High Bioavailability of -Tocopherol Loaded into Poly (DL-Lactic-co-Glycolic Acid) Microspheres in Apolipoprotein B Knockout Mice

PURPOSE

To assess the potential clinical value of alpha-tocopherol-loaded poly (DL-lactic-co-glycolic acid) (PLGA) microspheres, we examined the disposition kinetics of alpha-tocopherol after administration of the microspheres to apolipoprotein B (apo B) knockout mice as a model of abetalipoproteinemia.

METHODS

PLGA microspheres containing alpha-tocopherol were prepared by a solvent-evaporation method. The concentration of alpha-tocopherol was measured by gas chromatography-mass spectrometry.

RESULTS

The mean value of particle size of alpha-tocopherol-loaded PLGA microspheres was 108 microm. The loading and the trapping efficiency of alpha-tocopherol in PLGA microspheres were 20.8% and 86.6%, respectively. When alpha-tocopherol solution (25 mg/kg) was subcutaneously administered to apob (+/+) and apob (+/-) mice, the plasma concentrations of alpha-tocopherol reached a peak at 6 h and decreased to the endogenous level within 4 days in both types of mice. However, the area under the plasma concentration-time curve (AUC) of apob (+/-) mice was significantly smaller than that in the case of apob (+/+) mice. When alpha-tocopherol-loaded PLGA microspheres (100 mg/kg) were subcutaneously administered, the plasma concentrations of alpha-tocopherol increased slowly and remained about 2-fold higher than the endogenous level at 5 to 10 days after administration in both types of mice, and there was no significant difference between the AUC values.

CONCLUSIONS

The PLGA microsphere preparation of alpha-tocopherol is expected to be a very useful drug delivery system in vitamin E supplementation therapy for abetalipoproteinemia.

PLGA/TPGS Nanoparticles for Controlled Release of Paclitaxel: Effects of the Emulsifier and Drug Loading Ratio

PURPOSE

We successfully manufactured nanoparticles of biodegradable polymers for controlled release of paclitaxel. TPGS (d-alpha-tocopheryl polyethylene glycol 1000 succinate) could be a novel material to make nanoparticles of high drug encapsulation efficiency (EE) and desired physicochemical and pharmaceutical properties of the drug loaded nanoparticles. Among various controlling parameters in the process, the present work is to elucidate the effects of the surfactant stabilizer and the drug loading ratio.

METHODS

Paclitaxel loaded PLGA nanoparticles were formulated at various drug-loading ratios by a modified single emulsion solvent extraction/evaporation technique. TPGS was introduced either as the emulsifier or as a matrix material component by using different technique. Polyvinyl alcohol (PVA) was also used for a comparison. The nanoparticles of various recipes were characterized by various state-of-the-art instrument technology for their properties.

RESULTS

The EE and the in vitro release behavior were found significantly influenced by the drug loading ratio and the surfactant stabilizer encountered. TPGS involved nanoparticles can have high EE and other favorable properties.

CONCLUSIONS

TPGS could be a novel and effective emulsifier, which can result in high EE and desired properties of paclitaxel-loaded polymeric nanoparticles.

Hydrolytic degradation of poly(lactide-co-glycolide) films: effect of oligomers on degradation rate and crystallinity

Oligomers are thought to accelerate the hydrolytic degradation of devices prepared from poly(lactide-co-glycolide), PLGA, due to their increased number of carboxylic end groups. To experimentally verify this hypothesis, two D,L-lactic acid oligomers having molecular weights close to their critical limit of solubility were synthesized and incorporated into PLGA films in three concentrations (0, 10, and 30% w/w). All films were translucent, rather flexible and initially amorphous. With increasing oligomer concentration the glass transition temperature (T(g)) and the molecular weight of films decreased prior to erosion. The degradation studies show that initial mass loss and water absorption are increased in oligomer-containing films as a function of average molecular weight and oligomer concentration. However, the incorporation of oligomers does not accelerate the degradation of films. By contrast, oligomer-containing films show extended lag phase until onset of polymer erosion. This was shown to be related to crystallization. Moreover, it was found that crystallization occurs earlier in oligomer-containing films and that the degree of crystallization is related to the average molecular weight of the oligomer. These findings bring new insight into the role of oligomers in the degradation process and can be used to explain why erosion in massive polymer devices occurs from the center to the surface.

