Protein aggregation—Pathways and influencing factors

Unveiling the critical pH values triggering the unfolding of soy 7S and 11S globulins and enhancing their encapsulation efficiency

The pH-shifting process is an effective encapsulation method, and it is typically performed at extreme alkaline pH, which severely limits the application. In this study, we found that there were critical pH for the unfolding proteins during pH-shifting from 7 to 12, and upon the critical pH, physiochemical characteristics of protein greatly changed, leading to a sharp increase of encapsulation of hydrophobic actives. Firstly, the critical pH for β-conglycinin (7S) or Glycinin (11S) unfolding was determined by multispectral technology. The critical pH for 7S and 11S were 10.5 and 10.3, respectively. The encapsulation efficiency (EE) obtained by β-conglycinin-curcumin nanocomposite (7S-Cur) (88.80 %) and Glycinin-curcumin nanocomposite (11S-Cur) (88.38 %) at critical pH was significantly higher than that obtained by pH 7 (7S-Cur = 16.66 % and 11S-Cur = 15.78 %), and both values were close to EE obtained by at 12 (7S-Cur = 95.16 % and 11S-Cur = 94.63 %). The large-scale application of hydrophobic functional compounds will be enhanced by the experimental results.

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Growing Glycans in Rosetta: Accurate de novo glycan modeling, density fitting, and rational sequon design

Carbohydrates and glycoproteins modulate key biological functions. However, experimental structure determination of sugar polymers is notoriously difficult. Computational approaches can aid in carbohydrate structure prediction, structure determination, and design. In this work, we developed a glycan-modeling algorithm, GlycanTreeModeler, that computationally builds glycans layer-by-layer, using adaptive kernel density estimates (KDE) of common glycan conformations derived from data in the Protein Data Bank (PDB) and from quantum mechanics (QM) calculations. GlycanTreeModeler was benchmarked on a test set of glycan structures of varying lengths, or "trees". Structures predicted by GlycanTreeModeler agreed with native structures at high accuracy for both de novo modeling and experimental density-guided building. We employed these tools to design de novo glycan trees into a protein nanoparticle vaccine to shield regions of the scaffold from antibody recognition, and experimentally verified shielding. This work will inform glycoprotein model prediction, glycan masking, and further aid computational methods in experimental structure determination and refinement.

Aggregation structure induced by heat treatments mediated the gastric digestion behavior of soybean protein

The common belief that heat treatment enhances the gastric digestion of proteins is largely based on findings from animal proteins and may not apply to all proteins, particularly plant proteins. Here, we compared the digestion characteristics of soybean protein isolates (SPI) in an in vitro semi-dynamic digestion model and found distinct effects of heat treatment on the digestion properties of plant proteins. The results revealed that heat-treated SPIs formed clots during the early stages of digestion, although the clots gradually became smaller and looser as digestion progressed, the systems remained turbid at the end of gastric digestion, indicating the lag in their emptying. Furthermore, heat treatment altered the rheological properties of SPI, resulting in increased viscosity and slower gastric emptying. These effects became more pronounced with increasing heat treatment temperatures. The fluorescence spectrum analysis indicated that heat treatment altered its conformation. This led to protein unfolding and exposure of hydrophobic groups, facilitating the formation of larger aggregates during digestion. Additionally, heat treatment exposed more cleavage sites for gastric proteases, increasing the extent of hydrolysis. Elevated levels of free amino acids and a smaller molecular weight distribution further corroborated these findings. These findings contribute to a deeper understanding of the gastric digestion characteristics of plant proteins and the relationship between protein aggregation structure and the digestion process.

The Effects of Slaughter Methods and Drying Temperatures on the Protein Hydrolysis of Black Soldier Fly Larvae Meal

In recent years, the potential of insects as a sustainable protein alternative to feed the growing world population has been explored. Differences in the ways insects are processed can affect their proximate composition and digestibility. This work studied the effects of the combination of different types of slaughter methods and drying temperatures on the proximate composition, organic matter digestibility (OMd), hydrolysis degree (DH/NH2 and DH/100 g DM), total hydrolysis (TH), and hygienic and sanitary characteristics of BSFL (black soldier fly larvae) meal. Four types of slaughter methods were used including freezing (F), blanching + freezing (B), Melacide® + freezing (M), and liquid nitrogen slaughter (N). Each of these was used with three drying temperatures (50, 70, and 90 °C). A negative correlation between the acid detergent fiber (ADF) and protein digestibility parameters was obtained. The most suitable drying temperature was 70 °C, as it produced higher values of protein digestibility (DH and TH), resulting in hygienic and sanitary conditions suitable for food use. Slaughtering with liquid nitrogen and blanching was more conducive to achieving high protein digestibility results than traditional freezing or the use of Melacide®.

Advanced computational approaches to understand protein aggregation

Protein aggregation is a widespread phenomenon implicated in debilitating diseases like Alzheimer's, Parkinson's, and cataracts, presenting complex hurdles for the field of molecular biology. In this review, we explore the evolving realm of computational methods and bioinformatics tools that have revolutionized our comprehension of protein aggregation. Beginning with a discussion of the multifaceted challenges associated with understanding this process and emphasizing the critical need for precise predictive tools, we highlight how computational techniques have become indispensable for understanding protein aggregation. We focus on molecular simulations, notably molecular dynamics (MD) simulations, spanning from atomistic to coarse-grained levels, which have emerged as pivotal tools in unraveling the complex dynamics governing protein aggregation in diseases such as cataracts, Alzheimer's, and Parkinson's. MD simulations provide microscopic insights into protein interactions and the subtleties of aggregation pathways, with advanced techniques like replica exchange molecular dynamics, Metadynamics (MetaD), and umbrella sampling enhancing our understanding by probing intricate energy landscapes and transition states. We delve into specific applications of MD simulations, elucidating the chaperone mechanism underlying cataract formation using Markov state modeling and the intricate pathways and interactions driving the toxic aggregate formation in Alzheimer's and Parkinson's disease. Transitioning we highlight how computational techniques, including bioinformatics, sequence analysis, structural data, machine learning algorithms, and artificial intelligence have become indispensable for predicting protein aggregation propensity and locating aggregation-prone regions within protein sequences. Throughout our exploration, we underscore the symbiotic relationship between computational approaches and empirical data, which has paved the way for potential therapeutic strategies against protein aggregation-related diseases. In conclusion, this review offers a comprehensive overview of advanced computational methodologies and bioinformatics tools that have catalyzed breakthroughs in unraveling the molecular basis of protein aggregation, with significant implications for clinical interventions, standing at the intersection of computational biology and experimental research.

Microfluidic Stress Device to Decouple the Synergistic Effect of Shear and Interfaces on Antibody Aggregation

Protein denaturation and aggregation resulting from the effects of interfacial stress, often enhanced by flow and shear stress, pose significant challenges in the production of therapeutic proteins and monoclonal antibodies. The influence of flow on protein stability is closely intertwined with interfacial effects. In this study, we have developed a microfluidic device capable of exposing low volume (< 320 µL) protein solutions to highly uniform shear. To disentangle the synergistic impact of flow and interfaces on protein aggregation, we fabricated two devices composed of different materials, namely poly(methyl methacrylate) (PMMA) and stainless steel. Upon application of shear, we observed formation of protein particles in the micron-size range. Notably, The number of particles generated in the steel devices was ∼ 3.5 fold lower than in the PMMA device, hinting at an interface-mediated effect. With increasing the protein concentration from 1 to 50 mg/mL we observed a saturation in the amount of aggregates, further confirming the key role of solid-liquid interfaces in inducing particle formation. Introduction of non-ionic surfactants prevented protein aggregation, even at the highest tested protein concentration and low surfactant concentrations of 0.05 mg/mL. Overall, our findings corroborate the synergistic impact of shear and interface effects on protein aggregation. The device developed in this study offers a small-scale platform for assessing the stability of antibody formulations throughout various stages of the development and manufacturing process.

