Investigation on process parameters involved in preparation of poly-DL-lactide-poly(ethylene glycol) microspheres containing Leptospira Interrogans antigens

Initial Formation of the Skin Layer of PLGA Microparticles

Poly(lactide-co-glycolide) (PLGA) has been extensively used in making long-acting injectable formulations. The critical factors affecting the PLGA formulation properties have been adjusted to control the drug release kinetics and obtain desirable properties of PLGA-based drug delivery systems. The PLGA microparticle formation begins as soon as the drug/PLGA-dissolved in the organic solvent phase (oil phase) is exposed to the water phase. The initial skin (or shell) formation on the oil droplets occurs very quickly, sometimes in the matter of milliseconds, and studying the process has been difficult. The skin formation on the PLGA emulsion droplet surface that can affect the subsequent hardening steps is examined. PLGA droplets with different compositions are prepared. Using collimated light and a high-speed camera made it possible to detect the diffusion of acetonitrile from the oil phase into the water phase during the oil droplet formation. Although the skin formation is not visible on the surface of the oil phase droplet with the current setup, the droplet shapes, solid strand formation, and the difference in the spreading time suggest that the initial contact time between the oil and water phases in the range of a few seconds is critical to the properties of the skin.

Synthesis and Characterization of Polyfumarateurethane Nanoparticles for Sustained Release of Bupivacaine

Biodegradable polyfumarateurethane (PFU) for use as a bupivacaine delivery vehicle, synthesized using di-(2-hydroxypropyl fumarate) (DHPF), polyethylene glycol (PEG) and 1,6-hexamethylene diisocyanate (HMDI), was designed to be degradable through the hydrolysis and enzymatic degradation of the ester bonds in its polymer backbone. Using a water-in-oil-in-water double emulsion techniques, nanoparticles encapsulating water or fluorescein isothiocyanate (FITC) were fabricated to avoid the immune system owing to the presence of PEG on their surface. The morphologies of these nanoparticles were characterized by DLS, TEM, FE-SEM, and fluorescent microscopies. The present study explored the encapsulation, loading efficiency and in vitro drug release of bupivacaine encapsulated with biodegradable PFU nanoparticles for the treatment of local anesthesia. Various concentrations of bupivacaine were encapsulated into nanoparticles and their encapsulation efficiencies and drug loading were investigated. Encapsulation efficiency was highest when 2.5% bupivacaine was encapsulated. Drug release behavior from the bupivacaine-loaded PFU nanoparticles followed a sustained release profile.

Improved Stability of Rifampicin in the Presence of Gastric-Resistant Isoniazid Microspheres in Acidic Media

The degradation of rifampicin (RIF) in an acidic medium to form 3-formyl rifamycin SV, a poorly absorbed compound, is accelerated in the presence of isoniazid, contributing to the poor bioavailability of rifampicin. This manuscript presents a novel approach in which isoniazid is formulated into gastric-resistant sustained-release microspheres and RIF into microporous floating sustained-release microspheres to reduce the potential for interaction between RIF and isoniazid (INH) in an acidic environment. Hydroxypropyl methylcellulose acetate succinate and Eudragit^® L100 polymers were used for the manufacture of isoniazid-loaded gastric-resistant sustained-release microspheres using an o/o solvent emulsification evaporation approach. Microporous floating sustained-release microspheres for the delivery of rifampicin in the stomach were manufactured using emulsification and a diffusion/evaporation process. The design of experiments was used to evaluate the impact of input variables on predefined responses or quality attributes of the microspheres. The percent degradation of rifampicin following 12 h dissolution testing in 0.1 M HCl pH 1.2 in the presence of isoniazid gastric-resistant sustained-release microspheres was only 4.44%. These results indicate that the degradation of rifampicin in the presence of isoniazid in acidic media can be reduced by encapsulation of both active pharmaceutical ingredients to ensure release in different segments of the gastrointestinal tract, potentially improving the bioavailability of rifampicin.

Preparation of Chitosan Microcapsules Containing Red Ginger Oleoresin Using Emulsion Crosslinking Method

BACKGROUND:

Encapsulation is one of the methods used to trap active ingredients in the wall material of microparticles.

AIM:

The aim of this study was to evaluate the encapsulation of red ginger oleoresin using an emulsion crosslinking method with chitosan as the wall material.

METHODS:

Emulsions were formed of red ginger oleoresin with chitosan in concentrations of 1%, 2%, 3%, and 4% (w/v), respectively. The emulsions were then mixed with corn oil and stirred for one hour to obtain a second set of emulsions, and glutaraldehyde saturated toluene (GST) was added dropwise in quantities of 20, 10, 6.7, and 5 ml, respectively. This was followed by the addition of 2 ml of 25% glutaraldehyde and the emulsions were stirred for two hours. The resulting microcapsules were washed with petroleum ether followed by hexane and then dried in an oven at 70oC.

