MicroglassificationTM: A Novel Technique for Protein Dehydration

Stability Comparison Between Microglassification and Lyophilization Using a Monoclonal Antibody

Producing solid-state formulations of biologics remains a daunting task despite the prevalent use of lyophilization and spray drying technologies in the biopharmaceutical industry. The challenges include protein stability (temperature stresses), high capital costs, particle design/controllability, shortened processing times and manufacturing considerations (scalability, yield improvements, aseptic operation, etc.). Thus, scientists/engineers are constantly working to improve existing methodologies and exploring novel dehydration/powder-forming technologies. Microglassification™ is a dehydration technology that uses solvent extraction to rapidly dehydrate protein formulations at ambient temperatures, eliminating the temperature stress experienced by biologics in traditional lyophilization and spray drying methods. The process results in microparticles that are spherical, dense, and chemically stable. In this study, we compared the molecular stability of a monoclonal antibody formulation processed by lyophilization to the same formulation processed using Microglassification™. Both powders were placed on stability for 3 months at 40 °C and 6 months at 25 °C. Both dehydration methods showed similar chemical stability, including percent monomer, charge variants, and antigen binding. These results show that Microglassification™ is viable for the production of stable solid-state monoclonal antibody formulations.

Innovative Drying Technologies for Biopharmaceuticals

In the past two decades, biopharmaceuticals have been a breakthrough in improving the quality of lives of patients with various cancers, autoimmune, genetic disorders etc. With the growing demand of biopharmaceuticals, the need for reducing manufacturing costs is essential without compromising on the safety, quality, and efficacy of products. Batch Freeze-drying is the primary commercial means of manufacturing solid biopharmaceuticals. However, Freeze-drying is an economically unfriendly means of production with long production cycles, high energy consumption and heavy capital investment, resulting in high overall costs. This review compiles some potential, innovative drying technologies that have not gained popularity for manufacturing parenteral biopharmaceuticals. Some of these technologies such as Spin-freeze-drying, Spray-drying, Lynfinity® Technology etc. offer a paradigm shift towards continuous manufacturing, whereas PRINT® Technology and Microglassification^TM allow controlled dry particle characteristics. Also, some of these drying technologies can be easily scaled-up with reduced requirement for different validation processes. The inclusion of Process Analytical Technology (PAT) and offline characterization techniques in tandem can provide additional information on the Critical Process Parameters (CPPs) and Critical Quality Attributes (CQAs) during biopharmaceutical processing. These processing technologies can be envisaged to increase the manufacturing capacity for biopharmaceutical products at reduced costs.

Lessons Learned in Protein Precipitation Using a Membrane Emulsification Technique to Produce Reversible and Uniform Microbeads

The effects of the manufacturing process and the regeneration of Shirasu porous glass (SPG) membranes were investigated on the reproducibility of protein precipitants, termed protein microbeads. Intravenous immunoglobulin (IVIG) was selected as a model protein to produce its microbeads in seven different cases. The results showed that the hydrophobically modified SPG membrane produced finer microbeads than the hydrophilic SPG membrane, but this was inconsistent when using the general regeneration method. Its reproducibility was determined to be mostly dependent on rinsing the SPG membrane prior to the modification and on the protein concentration used for emulsification. The higher concentration could foul and plug the membrane during protein release and thus the membrane must be washed thoroughly before hydrophobic modification. Moreover, the membrane regenerated by silicone resin dissolved in ethanol had better reproducibility than silicone resin dissolved in water. On the other hand, rinsing the protein precipitant with cold ethanol after the emulsification was not favorable and induced protein aggregation. With the addition of trehalose, the purity of the IVIG microbeads was almost the same as before microbeadification. Therefore, the regeneration method, protein concentration, and its stabilizer are key to the success of protein emulsification and precipitation using the SPG membrane.