Biodegradable microparticles for sustained release of a new GnRH antagonist – part I: screening commercial PLGA and formulation technologies

The formulation of a new GnRH antagonist (degarelix) in biodegradable poly(DL-lactide-co-glycolide) (PLGA) microparticles was investigated for the development of a 3-month sustained release formulation to treat prostate cancer. The aim was to screen formulation technologies and distinct copolymers to produce microparticles (MP) of different types with good entrapment efficiency (>85%) and peptide purity (>95%) after gamma sterilization. Basically, three types of degarelix-loaded MP (4, 8 and 16% w/w nominal content) were produced with solvent and non-solvent technologies, namely double-emulsion solvent evaporation, spray-drying and two extrusion methods. Besides composition, commercial copolymers differing in residual monomer content and functional group at the carboxylic terminus (acid or ester) were characterized and employed. Peptide loading capacity and purity, as well as shape, size characteristics, and porosity of the produced microparticles were discussed in relation to technology and copolymer choice. Spray-drying and micro-extrusion were the two preferred formulation technologies because of higher entrapment efficiency and better preservation of peptide purity during production and gamma-sterilization. The impact of formulation technologies on the MP characteristics overwhelmed the impact of copolymer selection. Nevertheless, one particular polymer was discarded since it was more susceptible towards radiolytic degradation. The resulting degarelix-MP will be tested in a biological assay for selection of the formulation based on performance.

In-vivo-Untersuchung zur Degradation von Poly-(D,L-)Laktid- und Poly-(L-Laktid-co-Glykolid)-Osteosynthesematerial

AIMS

Comparison of the degradation of poly(D,L)lactide (Resorb X) or poly(lactide-co-glycolide) (LactoSorb) in vivo.

MATERIAL AND METHODS

LactoSorb and Resorb X osteosynthesis plates were fixed at the lateral aspect of the femora of 26 Chinchilla rabbits using the respective osteosynthesis screws. After intraperitoneal injection of fluorochromes the screw plate bone blocks were resected after 1, 6, 12, 14, 16, 21, 26 months and radiologic, histologic as well as fluorescence microscopic examinations were carried out.

RESULTS

Newly formed bone was detectable above and beneath the polymers 1 month after the implantation. The implants were totally covered by newly formed bone after 6 months. While the LactoSorb screws were found to be as birefringent as after 1 month, in the Resorb X screws a continuous resorption by phagocytizing marrow cells starting from the periphery was detectable. Resorb X was totally resorbed in histologic slides 12 months after implantation, while total resorption of LactoSorb lasted 14 months; both polymers were replaced by marrow cells. Bone remodeling was not finished 26 months after implantation in both polymers.

CONCLUSION

Resorption of Resorb X was finished earlier than the resorption of LactoSorb. Both materials were found by fluorescence microscope to be completely resorbed after 12 or 14 months, but bone remodeling of the screw holes was not yet finished 26 months after implantation.

Encapsulation of protamine sulphate compacted DNA in polylactide and polylactide–co-glycolide microparticles

This paper details the development and characterisation of a DNA-loaded microsphere system for gene delivery purposes. Encapsulation of DNA in microspheres was carried out by precondensation of the DNA with protamine sulphate, followed by encapsulation in a polymeric microsphere using a water-oil-water (w/o/w) solvent evaporation-emulsion process. The polymers used were polylactide and polylactide-co-glycolide. The amount of DNA encapsulated in the microsphere formulation was dependent on the weight ratio of protamine sulphate: DNA, with higher ratios (0.87:1 or 2:1) giving better encapsulation efficiencies (> or =62%). Additionally, compared to non-compacted DNA, the encapsulation of a protamine sulphate:DNA complex increased protection of the DNA against nuclease and decreased shear effects during processing. The release profile of DNA was shown to be dependent on the polymer type and polymer molecular weight. DNA was released relatively quickly from the microspheres and the released DNA primarily existed in a relaxed state. However, in vitro transfection experiments indicated that the DNA was still active upon release from the microspheres.

Polymer degradation and in vitro release of a model protein from poly(d,l-lactide-co-glycolide) nano- and microparticles