RESULTS:

The emulsion crosslinking method used to trap the red ginger oleoresin in chitosan produced microcapsules of good spherical geometry with the mean diameter ranging from 75.61 ± 11.8 µm to 178.65 ± 40.7 µm. The highest yield was 98.93% and encapsulation efficiency was 83.1%. Thermogravimetric and differential thermal analysis showed that the melting point was at a temperature between 120 and 130oC.

CONCLUSION:

Chitosan concentration has little effect on encapsulation yield, whereas the amount of GST tends to strengthen the crosslinking bonds of chitosan and reduces the mean diameter of microspheres.

Lymph Node-Targeting Nanovaccine through Antigen-CpG Self-Assembly Potentiates Cytotoxic T Cell Activation

Therapeutic vaccines that arouse the cytotoxic T cell immune response to reject infected cells have been investigated extensively for treating disease. Due to the large amounts of resident antigen-presenting cells (APCs) and T cells in lymph nodes, great efforts have been made to explore the strategy of targeting lymph nodes directly with nanovaccines to activate T cells. However, these nanovaccines still have several problems, such as a low loading efficiency and compromised activity of antigens and adjuvants derived from traditional complicated preparation. There are also safety concerns about materials synthesized without FDA approval. Herein, we construct an assembled nanoparticle composed of an antigen (ovalbumin, OVA) and adjuvant (CpG) to ensure its safety and high loading efficiency. The activity of both components was well preserved due to the mild self-assembly process. The small size, narrow distribution, negative charge, and good stability of the nanoparticle endow these nanovaccines with superior capacity for lymph node targeting. Correspondingly, the accumulation at lymph nodes can be improved by 10-fold. Subsequently, due to the sufficient APC internalization and maturation in lymph nodes, ~60% of T cells are stimulated to proliferate and over 70% of target cells are specifically killed. Based on the effective and quick cellular immune response, the assembled nanoparticles exhibit great potential as therapeutic vaccines.

Thermoresponsive curcumin/DsiRNA nanoparticle gels for the treatment of diabetic wounds: synthesis and drug release

AIM

Chitosan (CS) has been extensively studied as drug delivery systems for wound healing. Results/methodology: CS nanoparticles were loaded with curcumin (Cur) and DsiRNA against prostaglandin transporter gene and they were incorporated into 20 and 25% w/v Pluronic F-127. The gels were later analyzed for their rheology, gelation temperature (T_gel), morphology, drug incorporation and in vitro drug release. The particle size was in the range of 231 ± 17-320 ± 20 nm, depending on CS concentration. The gels had T_gel of 23-28°C and exhibited sustained drug release with high accumulated amount of drugs over 48 h.

CONCLUSION

A thermo-sensitive gel containing Cur/DsiRNA CS nanoparticles was successfully developed and has a great potential to be further developed.

Passive targeting and lung tolerability of enoxaparin microspheres for a sustained antithrombotic activity in rats

Pulmonary bed can retain microparticles (MP) larger than their capillaries' diameter, hence we offer a promising way for lung passive targeting following intravenous (IV) administration. In this study, enoxaparin (Enox)-albumin microspheres (Enox-Alb MS) were, optimally, developed as lung targeted sustained release MP for IV use. Lung tolerability and targeting efficiency of Enox-Alb MS were tested, and the pharmacokinetic profile following IV administration to albino rats was constructed. In vivo studies confirmed high lung targeting efficiency of Enox-Alb MS with lack of potential tissue toxicity. The anticoagulant activity of the selected Alb MS was significantly sustained for up to 38 h compared to 5 h for the market product. Alb MS are promising delivery carriers for controlled and targeted delivery of Enox to the lungs for prophylaxis and treatment of pulmonary embolism.

Nano-encapsulation of a novel anti-Ran-GTPase peptide for blockade of regulator of chromosome condensation 1 (RCC1) function in MDA-MB-231 breast cancer cells

Ran is a small ras-related GTPase and is highly expressed in aggressive breast carcinoma. Overexpression induces malignant transformation and drives metastatic growth. We have designed a novel series of anti-Ran-GTPase peptides, which prevents Ran hydrolysis and activation, and although they display effectiveness in silico, peptide activity is suboptimal in vitro due to reduced bioavailability and poor delivery. To overcome this drawback, we delivered an anti-Ran-GTPase peptide using encapsulation in PLGA-based nanoparticles (NP). Formulation variables within a double emulsion solvent evaporation technique were controlled to optimise physicochemical properties. NP were spherical and negatively charged with a mean diameter of 182-277nm. Peptide integrity and stability were maintained after encapsulation and release kinetics followed a sustained profile. We were interested in the relationship between cellular uptake and poly(ethylene glycol) (PEG) in the NP matrix, with results showing enhanced in vitro uptake with increasing PEG content. Peptide-loaded, pegylated (10% PEG)-PLGA NP induced significant cytotoxic and apoptotic effects in MDA-MB-231 breast cancer cells, with no evidence of similar effects in cells pulsed with free peptide. Western blot analysis showed that encapsulated peptide interfered with the proposed signal transduction pathway of the Ran gene. Our novel blockade peptide prevented Ran activation by blockage of regulator of chromosome condensation 1 (RCC1) following peptide release directly in the cytoplasm once endocytosis of the peptide-loaded nanoparticle has occurred. RCC1 blockage was effective only when a nanoparticulate delivery approach was adopted.

