Characteristics of Sugar Surfactants in Stabilizing Proteins During Freeze–Thawing and Freeze–Drying

Optimization of lyoprotectant for recombinant human acidic fibroblast growth factor by response surface methodology

Recombinant human acidic fibroblast growth factor (rh-aFGF) is a widely used biological product, but it is unstable and its biological activity is easy to decrease. In order to maintain the long-term stability and biological activity of rh-aFGF, based on the response surface method, the freeze-drying characterization and cell proliferation rate of rh-aFGF freeze-dried powder were evaluated by scoring and Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay in this study. The optimal concentrations of trehalose, glycine and BSA were optimized, and the optimal formulation was verified by regression experiment. The results showed that trehalose, glycine and BSA had significant effects on the characterization of lyophilized rh-aFGF and cell proliferation. The optimal formulation of 5.7% trehalose, 2.04% glycine and 1.98%BSA combined with rh-aFGF could achieve the optimal freeze-dried characterization and biological activity. Using the best formulation to verify, the freeze-dried formability index of the freeze-dried powder was 23.35, and the rate of cell proliferation was 43.59%, which was close to the expected 23 and 41.69%. This study determined a freeze-dried formulation of rh-aFGF that meets the requirements of freeze-dried formalization integrity and maintains biological activity, providing reliable support for the subsequent development of related drugs.

Design of an Ice Recrystallization-Inhibiting Polyampholyte-Containing Graft Polymer for Inhibition of Protein Aggregation

Freezing-induced damage to proteins, through osmotic stress and ice recrystallization, during protein processing and long-term storage is a serious concern and may lead to loss of protein activity owing to denaturation. In this study, graft copolymers composed of a cryoprotective polymer (capable of preventing osmotic stress) and poly(vinyl alcohol) (PVA; known for its high ice recrystallization inhibition (IRI) property) were developed. The polymers had high IRI activity, albeit slightly lower than that of PVA alone, but substantially higher than that of succinylated ε-poly-l-lysine (PLLSA) alone. The graft polymers showed an efficiency higher than that of PVA or PLLSA alone in protecting proteins from multiple freeze-thaw cycles, as well as during prolonged freezing, indicating a synergy between PVA and PLLSA. The PLLSA-based graft polymer is a promising material for use in protein biopharmaceutics for the long-term storage of proteins under freezing conditions.

Tween® Preserves Enzyme Activity and Stability in PLGA Nanoparticles

Enzymes, as natural and potentially long-term treatment options, have become one of the most sought-after pharmaceutical molecules to be delivered with nanoparticles (NPs); however, their instability during formulation often leads to underwhelming results. Various molecules, including the Tween^® polysorbate series, have demonstrated enzyme activity protection but are often used uncontrolled without optimization. Here, poly(lactic-co-glycolic) acid (PLGA) NPs loaded with β-glucosidase (β-Glu) solutions containing Tween^® 20, 60, or 80 were compared. Mixing the enzyme with Tween^® pre-formulation had no effect on particle size or physical characteristics, but increased the amount of enzyme loaded. More importantly, NPs made with Tween^® 20:enzyme solutions maintained significantly higher enzyme activity. Therefore, Tween^® 20:enzyme solutions ranging from 60:1 to 2419:1 mol:mol were further analyzed. Isothermal titration calorimetry analysis demonstrated low affinity and unquantifiable binding between Tween^® 20 and β-Glu. Incorporating these solutions in NPs showed no effect on size, zeta potential, or morphology. The amount of enzyme and Tween^® 20 in the NPs was constant for all samples, but a trend towards higher activity with higher molar rapports of Tween^® 20:β-Glu was observed. Finally, a burst release from NPs in the first hour with Tween^®:β-Glu solutions was the same as free enzyme, but the enzyme remained active longer in solution. These results highlight the importance of stabilizers during NP formulation and how optimizing their use to stabilize an enzyme can help researchers design more efficient and effective enzyme loaded NPs.

