Influence of load on particle size distribution of lactose-crystalline cellulose mixed powder

Effects of loads applied to a powdery layer of a mixture of lactose and crystalline cellulose (granules) on the microparticle formation were evaluated. In a 1:1 mixture, the number of particles size, 20 microm or smaller in diameter, was reduced under loading compared with the standard value. It tended to increase with increasing ratio of lactose. In samples with a particle size of 350 microm or less, the shear friction coefficient increased with increase in the load, reached a peak at a mixing ratio of 50%, and decreased with increase in the mixing ratio. These changes were similar to those of the number of particles 20 microm or smaller. These results suggest that particle formation and aggregation under loads are dependent on the mixing rate and that there is a range of mixing rates in which no changes in the particle size distribution are observed.     

Effect of vitamin E TPGS on immune response to nasally delivered diphtheria toxoid loaded poly(caprolactone) microparticles

The nasal mucosa has many advantages as a potential site for drug and vaccine delivery. The present study has sought to exploit this route of delivery using microparticles composed of D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) as a matrix material blended with poly(caprolactone) for nasal immunisation with diphtheria toxoid. Particles were prepared by a double emulsion method, followed by spray drying and the effect of TPGS on size, zeta potential, loading and release of antigen was assessed. Particles composed of TPGS-PCL blends were spherical, smooth and monodisperse, displaying increasing yields after spray drying with increasing concentrations of TPGS. The immune response to diphtheria toxoid loaded PCL-TPGS microspheres after nasal administration was shown to be higher than that achieved using PCL microspheres alone. We conclude that TPGS shows significant potential as a novel adjuvant either alone or in combination with an appropriate delivery system.     

Influence of particle size and patient dosing technique on lung deposition of HFA-beclomethasone from a metered dose inhaler.

The objective of this study was to determine the lung delivery of HFA-134a-beclomethasone dipropionate (HFA-BDP) from a breath-activated inhaler (QVAR Autohaler) compared with proper and improper press and breathe (QVAR P&B) metered dose inhaler (MDI) technique. The hypothesis was that that the smaller particles of BDP from HFA-BDP would stay suspended longer in the inspiratory air of patients and thus reduce the deleterious effects of inhaler discoordination. The study was an open label, four period, cross-over design. Asthmatic patients (n = 7) with a history of asthma symptoms, an FEV-1 of >70% of predicted normal, and a history of reversibility to a beta-agonist of >or=12% were utilized. BDP was radiolabeled with technetium-99m and delivered from the QVAR Autohaler or QVAR P&B device in patients trained to reproducibly utilize coordinated and discoordinated P&B MDI technique. Patients using Autohaler MDI exhibited 60% lung deposition of BDP. Patients using coordinated technique with the P&B MDI exhibited 59% lung deposition. Patients trained to consistently actuate the P&B MDI before inhaling exhibited 37% lung deposition. Patients trained to consistently actuate the P&B MDI late in the inspiration (i.e., 1.5 sec into a 3-sec inspiration) exhibited 50% lung deposition. In conclusion, the breath-activated Autohaler automatically provided optimal BDP lung deposition of 60%. Patients with good P&B MDI technique also received optimal lung deposition of 59%. The degree of lung deposition was decreased as patients demonstrated poor inhaler technique. However patients with poor technique still received a large lung dose of BDP (i.e., >or=37%) compared with lung deposition values of 4-7% for CFC-BDP MDIs previously published and confirmed in this study.     

Potentiation of immune response from polymer-entrapped antigen: toward development of single dose tetanus toxoid vaccine

Poly(lactide) (PLA) polymer particles entrapping immunoreactive tetanus toxoid (TT) were used for generation of immune response using single point immunization. Immunization with different sizes of polymer particles encapsulating immunoreactive TT elicited anti-TT antibody titers that persisted for more than 5 months. However, antibody response generated by single point immunization of either nanoparticles or microparticles were lower than the conventional two doses of alum adsorbed TT. To overcome this limitation, alum was used with particles that improved anti-TT antibody response. Immunization with nanoparticles along with alum resulted in very high and early immune response: high anti-TT antibody titers were detected as early as 15 days postimmunization. However anti-TT antibody titers declined rapidly with time. Immunization with admixture of microparticles and alum elicited higher antibody titers than the particles alone and the antibody titers were high particularly during the later part of the postimmunization period. Single point immunization with admixture of PLA microparticles and alum resulted in an antibody response very close to that achieved by two injection of alum-adsorbed TT. Physical mixture of both a nano- and microparticles along with alum resulted in sustained anti-TT antibody response from very early days of postimmunization until 150 days. The antibody titers were maintained around 50 μg/ml for more than 5 months. These results indicated that immune response from polymer particles can be further improved by use of additional adjuvant. Furthermore, using various size particles or physical mixture of different size particles along with alum, it is possible to modulate the kinetics of immune response using polymer particles based immunization.     