A microreactor-based continuous process for controlled synthesis of poly-methyl-methacrylate-methacrylic acid (PMMA) nanoparticles

We have developed a microreactor-based continuous process for synthesizing PMMA nanoparticles (NPs), based on the principle of nanoprecipitation.

Preparation and in vivo evaluation of insulin-loaded biodegradable nanoparticles prepared from diblock copolymers of PLGA and PEG

The aim of this study was to design a controlled release vehicle for insulin to preserve its stability and biological activity during fabrication and release. A modified, double emulsion, solvent evaporation, technique using homogenisation force optimised entrapment efficiency of insulin into biodegradable nanoparticles (NP) prepared from poly (DL-lactic-co-glycolic acid) (PLGA) and its PEGylated diblock copolymers. Formulation parameters (type of polymer and its concentration, stabiliser concentration and volume of internal aqueous phase) and physicochemical characteristics (size, zeta potential, encapsulation efficiency, in vitro release profiles and in vitro stability) were investigated. In vivo insulin sensitivity was tested by diet-induced type II diabetic mice. Bioactivity of insulin was studied using Swiss TO mice with streptozotocin-induced type I diabetic profile. Insulin-loaded NP were spherical and negatively charged with an average diameter of 200-400 nm. Insulin encapsulation efficiency increased significantly with increasing ratio of co-polymeric PEG. The internal aqueous phase volume had a significant impact on encapsulation efficiency, initial burst release and NP size. Optimised insulin NP formulated from 10% PEG-PLGA retained insulin integrity in vitro, insulin sensitivity in vivo and induced a sustained hypoglycaemic effect from 3h to 6 days in type I diabetic mice.

Revisiting the nanoformulation design approach for effective delivery of topotecan in its stable form: an appraisal of its in vitro Behavior and tumor amelioration potential

Topotecan (TPT) is indicated against a variety of solid tumors, but has restricted clinical use owing to associated pharmaceutical caveats. This study is focused at formulating a successful TPT PLGA nanosystem which ameliorates the rapid conversion of active lactone form of drug to its inactive carboxylate form and consequently improvises its efficacy. TPT PLGA nanoparticles were formulated by a double emulsion-solvent evaporation technique with sequential optimization to obtain desired particle size, PDI, zeta potential, and entrapment efficiency. Stability of TPT was ensured by maintaining an acidic pH in the drug-containing phase and the system was evaluated for in vitro-in vivo performance including cytotoxic potency. The optimized nanosystem had a particle size of 187.33 ± 7.50 nm, a PDI of 0.179 ± 0.05, and an entrapment efficiency of 56 ± 1.2%. Low pH in the interior of nanoparticles stabilized the drug to remain in its active lactone form and revealed a biphasic release pattern till 15 d. Additionally, an in vitro cytotoxicity testing as well as in vivo antitumor efficacy demonstrated a significant potential of higher proliferation inhibition as compared with neat drug (TPT). Thus, the investigation summarized an innovative simple tool for developing stable TPT NPs for effective delivery for treating solid tumors.

The use of solid lipid nanoparticles for sustained drug release

Novel solid lipid drug delivery systems such as solid lipid nanoparticles (SLN) have attracted wide and increasing attention in recent years. It has been sought as an interesting alternative drug delivery carrier system for bioactives for a variety of delivery routes. They show major advantages such as sustained release, improved bioavailability, improved drug incorporation and very wide application. This paper presents a discussion on the production protocols of SLN, lyophilization of SLN and delivery of SLN across the blood–brain barrier. Special attention was also paid to entrapment and release of drugs from SLN and strategies to enhance drug entrapment in SLN for sustained release. Analytical methods for the characterization of SLN were also discussed. Various routes of administration of SLN were presented as well as a consideration of the ethical issues and future prospects in the production and use of SLN for sustained release of bioactives.

