Liposomes and PLG microparticles as sustained release antitubercular drug carriers--an in vitro-in vivo study.

Liposomes and PLG microparticles were investigated as sustained release antitubercular drug carriers for isoniazid (INH) and rifampicin (RIF). In vitro release of drugs from liposomes showed a sustained release of INH and RIF up to 4 weeks. PLG microparticles exhibited a sustained release of INH and RIF up to 6 and 49 days, respectively. In vivo drug disposition studies from liposomes indicated a sustained release of INH in plasma and various tissues up to 24 h and 5 days, respectively, while release of rifampicin was obtained for 24 and 72 h in plasma and various tissues. In vivo drug disposition studies from PEG-PLG microparticles indicated a sustained release of INH up to 9 and 27 days in plasma and various tissues, while rifampicin was detected in plasma and lungs up to 12 h and 27 days. Hepatotoxicity studies revealed no toxicity induced using biochemical tests. PLG microparticles exhibited a more sustained release of antitubercular drugs than a liposomal carrier system.     

Structural analysis of nanocapsules by nuclear magnetic resonance

An oral formulation based on poly (DL-lactide-co-glycolide) (PLG) microparticles was developed for delivery of antituberculous drugs. PLG entrapped antitubercular drugs when administered orally, were found to release the drugs in a sustained manner. This formulation was found to be stable in the acidic environment of gastric fluid whereas, in the intestinal fluid the drug release was obtained up to 20 days as indicated by in vitro studies. Pharmacokinetic analysis of the data revealed changes in C(max); AUC(o-alpha); t(1/2) (a) and t(1/2) (e) when drugs were given entrapped in PLG microparticles. Higher peak concentration, area under the concentration time curve and delayed elimination rate of entrapped drugs indicated the potential of PLG for effective treatment of tuberculosis. Further, work is being carried out to evaluate the chemotherapeutic efficacy of the antitubercular drugs encapsulated in PLG microspheres.     

Preparation and characterization of D, L-PLA loaded 17-β-Estradiol valerate by emulsion/evaporation methods

PLA microparticles containing 17-β-estradiol valerate were prepared by an emulsion/evaporation method in order to sustain drug release. This system was characterized concerning particle size, particle morphology and the influence of formulation and processing parameters on drug encapsulation and in vitro drug release. The biodegradation of the microparticles was observed by tissue histological analysis. Scanning electron microscopy and particle size analysis showed that the microparticles were spherical, presenting non-aggregated homogeneous surface and had diameters in the range of 718-880 nm (inert micro-particles) and 3-4 μm (drug loaded microparticles). The encapsulation efficiency was ～80%. Hormone released from microparticles was sustained. An in vivo degradation experiment confirmed that microparticles are biodegradable. The preparation method was shown to be suitable, since the morphological characteristics and efficiency yield were satisfactory. Thus, the method of developed microparticles seems to be a promising system for sustained release of 17-β-estradiol.     

Novel cryomilled physically cross-linked biodegradable hydrogel microparticles as carriers for inhalation therapy

In this study, novel biodegradable physically cross-linked hydrogel microparticles were developed and evaluated in-vitro as potential carriers for inhalation therapy. These hydrogel microparticles were prepared to be respirable (desired aerodynamic size) when dry and also designed to avoid the macrophage uptake (attain large swollen size once deposited in lung). The swellable microparticles, prepared using cryomilling, were based on Pluronic? F-108 in combination with PEG grafted onto both chitosan (Cs) and its N-phthaloyl derivative (NPHCs). Polymers synthesized in the study were characterized using EA, FTIR, 2D-XRD and DSC. Morphology, particle size, density, biodegradation and moisture content of the microparticles were quantified. Swelling characteristics for both drug-free and drug-loaded microparticles showed excellent size increases (between 700-1300%) and the release profiles indicated sustained release could be achieved for up to 20 days. The respirable microparticles showed drug loading efficiency up to 92%. The enzymatic degradation of developed microparticles started within the first hour and only ～10% weights were remaining after 10 days. In conclusion, these respirable microparticles demonstrated promising in-vitro performance for potential sustained release vectors in pulmonary drug delivery.     