Applying text mining to identify relevant literature in food science: Cold denaturation as a case study

In a research environment characterized by the five V's of big data, volume, velocity, variety, value, and veracity, the need to develop tools that quickly screen a large number of publications into relevant work is an increasing area of concern, and the data-rich food industry is no exception. Here, a combination of latent Dirichlet allocation and food keyword searches were employed to analyze and filter a dataset of 6102 publications about cold denaturation. After using the Python toolkit generated in this work, the approach yielded 22 topics that provide background and insight on the direction of research in this field, as well as identified the publications in this dataset which are most pertinent to the food industry with precision and recall of 0.419 and 0.949, respectively. Precision is related to the relevance of a paper in the filtered dataset and the recall represents papers which were not identified in the screening method. Lastly, gaps in the literature based on keyword trends are identified to improve the knowledge base of cold denaturation as it relates to the food industry. This approach is generalizable to any similarly organized dataset, and the code is available upon request. Practical Application: A common problem in research is that when you are an expert in one field, learning about another field is difficult, because you may lack the vocabulary and background needed to read cutting edge literature from a new discipline. The Python toolkit developed in this research can be applied by any researcher that is new to a field to identify what the key literature is, what topics they should familiarize themselves with, and what the current trends are in the field. Using this structure, researchers can greatly speed up how they identify new areas to research and find new projects.

Challenges and Opportunities for Clustered Regularly Interspaced Short Palindromic Repeats Based Molecular Biosensing

Clustered regularly interspaced short palindromic repeats, CRISPR, has recently emerged as a powerful molecular biosensing tool for nucleic acids and other biomarkers due to its unique properties such as collateral cleavage nature, room temperature reaction conditions, and high target-recognition specificity. Numerous platforms have been developed to leverage the CRISPR assay for ultrasensitive biosensing applications. However, to be considered as a new gold standard, several key challenges for CRISPR molecular biosensing must be addressed. In this paper, we briefly review the history of biosensors, followed by the current status of nucleic acid-based detection methods. We then discuss the current challenges pertaining to CRISPR-based nucleic acid detection, followed by the recent breakthroughs addressing these challenges. We focus upon future advancements required to enable rapid, simple, sensitive, specific, multiplexed, amplification-free, and shelf-stable CRISPR-based molecular biosensors.

The need for novel cryoprotectants and cryopreservation protocols: Insights into the importance of biophysical investigation and cell permeability

BACKGROUND

Cryopreservation is a key method of preservation of biological material for both medical treatments and conservation of endangered species. In order to avoid cellular damage, cryopreservation relies on the addition of a suitable cryoprotective agent (CPA). However, the toxicity of CPAs is a serious concern and often requires rapid removal on thawing which is time consuming and expensive.

SCOPE OF REVIEW

The principles of Cryopreservation are reviewed and recent advances in cryopreservation methods and new CPAs are described. The importance of understanding key biophysical properties to assess the cryoprotective potential of new non-toxic compounds is discussed.

MAJOR CONCLUSIONS

Knowing the biophysical properties of a particular cell type is crucial for developing new cryopreservation protocols. Similarly, understanding how potential CPAs interact with cells is key for optimising protocols. For example, cells with a large osmotically inactive volume may require slower addition of CPAs. Similarly, a cell with low permeability may require a longer incubation time with the CPA to allow adequate penetration. Measuring these properties allows efficient optimisation of cryopreservation protocols.

GENERAL SIGNIFICANCE

Understanding the interplay between cells and biophysical properties is important not just for developing new, and better optimised, cryopreservation protocols, but also for broader research into topics such as dehydration and desiccation tolerance, chilling and heat stress, as well as membrane structure and function.

The Use of a Combination of a Sugar and Surfactant to Stabilize Au Nanoparticle Dispersion against Aggregation during Freeze-Drying

Drying a suspension of nanoparticles typically results in the irreversible aggregation of nanoparticles; however, solutions that contain unstable ingredients are often converted into dried powders to prolong their shelf lives. In this study, the use of a combination of a surface-active agent and sugar was investigated with regard to avoiding the aggregation of nanoparticles during drying. Suspensions of Au nanoparticles (∼60 nm diameter, AuNPs) were freeze-dried in the presence of different combinations of various sugars with a surfactant. Sucrose monopalmitate (SEC16) was mainly used as the surfactant, based on a comparison of antiaggregation effects conferred by various surfactants. The freeze-dried AuNP suspension was then reconstituted, and the avoidance of AuNP aggregation was then examined. The results demonstrated that the use of a combination of a small amount of SEC16 and sugar resulted in a greater redispersibility of AuNPs after freeze-drying than when the individual components were used. Repetition tests of freeze-drying and reconstitution were conducted. The sucrose/SEC16 mixture was freeze-dried on an electroless-plated Au film and then analyzed by infrared spectroscopy. Strong interactions between SEC16 and the Au surface were detected, and these interactions appear to play a crucial role in the antiaggregation of AuNPs during freeze-drying.

