Protective effect of sucrose on spray drying of oxyhemoglobin

Investigation of the Impact of Saccharides on the Relative Activity of Trypsin and Catalase after Droplet and Spray Drying

While using saccharides as stabilizers for therapeutic protein drying is common, the mechanisms underlying the stabilization during drying remain largely unexplored. Herein, we investigated the effect of different saccharides, trehalose dihydrate (TD), dextran (DEX), and hydroxypropyl β-cyclodextrins (low substitution-HP and high substitution-HPB), on the relative activities of the enzymes trypsin and catalase during miniaturized drying (MD) or spray drying (SD). For trypsin, the presence of saccharides, especially HP, was beneficial, as it significantly improved the enzyme activity following MD. The HPB preserved trypsin's activity during MD and SD. Adding saccharides during MD did not show a notable improvement in catalase activities. Increasing TD was beneficial during the SD of catalase, as indicated by significantly increased activity. Molecular docking and molecular dynamics simulations oftrypsin with HP or HPB revealed the influence of their substitution on the binding affinity for the enzyme. A higher affinity of HP to bind trypsin and itself was observed during simulations. Experimentally, activity reduction was mainly observed during MD, attributable to the higher droplet temperature during MD than during SD. The activities from the experiments and aggregation propensity from molecular modeling helped elucidate the impact of the size of protein and saccharides on preserving the activity during drying.

Impact of Different Saccharides on the In-Process Stability of a Protein Drug During Evaporative Drying: From Sessile Droplet Drying to Lab-Scale Spray Drying

OBJECTIVES

Solid biopharmaceutical products can circumvent lower temperature storage and transport and increase remote access with lower carbon emissions and energy consumption. Saccharides are known stabilizers in a solid protein produced via lyophilization and spray drying (SD). Thus, it is essential to understand the interactions between saccharides and proteins and the stabilization mechanism.

METHODS

A miniaturized single droplet drying (MD) method was developed to understand how different saccharides stabilize proteins during drying. We applied our MD to different aqueous saccharide-protein systems and transferred our findings to SD.

RESULTS

The poly- and oligosaccharides tend to destabilize the protein during drying. The oligosaccharide, Hydroxypropyl β-cyclodextrin (HPβCD) shows high aggregation at a high saccharide-to-protein molar ratio (S/P ratio) during MD, and the finding is supported by nanoDSF results. The polysaccharide, Dextran (DEX) leads to larger particles, whereas HPBCD leads to smaller particles. Furthermore, DEX is not able to stabilize the protein at higher S/P ratios either. In contrast, the disaccharide Trehalose Dihydrate (TD) does not increase or induce protein aggregation during the drying of the formulation. It can preserve the protein's secondary structure during drying, already at low concentrations.

CONCLUSION

During the drying of S/P formulations containing the saccharides TD and DEX, the MD approach could anticipate the in-process (in) stability of protein X at laboratory-scale SD. In contrast, for the systems with HPβCD, the results obtained by SD were contradictory to MD. This underlines that depending on the drying operation, careful consideration needs to be applied to the selection of saccharides and their ratios.

Spray-Dried Inhalable Powder Formulations of Therapeutic Proteins and Peptides

Respiratory diseases are among the leading causes of morbidity and mortality worldwide. Innovations in biochemical engineering and understanding of the pathophysiology of respiratory diseases resulted in the development of many therapeutic proteins and peptide drugs with high specificity and potency. Currently, protein and peptide drugs are mostly administered by injections due to their large molecular size, poor oral absorption, and labile physicochemical properties. However, parenteral administration has several limitations such as frequent dosing due to the short half-life of protein and peptide in blood, pain on administration, sterility requirement, and poor patient compliance. Among various noninvasive routes of administrations, the pulmonary route has received a great deal of attention and is a better alternative to deliver protein and peptide drugs for treating respiratory diseases and systemic diseases. Among the various aerosol dosage forms, dry powder inhaler (DPI) systems appear to be promising for inhalation delivery of proteins and peptides due to their improved stability in solid state. This review focuses on the development of DPI formulations of protein and peptide drugs using advanced spray drying. An overview of the challenges in maintaining protein stability during the drying process and stabilizing excipients used in spray drying of proteins and peptide drugs is discussed. Finally, a summary of spray-dried DPI formulations of protein and peptide drugs, their characterization, various DPI devices used to deliver protein and peptide drugs, and current clinical status are discussed.

Spray Freeze Dried Lyospheres® for Nasal Administration of Insulin

Pharmacologically active macromolecules, such as peptides, are still a major challenge in terms of designing a delivery system for their transport across absorption barriers and at the same time provide sufficiently high long-term stability. Spray freeze dried (SFD) lyospheres^® are proposed here as an alternative for the preparation of fast dissolving porous particles for nasal administration of insulin. Insulin solutions containing mannitol and polyvinylpyrrolidone complemented with permeation enhancing excipients (sodium taurocholate or cyclodextrins) were sprayed into a cooled spray tower, followed by vacuum freeze drying. Final porous particles were highly spherical and mean diameters ranged from 190 to 250 µm, depending on the excipient composition. Based on the low density, lyospheres resulted in a nasal deposition rates of 90% or higher. When tested in vivo for their glycemic potential in rats, an insulin-taurocholate combination revealed a nasal bioavailability of insulin of 7.0 ± 2.8%. A complementary study with fluorescently labeled-dextrans of various molecular weights confirmed these observations, leading to nasal absorption ranging from 0.7 ± 0.3% (70 kDa) to 10.0 ± 3.1% (4 kDa). The low density facilitated nasal administration in general, while the high porosity ensured immediate dissolution of the particles. Additionally, due to their stability, lyospheres provide an extremely promising platform for nasal peptide delivery.

