Current technologies to endotoxin detection and removal for biopharmaceutical purification

Novel processes to obtain pneumococcal surface proteins for vaccines

Current pneumococcal vaccines are based on the protection offered by capsular polysaccharides from only a few from > 100 serotypes; therefore, serotype-independent vaccines composed of pneumococcal surface proteins are being developed. Despite the immense number of publications on the discovery, characterization, and evaluation of new pneumococcal vaccine candidates, there are very few that describe the bioprocess development, which is an essential step to generate material for pre-clinical and clinical tests, to obtain enough protein amount for physical-chemical, biochemical, and biological characterization, and to understand critical product and process attributes. Here, aspects of production and purification processes of pneumococcal surface proteins are reviewed, the most common bioreactor cultivation strategies are discussed, and important features of the purification process are explored to bring new insights about the correlation between protein structure and chromatography. The process development oriented to an industrial scale is an essential step for the success of novel protein-based pneumococcal vaccines and can preclude problems that could be hardly identified at flask scale production. Moreover, the early bioprocess development should favor a smooth scale-up and transfer of the process to GMP facilities for future production of new pneumococcal vaccines. KEY POINTS: • Early bioprocess development is crucial to advancing pneumococcal protein vaccines. • Bioreactor cultivation can help to identify possible process bottlenecks. • Structural features of similar proteins can orient purification process development.

Effectiveness of manufacturing annealing temperature on sterilization and depyrogenation of closed ampoules compared with other techniques

The presence of endotoxin in the bloodstream can lead to unexpected fever and, in severe cases, endotoxemia and bacteremia that can lead to death. The reduction of bacterial endotoxin, known as depyrogenation, is crucial for preparing primary packaging components like ampoules for use in injectable drug products. The durability of glass ampoules depends on the proper annealing process. If glass is not annealed correctly, it is prone to cracking or shattering from even small changes in temperature or from mechanical shock or stress. To evaluate the effectiveness of sterilization and depyrogenation, a dry heat oven at 250°C was used for 30 minutes. The Limulus Amebocyte Lysate (LAL) assay was utilized to detect endotoxin, and efficient sterilization and depyrogenation were observed at this temperature. The impact of heating glass ampoules to various temperatures on the process of sterilization and depyrogenation was studied. This investigation covered a range of temperatures (250°C - 550°C), and included holding stage times (105, 120, and 200 seconds) corresponding to the belt speed. The removal of endotoxins was achieved by exposing to temperatures from 350°C to 550°C for specific time intervals and at 300°C with an exposure time of 200 seconds. The absence of endotoxin was observed when annealing glass ampoules at 500°C for 105 seconds, regardless of the ampoules' size. Alternative methods for testing depyrogenation of sealed ampoules, such as ethylene oxide (EtO), sodium hydroxide (NaOH), and hydrochloric acid (HCl), were also demonstrated to have a clear comparison against temperature which considered the best effective economic method . This research indicates that annealing sealed glass ampoules at specific temperatures can serve as a replacement for sterilization and depyrogenation processes prior to filling, leading to savings in time, labor, machine work, energy, and cost.

Collagen Hydrolysates as Nutritional Support in Canine Osteoarthritis: A Narrative Review

Osteoarthritis (OA) is a common disease in dogs with severe impact on their welfare. The multimodal management of OA includes feeding therapeutic diets and nutraceuticals to slow down OA progression. Collagen hydrolysates (CH) are a nutritional supplement that may exert anabolic effects on osteoarthritic joint cartilage as well as disease-modifying effects. After oral intake, CH is absorbed, mainly as amino acids, di- and tripeptides that are transported amongst others to the joint. In addition to reducing cartilage degradation, CH metabolites may reduce synovial inflammation and subchondral bone sclerosis during OA. Preliminary evidence in dogs suffering from the consequences of OA support the clinical efficacy of CH with reported reductions in lameness. However, effects on biomarker level of cartilage metabolism and inflammation are inconclusive. Additionally, current studies show a lack of standardised dosing regimens and the use of not validated outcomes. Future work should therefore elucidate further on the bioavailability of CH in dogs in order to establish adequate dosing recommendations. Furthermore, high-quality placebo-controlled randomised controlled trials are essential to dstudies have evaluated the cetermine the clinical efficacy of CH to reduce lameness, prevent OA progression and thereby improve the level of evidence.

Cleaning methods for biosafety cabinet to eliminate residual mycoplasmas, viruses, and endotoxins after changeover

Introduction

Cell-processing operations can potentially contaminate biosafety cabinets, which should be maintained sterile. However, unintended contamination can occur owing to the presence of viruses, mycoplasmas, and bacteria in the raw materials. Moreover, although several methods for expunging these contaminants have been proposed, an optimal method has not yet been determined. Additionally, the effectiveness of conventional methods for eliminating these contaminants remains unclear owing to their unique characteristics and potential resistances to cleaning. Therefore, this paper proposes a risk-based approach to identify appropriate cleaning methods and reduce the likelihood of cross-contamination in biosafety cabinets by these contaminants.

Methods

Various cleaning methods for eliminating mycoplasmas, viruses, and endotoxins from biosafety cabinets were evaluated, including ultraviolet (UV) irradiation at 200 mJ/cm2 for 20 min and wiping with disinfectants such as distilled water, benzalkonium chloride (BKC), and 70 % ethanol (ETH). The effectiveness of each method was evaluated by applying the contaminants on stainless steel plates and cleaning them using each method. Mycoplasma orale was cultured for 2 weeks in a liquid medium after cleaning. Feline calicivirus (FCV) was used for evaluating the virus-cleaning effectiveness and its presence was tested using the TCID50 test, whereas endotoxins obtained from the dried extract of Escherichia coli were measured via endotoxin testing.

Results

UV irradiation and wiping with BKC inhibited the growth of mycoplasma and significant decreased their presence compared with the other cleaning methods. Notably, mycoplasma were detected after wiping all SUS304 plates with ETH, which is a widely used cleaning method. Additionally, the cleaning efficacy for virus showed that the TCID50 of the wet group was 132,000 TCID50/plate, whereas those after UV irradiation or cleaning with BKC or DW were below the detection limit. Finally, UV irradiation did not significantly reduce the endotoxin production compared with that in the dry group. Additionally, wiping with ETH did not significantly reduce endotoxins compared with the dry group and their residues were higher than those detected after wiping with BKC or DW.

Conclusions

The changeover protocols currently employed in most cell-processing facilities may be ineffective as pathogenic or nonpathogenic materials may remain even after ETH wiping, leading to unintended cross-contamination. To the best of our knowledge, this is the first study to provide reference data of different cleaning methods for mycoplasmas, viruses, and endotoxins in cell-product manufacturing facilities, and can potentially support the development of evidence-based management strategies for ensuring safe cell-product processing.

Bifunctional sheets reduce the microbe and endotoxin contamination of tissue-derived collagen

Tendon-derived type I collagen is an essential biomaterial for various biomedical devices due to its inherent bioactivity and favorable environment for cells. Correspondingly, microbial and endotoxin contamination can be easily introduced during the collagen extraction process, which is generally overlooked in fundamental scientific research, especially the endotoxin residue. Conventional approaches for mitigating endotoxin exhibit limited effectiveness when applied to biomacromolecule products because of viscosity, clogging, and diminished bioactivity. In this study, we developed a bifunctional sheet that can simultaneously reduce the microbe and endotoxin contamination in collagen solution by co-incubation and subsequent magnetic separation, avoiding the issues of blockage and bioactivity impairment. The bifunctional sheet was successfully fabricated by modifying the magnetic graphene oxide with histamine. Collagen products treated by sheets exhibited reduced microbial and endotoxin contamination while maintaining their bioactivity for encapsulated cell growth. Additionally, inflammatory stimulation of collagen was decreased in vitro and in vivo after treatment. This work may present a facile approach for diminishing microbe and endotoxin residues in collagen products in basic research, obviating the non-essential use of a sterile workshop and facilitating the development of tissue-derived collagen research.