Preparation, physiochemical characterization, and oral immunogenicity of Abeta(1-12), Abeta(29-40), and Abeta(1-42) loaded PLG microparticles formulations

Alzheimer's disease (AD) is caused by the deposition of beta-amyloid (Abeta) protein in brain. The current AD immunotherapy aims to prevent Abeta plaque deposition and enhance its degradation in the brain. In this work, the peptides B-cell epitope Abeta(1-12), T-cell epitope Abeta(29-40) and full-length Abeta(1-42) were loaded separately to the poly (D,L-lactide co-glycolide) (PLG) microparticles by using W/O/W double emulsion solvent evaporation method with entrapment efficacy of 70.46%, 60.93%, and 65.98%, respectively. The prepared Abeta PLG microparticles were smooth, spherical, individual, and nonporous in nature with diameters ranging from 2 to 12 microm. The cumulative in vitro release profiles of Abeta(1-12), Abeta(29-40), and Abeta(1-42) from PLG microparticles sustained for long periods and progressively reached to 73.89%, 69.29%, and 70.08% by week 15. In vitro degradation studies showed that the PLG microparticles maintained the surface integrity up to week 8 and eroded completely by week 16. Oral immunization of Abeta peptides loaded microparticles in mice elicited stronger immune response by inducing anti-Abeta antibodies for prolonged time (24 weeks). The physicochemical characterization and immunogenic potency of Abeta peptides incorporated PLG microparticles suggest that the microparticles formulation of Abeta can be a potential oral AD vaccine.     

PVP magnetic nanospheres: biocompatibility, in vitro and in vivo bleomycin release

PURPOSE: To synthesize and characterize a magnetic micromolecular delivery system based on PVP hydrogel with polyvinyl alcohol (PVA) as the crosslinker. METHODS: The microparticles were successfully prepared using 25 kGy Co-60 gamma-ray irradiation and characterized. Biocompatibility, in vitro and in vivo drug release tests were carried out. RESULTS AND DISCUSSION: Bleomycin was quantitatively released with in slightly over 8 h (hours) from the nanospheres containing 1mg bleomycin while the time was longer for those containing 5 mg. On the other hand free bleomycin quantitatively passed through the dialysis baffle with in only 3.5 h. For both 5 and 1 mg of bound bleomycin, it took up to 2 h to reach peak concentration compared to 30 min for the free drug. CONCLUSION: The PVP hydrogel magnetic nanospheres exhibited passive drug release that could be exploited to enhance therapeutic efficacy. The present results indicate that PVP hydrogel based magnetic nanospheres have potential as drug carriers in magnetic guided chemotherapeutic drug delivery.     

Novel cryomilled physically cross-linked biodegradable hydrogel microparticles as carriers for inhalation therapy

In this study, novel biodegradable physically cross-linked hydrogel microparticles were developed and evaluated in-vitro as potential carriers for inhalation therapy. These hydrogel microparticles were prepared to be respirable (desired aerodynamic size) when dry and also designed to avoid the macrophage uptake (attain large swollen size once deposited in lung). The swellable microparticles, prepared using cryomilling, were based on Pluronic® F-108 in combination with PEG grafted onto both chitosan (Cs) and its N-phthaloyl derivative (NPHCs). Polymers synthesized in the study were characterized using EA, FTIR, 2D-XRD and DSC. Morphology, particle size, density, biodegradation and moisture content of the microparticles were quantified. Swelling characteristics for both drug-free and drug-loaded microparticles showed excellent size increases (between 700–1300%) and the release profiles indicated sustained release could be achieved for up to 20 days. The respirable microparticles showed drug loading efficiency up to 92%. The enzymatic degradation of developed microparticles started within the first hour and only ～10% weights were remaining after 10 days. In conclusion, these respirable microparticles demonstrated promising in-vitro performance for potential sustained release vectors in pulmonary drug delivery.     