Synthesis and in vitro evaluation of melatonin entrapped PLA nanoparticles: an oxidative stress and T-cell response using golden hamster

This study was carried out to evaluate the effects of melatonin entrapped PLA nanoparticles (Mel-NPs) and pure Mel on impact of reactive oxygen species (ROS), blastogenic responses (%SR) in terms of proliferation of splenocytes. ROS have been proposed to play an important role in balancing the pro- and antioxidant homeostasis during different physiological condition of organism. Melatonin has been suggested as an effective free radical scavenger that may have an important role during this process. Mel-NPs were prepared by using emulsification (o/w) nanoprecipitation method and their physicochemical characterizations were studied for evaluation of particle size and encapsulation efficiency by using SEM, TEM, particle size analyzer, DSC and FTIR. The TEM micrograph showed excellent findings regarding size, shape, encapsulation efficiency and difference between pure PLA nanoparticles and Mel-NPs. The SEM micrographs of Mel-NPs showed spherical shape, smooth surfaces and the homogeneous particle size distribution. In TEM micrograph, the average diameter of Mel-NPs was found to be 36 ± 8 nm with ∼78% (w/w) of entrapment efficiency. The size of pure PLA nanoparticles was found to be larger as compared to Mel-NPs which confirm that the drug supports the reduction of the size of Mel-NPs. In in vitro study, we observed that Mel-NPs significantly reduce the level of ROS in splenocytes and increased the level %SR at 96 h of splenocytes culture as compared to the culture with pure Mel. Thus our results propose high clinical value for improvement of depressed immunity by Mel-NPs.

Optimization of the process parameters for the fabrication of a polymer coated layered double hydroxide-methotrexate nanohybrid for the possible treatment of osteosarcoma

The study demonstrates the method of optimization for the development of PLGA encapsulated LDH-MTX, MTX and their in vitro and in vivo evaluation.

Bovine serum albumin adsorbed PGA-co-PDL nanocarriers for vaccine delivery via dry powder inhalation

PURPOSE

Dry powder vaccine delivery via the pulmonary route has gained significant attention as an alternate route to parenteral delivery. In this study, we investigated bovine serum albumin (BSA) adsorbed poly(glycerol adipate-co-ω-pentadecalactone), PGA-co-PDL polymeric nanoparticles (NPs) within L-leucine (L-leu) microcarriers for dry powder inhalation.

METHODS

NPs were prepared by oil-in-water single emulsion-solvent evaporation and particle size optimised using Taguchi's design of experiment. BSA was adsorbed onto NPs at different ratios at room temperature. The NPs were spray-dried in aqueous suspension of L-leu (1:1.5) using a Büchi-290 mini-spray dryer. The resultant nanocomposite microparticles (NCMPs) were characterised for toxicity (MTT assay), aerosolization (Next Generation Impactor), in vitro release study and BSA was characterized using SDS-PAGE and CD respectively.

RESULTS

NPs of size 128.50 ± 6.57 nm, PDI 0.07 ± 0.03 suitable for targeting lung dendritic cells were produced. BSA adsorption for 1 h resulted in 10.23 ± 1.87 μg of protein per mg of NPs. Spray-drying with L-leu resulted in NCMPs with 42.35 ± 3.17% yield. In vitro release study at 37°C showed an initial burst release of 30.15 ± 2.33% with 95.15 ± 1.08% over 48 h. Aerosolization studies indicated fine particle fraction (FPF%) dae < 4.46 μm as 76.95 ± 5.61% and mass median aerodynamic diameter (MMAD) of 1.21 ± 0.67 μm. The cell viability was 87.01 ± 14.11% (A549 cell line) and 106.04 ± 21.14% (16HBE14o- cell line) with L-leu based NCMPs at 1.25 mg/ml concentration after 24 h treatment. The SDS-PAGE and CD confirmed the primary and secondary structure of the released BSA.

CONCLUSIONS

The results suggest that PGA-co-PDL/L-leu NCMPs may be a promising carrier for pulmonary vaccine delivery due to excellent BSA adsorption and aerosolization behaviour.

Impact of surfactant selection on the formulation and characterization of microparticles for pulmonary drug delivery

The effect of suspension stabilizers, internal aqueous phase volume and polymer amount were investigated for the production of protein loaded poly(d,l lactide-co-glycolide) (PLGA) microparticles suitable for pulmonary drug delivery. PLGA microparticles were produced adopting water-in-oil-in-water (W/O/W) solvent evaporation technique and were investigated for surface morphology, particle size, encapsulation efficiency (EE%) and in-vitro release profile. Porous surface morphologies with a narrow size distribution were observed when employing 0.5 ml internal aqueous phase; 23.04 µm (± 0.98), 15.05 µm (± 0.27) and 22.89 µm (±0.41) for PVA, Tween 80 and oleic acid. Porous microparticles exhibited increased size and reduction in EE% with increasing internal aqueous phase, with non-porous microparticles produced when adopting 2.0 ml internal aqueous phase. The selection of stabilizer influences the size of the pores formed thus offers potential for the aerodynamic properties of the microparticles to be manipulated to achieve suitable aerosolization characteristics for pulmonary delivery of proteins.