AttABseq: an attention-based deep learning prediction method for antigen-antibody binding affinity changes based on protein sequences

The optimization of therapeutic antibodies through traditional techniques, such as candidate screening via hybridoma or phage display, is resource-intensive and time-consuming. In recent years, computational and artificial intelligence-based methods have been actively developed to accelerate and improve the development of therapeutic antibodies. In this study, we developed an end-to-end sequence-based deep learning model, termed AttABseq, for the predictions of the antigen-antibody binding affinity changes connected with antibody mutations. AttABseq is a highly efficient and generic attention-based model by utilizing diverse antigen-antibody complex sequences as the input to predict the binding affinity changes of residue mutations. The assessment on the three benchmark datasets illustrates that AttABseq is 120% more accurate than other sequence-based models in terms of the Pearson correlation coefficient between the predicted and experimental binding affinity changes. Moreover, AttABseq also either outperforms or competes favorably with the structure-based approaches. Furthermore, AttABseq consistently demonstrates robust predictive capabilities across a diverse array of conditions, underscoring its remarkable capacity for generalization across a wide spectrum of antigen-antibody complexes. It imposes no constraints on the quantity of altered residues, rendering it particularly applicable in scenarios where crystallographic structures remain unavailable. The attention-based interpretability analysis indicates that the causal effects of point mutations on antibody-antigen binding affinity changes can be visualized at the residue level, which might assist automated antibody sequence optimization. We believe that AttABseq provides a fiercely competitive answer to therapeutic antibody optimization.

Anion Binding to Ammonium and Guanidinium Hosts: Implications for the Reverse Hofmeister Effects Induced by Lysine and Arginine Residues

Anions have a profound effect on the properties of soluble proteins. Such Hofmeister effects have implications in biologics stability, protein aggregation, amyloidogenesis, and crystallization. However, the interplay between the important noncovalent interactions (NCIs) responsible for Hofmeister effects is poorly understood. To contribute to improving this state of affairs, we report on the NCIs between anions and ammonium and guanidinium hosts 1 and 2, and the consequences of these. Specifically, we investigate the properties of cavitands designed to mimic two prime residues for anion-protein NCIs─lysines and arginines─and the solubility consequences of complex formation. Thus, we report NMR and ITC affinity studies, X-ray analysis, MD simulations, and anion-induced critical precipitation concentrations. Our findings emphasize the multitude of NCIs that guanidiniums can form and how this repertoire qualitatively surpasses that of ammoniums. Additionally, our studies demonstrate the ease by which anions can dispense with a fraction of their hydration-shell waters, rearrange those that remain, and form direct NCIs with the hosts. This raises many questions concerning how solvent shell plasticity varies as a function of anion, how the energetics of this impact the different NCIs between anions and ammoniums/guanidiniums, and how this affects the aggregation of solutes at high anion concentrations.

Protecting Proteins from Desiccation Stress Using Molecular Glasses and Gels

Faced with desiccation stress, many organisms deploy strategies to maintain the integrity of their cellular components. Amorphous glassy media composed of small molecular solutes or protein gels present general strategies for protecting against drying. We review these strategies and the proposed molecular mechanisms to explain protein protection in a vitreous matrix under conditions of low hydration. We also describe efforts to exploit similar strategies in technological applications for protecting proteins in dry or highly desiccated states. Finally, we outline open questions and possibilities for future explorations.

Amyloids, amorphous aggregates and assemblies of peptides - Assessing aggregation

Amyloid and amorphous aggregates represent the two major categories of aggregates associated with diseases, and although exhibiting distinct features, researchers often treat them as equivalent, which demonstrates the need for more thorough characterization. Here, we compare amyloid and amorphous aggregates based on their biochemical properties, kinetics, and morphological features. To further decipher this issue, we propose the use of peptide self-assemblies as minimalistic models for understanding the aggregation process. Peptide building blocks are significantly smaller than proteins that participate in aggregation, however, they make a plausible means to bridge the gap in discerning the aggregation process at the more complex, protein level. Additionally, we explore the potential use of peptide-inspired models to research the liquid-liquid phase separation as a feasible mechanism preceding amyloid formation. Connecting these concepts can help clarify our understanding of aggregation-related disorders and potentially provide novel drug targets to impede and reverse these serious illnesses.

gp120-derived amyloidogenic peptides form amyloid fibrils that increase HIV-1 infectivity

Apart from mediating viral entry, the function of the free HIV-1 envelope protein (gp120) has yet to be elucidated. Our group previously showed that EP2 derived from one β-strand in gp120 can form amyloid fibrils that increase HIV-1 infectivity. Importantly, gp120 contains ~30 β-strands. We examined whether gp120 might serve as a precursor protein for the proteolytic release of amyloidogenic fragments that form amyloid fibrils, thereby promoting viral infection. Peptide array scanning, enzyme degradation assays, and viral infection experiments in vitro confirmed that many β-stranded peptides derived from gp120 can indeed form amyloid fibrils that increase HIV-1 infectivity. These gp120-derived amyloidogenic peptides, or GAPs, which were confirmed to form amyloid fibrils, were termed gp120-derived enhancers of viral infection (GEVIs). GEVIs specifically capture HIV-1 virions and promote their attachment to target cells, thereby increasing HIV-1 infectivity. Different GAPs can cross-interact to form heterogeneous fibrils that retain the ability to increase HIV-1 infectivity. GEVIs even suppressed the antiviral activity of a panel of antiretroviral agents. Notably, endogenous GAPs and GEVIs were found in the lymphatic fluid, lymph nodes, and cerebrospinal fluid (CSF) of AIDS patients in vivo. Overall, gp120-derived amyloid fibrils might play a crucial role in the process of HIV-1 infectivity and thus represent novel targets for anti-HIV therapeutics.

Integrated micro-scale protein a chromatography and Low pH viral inactivation unit operations on an automated platform

High throughput process development (HTPD) is established for time- and resource- efficient chromatographic process development. However, integration with non-chromatographic operations within a monoclonal antibody (mAb) purification train is less developed. An area of importance is the development of low pH viral inactivation (VI) that follows protein A chromatography. However, the lack of pH measurement devices at the micro-scale represents a barrier to implementation, which prevents integration with the surrounding unit operations, limiting overall process knowledge. This study is based upon the design and testing of a HTPD platform for integration of the protein A and low pH VI operations. This was achieved by using a design and simulation software before execution on an automated liquid handler. The operations were successfully translated to the micro-scale, as assessed by analysis of recoveries and molecular weight content. The integrated platform was then used as a tool to assess the effect of pH on HMWC during low pH hold. The laboratory-scale and micro-scale elution pools showed comparable HMWC across the pH range 3.2-3.7. The investigative power of the platform is highlighted by evaluating the resources required to conduct a hypothetical experiment. This results in lower resource demands and increased labor efficiency relative to the laboratory-scale. For example, the experiment can be conducted in 7 h, compared to 105 h, translating to labor hours, 3 h and 28 h for the micro-scale and laboratory-scale, respectively. This presents the opportunity for further integration beyond chromatographic operations within the purification sequence, to establish a fit-to-platform assessment tool for mAb process development.

