Protein stability during freezing: separation of stresses and mechanisms of protein stabilization

Impact of vial quality on interactions, particle formation, container closure integrity, and gas permeability for frozen drug product storage

The frozen storage of biopharmaceuticals brings new challenges to the primary packaging material. Due to an increasing demand and the downsides of standard type I glass vials, such as vial breakage, novel vial types for special applications of parenteral drug products have been introduced to the market in the past years. Mechanical stresses due to dimensional changes experienced during freezing and thawing could change the material properties, hence affecting the interaction with the drug product stored in the vial or functionality such as overall integrity. Therefore, we studied the suitability of different vial qualities related to the thermally induced mechanical stresses experienced during frozen drug product preparation and storage. First, the possible failure modes for each vial type were identified. The interaction between vial surface and drug product were investigated considering surface hydrophobicity, surface free energy and surface roughness as well as microscopically visible changes analyzed by confocal laser scanning microscopy. Differences in surface hydrophobicity, roughness and surface free energy between the vial types did not impact the performance upon freeze-thaw stress and did not change with the stress. Screening the vial content for particles originating from the container using light and electron scanning microscopy combined with energy-dispersive X-ray spectroscopy showed only rare cases of particles in coated glass vials. Under extreme stress conditions, including a drop-test in the frozen state, a low number of particles was also detected in coated polymer vials. No quality issues regarding the functionality were observed upon container closure integrity testing, while the oxygen permeability was slightly increased for uncoated and especially coated polymer vials. Overall, the results show that several vial types are appropriate for the frozen storage of drug products and selection should be based on the formulation and other product requirements.

Insights into myofibrillar protein denaturation during freezing: The impact of ice-water interface area

This study investigated the impact of the ice-water interface area on the denaturation of myofibrillar protein (MP) over 1, 3, and 5 freeze-thaw cycles. Experimental systems designed to generate ice-water interfaces with two distinct surface areas were established by employing rapid freezing at -80 °C and slow freezing at -25 °C, resulting in surface areas of 64.63 m2/100 mL and 54.05 m2/100 mL, respectively. Following three freeze-thaw cycles, the process of rapid freezing, characterized by formation of a larger ice-water interface area, was found to significantly influenced the functional properties of MP. The impact was evidenced by a reduction in solubility, total sulfhydryl content, and thermal denaturation temperature. Structural modifications in MP suggested that the larger ice-water interface led an accelerated rate of protein unfolding during freezing. Interfacial pressure and confocal laser scanning microscopy (CLSM) results demonstrated that the larger ice-water interface area could be more able to reduce protein interfacial adsorption and enhanced protein emulsion aggregation. The addition of 0.1 % surfactant Tween 80 prior to freezing markedly enhanced protein stability throughout both the freezing and subsequent freeze-thaw cycles. The findings suggested that to further inhibit MP frozen denaturation, it is important to consider limiting the expansion of ice-water interface area.

Formulation development and feasibility of AAV5 as a lyophilized drug product

The majority of adeno-associated virus (AAV) gene therapies are currently developed as frozen formulations (e.g., ≤ - 60 °C) that are challenging to maintain and distribute world-wide. Lyophilization can allow for long-term refrigerated storage and improved shelf-life that lowers long-term cost. Here, we performed a lyophilization feasibility study to assess the ability of several different excipients to stabilize AAV5 during lyophilization and on storage stability. A range of biophysical techniques were used to assess capsid integrity on a molecular level including quantification of externalized DNA, capsid particle size, and capsid monomer percent area. Additionally, transmission electron microscopy was used for the first time to monitor the size and integrity of the capsids subjected to the lyophilization process, and the results supported other characterization methods used in this study. A formulation containing hydroxyectoine and trehalose stabilized capsid structure directly after lyophilization, as observed directly by 5.0 % of internally stained capsids (empty) and indirectly with 7.5 % external DNA. A recombinant human albumin and trehalose formulation stabilized capsid structure on stability as observed by improved external DNA and monomer profiles overtime. Adversely, mannitol crystallization negatively affected capsid structure. Our findings indicate that lyophilization is a viable option to frozen formulation for stabilizing AAV5 drug products.

Iron saturation and binding capacity of lactoferrin - development and validation of a colorimetric protocol for quality control

Among the numerous biofunctional properties of lactoferrin, its ability to bind iron ions can be considered a core function. The saturation level with ferric iron affects the stability and functionality of the protein. To reliably quantify the iron saturation, an assay based on the color reagent Ferrozine was developed and validated concerning the lower detection (0.023 μg mL-1) and quantification limits (0.069 μg mL-1), as well as precision, recovery and accuracy values. The established assay was used to monitor iron uptake, comparing two commercially available bovine lactoferrin powders. Significant differences between the samples were observed. One sample exhibited nearly ideal binding behavior with a high affinity for ferric iron (saturation > 98 %), while the comparison sample did not exceed saturation values >80 %. This finding underscores the importance of assessing the iron status and binding capacity for the quality evaluation of lactoferrin products.

Freeze-Induced Protein Assembly of α-Synuclein into Stable Microspheres to Fabricate Light-Induced Cargo Release Systems

Stable hollow-type microspheres (MSs) have been fabricated using α-synuclein (αS), an amyloidogenic protein, via freeze-induced protein self-assembly. This assembly process involves three steps: rapid freezing to form spherical protein condensates from αS oligomers, frozen annealing to form a crust on the condensate and freeze-drying to create an interior lumen via the three-dimensional (3D) coffee-stain effect. The crust produced during the frozen-annealing step is a β-sheet-mediated protein structure that is presumed to be created at the quasi-liquid layer of the protein-ice interface and thus contributes to the stability of MSs in aqueous solutions at room temperature without any additional surface stabilization. MSs transform into amyloid fibril condensates when heated to 70 °C, and the drug is loaded via centrifugal membrane filtration. Additionally, the MSs were shielded with an iron-alginate layer embedded with gold nanoparticles (AuNPs) to prevent premature leakage and to control drug release. This takes advantage of the photothermal effect of AuNPs, resulting in combined cytotoxicity between the drug and heat. Therefore, drug-loaded MSs comprising αS and AuNPs can be suggested as light-controllable drug delivery systems that exhibit chemical and physical anticancer therapeutic effects.

Considerations on the stability of IgG antibody in clinical specimens

The 1890s marked a significant milestone with the introduction of antibody-based agglutination and precipitation assays, revolutionizing the detection of bacterial pathogens in both animals and humans. This era also witnessed pivotal contributions to our understanding of humoral immunity, as researchers elucidated the structure and functions of antibody molecules, laying the groundwork for diagnostic applications. Among antibody isotypes, IgG is of paramount importance in diagnostic investigations given its definitive indication of infection or vaccination, coupled with its widespread presence and detectability across various specimen types, such as serum, colostrum, milk, oral fluids, urine, feces, and tissue exudate. Despite their resilience, immunoglobulins are susceptible to structural alterations induced by physicochemical and enzymatic processes, which can compromise the reliability of their detection. Here we review comprehensively the historical milestones, underlying mechanisms, and influencing factors (e.g., temperature, pH, storage) that shape the structural integrity and stability of IgG antibodies in aqueous solutions and various clinical specimens.