Graphene oxide/chitosan hydrogels for removal of antibiotics

Antibiotic contamination in aquatic environments is a growing concern, posing risks to public health and ecosystems. To address this issue, advanced materials like graphene oxide (GO) and chitosan-based hydrogels are being extensively explored for their ability to effectively remove antibiotics from wastewater, owing to their distinct characteristics and synergistic benefits. This review comprehensively examines the synthesis, characterization, and applications of GO/chitosan hydrogels in addressing antibiotic pollution. The synthesis methods, including solution casting, crosslinking, and in situ polymerization, are discussed for their simplicity and scalability. The hydrogels' key properties, such as porosity, surface area, and mechanical strength, are essential for their efficient adsorption capabilities. Adsorption mechanisms, including electrostatic interactions, π-π stacking, hydrogen bonding, and surface functional groups, enable these hydrogels to achieve high adsorption capacities. Notable examples include rGO@ZIF-67@CS hydrogels, which achieved higher adsorption capacities of 1685.26 mg·g-1 for tetracycline at pH 4 and 1890.32 mg·g-1 for norfloxacin at pH 5, while the sulfonated CMC/GO-GCC composite hydrogel achieved 312.28 mg·g-1 for sulfamethoxazole at 298 K. Moreover, high adsorption efficiencies of 90.42% with GO-CTS and 97.06% were achieved using AGO-CTS hydrogel for diclofenac adsorption. The review also highlights the practical applications of these hydrogels in wastewater treatment, comparing their performance with other adsorbents and addressing challenges such as scalability and regeneration. Finally, the review explores future research directions to enhance the effectiveness and sustainability of GO/chitosan hydrogels, emphasizing their potential as scalable, eco-friendly solutions for antibiotic removal from water.

Endotoxin-Retentive Filters for the Online Preparation of Ultrapure Dialysis Fluid and Non-Pyrogenic Substitution Fluid: A Critical Review and Reference Guide

Poor water treatments and concentrates to prepare dialysis fluids favor bacterial growth-producing pyrogens (e.g., endotoxins) that may cross hemodialysis, particularly high-flux, membranes. This puts hemodialysis patients at risk of acute bacteremia, pyrogenic reactions, long-term complications, loss of residual renal function, and poor nutritional status. Consequently, regulatory bodies worldwide recommend using ultrapure dialysis fluid for routine hemodialysis. Requests are also growing for the online production of sterile non-pyrogenic substitution fluid from ultrapure dialysis fluid. This way, large volumes of infusion solution may be safely and economically produced, enabling more end-stage kidney disease patients to benefit from the greater capacity of hemodiafiltration to remove toxins than purely diffusive hemodialysis treatment. Ultrapure dialysis and substitution fluids are often produced upstream from hemodialyzers by online filtration of standard dialysis fluid through cascades of bacteria- and endotoxin-retentive filters (ETRFs). Commercial ETRFs differ for membranes, operation, performance, duration and maintenance protocols, connection to a dialysis machine, disinfection procedures, and replacement schedule. Although suboptimal ETRF choice may increase treatment costs, the difficulty in gathering comparative information on commercial ETRFs complicates their selection. To aid dialysis centers in selecting the most convenient and suitable ETRF for their needs, herein, relevant characteristics of commercial ETRFs are reported and critically reviewed for a quick yet effective comparison.

The impact of LPS mutants on endotoxin masking in different detection systems

Endotoxin masking poses a potential risk to patient safety by rendering endotoxin undetectable. While research often focuses on international endotoxin standards (RSE), the effects of LPS mutants on Low Endotoxin Recovery (LER) are poorly understood. Our study investigated S. minnesota and E. coli mutants with incomplete O-antigen chains (rough LPS) using Limulus amebocyte lysate (LAL), recombinant Factor C (rFC) and the monocyte activation test (MAT). All tested methods detected the mutants, with variations in activity observed. Measurements over time in a common drug formulation (10 mM sodium citrate and 0.05 % (w/v) polysorbate 20) showed different masking kinetics for the mutants using different methods. We were able to show that LAL and rFC have comparable kinetics, whereas MAT showed improved recovery of masked endotoxin. The study showed that the mutation of LPS have an effect on masking, independent of the assay system. We propose that polysaccharide length affects masking susceptibility, with lower hydrophilic/hydrophobic ratios caused by the shortened polysaccharide chain (rough LPS) reducing masking. In addition, the stronger negative charge of the rough mutants increases cation affinity and is suggested to contribute to the stabilisation of supramolecular structures, making the rough mutants less susceptible to masking than the smooth mutants.

Changeover method for biosafety cabinets using ozone gas

This study evaluated the effectiveness of a biosafety cabinet equipped with an ozone generator, particularly during the transition periods between the production of cell products. As living cell products cannot undergo sterilization, maintaining an aseptic manufacturing environment is paramount. Raw materials, often derived from human tissues, are frequently contaminated with various resident bacteria, necessitating environmental resets after each process. The utility of this device against bacteria, including endotoxins, endospores, and fungi endemic to human tissues, could facilitate safe and reproducible production changeovers through a simplified, one-button operation. This study focused on bacteria resistant to conventional cleaning protocols, specifically targeting endospore-forming bacteria with robust resistance to disinfectants, spore-forming fungi, and included analyses of endotoxins. The effects of ozone exposure on Pseudomonas aeruginosa (an endotoxin-producing bacterium), Bacillus subtilis (an endospore-forming bacterium), and Aspergillus brasiliensis (a spore-forming fungus) were assessed. In the dedicated biosafety cabinet equipped with an ozone generator, the treatment group exposed to ozone showed a significant reduction in both colony-forming units and endotoxin levels in Pseudomonas aeruginosa at 1.0 × 104 colony-forming units (CFUs) compared to the control group. Moreover, the ozone treatment markedly decreased the colony formation of Bacillus subtilis endospores and Aspergillus brasiliensis spores. Given its effectiveness against endospores and endotoxins-among the most challenging bacterial derivatives to eliminate-the device demonstrates potential for enhanced bacterial control in Grade A biosafety cabinets within cell product manufacturing facilities. The system may substantially reduce operator stress by ensuring product safety through straightforward operational procedures and high reproducibility, although further validation is required.

Dual-functional PCN-242 (Fe2Co) MOF for sensitive bacterial endotoxin detection

Endotoxin detection is paramount for monitoring bacterial contamination in food, pharmaceuticals, and clinical diagnostics. The limulus amebocyte lysate (LAL) test, which relies on horseshoe crab blood, has long been the gold standard for endotoxin detection. However, the widespread adoption of this method is constrained by ethical concerns and the high costs associated with harvesting endangered species. Although nanozyme-based colorimetric methods present a more cost-effective and straightforward alternative, their application is limited by suboptimal selectivity and sensitivity. In this study, we report the synthesis and rigorous characterization of the bimetallic PCN-242 (Fe2Co) metal-organic framework (MOF), synthesized using 2-amino terephthalic acid and a pre-synthesized [Fe2Co(μ3-O)(CH3COO)6] cluster. Steady-state kinetic analyses revealed that PCN-242 (Fe2Co) MOF exhibits a significantly higher affinity for hydrogen peroxide (H2O2) compared to horseradish peroxidase (HRP) and other iron-based MOFs. The development of a PCN-242 (Fe2Co)-based colorimetric sensor demonstrated a low limit of detection (LOD) of 1.36 μg mL-1 for endotoxins, with excellent selectivity and reproducibility, thereby enabling effective detection of bacterial endotoxins. Recognizing the potential of the PCN-242 (Fe2Co) MOF beyond endotoxin detection, we explored its utility in glucose biosensing. Moreover, incorporating glucose oxidase (GOx) into the PCN-242 (Fe2Co) MOF framework further enhanced its peroxidase-like catalytic activity. This integration enabled sensitive glucose detection, achieving LODs of 4.24 μM for glucose and 2.2 μM for H2O2 within a linear range of 1 to 150 μM. The dual functionality of PCN-242 (Fe2Co) MOF as a peroxidase mimic and biosensor platform highlights its potential for advanced catalytic and diagnostic applications, offering a versatile and ethical alternative to conventional methods.