Pharmaceutical proteins at the interfaces and the role of albumin

A critical measure of the quality of pharmaceutical proteins is the preservation of native conformations of the active pharmaceutical ingredients. Denaturation of the active proteins in any step before administration into patients could lead to loss of potency and/or aggregation, which is associated with an increased risk of immunogenicity of the products. Interfacial stress enhances protein instability as their adsorption to the air-liquid and liquid-solid interfaces are implicated in the formation of denatured proteins and aggregates. While excipients in protein formulations have been employed to reduce the risk of aggregation, the roles of albumin as a stabilizer have not been reviewed from practical and theoretical standpoints. The amphiphilic nature of albumin makes it accumulate at the interfaces. In this review, we aim to bridge the knowledge gap between interfacial instability and the influence of albumin as a surface-active excipient in the context of reducing the immunogenicity risk of protein formulations.

Fibrillation of Human Serum Albumin Differentially Affected by Asp-, Arg-, and Tyr-Capped Gold Nanoparticles

Fibrillation of proteins is associated with a number of debilitating diseases, including various neurodegenerative disorders. Prevention of the protein fibrillation process is therefore of immense importance. We investigated the effect of amino acid-capped AuNPs on the prevention of the fibrillation process of human serum albumin (HSA), a model protein. Amino acid-capped AuNPs of varying sizes and agglomeration extents were synthesized under physiological conditions. The AuNPs were characterized by their characteristic surface plasmon resonance (SPR), and their interactions with HSA were investigated through emission spectroscopy in addition to circular dichroism (CD) spectral analyses. Fluorescence lifetime imaging (FLIM) as well as transmission electron microscopy (TEM) were used to observe the fibrillar network. Thermodynamic and kinetic analyses from CD and fluorescence emission spectra provided insights into the fibrillation pathway adopted by HSA in the presence of capped AuNPs. Kinetics of the fibrillation pathway followed by ThT fluorescence emission confirmed the sigmoidal nature of the process. The highest cooperativity was observed in the case of Asp-AuNPs with HSA. This was in accordance with the ΔG value obtained from the CD spectral analyses, where Arg-AuNPs with HSA showed the highest positive ΔG value and Asp-AuNPs with HSA showed the most negative ΔG value. The study provides information about the potential use of conjugate AuNPs to monitor the fibrillation process in proteins.

Factors influencing amyloid fibril formation

Protein aggregation is a complex process with several stages that lead to the formation of complex structures and shapes with a broad variability in stability and toxicity. The aggregation process is affected by various factors and environmental conditions that disrupt the protein's original state, including internal factors like mutations, expression levels, and polypeptide chain truncation, as well as external factors, such as dense molecular surroundings, post-translation modifications, and interactions with other proteins, nucleic acids, small molecules, metal ions, chaperones, and lipid membranes. During the aggregation process, the biological activity of an aggregating protein may be reduced or eliminated, whereas the resulting aggregates may have the potential to be immunogenic, or they may have other undesirable properties. Finding the cause(s) of protein aggregation and controlling it to an acceptable level is among the most crucial topics of research in academia and biopharmaceutical companies. This chapter aims to review intrinsic pathways of protein aggregation and potential extrinsic variables that influence this process.

Designing Multifunctional Biomaterials via Protein Self-Assembly

Protein self-assembly is a fundamental biological process where proteins spontaneously organize into complex and functional structures without external direction. This process is crucial for the formation of various biological functionalities. However, when protein self-assembly fails, it can trigger the development of multiple disorders, thus making understanding this phenomenon extremely important. Up until recently, protein self-assembly has been solely linked either to biological function or malfunction; however, in the past decade or two it has also been found to hold promising potential as an alternative route for fabricating materials for biomedical applications. It is therefore necessary and timely to summarize the key aspects of protein self-assembly: how the protein structure and self-assembly conditions (chemical environments, kinetics, and the physicochemical characteristics of protein complexes) can be utilized to design biomaterials. This minireview focuses on the basic concepts of forming supramolecular structures, and the existing routes for modifications. We then compare the applicability of different approaches, including compartmentalization and self-assembly monitoring. Finally, based on the cutting-edge progress made during the last years, we summarize the current knowledge about tailoring a final function by introducing changes in self-assembly and link it to biomaterials' performance.

The quest for down scale representativeness: how to exploit CFD to design a shear study for vaccines

In this work, we exploit computational fluid dynamics (CFD) to evaluate stirred tank reactor (STR) process engineer parameters (PEP) and design a scale-down system (SDS) to be representative of the formulation and filling process steps for an Aluminum adjuvanted vaccine drug product (DP). To study the shear history in the SDS we used the concept of number of passages, combined with an appropriate stirring speed down scale strategy comprising of either (i) tip speed equivalence, widely used as a scale-up criterion for a shear-sensitive product, or (ii) rotating shear, a shear metric introduced by Metz and Otto in 1957 but never used as scaling criterion. The outcome of the CFD simulations shows that the tip equivalence generates a worst-case SDS in terms of shear, whereas the rotating shear scaling approach could be used to design a more representative SDS. We monitored the trend over time for "In Vitro Relative Potency" as DP Critical Quality Attribute for both scaling approaches, which highlighted the crucial role of choosing the appropriate scaling-down approach to be representative of the manufacturing scale during process characterization studies.

Proteotoxic stress and the ubiquitin proteasome system

The ubiquitin proteasome system maintains protein homeostasis by regulating the breakdown of misfolded proteins, thereby preventing misfolded protein aggregates. The efficient elimination is vital for preventing damage to the cell by misfolded proteins, known as proteotoxic stress. Proteotoxic stress can lead to the collapse of protein homeostasis and can alter the function of the ubiquitin proteasome system. Conversely, impairment of the ubiquitin proteasome system can also cause proteotoxic stress and disrupt protein homeostasis. This review examines two impacts of proteotoxic stress, 1) disruptions to ubiquitin homeostasis (ubiquitin stress) and 2) disruptions to proteasome homeostasis (proteasome stress). Here, we provide a mechanistic description of the relationship between proteotoxic stress and the ubiquitin proteasome system. This relationship is illustrated by findings from several protein misfolding diseases, mainly neurodegenerative diseases, as well as from basic biology discoveries from yeast to mammals. In addition, we explore the importance of the ubiquitin proteasome system in endoplasmic reticulum quality control, and how proteotoxic stress at this organelle is alleviated. Finally, we highlight how cells utilize the ubiquitin proteasome system to adapt to proteotoxic stress and how the ubiquitin proteasome system can be genetically and pharmacologically manipulated to maintain protein homeostasis.

Effect of Aggregation and Molecular Size on the Ice Nucleation Efficiency of Proteins

Aerosol acts as ice-nucleating particles (INPs) by catalyzing the formation of ice crystals in clouds at temperatures above the homogeneous nucleation threshold (-38 °C). In this study, we show that the immersion mode ice nucleation efficiency of the environmentally relevant protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), occurs at temperatures between -6.8 and -31.6 °C. Further, we suggest that this range is controlled by the RuBisCO concentration and protein aggregation. The warmest median nucleation temperature (-7.9 ± 0.8 °C) was associated with the highest concentration of RuBisCO (2 × 10-1 mg mL-1) and large aggregates with a hydrodynamic diameter of ∼103 nm. We investigated four additional chemically and structurally diverse proteins, plus the tripeptide glutathione, and found that each of them was a less effective INP than RuBisCO. Ice nucleation efficiency of the proteins was independent of the size (molecular weight) for the five proteins investigated in this study. In contrast to previous work, increasing the concentration and degree of aggregation did not universally increase ice nucleation efficiency. RuBisCO was the exception to this generalization, although the underlying molecular mechanism determining why aggregated RuBisCO is such an effective INP remains elusive.