Microcosmic mechanisms for protein incomplete release and stability of various amphiphilic mPEG-PLA microspheres

The microcosmic mechanisms of protein (recombinant human growth hormone, rhGH) incomplete release and stability from amphiphilic poly(monomethoxypolyethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA) microspheres were investigated. PELA with different hydrophilicities (PELA-1, PELA-2, and PELA-3) based on various ratios of mPEG to PLA were employed to prepare microspheres exhibiting a narrow size distribution using a combined double emulsion and premix membrane emulsification method. The morphology, rhGH encapsulation efficiency, in vitro release profile, and rhGH stability of PELA microspheres during the release were characterized and compared in detail. It was found that increasing amounts of PLA enhanced the encapsulation efficiency of PELA microspheres but reduced both the release rate of rhGH and its stability. Contact angle, atomic force microscope (AFM), and quartz crystal microbalance with dissipation (QCM-D) techniques were first combined to elucidate the microcosmic mechanism of incomplete release by measuring the hydrophilicity of the PELA film and its interaction with rhGH. In addition, the pH change within the microsphere microenvironment was monitored by confocal laser scanning microscopy (CLSM) employing a pH-sensitive dye, which clarified the stability of rhGH during the release. These results suggested that PELA hydrophilicity played an important role in rhGH incomplete release and stability. Thus, the selection of suitable hydrophilic polymers with adequate PEG lengths is critical in the preparation of optimum protein drug sustained release systems. This present work is a first report elucidating the microcosmic mechanisms responsible for rhGH stability and its interaction with the microspheres. Importantly, this research demonstrated the application of promising new experimental methods in investigating the interaction between biomaterials and biomacromolecules, thus opening up a range of exciting potential applications in the biomedical field including drug delivery and tissue regeneration.

Prospects of pharmaceuticals and biopharmaceuticals loaded microparticles prepared by double emulsion technique for controlled delivery

Several methods and techniques are potentially useful for the preparation of microparticles in the field of controlled drug delivery. The type and the size of the microparticles, the entrapment, release characteristics and stability of drug in microparticles in the formulations are dependent on the method used. One of the most common methods of preparing microparticles is the single emulsion technique. Poorly soluble, lipophilic drugs are successfully retained within the microparticles prepared by this method. However, the encapsulation of highly water soluble compounds including protein and peptides presents formidable challenges to the researchers. The successful encapsulation of such compounds requires high drug loading in the microparticles, prevention of protein and peptide degradation by the encapsulation method involved and predictable release, both rate and extent, of the drug compound from the microparticles. The above mentioned problems can be overcome by using the double emulsion technique, alternatively called as multiple emulsion technique. Aiming to achieve this various techniques have been examined to prepare stable formulations utilizing w/o/w, s/o/w, w/o/o, and s/o/o type double emulsion methods. This article reviews the current state of the art in double emulsion based technologies for the preparation of microparticles including the investigation of various classes of substances that are pharmaceutically and biopharmaceutically active.

The comparison of different daidzein-PLGA nanoparticles in increasing its oral bioavailability

The aim of this research was to increase the oral bioavailability of daidzein by the formulations of poly(lactic-co-glycolic) acid (PLGA) nanoparticles loaded with daidzein. Amongst the various traditional and novel techniques of preparing daidzein-loaded PLGA nanoparticles, daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were selected. The average drug entrapment efficiency, particle size, and zeta potential of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were 81.9% ± 5%, 309.2 ± 14.0 nm, -32.14 ± 2.53 mV and 83.2% ± 7.2%, 323.2 ± 4.8 nm, -18.73 ± 1.68 mV, respectively. The morphological characterization of nanoparticles was observed with scanning electron microscopy by stereological method and the physicochemical state of nanoparticles was valued by differential scanning calorimetry. The in vitro drug-release profile of both nanoparticle formulations fitted the Weibull dynamic equation. Pharmacokinetic studies demonstrated that after oral administration of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles to rats at a dose of 10 mg/kg, relative bioavailability was enhanced about 5.57- and 8.85-fold, respectively, compared to daidzein suspension as control. These results describe an effective strategy for oral delivery of daidzein-loaded PLGA nanoparticles and might provide a fresh approach to enhancing the bioavailability of drugs with poor lipophilic and poor hydrophilic properties.

Development of enteric submicron particle formulation of papain for oral delivery

BACKGROUND

Particulate systems have received increasing attention for oral delivery of biomolecules. The objective of the present study was to prepare submicron particulate formulations of papain for pH-dependent site-specific release using pH-sensitive polymers.

METHODS

Enteric submicron particle formulations of papain were prepared by w/o/w emulsion solvent evaporation using hydroxypropyl methylcellulose phthalate (HPMCP), Eudragit L100, and Eudragit S100, to avoid gastric inactivation of papain.