Extracellular production of antifungal peptides from oxidative endotoxin-free E. coli and application

Antifungal peptides (AFPs) can be used as novel preservatives, but achieving large-scale production and application remains a long-term challenge. In this study, we developed a hybrid peptide MD (metchnikowin-drosomycin fusion) secreted into Escherichia coli supernatant, demonstrating strong inhibitory activity against Aspergillus flavus and Botrytis cinerea. The fusion tag did not impact its activity. Moreover, an endotoxin-free and oxidative leaky strain was developed by knocking out the trxB, gor, and lpp genes of endotoxin-free E. coli ClearColi-BL21(DE3). This strain facilitates the proper folding of multi-disulfide bond proteins and promotes the extracellular production of recombinant bioactive AFP MD, achieving efficient production of endotoxin-free MD. In addition, temperature control replaces chemical inducers to further reduce production costs and circumvent the toxicity of inducers. This extracellularly produced MD exhibited favorable effectiveness in inhibiting fruit mold growth, and its safety was preliminarily established by gavage testing in mice, suggesting that it can be developed into a green and sustainable fruit fungicide. In conclusion, this study provides novel approaches and systematic concepts for producing extracellularly active proteins or peptides with industrial significance. KEY POINTS: • First report of extracellular production of bioactive antifungal peptide in Escherichia coli. • The hybrid antifungal peptide MD showed strong inhibitory activity against Aspergillus flavus and Botrytis cinerea, and the activity was not affected by the fusion tag. • Endotoxin-free oxidative Escherichia coli suitable for the expression of multi-disulfide bond proteins was constructed.

Chitosan-based matrix as a carrier for bacteriophages

Wound healing is a dynamic and complex process where infection prevention is essential. Chitosan, thanks to its bactericidal activity against gram-positive and gram-negative bacteria, as well as anti-inflammatory and hemostatic properties, is an excellent candidate to design dressings for difficult-to-heal wound treatment. The great advantage of this biopolymer is its capacity to be chemically modified, which allows for the production of various functional forms, depending on the needs and subsequent use. Moreover, chitosan can be an excellent polymer matrix for bacteriophage (phage) packing as a novel alternative/supportive antibacterial therapy approach. This study is focused on the preparation and characteristics of chitosan-based material in the form of a film with the addition of Pseudomonas lytic phages (KTN4, KT28, and LUZ19), which would exhibit antibacterial activity as a potential dressing that accelerates the wound healing. We investigated the method of producing a polymer based on microcrystalline chitosan (MKCh) to serve as the matrix for phage deposition. We described some important parameters such as average molar mass, swelling capacity, surface morphology, phage release profile, and antibacterial activity tested in the Pseudomonas aeruginosa bacterial model. The chitosan polysaccharide turned out to interact with phage particles immobilizing them within a material matrix. Nevertheless, with the high hydrophilicity and swelling features of the prepared material, the external solution of bacterial culture was absorbed and phages went in direct contact with bacteria causing their lysis in the polymer matrix. KEY POINTS: • A novel chitosan-based matrix with the addition of active phages was prepared • Phage interactions with the chitosan matrix were determined as electrostatic • Phages in the matrix work through direct contact with the bacterial cells.

Bactericidal effect of far ultraviolet-C irradiation at 222 nm against bacterial peritonitis

Far ultraviolet-C irradiation at 222 nm has potent bactericidal effects against severe infections such as peritonitis, with minimal cytotoxicity. Bacterial peritonitis due to bowel perforation is a serious condition with high mortality despite current treatments. This study investigated the safety and efficacy of intraperitoneal far ultraviolet-C irradiation at 222 nm. In vitro experiments optimized the fluid conditions for bacterial or protein concentrations prior to in vivo evaluation. In vivo efficacy was assessed in a rat peritonitis model induced by Escherichia coli, measuring intra-abdominal bacterial concentration, blood cytokine levels, and mortality rates. Safety was evaluated by analyzing cyclobutane pyrimidine dimers as markers of DNA damage in five abdominal organs: stomach, small intestine, colon, liver, and spleen. Statistical analyses employed parametric methods for normally distributed data and non-parametric methods for data without normality. Optimal in vitro conditions included 106 CFU/mL bacteria, 0.5 mW/cm2 irradiation, and 10-3 mg/mL protein. In the rat model, far ultraviolet-C irradiation at 222 nm significantly decreased intra-abdominal bacteria, reduced blood cytokines (interleukin-1β and interleukin-6), and elevated survival rates from 20% to 60%, compared to lavage alone. The formation of cyclobutane pyrimidine dimers was significantly lower with 222 nm irradiation than with 254 nm, suggesting reduced DNA damage. These findings indicate that far ultraviolet-C irradiation at 222 nm, when combined with lavage, represents a promising therapeutic strategy for bacterial peritonitis, providing effective bacterial reduction and a favorable safety profile. Further research is needed to verify these findings and investigate long-term safety and potential clinical applications.

Aspergillus flavipes L-methionine γ-lyase-β-cyclodextrin conjugates with improved stability, catalytic efficiency and anticancer activity

Aspergillus flavipes L-methionine γ-lyase (MGL) has been authenticated as a powerful anticancer agent towards various solid tumors, however, the catalytic efficiency and stability of this enzyme remains the main challenge for its further in vivo applications. Thus, the objective of this study was to enhance the catalytic efficiency, structural stability of A. flavipes MGL, in addition to boost their anticancer activity, via conjugation with β-cyclodextrin. The purified A. flavipes MGL was (38.1 μmol/mg/min) was conjugated with β-cyclodextrin, with immobilization yield 80%. The conjugation process of MGL with β-cyclodextrin was verified from the FTIR analysis, molecular docking analysis, ensuring the covalent conjugation process via the hydrogen, and hydrophobic interactions with the cyclodextrin hydroxyl groups and MGL surface amino acids residues. The free and CD-MGL have the same optimum reaction temperature 37 °C, reaction pH 7.5 and pH stability pH 6.5-8.0. The CD-MGL conjugates had a significant stability to proteinase K and trypsin digestion. The affinity of CD-MGL was increased by ~ 2 folds to L-methionine (KM 3.1 mM), compared to the free one (KM 7.2 mM), as well as the catalytic efficiency of MGL was increased by 1.8 folds upon cyclodextrin conjugation. The higher affinity of CD-MGL for L-methionine might be due to re-orientation of the MGL to bind with the substrate by multiple interactions hydrogen, hydrophobic and covalent bonds compared to the free one. The thermal stability of MGL was increased by ~ 2 folds for the tested treatments, upon cyclodextrin conjugation. The in vitro anticancer activity of CD-MGL was enhanced by 2 folds against the HCT-116 (IC50 value 13.9 μmol/mg/min) and MCF7 (IC50 value 9.6 μmol/mg/min), compared to the free MGL (~ 21.4 μmol/mg/min). The enzymes displayed a significant activity against the proliferation of Ehrlich ascites carcinoma in vivo, with an obvious improvement on the liver tissues, as revealed from the histopathological sections.

Rationalisation of the purification process for a phage active pharmaceutical ingredient

The resurgence of phage therapy, once abandoned in the early 20th century in part due to issues related to the purification process and stability, is spurred by the global threat of antibiotic resistance. Engineering advances have enabled more precise separation unit operations, improving overall purification efficiency. The present review discusses the physicochemical properties of impurities commonly found in a phage lysate, e.g., contaminants, phage-related impurities, and propagation-related impurities. Differences in phages and bacterial impurities properties are leveraged to elaborate a four-step phage purification process: clarification, capture and concentration, subsequent purification and polishing. Ultimately, a framework for rationalising the development of a purification process is proposed, considering three operational characteristics, i.e., scalability, transferability to various phages and duration. This guide facilitates the preselection of a sequence of unit operations, which can then be confronted with the expected impurities to validate the theoretical capacity of the process to purify the phage lysate.