The objective of the study was to investigate the effect of particle size of nano- and microparticles formulated from poly(D,L-lactide-co-glycolide) (50:50 PLGA) on polymer degradation and protein release. Since the surface area to volume ratio is inversely proportional to the particle size, it is hypothesized that the particle size would influence the polymer degradation as well as the release of the encapsulated protein. PLGA nano- and microparticles of approximate mean diameters of 0.1, 1 and 10 microm, containing bovine serum albumin as a model protein, were formulated using a multiple water-in-oil-in-water emulsion solvent evaporation technique. These particles were incubated at 37 degrees C in phosphate-buffered saline (pH 7.4, 154 mM) and the particles were characterized at various time points for molecular weight of polymer, surface-associated polyvinyl alcohol content (PVA), and the particle surface topology using scanning electron microscopy. The supernatants from the above study were analyzed for the released protein and PVA content. Polymer degradation was found to be biphasic in both nano- and microparticles, with an initial rapid degradation for 20-30 days followed by a slower degradation phase. The 0.1 microm diameter nanoparticles demonstrated relatively higher polymer degradation rate (P<0.05) during the initial phase as compared to the larger size microparticles (first order degradation rate constants of 0.028 day(-1), 0.011 day(-1) and 0.018 day(-1) for 0.1, 1 and 10 microm particles, respectively), however the degradation rates were almost similar (0.008 to 0.009 day(-1)) for all size particles during the later phase. All size particles maintained their structural integrity during the initial degradation phase; however, this was followed by pore formation, deformation and fusion of particles during the slow degradation phase. Protein release from 0.1 and 1 microm particles was greater than that from 10 microm size particles. In conclusion, the polymer degradation rates in vitro were not substantially different for different size particles despite a 10- and 100-fold greater surface area to volume ratio for 0.1 microm size nanoparticles as compared to 1 and 10 microm size microparticles, respectively. Relatively higher amounts of the surface-associated PVA found in the smaller-size nanoparticles (0.1 microm) as compared to the larger-size microparticles could explain some of the observed degradation results with different size particles.

A potential approach for decreasing the burst effect of protein from PLGA microspheres

A central issue in controlled delivery of therapeutics from biodegradable microspheres is the immediate burst of drug release upon injection. This burst is often observed with microsphere systems made by the double emulsion (w/o/w) technique, and may be prevented by improving the drug distribution throughout the polymer matrix. To this end, protein and polymer (poly-lactide-co-glycolide or PLGA) were dissolved within the same solvent system, and micron-sized microspheres were created from this solution by spontaneous emulsification. Improved protein loading was achieved by ion-pairing the protein with charged surfactants to increase solubility in the single-phase solvent system. Both in vitro and in vivo results showed a much diminished burst: compared to microspheres made by double emulsion, it was reduced over 10-fold.

An eight-month clinical study of LA-2575 30.0 mg: a new 4-month, subcutaneous delivery system for leuprolide acetate in the treatment of prostate cancer

OBJECTIVES

To investigate the safety, efficacy, and pharmacokinetics of a new 4-month subcutaneous depot of leuprolide acetate in patients with prostate cancer.

METHODS

Ninety patients diagnosed with adenocarcinoma of the prostate were enrolled in an open-label, multicenter study. LA-2575 30.0 mg was administered subcutaneously once every 4 months for 8 months. The primary efficacy parameter was a serum testosterone level of 50 ng/dL or less. The pharmacokinetics of leuprolide acetate were analyzed in the first 24 enrolled patients. The values are reported as the mean +/- standard error.

RESULTS

Of 90 enrolled patients, 82 (91%) completed the 8-month study. Eight patients voluntarily withdrew from the study for the following reasons: nonmedical reasons (n = 3), treatment-related adverse events (n = 3), disease progression (n = 1), and cardiovascular disease (n = 1). By day 28, 85 (94%) of the 90 patients had achieved a serum testosterone level less than 50 ng/dL. At study completion, 88 (98%) of the 90 patients had a testosterone value less than the castrate level (mean 12.4 +/- 0.8 ng/dL), with 81 (90%) at less than 20 ng/dL. From baseline to month 6, the mean luteinizing hormone level had decreased from 7.51 +/- 0.69 mIU/mL to 0.12 +/- 0.02 mIU/mL. The mean prostate-specific antigen level had decreased 90% from 13.2 +/- 2.0 ng/mL at baseline to 1.3 +/- 0.3 ng/mL at 8 months. No clinically significant flare reactions were observed. The most common treatment-related adverse event was mild hot flashes.

CONCLUSIONS

LA-2575 30.0-mg depot consistently produced and maintained safe and effective suppression of serum testosterone, with total serum testosterone concentrations well below the medical castrate level of less than 50 ng/dL.

PLG microsphere size controls drug release rate through several competing factors

PURPOSE

Although the rate of drug release from poly(D,L-lactide-co-glycolide) (PLG) microspheres is often modulated by changing fabrication conditions or materials, the specific factors directly controlling the release profiles are often unclear. We have fabricated uniform rhodamine- and piroxicam-containing microspheres, 10 to 100 microm in diameter, to better understand how microsphere size controls drug release.

METHODS

Drug distribution within the microspheres was examined using confocal fluorescence microscopy. The rate of polymer degradation was determined as the change in molecular weight, measured by gel permeation chromatography, during in vitro degradation experiments. Further, changes in the surface and interior morphology of the particles during in vitro degradation were investigated by scanning electron microscopy.