Optimization of continuous spin-freeze-drying: The role of spin-freezing on quality attributes and drying efficiency of a model peptide formulation

Continuous spin-freeze-drying is an innovative pharmaceutical manufacturing approach offering real-time monitoring and control at the individual vial level, unlike conventional batch lyophilization. A central feature of this technology is spin-freezing, which involves rapidly spinning liquid-filled vials under a precisely controlled cold gas flow, resulting in a thin, uniform frozen product layer. Using a model peptide formulation, we investigated the impact of different cooling and crystallization rates on quality attributes (QA) and primary drying duration. Key QAs included monomer content, peptide assay, moisture content, and pore structure. The monomer content, peptide content, and primary drying duration remained consistent across all spin-freezing conditions. However, scanning electron microscopy (SEM) and Karl Fischer titration revealed that freezing parameters significantly influenced pore structure and residual moisture content. Samples with smaller pores displayed lower residual moisture, as larger surface areas facilitate moisture desorption. Variations in freezing parameters also significantly impacted desorption kinetics during secondary drying. Slower crystallization rates led to more cracks and less shrinkage in the cake structure, while faster rates resulted in more uniform, stable cakes. Although specific to the product under study, these findings highlight the crucial role of spin-freezing in enhancing freeze-drying efficiency and product quality of biopharmaceuticals.

Inflammation biomarkers and Alzheimer's disease: A pilot study using NULISAseq

INTRODUCTION

Increasing evidence links amyloid beta (Aβ) aggregation with inflammation. This pilot study investigated the use of an immunoassay panel to map biomarker changes in patients with Alzheimer's disease (AD). Furthermore, we evaluated the stability of protein quantification after multiple freeze-thaw cycles (FTCs).

METHODS

The nucleic acid-linked immuno-sandwich assay (NULISA) inflammation panel measured 203 proteins in serum samples of individuals with (n = 31) and without (n = 31) AD pathology. Linear models, adjusted for age and sex, contrasted protein expression across groups.

RESULTS

After multiple-testing adjustments, glial fibrillary acidic protein (p < 0.001) and S100A12 (p < 0.001) were significantly changed in the presence of AD pathology. Furthermore, they correlated with cerebrospinal fluid biomarkers (phosphorylated tau-181 [p-tau181], tau, and Aβ42). Additional markers were nominally changed between groups. Five FTCs caused minimal changes in measurements with the NULISA inflammation panel.

DISCUSSION

Monitoring of inflammation in AD, using the 200-plex NULISA panel, demonstrates changes in peripherally circulating inflammation-related proteins. Contrary to previous reports, FTCs had minimal impact on the quantification of inflammatory markers.

Highlights

The novel nucleic acid-linked immuno-sandwich assay (NULISA) inflammation panel, which includes 200 protein biomarkers, was used.The panel was used for the first time in serum from patients with Alzheimer's disease (AD).The protein S100A12 was identified as a potential biomarker for AD.Inflammation markers were stable in up to five freeze-thaw cycles.

Practical advice in the development of a lyophilized protein drug product

The development of lyophilized protein drug products is a critical and complex task in the pharmaceutical industry, requiring a comprehensive understanding of the myriad of factors affecting product quality, stability, and the efficiency and robustness of the lyophilization process. This review offers practical advice on the critical aspects of lyophilized protein drug product development. Practical considerations across both the early and late stages of development are discussed, underscoring the necessity of a strategic approach from initial development through to commercialization. The review then delves into formulation optimization strategies that are essential for enhancing protein stability and the efficiency of the lyophilization process. This section outlines stable formulation design and highlights the unique considerations required for high protein concentration lyophilized drug products. It further explores the formulation strategies to enhance the lyophilization process' efficiency. Moreover, the paper examines the critical elements in selecting primary containers and closures for lyophilized drug products, focusing on vials and dual chamber systems. The analysis encompasses the effects of the container/closure's material, size, geometry, and fill volume on product quality and process efficiency. Lastly, the review provides practical considerations in lyophilization cycle development, including the design and optimization of the freezing, primary drying, and secondary drying stages to achieve a robust, scalable, and efficient lyophilization process. By offering comprehensive insights into these key areas to enhance their understanding and implementation of best practices in the field, this paper serves as a useful resource for researchers, formulators, and process engineers involved in the development of lyophilized protein drug products.

Purification of micrococcal nuclease for use in ribosomal profiling of high-salinity extremophiles

Nucleases, that is, enzymes that catalyze the hydrolysis of phosphodiester bonds in nucleic acids, are essential tools in molecular biology and biotechnology. Staphylococcus aureus nuclease is particularly interesting due to its thermostability and Ca2+ dependence, making it the prime choice for applications where nuclease modulation is critical, such as ribosome profiling in bacteria and halophilic archaea. The latter poses a technical and economical challenge: high salt reaction conditions are essential for maintaining ribosome integrity but negatively impact the micrococcal nuclease (MNase) activity, necessitating using large amounts of nuclease to achieve efficient cleavage. Here, we set out to generate an optimized production protocol for two forms of MNase-fully processed MNaseA and the 19 amino acid propeptide-containing MNaseB-and to biochemically benchmark them against a commercial nuclease. Our results show that both MNases are highly active in normal reaction conditions, but MNaseA maintains higher enzymatic activity in high salt concentrations than MNaseB. MNaseA also retains >90% of its activity after multiple freeze-thaw cycles when stored at -80 °C in a buffer containing 5% glycerol. Importantly, ribosome profiling experiments in the haloarchaeon Haloferax volcanii demonstrated that MNaseA produces ribosome footprints and hallmarks of active translation highly comparable to those obtained with the commercial nuclease, making it a suitable alternative for high-salt ribosome profiling applications. In conclusion, our method can be easily implemented for efficient MNaseA production, thereby providing access to an effective, robust, and cost-efficient alternative to commercial nucleases, as well as facilitating future translation studies into halophilic organisms.

Formulation development of a stable influenza recombinant neuraminidase vaccine candidate

Current influenza vaccines could be augmented by including recombinant neuraminidase (rNA) protein antigen to broaden protective immunity and improve efficacy. Toward this goal, we investigated formulation conditions to optimize rNA physicochemical stability. When rNA in sodium phosphate saline buffer (NaPBS) was frozen and thawed (F/T), the tetrameric structure transitioned from a "closed" to an "open" conformation, negatively impacting functional activity. Hydrogen deuterium exchange experiments identified differences in anchorage binding sites at the base of the open tetramer, offering a structural mechanistic explanation for the change in conformation and decreased functional activity. Change to the open configuration was triggered by the combined stresses of acidic pH and F/T. The desired closed conformation was preserved in a potassium phosphate buffer (KP), minimizing pH drop upon freezing and including 10% sucrose to control F/T stress. Stability was further evaluated in thermal stress studies where changes in conformation were readily detected by ELISA and size exclusion chromatography (SEC). Both tests were suitable indicators of stability and antigenicity and considered potential critical quality attributes (pCQAs). To understand longer-term stability, the pCQA profiles from thermally stressed rNA at 6 months were modeled to predict stability of at least 24-months at 5°C storage. In summary, a desired rNA closed tetramer was maintained by formulation selection and monitoring of pCQAs to produce a stable rNA vaccine candidate. The study highlights the importance of understanding and controlling vaccine protein structural and functional integrity.

Integrated lipidomics and microbiomics reveal the quality changes of fresh yak tenderloin during storage

The changes in lipid and microbial during beef storage exert a substantial impact on the overall quality of beef. In this study, lipidomics and microbiomics were used to evaluate the effects of chilled storage (at 4 °C, CS) and superchilled storage (at -2 °C, SS) on the quality of yak tenderloin. The data revealed that TG, PS, PI, PE, and Car are the key factors contributing to the generation of undesirable odor during the storage of tenderloin. Macrococcus, Lactobacillus, Myroides, and Proteobacteria directly affect the storage quality of yak tenderloin. Integrated analysis revealed that microbial metabolites interact with lipids, resulting in a deterioration of meat quality. These changes are mediated by Myroides, Pseudomonas, and Lactobacillus, which regulate fatty oxidation and metabolism of PE, PI, PS, Cer, and SM. These findings have important implications for understanding the changes in quality and microbial activity of refrigerated meat and meat products.