The stability of insulin in biodegradable microparticles based on blends of lactide polymers and polyethylene glycol

Insulin-loaded microparticles were produced from blends of poly(ethylene glycol) (PEG) with poly (L-lactide) (PLA) homopolymer and poly (DL-lactide co-glycolide) copolymers (PLG) using a water-in-oil solvent extraction method. The dispersed phase was composed of PLG/PEG or PLA/PEG dissolved in dichloromethane, and the continuous phase was methanol containing 10% PVP. Characteristics, including particle size distribution, insulin loading capacity and efficiencies, in vitro release, degradation and stability, were investigated. The stability of insulin associated with microparticles prepared using PEG and 50:50 PLG and PLA was analysed by HPSEC and quantified by peak area following incubation in PBS at 37 degrees C for up to 1 month. Insulin was successfully entrapped in the PLG/PEG and PLA/PEG microparticles with trapping efficiencies up to 56 and 48%, loading levels 17.8 and 10.6% w/w, and particle sizes 8 and 3 microm, respectively. The insulin-loaded PLG/PEG and PLA/PEG microparticles were capable of controlling the release of insulin over 28 days with in vitro delivery rates of 0.94 and 0.65 microg insulin/mg particles/day in the first 4 days and a steady release with rate of 0.4 and 0.43 microg insulin/mg particles/day over the following 4 weeks, respectively. Extensive degradation of the PLG/PEG microparticles also occurred over 4 weeks, whereas the use of PLA/PEG blends resulted in a stable microparticle morphology and much reduced fragmentation and aggregation of the associated insulin.     

Chemotherapeutic efficacy of poly (DL-lactide-co-glycolide) nanoparticle encapsulated antitubercular drugs at sub-therapeutic dose against experimental tuberculosis

The present study was designed to evaluate the chemotherapeutic efficacy of poly (DL-lactide-co-glycolide) (PLG) nanoparticles (NP) encapsulating three front-line antitubercular drugs (ATDs: rifampicin, RIF; isoniazid, INH and pyrazinamide, PZA) at 2/3rd therapeutic dose. PLG nanoparticles prepared by the double emulsion and solvent evaporation technique were administered orally at 2/3rd therapeutic dose to guinea pigs. A single oral administration of the formulation resulted in sustained drug levels in the plasma for 7-12 days and in the organs for 11-14 days with a significant improvement in mean residence time as well as drug bioavailability. The administration of PLG nanoparticles every 10 days (five doses) to Mycobacterium tuberculosis H(37)Rv infected guinea pigs led to undetectable bacilli in the organs, as did 46 conventional doses. Therefore, nanoparticle based antitubercular chemotherapy forms a sound basis for a reduction in dosing frequency and also offers the possibility of reducing the drug dosage.     

Controlled release pulmonary administration of curcumin using swellable biocompatible microparticles

This study involves a promising approach to achieve sustained pulmonary drug delivery. Dry powder particulate carriers were engineered to allow simultaneous aerosol lung delivery, evasion of macrophage uptake, and sustained drug release through a controlled polymeric architecture. Chitosan grafted with PEG was synthesized and characterized (FTIR, EA, DSC and 2D-XRD). Then, a series of respirable amphiphilic hydrogel microparticles were developed via spray drying of curcumin-loaded PLGA nanoparticles with chitosan-grafted-PEG or chitosan. The nanoparticles and microparticles were fully characterized using an array of physicochemical analytical methods including particle size, surface morphology, dynamic swelling, density, moisture content and biodegradation rates. The PLGA nanoparticles and the hydrogel microspheres encapsulating the curcumin-loaded PLGA nanoparticles showed average size of 221-243 nm and 3.1-3.9 μm, respectively. The developed carriers attained high swelling within a few minutes and showed low moisture content as dry powders (0.9-1.8%), desirable biodegradation rates, high drug loading (up to 97%), and good sustained release. An aerosolization study was conducted using a next generation impactor, and promising aerosolization characteristics were shown. In vitro macrophage uptake studies, cytotoxicity and in vitro TNF-α assays were performed for the investigated particles. These assays revealed promising biointeractions for the respirable/swellable nano-micro particles developed in this study as potential carriers for sustained pulmonary drug delivery.     

Preparation and in vitro evaluation of salbutamol-loaded lipid microparticles for sustained release pulmonary therapy

The aim of this study was to prepare lipid microparticles (LMs) loaded with the polar bronchodilator agent salbutamol, and designed for sustained release pulmonary delivery. The microparticles were produced by melt emulsification followed by a sonication step, using different biocompatible lipid carriers (tristearin, stearic acid and glyceryl behenate) and phosphatidylcholine as the surfactant. The use of salbutamol free base, rather than salbutamol sulphate, was necessary to obtain the incorporation of the drug in the lipid particle matrix. The prolonged release of salbutamol base was achieved only by the glyceryl behenate microparticles (40.9% of encapsulated drug being released after 8 h). The salbutamol loading was 4.2%?±?0.1 and the mass median diameter, determined by laser diffraction, ranged from 4.8 to 5.4 μm. The sustained release of LMs were formulated as a carrier-free dry powder for inhalation and exhibited a fine particle fraction of 17.3%?±?2.2, as measured by multi-stage liquid impinger.     