Concomitant delivery of a CTL-restricted peptide antigen and CpG ODN by PLGA microparticles induces cellular immune response

Poly(lactide-co-glycolide) (PLGA) microparticles (MP) possess immunological adjuvant properties. Yet, exploitation of their full potential has just begun. The purpose of this study was to explore opportunities arising from surface modifications, and attachment and entrapment of combinations of antigen and a Toll-like receptor (TLR) ligand. The cytotoxic T lymphocyte (CTL)-restricted OVA ovalbumin peptide SIINFEKL was microencapsulated into bare, chitosan-coated, and protamine-coated PLGA MP using a microextrusion-assisted solvent extraction process. A TLR-ligand (CpG ODN) was either covalently coupled or physically adsorbed onto the MP surface. The peptide encapsulation efficiency decreased from 71% for uncoated particles to 62% and 45% upon coating with chitosan and protamine, respectively. CpG adsorption efficiency decreased from 93% for protamine-coated particles to 19% and 8% for chitosan and bare particles. Release of the adsorbed CpG was slow and incomplete (23% within 7 days) with the protamine coating, intermediate (>90% within 3 days) with the chitosan coating, and immediate (100% within 3?h) without coating. Interestingly, only the uncoated PLGA MP with adsorbed CpG mediated a prominent CTL response in mice at 6 days after immunization, as determined from IFN-γ release from antigen-specific CD8⁺ cells; failure of the other MP formulations was ascribed to the low release of antigen and CpG within the first week after immunization. The study illustrates novel opportunities for PLGA MP vaccines by combining antigens and immunostimulatory ligands.     

Influence of particle size,an elongated particle geometry,and adjuvants on dendritic cell activation

Modern subunit vaccines have many benefits compared to live vaccines such as convenient and competitive large scale production, better reproducibility and safety. However, the poor immunogenicity of subunit vaccines usually requires the addition of potent adjuvants or drug delivery vehicles. Accordingly, researchers are investigating different adjuvants and particulate vaccine delivery vehicles to boost the immunogenicity of subunit vaccines. Despite the rapidly growing knowledge in this field, a comparison of different adjuvants is sparsely found. Until today, little is known about efficient combinations of the different adjuvants and particulate vaccine delivery vehicles.In this study we compared three adjuvants with respect to their immune stimulatory potential and combined them with different particulate vaccine delivery vehicles. For this reason, we investigated two types of polyI:C and a CL264 base analogue and combined these adjuvants with differently sized and shaped particulate vaccine delivery vehicles. A high molecular weight polyI:C combined with a spherical nano-sized particulate vaccine delivery vehicle promoted the strongest dendritic cells activation.     

角鲨烯作为新型佐剂的免疫效果研究

目的研究以角鲨烯作为新型佐剂制备的新城疫、禽流感H5N1和H9灭活疫苗在SPF鸡体内的抗体效价水平以及对机体的细胞免疫作用。方法本试验油相中按一定的比例添加角鲨烯,按照常规方法制备灭活疫苗,免疫SPF鸡后,采用微量血凝抑制法和MTT法分别检测了SPF鸡免疫不同疫苗后机体的抗体效价水平和机体外周血T淋巴细胞的动态增殖变化。结果免疫以角鲨烯作为新型佐剂制备的新城疫、禽流感H5N1和H9灭活疫苗后,HI抗体在免疫后第2周检测为阳性,第3周达到最大值,持续到第4周抗体效价无明显下降(P>0.05);免疫组外周血T淋巴细胞增殖显著高于对照组。结论表明以角鲨烯作为新型佐剂制备的新城疫、禽流感H5N1和H9灭活疫苗对SPF鸡的促抗体效价作用和细胞免疫作用均有显著增强。     