Development and Characterization of Sodium Hyaluronate Microparticle-Based Sustained Release Formulation of Recombinant Human Growth Hormone Prepared by Spray-Drying

The purpose of this study was to develop and characterize a sodium hyaluronate microparticle-based sustained release formulation of recombinant human growth hormone (SR-rhGH) prepared by spray-drying. Compared to freeze-drying, spray-dried SR-rhGH showed not only prolonged release profiles but also better particle property and injectability. The results of size-exclusion high-performance liquid chromatography showed that no aggregate was detected, and dimer was just about 2% and also did not increase with increase of inlet temperature up to 150 °C. Meanwhile, the results of reversed-phase high-performance liquid chromatography revealed that related proteins increased slightly from 4.6% at 100 °C to 6.3% at 150 °C. Thermal mapping test proved that product temperature did not become high to cause protein degradation during spray-drying because thermal energy was used for the evaporation of surface moisture of droplets. The structural characterization by peptide mapping, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and circular dichroism revealed that the primary, secondary, and tertiary structures of rhGH in SR-rhGH were highly comparable to those of reference somatropin materials. The biological characterization by rat weight gain and cell proliferation assays provided that bioactivity of SR-rhGH was equivalent to that of native hGH. These data establish that spray-dried SR-rhGH is highly stable by preserving intact rhGH and hyaluronate microparticle-based formulation by spray-drying can be an alternative delivery system for proteins.

An overview on in situ micronization technique - An emerging novel concept in advanced drug delivery

The use of drug powders containing micronized drug particles has been increasing in several pharmaceutical dosage forms to overcome the dissolution and bioavailability problems. Most of the newly developed drugs are poorly water soluble which limits dissolution rate and bioavailability. The dissolution rate can be enhanced by micronization of the drug particles. The properties of the micronized drug substance such as particle size, size distribution, shape, surface properties, and agglomeration behaviour and powder flow are affected by the type of micronization technique used. Mechanical communition, spray drying and supercritical fluid (SCF) technology are the most commonly employed techniques for production of micronized drug particles but the characteristics of the resulting drug product cannot be controlled using these techniques. Hence, a newer technique called in situ micronization is developed in order to overcome the limitations associated with the other techniques. This review summarizes the existing knowledge on in situ micronization techniques. The properties of the resulting drug substance obtained by in situ micronization were also compared.

Sugars comparable to glutathione as hemoglobin oxidation protectants during vacuum drying

One of the most significant challenges to stabilization of blood in the dry state is mitigation of hemoglobin oxidation. Here, oxidation of free hemoglobin vacuum desiccated in phosphate-buffered saline alone reached 65%±5%. Arabinose, glucose, sucrose, trehalose, and raffinose at 100 mM were shown to reduce oxidation to 24%±2%, 23%±2%, 3%±1%, 8%±3%, and 7%±2%, respectively. For comparison, 100 mM glutathione allowed 5%±2% hemoglobin oxidation. Oxidation protection provided by glucose, sucrose, and trehalose was shown to increase with concentration between 5 and 100 mM, plateauing thereafter. Oxidation of hemoglobin dried in the presence of 100 mM trehalose was shown to increase with decreasing initial pH.

Investigation of the physical properties of spray-dried stabilised lysozyme particles

The aim of this study was to investigate the effect of the composition of formulations on the physical properties, including glass-transition temperatures (Tg) and aerodynamic-related characteristics, of spray-dried lysozyme particles. The Tg, as determined by differential scanning calorimetry, of spray-dried lysozyme formulations was found to be dependent upon the type and amount of excipient(s) included in the formulation. In addition, the Tg of sucrose-containing particles appeared to be raised markedly by the inclusion of trehalose, but not by dextran. The surfaces of all spray-dried particles were shown by scanning electron microscopy to be smooth with some containing characteristic dimples, typical of spray-dried material, and the morphology appeared to be independent of variation in excipient composition. However, the volume median diameters (VMD) of spray-dried powders, as determined by laser diffraction, were found to depend upon the amounts of excipients. The fine particle fraction of enzyme delivered to the lower stage of a twin-stage impinger from lysozyme–trehalose 1:1 powders appeared to be greater than that from lysozyme–sucrose 1:1 particles (22.5% vs 15.9%) when dispersed via a Rotahaler although a similar dispersibility of the two formulations (39.6% vs 36.7%) was found from a glass inhaler. In general, spray-drying was demonstrated to be feasible to produce respirable particles of the stabilised model protein, with Tg of the formulations being >30°C higher than room temperature.

Application of hanging drop technique to optimize human IgG formulations

Objectives

The purpose of this work is to assess the hanging drop technique in screening excipients to develop optimal formulations for human immunoglobulin G (IgG).

Methods

A microdrop of human IgG and test solution hanging from a cover slide and undergoing vapour diffusion was monitored by a stereomicroscope. Aqueous solutions of IgG in the presence of different pH, salt concentrations and excipients were prepared and characterized.