RESULTS

Microsphere size greatly affected drug distribution. Small (approximately 10-microm) microspheres showed an essentially uniform drug distribution. Larger (approximately 100-microm) microspheres showed redistribution of drug to specific regions of the microspheres. Rhodamine partitioned to the surface and piroxicam partitioned to the interior of large PLG microspheres. Further, the rate of polymer degradation increased with microsphere size, possibly the result of a more acidic interior caused by increased accumulation of hydrolyzed polymer products in larger particles. Finally, larger microspheres developed a more porous interior structure during the drug release.

CONCLUSION

Microsphere size affects drug release not only through changes in diffusion rates but also through secondary effects including drug distribution in the particle, polymer degradation rate, and microsphere erosion rates.

Effect of copolymer composition on the physicochemical characteristics, in vitro stability, and biodistribution of PLGA-mPEG nanoparticles

The physicochemical properties, the colloidal stability in vitro and the biodistribution properties in mice of different PLGA-mPEG nanoparticle compositions were investigated. The nanoparticles were prepared by a precipitation-solvent evaporation technique. The physical characteristics and the colloidal stability of the PLGA-mPEG nanoparticles were significantly influenced by the composition of the PLGA-mPEG copolymer used to prepare the nanoparticles. PLGA-mPEG nanoparticles prepared from copolymers having relatively high mPEG/PLGA ratios were smaller and less stable than those prepared from copolymers having relatively low mPEG/PLGA ratios. All PLGA-mPEG nanoparticle compositions exhibited prolonged residence in blood, compared to the conventional PLGA nanoparticles. The composition of the PLGA-mPEG copolymer affected significantly the blood residence time and the biodistribution of the PLGA-mPEG nanoparticles in liver, spleen and bones. The in vivo behavior of the different PLGA-mPEG nanoparticle compositions did not appear to correlate with their in vitro stability. Optimum mPEG/PLGA ratios appeared to exist leading to long blood circulation times of the PLGA-mPEG nanoparticles. This may be associated with the effects of the mPEG/PLGA ratio on the density of PEG on the surface of the nanoparticles and on the size of the nanoparticles.

Comparison of resorbable poly-L-lactic acid-polyglycolic acid and internal Palmaz stents for the surgical correction of severe tracheomalacia

Tracheomalacia (TM) is associated with expiratory airway collapse and potentially fatal respiratory distress. Internal and external tracheal stents and, recently, resorbable biopolymers have been used to treat this condition. In this study, the efficacy and biocompatibility of internal Palmaz stents and external poly-L-lactic acid-polyglycolic acid (PLPG) stents were compared in a model of severe TM induced in piglets. The tracheas were repaired with one of two stenting methods, and the animals survived for up to 16 weeks. Weight gain, adverse respiratory signs and symptoms, tracheal or lung histopathologic changes, and internal and external tracheal diameters were measured. The animals in the PLPG group uniformly were free of respiratory distress and tracheal stenosis or inflammation, whereas all animals in the Palmaz group developed respiratory distress as a result of pneumonia or tracheal stenosis caused by intraluminal granulation tissue. In conclusion, superior efficacy of external, resorbable PLPG stents was found relative to internal Palmaz stents for the surgical repair of severe TM.

Double walled POE/PLGA microspheres: encapsulation of water-soluble and water-insoluble proteins and their release properties

The poly(orthoester) (POE)-poly(D,L-lactide-co-glycolide) (50:50) (PLGA) double-walled microspheres with 50% POE in weight were loaded with hydrophilic bovine serum albumin (BSA) and hydrophobic cyclosporin A (CyA). Most of the BSA and CyA was entrapped within the shell and core, respectively, because of the difference in their hydrophilicity. The morphologies and release mechanisms of proteins-loaded double-walled POE/PLGA microspheres were investigated. Scanning electron microscope studies revealed that the CyA-BSA-loaded double-walled POE/PLGA microspheres yielded a more porous surface and PLGA shell than those without BSA. The neat POE and PLGA yielded slow and incomplete CyA and BSA release. In contrast, nearly complete BSA and more than 95% CyA were released in a sustained manner from the double-walled POE/PLGA microspheres. Both the BSA- and CyA-BSA-loaded POE/PLGA microspheres yielded a sustained BSA release over 5 days. The CyA release pattern of the CyA-loaded double-walled POE/PLGA microspheres was biphasic, characterized by a slow release over 15 days followed by a sustained release over 27 days. However, the CyA-BSA-loaded double-walled POE/PLGA microspheres provided a more constant and faster CyA release due to their more porous shell. In the CyA-BSA-loaded double-walled POE/PLGA microspheres system, the PLGA layer acted as a carrier for BSA and mild reservoir for CyA. During the first 5 days, most BSA was released from the shell but only 14% CyA was left from the microspheres. Subsequently, more than 80% CyA were released in the next 25 days. The distinct structure of double-walled POE/PLGA microspheres would make an interesting device for controlled delivery of therapeutic agents.