Protein microbeadification to achieve highly concentrated protein formulation with reversible properties and in vivo pharmacokinetics after reconstitution

A protein precipitation technique was optimized to produce biophysically stable 'protein microbeads', applicable to highly concentrated protein formulation. Initially, production of BSA microbeads was performed using rapid dehydration by vortexing in organic solvents followed by cold ethanol treatment and a vacuum drying. Out of four solvents, n-octanol produced the most reversible microbeads upon reconstitution. A Shirasu porous glass (SPG) membrane emulsification technique was utilized to enhance the size distribution and manufacturing process of the protein microbeads with a marketized human IgG solution. Process variants such as dehydration time, temperature, excipients, drying conditions, and initial protein concentration were evaluated in terms of the quality of IgG microbeads and their reversibility. The hydrophobized SPG membrane produced a narrow size distribution of the microbeads, which were further enhanced by shorter dehydration time, low temperature, minimized the residual solvents, lower initial protein concentration, and addition of trehalose to the IgG solution. Final reversibility of the IgG microbeads with trehalose was over 99% at both low and high protein concentrations. Moreover, the formulation was highly stable under repeated mechanical shocks and at an elevated temperature compared to its liquid state. Its in vivo pharmacokinetic profiles in rats were consistent before and after the 'microbeadification'.

Protein-based microsphere biolasers fabricated by dehydration

Biolasers made of biological materials have attracted considerable research attention due to their biocompatibility and biodegradability, and have the potential for biosensing and biointegration. However, the current fabrication methods of biolasers suffer from several limitations, such as complicated processing, time-consuming and environmentally unfriendly nature. In this study, a novel approach with green processes for fabricating solid-state microsphere biolasers has been demonstrated. By dehydration via a modified Microglassification™ technology, dye-doped bovine serum albumin (BSA) droplets could be quickly (less than 10 minutes) and easily changed into solid microspheres with diameters ranging from 10 μm to 150 μm. The size of the microspheres could be effectively controlled by changing either the concentration of the BSA solution or the diameter of the initial droplets. The fabricated microspheres could act as efficient microlasers under an optical pulse excitation. A lasing threshold of 7.8 μJ mm-2 and a quality (Q) factor of about 1700 to 3100 were obtained. The size dependence of lasing characteristics was investigated, and the results showed a good agreement with whispering gallery mode (WGM) theory. Our findings contribute an effective technique for the fabrication of high-Q factor microlasers that may be potential for applications in biological and chemical sensors.

Lyophilization Process Design and Development: A Single-Step Drying Approach

High-throughput lyophilization process was designed and developed for protein formulations using a single-step drying approach at a shelf temperature (T_s) of ≥40°C. Model proteins were evaluated at different protein concentrations in amorphous-only and amorphous-crystalline formulations. Single-step drying resulted in product temperature (T_p) above the collapse temperature (T_c) and a significant reduction (of at least 40%) in process time compared to the control cycle (wherein T_p <T_c). For the amorphous-only formulation at a protein concentration of ≤25 mg/mL, single-step drying resulted in product shrinkage and partial collapse, whereas a 50 mg/mL concentration showed minor product shrinkage. The presence of a crystallizing bulking agent improved product appearance at ≤25 mg/mL protein concentration for single-step drying. No impact to other product quality attributes was observed for single-step drying. Vial type, fill height, and scale-up considerations (i.e., choked flow, condenser capacity, lyophilizer design and geometry) were the important factors identified for successful implementation of single-step drying. Although single-step drying showed significant reduction in the edge vial effect, the scale-up considerations need to be addressed critically. Finally, the single-step drying approach can indeed make the lyophilization process high throughput compared to traditional freeze-drying process (i.e., 2-step drying).