Key findings

Low concentration of either sodium/potassium phosphate or McIlvaine buffer favoured the solubility of IgG. Addition of sucrose favoured the stability of this antibody while addition of NaCl caused more aggregation. Antimicrobial preservatives were also screened and a complex effect at different buffer conditions was observed. Dynamic light scattering, differential scanning calorimetry and size exclusion chromatography studies were performed to further validate the results.

Conclusions

In conclusion, hanging drop is a very easy and effective approach to screen protein formulations in the early stage of formulation development.

Characterization and aerodynamic evaluation of spray dried recombinant human growth hormone using protein stabilizing agents

The effect of the protein stabilizers on the stability and aerosol performance of spray dried recombinant human growth hormone (SD rhGH) was investigated. rhGH solution was spray dried alone, with polysorbate 20 (at three concentrations of 0.05%, 0.01%, and 0.005%), Zn(2+) (by Zn(2+):rhGH molar ratio of 2:1 and 4:1), and/or lactose (by lactose:rhGH weight ratio of 2:1). Size exclusion chromatography (SEC) analysis of spray dried powders demonstrated that of all the potential protein stabilizers, the combination of polysorbate 20 (0.05%), Zn(2+) (Zn(2+):rhGH molar ratio of 2:1) and lactose (lactose:rhGH weight ratio of 2:1) was the most effective at protecting rhGH against aggregation during spray drying. The results of circular dichroism (CD) analysis revealed that using of polysorbate 20 (in all concentrations) and Zn(2+) (by Zn(2+):rhGH molar ratio of 2:1) together in the formulations would preserve rhGH conformational stability during the process. The particle size distribution data obtained by laser diffraction method showed all SD rhGH formulations had volume median diameter and mean diameter below 5mum. The characterization of the aerosol performance of the spray dried powders by Andersen cascade impactor (ACI) showed that by increasing the concentration of polysorbate 20 in the formulations the aerodynamic efficiency of the resultant particles was reduced. In conclusion, the optimum amounts of polysorbate 20, Zn(2+) and lactose satisfied both physical stability during spray drying process (2.37% aggregation) and good aerosol performance (fine particle fraction; FPF=38.52%).

Physical characteristics and aerosolization performance of insulin dry powders for inhalation prepared by a spray drying method

The objective of this study was to investigate the influence of formulation excipients on the physical characteristics and aerosolization performance of insulin dry powders for inhalation. Insulin dry powders were prepared by a spray drying technique using excipients such as sugars (trehalose, lactose and dextran), mannitol and amino acids (L-leucine, glycine and threonine). High performance liquid chromatography and the mouse blood glucose method were used for determination of the insulin content. The powder properties were determined and compared by scanning electron microscopy, thermo-gravimetric analysis and size distribution analysis by a time-of-flight technique. The in-vitro aerosolization behaviour of the powders was assessed with an Aerolizer inhaler using a twin-stage impinger. Powder yield and moisture absorption were also determined. Results showed that there was no noticeable change in insulin content in any of the formulations by both assay methods. All powders were highly wrinkled, with median aerodynamic diameters of 2-4 microm, and consequently suitable for pulmonary administration. The tapped density was reduced dramatically when glycine was added. The powders containing mannitol, with or without L-leucine, were less sensitive to moisture. The highest respirable fraction of 67.3 +/- 1.3% was obtained with the formulation containing L-leucine, in contrast to formulations containing glycine and threonine, which had a respirable fraction of 11.2 +/- 3.9% and 23.5 +/- 2.5%, respectively. In addition, powders with good physical properties were achieved by the combination of insulin and trehalose. This study suggests that L-leucine could be used to enhance the aerosolization behaviour of the insulin dry powders for inhalation, and trehalose could potentially be used as an excipient in the formulations.

The challenge of drying method selection for protein pharmaceuticals: product quality implications

Numerous drying methods are used to dry solutions of proteins in the laboratory and/or in pharmaceutical manufacturing. In this review article, we will discuss many of these drying methods. We will briefly introduce and compare the unit operations involved in the drying methods to give an insight on thermal history, and the different stresses that a drying method can present to an active ingredient, particularly for protein molecules. We will review and compare some important physico-chemical properties of the dried powder that result from using different drying methods such as specific surface area, molecular dynamics, secondary structure (for protein molecules), and composition heterogeneity. We will discuss some factors that might lead to differences in the physico-chemical properties of different powders of the same formulation prepared by different techniques. We will examine through a literature review how differences in some of these properties can affect storage stability. Also, we will review process modifications of the basic drying methods and how these modifications might impact physico-chemical properties, in-process stability and/or storage stability of the dried powders.

Particle engineering techniques for inhaled biopharmaceuticals

Formulation of biopharmaceuticals for pulmonary delivery is faced with the challenge of producing particles with the optimal properties for deep lung deposition without altering the native conformation of these molecules. Traditional techniques such as milling are continuously being improved while newer and more advanced techniques such as spray drying, spray freeze drying and supercritical fluid technology are being developed so as to optimize pulmonary delivery of biopharmaceuticals. While some of these techniques are quite promising, some are harsh and impracticable. Method scale up, cost-effectiveness and safety issues are important factors to be considered in the choice of a technique. This paper reviews the presently developed techniques for particle engineering biopharmaceuticals.