Influence of particle size and antigen binding on effectiveness of aluminum salt adjuvants in a model lysozyme vaccine

It has been suggested that agglomeration of aluminum salt adjuvant particles during freezing and drying can cause loss of immunogenicity of vaccines formulated with such adjuvants. In this study, we tested this hypothesis and examined the immune response in a murine model to various liquid, freeze-thawed, and lyophilized vaccine formulations, using lysozyme as a model antigen. The various processing techniques and excipient levels resulted in a wide range of particle size distributions (PSDs) and antigen-adjuvant binding levels. Anti-lysozyme titers were independent of the PSD for vaccines adjuvanted with either aluminum hydroxide or aluminum phosphate and also were unaffected by the level of antigen binding to the adjuvant.     

Effect of particle size of dried mycobacteria on adjuvant induced arthritis in the rat

Freund's complete adjuvant prepared by grinding dried, heat killed Mycobacterium tuberculosis with liquid paraffin was investigated for particle size-weight distribution. Variations in the grinding times and preparative procedure had a marked effect on the arthritogenic action of the adjuvant in the rat. A satisfactory response in the injected foot was found only when the particle size was less than 19 microns and a secondary response in the non-injected foot required particles less than 10 microns in diameter.     

A comparative study of the antigen-specific immune response induced by co-delivery of CpG ODN and antigen using fusion molecules or biodegradable microparticles

CpG ODN are toll-like receptor 9 (TLR9) agonists that can enhance antigen presentation by antigen presenting cells (APCs) such as dendritic cells (DCs). The most potent antigen-specific responses are seen when CpG ODN and the antigen are co-localized in the same APC. CpG ODN-antigen fusion molecules and biodegradable microparticles entrapping CpG ODN and antigen can ensure both components are delivered to the same APC. In this study, we compared the efficacy of the CpG-ODN fusion molecules against biodegradable microparticles entrapping antigen and CpG ODN. Microparticles were prepared using a double emulsion solvent evaporation methodology. CpG ODN-OVA fusion molecules were prepared by mixing maleimide-activated protein with thiolated CpG ODN. Both CpG ODN-OVA fusion molecules and microparticles co-entrapping CpG ODN and OVA generated stronger IgG2a and interferon-gamma (IFN-gamma) responses than delivery of soluble CpG ODN and OVA. The microparticles generated stronger IgG2a and IFN-gamma immune responses than did CpG ODN-antigen fusion molecules.     

Influence of formulation factors on PpIX production and photodynamic action of novel ALA‐loaded microparticles

A novel 5‐aminolevulinic acid (ALA)‐containing microparticulate system was produced recently, based on incorporation of ALA into particles prepared from a suppository base that maintains drug stability during storage and melts at skin temperature to release its drug payload. The novel particulate system was applied to the skin of living animals, followed by study of protoporphyrin IX (PpIX) production. The effect of formulating the microparticles in different vehicles was investigated and also the phototoxicity of the PpIX produced using a model tumour. Particles formulated in propylene glycol gels (10% w/w ALA loading) generated the highest peak PpIX fluorescence levels in normal mouse skin. Peak PpIX levels induced in skin overlying subcutaneously implanted WiDr tumours were significantly lower than in normal skin for both the 10% w/w ALA microparticles alone and the 10% w/w ALA microparticles in propylene glycol gels during continuous 12 h applications. Tumours not treated with photodynamic therapy continued to grow over the 17 days of the anti‐tumour study. However, those treated with 12 h applications of either the 10% w/w ALA microparticles alone or the 10% w/w ALA microparticles in propylene glycol gel followed by a single laser irradiation showed no growth. The gel formulation performed slightly better once again, reducing the tumour growth rate by approximately 105%, compared with the 89% reduction achieved using particles alone. Following the promising results obtained in this study, work is now going on to prepare particle‐loaded gels under GMP conditions with the aim of initiating an exploratory clinical trial. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of flow rate on aerosol particle size distributions from pressurized and breath-actuated inhalers.