Biodegradable micro- and nanoparticles as long-term delivery vehicles for interferon-alpha

The development of new interferon-alpha (IFN-alpha) delivery strategies is a key issue in order to simplify its administration and improve its therapeutic effects, while reducing its dose-related side effects. One of the most attractive approaches towards this aim is the encapsulation of IFN-alpha into poly(lactic-glycolic acid) (PLGA) microspheres. Nevertheless, the stability of IFN-alpha released from these microspheres has been identified as one of the most important concerns in relation to the potential of this approach. Being conscious of this problem, we have used new strategies for the encapsulation of IFN-alpha into biodegradable micro- and nanoparticles. We chose poloxamer 188 as a stabilizing agent and encapsulated IFN-alpha within PLGA/poloxamer blend microspheres prepared by an oil-in-oil solvent extraction technique and also within PLGA micro- and nanospheres containing poloxamer, prepared by the water-in-oil-in-water solvent evaporation technique. The results showed that these techniques led to the efficient encapsulation of IFN-alpha and the modulation of their particle size, ranging from nanospheres (280 nm) to 40 microm-microspheres. These systems exhibit a similar pattern of release that is characterized by an initial burst (2-24% IFN-alpha released, as determined by ELISA) followed by small pulses of immunoenzymatically detected IFN-alpha for up to 1 month. The maintenance of the structural integrity and bioactivity of the protein was confirmed using a cytostasis bioassay. The results showed that the antiproliferative activity of the IFN-alpha varied depending on the formulation. More specifically, PLGA/poloxamer blend microspheres were able to provide significant amounts of active IFN-alpha for up to 96 days. This new IFN-alpha delivery system opens up possibilities to improve present IFN-alpha-based therapies.

Periodontal delivery of ipriflavone: new chitosan/PLGA film delivery system for a lipophilic drug

The aim of the present work was to design a film dosage form for sustained delivery of ipriflavone into the periodontal pocket. For this purpose, monolayer composite systems made of ipriflavone loaded poly(D,L-lactide-co-glycolide) (PLGA) micromatrices in a chitosan film form, were obtained by emulsification/casting/evaporation technique. Multilayer films, made of three layers of polymers (chitosan/PLGA/chitosan), were also prepared and compared to monolayer films for their "in vitro" characteristics. Morphology and physico-chemical properties of the different systems were evaluated. The influence of pH, ionic strength and enzymatic activity on film degradation, was also investigated. Significant differences in swelling, degradation and drug release were highlighted, depending on film structure and composition. In vitro experiments demonstrated that the composite micromatricial films represent a suitable dosage form to prolong ipriflavone release for 20 days.

The effect of CTAB concentration in cationic PLG microparticles on DNA adsorption and in vivo performance

PURPOSE

Cationic PLG microparticles with adsorbed DNA have previously been shown to efficiently target antigen presenting cells in vivo for generating higher immune responses in comparison to naked DNA. In this study we tried to establish the role of surfactant (CTAB) concentration on the physical behavior of these formulations.

METHODS

Cationic PLG microparticle formulations with adsorbed DNA were prepared using a solvent evaporation technique. Formulations with varying CTAB concentrations and a fixed DNA load were prepared. The loading efficiency and 24 h DNA release was evaluated for each formulation. Select formulations were tested in vivo.

RESULTS

Higher CTAB concentration correlated with higher DNA binding efficiency on the microparticles and lower in vitro release rates. Surprisingly though, the in vivo performance of formulations with varying CTAB concentration was comparable to one another.

CONCLUSIONS

Cationic PLG microparticles with adsorbed DNA, as described here, offer a robust way of enhancing in vivo responses to plasmid DNA.

Dynamics of endocytosis and exocytosis of poly(D,L-lactide-co-glycolide) nanoparticles in vascular smooth muscle cells

PURPOSE

The purpose of this work was to characterize the process of endocytosis, exocytosis, and intracellular retention of poly (D,L-lactide-co-glycolide) nanoparticles in vitro using human arterial vascular smooth muscle cells (VSMCs).

METHODS

Nanoparticles containing bovine serum albumin (BSA) as a model protein and 6-coumarin as a fluorescent marker were formulated by a double emulsion-solvent evaporation technique. The endocytosis and exocytosis of nanoparticles in VSMCs were studied using confocal microscopy and their intracellular uptake and retention were determined quantitatively using high-performance liquid chromatography.