Effects of process variables on the powder yield of spray-dried trehalose on a laboratory spray-dryer

A systematic examination is presented of the effects of process variables on the powder yield of amorphous trehalose obtained from the Buchi Model 191 laboratory-scale mini spray dryer. By using a specially made, narrow cyclone the powder yield could be greatly improved at all process temperatures examined. Calculations of the separation efficiencies of the improved cyclone and the manufacturer's standard cyclone are given, which show that the former's higher tangential particle velocity at the radius of the exit duct is responsible for the improved performance. The powder yield increases with higher process temperatures, owing to improved droplet drying and reduced droplet/particle deposition on the walls of the drying chamber. A maximum in the powder yield is reached, however, after which it decreases sharply. This is caused by heating of the cyclone wall to >10 degrees C above the so-called 'sticky point' of the trehalose, causing increased particle deposits on the walls of the tower and cyclone. Increasing liquid feed flow rate or decreasing atomizing air flow rate too extensively were both detrimental to powder yield. The drying air flow rate should be as high as possible to ensure sufficient enthalpy throughput to dry the trehalose adequately to give a high powder yield. The enthalpy balance calculation for drying trehalose with the new cyclone was used successfully to interpret the results obtained. Some recommendations for optimizing powder yield of an amorphous material are given.

Improvement of stability and absorbability of dry insulin powder for inhalation by powder-combination technique

The effect of pulmonary absorption enhancers on the stability of active ingredients is an important factor for successful inhalation therapy as well as the effect on pharmacological activity and safety. We examined the effect of pulmonary absorption enhancers on the stability of insulin in dry powders prepared by a spray-drying technique. Although the hypoglycemic effect was greatly improved when a dry insulin powder containing citric acid (MIC SD) was administered, insulin in the MIC SD was unstable compared with the other powders examined. Bacitracin and Span 85, which are potent pulmonary absorption enhancers of insulin formulated in solutions, showed no deteriorative effect on the stability of dry insulin powder. However, they did not improve the hypoglycemic effect of insulin in dry powders. We modified the insulin dosage form with citric acid to improve the insulin stability at room temperature without loss of hypoglycemic activity. MIC Mix was formulated as a combination of insulin powder (MI') and citric acid powder (MC). MIC Mix showed hypoglycemic activity comparable to MIC SD while the insulin stability was much better than that of MIC SD at a 60 degrees C/dry condition. However, moisture lowered the insulin stability and changed the particle morphology of MIC Mix with time at a 60 degrees C/75% relative humidity condition, suggesting that a package preventing moisture absorption was necessary for the MIC Mix powder.

Liposomes and disaccharides as carriers in spray-dried powder formulations of superoxide dismutase

In this study, we aim to investigate the effects of disaccharides and liposome carriers on the activity, solid state characteristics, structural preservation, and aerosol powder performance of spray-dried superoxide dismutase (SOD) formulations. Sucrose, trehalose, and lactose were selected as stabilizing adjuvants in the spray-drying process. Dipalmitoyl phosphatidylcholine (DPPC) was the major lipid component for preparing liposomes. These SOD formulations were characterized with SOD activity assay, particle size, residual moisture content, scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), differential scanning calorimeter (DSC), and Fourier transform infrared (FT-IR) spectroscopy. We found that the inlet/outlet temperature of spray drying can be performed up to 168/122 degrees C with maintaining the activity of SOD in the SOD\DPPC\sucrose formulation for 98%. The SEM image of this formulation showed wrinkled and raisin-like appearance. Aerosol powder performance test demonstrated that this formulation exhibited excellent emitted dose (ED, 71%), aerodynamic diameter (2 microm), and respirable fraction (RF, 72%). DSC study suggested an indication of initial electrostatic stabilization of SOD by DPPC and sucrose, the following lipid perturbation by SOD, and the formation of an inclusion complex, thus minimizing the individual transition peaks of SOD and DPPC. FT-IR study showed that the major secondary structure of SOD, beta-sheet, was maintained in this formulation. The surface ESCA analysis of this formulation suggested the absence of SOD on the surface region of the powders, indicating that SOD was well surrounded and protected by DPPC and sucrose. Spray drying has been demonstrated to be a feasible process to preserve the activity of SOD in the formulation of DPPC liposomes with sucrose.

The effect of protective agents on the stability of plasmid DNA by the process of spray-drying

The effect of several protective agents was assessed on the stability of spray-dried plasmid DNA. The spray-drying process had adverse effects on the tertiary structure of plasmid DNA with the protective agents of sucrose, glycine and agarose. With the protection of these noncondensing agents, a band corresponding to the linear form of plasmid DNA was observed in the gel electrophoresis between the supercoiled circular (SC) form and the open circular (OC) form. On the contrary, spray-dried plasmid DNA maintained some degree of structural integrity under the protection of condensing agents. For the protection by neutral condensing polymers, such as polyethylene glycol 1000 and 4000, no linear form between the SC form and the OC form of plasmid DNA was revealed in the gel electrophoresis. Also, excess cationic condensing polymer, polyethyleneimine, had the ability to provide the plasmid DNA with protection from degradation as indicated by the preservation in SC and OC forms of plasmid DNA on the agarose gel electrophoresis. Moreover, DNA topology was unchanged after six-month storage at 4 degrees C by the protection of these neutral and cationic condensing agents. Accordingly, DNA condensation induced by condensing agents may provide a way to minimize damage to plasmid DNA by the process of spray drying.

Effects of sucrose and trehalose on the preservation of the native structure of spray-dried lysozyme

PURPOSE

To investigate the effects of sucrose, trehalose, sucrose/ dextran mixtures, and sucrose/trehalose mixtures on the preservation of the native structure of spray-dried lysozyme in the solid state.