Synthesis, Surface and Antimicrobial Activity of New Lactose-Based Surfactants

This work presents a synthesis method for new surfactants based on lactose. The compounds obtained belong to the homologous series of O-β-D-Galactopyranosyl-(1→4)-N-alkyl-(3-sulfopropyl)-D-glucosamine hydrochloride, containing 12 and 14 carbon atoms in the alkyl chain, and they may serve as an example of cationic surfactants. The newly synthesized compounds exhibit good surface properties, low value of CMC (Critical Micelle Concentration) and good wetting properties. These surfactants' ability to produce foam is considerably higher than in the commercial surfactants. Moreover, antibacterial and fungistatic activity was carried out by well diffusion assay against the selected bacteria (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa), yeasts (Candida albicans) and filamentous fungi (Fusarium graminearum, F. avenaceum, F. oxysporum, F. culmorum, F. equiseti, Alternaria alternata and Botrytis cinerea). It was shown that the resulting quaternary salts significantly inhibit the growth of tested microorganisms. Antibacterial and fungistatic activity of the surfactant compounds varied depending on the species of bacteria or fungi. The results of antimicrobial activity of new lactose derivatives indicate that the compounds exhibit larger or similar antagonistic activity against tested bacteria and fungi than typical cationic surfactant cetylpyridinium chloride.

Stabilization of enzyme-immobilized hydrogels for extended hypoxic cell culture

In this work, glucose oxidase (GOx)-immobilized hydrogels are developed and optimized as an easy and convenient means for creating solution hypoxia in a regular incubator. Specifically, acrylated GOx co-polymerizes with poly(ethylene glycol) diacrylate (PEGDA) to form PEGDA-GOx hydrogels. Results show that freeze-drying and reaction by-products, hydrogen peroxide, negatively affect oxygen-consuming activity of network-immobilized GOx. However, the negative effects of freeze-drying can be mitigated by addition of trehalose/raffinose in the hydrogel precursor solution, whereas the inhibition of GOx caused by hydrogen peroxide can be prevented via addition of glutathione (GSH) in the buffer/media. The ability to preserve enzyme activity following freeze-drying and during long-term incubation permits facile application of this material to induce long-term solution/media hypoxia in cell culture plasticware placed in a regular CO₂ incubator.

n-Octyl (Thio)glycosides as Potential Cryoprotectants: Glass Transition Behaviour, Membrane Permeability, and Ice Recrystallization Inhibition Studies

A series of eight n-octyl (thio)glycosides (1α, β–4α, β) with d-glucose or d-galactose-configured head groups and varying anomeric configuration were synthesized and evaluated for glass transition behaviour, membrane permeability, and ice recrystallization inhibition (IRI) activity. Of these, n-octyl β-d-glucopyranoside (2β) exhibited a high glass transition temperatures (Tg), both as a neat sample and 20 wt-% aqueous solution. Membrane permeability studies of this compound revealed cellular uptake to concentrations relevant to the inhibition of intracellular ice formation, thus presenting a promising lead candidate for further biophysical and cryopreservation studies. Compounds were also evaluated as ice recrystallization inhibitors; however, no detectable activity was observed for the newly tested compounds.

Production of proteases from organic wastes by solid-state fermentation: downstream and zero waste strategies

Production of enzymes through solid-state fermentation (SSF) of agro-industrial wastes reports high productivity with low investment. The extraction of the final product from the solid waste and solid disposal represent the main cost of the process. In this work, the complete downstream processes of SSF of two industrial residues for the production of proteases, soy fibre (SF) and a mixture of hair and sludge (HS), were studied in terms of activity recovery, using different extraction parameters (extracting solvent, ratio solid: solvent and extraction mode). Activity after lyophilisation was tested. Solid waste valorisation after extraction was studied using respiration techniques and biogas production tests, as part of a zero waste strategy. Results showed a maximum extraction yield of 91% for SF and 121% for HS, both in agitated mode and distilled water as extraction agent. An average activity recovery of 95 ± 6 and 94 ± 6% for SF and HS, respectively, was obtained after lyophilisation and redissolution. To reduce the cost of extraction, a ratio 1:3 w:v solid-solvent in static mode is advised for SF, and 1:2 w:v extraction ratio in agitated mode for HS, both with distilled water as extracting agent. Both composting and anaerobic digestion are suitable techniques for valorisation of the waste material.