Application of Machine Learning in the Quantitative Analysis of the Surface Characteristics of Highly Abundant Cytoplasmic Proteins: Toward AI-Based Biomimetics

Proteins in the crowded environment of human cells have often been studied regarding nonspecific interactions, misfolding, and aggregation, which may cause cellular malfunction and disease. Specifically, proteins with high abundance are more susceptible to these issues due to the law of mass action. Therefore, the surfaces of highly abundant cytoplasmic (HAC) proteins directly exposed to the environment can exhibit specific physicochemical, structural, and geometrical characteristics that reduce nonspecific interactions and adapt to the environment. However, the quantitative relationships between the overall surface descriptors still need clarification. Here, we used machine learning to identify HAC proteins using hydrophobicity, charge, roughness, secondary structures, and B-factor from the protein surfaces and quantified the contribution of each descriptor. First, several supervised learning algorithms were compared to solve binary classification problems for the surfaces of HAC and extracellular proteins. Then, logistic regression was used for the feature importance analysis of descriptors considering model performance (80.2% accuracy and 87.6% AUC) and interpretability. The HAC proteins showed positive correlations with negatively and positively charged areas but negative correlations with hydrophobicity, the B-factor, the proportion of beta structures, roughness, and the proportion of disordered regions. Finally, the details of each descriptor could be explained concerning adaptative surface strategies of HAC proteins to regulate nonspecific interactions, protein folding, flexibility, stability, and adsorption. This study presented a novel approach using various surface descriptors to identify HAC proteins and provided quantitative design rules for the surfaces well-suited to human cellular crowded environments.

Mechanistic Insights into the Adsorption of Monoclonal Antibodies at the Water/Vapor Interface

Monoclonal antibodies (mAbs) are active components of therapeutic formulations that interact with the water-vapor interface during manufacturing, storage, and administration. Surface adsorption has been demonstrated to mediate antibody aggregation, which leads to a loss of therapeutic efficacy. Controlling mAb adsorption at interfaces requires a deep understanding of the microscopic processes that lead to adsorption and identification of the protein regions that drive mAb surface activity. Here, we report all-atom molecular dynamics (MD) simulations of the adsorption behavior of a full IgG1-type antibody at the water/vapor interface. We demonstrate that small local changes in the protein structure play a crucial role in promoting adsorption. Also, interfacial adsorption triggers structural changes in the antibody, potentially contributing to the further enhancement of surface activity. Moreover, we identify key amino acid sequences that determine the adsorption of antibodies at the water-air interface and outline strategies to control the surface activity of these important therapeutic proteins.

The Development of a Novel Aflibercept Formulation for Ocular Delivery

Aflibercept is a recombinant fusion protein that is commercially available for several ocular diseases impacting millions of people worldwide. Here, we use a case study approach to examine alternative liquid formulations for aflibercept for ocular delivery, utilizing different stabilizers, buffering agents, and surfactants with the goal of improving the thermostability to allow for limited storage outside the cold chain. The formulations were developed by studying the effects of pH changes, substituting amino acids for sucrose and salt, and using polysorbate 80 or poloxamer 188 instead of polysorbate 20. A formulation containing acetate, proline, and poloxamer 188 had lower rates of aggregate formation at 4, 30, and 40°C when compared to the marketed commercial formulation containing phosphate, sucrose, sodium chloride, and polysorbate 20. Further studies examining subvisible particles after exposure to a transport stress and long-term stability at 4°C, post-translational modifications by multi-attribute method, purity by reduced and non-reduced capillary electrophoresis, and potency by cell proliferation also demonstrated a comparable or improved stability for the enhanced formulation of acetate, proline, and poloxamer 188. This enhanced stability could enable limited storage outside of the cold chain, allowing for easier distribution in low to middle income countries.

Fluorescence-Based Protein Stability Monitoring-A Review

Proteins are large biomolecules with a specific structure that is composed of one or more long amino acid chains. Correct protein structures are directly linked to their correct function, and many environmental factors can have either positive or negative effects on this structure. Thus, there is a clear need for methods enabling the study of proteins, their correct folding, and components affecting protein stability. There is a significant number of label-free methods to study protein stability. In this review, we provide a general overview of these methods, but the main focus is on fluorescence-based low-instrument and -expertise-demand techniques. Different aspects related to thermal shift assays (TSAs), also called differential scanning fluorimetry (DSF) or ThermoFluor, are introduced and compared to isothermal chemical denaturation (ICD). Finally, we discuss the challenges and comparative aspects related to these methods, as well as future opportunities and assay development directions.

The Effects of Excipients on Freeze-dried Monoclonal Antibody Formulation Degradation and Sub-Visible Particle Formation during Shaking

PURPOSES

We previously reported an unexpected phenomenon that shaking stress could cause more protein degradation in freeze-dried monoclonal antibody (mAb) formulations than liquid ones (J Pharm Sci, 2022, 2134). The main purposes of the present study were to investigate the effects of shaking stress on protein degradation and sub-visible particle (SbVP) formation in freeze-dried mAb formulations, and to analyze the factors influencing protein degradation during production and transportation.

METHODS

The aggregation behavior of mAb-X formulations during production and transportation was simulated by shaking at a rate of 300 rpm at 25°C for 24 h. The contents of particles and monomers were analyzed by micro-flow imaging, dynamic light scattering, size exclusion chromatography, and ultraviolet - visible (UV-Vis) spectroscopy to compare the protective effects of excipients on the aggregation of mAb-X.

RESULTS

Shaking stress could cause protein degradation in freeze-dried mAb-X formulations, while surfactant, appropriate pH, polyol mannitol, and high protein concentration could impact SbVP generation. Water content had little effect on freeze-dried protein degradation during shaking, as far as the water content was controlled in the acceptable range as recommended by mainstream pharmacopoeias (i.e., less than 3%).

CONCLUSIONS

Shaking stress can reduce the physical stability of freeze-dried mAb formulations, and the addition of surfactants, polyol mannitol, and a high protein concentration have protective effects against the degradation of model mAb formulations induced by shaking stress. The experimental results provide new insight for the development of freeze-dried mAb formulations.

Shear stress as a driver of degradation for protein-based therapeutics: More accomplice than culprit

Protein degradation is a major concern for protein-based therapeutics. It may alter the biological activity of the product and raise the potential for undesirable effects on the patients. Among the numerous drivers of protein degradation, shear stress has been the focus around which much work has revolved since the 1970s. In the pharmaceutical realm, the product is often processed through several unit operations, which include mixing, pumping, filtration, filling, and atomization. Nonetheless, the drug might be exposed to significant shear stresses, which might cooperatively contribute to product degradation, together with interfacial stress. This review presents fundamentals of shear stress about protein structure, followed by an overview of the drivers of product degradation. The impact of shear stress on protein stability in different unit operations is then presented, and recommendations for limiting the adverse effects on the biopharmaceutical formulations are outlined. Finally, several devices used to explore the effects of shear stress are discussed.

Modular and tunable alternative surfactants for biopharmaceuticals provide insights into Surfactant's Structure-Function relationship

Surface-induced aggregation of protein therapeutics is opposed by employing surfactants, which are ubiquitously used in drug product development, with polysorbates being the gold standard. Since poloxamer 188 is currently the only generally accepted polysorbate alternative, but cannot be ubiquitously applied, there is a strong need to develop surfactant alternatives for protein biologics that would complement and possibly overcome known drawbacks of existing surfactants. Yet, a severe lack of structure-function relationship knowledge complicates the development of new surfactants. Herein, we perform a systematic analysis of the structure-function relationship of three classes of novel alternative surfactants. Firstly, the mode of action is thoroughly characterized through tensiometry, calorimetry and MD simulations. Secondly, the safety profiles are evaluated through cell-based in vitro assays. Ultimately, we could conclude that the alternative surfactants investigated possess a mode of action and safety profile comparable to polysorbates. Moreover, the biophysical patterns elucidated here can be exploited to precisely tune the features of future surfactant designs.