Swellable microparticles as carriers for sustained pulmonary drug delivery

In this investigation, novel biodegradable physically crosslinked hydrogel microparticles were developed and evaluated in vitro as potential carriers for sustained pulmonary drug delivery. To facilitate sustained release in the lungs, aerosols must first navigate past efficient aerodynamic filtering to penetrate to the deep lung (requires small particle size) where they must then avoid rapid macrophage clearance (enhanced by large particle size). The strategy suggested in this study to solve this problem is to deliver drug‐loaded hydrogel microparticles with aerodynamic characteristics allowing them to be respirable when dry but attain large swollen sizes once deposited on moist lung surfaces to reduce macrophage uptake rates. The microparticles are based on PEG graft copolymerized onto chitosan in combination with Pluronic® F‐108 and were prepared via cryomilling. The synthesized polymers used in preparation of the microparticles were characterized using FTIR, EA, 2D‐XRD, and differential scanning calorimetry (DSC). The microparticles size, morphology, moisture content, and biodegradation rates were investigated. Swelling studies and in vitro drug release profiles were determined. An aerosolization study was conducted and macrophage uptake rates were evaluated against controls. The microparticles showed a respirable fraction of approximately 15% when prepared as dry powders. Enzymatic degradation of microparticles started within the first hour and about 7–41% weights were remaining after 240 h. Microparticles showed sustained release up to 10 and 20 days in the presence and absence of lysozyme, respectively. Preliminary macrophage interaction studies indicate that the developed hydrogel microparticles significantly delayed phagocytosis and may have the potential for sustained drug delivery to the lung. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2343–2356, 2010     

Multivesicular liposome formulation for the sustained delivery of breviscapine

Breviscapine, a well-known bioactive flavonoid ingredient extracted from the traditional Chinese medicine, has been extensively used in clinic to treat ischemic cerebrovascular and cardiovascular diseases in China. In order to prolong the duration of the drug in the circulation, reduce the frequency of injection administration and subsequently afford patient compliance, multivesicular liposome (MVL, namely DepoFoam) was utilized as a sustained-delivery system for breviscapine. In vitro release and in vivo pharmacokinetics of MVLs containing breviscapine (bre-MVLs) following intramuscular injection to rats were investigated compared with those of traditional liposomes containing breviscapine (bre-TLs). The drug durations both in vitro and in vivo were significantly prolonged for the bre-MVL, and that the drug release in vitro and the absorption in vivo showed a good linear correlation (R=0.9834), which provided an evidence for the suitability to select human plasma as the medium of drug release from MVLs in vitro. Drug release from bre-MVLs (triolein/tricaprylin, 10/0) in vitro extended a long period of 5-6 days, while the bre-TLs released 80% within only 4h. The mean residence time (MRT) obtained from the pharmacokinetics study of bre-MVL was about 16.6- and 5.04-fold longer than those of breviscapine solution (BS) and bre-TL, respectively. A duration in vivo for a period of 4-5 days was fulfilled for bre-MVL. In conclusion, MVL can be successfully used as a sustained delivery system of breviscapine.     

Stabilization and encapsulation of recombinant human erythropoietin into PLGA microspheres using human serum albumin as a stabilizer

The aim of this study was to prepare recombinant human erythropoietin (rhEPO) loaded poly(lactic-co-glycolic acid) (PLGA) microspheres using human serum albumin (HSA) as a stabilizer. Prior to encapsulation, the rhEPO-HSA mixture microparticles were fabricated using a modified freezing-induced phase separation method. The microparticles were subsequently encapsulated into PLGA microspheres. Process optimization revealed that the polymer concentration in the organic phase and the sodium chloride (NaCl) concentration in the outer water phase of the s/o/w emulsion played critical roles in determining the properties of the resultant microspheres. An in vitro release test showed that rhEPO was released from PLGA microspheres in a sustained manner up to 30 days. A single injection of rhEPO-loaded PLGA microspheres in Sprague-Dawley rats resulted in elevated hemoglobin and red blood cell concentrations for about 33 days. The stability of the rhEPO within the PLGA microspheres was systematically investigated by size-exclusion high-performance liquid chromatography (SEC-HPLC), SDS-PAGE, western blot and in vivo biological activity assay. The stability of rhEPO released from rhEPO-loaded microspheres was also examined by western blot. The results suggested that the integrity of rhEPO was successfully protected during the encapsulation process and the release period from polymeric matrices.     