RESULTS

Smaller internal and external aqueous phase volumes provided maximum encapsulation efficiency (75.58%-82.35%), the smallest particle size (665.6-692.4 nm), and 25%-30% loss of enzyme activity. Release studies in 0.1 N HCl confirmed the gastroresistance of the formulations. The anionic submicron particles aggregated in 0.1 N HCl (ie, gastric pH 1.2) due to protonation of carboxylic groups in the enteric polymer. Aggregates < 500 μm size would not impede gastric emptying. However, at pH > 5.0 (duodenal pH), the submicron particles showed deaggregation due to restoration of surface charge. HPMCP submicron particles facilitated almost complete release of papain within 30 minutes at pH 6.0, while Eudragit L100 and Eudragit S100 particles released 88.82% and 53.00% of papain at pH 6.8 and pH 7.4, respectively, according to the Korsmeyer-Peppas equation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorescence spectroscopy confirmed that the structural integrity of the enzyme was maintained during encapsulation. Fourier transform infrared spectroscopy revealed entrapment of the enzyme, with powder x-ray diffraction and differential scanning calorimetry indicating an amorphous character, and scanning electron microscopy showing that the submicron particles had a spherical shape.

CONCLUSION

In simulated gastrointestinal pH conditions, the HPMCP, Eudragit L100, and Eudragit S100 submicron particles showed good digestion of paneer and milk protein, and could serve as potential carriers for oral enzyme delivery. Stability studies indicated that formulations with approximately 6% overage would ensure a two-year shelf-life at room temperature.

Development of enteric submicron particles formulation of α-amylase for oral delivery

Enteric submicron particles (SPs) formulations of α-amylase were prepared by w/o/w emulsion solvent evaporation using hydroxypropyl methylcellulose phthalate (HPMCP) and Eudragit L 100, to avoid gastric inactivation of α-amylase. Smaller internal and external aqueous phase volume provided maximum encapsulation efficiency (71.92-73.40%), least particle size (546.4-595.4 nm) and 23-26% loss of enzyme activity. Release studies in 0.1 N HCl confirmed the gastro-resistance of formulations. The anionic SPs aggregated in 0.1 N HCl (i.e. gastric pH 1.2), due to protonation of carboxylic groups of enteric polymer. The aggregates being < 500 µm size would not impede gastric emptying. However, at pH >5.0 (duodenal pH), SPs showed de-aggregation due to restoration of surface charge. HPMCP and Eudragit L 100 SPs facilitated almost complete release of α-amylase within 30 min at pH 6.0 and 6.8, respectively, following Higuchi kinetics. PXRD and DSC indicated amorphous character and scanning electron microscope showed spherical shape of SPs. In simulated gastro-intestinal pH condition, HPMCP and Eudragit L 100 SPs showed good digestion of cooked rice and could serve as potential carrier for oral enzyme delivery. Stability studies indicated the formulations as quite stable to ensure 2 years shelf life at room temperature.

Controlled release of octreotide and assessment of peptide acylation from poly(D,L-lactide-co-hydroxymethyl glycolide) compared to PLGA microspheres

Purpose

To investigate the in vitro release of octreotide acetate, a somatostatin agonist, from microspheres based on a hydrophilic polyester, poly(D,L-lactide-co-hydroxymethyl glycolide) (PLHMGA).

Methods

Spherical and non-porous octreotide-loaded PLHMGA microspheres (12 to 16 μm) and loading efficiency of 60–70% were prepared by a solvent evaporation. Octreotide release profiles were compared with commercial PLGA formulation (Sandostatin LAR^®); possible peptide modification with lactic, glycolic and hydroxymethyl glycolic acid units was monitored.

Results

PLHMGA microspheres showed burst release (~20%) followed by sustained release for 20–60 days, depending on the hydrophilicity of the polymer. Percentage of released loaded peptide was high (70–90%); > 60% of released peptide was native octreotide. PLGA microspheres did not show peptide release for the first 10 days, after which it was released in a sustained manner over the next 90 days; > 75% of released peptides were acylated adducts.

Conclusions

PLHMGA microspheres are promising controlled systems for peptides with excellent control over release kinetics. Moreover, substantially less peptide modification occurred in PLHMGA than in PLGA microspheres.

Electronic Supplementary Material

The online version of this article (doi:10.1007/s11095-011-0517-3) contains supplementary material, which is available to authorized users.

Polyethylenglycol-co-poly-D,L-lactide copolymer based microspheres: preparation, characterization and delivery of a model protein

PURPOSE

To prepare and characterize polyethylenglycol-co-poly-D,L-lactide (PEG-D,L-PLA) multiblock copolymer microspheres containing ovalbumin. Microsphere batches made of Poly-D,L-lactide (PLA) homopolymers were prepared in order to evaluate how the presence of PEG segments into PEG-D,L-PLA copolymer could affect the behaviour of microspheres as carrier of protein drugs.

METHODS

The PEG-D,L-PLA and PLA microspheres, loaded with the model protein ovalbumin, were prepared using double emulsion solvent evaporation method. The effect of PEG segments in the microparticles matrix, on the morphology, size distribution, encapsulation efficiency and release behaviour was studied.

RESULTS

According to the results, PEG-D,L-PLA microspheres were more hydrophilic than PLA microparticles and with lower glass transition temperature. The surface of PEG-D,L-PLA microspheres was not as smooth as that of PLA microparticles, the mean diameter of PEG-D,L-PLA microparticles was bigger than that of PLA microspheres. Protein release from the microspheres was affected by the morphological structure of PEG-D,L-PLA microspheres and properties of PEG-D,L-PLA copolymer. This study suggests that PEG-D,L-PLA multiblock copolymer may be used as carrier in protein delivery systems for different purposes.