Particle size distribution of delivered aerosols and the total mass of drug delivered from the inhaler are important determinants of pulmonary deposition and response to inhalation therapy. Inhalation flow rate may vary between patients and from dose to dose. The Andersen Sampler (AS) cascade impactor operated at flow rates of 30 and 55 L/min and the Marple-Miller Impactor (MMI) operated at flow rates of 30, 55, and 80 L/min were used in this study to investigate the influence of airflow rate on the particle size distributions of inhalation products. Total mass of drug delivered from the inhaler, fine particle mass, fine particle fraction, percentage of nonrespirable particles, and amount of formulation retained within the inhaler were determined by ultraviolet spectrophotometry for several commercial bronchodilator products purchased in the marketplace, including a pressurized metered-dose inhaler (pMDI), breath-actuated pressurized inhaler (BAMDI), and three dry powder inhalers (DPIs), two containing salbutamol sulphate and the other containing terbutaline sulphate. Varying the flow rate through the cascade impactor produced no significant change in performance of the pressurized inhalers. Increasing the flow rate produced a greater mass of drug delivered and an increase in respirable particle mass and fraction from all DPIs tested.     

Influence of respiratory spacer devices on aerodynamic particle size distribution and fine particle mass of beclomethasone from metered-dose inhalers.

Respiratory spacer devices are used mainly with pressurized metered dose inhalers, especially those containing corticosteroids, to assist with patient coordination and reduce oropharyngeal side effects. This investigation examines the influence of different spacer devices on the delivered fine particle mass (aerodynamic diameter of <3.3 microm and <4.7 microm) of the corticosteroid beclomethasone dipropionate, which approximates the respirable dose. The Anderson Mark II Cascade Impactor was used to characterise the deposition of single doses of beclomethasone dipropionate from several metered-dose inhalers. Following actuation of one single dose the amount of beclomethasone dipropionate deposited on each stage of the impactor was quantified using reverse phase high-performance liquid chromatography and ultraviolet detection. The fine particle mass smaller than 4.7 microm for Respocort delivered by the Sanner and Fisonair spacer devices was 77.7% and 41.3% higher (p < 0.04), respectively, than the metered-dose inhaler alone, while the Breathatech spacer delivered 21.4% lower (p < 0.01). The fine particle mass of Becotide delivered by the Sanner, Fisonair, Nebuhaler, and Volumatic spacer devices were 81%, 42.4%, 46.9%, and 32.8% higher (p < 0.008), respectively, than be metered dose inhaler alone. The fine particle mass for Becloforte delivered by the Sanner, Fisonair, and Volumatic spacer devices was 82.8%, 36.9%, and 48.0% higher (p < 0.009) than that delivered by metered dose inhaler alone. This study suggests that there are significant differences in the fine particle mass of beclomethasone dipropionate delivered by respiratory spacer devices when used in conjunction with commercially available metered dose inhalers of this drug.     

Influence of particle size on rectal absorption of aspirin.

The rectal absorption of aspirin from theobroma oil suppositories was studied in seven human subjects using urinary excretion measurements. The effect of particle size on the excretion rate and cumulative amount of total salicylate excreted was demonstrated by the administration of a 600-mg dose as powdered aspirin and as aspirin disks having 0.023 as much surface as powdered aspirin. In vitro dissolution profiles of aspirin from the suppositories were studied. By the NF XIII Method II, the time required for 50% of the aspirin to dissolve from the suppository was 50 and 100 min for the powdered aspirin and the aspirin disks, respectively. In the bioavailability study, the diffusion equilibrium was attained at approximately 4-5 and 9-10 hr after the rectal administration of powdered aspirin and aspirin disks, respectively. No correlation was found between bioavailability and the dissolution profiles as determined by the USP XVIII dissolution method.     

Influence of the primary emulsification procedure on the characteristics of small protein-loaded PLGA microparticles for antigen delivery

Microparticles prepared from poly(lactic-co-glycolic acid) (PLGA) using a W1/O/W2 double emulsion solvent evaporation method are suitable vehicles for the delivery of proteins to antigen presenting cells, e.g. dendritic cells. In this study, the influence of different techniques for the preparation of the primary W1/O emulsion was investigated with respect to the protein localization within the microparticles, morphological characteristics of these particles, protein burst release and the native state of the released protein. Bovine serum albumin bearing fluorescein isothiocyanate (FITC-BSA) was used as model protein. A static micromixer was applied for the preparation of the W1/O/W2 double emulsion. Employing a rotor-stator homogenizer (Ultra-Turrax) for primary emulsification, microcapsules with a high burst release were produced, because nearly all FITC-BSA was attached to the outside of the particle wall. Using a high pressure homogenizer or an ultrasonic procedure resulted in the formation of microspheres with homogeneous protein distribution and a reduced burst release.     