Optimized recombinant production of the bacteriocin garvicin Q by Corynebacterium glutamicum

Bacteriocins are antimicrobial peptides applied in food preservation and are interesting candidates as alternatives to conventional antibiotics or as microbiome modulators. Recently, we established Corynebacterium glutamicum as a suitable production host for various bacteriocins including garvicin Q (GarQ). Here, we establish secretion of GarQ by C. glutamicum via the Sec translocon achieving GarQ titers of about 7 mg L-1 in initial fermentations. At neutral pH, the cationic peptide is efficiently adsorbed to the negatively charged envelope of producer bacteria limiting availability of the bacteriocin in culture supernatants. A combination of CaCl2 and Tween 80 efficiently reduces GarQ adsorption to C. glutamicum. Moreover, cultivation in minimal medium supplemented with CaCl2 and Tween 80 improves GarQ production by C. glutamicum to about 15 mg L-1 but Tween 80 resulted in reduced GarQ activity at later timepoints. Using a reporter strain and proteomic analyses, we identified HtrA, a protease associated with secretion stress, as another potential factor limiting GarQ production. Transferring production to HtrA-deficient C. glutamicum K9 improves GarQ titers to close to 40 mg L-1. Applying conditions of low aeration prevented loss in activity at later timepoints and improved GarQ titers to about 100 mg L-1. This is about 50-fold higher than previously shown with a C. glutamicum strain employing the native GarQ transporter GarCD for secretion and in the range of levels observed with the native producer Lactococcus petauri B1726. Additionally, we tested several synthetic variants of GarQ and were able to show that exchange of the methionine in position 5 to a phenylalanine (GarQM5F) results in markedly increased activity against Lactococcus lactis and Listeria monocytogenes. In summary, our findings shed light on several aspects of recombinant GarQ production that may also be of relevance for production with natural producers and other bacteriocins.

Spectroscopic Analysis of the Effect of Ibuprofen Degradation Products on the Interaction between Ibuprofen and Human Serum Albumin

BACKGROUND

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are one of the most commonly used groups of medicinal compounds in the world. The wide access to NSAIDs and the various ways of storing them due to their easy accessibility often entail the problem with the stability and durability resulting from the exposure of drugs to external factors. The aim of the research was to evaluate in vitro the mechanism of competition between ibuprofen (IBU) and its degradation products, i.e., 4'-isobutylacetophenone (IBAP) and (2RS)-2-(4- formylphenyl)propionic acid (FPPA) during transport in a complex with fatted (HSA) and defatted (dHSA) human serum albumin.

METHODS

The research was carried out using spectroscopic techniques, such as spectrophotometry, infrared spectroscopy and nuclear magnetic resonance spectroscopy.

RESULTS

The comprehensive application of spectroscopic techniques allowed, among others, for the determination of the binding constant, the number of classes of binding sites and the cooperativeness constant of the analyzed systems IBU-(d)HSA, IBU-(d)HSA-FPPA, IBU-(d)HSA-IBAP; the determination of the effect of ibuprofen and its degradation products on the secondary structure of albumin; identification and assessment of interactions between ligand and albumin; assessment of the impact of the presence of fatty acids in the structure of albumin and the measurement temperature on the binding of IBU, IBAP and FPPA to (d)HSA.

CONCLUSION

The conducted research allowed us to conclude that the presence of ibuprofen degradation products and the increase in their concentration significantly affect the formation of the IBU-albumin complex and thus, the value of the association constant of the drug, changing the concentration of its free fraction in the blood plasma. It was also found that the presence of an ibuprofen degradation product in a complex with albumin affects its secondary structure.

Magnesium ions regulated ovalbumin-lysozyme heteroprotein complex: Aggregation kinetics, thermodynamics and morphologic structure

This study aims to investigate the mechanism of magnesium ions regulated ovalbumin-lysozyme (OVA-LYS) heteroprotein aggregation behavior via aggregation kinetics model, exploring the relationship between differential aggregation behavior and protein molecular structure, intermolecular interactions and thermal stability. Results showed that the aggregation rate (kapp) and maximum absorbance (Amax) of the OVA-LYS heteroprotein complex were located between OVA and LYS. Meanwhile, the thermal denaturation temperature (Td) and denaturation enthalpy (ΔH) were between the values of OVA and LYS as well. Compared with OVA, the thermal stability of the OVA-LYS heteroprotein complex increased owing to the electrostatic interactions between OVA and LYS, resulting in slower aggregation rate and lower aggregation degree. Molecular dynamics simulations revealed the molecular conformational changes during OVA-LYS binary protein binding and the stability of the complex conformation. Moreover, MgCl2 weakened the OVA-LYS interactions through Debye shielding while increasing thermal stability, allowing the two proteins to aggregate into amorphous precipitates rather than spherical coacervates. Overall, this study provides information to further understand the regulation mechanism of proteins differential aggregation behavior by ions.

UVB pretreatment of β-lactoglobulin affects the temperature-induced formation of functional amyloid-like aggregates and promotes oxidative degradation

Unfolding in combination with or without acid hydrolysis is crucial for the formation of functional amyloid (fibrillar) or amyloid-like (worm-like) β-lactoglobulin (BLG) aggregates, which can be induced through temperature treatment for several hours at pH 2-4. A preceding conformational destabilization of BLG might affect its aggregation. We investigated ultraviolet (UV) B radiation as conformational perturbing treatment to facilitate temperature-induced protein aggregation. 2-h UVB pretreated BLG (UV-BLG) exhibited an accelerated worm-like aggregation at pH 3.5, while at pH 2 the formation of fibrils was decelerated. The UV-induced conformational destabilization lowered the thermal stability and thus facilitates unfolding during thermal treatment. Thereby, the formation of covalent and non-covalent intermolecular interactions was favored, which promoted assembly of intact proteins resulting in worm-like aggregates. The oxidative degradation of UV-BLG was suggested to alter fibrillation-prone protein regions and thereby impede peptide assembly.

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.

Determination of the critical pH for unfolding water-soluble cod protein and its effect on encapsulation capacities

Hydrophobic polyphenols, with a variety of physiological activities, are often practically limited due to their low water solubility and chemical instability, among which curcumin (Cur) is a representative hydrophobic polyphenol. To improve Cur, the cod protein (CP)-Cur composite particles (CP-Cur) were successfully prepared using the pH-shift method, but this pH-shift method (7-12-7) required a higher pH, which limited application and increased cost. The critical pH of CP structure unfolding during pH-shift and its encapsulation effect on Cur were investigated in this paper. During the pH-shift process, the critical pH of the structural unfolding of CP was pH 10, and the degree of protein structure unfolding was higher, which was attributed to the increasing electrostatic repulsion, and the weakened hydrogen bond and hydrophobic interaction. The encapsulation efficiency of CP-Cur formed after pH 10-shift was higher than that formed after pH 9.8-shift, which increased by 22.17 %. At pH 9.8, the binding sites in CP reached saturation at the molar ratio of 10, while at pH 10 and 10.2, the binding sites in CP both reached saturation at the molar ratio of 14, also indicating that the protein treated with critical pH could bind more Cur. The binding between Cur and CP was mostly hydrophobic interaction, accompanied by hydrogen bonding and electrostatic interactions. The above results verified the necessity of critical pH in the experiment, indicating that critical pH could indeed improve the encapsulation effect and obtain a higher encapsulation efficiency. This work will help improve the large-scale application of hydrophobic functional substances in production.