In Vitro and In Vivo Biocompatibility of Bacterial Cellulose

Bacterial cellulose is a unique biomaterial produced by various species of bacteria that offers a range of potential applications in the biomedical field. To provide a cost-effective alternative to soft-tissue implants used in cavity infills, remodeling, and subdermal wound healing, in vitro cytotoxicity and in vivo biocompatibility of native bacterial cellulose were investigated. Cytotoxicity was assessed using a metabolic assay on Swiss 3T3 fibroblasts and INS-1832/13 rat insulinoma. Results showed no cytotoxicity, whether the cells were seeded over or under the bacterial cellulose scaffolds. Biocompatibility was performed on Sprague-Dawley rats (males and females, 8 weeks old) by implanting bacterial cellulose membranes subcutaneously for 1 or 12 weeks. The explanted scaffolds were then sliced and stained with hematoxylin and eosin for histological characterization. The first series of results revealed acute and chronic inflammation persisting over 12 weeks. Examination of the explants indicated a high number of granulocytes within the periphery of the bacterial cellulose, suggesting the presence of endotoxins within the membrane, confirmed by a Limulus amebocyte lysate test. This discovery motivated the development of non-pyrogenic bacterial cellulose scaffolds. Following this, a second series of animal experiments was done, in which materials were implanted for 1 or 2 weeks. The results revealed mild inflammation 1 week after implantation, which then diminished to minimal inflammation after 2 weeks. Altogether, this study highlights that unmodified, purified native bacterial cellulose membranes may be used as a cost-effective biomedical device provided that proper endotoxin clearance is achieved.

The complex link between the gut microbiome and obesity-associated metabolic disorders: Mechanisms and therapeutic opportunities

Microbial interactions are widespread and important processes that support the link between disease and microbial ecology. The gut microbiota is a major source of microbial stimuli that can have detrimental or beneficial effects on human health. It is also an endocrine organ that maintains energy homeostasis and host immunity. Obesity is a highly and increasingly prevalent metabolic disease and the leading cause of preventable death worldwide. An imbalance in the gut microbiome is associated with several diseases including obesity-related metabolic disorders. This review summarizes the complex association between the gut microbiome and obesity-associated metabolic diseases and validates the role and mechanisms of ecological dysregulation in the gut in obesity-associated metabolic disorders. Therapies that could potentially alleviate obesity-associated metabolic diseases by modulating the gut microbiota are discussed.

Development of a novel bacterial production system for recombinant bioactive proteins completely free from endotoxin contamination

Endotoxins, or lipopolysaccharides (LPS), are potent immunostimulatory molecules of critical concern in bacterial recombinant protein expression systems. The gram-negative bacterium Acinetobacter baumannii exhibits an interesting and unique phenotype characterized by the complete loss of LPS. In this study, we developed a novel system for producing recombinant proteins completely devoid of endotoxin contamination using LPS-deficient A. baumannii. We purified endotoxin-free functional green fluorescent protein, which reduced endotoxin contamination by approximately three orders of magnitude, and also purified the functional cytokine tumor necrosis factor (TNF)-α. Additionally, utilization of the Omp38 signal peptide of A. baumannii enabled the extracellular production of variable domain of heavy chain of heavy chain (VHH) antibodies. With these advantages, mNb6-tri-20aa, a multivalent VHH that specifically binds to the spike protein of severe acute respiratory syndrome coronavirus 2, was purified from the culture supernatant, and endotoxin contamination was reduced by a factor of approximately 2 × 105 compared with that in conventional expression systems. A virus neutralization assay demonstrated the functionality of the purified antibody in suppressing viral infections. Moreover, we applied our system to produce ozoralizumab, a multispecific VHH that binds to human TNF-α and albumin and are marketed as a rheumatoid arthritis drug. We successfully purified a functional antibody from endotoxin contamination. This system establishes a new, completely endotoxin-free platform for the expression of recombinant proteins, which distinguishes it from other bacterial expression systems, and holds promise for future applications.

Biosafety consideration of nanocellulose in biomedical applications: A review

Nanocellulose-based biomaterials have gained significant attention in various fields, especially in medical and pharmaceutical areas, due to their unique properties, including non-toxicity, high specific surface area, biodegradability, biocompatibility, and abundant feasible and sophisticated strategies for functional modification. The biosafety of nanocellulose itself is a prerequisite to ensure the safe and effective application of biomaterials as they interact with living cells, tissues, and organs at the nanoscale. Potential residual endogenous impurities and exogenous contaminants could lead to the failure of the intended functionalities or even serious health complications if they are not adequately removed and assessed before use. This review summarizes the sources of impurities in nanocellulose that may pose potential hazards to their biosafety, including endogenous impurities that co-exist in the cellulosic raw materials themselves and exogenous contaminants caused by external exposure. Strategies to reduce or completely remove these impurities are outlined and classified as chemical, physical, biological, and combined methods. Additionally, key points that require careful consideration in the interpretation of the biosafety evaluation outcomes were discussed to ensure the safety and effectiveness of the nanocellulose-based biomaterials in medical applications.

Episomal Vectors for Stable Production of Recombinant Proteins and Engineered Antibodies

There is tremendous interest in the production of recombinant proteins, particularly bispecific antibodies and antibody-drug conjugates for research and therapeutic use. Here, we demonstrate a highly versatile plasmid system that allows the rapid generation of stable Expi293 cell pools by episomal retention of transfected DNA. By linking protein expression to puromycin resistance through an attenuated internal ribosome entry site, we achieve stable cell pools producing proteins of interest. In addition, split intein-split puromycin-mediated selection of two separate protein expression cassettes allows the stable production of bispecific antibody-like molecules or antibodies with distinct C-terminal heavy chain modifications, such as an antigen on one chain and a sortase tag on the other chain. We also use this novel expression system to generate stable Expi293 cell pools that secrete sortase A Δ59 variant Srt4M. Using these reagents, we prepared a site-specific drug-to-antibody ratio of 1 antibody-siRNA conjugate. We anticipate the simple, robust, and rapid stable protein expression systems described here being useful for a wide variety of applications.

Structural characterization and immunomodulatory activity of a water-soluble polysaccharide from Poria cocos

In order to investigate the structural characteristics and immunomodulatory effects of Poria cocos polysaccharides, a water-soluble homogeneous polysaccharide (PCP-2) was isolated by water extraction and alcohol precipitation and further purified by Cellulose DEAE-52 and Sephacryl S-100HR column chromatography. PCP-2 is a heteropolysaccharide composed of glucose, galactose, mannose, and fucose in a molar ratio of 42.0: 35.0: 13.9: 9.1. It exhibits a narrow molecular weight distribution at 2.35 kDa with a branching degree of 37.1 %. The main chain types of PCP-2 include 1,3-β-D-Glc and 1,6-β-D-Glc as the backbone glucans and 1,6-α-D-Gal as the backbone heterogalactan. In vitro experiments demonstrate that PCP-2 directly stimulate RAW264.7 cell proliferation and secretion of inflammatory factors such as NO and TNF-α. In cyclophosphamide (CTX)-induced mice, it promotes the development of thymus and spleen immune organs, elevates the blood levels of IgG, IgA, IgM and CD3+CD4+ T cells, increases the intestinal villus height/ crypt depth ratio and improves gut barrier dysfunctions. These findings suggest that PCP-2 is a natural fungal polysaccharide with broad spectrum of immunoenhancing effects, which can significantly ameliorate the immunocompromised state.

Nanobodies: a promising approach to treatment of viral diseases

Since their discovery in the 1990s, heavy chain antibodies have garnered significant interest in the scientific community. These antibodies, found in camelids such as llamas and alpacas, exhibit distinct characteristics from conventional antibodies due to the absence of a light chain in their structure. Furthermore, they possess a single antigen-binding domain known as VHH or Nanobody (Nb). With a small size of approximately 15 kDa, these Nbs demonstrate improved characteristics compared to conventional antibodies, including greater physicochemical stability and enhanced biodistribution, enabling them to bind inaccessible epitopes more effectively. As a result, Nbs have found numerous applications in various medical and veterinary fields, particularly in diagnostics and therapeutics. Advances in biotechnology have made the production of recombinant antibodies feasible and compatible with large-scale manufacturing. Through the construction of immune phage libraries that display VHHs and subsequent selection through biopanning, it has become possible to isolate specific Nbs targeting pharmaceutical targets of interest, such as viruses. This review describes the processes involved in nanobody production, from hyperimmunization to purification, with the aim of their application in the pharmaceutical industry.