Formulation factors for preparing ocular biodegradable delivery system of 5-fluorouracil microparticles

Microparticles containing 5-fluorouracil (5-FU) were prepared using poly(dllactide-co-glycolide) with an oil-in-oil emulsion/solvent extraction technique. Particle characteristics including size distribution, 5-FU loading efficiencies, in vitro release and degradation were investigated. The dispersed phase was composed of PLG dissolved in dichloromethane, and the continuous phase was paraffin oil containing lecithin. 5-FU was successfully entrapped in the microparticles with trapping efficiencies up to 76%, loading level 10% w/v, and particle size 3 µm. Release profiles of 5-FU loaded microparticles were determined to follow a first-order-time relationship. An optimized preparation of 5-FU microparticles was achieved and was capable of controlling the release of 5-FU over 21 days with an in vitro delivery rate of 0.4 µg 5-FU/mg particles/ day in the study. Preliminary animal studies indicated that the 5-FU loaded microparticles as an ocular delivery system showed no ocular toxicity and no significant inflammatory response in rabbits for 2 months. The 5-FU loaded microparticles approach, with PLG, might be a potential for the application of long-term delivery of hydrophilic drugs in the eye.     

Formulation factors for preparing ocular biodegradable delivery system of 5-fluorouracil microparticles.

Microparticles containing 5-fluorouracil (5-FU) were prepared using poly(DL-lactide-co-glycolide) with an oil-in-oil emulsion/solvent extraction technique. Particle characteristics including size distribution, 5-FU loading efficiencies, in vitro release and degradation were investigated. The dispersed phase was composed of PLG dissolved in dichloromethane, and the continuous phase was paraffin oil containing lecithin. 5-FU was successfully entrapped in the microparticles with trapping efficiencies up to 76%, loading level 10% w/v, and particle size 3 microm. Release profiles of 5-FU loaded microparticles were determined to follow a first-order-time relationship. An optimized preparation of 5-FU microparticles was achieved and was capable of controlling the release of 5-FU over 21 days with an in vitro delivery rate of 0.4 microg 5-FU/mg particles/day in the study. Preliminary animal studies indicated that the 5-FU loaded microparticles as an ocular delivery system showed no ocular toxicity and no significant inflammatory response in rabbits for 2 months. The 5-FU loaded microparticles approach, with PLG, might be a potential for the application of long-term delivery of hydrophilic drugs in the eye.     

Biodegradable microparticulate system of captopril

Albumin microparticles have found many applications in diagnosis and treatment in recent years and more than 100 diagnostic agents and drugs have been incorporated into albumin microparticles. In the present study, bovine serum albumin (BSA) based microparticles bearing captopril were prepared by an emulsification-heat stabilization technique. Four batches of microparticles with varying ratio of drug and polymer were prepared. The prepared microparticles were studied for drug loading, particle size distribution, in vitro release characteristics, in vivo tissue distribution study and stability studies. The microparticles had mean diameter between 2 and 11 microm of which more than 70% were below 5 microm and incorporation efficiency of 41-63% was obtained. In vitro release profile for formulations containing captopril-loaded albumin microparticles with heat stabilizing technique shows slow controlled release up to 24 h. The in vivo result of drug-loaded microparticles showed preferential drug targeting to liver followed by lungs, kidneys and spleen. Stability studies showed that maximum drug content and closest in vitro release to initial data were found in the formulation stored at 4 degrees C. In the present study, captopril-loaded BSA microparticles were prepared and targeted to various organs to a satisfactory level and were found to be stable at 4 degrees C.     