Poly(D,L-lactide-co-glycolide) protein-loaded nanoparticles prepared by the double emulsion method—processing and formulation issues for enhanced entrapment efficiency

Although extensive research in the field of biodegradable microparticles containing peptide or protein drugs has greatly advanced production know-how, the effects of critical parameters influencing successful drug entrapment have not yet been sufficiently investigated with nano-scaled carriers. This paper deals with the formulation and processing parameters of the w(1)/o/w(2) double emulsion method that can affect nanoparticle size and loading. Fluorescein isothiocyanate-labelled bovine serum albumin (FITC-BSA) was used as a model protein. Results showed that high FITC-BSA entrapment efficiencies were reached (>80%) when sonication was used for the two emulsification steps of the nanoparticle formation, independently of the mixing durations and intensities. By comparison, the use of a vortex mixer for obtaining the primary w(1)/o emulsion led to a rather poor entrapment efficiency (approximately 25%). Some inherent properties of the poly(D,L-lactic-co-glycolic acid) polymer, such as, for example, high molecular weight, high hydrophilicity or the presence of free carboxylic end groups, enhanced the drug entrapment efficiency. It was also demonstrated that a low nominal drug loading, a large volume of the inner w1 phase or the choice of methylene chloride instead of ethyl acetate as organic solvent favoured the drug entrapment, with entrapment efficiency values often reaching 100%. However, when using methylene chloride, the mean particle size was substantially increased, due to the presence of larger particles. Mean particle size increased also when the polymer concentration in the organic phase was increased.

Effects of polymer, organic solvent and mixing strength on integrity of proteins and liposomes encapsulated in polymeric microspheres fabricated by the double emulsion process

The double emulsion process has commonly been applied to encapsulate water-soluble bioactive agents into polymeric microspheres. However, the integrity of many of these agents may be destroyed by the highly energetic procedures such as sonication that are routinely used to produce stable water-in-oil (w/o) emulsion. The aim of this research was to pursue the possibility of replacing the sonication by a mild emulsification procedure such as vortex mixing, with the use of certain materials to help to obtain stable w/o emulsion. The following materials were examined: poly(lactide-co-ethylene glycol) (PELA) as the polymer, ethyl acetate and acetone as the solvents, poly(vinyl alcohol) (PVA) and d-alpha tocopheryl polyethylene glycol 1000 succinate (Vitamin E TPGS) as the emulsifiers in w/o emulsion. The experimental results, with human serum albumin (HSA) as the encapsulated agent, showed that, when vortex mixing was used, these materials could significantly improve w/o emulsion stability and help to obtain satisfactory encapsulation effects, i.e. high encapsulation efficiency (EE) and low initial release burst. A delicate structure, i.e. liposomes, which is very sensitive to sonication, was then incorporated into microspheres by the 'modified double emulsion process'. It was found that the liposomes were intact and the encapsulation effects were good. Therefore, it can be concluded that the modified double emulsion process could be advantageous for the encapsulation of delicate substances.

Microencapsulation by solvent evaporation: state of the art for process engineering approaches

Microencapsulation by solvent evaporation technique is widely used in pharmaceutical industries. It facilitates a controlled release of a drug, which has many clinical benefits. Water insoluble polymers are used as encapsulation matrix using this technique. Biodegradable polymer PLGA (poly(lactic-co-glycolic acid)) is frequently used as encapsulation material. Different kinds of drugs have been successfully encapsulation: for example hydrophobic drugs such as cisplatin, lidocaine, naltrexone and progesterone; and hydrophilic drugs such as insulin, proteins, peptide and vaccine. The choice of encapsulation materials and the testing of the release of drug have been intensively investigated. However process-engineering aspects of this technique remain poorly reported. To succeed in the controlled manufacturing of microspheres, it is important to investigate the latter. This article reviews the current state of the art concerning this technique by focusing on the influence of the physical properties of materials and operating conditions on the microspheres obtained. Based on the existing results and authors' reflection, it gives rise to reasoning and suggested choices of materials and process conditions. A part of this paper is also dedicated to numerical models on the solvent evaporation and the solidification of microspheres. This review reveals also the surprising lack of knowledge on certain aspects, such as the mechanism of formation of pores in the microspheres and the experimental study on the solidification of microspheres.

