Cytarabine release from comatrices of albumin microspheres in a poly(lactide–co-glycolide) film: in vitro and in vivo studies

A smart approach to enable preclinical studies in pharmaceutical industry: PLGA-based extended release formulation platform for subcutaneous applications

Objective: Validation of a prospective new therapeutic concept in a proof of concept study is costly and time-consuming. In particular, pharmacologically active tool compounds often lack suitable pharmacokinetic (PK) properties for subsequent studies. The current work describes a PLGA-based formulation platform, encapsulating different preclinical research compounds into extended release microparticles, to optimize their PK properties after subcutaneous administration.Significance: Developing a PLGA-based formulation platform offers the advantage of enabling early proof of concept studies in pharmaceutical research for a variety of preclinical compounds by providing a tailor-made PK profile.Methods: Different model compounds were encapsulated into PLGA microparticles, utilizing emulsification solvent evaporation or spray drying techniques. Formulations aiming different release rates were manufactured and characterized. Optimized formulations were assessed in in vivo studies to determine their PK properties, with the mean residence time (MRT) as one key PK parameter.Results: Utilizing both manufacturing methods, tested tool compounds were encapsulated successfully, with a drug load between 5% and 40% w/w, and an extended release time up to 250 h. In the following PK studies, the MRT was extended by a factor of 90, resulting in prolonged coverage of the required target through level. This approach was confirmed to be equally successful for additional internal compounds, verifying a general applicability of the platform.Conclusion: For different active pharmaceutical ingredients (API), an optimized, tailor-made PK profile was obtained utilizing the described formulation platform. This approach is applicable for a variety of pharmacologically active tool compounds, reducing timelines and costs in preclinical research.

Construction of a Novel Magnetic Targeting Anti-Tumor Drug Delivery System: Cytosine Arabinoside-Loaded Bacterial Magnetosome

To ease the side effects triggered by cytosine arabinoside (Ara-C) for acute leukemia treatment, a novel magnetic targeting anti-tumor drug delivery system was constructed through bacterial magnetosomes (BMs) from Magnetospirillum magneticum AMB-1 combined with Ara-C by crosslinking of genipin (GP). The results showed that Ara-C could be bonded onto the membrane surface of BMs effectively through chemical crosslinking induced by dual hand reagents GP. The average diameters of BMs and Ara-C-coupled BMs (ABMs) were 42.0 ± 8.6 and 72.7 ± 6.0 nm respectively, and the zeta potentials (−38.1 ± 9.1) revealed that these systems were stable, confirming the stability of the system. The optimal encapsulation efficiency and drug loading were 89.05% ± 2.33% and 47.05% ± 0.64% respectively when crosslinking reaction lasted for 72 h. The system also presented long-term stability and release behaviors without initial burst release (Ara-C could be released 80% within three months). Our results indicate that BMs have great potential in biomedical and clinical fields as a novel anti-tumor drug carrier.

Sterilization stability of vesicular phospholipid gels loaded with cytarabine for brain implant

The aim of this study was to investigate the sterilization stability of cytarabine (Ara-C) loaded vesicular phospholipid gels (VPGs). VPGs were prepared by high pressure homogenization method intended for the treatment of glioblastoma multiforme (GBM) in brain as injectable implant. The particle size of VPGs after redispersion was 119.6 ± 66.24 nm, and entrapment efficiency (EE) was 32.6 ± 2.1%. Drug release in vitro from VPGs sustained for 80 h with 48.1% initial release within 1h, and rheological studies demonstrated a gel-like behavior. Comparatively, after autoclaved sterilization, increased particle size and EE were obtained as 165.6 ± 71.89 nm and 62.6 ± 2.3%, respectively. Additionally, characteristics of drug release were significantly altered with obviously prolonged release time to 450 h and remarkable reduced initial release to 24.7%. Also, the viscoelasticity was reinforced with clearly decreased fluidity. This result could be explained by the fusion of small vesicles witnessed in TEM observation, which resulted in percentages change of vesicle groups with different size. However, reduced Ara-C and increased lysophosphatidylcholine (LPC) were observed. Among the stabilizers, addition of sodium sulfite showed best effects with high stability of Ara-C and phospholipids. This may be explained by the presence of SO(3)(-), free radicals produced by sodium sulfite. Being an hydroxyl radical scavenger, it can reduce the generation of HO free radicals. These results show that, with addition of appropriate stabilizers, VPGs can be autoclaved with high stability, and it is a promising dosage form for treatment of GBM after injection into resectable or nonresectable neoplasms with sustained release properties.