Quartz Crystal Microbalance as a Predictive Tool for Drug-Material of Construction Interactions in Intravenous Protein Drug Administration

As a growing number of protein drug products are developed, formulation characterization is becoming important. An IgG drug product is tested at concentrations from 0.0001-0.1 mg/mL for adsorption behavior to polymer surfaces polyvinyl chloride (PVC) and polypropylene (PP) upon dilution in normal saline (NS) using quartz crystal microbalance with dissipation (QCM-D). The studies mimicked IgG antibody interaction during IV administration with polymeric surfaces within syringes, lines, and bags. Drug product was characterized with excipients, with focus on surfactant. Drug solutions were run over polymer-coated sensors to measure the adsorption behavior of the formulation with emphasis on the behavior of each of the formulation's components. Over 60 sensorgram data sets were correlated with assayed protein solution concentrations in mock NS-diluted infusions of drug product in the equivalent concentrations to QCM experiments to build a preliminary predictive model for determining fraction of drug and surfactant adsorbed and lost at the hydrophobic surface during administration. These results create a method for reliably and predictively estimating drug product adsorption behavior and protein drug dose loss on polymers at different protein drug concentrations.

Prediction of Protein Aggregation Propensity via Data-Driven Approaches

Protein aggregation occurs when misfolded or unfolded proteins physically bind together and can promote the development of various amyloid diseases. This study aimed to construct surrogate models for predicting protein aggregation via data-driven methods using two types of databases. First, an aggregation propensity score database was constructed by calculating the scores for protein structures in the Protein Data Bank using Aggrescan3D 2.0. Moreover, feature- and graph-based models for predicting protein aggregation have been developed by using this database. The graph-based model outperformed the feature-based model, resulting in an R2 of 0.95, although it intrinsically required protein structures. Second, for the experimental data, a feature-based model was built using the Curated Protein Aggregation Database 2.0 to predict the aggregated intensity curves. In summary, this study suggests approaches that are more effective in predicting protein aggregation, depending on the type of descriptor and the database.

The biomolecular gastrointestinal corona in oral drug delivery

The formation of a biomolecular corona on exogenous particles in plasma is well studied and is known to dictate the biodistribution and cellular interactions of nanomedicine formulations. In contrast, while the oral route is the most favorable administration method for pharmaceuticals, little is known about the formation and composition of the corona formed by biomolecules on particles within the gastrointestinal tract. This work reviews the current literature understanding of (1) the formation of drug particles after oral administration, (2) the formation of a biomolecular corona within the gastrointestinal tract ("the gastrointestinal corona"), and (3) the possible implications of the formation of a gastrointestinal corona on the interactions of drug particles with their biological environment. In doing so, this work aims to establish the significance of the formation of a gastrointestinal corona in oral drug delivery to ultimately arrive at new avenues to control the behavior of orally administered pharmaceuticals.

A comprehensive review of silk-fibroin hydrogels for cell and drug delivery applications in tissue engineering and regenerative medicine

Hydrogel scaffolds hold great promise for developing novel treatment strategies in the field of regenerative medicine. Within this context, silk fibroin (SF) has proven to be a versatile material for a wide range of tissue engineering applications owing to its structural and functional properties. In the present review, we report on the design and fabrication of different forms of SF-based scaffolds for tissue regeneration applications, particularly for skin, bone, and neural tissues. In particular, SF hydrogels have emerged as delivery systems for a wide range of bio-actives. Given the growing interest in the field, this review has a primary focus on the fabrication, characterization, and properties of SF hydrogels. We also discuss their potential for the delivery of drugs, stem cells, genes, peptides, and growth factors, including future directions in the field of SF hydrogel scaffolds.

Structural modification of poppy-pollen protein as a natural antioxidant, emulsifier and carrier in spray-drying of O/W-emulsion: Physicochemical and oxidative stabilization

This study was aimed to investigate the efficiency of poppy-pollen (PP) protein and peptides as carrier for spray-drying encapsulation of grape-seed oil (GSO). The composition of amino acids, functional properties and bioactivity (scavenging of DPPH, ABTS, OH, and nitric-oxide radicals, reducing power, total antioxidant, TBARS levels in O/W-emulsion, and chelation of Fe2+ and Cu2+ ions) of PP-protein were affected by the enzymolysis time. Partial enzymolysis (30 min) led to improved solubility, protein surface activity and increased physical stability of GSO/W emulsion (relative to creaming, aggregation and flocculation) during storage. Also, spray-dried emulsions with this type of carrier (H-30) had the highest production yield (~67 %), solubility (~92 %), flowability, encapsulation efficiency (~96 %), reconstitution ability (least size and EE changes), physical and oxidative stability. The evaluation of the chemical structures (FTIR) indicated the formation of hydrogen bonds between the cis-alkene groups of fatty acids and the hydroxyl groups of the amide A and B regions, as well as the trapping of oil in the carrier matrix. SEM images illustrated the effect of native protein carriers (particles with smooth, dents, and hollow surfaces with surface pores), partially (wrinkled and reservoir-type), and strongly (irregular structures, sticky and amorphous agglomerates) hydrolyzed peptides on the morphology of oily-particles. The results of this research indicate the usability of partially hydrolyzed poppy-pollen protein as a source of natural antioxidant, emulsifier, and carrier in the production, stabilization, and encapsulation of oxidation-sensitive bioactive components and emulsions.

Mechanistic insights into gel formation of egg-based yoghurt: The dynamic changes in physicochemical properties, microstructure, and intermolecular interactions during fermentation

This study aimed to elucidate the mechanism of acid-induced gelation in egg-based yoghurt by investigating the dynamic changes in physicochemical properties, texture, rheology, and microstructure of the gel during fermentation, combined with the role of intermolecular forces in gel formation. Results showed that protein aggregation and cross-linking increased as pH decreased during fermentation. Gel hardness increased with fermentation, eventually reaching 11.36 g, while maintaining low fracturability. Water holding capacity (WHC) decreased from 91.77% to 73.13% during fermentation. Rheological testing demonstrated a significant increase in viscosity and dynamic moduli (G' and G''), consistent with the observation of a more compact microstructure by scanning electron microscopy (SEM) and particle size analysis. Furthermore, dynamic changes of surface hydrophobicity, sulfhydryl content, and intermolecular forces suggested that hydrophobic interactions were likely the main driving force for gel formation, as well as that hydrophobic interactions and disulfide bonds played an important role in the maintenance and construction of the gel network structure. Although ionic bonds and hydrogen bonds also had an effect on the gel formation of egg-based yoghurt, their contributions were not significant. The study provided new insights for the development of novel egg-based fermentation foods and the research of acid-induced protein gels, and also contributed to the deep exploitation and utilization of poultry eggs.

Structure and in vitro digestion characteristics of skim goat milk protein during processing: effects of fat separation

BACKGROUND

Although nonfat milk has been used worldwide in the industrial dairy process, little is known about the effects of fat separation during the manufacturing process on skim milk's structural and digestive properties. This study investigated the effects of the manufacturing process on the structure and in vitro digestion properties of skim goat milk, particularly emphasizing fat separation.