RESULTS

Cellular uptake of nanoparticles (mean particle size 97 +/- 3 nm) was a concentration-, time-, and energy-dependent endocytic process. Confocal microscopy demonstrated that nanoparticles were internalized rapidly, with nanoparticles seen inside the cells as early as within 1 min after incubation. The nanoparticle uptake increased with incubation time in the presence of nanoparticles in the medium; however, once the extracellular nanoparticle concentration gradient was removed, exocytosis of nanoparticles occurred with about 65% of the internalized fraction undergoing exocytosis in 30 min. Exocytosis of nanoparticles was slower than the exocytosis of a fluid phase marker, Lucifer yellow. Furthermore, the exocytosis of nanoparticles was reduced after the treatment of cells with the combination of sodium azide and deoxyglucose, suggesting that exocytosis of nanopartides is an energy-dependent process. The nanoparticle retention increased with increasing nanoparticle dose in the medium but the effect was relatively less significant with the increase in incubation time. Interestingly, the exocytosis of nanoparticles was almost completely inhibited when the medium was depleted of serum. Further studies suggest that the addition of BSA in the serum free medium with or without platelet derived growth factor (PDGF) induced exocytosis of nanoparticles. The above result suggests that the protein in the medium is either adsorbed onto nanoparticles and/or carried along with nanoparticles inside the cells, which probably interacts with the exocytic pathway and leads to greater exocytosis of nanoparticles.

CONCLUSIONS

The study demonstrated that endocytosis and exocytosis of nanoparticles are dynamic and energy-dependent processes. Better understanding of the mechanisms of endocytosis and exocytosis, studies determining the effect of nanoparticle formulation and composition that may affect both the processes, and characterization of intracellular distribution of nanoparticles with surface modifications would be useful in exploring nanoparticles for intracellular delivery of therapeutic agents.

BCNU-loaded poly(D, L-lactide-co-glycolide) wafer and antitumor activity against XF-498 human CNS tumor cells in vitro

Implantable polymeric device that can release chemotherapeutic agent directly into central nervous system (CNS) has had an impact on malignant glioma therapy. The purpose of our study was to develop an implantable polymeric device, which can release intact 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) for long-term period over 1 month, and to evaluate its cytotoxicity against XF 498 human CNS tumor cells in vitro. BCNU was incorporated into biodegradable poly(D,L-lactide-co-glycolide) (PLGA), by using spray-drying method. BCNU-loaded PLGA microparticles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction, and differential scanning calorimetry. SEM observation of the microparticles showed that the microparticles were spherical, i.e. microspheres. Homogeneous distribution of BCNU in PLGA microsphere was confirmed by significant reduction of crystallinity of BCNU. Microspheres were fabricated into wafers with flat and smooth surface by direct compression method. In vitro release of BCNU in pH 7.4 phosphate buffered saline was prolonged up to 8 weeks after short initial burst period. Antitumor activity of BCNU-loaded PLGA wafer against XF 498 human CNS tumor cells continued over 1 month and, PLGA only did not affect the growth of the cells. Meanwhile, the cytotoxic activity of BCNU powder disappeared within 12 h. These results strongly suggest that the BCNU/PLGA formulations increase release period of carmustine in vivo and also be useful in the development of implantable polymeric device for malignant glioma.

Preparation of a copoly (dl-lactic/glycolic acid)-zinc oxide complex and its utilization to microcapsules containing recombinant human growth hormone

A procedure to prepare a complex of copoly (dl-lactic/glycolic acid) and zinc oxide (PLGA-zinc oxide complex) was developed. Out of sparingly water-soluble zinc compounds, zinc oxide was most remarkably soluble in a PLGA/dichloromethane solution and the dissolution rates became faster as the water contents in the PLGA/dichloromethane solutions increased. Since the solubility of zinc oxide was saturated at approximately 0.5-fold molar ratio to PLGA and water was generated with dissolution of zinc oxide in the PLGA/dichloromethane solutions, it is suggested that zinc oxide interacts with the terminal carboxyl group of PLGA. In addition, the glass-transition temperature of a solid material obtained by vacuum-drying the PLGA/dichloromethane solution dissolving zinc oxide became higher as the zinc content increased, suggesting that the formation of a PLGA-zinc oxide complex. Microcapsules were prepared with the PLGA-zinc oxide complex using recombinant human growth hormone (rhGH) in order to evaluate an effect of the complex on protein release and stability of protein in the microcapsules. Released rhGH amount from the microcapsules prepared with the PLGA-zinc oxide complex after subcutaneous administration in rats was significantly larger than that from microcapsules prepared with PLGA alone, indicating that rhGH molecules in the microcapsules was stabilized by the PLGA-zinc oxide complex.