HPLC–MS/MS method for the determination of cytarabine in human plasma

Background: Cytarabine is an anti-tumor drug that is currently under investigation for treatment in combination with other anticancer drugs for the chemotherapy of leukemia. The quantitative determination of cytarabine in plasma is challenging due to the required sensitivity, its in vitro instability and the presence of an isobaric endogenous compound, cytidine. Owing to the polarity of cytarabine, conventional chromatography cannot provide adequate separation of the analyte and the interfering compounds. A few analytical methods have been reported for the determination of cytarabine in plasma, but their sensitivity was not sufficient since most of these methods apply spectrophotometric detection. Results: In this article, an LC–MS/MS method is described for the determination of cytarabine in human plasma down to the sub ng/ml level. To prevent conversion of cytarabine by cytidine deaminase, whole blood samples were stabilized with tetrahydrouridine directly after the collection of whole blood at the clinical site. Cation-exchange SPE was employed to extract cytarabine from 50 µl human plasma. UHPLC on high strength silica T3 column (100 × 2.1 mm × 1.8 µm) was applied to achieve adequate separation of cytarabine from cytidine within a reasonable run time of 5 min. A triple quad mass spectrometer equipped with an ESI source was used for detection. Conclusion: The method was linear over the concentration ranges of 0.500–500 ng/ml. The intra- and inter-day relative standard deviation (precision) as well as the bias (accuracy) were well below 15%. In the presence of tetrahydrouridine, cytarabine was sufficiently stable under all relevant conditions. The method was successfully applied to support a clinical pharmacokinetic study with a low dose of cytarabine.

Smart nanocontainers as depot media for feedback active coatings

Among the grand challenges at present are ways to develop systems with low consumption of raw materials and with little load on the environment. In view of this it is of utmost importance to avoid or to delay processes causing material destruction. This is especially urgent, since many protective substances have associated health hazards, and new routes to improve the situation are a main concern of this contribution. Nanocapsules (nanocontainers) with controlled release properties of the shell can be used to fabricate a new family of active coatings, with quick response to changes of the coating environment or coating integrity. The release of active materials encapsulated into nanocapsules is triggered by various external and internal factors, thus preventing spontaneous leakage of the active component. The coating can have several active functionalities when several types of nanocapsules loaded with corresponding active agent are incorporated simultaneously into a coating matrix. We highlight recent achievements in development and application of filled responsive containers in biomedical and self-healing protective coatings.

Time controlled release of arabinofuranosylcytosine (Ara-C) from agarose hydrogels using layer-by-layer assembly: an in vitro study

Experimentally induced axonal regeneration is compromised by glial scar formation arising from leptomeningeal fibroblasts cells in and around the hydrogel scaffold implanted for nerve repair. Strategies are needed to prevent such fibroblastic reactive cell layer formation for enhanced axonal regeneration. Here, we implement the technique of layer-by-layer assembled degradable, hydrogen bonded multilayers on agarose hydrogels to incorporate an anti-mitotic drug (1-β-D-arabinofuranosylcytosine (Ara-C)) within the agarose hydrogels. We show controlled release of Ara-C under physiological conditions over a period of days. The concentrations of Ara-C released from agarose at the different time points were sufficient to inhibit fibroblast growth in vitro, while not adversely affecting the viability of the neuronal cells.

Ethanol injection method for hydrophilic and lipophilic drug-loaded liposome preparation

In this article, a hydrophobic (beclomethasone dipropionate; BDP) and a hydrophilic (cytarabine; Ara-C) drugs have been encapsulated in liposomes in order to be administered via the pulmonary route. For this aim, a liposome preparation method, which is easy to scale up, the ethanol injection method, has been selected. The effects of critical process and formulation parameters have been investigated. The drug-loaded liposomes were prepared and characterized in terms of size, zeta potential, encapsulation efficiency, release study, cell uptake, and aerodynamic behavior. Small multilamellar vesicles, with sizes ranging from about 80 to 170 nm, were successfully obtained. Results indicated a significant influence of phospholipid and cholesterol amounts on liposome size and encapsulation efficiency. The higher encapsulation efficiencies were about 100% for the hydrophobic drug (BDP) and about 16% for the hydrophilic one (Ara-C). The in vitro release study showed a prolonged release profile for BDP, in contrast with Ara-C, which was released more rapidly. The cell-uptake test revealed that fluorescent liposomes have been well internalized into the cytoplasm of SW-1573 human lung carcinoma cells, confirming the possibility to use liposomes for lung cell targeting. Nebulized Ara-C and BDP liposomes presented aerodynamic diameters compatible with deep lung deposition. In conclusion, the elaborated liposomes seem to be promising carriers for both Ara-C and BDP pulmonary delivery.

