Optical cryomicroscopy and differential scanning calorimetry of buffer solutions containing cryoprotectants

Interaction of L-proline with water and ice: Implications for Litopenaeus Vannamei Cryoprotection during temperature fluctuation

Temperature fluctuations can negatively affect the quality of frozen shrimp. Research on novel cryoprotectants to replace traditional agents (phosphate, etc.) has become a hotspot. Our results indicated that L-Proline could reduce thawing losses, delay texture deterioration and improve the functional properties of myofibrillar proteins of shrimp. Thawing loss in the proline group (3.2 %) was significantly lower than that in the control (5.4 %) after 3 freeze-thaw cycles (p < 0.05). Compared to Na4P2O7, proline had better permeability and greater ability to inhibit ice crystal growth and volume expansion. Through molecular simulations, we found that proline might inhibit ice crystal formation by forming glassy states with water. Hydrogen bonding between proline and water/ice played a major role, and only a small amount of proline was required to significantly reduce the ice crystal growth rate from 0.16 m/s to 0.06 m/s. Briefly, proline exhibited potential as a cryoprotectant for shrimp in temperature fluctuations.

"Anchoring Capture" Effect Mimicking Proline in Hardy Deep-Sea Fish to Stabilize the Zinc Anode with Lower Operating Temperature

The low plating/stripping efficiency of zinc anodes, dendrite growth, and high freezing points of aqueous solutions hinder the practical application of aqueous zinc-ion batteries. This paper proposes a zwitterionic permeable network solid-state electrolyte based on the "anchor-capture" effect to address these problems by incorporating proline (Pro, a biological antifreeze agent) into the electrolyte. Extensive validation tests, Quantum Chemistry (QC) calculations, Molecular Dynamics (MD) Simulations, and ab initio molecular dynamics simulations consistently indicate that the amino groups in proline adsorb onto the Zn metal surface, stabilizing the zinc anode-electrolyte interface, suppressing side reactions from water decomposition, and homogenizing zinc-ion flux. This electrolyte demonstrates excellent reversibility in Zn-Mn2O3 cells and Zn-Zn half-cells, achieving a high coulombic efficiency of over 99.4% across 2000 cycles in Zn-Mn2O3 full cells, and delivering a discharge-specific capacity of 175.2 mAh g-1 at -35 °C and 1 A g-1. Additionally, an appropriate concentration of proline lowers the electrolyte's freezing point to -45 °C through the network's solid-state effect, ensuring the stable operation of the solid-state battery at -35 °C. This innovative concept of network solid-state electrolytes injects new vitality into the development of multifunctional solid-state electrolytes.

Histidine as a versatile excipient in the protein-based biopharmaceutical formulations

Adequate stabilization is essential for marketed protein-based biopharmaceutical formulations to withstand the various stresses that can be exerted during the pre- and post-manufacturing processes. Therefore, a suitable choice of excipient is a significant step in the manufacturing of such delicate products. Histidine, an essential amino acid, has been extensively used in protein-based biopharmaceutical formulations. The physicochemical properties of histidine are unique among amino acids and could afford multifaceted benefits to protein-based biopharmaceutical formulations. With a pKa of approximately 6.0 at the side chain, histidine has been primarily used as a buffering agent, especially for pH 5.5-6.5. Additionally, histidine exhibited several affirmative properties similar to those of carbohydrates (e.g., sucrose and trehalose) and could therefore be considered to be an alternative approach to established protein-based formulation strategies. The current review describes the general physicochemical properties of histidine, lists all commercial histidine-containing protein-based biopharmaceutical products, and discusses a brief outline of the existing research focused on the versatile applications of histidine, which can act as a buffering agent, stabilizer, cryo-/lyo-protectant, antioxidant, viscosity reducer, and solubilizing agent. The interaction between histidine and proteins in protein-based biopharmaceutical formulations, such as the Donnan effect during diafiltration of monoclonal antibody solutions and the degradation of polysorbates in histidine buffer, has also been discussed. As the first review of histidine in protein biopharmaceuticals, it helps to deepen our understanding of the opportunities and challenges associated with histidine as an excipient for protein-based biopharmaceutical formulations.

Molecular modelling studies reveal cryoprotective mechanism of L-Proline during the frozen storage of shrimp (Litopenaeus vannamei)

This study aimed to investigate the cryoprotective properties of proline (1% and 3% (w/v)) on shrimp. The cryoprotective mechanism was studied using physico-chemical experiments and molecular simulations. Proline had a notable positive impact on the thawing loss and texture of shrimp in comparison to the control. The denaturation of myosin in frozen shrimp was delayed by proline. Microscopy analysis demonstrated that proline effectively lowered the harm caused by ice crystals to shrimp muscle. Molecular simulations indicated that proline potentially exerted a cryoprotective effect primarily through the "water substitution" and "glassy state" hypotheses. Proline formed hydrogen bonds with myosin to replace the water molecules around myosin. Additionally, proline interacted with water molecules to form a glassy state, impeding the growth of ice crystals. Consequently, the stability of shrimp myosin was enhanced during freezing. In conclusion, proline demonstrated promise as an efficacious cryoprotectant for aquatic products.

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.

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.