Feeding liquid, non-ionic surfactant and cyclodextrin affect the properties of insulin-loaded poly(lactide-co-glycolide) microspheres prepared by spray-drying

The potential of spray-drying technique for the encapsulation in poly(lactide-co-glycolide) (PLGA) microspheres of bovine insulin, a poorly stable peptide, has been investigated. Insulin-loaded microspheres were prepared by spray-drying different feeding liquids containing insulin and PLGA, that is a S/O dispersion, a W/O emulsion or an acetic acid solution. In the case of the emulsion, insulin was also co-encapsulated with either non-ionic surfactants such as polysorbate 20 and poloxamer 188, or complexing agents such as HPbetaCD. In the microspheres prepared from the acetic acid solution of insulin and PLGA, HPbetaCD was tested. Microspheres containing surfactants were aggregated, whereas good quality particles displaying a mean diameter in the range 12.1-27.9 microm were produced in the other cases. Insulin was efficiently loaded inside microspheres except for S/O formulation (only 22% of total insulin content was entrapped). The impact of the microencapsulation process on insulin chemical and conformational stability was assessed by HPLC, circular dichroism and turbidimetry studies. Under the adopted manufacture conditions, insulin was encapsulated in the native state and its chemical and conformational stability was preserved along the fabrication process. The formulations containing only insulin displayed low burst effects (6-11%), whereas the addition of surfactants resulted in much higher burst effects (49-54%) and faster release rate. The co-encapsulation of HPbetaCD slowed down the overall release rate and, in the case of microspheres prepared from the emulsion, allowed a constant insulin release up to 45 days. The study of insulin stability along the release phase showed that insulin was released in the intact form and un-released insulin was stable inside all the microsphere formulations. We conclude that insulin can be effectively encapsulated in PLGA microspheres by the spray-drying technique. Additives with complexing properties such as HPbetaCD have demonstrated a potential in optimizing the release rate of insulin when used in microspheres prepared from W/O emulsions.

A novel controlled release formulation for the anticancer drug paclitaxel (Taxol): PLGA nanoparticles containing vitamin E TPGS

Paclitaxel (Taxol) is one of the best antineoplastic drugs found from nature in the past decades. Like many other anticancer drugs, there are difficulties in its clinical administration due to its poor solubility. Therefore an adjuvant called Cremophor EL has to be employed, but this has been found to cause serious side-effects. However, nanoparticles of biodegradable polymers can provide an ideal solution to the adjuvant problem and realise a controlled and targeted delivery of the drug with better efficacy and fewer side-effects. The present research proposes a novel formulation for fabrication of nanoparticles of biodegradable polymers containing d-alpha-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS or TPGS) to replace the current method of clinical administration and, with further modification, to provide an innovative solution for oral chemotherapy. In the modified solvent extraction/evaporation technique employed in this research, the emulsifier/stabiliser/additive and the matrix material can play a key role in determining the morphological, physicochemical and pharmaceutical properties of the produced nanoparticles. We found that vitamin E TPGS could be a novel surfactant as well as a matrix material when blended with other biodegradable polymers. The nanoparticles composed of various formulations and manufactured under various conditions were characterised by laser light scattering (LLS) for size and size distribution, scanning electron microscopy (SEM) and atomic force microscopy (AFM) for morphological properties, X-ray photoelectron spectroscopy (XPS) for surface chemistry and differential scanning calorimetry (DSC) for thermogram properties. The drug encapsulation efficiency (EE) and the drug release kinetics under in vitro conditions were measured by high performance liquid chromatography (HPLC). It was concluded that vitamin E TPGS has great advantages for the manufacture of polymeric nanoparticles for controlled release of paclitaxel and other anti-cancer drugs. Nanoparticles of nanometer size with narrow distribution can be obtained. A drug encapsulation efficiency as high as 100% can be achieved and the release kinetics can be controlled.

Loading of plasmid DNA into PLGA microparticles using TROMS (Total Recirculation One-Machine System): evaluation of its integrity and controlled release properties

Loading plasmid DNA into poly(ester) microparticles usually involves the formation of a multiple emulsion, using homogenisation techniques such as sonication or Ultra-Turrax. These procedures may negatively affect the integrity of the macromolecule and consequently its activity. The aim of this study was to prepare and evaluate DNA-loaded microparticles by TROMS (Total Recirculation One-Machine System), a new procedure that is based on the formation of a multiple emulsion by the injection of the phases under a turbulent regime. Microparticles were prepared with either Resomer) RG 502 (MP 502) or RG 756 (MP 756) and DNA loading was quantified fluorimetrically. DNA loading in MP 756 was almost twice as high as in MP 502 (510 vs. 285 ng/mg, respectively). Under both formulations, the loaded plasmid was released while maintaining its integrity for at least 24 days (MP 502) and 40 days (MP 756). Finally, the transfection efficiency was studied after injection of the microparticles (MP 502) into rat skeletal muscle and compared with naked DNA injection. Injection of naked DNA (150 microg DNA per muscle) achieved higher but variable expression levels that decreased after 3 weeks. In contrast, the muscles injected with microparticles (6.8 microg DNA per muscle) showed lower but homogeneous expression values, which were maintained for at least 3 weeks.

