Annealing to optimize the primary drying rate, reduce freezing‐induced drying rate heterogeneity, and determine T'g in pharmaceutical lyophilization

Searles, James A.; Carpenter, John F.; Randolph, Theodore W.

doi:10.1002/jps.1040

Cited by 260 publications

(166 citation statements)

References 39 publications

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“…Increased collagen content will promote ice crystal nucleation and raise the freezing temperature of the collagen slurry. Ice crystal size has previously been shown to be proportional to the freezing temperature, explaining the increase in pore size (which mirrors ice crystal structure) with increasing collagen content (Searles et al 2000).…”

Section: Cell Metabolic Activitymentioning

confidence: 96%

The effects of collagen concentration and crosslink density on the biological, structural and mechanical properties of collagen-GAG scaffolds for bone tissue engineering

Tierney

Haugh

Liedl

et al. 2009

Journal of the Mechanical Behavior of Biomedical Materials

199

103

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Section: Cell Metabolic Activitymentioning

confidence: 96%

The effects of collagen concentration and crosslink density on the biological, structural and mechanical properties of collagen-GAG scaffolds for bone tissue engineering

Tierney

Haugh

Liedl

et al. 2009

Journal of the Mechanical Behavior of Biomedical Materials

199

103

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“…15 Although annealing has been used to create larger ice crystals to facilitate shorter drying times for freeze-dried pharmaceuticals, the effects of annealing on the pore structure of freeze-dried scaffolds have yet to be investigated. [16][17][18] We hypothesize that annealing can be used to increase the pore size of CG scaffolds. Therefore, the specific objectives of this study were to determine (1) the effects of reducing T f to below À408C on scaffold pore size and (2) to test our hypothesis that the introduction of an annealing step during freeze-drying would lead to an increase in the pore size of CG scaffolds.…”

mentioning

confidence: 99%

“…22,23,25 The use of annealing to alter the pore size of a freeze-dried scaffold is a novel aspect of this study. Annealing has been used previously to encourage crystallization and reduce the drying cycle times of pharmaceuticals, 17,26,27 but has yet to be investigated for its effects on the structure of freeze-dried scaffolds.…”

mentioning

confidence: 99%

Novel Freeze-Drying Methods to Produce a Range of Collagen–Glycosaminoglycan Scaffolds with Tailored Mean Pore Sizes

Haugh

Murphy

O’Brien

2010

Tissue Engineering Part C: Methods

225

196

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• to copy, distribute, display, and perform the work.• to make derivative works. Under the following conditions:• Attribution -You must give the original author credit.• Non-Commercial -You may not use this work for commercial purposes.• The pore structure of three-dimensional scaffolds used in tissue engineering has been shown to significantly influence cellular activity. As the optimal pore size is dependant on the specifics of the tissue engineering application, the ability to alter the pore size over a wide range is essential for a particular scaffold to be suitable for multiple applications. With this in mind, the aim of this study was to develop methodologies to produce a range of collagen-glycosaminoglycan (CG) scaffolds with tailored mean pore sizes. The pore size of CG scaffolds is established during the freeze-drying fabrication process. In this study, freezing temperature was varied (À108C to À708C) and an annealing step was introduced to the process to determine their effects on pore size. Annealing is an additional step in the freeze-drying cycle that involves raising the temperature of the frozen suspension to increase the rate of ice crystal growth. The results show that the pore size of the scaffolds decreased as the freezing temperature was reduced. Additionally, the introduction of an annealing step during freeze-drying was found to result in a significant increase (40%) in pore size. Taken together, these results demonstrate that the methodologies developed in this study can be used to produce a range of CG scaffolds with mean pore sizes from 85 to 325 mm. This is a substantial improvement on the range of pore sizes that were possible to produce previously (96-150 mm). The methods developed in this study provide a basis for the investigation of the effects of pore size on both in vitro and in vivo performance and for the determination of the optimal pore structure for specific tissue engineering applications.