RESULTS

Changes in the surface charge and hydrophobicity of milk proteins caused by fat separation resulted in oxidation and aggregation in the subsequent homogenization, heat and spray-drying processing, which affected its digestibility. Compared with separation by dish separator (DS), skim milk after tubular centrifugal separation (CS) showed a higher initial and final digestibility. The CS samples also had a lower surface hydrophobicity level and higher free sulfhydryl content, ζ-potential, and average particle size (P < 0.05). Goat milk protein after CS was more readily oxidized and aggregated during the subsequent homogenization and heat treatment, as evidenced by the higher carbonyl content and particle size. Centrifugal separation also converted more β-sheets to α-helices, thus promoting the aggregation of oxidized skim milk protein.

CONCLUSION

The skim milk after CS and DS demonstrated different structural and digestive properties. Skim goat milk products after CS were more susceptible to oxidant-induced protein structural changes, resulting in higher protein digestibility. These findings provide insights into the mechanism involved in the control of gastric digestion of skim milk during manufacturing process. © 2023 Society of Chemical Industry.

Mechanism of Insoluble Aggregate Formation in a Reconstituted Solution of Spray-Dried Protein Powder

BACKGROUND

Spray-drying is considered a promising alternative drying method to lyophilization (freeze-drying) for therapeutic proteins. Particle counts in reconstituted solutions of dried solid dosage forms of biologic drug products are closely monitored to ensure product quality. We found that high levels of particles formed after reconstitution of protein powders that had been spray-dried under suboptimal conditions.

METHODS

Visible and subvisible particles were evaluated. Soluble proteins in solution before spray-drying and in the reconstituted solution of spray-dried powder were analyzed for their monomer content levels and melting temperatures. Insoluble particles were collected and analyzed by Fourier transform infrared microscopy (FTIR), and further analyzed with hydrogen-deuterium exchange (HDX).

RESULTS

Particles observed after reconstitution were shown not to be undissolved excipients. FTIR confirmed their identity as proteinaceous in nature. These particles were therefore considered to be insoluble protein aggregates, and HDX was applied to investigate the mechanism underlying aggregate formation. Heavy-chain complementarity-determining region 1 (CDR-1) in the aggregates showed significant protection by HDX, suggesting CDR-1 was critical for aggregate formation. In contrast, various regions became more conformationally dynamic globally, suggesting the aggregates have lost protein structural integrity and partially unfolded after spray-drying.

DISCUSSION

The spray-drying process could have disrupted the higher-order structure of proteins and exposed the hydrophobic residues in CDR-1 of the heavy chain, contributing to the formation of aggregate through hydrophobic interactions upon reconstitution of spray-dried powder. These results can contribute to efforts to design spray-dry resilient protein constructs and improve the robustness of the spray-drying process.

Enhanced powder dispersion of dual-excipient spray-dried powder formulations of a monoclonal antibody and its fragment for local treatment of severe asthma

The advent of biologics has brought renewed hope for patients with severe asthma, a condition notorious for being hampered by poor response to conventional therapies and adverse drug reactions owing to corticosteroid dependence. However, biologics are administered as injections, thereby precluding the benefits inhalation therapy could offer such as increased bioavailability at the site of action, minimal systemic side effects, non-invasiveness, and self-administration. Here, 2-hydroxypropyl-beta-cyclodextrin and ʟ-leucine were co-spray-dried, as protein stabiliser and dispersion enhancer, respectively, at various weight ratios to produce a series of formulation platforms. Powder aerosolisation characteristics and particle morphology were assessed for suitability for pulmonary delivery. The selected platform with the best aerosol performance, a 1:1 ratio of the excipients, was then incorporated with a monoclonal antibody directed against IL-4 receptor alpha or its antigen-binding fragment. The dual-excipient antibody formulations exhibited emitted fraction of at least 80% and fine particle fraction exceeding 60% in cascade impactor study, while the residual moisture content was within a desirable range between 1% and 3%. The in vitro antigen-binding ability and inhibitory potency of the spray-dried antibody were satisfactorily preserved. The results from this study corroborate the viability of inhaled solid-state biomacromolecules as a promising treatment approach for asthma.

Structural, kinetic, and thermodynamic aspects of insulin aggregation

Given the significance of protein aggregation in proteinopathies and the development of therapeutic protein pharmaceuticals, revamped interest in assessing and modelling the aggregation kinetics has been observed. Quantitative analysis of aggregation includes data of gradual monomeric depletion followed by the formation of subvisible particles. Kinetic and thermodynamic studies are essential to gain key insights into the aggregation process. Despite being the medical marvel in the world of diabetes, insulin suffers from the challenge of aggregation. Physicochemical stresses are experienced by insulin during industrial formulation, storage, delivery, and transport, considerably impacting product quality, efficacy, and effectiveness. The present review briefly describes the pathways, mathematical kinetic models, and thermodynamics of protein misfolding and aggregation. With a specific focus on insulin, further discussions include the structural heterogeneity and modifications of the intermediates incurred during insulin fibrillation. Finally, different model equations to fit the kinetic data of insulin fibrillation are discussed. We believe that this review will shed light on the conditions that induce structural changes in insulin during the lag phase of fibrillation and will motivate scientists to devise strategies to block the initialization of the aggregation cascade. Subsequent abrogation of insulin fibrillation during bioprocessing will ensure stable and globally accessible insulin for efficient management of diabetes.

Optimization of Water Lentil (Duckweed) Leaf Protein Purification: Identification, Structure, and Foaming Properties

Water lentil, commonly known as duckweed, is an aquatic plant with great agronomic potential, as it can double its biomass in less than 24 h and contains up to 45% leaf proteins on a dry matter basis. However, extracting proteins from leaves is an arduous process due to the complexity of the matrix, which limits their uses in the food industry. In this study, water lentil protein extraction by solubilization was maximized using response surface methodology. By heating at 80 °C at pH 11 with a water lentil powder concentration of 2% or 4% for 2 h, up to 77.8% of total proteins were solubilized. Then, by precipitating the solubilized proteins at pH 4, a protein purity of 57.6% combined with a total protein yield of 60.0% was achieved. To the best of our knowledge, this is the highest leaf protein extraction yield reported in the literature with such protein purity. Proteomics analyses showed that the protein concentrate was composed of around 85.0% RubisCO, and protein structure analyses using ATR-FTIR and DSC were linked to a high protein solubility in water at pH 7. Moreover, a 1.5% protein solution of the protein concentrate at pH 7 showed excellent foaming properties compared to a 10.3% protein egg white solution. It had a superior foaming capacity (194% vs. 122%, respectively) for the same foaming stability after 60 min, which confirms water lentil proteins' potential for human nutrition and food formulation.

A comprehensive review of protein misfolding disorders, underlying mechanism, clinical diagnosis, and therapeutic strategies

INTRODUCTION

Proteins are the most common biological macromolecules in living system and are building blocks of life. They are extremely dynamic in structure and functions. Due to several modifications, proteins undergo misfolding, leading to aggregation and thereby developing neurodegenerative and systemic diseases. Understanding the pathology of these diseases and the techniques used to diagnose them is therefore crucial for their effective management . There are several techniques, currently being in use to diagnose them and those will be discussed in this review.

AIM/OBJECTIVES

Current review aims to discuss an overview of protein aggregation and the underlying mechanisms linked to neurodegeneration and systemic diseases. Also, the review highlights protein misfolding disorders, their clinical diagnosis, and treatment strategies.