Microencapsulation of low molecular weight heparin into polymeric particles designed with biodegradable and nonbiodegradable polycationic polymers

Owing to its lack of oral absorption, heparin has to be administered parenterally. However, parental administration has negative aspects such as multiple injections, possible infection, patient inconvenience, and high cost. Now, low molecular weight heparin (LMWH) is taking part in antithrombotic treatment and is proven to confer more advantages than unfractionated heparin. The aim of our present study was to formulate, by the w/o/w emulsification process, LMWH microparticles as potential oral carriers prepared with biodegradable (poly-epsilon-caprolactone and poly-lactic-co-glycolic acid) and nonbiodegradable polycationic polymers (Eudragit RS and RL), used alone or blended. The encapsulation efficiency ranged from 16 to 47% and was highly dependent on the presence of the positively charged polymers. In the same way, a low in vitro LMWH release was observed when Eudragit polymers composed totally or partially the polymeric matrix, compared with biodegradable polymers exhibiting higher LMWH release (40 and 60%). For each formulation, LMWH released from microparticles preserved its biological activity as shown by the antifactor Xa activity. Experiments performed with fluorescein-labeled LMWH showed the drug distribution in microparticles and may give information about the mechanisms controlling LMWH encapsulation and release.

Potential applications of PLGA film-implants in modulating in vitro drugs release

In this work we evaluate poly(lactic/glycolic) acid (PLGA) film-implants as potential biodegradable devices for controlled release of two different drugs: 5-Fluorouridine (5-FUR), a conventional low molecular weight water-soluble compound and SPf66 malaria vaccine, a therapeutic synthetic polypeptide. Three types of devices were prepared by solvent-casting techniques alone or combined with compression method: simple monolithic discs (SMD), multilayer discs with a central monolithic layer (MLDM), and multilayer discs with a central drug-reservoir (MLDR). For the highly water-soluble drug, 5-FUR, in vitro release from SMD showed an initial burst (24% in 2 h) followed by prolonged release over 20 days. In contrast, from a MLDM (two drug-free PLGA discs were added to the SMD) showed an initial lag-time of 12 days followed by a very fast second release phase. Finally, when the load of this system was increased from 3 to 9%, an extended release over 20 days with a low burst effect was obtained. For SPf66, the central reservoir containing the synthetic polypeptide MLDR reduces the possibility of degradation due to peptide contact with polymer solution. When four layers were added, 10 days sustained-release was obtained without any burst effect. With six layers a moderate pulse was obtained, 18-22 days from the beginning of the release. The results show the suitability of the proposed devices to control release and avoid the burst effect with highly water-soluble drugs; as well as modulate in vitro peptide release.

Preservation of lysozyme structure and function upon encapsulation and release from poly(lactic-co-glycolic) acid microspheres prepared by the water-in-oil-in-water method

When proteins are encapsulated in bioerodible polymers by water-in-oil-in-water (w/o/w) encapsulation techniques, inactivation and aggregation are serious drawbacks hampering their sustained delivery. Hen egg-white lysozyme was employed to investigate whether stabilizing it towards the major stress factors in the w/o/w encapsulation procedure would allow for the encapsulation and release of structurally unperturbed, non-aggregated, and active protein. When it was encapsulated in poly(lactic-co-glycolic) acid (PLGA) microspheres without stabilizing additives, lysozyme showed substantial loss in activity and aggregation. It has been shown that by co-dissolving various sugars and polyhydric alcohols with lysozyme in the first aqueous buffer, interface-induced lysozyme aggregation and inactivation can be minimized in the first emulsification step [J. Pharm. Pharmacol. 53 (2001) 1217]. Herein, it was found that those excipients, which were efficient in preventing interface-induced structural perturbations, were also efficient in minimizing lyophilization-induced structural perturbations (e.g. lactulose). The efficient excipients identified also reduced structural perturbations upon lysozyme encapsulation in PLGA microspheres and this led to reduced lysozyme inactivation and aggregation. However, the data obtained also show that later steps in the encapsulation procedure are detrimental to lysozyme activity. Lysozyme inactivation was completely prevented only by employing the efficient excipients in the second aqueous phase also. In summary, protein aggregation and inactivation were minimized by rationally selecting excipients efficient in stabilizing lysozyme against the major stress factors of w/o/w encapsulation.