METHODS

The intensity of the alpha-helical band and the melting enthalpies (deltaH(m)) of spray-dried lysozyme in the dried form and in aqueous solution were obtained using second derivative FTIR and differential scanning calorimetry (DSC) respectively.

RESULTS

The intensity of the alpha-helical band and the deltaH(m) of spray-dried lysozyme obtained were linearly correlated and both suggest that the stabilization of lysozyme in the dried form was excipient concentration-dependent with a close to maximum stabilization being conferred by sucrose or trehalose at a mass ratio 1-2 (sugar:enzyme). Sucrose appeared to be more effective than trehalose on a weight by weight basis whilst stabilizing effects of dextran/sucrose or trehalose/ sucrose mixtures were found to be additive.

CONCLUSION

Dehydration during spray drying was considered the main stress to the denaturation of lysozyme. A major effect of the sugars in protecting lysozyme against dehydration was attributable to hydrogen bonding between the sugar and protein molecules, which lead to an increase in the change in the negative value of the free energy between native and denatured states.

The effect of process variables on the degradation and physical properties of spray dried insulin intended for inhalation

The aim of this study was to investigate the effect of process variables on the degradation and physical properties of spray dried insulin intended for inhalation. A 2(4) full factorial experimentally designed study was performed to investigate the influence of the following independent spray drying variables: feed flow rate, nozzle gas flow rate, inlet air temperature and aspirator capacity (drying gas flow rate). Human insulin (biosynthetic and Ph.Eur. quality) was dissolved in distilled water to concentrations of 5 mg/ml. The solutions were spray dried in a Mini Spray Dryer Büchi and the dry powders produced were characterized by high performance liquid chromatography, size exclusion chromatography, laser diffraction, thermo gravimetric analysis, scanning electron microscopy and weighing. The degradation of insulin was found to be affected mainly by the process variables that determine the outlet air temperature, i.e.: inlet air temperature, aspirator capacity and feed flow rate. The outlet air temperature should be kept below 120 degrees C to avoid degradation. A statistical optimization of the spray drying variables was performed, and found to recommend an experiment with an outlet air temperature of 61+/-4 degrees C. This experiment ought to generate a yield of 54+/-7% by weight of particles with a mass median diameter 2.9+/-0.4 microm, moisture content 3.9+/-0.5% by weight, content of high molecular weight proteins 0.3+/-0.1% by area, A-21 desamido insulin 0.3+/-0.05% by area and other insulin related compounds 0.3+/-0.1% by area.

Low-temperature micronization of a peptide drug in fluid propellant: case study cetrorelix

Aim of this study was to elaborate an efficient method for the micronization of the decapeptide cetrorelix (a GnRH-antagonist), in order to obtain a microsuspension as basis for other pharmaceutical preparations, such as e.g. inhalation aerosols. A modified pearl-mill coupled with a cryostat was used for the micronization of cetrorelix in fluid propellant and operated under different conditions. The obtained cetrorelix suspensions were analyzed for particle size distribution, purity of cetrorelix, and for metal contamination through abrasion from parts of the mill. The method allowed an effective micronization of cetrorelix. The mean particle size of the initial cetrorelix lyophilizate bulk ware was reduced from 52.5 microm (Volume Mean Diameter, VMD) down to 14.9, 6.1 and 3.1 microm, respectively, respectively. The HPLC analysis of all cetrorelix suspensions after micronization did not show signs of decomposition as compared to the initial product. The elementary analysis of the suspensions performed by inductively coupled plasma mass spectrometry revealed a negligible amount of contaminants in the suspension (Zr = max. 0.6 ppm; Fe, Cr, Ni, Ba, below limit of quantification, i.e. < 0.14 ppm). The only appreciable contaminant, Aluminum (Al = 1.1 ppm), was derived from the mechanical capping of aluminum canisters prior to analysis. The Zr determination in the suspension of 0.6 ppm, is still considered to be negligible as compared to the legally tolerated limit of air contamination. By low-temperature micronization in fluid propellant, fine drug suspensions of cetrorelix for pMDIs can be directly manufactured in one-step procedure without destruction of the peptide structure and without appreciable product contamination.

A novel apparatus for rat in vivo evaluation of dry powder formulations for pulmonary administration

The lungs have attracted increasing attention as a site for administration of drugs, including macromolecules that are poorly absorbed from the intestine. There have been a number of basic studies in which peptide solutions were administered to experimental animals via the lungs. Although there have been several studies of pulmonary peptide absorption from dry powder formulations, a simpler and more inexpensive apparatus for administration of dry powders would enhance rapid screening of the formulations. In this study, we developed a simple apparatus to disperse dry powders. The apparatus has two 3-way stopcocks; one allows dispersal of powders at a constant pressure and airflow, and the other allows rats to breathe before and after administration. Dry powders of fluorescein (FL) and FITC-dextran (FD4) were manufactured by the spray-drying technique. The effects of operating conditions on the absorption of these model drugs were examined in rats. The C(max) for FL from dry powder was lower than that from solution and mean residence time was extended, suggesting that dissolution was the rate-determining step for FL absorption from dry powder. For FD4, the rate of absorption may not be regulated by dissolution but by epithelial transport. Absorption of insulin from spray-dried powder via the rat trachea was investigated using this apparatus. Intratracheally administered spray-dried insulin powder decreased plasma glucose level to a greater extent than spray-dried insulin solution administered via the same route. Thus, the apparatus is simple, inexpensive, and useful for rapid screening of dry powder formulations.