Particle formation in response to different protein formulations and containers: Insights from machine learning analysis of particle images

Subvisible particle count is a biotherapeutics stability indicator widely used by pharmaceutical industries. A variety of stresses that biotherapeutics are exposed to during development can impact particle morphology. By classifying particle morphological differences, stresses that have been applied to monoclonal antibodies (mAbs) can be identified. This study aims to evaluate common biotherapeutic drug storage and shipment conditions that are known to impact protein aggregation. Two different studies were conducted to capture particle images using micro-flow imaging and to classify particles using a convolutional neural network. The first study evaluated particles produced in response to agitation, heat, and freeze-thaw stresses in one mAb formulated in five different formulations. The second study evaluated particles from two common drug containers, a high-density polyethylene bottle and a glass vial, in six mAbs exposed solely to agitation stress. An extension of this study was also conducted to evaluate the impact of sequential stress exposure compared to exposure to one stress alone, on particle morphology. Overall, the convolutional neural network was able to classify particles belonging to a particular formulation or container. These studies indicate that storage and shipping stresses can impact particle morphology according to formulation composition and mAb.

Reconsidering freeze-induced protein aggregation: Air bubbles as the root cause of ice-water interface stress

Freeze-induced stress causing aggregation of proteins has typically been primarily attributed to the ice-water interface. However, we hypothesize that the underlying observed and perceived detrimental effect of ice is, to some extent, attributed to air bubbles expelled from ice crystal lattices or to nanobubbles existing prior to freezing. The reduction of dissolved air was achieved via a deaeration process by placing samples in a reduced pressure chamber, while the reduction of nanobubbles was achieved by filtering samples via a syringe filter. The results showed that the reduction of both dissolved air molecules and stable colloidal nanobubbles in a bovine IgG solution prior to freezing led to a significant decrease in aggregation after thawing compared to untreated samples (∼6,000 vs. ∼ 40,000 particles/mL at a freezing rate of 100 K/s, respectively). The deaeration-filtration treatment works additively with cryoprotectants such as trehalose, further reducing the freeze-induced aggregation of IgG. The results also demonstrated that air-water interfacial aggregation of IgG in bulk liquid samples is a time-dependent process. The number of IgG subvisible particles increased with time and temperature, suggesting that random collisions of denatured molecules promoted the formation of aggregates with spherical morphology. In contrast, the IgG subvisible count after freeze-thawing had already reached its nominal value, suggesting a time-independent process where denatured protein molecules were compressed between ice crystals into filament-like aggregates. In summary, the findings shift the current paradigm from ice crystals being the main destabilizing factor during freezing to air bubbles, although the two are intertwined. From a translational aspect, this study underscores the value of deaeration-filtration as an essential supplemental process that can be applied in addition to formulation approaches such as the use of cryoprotectants to further reduce freezing stress on proteins and increase their stability.

Effectiveness of Lyoprotectants in Protein Stabilization During Lyophilization

Background: Proteins are commonly used in the healthcare industry to treat various health conditions, and most proteins are sensitive to physical and chemical changes. Lyophilization, also known as freeze-drying, involves sublimating water in the form of ice from a substance at low pressure, forming a freeze-dried powder that increases its shelf life. Extreme pressure and varying temperatures in the freeze-drying process may damage the protein's structural integrity. Lyoprotectants are commonly used to protect protein conformations. It is important to choose a suitable lyoprotectant to ensure optimal effectiveness. Method: Twenty articles screened from Scopus, Web of Science, and PubMed were included in this review that discussed potential lyoprotectants and their effectiveness with different protein models. Results: Lyoprotectants were categorized into sugars, polyols, surfactants, and amino acids. Lyoprotectants can exhibit significant protective effects towards proteins, either singularly or in combination with another lyoprotectant. They exert various interactions with the protein to stabilize it, such as hydrogen bonding, hydrophobic interactions, electrostatic interactions, and osmoprotection. Conclusions: This review concludes that disaccharides are the most effective lyoprotectants, while other groups of lyoprotectants are best used in combination with other lyoprotectants.

Long term investigation of formulation buffers to mitigate stability issues of conjugated critical reagents

Stability of conjugated critical reagents supporting ligand binding assays to enable biotherapeutic drug development is a universal concern. Formulation buffer employed for long-term cold storage may be key to mitigate protein aggregation issues. We investigated biophysical and functional attributes of murine mAb and human multispecific drug labeled with biotin, ruthenium, and Alexa fluor 647 frozen at -80 °C in PBS or a protein storage buffer for 3-15 months. Aggregation was observed at 4 months in mAb A-Ru (11.2%) and -Alexa (10%) in PBS followed by precipitation and reduced biological binding at 15 months. Increased aggregation in drug Ru (11.7%, 6 months) and Alexa (6.9%, 15 months) were noted but without impact on performance. There were no observations with biotin labeled reagents.

Optimizing renal transporter immunodetection: consequences of freeze-thaw during sample preparation

Renal transporters (cotransporters, channels, and claudins) mediate homeostasis of fluids and electrolytes and are targets of hormonal and therapeutic regulators. Assessing renal transporter abundance with antibody probes by immunoblotting is an essential tool for mechanistic studies. Although journals require authors to demonstrate antibody specificity, there are no consensus guidelines for kidney sample preparation leading to lab-to-lab variability in immunoblot results. In this study, we determined the impact of sample preparation, specifically freeze-thawed (Frozen) versus freshly processed (Fresh) kidneys (female and male rats and mice) on immunoblot signal detection of 15 renal transporters and the impact of protease inhibitors during homogenization. In female Sprague-Dawley rat kidneys homogenized with aprotinin, Na2EDTA, PMSF, and phosphatase inhibitors, immunodetection signals were ∼50% lower in Frozen versus Fresh samples for most transporters. Inclusion of additional inhibitors (Roche cOmplete Protease Inhibitor, "+") only partially increased transporter immunoblot signals to near Fresh levels. In male Sprague-Dawley rats, immunoblot signal density was lower in Frozen+ versus Fresh+ despite additional inhibitors. In C57BL/6 male mice, immunoblot signals from proximal tubule transporters were lower in Frozen versus Fresh by ∼25-50% and greater in Frozen+. In contrast, immunodetection signal was equivalent in female Frozen+ versus female Fresh+ for claudin 2, villin, AQP1, NKCC2, NCC, ENaCβ, ENaCɣ, claudin 7, AQP2, NKAα1, and NKAβ1. Thus, kidney sample preparation variables, including freeze-thaw and protease inhibition, have substantial transporter-specific effects on quantification of renal transporter abundance by immunoblot. These findings underscore the critical importance of assessing and reporting the impact of sample preparation protocols on transporter recovery to ensure robust rigor and reproducibility. NEW & NOTEWORTHY Freeze-thawing kidneys before homogenization is widely accepted in renal research. This study demonstrates that if kidneys are freeze-thawed just once before homogenization, immunoblot signals are reduced in a transporter-specific manner in rats and mice dependent on sex and that immunoblot signals can be partially recovered by adding additional protease inhibitors. These findings underscore the critical importance of assessing the impact of sample preparation, including freeze-thaw versus fresh, to ensure robust rigor and reproducibility.