Influence of the primary emulsification procedure on the characteristics of small protein-loaded PLGA microparticles for antigen delivery

Microparticles prepared from poly(lactic-co-glycolic acid) (PLGA) using a W₁/O/W₂ double emulsion solvent evaporation method are suitable vehicles for the delivery of proteins to antigen presenting cells, e.g. dendritic cells. In this study, the influence of different techniques for the preparation of the primary W₁/O emulsion was investigated with respect to the protein localization within the microparticles, morphological characteristics of these particles, protein burst release and the native state of the released protein. Bovine serum albumin bearing fluorescein isothiocyanate (FITC-BSA) was used as model protein. A static micromixer was applied for the preparation of the W₁/O/W₂ double emulsion. Employing a rotor-stator homogenizer (Ultra-Turrax®) for primary emulsification, microcapsules with a high burst release were produced, because nearly all FITC-BSA was attached to the outside of the particle wall. Using a high pressure homogenizer or an ultrasonic procedure resulted in the formation of microspheres with homogeneous protein distribution and a reduced burst release.     

How porosity and size affect the drug release mechanisms from PLGA-based microparticles

Porous, poly(lactic-co-glycolic acid) (PLGA)-based microparticles were prepared using a water-in-oil-in-water (W/O/W) solvent extraction/evaporation technique. Lidocaine was used as a model drug and different-sized particle fractions were obtained by sieving. The physicochemical properties of the devices and changes thereof upon exposure to phosphate buffer pH 7.4 were studied using optical and scanning electron microscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), gravimetric analysis and in vitro drug release measurements. In contrast to non-porous microparticles of identical composition, the relative drug release rate was found to decrease with increasing system size. SEC, DSC and gravimetric analysis showed that the degradation rate of the polymer increased with increasing microparticle dimension, indicating that autocatalytic effects play an important role even in small and highly porous PLGA-based microparticles. However, these effects were much less pronounced than in non-porous devices. Importantly, they were overcompensated by the effects of the increasing diffusion pathway lengths with increasing system dimension. Thus, high initial microparticle porosities do not only lead to increased drug mobilities, but can also fundamentally alter the underlying mass transport mechanisms.     

Effects of applied load and particle size on the plastoelasticity and tablet strength of some directly compressible powders

Correlations have been established between the particle size and packing fraction of microcrystalline cellulose, calcium phosphate dihydrate, corn starch and lactose, and the elastic recovery, stress relaxation, and tensile strengths of their tablets.     

Dual agents loaded PLGA nanoparticles: Systematic study of particle size and drug entrapment efficiency

PLGA nanoparticles simultaneously loaded with vincristine sulfate (VCR) and quercetin (QC) were prepared via O/W emulsion solvent evaporation. Six independent processing parameters and PLGA characteristics were assessed systematically to enhance the incorporation of the dual agents with different properties (VCR and QC, hydrophilic and hydrophobic molecule, respectively) into PLGA nanoparticles and control particle size. Approaches investigated for the enhancement of drug entrapment efficiencies and the controlling of particle size included the influence of the molecular weight (MW) of PLGA and the lactide-to-glycolide (L:G) ratio of PLGA, PLGA concentration, PVA concentration, initial QC content, acetone-to-dichloromethane (A/D) volume ratio, aqueous phase pH and aqueous to organic phase (W/O) volume ratio. The nanoparticles produced by optimal formulation were submicron size (139.5+/-4.3 nm, n=3) with low polydispersity index (0.095+/-0.031, n=3). Nanoparticles observed by transmission electron microscopy (TEM) showed extremely spherical shape. The entrapment efficiencies determined by high performance liquid chromatography (HPLC) by ultracentrifuge method were 92.84+/-3.37% for VCR and 32.66+/-2.92% for QC (n=3). The drug loadings were 0.0037+/-0.0001% for VCR and 1.36+/-0.12% for QC (n=3).