Surface composition of spray-dried particles of bovine serum albumin/trehalose/surfactant

PURPOSE

To characterize via electron spectroscopy for chemical analysis (ESCA) the surface of spray-dried particles of trehalose plus a protein (bovine serum albumin). Additionally, to show how and why the addition of a surfactant reduces protein adsorption, and by this mechanism could reduce protein instability during spray-drying.

METHODS

Aqueous solutions of trehalose plus bovine serum albumin (bSA) were spray-dried with increasing concentrations of surfactant. The surface composition of the dried particles was examined using ESCA.

RESULTS

The presence of bSA, trehalose, and surfactant could be detected quantitatively in the particle surface. In the absence of surfactant the bSA had a large surface excess concentration (determined via its N atoms). Increasing concentration of polysorbate 80 reduced the surface excess of bSA in a concentration-dependent manner. At high polysorbate 80 concentration (5 mg/ml) the bSA could no longer be detected in solid surface. Using sodium dodecyl sulfate it was shown that the reduction in surface concentration of the protein is accompanied by a simultaneous increase in surface concentration of the surfactant. Neither surfactant fully covers the surface at the point of complete protein exclusion.

CONCLUSIONS

ESCA provides a direct, quantitative measure of the surface composition of spray-dried trehalose/protein/surfactant particles. Surfactant reduces protein adsorption at the water/air-interface. This appears to be a result of complex formation with the surfactant within the bulk spray solution.

Development of a new type nozzle and spray-drier for industrial production of fine powders

Sophisticated nozzle and spray-drier were newly developed. The nozzle type was that of four-phase spraying, where two liquid streams and two air streams were blown off. The spray pattern from the nozzle was of a hollow-cone type. Mean diameter of droplets in the mist was 13.2 microm in weight average in the condition of blowing at 776 g/min in air flow and 500 ml/min in liquid flow. That is, the weight-based flow ratio of air to liquid was as small as 1. 55. The geometric standard deviation of the droplet size was less than 1.65. This nozzle was still available for a concentrated suspension up to 27% solid without formation of the sludge on the orifice. Thus, fine powder with 1.99 microm in mean diameter was obtained by means of the nozzle and the spray-drier newly developed by us. These are promising for industrial production of the fine powder with low energy and high recovery.

Hydroxypropyl-beta-cyclodextrin inhibits spray-drying-induced inactivation of beta-galactosidase

The single-step, fast spray-drying process may represent a valuable alternative to the multistep, time-consuming freeze-drying process in the area of formulation and processing of biopharmaceuticals. In this study, we tested the use of sucrose and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as stabilizing excipients in the spray-drying of a model protein, beta-galactosidase. The solutions were processed using a Büchi 190 cocurrent Mini Spray Dryer at an outlet temperature of 61 +/- 2 degrees C. The powders were redissolved and analyzed for catalytic activity, aggregation, chemical decomposition, and thermal susceptibility as observed by high-resolution calorimetry. Spray-drying significantly inactivated beta-galactosidase. Spray-drying beta-galactosidase in the presence of sucrose did not prevent inactivation. However, after spray-drying beta-galactosidase in the presence of HP-beta-CD, or HP-beta-CD and sucrose, full catalytic activity was exhibited on reconstitution. Furthermore, the reconstituted product was unchanged in terms of molecular weight, charge, and thermal stability. These findings are consistent with a hypothesis that the change responsible for inactivation of beta-galactosidase was mainly a monomolecular, noncovalent change, i. e., the formation of incorrect structures, that arose from surface denaturation. This study clearly demonstrates that cyclodextrins can be useful stabilizing excipients in the preparation of spray-dried protein pharmaceuticals.

Moisture effects on protein-excipient interactions in spray-dried powders. Nature of destabilizing effects of sucrose

The preparation of stable solid protein formulations presents significant challenges. Ultimately, the interactions between incorporated excipients and the pharmaceutical protein determine the formulation stability. In this study, moisture was utilized to probe the interactions between a model protein, trypsinogen, and sucrose in the solid state, following spray drying. Through investigation of the physical properties of the spray-dried formulations, we attempted to elucidate the mechanisms underlying the previously observed stabilizing and destabilizing effects of the carbohydrate during spray drying. Both dynamic and equilibrium moisture uptake studies indicated the presence of an optimal protein-sugar hydrogen bonding network. At low sucrose contents, a preferential protein-sucrose hydrogen bonding interaction was dominant, resulting in protein stabilization. However, at high carbohydrate concentrations, preferential sugar-sugar interactions prevailed, resulting in a phase separation within the formulation matrix. The preferential incorporation of the sucrose molecules in a sugar-rich phase reduced the actual amount of the carbohydrate available to interact with the protein and thereby decreased the number of effective protein-sucrose contacts. As a consequence, the protein could not be effectively protected during spray drying. We hypothesize that the observed phase separation at this sucrose concentration regime originates from its exclusion from the protein in solution before spray drying, further accompanied by preferential clustering of the sucrose molecules.