A comprehensive review on freeze-induced deterioration of frozen egg yolks: Freezing behaviors, gelation mechanisms, and control techniques

Over the years, the production of eggs has increased tremendously, with an estimated global egg production of 9.7 billion by 2050. Further processing of shell eggs to egg products has gained growing popularity. Liquid egg yolks, an innovative form of egg replacement, still suffer from short shelf-life issues, and freezing has been applied to maintain freshness. An undesirable phenomenon called "gelation" was found during the production of frozen egg yolks, which has attracted numerous scholars to study its mechanism and quality control methods. Therefore, we comprehensively reviewed the history of the studies on frozen egg yolks, including the production procedure, the fundamentals of freezing, the gelation mechanism, the factors affecting gelation behaviors, and the techniques to control the gelation behaviors of frozen egg yolks. Reporting the production procedure and freezing fundamentals of frozen egg yolks will give readers a better understanding of the science and technological aspects of frozen egg yolks. Furthermore, a comprehensive summary of the mechanism of egg yolk gel formation induced by freeze-thawing and relevant control techniques will provide insights to researchers and manufacturers in the field of frozen egg processing.

Validation and stability analysis of guanine deaminase assay kit

Guanine deaminase (GD)plays important roles in the diagnosis of liver function. However, there is no totally rapid and simple for the eatimation of GD activity in clinical application. Herein, we have constructed an enzymatic assay system with highly sensitive and strong stability for quantification of GD activity by highly double enzyme-coupling (xanthine oxidase and uric acid oxidase) and adding compound stabilizer in GD kit. In this study, we validated parameters, including reagent blank, sensitivity, accuracy, inter-batch difference, intra-batch difference, linear range. Furthermore, composite stabilizers, containing gentamicin sulfate, bovine serum albumin, and mannitol, were selected to improve stability of GD kit during long-term storage. The experimental results showed that the absorbance of the reagent blank was <0.2, the mean recovery rate was 103 %, the inter-batch and intra-batch diffeerence were <15 %, The linearity range was 0 U/L-50 U/L (R2 > 0.99). All indicators met the kit requirements for clinical applications. When gentamicin sulfate, bovine serum albumin, and mannitol were used as a stabilizer, the kit remained stable for 12 months without significant loss of enzymatic activity. These results indicated that GD kit possesses high sensitivity and strong stability, which can be used for routine biochemical applications and is of great significance for the diagnosis and differential diagnosis of liver diseases.

Cryomilled electrospun nanofiber mats containing d-mannitol exhibit suitable for aerosol delivery of proteins

Dry powder inhalers (DPIs) are the first choice for inhalation drug development. However, some conventional DPI formulation processes require heating, which may damage high molecular weight drugs such as proteins and nucleic acids. In this study, we propose a novel DPI preparation process that avoids the use of heat. Dry powders were prepared by cryomilling nanofiber mats composed of polyvinyl alcohol, D(-)-mannitol (Man), and α-chymotrypsin (α-Chy) as the model drug using the electrospinning method. The addition of Man conferred high dispersibility and excellent in vitro aerosol performance to the nanofiber mat powder in a very short milling time (less than 0.5 min) as assessed using the Andersen cascade impactor. Powders were classified according to the degree of friability, and among these, nanofiber mats containing 15 % Man and milled for 0.25 min exhibited the highest aerosol performance. Nanofiber mats containing Man milled for less than 0.5 min also exhibited greater α-Chy enzymatic activity than a nebulized α-Chy solution. Furthermore, single inhalation induced no significant lung tissue damage as evidenced by lactate dehydrogenase activity assays of mouse bronchoalveolar lavage fluid. This novel DPI formulation process may facilitate the safe and efficient inhalational delivery of therapeutic proteins.

Quantification of Residual Water in Pharmaceutical Frozen Solutions Via 1H Solid-State NMR

Freezing is essential for the stability of biological drug substances and products, particularly in frozen solution formulations and during the primary drying of lyophilized preparations. However, the unfrozen segment within the frozen matrix can alter solute concentration, ionic strength, and stabilizer crystallization, posing risks of increased biophysical instability and faster chemical degradation. While quantifying the unfrozen water content is important for designing stable biopharmaceuticals, there is a lack of analytical techniques for in situ quantitative measurements. In this study, we introduce a 1H magic angle spinning NMR technique to identify the freezing point (Tice) and quantify mobile water content in frozen biologics, applying this method to analyze the freezing of a commercial high-concentration drug product, Dupixent®. Our results demonstrate that water freezing is influenced by buffer salt properties and formulation composition, including the presence of sugar cryoprotectants and protein concentration. Additionally, the 1H chemical shift can probe pH in the unfrozen phase, potentially predicting the microenvironmental acidity in the frozen state. Our proposed methodology provides fresh insights into the analysis of freeze-concentrated solutions, enhancing our understanding of the stability of frozen and lyophilized biopharmaceuticals.

Drug product Formulation and Fill/Finish Manufacturing Process Considerations for AAV-Based Genomic Medicines

Adeno-associated viruses (AAVs) have become the delivery medium of choice for a variety of genomic medicine applications i.e., gene therapy, gene editing/regulation, and ex-vivo cell therapy. AAVs are protein-DNA complexes which have unique stability characteristics that are susceptible to various stress exposure conditions commonly seen in the drug product (DP) life cycle. This review takes a comprehensive look at AAV DP formulation and process development considerations that could impact critical quality attributes (CQAs) during manufacturing, packaging, shipping, and clinical use. Additional aspects related to AAV development reviewed herein are: (1) Different AAV serotypes with unique protein sequences and charge characteristics potentially leading to discrete stability profiles; (2) Manufacturing process challenges and optimization efforts to improve yield, recovery and purity especially during early development activities; and (3) Defining and identifying CQAs with analytical methods which are constantly evolving and present unique characterization challenges for AAV-based products.

The Non-Denatured Processing of Brasenia schreberi Mucilage-Characteristics of Hydrodynamic Properties and the Effect on In Vivo Functions

Food non-denatured processes, such as freeze-drying and grinding, are commonly applied to raw materials with good bioactive functions. Although the functional components are maintained, whether structural and physical changes impact the in vivo function is often ignored in practical situations. Brasenia schreberi mucilage (BSM) has a significant alleviation effect on DSS-induced colitis. This work focused on the influence of non-denatured manufacture on the colonic benefits of BSM-based products. First, three forms of products including fresh mucilage (FM), freeze-dried products (FS), and freeze-dried powder (FP) were prepared. Then, their in vitro physiochemical properties were compared, analyzing their influence on the gut inflammation degree, microbial composition, and SCFA production in mice. The results suggested that the water retention rate of FS and FP was decreased to 34.59 ± 3.85%, and 9.93 ± 1.76%. The viscosity of FM, FS, and FP was 20.14 Pa∙s, 4.92 Pa∙s, and 0.41 Pa∙s, respectively. The freeze-drying and grinding process also damaged the lamellar microstructure of BSM. Then, animal tests showed that colitis mice intervened with FM, FS, and FP had disease activity scores of 2.03, 3.95, and 4.62. Meanwhile, FM notably changed the gut microbial composition and significantly increased propionate and butyrate levels. It seemed that the distinct colitis alleviation efficacy of BSM-based products is attributed to different hydrodynamic properties in the gut. FM had relatively higher viscosity and correspondingly high nutritional density in the gut lumen, which stimulates Firmicutes growth and promotes butyrate production, and thereby exhibited the best efficiency on protecting from colitis.