METHODOLOGY

Literature related to neurodegenerative and systemic diseases was explored through PubMed, Google Scholar, Scopus, and Medline databases. The keywords used for literature survey and analysis are protein aggregation, neurodegenerative disorders, Alzheimer's disease, Parkinson's disease, systemic diseases, protein aggregation mechanisms, etc. DISCUSSION /CONCLUSION: This review summarises the pathogenesis of neurodegenerative and systemic disorders caused by protein misfolding and aggregation. The clinical diagnosis and therapeutic strategies adopted for the management of these diseases are also discussed to aid in a better understanding of protein misfolding disorders. Many significant concerns about the role, characteristics, and consequences of protein aggregates in neurodegenerative and systemic diseases are not clearly understood to date. Regardless of technological advancements, there are still great difficulties in the management and cure of these diseases. Therefore, for better understanding, diagnosis, and treatment of neurodegenerative and systemic diseases, more studies to identify novel drugs that may aid in their treatment and management are required.

Not the Usual Suspects: Alternative Surfactants for Biopharmaceuticals

Therapeutically relevant proteins naturally adsorb to interfaces, causing aggregation which in turn potentially leads to numerous adverse consequences such as loss of activity or unwanted immunogenic reactions. Surfactants are ubiquitously used in biotherapeutics drug development to oppose interfacial stress, yet, the choice of the surfactant is extremely limited: to date, only polysorbates (PS20/80) and poloxamer 188 are used in commercial products. However, both surfactant families suffer from severe degradation and impurities of the raw material, which frequently increases the risk of particle generation, chemical protein degradation, and potential adverse immune reactions. Herein, we assessed a total of 40 suitable alternative surfactant candidates and subsequently performed a selection through a three-gate screening process employing four protein modalities encompassing six different formulations. The screening is based on short-term agitation-induced aggregation studies coupled to particle analysis and surface tension characterization, followed by long-term quiescence stability studies connected to protein purity measurements and particle analysis. The study concludes by assessing the surfactant's chemical and enzymatic degradation propensity. The candidates emerging from the screening are de novo α-tocopherol-derivatives named VEDG-2.2 and VEDS, produced ad hoc for this study. They display protein stabilization potential comparable or better than polysorbates together with an increased resistance to chemical and enzymatic degradation, thus representing valuable alternative surfactants for biotherapeutics.

Structural Properties of Quinoa Protein Isolate: Impact of Neutral to High Alkaline Extraction pH

In this work, we extracted proteins from white quinoa cultivated in the northeast of Qinghai-Tibet plateau using the method of alkaline solubilization and acid precipitation, aiming to decipher how extraction pH (7-11) influenced extractability, purity and recovery rate, composition, multi-length scale structure, and gelling properties of quinoa protein isolate (QPI). The results showed that protein extractability increased from 39 to 58% with the increment of pH from 7 to 11 whereas protein purity decreased from 89 to 82%. At pH 7-11, extraction suspensions and QPI showed the similar major bands in SDS-PAGE with more minor ones (e.g., protein fractions at > 55 or 25-37 kDa) in suspensions. Extraction pH had limited effect on the secondary structure of QPI. In contrast, the higher-order structures of QPI were significantly affected, e.g., (1) emission maximum wavelength of intrinsic fluorescence increased with extraction pH; (2) surface hydrophobicity and the absolute value of zeta-potential increased with increasing extraction pH from 7 to 9, and then markedly decreased; (3) the particle size decreased to the lowest value at pH 9 and then increased to the highest value at pH 11; and (4) denaturation temperature of QPI had a large decrease with increasing extraction pH from 7/8 to 9/10. Besides, heat-set QPI gels were formed by loosely-connected protein aggregates, which were strengthened with increasing extraction pH. This study would provide fundamental data for industrial production of quinoa protein with desired quality.

The Evolution of Commercial Antibody Formulations

It has been nearly four decades since the first therapeutic monoclonal antibodies were approved and made available for widespread human use. Herein, US and EU approved antibody formulations are reviewed, and their nature and compositions are evaluated over time. From 1986 through Jan 2023, significant formulation trends have occurred and to represent this, 165 commercial antibody therapeutic formulations were binned into 5 different periods of time. Overall, we have observed the following: 1) The average formulation pH has decreased in recent years by over 0.5 units along with a decrease in variability that is largely driven by non-high concentration liquid in vial presentations for IV administration, 2) The use of certain excipients and buffers such as histidine, sucrose, metal chelators, arginine and methionine has become significantly more common, whereas formulations that contain phosphate, salt, no sugar or no surfactant have fallen out of favor, 3) Overall formulation space has increasingly become more homogenous and has converged in terms of formulation pH and excipient preferences regardless of formulation concentration, drug product presentation, and route of administration, 4) The average calculated isoelectric point (pI) has decreased 0.26 units, and 5) Overall, the average formulation pH and calculated pI for all commercial antibodies surveyed was 6.0 and 8.4, respectively. These trends and formulation convergence may be driven by multiple factors such as advancements in high-throughput computational and analytical technologies, the increased emphasis and understanding of certain developability attributes and formulation principles during lead selection and formulation development, and the adoption of low-risk development platform approaches.

Small angle X-ray scattering investigation of ionic liquid effect on the aggregation behavior of globular proteins

Globular proteins are well-folded model proteins, where ions can substantially influence their structure and aggregation. Ionic liquids (ILs) are salts in the liquid state with versatile ion combinations. Understanding the IL effect on protein behavior remains a major challenge. Here, we employed small angle X-ray scattering to investigate the effect of aqueous ILs on the structure and aggregation of globular proteins, namely, hen egg white lysozyme (Lys), human lysozyme (HLys), myoglobin (Mb), β-lactoglobulin (βLg), trypsin (Tryp) and superfolder green fluorescent protein (sfGFP). The ILs contain ammonium-based cations paired with the mesylate, acetate or nitrate anion. Results showed that only Lys was monomeric, whereas the other proteins formed small or large aggregates in buffer. Solutions with over 17 mol% IL resulted in significant changes in the protein structure and aggregation. The Lys structure was expanded at 1 mol% but compact at 17 mol% with structural changes in loop regions. HLys formed small aggregates, with the IL effect similar to Lys. Mb and βLg mostly had distinct monomer and dimer distributions depending on IL type and IL concentration. Complex aggregation was noted for Tryp and sfGFP. While the anion had the largest ion effect, changing the cation also induced the structural expansion and protein aggregation.

A double point mutation of SOD1 targeting net charge promotes aggregation under destabilizing conditions: Correlation of charge distribution and ALS-provoking mutation

A progressive neurodegenerative illness such as amyotrophic lateral sclerosis (ALS) is characterized by the misfolding and aggregation of human CuZn superoxide dismutase (hSOD1) into amyloid aggregates. Thus, designing strategies for the choice of WT-SOD1 and double mutant (G12D/G138E) with an increased net negative charge can be a good idea to elucidate the pathological mechanism of SOD1 in ALS under some destabilizing conditions. Consequently, we show evidence that protein charge, together with other destabilizing conditions, plays an important role in ALS disease. To achieve this purpose, we use methods, such as spectroscopy and transmission electron microscopy (TEM) to monitor the formation of amyloid aggregation. The specific activity of WT-SOD1 was approximately 1.72 times higher than that of the double mutant. Under amyloidogenic circumstances, structural properties such as local, secondary, oligomeric, and fibrillar structures were explored. The double mutant's far-UV CD spectra displayed a broad minimum peak in the region 213 to 218 nm, suggesting the production of β-rich amyloid fibrils. FTIR spectra of the double mutant samples at different incubation times showed a low-frequency peak around 1630-1640 cm^-1, attributed to a parallel β-sheet. Moreover, CR-binding assay and TEM analysis revealed and confirmed that mutation with an increased repulsive charge promotes the formation of fibrous aggregates. Consequently, ALS mutations with a higher repulsive charge are the apparent exceptions that validate the rule. This findings revealed that the double mutant increases protein aggregation through a novel mechanism, likely involving destabilization of structure and a change in the net negative charge.