramide (FL-ceramide) and BODIPY-TR labeled ceramide (TR-ceramide) were encapsulated into carboxy-terminated PLGA nanoparticles. The negatively charged PLGA nanoparticles were then encapsulated into cationic liposomes to obtain PLGA/liposome hybrids. As a control, FL-ceramide and/or TR ceramide co-loaded liposomes without PLGA were prepared. The release of ceramides from PLGA/liposome hybrids and liposomes in rat plasma, cultured MDA-MB-231 cells, and rat blood circulation was compared using fluorescence resonance energy transfer (FRET) between FL-ceramide (donor) and TR-ceramide (acceptor).

Results

FRET analysis showed that FL-ceramide and TR-ceramide in liposomal lipid bilayer were rapidly released during incubation with rat plasma. In contrast, the FL-ceramide and TR-ceramide in PLGA/liposome hybrids showed extended release. FRET images of cells revealed that ceramides in liposomal bilayer were rapidly transferred to cell membranes. In contrast, ceramides in PLGA/liposome hybrids were internalized into cells with nanoparticles simultaneously. Upon intravenous administration to rats, ceramides encapsulated in liposomal bilayer were completely released in 2 min. In contrast, ceramides encapsulated in the PLGA core were retained in PLGA/liposome hybrids for 4 h.

Conclusions

The PLGA/liposome hybrid nanoparticles reduced in vitro and in vivo premature release of ceramides and offer a viable platform for targeted delivery of lipophilic drugs.