Characteristics of proteinaceous additives in stabilizing enzymes during freeze-thawing and -drying

Protein-stabilizing characteristics of sixteen proteins during freeze-thawing and freeze-drying were investigated. Five enzymes, each with different instabilities against freezing and dehydration, were employed as the protein to be stabilized. Proteinaceous additives generally resulted in greater enzyme stabilization during freeze-thawing than sugars while the degree of stabilization for basic lysozyme and protamine were inferior to that of neutral and acidic proteins. Freeze-drying-induced inactivation of enzyme was also reduced by the presence of a proteinaceous additive, the extent of which was lower than that for a sugar. In both freeze thawing and freeze drying, the enzymes stabilization by the proteinaceous additive increased with increasing additive concentration. The enhancement of enzyme inactivation caused by pH change was also reduced in the presence of proteinaceous additives. The combined use of a sugar such as sucrose and dextran tended to increase the stabilizing effect of the proteinaceous additive.

Oligosaccharide-based Surfactant/Citric Acid Buffer System Stabilizes Lactate Dehydrogenase during Freeze-drying and Storage without the Addition of Natural Sugar

Experiments were conducted to assess the maintenance effects of oligosaccharide-based surfactants on the enzymatic activity of a model protein, lactate dehydrogenase (LDH), during freeze-drying and room temperature storage using the citric acid buffer system. Oligosaccharide-based surfactants, which exhibit a high glass transition temperature (Tg), promoted the eminent retention of enzymatic activity during these protocols, whereas monosaccharide-based surfactants with a low Tg displayed poor performance at high concentration, albeit much better than that of Tween 80 at middle concentration. The increase in the alkyl chain length did not exert positive effects as observed for the maintenance effect during freeze-thawing, but an amphiphilic nature and a glass forming ability were crucial for the effective stabilization at a low excipient concentration during freeze-drying. Even a low oligosaccharide-based surfactant content (0.1 mg mL(-1)) could maintain LDH activity during freeze-drying, but a high surfactant content (1.0 mg mL(-1)) was required to prevent buffer precipitation and retain high LDH activity on storage. Regarding storage, glass formation restricted molecular mobility in the lyophilized matrix, and LDH activity was effectively retained. The present results describe a strategy based on the glass-forming ability of surfactant-type excipients that affords a natural sugar-free formulation or an alternative use for polysorbate-type surfactants.

Addressing Barriers to the Development and Adoption of Rapid Diagnostic Tests in Global Health

Immunochromatographic rapid diagnostic tests (RDTs) have demonstrated significant potential for use as point-of-care diagnostic tests in resource-limited settings. Most notably, RDTs for malaria have reached an unparalleled level of technological maturity and market penetration, and are now considered an important complement to standard microscopic methods of malaria diagnosis. However, the technical development of RDTs for other infectious diseases, and their uptake within the global health community as a core diagnostic modality, has been hindered by a number of extant challenges. These range from technical and biological issues, such as the need for better affinity agents and biomarkers of disease, to social, infrastructural, regulatory and economic barriers, which have all served to slow their adoption and diminish their impact. In order for the immunochromatographic RDT format to be successfully adapted to other disease targets, to see widespread distribution, and to improve clinical outcomes for patients on a global scale, these challenges must be identified and addressed, and the global health community must be engaged in championing the broader use of RDTs.

Design of experiments reveals critical parameters for pilot-scale freeze-and-thaw processing of L-lactic dehydrogenase

Freezing constitutes an important unit operation of biotechnological protein production. Effects of freeze-and-thaw (F/T) process parameters on stability and other quality attributes of the protein product are usually not well understood. Here a design of experiments (DoE) approach was used to characterize the F/T behavior of L-lactic dehydrogenase (LDH) in a 700-mL pilot-scale freeze container equipped with internal temperature and pH probes. In 24-hour experiments, target temperature between -10 and -38°C most strongly affected LDH stability whereby enzyme activity was retained best at the highest temperature of -10°C. Cooling profile and liquid fill volume also had significant effects on LDH stability and affected the protein aggregation significantly. Parameters of the thawing phase had a comparably small effect on LDH stability. Experiments in which the standard sodium phosphate buffer was exchanged by Tris-HCl and the non-ionic surfactant Tween 80 was added to the protein solution showed that pH shift during freezing and protein surface exposure were the main factors responsible for LDH instability at the lower freeze temperatures. Collectively, evidence is presented that supports the use of DoE-based systematic analysis at pilot scale in the identification of F/T process parameters critical for protein stability and in the development of suitable process control strategies.