Preparation and Characterization of Cationic Chitosan-modified Poly(D,L-lactide-co-glycolide) Copolymer Nanospheres as DNA Carriers

Chitosan (CS)-modified poly(D,L-lactide-co-glycolide) (PLGA/CS) nanoparticles with cationic surface were prepared by means of emulsion—solvent evaporation technique using polyviny alcohol and chitosan as costabilizers. The preparation conditions of the cationic nanoparticles were optimized by orthogonal factorial design, and the influences of the experiment variables such as polymer concentration, the molecular weight of chitosan, etc., on the size and zeta potential of the nanoparticles were evaluated. It was shown that the diameter of the PLGA/CS nanoparticles can be controlled in the range of 150—200 nm as determined by dynamic light scattering with the optimized conditions. The zeta potential of PLGA/CS nanoparticles increased with increasing the concentration of CS (CCS) or decreasing the pH, it was up to 55 mV when CCS was 3mg/mL at pH 4 and inversed around pH 8. The optimization conditions for fabricating the relatively small diameter and high zeta potential cationic nanoparticles were CCS 3mg/mL, CPLGA 10 mg/mL, and the volume ratio of organic solution to aqueous medium 1/4. X-ray photo electron spectroscopy and fluorescence inverted microscope observations approved that CS molecules were adsorbed on the surface of PLGA nanoparticles, DNA-condensing ability of the PLGA/CS nanoparticles and cell transfection efficiency of the nanoparticle—DNA complexes were estimated by gel electrophoresis and transfection experiment to 293FT cell, respectively.

Effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin

The effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin was investigated. A modified double emulsion method was applied for the preparation of PLGAmPEG nanoparticles of cisplatin, based on the partial or complete replacement of the water of the inner aqueous phase of the emulsion by dimethyl formamide(dmf) or the addition of cisplatin in the form of a complex with poly(glutamic acid). These modifications resulted in significant improvement of cisplatin loading in the PLGA-mPEG nanoparticles. Increased cisplatin loading and encapsulation efficiency were obtained when a relatively low dmf/water ratio, low dmf volume (when pure dmf formed the inner polar phase), or a high drug/polymer ratio were applied. A reduction of average size of nanoparticles was observed with decreasing the amount of PLGA-mPEG added in the formulation or increasing sonication time. The only factor that had a significant effect on size distribution was the sonication time, with the size P.I. being decreased with increasing sonication time. Prolonged sonication, however, decreased cisplatin loading and encapsulation efficiency. From the four lyoprotectant sugars tested (glucose, lactose, mannitol, and trehalose), only mannitol could prevent nanoparticle aggregation upon lyophilization. When appropriate amounts of an effective lyoprotectant were added in nanoparticles before lyophilization, drug loading of the nanoparticles was not affected by nanoparticle lyophilization.

Preparation and characterization of spironolactone-loaded nanocapsules for paediatric use

Spironolactone is a steroidal diuretic showing incomplete oral behaviour because of its low solubility and slow dissolution rate. In this study, we applied the nanoprecipitation method to prepare spironolactone-loaded nanocapsules, at laboratory-scale and pilot-scale. The effect of several formulation variables on the spironolactone-loaded nanocapsules properties (average size, drug release rate and drug entrapment) was investigated. The optimized formulations at laboratory-scale and pilot-scale lead to the preparation of spironolactone-loaded nanocapsules with a mean size of 320 and 400 nm, respectively, a high encapsulation efficiency (96.21% and 90.56% respectively), both stable for 6 months. The release of spironolactone from nanocapsules was rapid and complete in a simulated gastric fluid, therefore recourse to spironolactone nanoencapsulation should enhance its oral bioavailability and probably its efficiency. The optimized formulations lead to a high drug-concentration in the liquid preparation (1.5 mg/ml) allowing minimizing the preparation volume administered for children medication.

Biodegradable nanoparticles loaded with insulin–phospholipid complex for oral delivery: Preparation, in vitro characterization and in vivo evaluation

Biodegradable nanoparticles loaded with insulin-phospholipid complex were prepared by a novel reverse micelle-solvent evaporation method, in which soybean phosphatidylcholine (SPC) was employed to improve the liposolubility of insulin, and biodegradable polymers as carrier materials to control drug release. Solubilization study, IR and X-ray diffraction analysis were employed to prove the complex formation. The effects of key parameters such as polymer/SPC weight ratio, organic phase and polymer type on the properties of the nanoparticles were investigated. Spherical particles of 200 nm mean diameter and a narrow size distribution were obtained under optimal conditions. The drug entrapment efficiency was up to 90%. The in vitro drug release was characterized by an initial burst and subsequent delayed release in both pH 6.8 and pH 1.2 dissolution mediums. The specific modality of drug release, i.e., free or SPC-combined, was investigated in the aid of ultracentrifugation and ultrafiltration methods. The influence of polymer type on the drug release was also discussed. The pharmacological effects of the nanoparticles made of PLGA 50/50 (Av.Mw 9500) were further evaluated to confirm their potential suitability for oral delivery. Intragastric administration of the 20 IU/kg nanoparticles reduced fasting plasma glucose levels to 57.4% within the first 8 h of administration and this continued for 12 h. PK/PD analysis indicated that 7.7% of oral bioavailability relative to subcutaneous injection was obtained.