The Influences of Cryopreservation Methods on RNA, Protein, Microstructure and Cell Viability of Skeletal Muscle Tissue

Background: Different experiments require different sample storage methods. The commonly used preservation methods in biobank practice cannot fully meet the multifarious requirements of experimental techniques. Programmable controlled slow freezing (PCSF) can maintain the viability of tissue. In this study, we hypothesized that PCSF-preserved samples have potential advantages in matching subsequent experiments compared with existing methods. Methods: We compared the differences on skeletal muscle tissue RNA integrity, protein integrity, microstructure integrity, and cell viability between four existing cryopreservation methods: liquid nitrogen (LN2) snap-freezing, LN2-cooled isopentane snap-freezing, RNAlater®-based freezing, and PCSF. RNA integrity was evaluated using agarose gel electrophoresis and RNA integrity number. Freezing-related microstructural damage in the muscle tissue was evaluated using ice crystal diameter and muscle fiber cross-sectional area. Protein integrity was evaluated using immunofluorescence staining. Cell viability was evaluated using trypan blue staining after primary muscle cell isolation. Results: PCSF preserved RNA integrity better than LN2 and isopentane, with a statistically significant difference. RNAlater preserved RNA integrity best. PCSF best controlled ice crystal size in myofibers, with a significant difference compared with LN2. The PCSF method best preserved the integrity of protein epitopes according to the mean fluorescence intensity results, with a significant difference. Cell viability was best preserved in the PCSF method compared with the other three methods, with a significant difference. Conclusion: PCSF protected the RNA integrity, microstructural integrity, protein integrity, and cell viability of skeletal muscle tissue. The application of PCSF in biobank practice is recommended as a multi-experiment-compatible cryopreservation method.

Insights into Thermal Interactions in Frozen Pharmaceutical Vials: Effects on Ice Nucleation Times and Inhibition

PURPOSE

This study investigates the thermal interactions between adjacent vials during freezing and assesses their impact on nucleation times.

METHODS

Various loading configurations were analyzed to understand their impact on nucleation times. Configurations involving direct contact between vials and freeze-dryer shelves were studied, along with setups using empty vials between filled ones. Additionally, non-conventional loading configurations and glycol-filled vials were tested. The analysis includes 2R and 20R vials, which are commonly utilized in the freezing and lyophilization of drug products, along with two different fill depths, 1 and 1.4 cm.

RESULTS

The investigation revealed that configurations with direct contact between vials and freeze-dryer shelves led to substantial thermal interactions, resulting in delayed nucleation in adjacent vials and affecting the temperature at which nucleation takes place in a complex way. In another setup, empty vials were placed between filled vials, significantly reducing thermal interactions. Further tests with non-conventional configurations and glycol-filled vials confirmed the presence of thermal interactions with a minimal inhibitory effect.

CONCLUSIONS

These findings carry significant implications for the pharmaceutical industry, highlighting the role of thermal interactions among vials during freezing and their impact on the temperature at which ice nucleation occurs.

Probing Chemical Equilibrium in Frozen Sodium Phosphate Buffer Solution by 31P Solid-State NMR

Phosphate buffers are crucial for cryopreservative stability in pharmaceuticals, food processing, biomedical sciences, and biology. However, their freeze concentrates lack quantitative characterization, especially regarding the physicochemical properties of phosphate salt species in equilibrium at subzero temperatures. This study employs 31P solid-state NMR (ssNMR) to analyze frozen sodium phosphate (NaP) solutions, providing insights into phase composition, ionic strength, and pH. For the first time, we have directly quantified phosphate species in frozen NaP buffer, including crystallized disodium phosphate dodecahydrate (Na2HPO4·12H2O) content and the concentrations of H2PO4- and HPO42- in the freeze concentrate. This enabled the calculation of the pH as well as the ionic strength in the freeze concentrate. Trehalose effectively mitigated pH shifts in buffer solutions by preventing the selective crystallization of salt, a spectroscopic phenomenon not previously observed experimentally.

Characterization of Freezing Processes in Drug Substance Bottles by Ice Core Sampling

Freezing of biological drug substance (DS) is a critical unit operation that may impact product quality, potentially leading to protein aggregation and sub-visible particle formation. Cryo-concentration has been identified as a critical parameter to impact protein stability during freezing and should therefore be minimized. The macroscopic cryo-concentration, in the following only referred to as cryo-concentration, is majorly influenced by the freezing rate, which is in turn impacted by product independent process parameters such as the DS container, its size and fill level, and the freezing equipment. (At-scale) process characterization studies are crucial to understand and optimize freezing processes. However, evaluating cryo-concentration requires sampling of the frozen bulk, which is typically performed by cutting the ice block into pieces for subsequent analysis. Also, the large amount of product requirement for these studies is a major limitation. In this study, we report the development of a simple methodology for experimental characterization of frozen DS in bottles at relevant scale using a surrogate solution. The novel ice core sampling technique identifies the axial ice core in the center to be indicative for cryo-concentration, which was measured by osmolality, and concentrations of histidine and polysorbate 80 (PS80), whereas osmolality revealed to be a sensitive read-out. Finally, we exemplify the suitability of the method to study cryo-concentration in DS bottles by comparing cryo-concentrations from different freezing protocols (-80°C vs -40°C). Prolonged stress times during freezing correlated to a higher extent of cryo-concentration quantified by osmolality in the axial center of a 2 L DS bottle.

Freeze-drying revolution: unleashing the potential of lyophilization in advancing drug delivery systems

Lyophilization also known as freeze-drying is a technique that has been employed to enhance the long-term durability of nanoparticles (NPs) that are utilized for drug delivery applications. This method is used to prevent their instability in suspension. However, this dehydration process can cause stress to the NPs, which can be alleviated by the incorporation of excipients like cryoprotectants and lyoprotectants. Nevertheless, the freeze-drying of NPs is often based on empirical principles without considering the physical-chemical properties of the formulations and the engineering principles of freeze-drying. For this reason, it is crucial to optimize the formulations and the freeze-drying cycle to obtain a good lyophilizate and ensure the preservation of NPs stability. Moreover, proper characterization of the lyophilizate and NPs is of utmost importance in achieving these goals. This review aims to update the recent advancements, including innovative formulations and novel approaches, contributing to the progress in this field, to obtain the maximum stability of formulations. Additionally, we critically analyze the limitations of lyophilization and discuss potential future directions. It addresses the challenges faced by researchers and suggests avenues for further research to overcome these limitations. In conclusion, this review is a valuable contribution to the understanding of the parameters involved in the freeze-drying of NPs. It will definitely aid future studies in obtaining lyophilized NPs with good quality and enhanced drug delivery and therapeutic benefits.

How spray drying processing and solution composition can affect the mAbs stability in reconstituted solutions for subcutaneous injections. Part I: Contribution of processing stresses against composition

Spray drying is increasingly being applied to process biopharmaceuticals, particularly monoclonal antibodies (mAbs). However, due to their protein nature, mAbs are susceptible to degradation when subjected to various stresses during a drying process. Despite extensive research in this domain, identifying the appropriate formulation composition and spray drying conditions remains a complex challenge, requiring further studies to enhance the understanding on how process and formulation parameters impact mAb stability in reconstituted solutions. This research aims to explore spray drying as technique for producing pharmaceutical mAbs-based powders intended for reconstitution and subcutaneous injection. In the initial phase of this study, using a model mAb (mAb-A), the influence of dissociated and coupled process stresses on protein stability after solution reconstitution was investigated. The findings revealed a detrimental interplay of mechanical, interfacial, and thermal/dehydration stresses on mAb-A stability, notably characterized by an increase in protein aggregation. Subsequently, in a second phase, the study delved into the impact of spray drying processing conditions, the level of excipients, and protein concentration on mAb-A aggregation in reconstituted solutions. The obtained results highlighted the critical role of formulation composition as a parameter deserving further study, specifically concerning the selection of type and concentration of stabilizers to be added in the liquid mAb-A solution to be dried.