Investigating freezing-induced acidity changes in citrate buffers

Citrate buffers are commonly utilized in the field of biomolecule stabilization. We investigate their applicability in the frozen state within a range of initial pHs (2.5 to 8.0) and concentrations (0.02 to 0.60 M). Citrate buffer solutions subjected to various cooling and heating temperatures are examined in terms of the freezing-induced acidity changes, revealing that citrate buffers acidify upon cooling. The acidity is assessed with sulfonephthalein molecular probes frozen in the samples. Optical cryomicroscopy combined with differential scanning calorimetry was employed to investigate the causes of the observed acidity changes. The buffers partly crystallize and partly vitrify in the ice matrix; these processes influence the resulting pH and allow designing the optimal storage temperatures in the frozen state. The freezing-induced acidification apparently depends on the buffer concentration; at each pH, we suggest pertinent concentration, at which freezing causes minimal acidification.

Study of Oncolytic Virus Preservation and Formulation

In recent years, oncolytic viruses (OVs) have emerged as an effective means of treating cancer. OVs have multiple oncotherapeutic functions including specifically infecting and lysing tumor cells, initiating immune cell death, attacking and destroying tumor angiogenesis and triggering a broad bystander effect. Oncolytic viruses have been used in clinical trials and clinical treatment as drugs for cancer therapy, and as a result, oncolytic viruses are required to have long-term storage stability for clinical use. In the clinical application of oncolytic viruses, formulation design plays a decisive role in the stability of the virus. Therefore, this paper reviews the degradation factors and their degradation mechanisms (pH, thermal stress, freeze-thaw damage, surface adsorption, oxidation, etc.) faced by oncolytic viruses during storage, and it discusses how to rationally add excipients for the degradation mechanisms to achieve the purpose of maintaining the long-term stability of oncolytic viral activity. Finally, the formulation strategies for the long-term formulation stability of oncolytic viruses are discussed in terms of buffers, permeation agents, cryoprotectants, surfactants, free radical scavengers, and bulking agent based on virus degradation mechanisms.

Raman Marker Bands for Secondary Structure Changes of Frozen Therapeutic Monoclonal Antibody Formulations During Thawing

In this work we use Raman spectroscopy for protein characterization in the frozen state. We investigate the behavior of frozen therapeutic monoclonal antibody IgG1 formulation upon thawing by Raman spectroscopy. Secondary and tertiary structure of the protein in three different mab formulations in the frozen state are followed through observation of marker bands for α-helix, β-sheet and random coil. We identify the tyrosine intensity ratio I₈₅₆/I₈₃₀ as a marker for mab aggregation. Upon fast cooling (40 °C/min) to -80 °C we observe a significant increase of random coil and α -helical structures, while this is not the case for slower cooling (20 °C/min) to -80 °C. Most changes in the protein's secondary structure are observed in the course of thawing in the range up to -20 °C, when passing through the glass transitions and cold-crystallization of the two types of freeze-concentrated solutions formed through macro- and microcryoconcentration. An increase of protein concentration and the addition of mannitol suppress secondary structural changes but do no impact on aggregation.

Preparation of Curcumin Solid Lipid Nanoparticles Loaded with Flower-Shaped Lactose for Lung Inhalation and Preliminary Evaluation of Cytotoxicity In Vitro

The purpose of this study is to design a flower-shaped lactose loaded curcumin solid lipid nanoparticles dry powder inhaler and characterize it to improve the solubility and dissolution rate of curcumin in lung. Curcumin solid lipid nanoparticles (Cur-SLNs) were prepared by solvent evaporation method, and then they were micronized by freeze-drying technology. Finally, Cur-SLN micropowder obtained by freeze-drying was mixed with flower-shaped lactose (FL) at a ratio of 2 : 1 and then passed through a 200-mesh sieve to obtain Cur-SLN-FL powder. Tween-80 was selected as the surfactant to inhibit the aggregation of drug solid lipid nanoparticles. Under the optimum conditions, the solid lipid nanoparticles (SLN) were relatively spherical, with an average particle size of 14.7 nm, narrow distribution, Zeta potential of -22.5 mV, encapsulation efficiency of 90.21%, and drug loading of 8.56%. According to the particle size, PI, Zeta potential, drug loading (LC%), encapsulation efficiency (EE%), morphology, and in vitro release characteristics, the prescription of solid lipid nanoparticles was screened. Dry powder inhaler (DPI) was characterized by differential scanning calorimetry, scanning electron microscopy, particle size, density, and in vitro release performance. Its cytotoxicity to mouse fibroblasts (L929) and human normal lung epithelial cells (BEAS-2B) in vitro was investigated, and its safety for pulmonary inhalation was preliminarily determined. FTIR analysis shows that the micronized Cur-SLN-FL has the same chemical structure as FL. FTIR and DSC analysis confirmed that the characteristic absorption peak of curcumin was not found in Cur-SLN-FL, showing similar structure to SLN and FL. In addition, curcumin was coated in solid lipid nanoparticles to make powder mist, which increased its drug loading, kept its aerodynamic particle size (4.03 ± 0.40) μm, and significantly improved its drug release performance in artificial lung fluid. In vitro cytotoxicity test results confirmed that Cur-SLN-FL was less toxic to BEAS-2B cells than L929 cells. Therefore, curcumin was prepared into solid lipid nanoparticles by emulsion evaporation-low temperature solidification method and then micronized and mixed with FL to prepare curcumin solid lipid nanoparticle powder mist loaded with flower-shaped lactose. The process is simple and feasible, and it has better safety performance for lung cells, which is expected to become a safe and effective delivery system for pulmonary inhalation drugs.