Advances in endotoxin analysis

The outer membrane of gram-negative bacteria is primarily composed of lipopolysaccharide (LPS). In addition to protection, LPS defines the distinct serogroups used to identify bacteria specifically. Furthermore, LPS also act as highly potent stimulators of innate immune cells, a phenomenon essential to understanding pathogen invasion in the body. The complex multi-step process of LPS binding to cells involves several binding partners, including LPS binding protein (LBP), CD14 in both membrane-bound and soluble forms, membrane protein MD-2, and toll-like receptor 4 (TLR4). Once these pathways are activated, pro-inflammatory cytokines are eventually expressed. These binding events are also affected by the presence of monomeric or aggregated LPS. Traditional techniques to detect LPS include the rabbit pyrogen test, the monocyte activation test and Limulus-based tests. Modern approaches are based on protein, antibodies or aptamer binding. Recently, novel techniques including electrochemical methods, HPLC, quartz crystal microbalance (QCM), and molecular imprinting have been developed. These approaches often use nanomaterials such as gold nanoparticles, quantum dots, nanotubes, and magnetic nanoparticles. This chapter reviews current developments in endotoxin detection with a focus on modern novel techniques that use various sensing components, ranging from natural biomolecules to synthetic materials. Highly integrated and miniaturized commercial endotoxin detection devices offer a variety of options as the scientific and technologic revolution proceeds.

EPISOMAL VECTORS FOR STABLE PRODUCTION OF RECOMBINANT PROTEINS AND ENGINEERED ANTIBODIES

There is tremendous interest in the production of recombinant proteins, particularly bispecific antibodies and antibody-drug conjugates for research and therapeutic use. Here, we demonstrate a highly versatile plasmid system that allows rapid generation of stable Expi293 cell pools by episomal retention of transfected DNA. By linking protein expression to puromycin resistance though an attenuated internal ribosome entry site, we achieve stable cell pools producing proteins of interest. In addition, split intein-split puromycin-mediated selection of two separate protein expression cassettes allows the stable production of bispecific antibody-like molecules or antibodies with distinct C-terminal heavy chain modifications, such as an antigen on one chain and a sortase tag on the other chain. We also use this novel expression system to generate stable Expi293 cell pools that secrete sortase A Δ59 variant Srt4M. Using these reagents, we prepared a site-specific drug-to-antibody ratio of 1 antibody-siRNA conjugate. We anticipate the simple, robust, and rapid stable protein expression systems described here being useful for a wide variety of applications.

Preparation and application of UPLC silica microsphere stationary phase:A review

In this review, microspheres for ultra-performance liquid chromatography (UPLC) were reviewed in accordance with the literature in recent years. As people's demands for chromatography are becoming more and more sophisticated, the preparation and application of UPLC stationary phases have become the focus of researchers in this field. This new analytical separation science not only maintains the practicality and principle of high-performance liquid chromatography (HPLC), but also improves the step function of chromatographic performance. The review presents the morphology of four types of sub-2 μm silica microspheres that have been used in UPLC, including non-porous silica microspheres (NPSMs), mesoporous silica microspheres (MPSMs), hollow silica microspheres (HSMs) and core-shell silica microspheres (CSSMs). The preparation, pore control and modification methods of different microspheres are introduced in the review, and then the applications of UPLC in drug analysis and separation, environmental monitoring, and separation of macromolecular proteins was presented. Finally, a brief overview of the existing challenges in the preparation of sub-2 μm microspheres, which required further research and development, was given.

Recovering What Matters: High Protein Recovery after Endotoxin Removal from LPS-Contaminated Formulations Using Novel Anti-Lipid A Antibody Microparticle Conjugates

Endotoxins or lipopolysaccharides (LPS), found in the outer membrane of Gram-negative bacterial cell walls, can stimulate the human innate immune system, leading to life-threatening symptoms. Therefore, regulatory limits for endotoxin content apply to injectable pharmaceuticals, and excess LPS must be removed before commercialization. The majority of available endotoxin removal systems are based on the non-specific adsorption of LPS to charged and/or hydrophobic surfaces. Albeit effective to remove endotoxins, the lack of specificity can result in the unwanted loss of essential proteins from the pharmaceutical formulation. In this work, we developed microparticles conjugated to anti-Lipid A antibodies for selective endotoxin removal. Anti-Lipid A particles were characterized using flow cytometry and microscopy techniques. These particles exhibited a depletion capacity > 6 ×103 endotoxin units/mg particles from water, as determined with two independent methods (Limulus Amebocyte Lysate test and nanoparticle tracking analysis). Additionally, we compared these particles with a non-specific endotoxin removal system in a series of formulations of increasing complexity: bovine serum albumin in water < insulin in buffer < birch pollen extracts. We demonstrated that the specific anti-Lipid A particles show a higher protein recovery without compromising their endotoxin removal capacity. Consequently, we believe that the specificity layer integrated by the anti-Lipid A antibody could be advantageous to enhance product yield.

Lysozyme-Immobilized Polyethersulfone Membranes with Satisfactory Hemocompatibility and High Enzyme Activity for Endotoxin Removal

Endotoxin adsorption has received extensive attention in the field of blood purification. However, developing highly efficient endotoxin adsorbents with excellent hemocompatibility remains challenging. In this study, we propose a new approach for developing the functional polyethersulfone (PES) membrane to remove endotoxins. First, the PES polymer is grafted with polyethylene glycol methyl acrylate (PEG-MA) in a homogeneous phase system via γ irradiation, and PES-g-PEG can be directly used to prepare the membrane by the phase inversion method. Then, polydopamine (PDA) is coated as an adhesive layer onto a PES-g-PEG membrane in an alkaline aqueous solution, and lysozyme (Lyz) is covalently immobilized with PDA through the Schiff base reaction. Lysozyme acts as an affinity adsorption ligand of endotoxin through charge and hydrophobic action. Our study reveals that the PEG branched chain and the PDA coating on the PES membrane can maintain the secondary structure of lysozyme, and thus, the immobilized Lyz can maintain high activity. The adsorption capacity of endotoxins for the PES-g-PEG/PDA/Lyz membrane is 1.28 EU/mg, with an equilibrium adsorption time of 6 h. Therefore, the PES-g-PEG/PDA/Lyz membrane shows great potential application in the treatment of endotoxemia.

Alginate and Nanocellulose Dressings With Extract From Salmon Roe Reduce Inflammation and Accelerate Healing of Porcine Burn Wounds

Partial-thickness thermal burn wounds are characterized by a prolonged inflammatory response, oxidative stress, tissue damage, and secondary necrosis. An optimal dressing for burn wounds would reduce inflammation and oxidative stress while providing a moist, absorbent, and protective cover. We have developed an extract from unfertilized salmon roe containing components with potential anti-inflammatory and antioxidative properties, called HTX. HTX has been combined with alginate from brown algae and nanocellulose from tunicates, and 3D printed into a solid hydrogel wound dressing called Collex. Here, Collex was tested on partial thickness burn wounds in Göttingen minipigs compared to Jelonet, and a variant of Collex without HTX. We found that dermal treatment of burn wounds with Collex resulted in accelerated healing at a majority of measured points over 23 days, compared to treatment with Jelonet. In comparison to Collex without HTX, Collex enhanced healing in the first week after trauma where wound progression was pronounced. Notably, Collex reduced the inflammatory response in the early post-injury phase. The anti-inflammatory response of Collex was investigated in more detail on activated M1 macrophages. We found that Collex, as well as HTX alone, significantly reduced the secretion of pro-inflammatory interleukin-1β as well as intracellular levels of oxidative stress. The results from this study indicate that Collex is a potent dressing for the treatment of burn wounds, with the anti-inflammatory effect of HTX beneficial in the initial phase, and the moist qualities of the hydrogel favorable both in the initial and the proceeding proliferative phase of wound healing.