Manipulating Single Microdroplets of NaCl Solutions: Solvent Dissolution, Microcrystallization, and Crystal Morphology

A new "three-micropipette manipulation technique" for forming, dehydrating, crystallizing, and resolvating nanograms of salt material has been developed to study supersaturated single microdroplets and microcrystals. This is the first report of studies that have measured in situ both supersaturation (as homogeneous nucleation) and saturation (as microcrystal redissolution) for single microdroplets of NaCl solution using the micropipette technique. This work reports a measure of the critical supersaturation concentration for homogeneous nucleation of NaCl (10.3 ± 0.3 M) at a supersaturation fraction of S = 1.9, the saturation concentration of NaCl in aqueous solution as measured with nanograms of material (5.5 ± 0.1 M), the diffusion coefficient for water in octanol, D = (1.96 ± 0.10) × 10^-6 cm²/s, and the effect of the solvent's activity on dissolution kinetics. It is further shown that the same Epstein-Plesset (EP) model, which was originally developed for diffusion-controlled dissolution and uptake of gas, and successfully applied to liquid-in-liquid dissolution, can now also be applied to describe the diffusion-controlled uptake of water from a water-saturated environment using the extended activity-based model of Bitterfield et al. This aspect of the EP model has not previously been tested using single microdroplets. Finally, it is also reported how the water dissolution rate, rate of NaCl concentration change, resulting crystal structure, and the time frame of initial crystal growth are affected by changing the bathing medium from octanol to decane. A much slower loss of water-solvent and concomitant slower up-concentration of the NaCl solute resulted in a lower tendency to nucleate and slower crystal growth because much less excess material was available at the onset of nucleation in the decane system as compared to the octanol system. Thus, the crystal structure is reported to be dendritic for NaCl solution microdroplets dissolving rapidly and nucleating violently in octanol, while they are formed as single cubic crystals in a gentler way for solution-dissolution in decane. These new techniques and analyses can now also be used for any other system where all relevant parameters are known. An example of this is control of drug/hydrogel/emulsion particle size change due to solvent uptake.

Real-Time Visualization of the Precipitation and Phase Behavior of Octaethylporphyrin in Lipid Microparticles

The material properties of micro- and nanoparticles are fundamental for their bulk properties in suspension, like their stability and encapsulation efficiency. A particularly interesting system with potential biomedical applications is the encapsulation of hydrophobic porphyrins into lipid particles and their use as metal atom chelators, where retention and stability are keys for the design process. The overall goal here was to study the solubility, phase behavior, and mixing of octaethylporphyrin (OEP) and OEP-Cu chelates with 2 core materials, triolein (TO) and cholesteryl acetate, as single microparticles. We employed a real-time, single-particle microscopic technique based on micropipette injection to characterize the behavior of these materials and their mixtures upon solvent loss and precipitation. A clear phase separation was observed between the triolein liquid core and porphyrin microcrystals, and the ternary phase diagram of the droplet compositions and onsets of phase separation over solvent dissolution was built. On the contrary, cholesteryl acetate and OEP-Cu coprecipitated by solvent dissolution, preventing porphyrin crystallization even for very high supersaturations. This type of real-time, single-particle characterization is expected to offer important information about the formulation of other hydrophobic compounds of interest, where finding the proper encapsulation environment is a key step for their retention and stability.

An Activity-Based Dissolution Model for Solute-Containing Microdroplets

When a solute is present in an aqueous droplet, the water activity in the droplet and the rate of droplet dissolution are both decreased (as compared to a pure water droplet). One of the main parameters that controls this effect is the dynamically changing solute concentration, and therefore water activity and chemical potential, at the droplet interface. This work addresses the importance of understanding how water activity changes during solution droplet dissolution. A model for dissolution rate is presented that accounts for the kinetic effects of changing water activity at the droplet interface during the dissolution of an aqueous salt solution microdroplet into a second immiscible liquid phase. The important underlying question in this model is whether the dissolving component can be considered in local equilibrium on both sides of the droplet interface and whether this assumption is sufficient to account for the kinetics of dissolution. The dissolution model is based on the Epstein-Plesset equation, which has previously been applied to pure gas (bubble) and liquid (droplet) dissolution into liquid phases, but not to salt solutions. The model is tested by using the micropipet technique to form and observe the dehydration of single NaCl solution microdroplets in octanol or butyl acetate. The model successfully predicts the droplet diameter as a function of time in both organic solvents. The NaCl concentration in water is measured well into the supersaturated area >5.4 M, and the supersaturation limit at which NaCl nucleation happens is reported to be 10.24 ± 0.31 M.