Potential of a Bead-Based Multiplex Assay for SARS-CoV-2 Antibody Detection

Serological assays for SARS-CoV-2 play a pivotal role in the definition of whether patients are infected, the understanding of viral epidemiology, the screening of convalescent sera for therapeutic and prophylactic purposes, and in obtaining a better understanding of the immune response towards the virus. The aim of this study was to investigate the performance of a bead-based multiplex assay. This assay allowed for the simultaneous testing of IgG antibodies against SARS-CoV-2 spike, S1, S2, RBD, and nucleocapsid moieties and S1 of seasonal coronaviruses hCoV-22E, hCoV-HKU1, hCoV-NL63, and hCoV-OC43, as well as MERS and SARS-CoV. We compared the bead-based multiplex assay with commercial ELISA tests. We tested the sera of 27 SARS-CoV-2 PCR-positive individuals who were previously tested with different ELISA assays. Additionally, we investigated the reproducibility of the results by means of multiple testing of the same sera. Finally, the results were correlated with neutralising assays. In summary, the concordance of the qualitative results ranged between 78% and 96% depending on the ELISA assay and the specific antigen. Repeated freezing-thawing cycles resulted in reduced mean fluorescence intensity, while the storage period had no influence in this respect. In our test cohort, we detected up to 36% of sera positive for the development of neutralising antibodies, which is in concordance with the bead-based multiplex and IgG ELISA.

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.

Monitoring Aqueous Sucrose Solutions Using Droplet Microfluidics: Ice Nucleation, Growth, Glass Transition, and Melting

Freezing and freeze-drying processes are commonly used to extend the shelf life of drug products and to ensure their safety and efficacy upon use. When designing a freezing process, it is beneficial to characterize multiple physicochemical properties of the formulation, such as nucleation rate, crystal growth rate, temperature and concentration of the maximally freeze-concentrated solution, and melting point. Differential scanning calorimetry has predominantly been used in this context but does have practical limitations and is unable to quantify the kinetics of crystal growth and nucleation. In this work, we introduce a microfluidic technique capable of quantifying the properties of interest and use it to investigate aqueous sucrose solutions of varying concentration. Three freeze-thaw cycles were performed on droplets with 75-μm diameters at cooling and warming rates of 1 °C/min. During each cycle, the visual appearance of the droplets was optically monitored as they experienced nucleation, crystal growth, formation of the maximally freeze-concentrated solution, and melting. Nucleation and crystal growth manifested as increases in droplet brightness during the cooling phase. Heating was associated with a further increase as the temperature associated with the maximally freeze-concentrated solution was approached. Heating beyond the melting point corresponded to a decrease in brightness. Comparison with the literature confirmed the accuracy of the new technique while offering new visual data on the maximally freeze-concentrated solution. Thus, the microfluidic technique presented here may serve as a complement to differential scanning calorimetry in the context of freezing and freeze-drying. In the future, it could be applied to a plethora of mixtures that undergo such processing, whether in pharmaceutics, food production, or beyond.

Development of Lyophilized Eukaryotic Cell-Free Protein Expression System Based on Leishmania tarentolae

Eukaryotic cell-free protein expression systems enable rapid production of recombinant multidomain proteins in their functional form. A cell-free system based on the rapidly growing protozoan Leishmania tarentolae (LTE) has been extensively used for protein engineering and analysis of protein interaction networks. However, like other eukaryotic cell-free systems, LTE deteriorates at ambient temperatures and requires deep freezing for transport and storage. In this study, we report the development of a lyophilized version of LTE. Use of lyoprotectants such as poly(ethylene glycol) and trehalose during the drying process allows retention of 76% of protein expression activity versus nonlyophilized controls. Lyophilized LTE is capable of withstanding storage at room temperature for over 2 weeks. We demonstrated that upon reconstitution the lyophilized LTE could be used for in vitro expression of active enzymes, analysis of protein-protein interactions by AlphaLISA assay, and functional analysis of protein biosensors. Development of lyophilized LTE lowers the barriers to its distribution and opens the door to its application in remote areas.

Impact of secondary ice in a frozen NaCl freeze-concentrated solution on the extent of methylene blue aggregation

Freezing and lyophilization have been utilized for decades to stabilize pharmaceutical and food products. Freezing a solution that contains dissolved salt and/or organic matter produces pure primary ice crystal grains separated by freeze-concentrated solutions (FCS). The microscopic size of the primary ice crystals depends on the cooling conditions and the concentration of the solutes. It is generally accepted that primary ice crystals size influences the rate of sublimation and also can impact physico-chemical behaviour of the species in the FCS. This article, however, presents a case where the secondary ice formed inside the FCS plays a critical role. We microscoped the structures of ice-cast FCS with an environmental scanning electron microscope and applied the aggregation-sensitive spectroscopic probe methylene blue to determine how the microstructure affects the molecular arrangement. We show that slow cooling at -50 °C produces large salt crystals with a small specific surface, resulting in a high degree of molecular aggregation within the FCS. In contrast, fast liquid nitrogen cooling yields an ultrafine structure of salt crystals having a large specific surface area and, therefore, inducing smaller aggregation. The study highlights a critical role of secondary ice in solute aggregation and introduces methylene blue as a molecular probe to investigate freezing behaviour of aqueous systems with crystalline solute.

Screening and Stability Evaluation of Freeze-Dried Protective Agents for a Live Recombinant Pseudorabies Virus Vaccine

Infection of pigs with the pseudorabies virus (PRV) causes significant economic losses in the pig industry. Immunization with live vaccines is a crucial aspect in the prevention of pseudorabies in swine. The TK/gE/gI/11k/28k deleted pseudorabies vaccine is a promising alternative for the eradication of epidemic pseudorabies mutant strains. This study optimized the lyophilization of a heat-resistant PRV vaccine to enhance the quality of a live vaccine against the recombinant PRV rHN1201TK-/gE-/gI-/11k-/28k-. The A4 freeze-dried protective formulation against PRV was developed by comparing the reduction in virus titer after lyophilization and after seven days of storage at 37 °C. The formulation contains 1% gelatin, 5% trehalose, 0.5% poly-vinylpyrimidine (PVP), 0.5% thiourea, and 1% sorbitol. The A4 freeze-dried vaccine demonstrated superior protection and thermal stability. It experienced a freeze-dried loss of 0.31 Lg post-freeze-drying and a heat loss of 0.42 Lg after being stored at a temperature of 37 °C for 7 consecutive days. The A4 freeze-dried vaccine was characterized through XRD, FTIR, and SEM analyses, which showed that it possessed an amorphous structure with a consistent porous interior. The trehalose component of the vaccine formed stable hydrogen bonds with the virus. Long-term and accelerated stability studies were also conducted. The A4 vaccine maintained viral titer losses of less than 1.0 Lg when exposed to 25 °C for 90 days, 37 °C for 28 days, and 45 °C for 7 days. The A4 vaccine had a titer loss of 0.3 Lg after storage at 2-8 °C for 24 months, and a predicted shelf life of 6.61 years at 2-8 °C using the Arrhenius equation. The A4 freeze-dried vaccine elicited no side effects when used to immunize piglets and produced specific antibodies. This study provides theoretical references and technical support to improve the thermal stability of recombinant PRV rHN1201TK-/gE-/gI-/11k-/28k- vaccines.

Stabilization challenges and aggregation in protein-based therapeutics in the pharmaceutical industry

Protein-based therapeutics have revolutionized the pharmaceutical industry and become vital components in the development of future therapeutics. They offer several advantages over traditional small molecule drugs, including high affinity, potency and specificity, while demonstrating low toxicity and minimal adverse effects. However, the development and manufacturing processes of protein-based therapeutics presents challenges related to protein folding, purification, stability and immunogenicity that should be addressed. These proteins, like other biological molecules, are prone to chemical and physical instabilities. The stability of protein-based drugs throughout the entire manufacturing, storage and delivery process is essential. The occurrence of structural instability resulting from misfolding, unfolding, and modifications, as well as aggregation, poses a significant risk to the efficacy of these drugs, overshadowing their promising attributes. Gaining insight into structural alterations caused by aggregation and their impact on immunogenicity is vital for the advancement and refinement of protein therapeutics. Hence, in this review, we have discussed some features of protein aggregation during production, formulation and storage as well as stabilization strategies in protein engineering and computational methods to prevent aggregation.