Green biomanufacturing in recombinant collagen biosynthesis: trends and selection in various expression systems

Collagen, classically derived from animal tissue, is an all-important protein material widely used in biomedical materials, cosmetics, fodder, food, etc. The production of recombinant collagen through different biological expression systems using bioengineering techniques has attracted significant interest in consideration of increasing market demand and the process complexity of extraction. Green biomanufacturing of recombinant collagen has become one of the focus topics. While the bioproduction of recombinant collagens (type I, II, III, etc.) has been commercialized in recent years, the biosynthesis of recombinant collagen is extremely challenging due to protein immunogenicity, yield, degradation, and other issues. The rapid development of synthetic biology allows us to perform a heterologous expression of proteins in diverse expression systems, thus optimizing the production and bioactivities of recombinant collagen. This review describes the research progress in the bioproduction of recombinant collagen over the past two decades, focusing on different expression systems (prokaryotic organisms, yeasts, plants, insects, mammalian and human cells, etc.). We also discuss the challenges and future trends in developing market-competitive recombinant collagens.

Application of a novel chemical assay for the quantification of endotoxins in bacterial bioreactor samples

A novel chemical assay, the so-called Kdo-DMB-liquid chromatography (LC) assay, was used for the accurate and cost-effective determination of the endotoxin content in supernatants of Gram-negative bacteria bioreactor samples. During mild acid hydrolysis, the endotoxin-specific sugar acid 3-deoxy-D-manno-oct-2-ulsonic acid (Kdo) is quantitatively released. Kdo is reacted with 1,2-diamino-4,5-methylenedioxybenzene (DMB) to obtain the highly fluorescent derivate Kdo-DMB. It is separated from the reaction mixture by reversed phase-(U)HPLC and detected by fluorescence. From the Kdo content the endotoxin content of the sample is calculated. For three batch cultivations of Escherichia coli K12 and a fed-batch cultivation of Pseudomonas putida KT2440, the evolution of the endotoxin content in dependence on the cultivation time was monitored. Under optimal, constant cultivation conditions a linear correlation between the endotoxin content and the easy-to-access bioreactor parameters optical density at 600 nm and dry cell weight was found for both endotoxin kinds. Under stress cultivation conditions the E. coli K12 cultivation showed a stronger increase of the endotoxin content at harvest in comparison to optimal conditions. Optical density and dry cell weight may be used for production reactors as an economic real-time estimation tool to determine the endotoxin content at different cultivation time points and conditions. The optical density can further be used to establish straightforward sample dilution schemes for endotoxin quantification in samples of unknown endotoxin content. The endotoxin content [ng mL-1] measured by the Kdo-DMB-LC assay and the endotoxin activity [EU mL-1] obtained by the compendial Limulus Amoebocyte Lysate assay show a high correlation for the bacterial bioreactor samples tested.

A trimeric coiled-coil motif binds bacterial lipopolysaccharides with picomolar affinity

α-helical coiled-coils are ubiquitous protein structures in all living organisms. For decades, modified coiled-coils sequences have been used in biotechnology, vaccine development, and biochemical research to induce protein oligomerization, and form self-assembled protein scaffolds. A prominent model for the versatility of coiled-coil sequences is a peptide derived from the yeast transcription factor, GCN4. In this work, we show that its trimeric variant, GCN4-pII, binds bacterial lipopolysaccharides (LPS) from different bacterial species with picomolar affinity. LPS molecules are highly immunogenic, toxic glycolipids that comprise the outer leaflet of the outer membrane of Gram-negative bacteria. Using scattering techniques and electron microscopy, we show how GCN4-pII breaks down LPS micelles in solution. Our findings suggest that the GCN4-pII peptide and derivatives thereof could be used for novel LPS detection and removal solutions with high relevance to the production and quality control of biopharmaceuticals and other biomedical products, where even minuscule amounts of residual LPS can be lethal.

Tissue engineering of decellularized pancreas scaffolds for regenerative medicine in diabetes

Diabetes mellitus is a global disease requiring long-term treatment and monitoring. At present, pancreas or islet transplantation is the only reliable treatment for achieving stable euglycemia in Type I diabetes patients. However, the shortage of viable pancreata for transplantation limits the use of this therapy for the majority of patients. Organ decellularization and recellularization is emerging as a promising solution to overcome the shortage of viable organs for transplantation by providing a potential alternative source of donor organs. Several studies on decellularization and recellularization of rodent, porcine, and human pancreata have been performed, and show promise for generating usable decellularized pancreas scaffolds for subsequent recellularization and transplantation. In this state-of-the-art review, we provide an overview of the latest advances in pancreas decellularization, recellularization, and revascularization. We also discuss clinical considerations such as potential transplantation sites, donor source, and immune considerations. We conclude with an outlook on the remaining work that needs to be done in order to realize the goal of using this technology to create bioengineered pancreata for transplantation in diabetes patients. STATEMENT OF SIGNIFICANCE: Pancreas or islet transplantation is a means of providing insulin-independence in diabetes patients. However, due to the shortage of viable pancreata, whole-organ decellularization and recellularization is emerging as a promising solution to overcome organ shortage for transplantation. Several studies on decellularization and recellularization of rodent, porcine, and human pancreata have shown promise for generating usable decellularized pancreas scaffolds for subsequent recellularization and transplantation. In this state-of-the-art review, we highlight the latest advances in pancreas decellularization, recellularization, and revascularization. We also discuss clinical considerations such as potential transplantation sites, donor source, and immune considerations. We conclude with future work that needs to be done in order to realize clinical translation of bioengineered pancreata for transplantation in diabetes patients.

Intralaboratory Validation of a Kinetic Turbidimetric Assay Based on Limulus Amebocyte Lysate (LAL) for Assessing Endotoxin Activity in Cow Milk

Mastitis, one of the most common diseases in dairy cattle, causes severe losses in the dairy sector worldwide and affects animal welfare. The disease is characterized by an inflammatory reaction of the mammary gland and is mainly caused by bacterial infections, including both Gram-negative and Gram-positive bacteria. The release of endotoxins associated to bacterial lysis is a weighty factor in the clinical course of Gram-negative associated mastitis and should be taken into consideration when using antibiotics in the treatment of these infections. Therefore, endotoxin detection in milk samples would be of help in the management of bovine mastitis. With this aim, we have validated a kinetic turbidimetric assay based on Limulus amebocyte lysate (LAL) for the quantification of endotoxins in milk samples. The assay was adapted to this particular matrix by incorporating filtration and dilution of the milk samples in the procedure. Our results demonstrate the robustness and usefulness of the assay, which allows the identification of coliform mastitis in milk samples from affected cows and the quantification of endotoxin activity in bulk and commercial milk samples. Further studies are required to evaluate the performance of the assay in mastitis milk samples associated to Gram-negative bacteria other than Escherichia coli as well as during the clinical course of these Gram-negative mastitis or after their treatment with antibiotics.

Process Development of Recombinant Adeno-Associated Virus Production Platform Results in High Production Yield and Purity

Optimization of recombinant adeno-associated virus (rAAV) production has important clinical implications, as manufacturing is one of the major challenges for rAAV gene therapy. In this study, we optimized upstream and downstream processing of the rAAV production platform created by an earlier design-of-experiment approach. Our results showed that adding peptones (yeastolate, Trypton N1 or both) increased production yield by 2.8- to 3.4-folds. For downstream processing, a variety of wash buffers for an affinity resin, POROS™ CaptureSelect™ (PCS)-AAVX, were tested for their effects on rAAV8 purity, including NaCl, MgCl₂, arginine, Triton X-100, CHAPS, Tween 20, octyl β-d-1-thioglucopyranoside (OTG), and low pH. The results showed that the OTG wash significantly improved the rAAV purity to 97% and reduced endotoxins to an undetectable level (<0.5 EU/mL), while retaining the yield at 92.3% of the phosphate-buffered saline (PBS) wash. The OTG wash was successfully applied to purifications of rAAV1, rAAV2, and rAAV5 using PCS-AAVX, and rAAV9 using PCS-AAV9. rAAV8 purified with OTG wash showed comparable transduction efficiency in HEK 293T cells to the rAAV8 purified with PBS wash. The optimized rAAV production process yielded 5.5-6.0 × 10¹⁴ and 7.6 × 10¹⁴ vector genome per liter of HEK 293T cells for purified rAAV8- and rAAV5-EF1α-EGFP (enhanced green fluorescent protein), respectively. The platform described in this study is simple with high yields and purity, which will be beneficial to both research and clinical gene therapy.