Evaluation of microparticles containing doxorubicin suitable for aerosol delivery to the lungs

The efficacy of microparticulate systems containing anticancer agents may be assessed in vitro prior to evaluation of the effects of targeted and controlled drug release on tumor growth. Particles prepared in a size range suitable for aerosol delivery to the lungs (1-5 microm) would be useful in the treatment of locally occurring tumors. Bovine serum albumin microparticles containing doxorubicin (2.6-microm median diameter) were prepared by an emulsion technique with thermal stabilization. Dialysis was used to assess drug release in citrate phosphate buffer pH 4.0 and phosphate buffer pH 7.4, at 37 degrees C. Sixty percent of the doxorubicin load was released in a 10-h burst at pH 4.0. An additional 20% was released up to 70 h. Fifty percent of the drug was released in 70 h at pH 7.4. S180 murine sarcoma cells were incubated with doxorubicin in solution and in microparticle suspension for 24, 48, and 72 h to evaluate cytotoxicity. Viable cells were recovered in smaller numbers following treatment with doxorubicin microparticles than following treatment with doxorubicin solution. The action of doxorubicin on growth of S180 murine sarcoma cells was enhanced in vitro by delivery in microparticles. A four-fold reduction in the effective dose, at which the rate of cell death exceeds replication, was observed for microparticles (5 microg/ml) than for doxorubicin alone (20 microg/ml). Therefore, the doxorubicin microparticles exhibit potential for greater therapeutic effect than drug alone when evaluated in vitro. Further studies are required to demonstrate the aerodynamic properties of these particles and efficacy in an in vivo tumor model.     

Formulation of inhalable lipid-based salbutamol sulfate microparticles by spray drying technique

Background

The aim of this work was to develop dry powder inhaler (DPI) formulations of salbutamol sulfate (SS) by the aid of solid lipid microparticles (SLmPs), composed of biocompatible phospholipids or cholesterol.

Methods

The SLmPs were prepared by using two different solvent systems (ethanol and water-ethanol) and lipid carriers (dipalmitoylphosphatidylcholine (DPPC) and cholesterol) with/without L-leucine in the spray drying process. The spray-dried microparticles were physically-mixed with coarse lactose monohydrate in order to make our final DPI formulations and were investigated in terms of physical characteristics as well as in vitro drug release profile and aerosolization behavior.

Results

We observed significant differences in the sizes, morphologies, and in vitro pulmonary depositions between the formulations. In particular, the SS-containing SLmPs prepared with water-ethanol (30:70 v/v) solution of DPPC and L-leucine which had then been blended with coarse lactose (1:9 w/w) exhibited the highest emitted dose (87.9%) and fine particle fraction (42.7%) among the formulations. In vitro drug release study indicated that despite of having a significant initial burst release for both cholesterol and DPPC-based microparticles, the remained drug released more slowly than the pure drug.

Conclusion

This study demonstrated the potential of using lipid carriers as well as L-leucine in DPI formulations of SS to improve its aerosolization behavior and retard the release profile of the drug.     

In vitro skin permeation of estradiol from various proniosome formulations

The objective of this work was to assess the in vitro characteristics, in vivo pharmacokinetics and in vivo pharmacodynamics of nalbuphine propionate (NAP)-loaded microspheres. An oil-in-water solvent evaporation method was used to incorporate NAP into poly (d,l-lactide-co-glycolide) (PLGA)-based microspheres. The morphology of the microspheres were evaluated using scanning electron microscopy which showed a spherical shape with smooth surface. A prolonged in vitro drug release profile was observed, with 71.1% of incorporated drug released in 96 h. The release profile fit well to the Baker and Lonsdale's spherical matrix model, suggesting the release of NAP from microspheres was consistent with a diffusion mechanism. The in vivo pharmacokinetic studies after subcutaneous injection of NAP-loaded microsphere showed a sustained plasma nalbuphine (NA)-time profile, with 100% relative bioavailability comparing to the AUC obtained after intravenous injection. The in vitro release pattern correlated well with the in vivo pharmacokinetic profile. The pharmacodynamic studies evaluated using paw pressure model also showed a prolonged pharmacological response after injection of microspheres. A linear correlation between the percent analgesic effect and the logarithm of plasma NA concentration was obtained, suggesting the pharmacological response can be reflected by plasma drug concentration. This correlation may be utilized for evaluating the pharmacological responses of various NA and its prodrug-based formulations with known plasma NA concentrations.