Activity-stability considerations of trypsinogen during spray drying: effects of sucrose

The preparation and processing of protein pharmaceuticals into powders may impose significant stresses that could perturb and ultimately denature them. In many cases their stabilization through added excipients is necessary to yield native and active proteins. In this study, the effect of spray drying on the structure and activity of a model protein (trypsinogen) was investigated. In the absence of excipients, spray drying resulted in small losses of its enzymatic activity. Protein conformational rearrangements in the solid state (observed via FTIR) and irreversible aggregation (upon reconstitution) constituted the major degradation pathways. The irreversible unfolding in the solid state was also confirmed by solution calorimetric studies that indicated a decreased thermal stability of the spray-dried protein after reconstitution. The presence of sucrose, a thermal and dehydration stress stabilizer, induced a concentration-dependent protective effect. Protein protection was afforded even at low carbohydrate concentrations, while at specific mass ratios (sucrose-to-protein = 1:1) complete activity preservation was achieved. However, at the high end of sucrose concentrations, a small destabilization was evident, indicating that excluded volume effects may be undesirable during preparation of protein microparticles via spray drying. The profile of both the protein conformational changes and thermal stability in the solid state closely followed that of the incurred activity losses, indicating that protein stabilization during dehydration is crucial during processing of these polypeptides.

Stability and surface activity of lactate dehydrogenase in spray-dried trehalose

The stability of the model protein lactate dehydrogenase (LDH) during spray-drying and also on subsequent dry storage was examined. Trehalose was used as a carrier. The spray-drying temperatures Tinlet and Toutlet have a measurable effect on LDH inactivation. Low Tinlet produced the least process inactivation, but gave a high residual moisture content making the protein's storage stability poor. High Tinlet reduced residual moisture and improved storage stability, but at the cost of high process inactivation. As already found for other systems, addition of a surfactant (in this case polysorbate 80) could ameliorate process inactivation of LDH at Tinlet = 150 degreesC. Surfactant had, however, a deleterious effect on storage stability of LDH, the vital factor being the molar ratio of surfactant/protein in the dried product. By using electron spectroscopy it was shown that LDH has a 10 times higher surface concentration in the dried trehalose particles than expected for a homogeneous distribution. Surface tension measurements at the water/air interface proved that LDH is surface active, although the Gibbs equation appeared to be inapplicable. Calculations of spray-droplet formation time and drying time indicate than the extent of diffusion-driven LDH adsorption to the liquid/air interface is sufficient to account for the measured amount of LDH inactivation during spray-drying. The presence of 0.1% polysorbate 80 to the spray solution prevents LDH from appearing at the surface of the dried particles. As a negative control, the phosphatide Lipoid E 80 does not prevent the appearance of LDH in the surface according to electron spectroscopy and does not therefore prevent LDH inactivation during spray-drying at Tinlet = 150 degreesC.

Physicochemical stability of crystalline sugars and their spray-dried forms: dependence upon relative humidity and suitability for use in powder inhalers

Lactose, trehalose, sucrose, and mannitol were purchased in crystalline form and fractionated by sieving. Coarse (125-212 microns) and fine (44-74 microns) free-flowing fractions were selected as typical of drug carriers in dry-powder inhalers. In addition, one batch of each sugar was spray-dried to form a respirable powder (> 50% [w/w], < 5 microns). Both fractions and the spray-dried powders were characterized before and after storage for 30 days at < 23%, 23%, 52%, 75% and 93% relative humidity (RH) at 25 degrees C. Moisture uptake was determined by thermogravimetric analysis (TGA) validated by Karl Fischer titration. Sieve fractions (before storage at different RHs) and spray-dried materials (before and after storage) were further characterized by differential scanning calorimetry (DSC) and x-ray powder diffraction (XRPD). All crystalline sieve fractions (except sucrose at 93% RH) were stable at 25 degrees C and showed insignificant moisture uptake when exposed to each relative humidity for 30 days. Sucrose dissolved in sorbed moisture at 93% RH. Spray-dried lactose, sucrose, and trehalose, which were collected in the amorphous form, showed moisture uptake, without recrystallization, when held for 30 days at 23% RH. These sugars recrystallized as sintered masses and became undispersible at > or = 52% RH. Spray-dried mannitol was apparently 100% crystalline when collected directly from the spray-dryer; it did not show humidity-induced changes. The physicochemical behavior of each sugar form is discussed as it relates to the sugar's suitability as a powder-inhaler excipient, with both conventional and protein drugs.

Effect of spray drying and subsequent processing conditions on residual moisture content and physical/biochemical stability of protein inhalation powders

PURPOSE

To understand the effect of spray drying and powder processing environments on the residual moisture content and aerosol performance of inhalation protein powders. Also, the long-term effect of storage conditions on the powder's physical and biochemical stability was presented.

METHODS

Excipient-free as well as mannitol-formulated powders of a humanized monoclonal antibody (anti-IgE) and recombinant human deoxyribonuclease (rhDNase) were prepared using a Buchi 190 model spray dryer. Residual moisture content and moisture uptake behavior of the powder were measured using thermal gravimetric analysis and gravimetric moisture sorption isotherm, respectively. Protein aggregation, the primary degradation product observed upon storage, was determined by size-exclusion HPLC. Aerosol performance of the dry powders was evaluated after blending with lactose carriers using a multi-stage liquid impinger (MSLI).

RESULTS

Spray-dried powders with a moisture level (approximately 3%) equivalent to the freeze-dried materials could only be achieved using high-temperature spray-drying conditions, which were not favorable to large-male manufacturing, or subsequent vacuum drying. These dry powders would equilibrate with the subsequent processing and storage environments regardless of the manufacturing condition. As long as the relative humidity of air during processing and storage was lower than 50%, powders maintained their aerosol performance (fine particle fraction). However, powders stored under drier conditions exhibited better long-term protein biochemical stability.