Modified nanoprecipitation method for preparation of cytarabine-loaded PLGA nanoparticles

The present investigation was aimed at developing cytarabine-loaded poly(lactide-coglycolide) (PLGA)-based biodegradable nanoparticles by a modified nanoprecipitation which would have sustained release of the drug. Nine batches were prepared as per 3(2) factorial design to optimize volume of the co-solvent (0.22-0.37 ml) and volume of non-solvent (1.7-3.0 ml). A second 3(2) factorial design was used for optimization of drug: polymer ratio (1:5) and stirring time (30 min) based on the two responses, mean particle size (125 ± 2.5 nm), and percentage entrapment efficiency (21.8 ± 2.0%) of the Cyt-PLGA nanoparticles. Optimized formulation showed a zeta potential of -29.7 mV indicating good stability; 50% w/w of sucrose in Cyt-PLGA NP was added successfully as cryoprotectant during lyophilization for freeze-dried NPs and showed good dispersibility with minimum increase in their mean particle sizes. The DSC thermograms concluded that in the prepared PLGA NP, the drug was present in the amorphous phase and may have been homogeneously dispersed in the PLGA matrix. In vitro drug release from the pure drug was complete within 2 h, but was sustained up to 24 h from PLGA nanoparticles with Fickian diffusion. Stability studies showed that the developed PLGA NPs should be stored in the freeze-dried state at 2-8°C where they would remain stable in terms of both mean particle size and drug content for 2 months.

Nucleoside analogue delivery systems in cancer therapy

Nucleoside analogues (NAs) are important agents in the treatment of hematological malignancies. They are prodrugs that require activation by phosphorylation. Their rapid catabolism, cell resistance and overdistribution in the body jeopardize nucleoside analogue chemotherapy. Accordingly, therapeutic doses of NAs are particularly high and regularly have to be increased, resulting in severe toxicity and narrow therapeutic index. The major challenge is to concentrate the drug at the tumour site, avoiding its distribution to normal tissues. New drug carriers and biomaterials are being developed to overcome some of these obstacles. This review highlights novel NA delivery systems and discusses new technologies that could improve NA cancer therapy.

5-Fluorouracil-loaded microspheres prepared by spray-drying poly(D,L-lactide) and poly(lactide-co-glycolide) polymers: characterization and drug release

5-Fluorouracil (5-FU), a hydrosoluble anti-neoplastic drug, was encapsulated in microspheres of poly(D,L-lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) polymers using the spray-drying technique, in order to obtain small size microspheres with a significant drug entrapment efficiency. Drug-loaded microspheres included between 47 +/- 11 and 67 +/- 12 microg 5-FU mg(-1) microspheres and the percentage of entrapment efficiency was between 52 +/- 12 and 74 +/- 13. Microspheres were of small size (average diameter: 0.9 +/- 0.4-1.4 +/- 0.8 microm microspheres without drug; 1.1 +/- 0.5-1.7 +/- 0.9 microm 5-FU-loaded microspheres) and their surface was smooth and slightly porous, some hollows or deformations were observed in microspheres prepared from polymers with larger Tg. A fractionation process of the raw polymer during the formation of microspheres was observed as an increase of the average molecular weight and also of Tg of the polymer of the microspheres. The presence of 5-FU did not modify the Tg values of the microspheres. Significant interactions between the drug and each one of the polymers did not take place and total release of the included drug was observed in all cases. The time needed for the total drug release (28-129 h) was in the order PLA > PLGA 75/25 > PLGA 50/50. A burst effect (17-20%) was observed during the first hour and then a period of constant release rate (3.52 +/- 0.82-1.46 +/- 0.26 microg 5-FU h(-1) per milligram of microspheres) up to 8 or 13 h, depending on the polymer, was obtained.

Dexamethasone-loaded poly(lactic-co-glycolic) acid microspheres/poly(vinyl alcohol) hydrogel composite coatings for inflammation control

BACKGROUND

Successful performance of implantable glucose biosensors for metabolic monitoring is dependent on tissue compatibility. Negative immunostimulatory tissue reactions that occur due to implantation-induced tissue injury and the prolonged presence of such sensors can lead to a loss of functionality and device failure. The use of novel poly(lactic-co-glycolic) acid (PLGA) microsphere/poly(vinyl alcohol) (PVA) hydrogel composite coatings for implantable biosensors to control localized inflammation and fibrosis at the sensor/tissue interface is reported.

METHODS

Dexamethasone-loaded PLGA microspheres were prepared using a solvent evaporation technique. Composites were fabricated by dispersing microspheres in PVA solution and performing freeze-thaw cycling. Composites were implanted into subcutaneous tissue of rats. In vitro and in vivo drug release kinetics were studied. Immunostimulatory response was determined through histopathological evaluation of excised tissue.

RESULTS

PLGA microsphere/PVA hydrogel composites achieved localized dexamethasone delivery with approximate zero-order release kinetics. A linear level A in vitro-in vivo correlation was observed (R2 = 0.97). Dexamethasone released at a steady rate of 0.17 microg/day was sufficient to control acute and chronic inflammation as well as fibrosis. Implantation of composites containing no drug led to significant infiltration of inflammation-mediating cells at the implant site characteristic of acute inflammation followed by proliferation of a fibrotic band surrounding the implant by week 3.

CONCLUSIONS

PLGA microsphere/PVA hydrogel composites eluting dexamethasone were successful in controlling negative tissue reactions at the sensor-tissue interface by reducing the level of inflammation-mediation cells to those observed in normal tissue. These composites show promise as coatings for implantable biosensors to improve biocompatibility and prolong sensor lifetime.