HER2-specific liposomes loaded with proteinaceous BRET pair as a promising tool for targeted self-excited photodynamic therapy

Photodynamic therapy (PDT) for deep-seated tumors is still challenging due to the limited penetration of visible light through tissues. To resolve this limitation, systems based on bioluminescence resonance energy transfer (BRET), that do not require an external light source are proposed. Herein, for BRET-activated PDT we developed proteinaceous BRET-pair consisting of luciferase NanoLuc, which acts as energy donor upon addition of luciferase specific substrate furimazine, and phototoxic protein SOPP3 as a photosensitizer. We have shown that hybrid protein NanoLuc-SOPP3 is an excellent BRET pair with BRET ratio of 1.12. Targeted delivery of NanoLuc-SOPP3 BRET pair via tumor-specific small liposomes (∼100 nm) to tumors overexpressing the HER2-receptor (human epidermal growth factor receptor 2) was demonstrated in vitro and in vivo. The proposed BRET-activated system has been shown to significantly suppress tumor growth in a model of subcutaneous and, more importantly, deep-seated tumor model. Taking into account the in vivo efficiency of proposed BRET-activated system, we believe that it has great potential for depth-independent PDT and can significantly broaden the application of PDT in the clinic.

Application of Formulation Principles to Stability Issues Encountered During Processing, Manufacturing, and Storage of Drug Substance and Drug Product Protein Therapeutics

The field of formulation and stabilization of protein therapeutics has become rather extensive. However, most of the focus has been on stabilization of the final drug product. Yet, proteins experience stress and degradation through the manufacturing process, starting with fermentaition. This review describes how formulation principles can be applied to stabilize biopharmaceutical proteins during bioprocessing and manufacturing, considering each unit operation involved in prepration of the drug substance. In addition, the impact of the container on stabilty is discussed as well.

Screening of Cyclodextrins in the Processing of Buserelin Dry Powders for Inhalation Prepared by Spray Freeze-Drying

Purpose

In this study, we prepared inhalable buserelin microparticles using the spray freeze-drying (SFD) method for pulmonary drug delivery. Raffinose as a cryoprotectant carrier was combined with two levels of five different cyclodextrins (CDs) and then processed by SFD.

Methods

Dry powder diameters were evaluated by laser light scattering and morphology was determined by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were utilized for the determination of crystalline structures. The aerodynamic properties of the spray freeze-dried powders were evaluated by twin stage impinger (TSI) and the stability of prepared samples was assessed under normal and accelerated conditions.

Results

The prepared powders were mostly porous spheres and the size of microparticles ranged from 9.08 to 13.53 μm, which are suitable as spray-freeze dried particles. All formulations showed amorphous structure confirmed by DSC and XRD. The aerosolization performance of the formulation containing buserelin, raffinose and 5% beta-cyclodextrin (β-CD), was the highest and its fine particle fraction (FPF) was 69.38%. The more circular and separated structures were observed in higher concentrations of CDs, which were compatible with FPFs. The highest stability was obtained in the formulation containing hydroxypropyl beta-cyclodextrin (HP-β-16. CD) 5%. On the contrary, sulfobutylether beta-cyclodextrin (SBE-β-CD) 5% bearing particles showed the least stability.

Conclusion

By adjusting the type and ratio of CDs in the presence of raffinose, the prepared formulations could effectively enhance the aerosolization and stability of buserelin. Therefore, they can be proposed as a suitable career for lung drug delivery.

Assessment of sample freezing as a preservation technique for analysing the molecular composition of dissolved organic matter in aquatic systems

Dissolved organic matter (DOM) is widely studied in environmental and biogeochemical sciences, but is susceptible to chemical and biological degradation during sample transport and storage. Samples taken in remote regions, aboard ships, or in large numbers need to be preserved for later analysis without changing DOM composition. Here we compare high-resolution mass spectra of solid phase extractable DOM before and after freezing at -20 °C. We found that freezing increases compositional dissimilarity in DOM by between 0 to 18.2% (median = 2.7% across 7 sites) when comparing replicates that were frozen versus unfrozen, i.e., processed immediately after sampling, as compared with differences between unfrozen replicates. The effects of freezing primarily consisted of a poorer detection limit, but were smaller than other sample preparation and analysis steps, such as solid phase extraction and variable ionisation efficiency. Freezing samples for either 21 or 95 days led to similar and only slight changes in DOM composition, albeit with more variation for the latter. Therefore, we conclude that sample freezing on these time scales should not impede scientific study of aquatic DOM and can be used where it makes logistical sense, such as for large spatial surveys or study of archived samples.

Characterizing Silicone Oil-Induced Protein Aggregation with Stimulated Raman Scattering Imaging

Particles in biopharmaceutical products present high risks due to their detrimental impacts on product quality and safety. Identification and quantification of particles in drug products are important to understand particle formation mechanisms, which can help develop control strategies for particle formation during the formulation development and manufacturing process. However, existing analytical techniques such as microflow imaging and light obscuration measurement lack the sensitivity and resolution to detect particles with sizes smaller than 2 μm. More importantly, these techniques are not able to provide chemical information to determine particle composition. In this work, we overcome these challenges by applying the stimulated Raman scattering (SRS) microscopy technique to monitor the C-H Raman stretching modes of the proteinaceous particles and silicone oil droplets formed in the prefilled syringe barrel. By comparing the relative signal intensity and spectral features of each component, most particles can be classified as protein-silicone oil aggregates. We further show that morphological features are poor indicators of particle composition. Our method has the capability to quantify aggregation in protein therapeutics with chemical and spatial information in a label-free manner, potentially allowing high throughput screening or investigation of aggregation mechanisms.

Effect of Freezing on Soybean Protein Solution

To investigate the impact of frozen storage conditions on the physicochemical properties of soybean protein and explore the underlying mechanisms, this study focused on soybean isolate (SPI), ß-soybean companion globulin (7S), and soybean globulin (11S). The protein solutions were prepared at a concentration of 2% and subjected to freezing for 1 and 5 days. Subsequently, the protein content, physicochemical properties, secondary structure, sulfhydryl content, and chemical interaction forces were assessed and analyzed using UV spectrophotometry, Zeta potential measurements, SDS-PAGE, Fourier infrared spectroscopy, and endogenous fluorescence photoemission spectroscopy. The obtained results revealed that the solubility and total sulfhydryl content of SPI, 7S, and 11S exhibited a decreasing trend with prolonged freezing time. Among them, 11S demonstrated the largest decrease in solubility and total sulfhydryl content, followed by SPI, and 7S the least. During freezing, the aromatic amino acids of SPI, 7S, and 11S molecules were exposed, leading to increased hydrophobicity, protein aggregation, and particle size enlargement, and the structure of the protein changed from disordered structure to ordered structure. After freezing, the polarity of the microenvironment of SPI, 7S, and 11S increased, and their maximum fluorescence emission wavelengths were red-shifted. Notably, the largest red shift of SPI was from 332 nm to 335 nm. As freezing time increased, the contribution of hydrogen bonding increased, while the contribution of hydrophobic interactions decreased. This indicates that freezing affects the hydrophobic interactions, hydrogen bonding, and other chemical forces of the protein. The growth of ice crystals leads to the unfolding of protein molecular chains, exposure of internal hydrophobic groups, enhancement of hydrophobicity, and alters the secondary structure of the protein.