CONCLUSIONS

Manufacturing, powder processing, and storage environments affected powder's residual moisture level in a reversible fashion. Therefore, the storage condition determined powder's overall stability, but residual moisture had a greater impact on protein chemical stability than on powder physical stability.

Spray-drying of air-liquid interface sensitive recombinant human growth hormone

Spray-drying is an attractive method for preparing fine recombinant human growth hormone (rhGH) powders if the detrimental effect of protein degradation at the air-liquid interface on the protein can be minimized. In this study, we demonstrated that rhGH degradation (insoluble and soluble aggregate formation), as the consequence of air-liquid interfacial degradation, could be prevented using the appropriate formulation. Adding polysorbate-20 surfactant into the liquid feed (with no presence of sugar protectant) significantly reduced the formation of insoluble protein aggregates, while adding the divalent metal zinc ion effectively suppressed the formation of soluble protein aggregates. The combination of the two yielded a spray-dried rhGH powder having insignificant protein degradation. Our data suggest that the two components might protect the protein through different mechanisms. Polysorbate molecules occupy the air-liquid interface of spray droplets, thereby reducing the chance for rhGH to form insoluble aggregates by surface denaturation. Two zinc ions associate with two rhGH molecules to form a dimer complex that can resist the formation of soluble protein aggregates. Characterization of spray-dried powders by scanning electron microscopy suggests that both formulation and drying conditions have a strong influence on particle morphology and shape. Overall, spherical rhGH powders of smooth surface and good biochemical quality can be prepared by spray-drying using this formulation with no addition of sugar protectant.

The effect of operating and formulation variables on the morphology of spray-dried protein particles

The purpose of this research was to investigate the shape and morphology of various spray-dried protein powders as a function of spray-drying conditions and protein formulations. A benchtop spray dryer was used to spray dry three model proteins in formulation with a sugar or a surfactant. Physical characterizations of the powder included morphology (scanning electron microscopy), particle size, residual moisture, and X-ray powder diffraction analyses. A significant change in particle shape from irregular (e.g., "donut") to spherical was observed as the outlet temperature of the dryer was decreased. The drying air outlet temperature was shown to depend on various operating parameters and was found to correlate with the drying rate of atomized droplets in the drying chamber. The morphology of spray-dried protein particles was also affected by formulation. In protein:sugar formulations, spray-dried particles exhibited a smooth surface regardless of the protein-to-lactose ratio, whereas roughness was observed when mannitol was present at > 30% of total solids, due to recrystallization. Protein particles containing trehalose at concentrations > 50% were highly agglomerated. The presence of surfactant resulted in noticeably smoother, more spherical particles. The shape and the morphology of spray-dried powders are affected by spray drying conditions and protein formulation. This study provides information useful for development of dry proteins for fine powder (e.g., aerosol) applications.

The effect of process and formulation variables on the properties of spray-dried beta-galactosidase

The objective of this study was to evaluate the joint effects of various processing and formulation variables on the properties of spray-dried beta-galactosidase using statistically designed experiments. The key response variables evaluated were product yield, residual enzymatic activity, moisture content and particle size and appearance. The residual enzymatic activity and product yield were significantly affected by the processing variables. The highest product yields were obtained when the drier outlet temperature was relatively high, resulting in extensive protein denaturation. Subsequent experiments, therefore, compared the relative effectiveness of four stabilizers (mannitol, sucrose, arginine hydrochloride and trehalose) in terms of their ability to preserve enzymatic activity during the spray-drying process and during long-term storage. Trehalose was the most suitable stabilizer. The effect of a number of other formulation variables (total solids level, ratio of stabilizer to protein, presence of surfactant and presence of buffer) was also investigated. A final formulation consisting of 6% beta-galactosidase and 10% trehalose in deionized water was selected. Spray-drying at inlet and outlet temperatures of 140 and 95 degrees C, respectively, results in greater than 70% yields of a fully active product with a moisture content of 2-5% and a mean particle size of 2-4 microns.

Feasibility study on spray-drying protein pharmaceuticals: recombinant human growth hormone and tissue-type plasminogen activator

The feasibility of spray-drying solutions of recombinant methionyl human growth hormone (hGH) and tissue-type plasminogen activator (t-PA) was investigated. hGH was formulated in a mannitol phosphate buffer and t-PA was used in an arginine phosphate formulation containing 0.004% (w/v) polysorbate 80. Using filtered air (90-150 degrees C) as the drying medium, hGH could be dried to a residual moisture content of < or = 4%. However, approximately 25% of the protein was degraded during the processing. Results of atomization studies suggest that surface denaturation at the air-liquid interface of the droplets in the spray plays a major role in the degradation of the protein. The addition of 0.1% (w/v) polysorbate 20 into the hGH formulation reduced the formation of soluble and insoluble aggregates by approximately 90% during atomization. During spray-drying the addition of 0.1% (w/v) polysorbate 20 reduced the formation of soluble and insoluble aggregates by approximately 70 and 85%, respectively. In contrast, t-PA remained intact upon atomization. Depending on the spray-drying conditions, product powders with a residual moisture content between 5 and 8% were obtained. No oxidation, aggregation, or denaturation occurred in the protein under several operation conditions. Overall, this study demonstrates that it is feasible to spray-dry t-PA in the current marketed formulation.