Enhancement of anti-tumor activity in melanoma using arginine deiminase fused with 30Kc19α protein

Arginine deiminase (ADI) is a microbial-derived enzyme which catalyzes the conversion of L-arginine into L-citrulline. ADI originating from Mycoplasma has been reported to present anti-tumor activity against arginine-auxotrophic tumors, including melanoma. Melanoma cells are sensitive to arginine depletion due to reduced expression of argininosuccinate synthase 1 (ASS1), a key enzyme for arginine biosynthesis. However, clinical applications of recombinant ADI for melanoma treatment present some limitations. Since recombinant ADI is not human-derived, it shows instability, proteolytic degradation, and antigenicity in human serum. In addition, there is a problem of drug resistance issue due to the intracellular expression of once-silenced ASS1. Moreover, recombinant ADI proteins are mainly expressed as inclusion body forms in Escherichia coli and require a time-consuming refolding process to turn them back into active form. Herein, we propose fusion of recombinant ADI from Mycoplasma hominis and 30Kc19α, a cell-penetrating protein which also increases stability and soluble expression of cargo proteins, to overcome these problems. We inserted matrix metalloproteinase-2 cleavable linker between ADI and 30Kc19α to increase enzyme activity in melanoma cells. Compared to ADI, ADI-LK-30Kc19α showed enhanced solubility, stability, and cell penetration. The fusion protein demonstrated selective cytotoxicity and reduced drug resistance in melanoma cells, thus would be a promising strategy for the improved efficacy in melanoma treatment. KEY POINTS: • Fusion of ADI with 30Kc19α enhances soluble expression and productivity of recombinant ADI in E. coli • 30Kc19α protects ADI from the proteolytic degradation by shielding effect, helping ADI to remain active • Intracellular delivery of ADI by 30Kc19α overcomes ADI resistance in melanoma cells by degrading intracellularly expressed arginine.

Recombinant vaccines in 2022: a perspective from the cell factory

The last big outbreaks of Ebola fever in Africa, the thousands of avian influenza outbreaks across Europe, Asia, North America and Africa, the emergence of monkeypox virus in Europe and specially the COVID-19 pandemics have globally stressed the need for efficient, cost-effective vaccines against infectious diseases. Ideally, they should be based on transversal technologies of wide applicability. In this context, and pushed by the above-mentioned epidemiological needs, new and highly sophisticated DNA-or RNA-based vaccination strategies have been recently developed and applied at large-scale. Being very promising and effective, they still need to be assessed regarding the level of conferred long-term protection. Despite these fast-developing approaches, subunit vaccines, based on recombinant proteins obtained by conventional genetic engineering, still show a wide spectrum of interesting potentialities and an important margin for further development. In the 80's, the first vaccination attempts with recombinant vaccines consisted in single structural proteins from viral pathogens, administered as soluble plain versions. In contrast, more complex formulations of recombinant antigens with particular geometries are progressively generated and explored in an attempt to mimic the multifaceted set of stimuli offered to the immune system by replicating pathogens. The diversity of recombinant antimicrobial vaccines and vaccine prototypes is revised here considering the cell factory types, through relevant examples of prototypes under development as well as already approved products.

Highly efficient decontamination of tetracycline and pathogen by a natural product-derived Emodin/HAp photocatalyst

To address the water pollution induced by pharmaceuticals, especially antibiotics, and pathogens, natural product emodin, a traditional Chinese medicine with the characteristic large π-conjugation anthraquinone structure, was used to rationally develop a novel Emodin/HAp photocatalyst by integrating with a thermally stable and recyclable support material hydroxyapatite (HAp) through a simple preparation method. It was found that its photocatalytic activity to generate reactive oxygen species (ROS) was greatly improved due to the migration of photogenerated electrons and holes between emodin and HAp upon visible light irradiation. Thus, this Emodin/HAp photocatalyst not only quickly photodegraded tetracycline with 99.0% removal efficiency but also exhibited complete photodisinfection of pathogenic bacteria Staphylococcus aureus upon visible light irradiation. Therefore, this study offers a new route for the design and preparation of multifunctional photocatalysts using widely available natural products for environmental remediation.

Plant produced endotoxin binding recombinant proteins effectively remove endotoxins from protein samples

Lipopolysaccharides (LPS) are highly toxic compounds, even at a trace amount. When recombinant proteins are produced in E. coli, it is inevitable that LPS contaminates. However, LPS removal is still technically challenging and costly due to the high degree of solubility in a wide range of solvents. In this study, we explored the possibility of using the N-terminal region containing cysteine-rich, EGF-like, and sushi1–3 domains (CES3) of Factor C from the horseshoe crab Carcinoscorpius rotundicauda to develop a platform to remove LPS from recombinant proteins. We expressed CES3 as part of a recombinant protein, BiP:NT:CBM3:SUMO:CES3:His:HDEL, in Nicotiana benthamiana and found that purified or microcrystalline cellulose (MCC) bead-immobilised CES3 showed strong binding to LPS-containing E. coli. To produce CES3:CBM3 in an LPS-free environment, we generated Arabidopsis transgenic plants harbouring a recombinant gene, BiP:NT:SUMO:CES3:CBM3:HDEL, and found that transgenic plants mainly produce CES3:CBM3:His:HDEL, a truncated version of BiP:NT:SUMO:CES3:CBM3:HDEL via endogenous protease-mediated proteolytic processing in vivo. CES3:CBM3:HDEL purified from Arabidopsis plant extracts and immobilised onto MCC beads removed LPS contamination from protein samples. We propose that the CES3:CBM3 fusion protein produced in plants and immobilised on MCC beads can be a robust and easy platform for LPS removal from recombinant proteins.

Gelatin-methacryloyl hydrogels containing turnip mosaic virus for fabrication of nanostructured materials for tissue engineering

Current tissue engineering techniques frequently rely on hydrogels to support cell growth, as these materials strongly mimic the extracellular matrix. However, hydrogels often need ad hoc customization to generate specific tissue constructs. One popular strategy for hydrogel functionalization is to add nanoparticles to them. Here, we present a plant viral nanoparticle the turnip mosaic virus (TuMV), as a promising additive for gelatin methacryloyl (GelMA) hydrogels for the engineering of mammalian tissues. TuMV is a flexuous, elongated, tubular protein nanoparticle (700–750 nm long and 12–15 nm wide) and is incapable of infecting mammalian cells. These flexuous nanoparticles spontaneously form entangled nanomeshes in aqueous environments, and we hypothesized that this nanomesh structure could serve as a nanoscaffold for cells. Human fibroblasts loaded into GelMA-TuMV hydrogels exhibited similar metabolic activity to that of cells loaded in pristine GelMA hydrogels. However, cells cultured in GelMA-TuMV formed clusters and assumed an elongated morphology in contrast to the homogeneous and confluent cultures seen on GelMA surfaces, suggesting that the nanoscaffold material per se did not favor cell adhesion. We also covalently conjugated TuMV particles with epidermal growth factor (EGF) using a straightforward reaction scheme based on a Staudinger reaction. BJ cells cultured on the functionalized scaffolds increased their confluency by approximately 30% compared to growth with unconjugated EGF. We also provide examples of the use of GelMA-TuMV hydrogels in different biofabrication scenarios, include casting, flow-based-manufacture of filaments, and bioprinting. We envision TuMV as a versatile nanobiomaterial that can be useful for tissue engineering.