From Whispering Gallery Mode Resonators to Biochemical Sensors

Optical biosensors are frontrunners for the rapid and real-time detection of analytes, particularly for low concentrations. Among them, whispering gallery mode (WGM) resonators have recently attracted a growing focus due to their robust optomechanical features and high sensitivity, measuring down to single binding events in small volumes. In this review, we provide a broad overview of WGM sensors along with critical advice and additional "tips and tricks" to make them more accessible to both biochemical and optical communities. Their structures, fabrication methods, materials, and surface functionalization chemistries are discussed. We propose this reflection under a pedagogical approach to describe and explain these biochemical sensors with a particular focus on the most recent achievements in the field. In addition to highlighting the advantages of WGM sensors, we also discuss and suggest strategies to overcome their current limitations, leaving room for further development as practical tools in various applications. We aim to provide new insights and combine different knowledge and perspectives to advance the development of the next generation of WGM biosensors. With their unique advantages and compatibility with different sensing modalities, these biosensors have the potential to become major game changers for biomedical and environmental monitoring, among many other relevant target applications.

Enabling Efficient Design of Biological Formulations Through Advanced Characterization

The present review summarizes the use of differential scanning calorimetry (DSC) and scattering techniques in the context of protein formulation design and characterization. The scattering techniques include wide angle X-ray diffractometry (XRD), small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). While DSC is valuable for understanding thermal behavior of the excipients, XRD provides critical information about physical state of solutes during freezing, annealing and in the final lyophile. However, as these techniques lack the sensitivity to detect biomolecule-related transitions, complementary characterization techniques such as small-angle scattering can provide valuable insights.

Crystal structure of a putative 3-hydroxypimelyl-CoA dehydrogenase, Hcd1, from Syntrophus aciditrophicus strain SB at 1.78 Å resolution

Syntrophus aciditrophicus strain SB is a model syntroph that degrades benzoate and alicyclic acids. The structure of a putative 3-hydroxypimelyl-CoA dehydrogenase from S. aciditrophicus strain SB (SaHcd1) was resolved at 1.78 Å resolution. SaHcd1 contains sequence motifs and structural features that belong to the short-chain dehydrogenase/reductase (SDR) family of NADPH-dependent oxidoreductases. SaHcd1 is proposed to concomitantly reduce NAD+ or NADP+ to NADH or NADPH, respectively, while converting 3-hydroxypimelyl-CoA to 3-oxopimeyl-CoA. Further enzymatic studies are needed to confirm the function of SaHcd1.

Frozen fresh blood plasma preserves the functionality of native human α2-macroglobulin

Human α₂-macroglobulin (hα₂M) is a large homotetrameric protein involved in the broad inhibition of endopeptidases. Following cleavage within a bait region, hα₂M undergoes stepwise transitions from its native, expanded, highly flexible, active conformation to an induced, compact, triggered conformation. As a consequence, the peptidase is entrapped by an irreversible Venus flytrap mechanism. Given the importance of hα₂M, biochemical studies galore over more than seven decades have attempted to ascertain its role, typically using authentic hα₂M purified from frozen and non-frozen fresh blood plasma, and even outdated plasma. However, hα₂M is sensitive once isolated and purified, and becomes heterogeneous during storage and/or freezing, raising concerns about the functional competence of frozen plasma-derived hα₂M. We therefore used a combination of native and sodium dodecylsulfate polyacrylamide gel electrophoresis, affinity and ion-exchange chromatography, multi-angle laser light scattering after size-exclusion chromatography, free cysteine quantification, and peptidase inhibition assays with endopeptidases of two catalytic classes and three protein substrates, to characterize the biochemical and biophysical properties of hα₂M purified ad hoc either from fresh plasma or frozen fresh plasma after thawing. We found no differences in the molecular or functional properties of the preparations, indicating that protective components in plasma maintain native hα₂M in a functionally competent state despite freezing.

Lyophilization for Formulation Optimization of Drug-Loaded Thermoresponsive Polyelectrolyte Complex Nanogels from Functionalized Hyaluronic Acid

The lyophilization of nanogels is practical not only for their long-term conservation but also for adjusting their concentration and dispersant type during reconstitution for different applications. However, lyophilization strategies must be adapted to each kind of nanoformulation in order to minimize aggregation after reconstitution. In this work, the effects of formulation aspects (i.e., charge ratio, polymer concentration, thermoresponsive grafts, polycation type, cryoprotectant type, and concentration) on particle integrity after lyophilization and reconstitution for different types of polyelectrolyte complex nanogels (PEC-NGs) from hyaluronic acid (HA) were investigated. The main objective was to find the best approach for freeze-drying thermoresponsive PEC-NGs from Jeffamine-M-2005-functionalized HA, which has recently been developed as a potential platform for drug delivery. It was found that freeze-drying PEC-NG suspensions prepared at a relatively low polymer concentration of 0.2 g.L−1 with 0.2% (m/v) trehalose as a cryoprotectant allow the homogeneous redispersion of PEC-NGs when concentrated at 1 g.L−1 upon reconstitution in PBS without important aggregation (i.e., average particle size remaining under 350 nm), which could be applied to concentrate curcumin (CUR)-loaded PEC-NGs for optimizing CUR content. The thermoresponsive release of CUR from such concentrated PEC-NGs was also reverified, which showed a minor effect of freeze-drying on the drug release profile.

Freezing process influences cake appearance of a lyophilized amorphous protein formulation with low solid content and high fill configuration

Low solid content and high fill drug product configuration pose special challenges for achieving elegant cake appearance after lyophilization. In this study, such a configuration for a protein formulation required lyophilization within a narrow primary drying operating space to obtain elegant cakes. Freezing process optimization was explored as a solution. A Design of Experiment (DoE) approach was used to evaluate the effect of shelf cooling rate, annealing temperature, and their interaction on cake appearance. The slope of product resistance (R_p) vs. dried layer thickness (L_dry) was used as the quantitative response because elegant cake appearance correlated with a lower initial R_p and positive slope. As the R_p vs. L_dry slope can be experimentally established within the first 1/6th of the total primary drying duration, partial lyophilization runs were executed, allowing for rapid screening. The DoE model revealed that a slow cooling rate (≤0.3 °C/min) and high annealing temperature (≥-10 °C) resulted in a better cake appearance. Furthermore, X-ray micro-computed tomography showed that elegant cakes exhibited uniform porous structure and larger pores, while inelegant cakes showed dense top layers with smaller pores. With the optimized freezing process, the primary drying operating space was broadened with improved cake appearance and batch homogeneity.

Potential of Good's buffers to inhibit denaturation of myofibrillar protein upon freezing

The current systematic study sought to examine the potential use of three Good's buffers (MES, MOPS and HEPES) in inhibiting myofibrillar protein (MFP) denaturation induced by acidity changes. The highest degree of acidity variation was found in the center and bottom of large bottles due to the freeze-concentration effect. Good's buffer tended to basify during freezing, and it could prevent the crystallization of sodium phosphate (Na-P) buffer. Acidification upon freezing Na-P disrupted the natural conformation of MFP and induced the formation of large proteins aggregates with tight packing. The 15 mM MES, 20 mM MOPS, and 30 mM HEPES were respectively added to neutralize the strong acidity drop induced by freezing 20 mM Na-P, and all of them significantly improved the stability of the MFP conformation (P < 0.05). This work is not only critical to meet the growing demand for protein, but also groundbreaking for broadening the applicability of Good's buffers in the food industry.