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“…5,8,[12][13][14][15] Physical states (e.g., crystallinity, crystal polymorph) of the components are important factors that determine chemical and conformational stability of proteins during the freeze-drying process and subsequent storage. [16][17][18] The stabilizing effects of disaccharides are attributed to protection of protein conformation by the substitution of surrounding water molecules and by holding protein molecules in lower molecular mobility glassstate amorphous solids.…”

mentioning

confidence: 99%

Amorphous–Amorphous Phase Separation of Freeze-Concentrated Protein and Amino Acid Excipients for Lyophilized Formulations

Izutsu¹,

Yoshida²,

Shibata³

et al. 2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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The objective of this study was to elucidate the mixing state of proteins and amino acid excipients concentrated in the amorphous non-ice region of frozen solutions. Thermal analysis of frozen aqueous solutions was performed in heating scans before and after a heat treatment. Frozen aqueous solutions containing a protein (e.g., recombinant human albumin, gelatin) or a polysaccharide (dextran) and an amino acid excipient (e.g., L-arginine, L-arginine hydrochloride, L-arginine monophosphate, sodium L-glutamate) at varied mass ratios showed single or double T g ′ (glass transition temperature of maximally freeze-concentrated solutes). Some mixture frozen solutions rich in the polymers maintained the single T g ′ of the freeze-concentrated amorphous solute-mixture phase. In contrast, amino acid-rich mixture frozen solutions revealed two T g ′s that suggested transition of concentrated non-crystalline solute-mixture phase and excipient-dominant phase. Post-freeze heat treatment induced splitting of the T g ′ in some intermediate mass ratio mixture solutions. The mixing state of proteins and amino acids varied depending on their structure, salt types, mass ratio, composition of co-solutes (e.g., NaCl) and thermal history. Information on the varied mixing states should be valuable for the rational use of amino acid excipients in lyophilized protein pharmaceuticals.Key words amorphous; freeze drying; thermal analysis; protein formulation; stabilization; mixing Freeze-drying is a popular method to formulate therapeutic proteins that are insufficiently stable in aqueous solutions during storage.1) Several freeze-dried therapeutic protein formulations contain multiple excipients, including stabilizers, bulking agents, pH buffer agents, and tonicity modifiers besides active pharmaceutical ingredient (API).2-4) Sucrose and trehalose are popular stabilizers that protect proteins from dehydration-induced irreversible structural changes during the process and from chemical degradation during storage. Certain amino acids and their salts are potent stabilizers in the freeze-drying of proteins, frozen storage of liposomes, and spray drying of vaccines.5-11) Application of the amino acid excipients that protect proteins through particular mechanisms not achievable by saccharides (e.g., aggregation-reducing effect of L-arginine (L-Arg) in aqueous solution) would increase formulation strategies in lyophilization of marginally stable proteins. 5,8,[12][13][14][15] Physical states (e.g., crystallinity, crystal polymorph) of the components are important factors that determine chemical and conformational stability of proteins during the freeze-drying process and subsequent storage. [16][17][18] The stabilizing effects of disaccharides are attributed to protection of protein conformation by the substitution of surrounding water molecules and by holding protein molecules in lower molecular mobility glassstate amorphous solids. Crystallization of some sugar alcohols (e.g., mannitol) during the freezing segment of lyophilization deprives the...

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Annealing to optimize the primary drying rate, reduce freezing‐induced drying rate heterogeneity, and determine T'g in pharmaceutical lyophilization

Cited by 260 publications

References 39 publications

The effects of collagen concentration and crosslink density on the biological, structural and mechanical properties of collagen-GAG scaffolds for bone tissue engineering

The effects of collagen concentration and crosslink density on the biological, structural and mechanical properties of collagen-GAG scaffolds for bone tissue engineering

Novel Freeze-Drying Methods to Produce a Range of Collagen–Glycosaminoglycan Scaffolds with Tailored Mean Pore Sizes

Amorphous–Amorphous Phase Separation of Freeze-Concentrated Protein and Amino Acid Excipients for Lyophilized Formulations

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