Development and validation of a novel luciferase reporter gene assay to detect pyrogen

To develop and validate a novel reporter gene assay (RGA) to detect pyrogen, HL60 cells were transfected with an NF-κB-RE plasmid containing the luciferase gene to generate stably transfected cells. Through stimulation with pyrogens, a signal was obtained that was dose-dependent with the concentration of pyrogen. Using the cells, we selected and optimized the parameters and found that the optimal conditions may be with 5 × 10⁵/ml cells that were seeded and incubated with pyrogen for 3-6 h in IMDM medium with 2% FBS. Based on the optimized parameters, a novel RGA was developed. Then, the RGA was validated and the results showed that the linearity was greater than 0.95 between the signals and the concentrations of pyrogen, the recoveries of pyrogen were all between 50% and 200%, and the precision was less than 35%. There was no difference in the sensitivity, specificity or reproducibility between RGA and BET, and the results from RGA and MAT and RPT were consistent. Furthermore, the RGA can be applied to the pyrogen detection of monoclonal antibodies. Due to its advantages including a fast detection speed, high sensitivity, convenient mode of operation and wide-pyrogen spectrum detection, RGA is promising as a supplementary method to detect pyrogen.

Preparation and characterization of polymyxin B- and histidine-coupled magnetic nanoparticles for purification of biologics from acquired endotoxin contamination

Background

Endotoxin is a major process-related impurity that can act as a strong immunostimulant leading to fever and hypotensive shock. Thus, the US FDA and international quality standards strictly direct the biologics manufacturers to control the endotoxin contamination during the purification process. In this work, a developed method for biologics purification from acquired endotoxin contamination is introduced. This is accomplished by the preparation of dextran-coated magnetic nanoparticles using a facile rapid co-precipitation method.

Results

The resulting magnetic nanoparticles (MNPs) are characterized by dynamic light scattering, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The dextran-coated magnetic nanoparticles are further coupled to either polymyxin B or histidine to provide a positively charged ligand which enhances the affinity to the negatively charged endotoxin. Both ligands-coupled MNPs are tested for purification efficiency using the chromogenic kinetic assay. The method conditions are optimized using a two-level factorial design to achieve best purification conditions of the contaminated biologics and indicated endotoxin removal percentage 85.12% and maximum adsorption capacity of 38.5 mg/g, for histidine-coupled MNPs.

Conclusions

This developed method is introduced to serve biologics manufacturers to improve their manufacturing processes through providing a simple purifying tool for biologics from acquired endotoxin contamination.

Graphical Abstract

Engineering a suite of E. coli strains for enhanced expression of bacterial polysaccharides and glycoconjugate vaccines

BACKGROUND

Glycoengineering, in the biotechnology workhorse bacterium, Escherichia coli, is a rapidly evolving field, particularly for the production of glycoconjugate vaccine candidates (bioconjugation). Efficient production of glycoconjugates requires the coordinated expression within the bacterial cell of three components: a carrier protein, a glycan antigen and a coupling enzyme, in a timely fashion. Thus, the choice of a suitable E. coli host cell is of paramount importance. Microbial chassis engineering has long been used to improve yields of chemicals and biopolymers, but its application to vaccine production is sparse.

RESULTS

In this study we have engineered a family of 11 E. coli strains by the removal and/or addition of components rationally selected for enhanced expression of Streptococcus pneumoniae capsular polysaccharides with the scope of increasing yield of pneumococcal conjugate vaccines. Importantly, all strains express a detoxified version of endotoxin, a concerning contaminant of therapeutics produced in bacterial cells. The genomic background of each strain was altered using CRISPR in an iterative fashion to generate strains without antibiotic markers or scar sequences.

CONCLUSIONS

Amongst the 11 modified strains generated in this study, E. coli Falcon, Peregrine and Sparrowhawk all showed increased production of S. pneumoniae serotype 4 capsule. Eagle (a strain without enterobacterial common antigen, containing a GalNAc epimerase and PglB expressed from the chromosome) and Sparrowhawk (a strain without enterobacterial common antigen, O-antigen ligase and chain length determinant, containing a GalNAc epimerase and chain length regulators from Streptococcus pneumoniae) respectively produced an AcrA-SP4 conjugate with 4 × and 14 × more glycan than that produced in the base strain, W3110. Beyond their application to the production of pneumococcal vaccine candidates, the bank of 11 new strains will be an invaluable resource for the glycoengineering community.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles as Biological Carriers for Drug Delivery in Cancer Therapy

Cancer is the second leading cause of death worldwide, with 10.0 million cancer deaths in 2020. Despite advances in targeted therapies, some pharmacological drawbacks associated with anticancer chemo and immunotherapeutic agents include high toxicities, low bioavailability, and drug resistance. In recent years, extracellular vesicles emerged as a new promising platform for drug delivery, with the advantage of their inherent biocompatibility and specific targeting compared to artificial nanocarriers, such as liposomes. Particularly, mesenchymal stem/stromal cells were proposed as a source of extracellular vesicles for cancer therapy because of their intrinsic properties: high in vitro self-renewal and proliferation, regenerative and immunomodulatory capacities, and secretion of extracellular vesicles that mediate most of their paracrine functions. Moreover, extracellular vesicles are static and safer in comparison with mesenchymal stem/stromal cells, which can undergo genetic/epigenetic or phenotypic changes after their administration to patients. In this review, we summarize currently reported information regarding mesenchymal stem/stromal cell-derived extracellular vesicles, their proper isolation and purification techniques - from either naive or engineered mesenchymal stem/stromal cells - for their application in cancer therapy, as well as available downstream modification methods to improve their therapeutic properties. Additionally, we discuss the challenges associated with extracellular vesicles for cancer therapy, and we review some preclinical and clinical data available in the literature.

Development and Characterization of Silver-Doped Multi-Walled Carbon Nanotube Membranes for Water Purification Applications

A unique approach was utilized to develop multi-walled carbon nanotube (MWCNT) silver (Ag) membranes. MWCNTs were impregnated with 1 wt% Ag loading, which resulted in a homogeneous dispersion of Ag in MWCNTs. MWCNTs impregnated with Ag were then uniaxially compacted at two different pressures of 80 MPa and 120 MPa to form a compact membrane. Compacted membranes were then sintered at two different temperatures of 800 °C and 900 °C to bind Ag particles with MWCNTs as Ag particles also act as a welding agent for CNTs. The powder mixture was characterized by FESEM, thermogravimetric analysis, and XRD, while the developed samples were characterized by calculating the porosity of membrane samples, contact angle, water flux and a diametral compression test. The developed membranes showed overall large water flux, while maximum porosity was found to decrease as the compaction load and sintering temperature increased. The mechanical strength of the membranes was found to increase as the compaction load increased. The hydrophilicity of the membranes remained unchanged after the addition of Ag particles. The developed membranes would be useful for removing a variety of contaminants from water.

Strategies for Heterologous Expression, Synthesis, and Purification of Animal Venom Toxins

Animal venoms are complex mixtures containing peptides and proteins known as toxins, which are responsible for the deleterious effect of envenomations. Across the animal Kingdom, toxin diversity is enormous, and the ability to understand the biochemical mechanisms governing toxicity is not only relevant for the development of better envenomation therapies, but also for exploiting toxin bioactivities for therapeutic or biotechnological purposes. Most of toxinology research has relied on obtaining the toxins from crude venoms; however, some toxins are difficult to obtain because the venomous animal is endangered, does not thrive in captivity, produces only a small amount of venom, is difficult to milk, or only produces low amounts of the toxin of interest. Heterologous expression of toxins enables the production of sufficient amounts to unlock the biotechnological potential of these bioactive proteins. Moreover, heterologous expression ensures homogeneity, avoids cross-contamination with other venom components, and circumvents the use of crude venom. Heterologous expression is also not only restricted to natural toxins, but allows for the design of toxins with special properties or can take advantage of the increasing amount of transcriptomics and genomics data, enabling the expression of dormant toxin genes. The main challenge when producing toxins is obtaining properly folded proteins with a correct disulfide pattern that ensures the activity of the toxin of interest. This review presents the strategies that can be used to express toxins in bacteria, yeast, insect cells, or mammalian cells, as well as synthetic approaches that do not involve cells, such as cell-free biosynthesis and peptide synthesis. This is accompanied by an overview of the main advantages and drawbacks of these different systems for producing toxins, as well as a discussion of the biosafety considerations that need to be made when working with highly bioactive proteins.