Size dependent uptake and trophic transfer of polystyrene microplastics in unicellular freshwater eukaryotes

Microplastics (MP) have become a well-known and widely investigated environmental pollutant. Despite the huge amount of new studies investigating the potential threat posed by MP, the possible uptake and trophic transfer in lower trophic levels of freshwater ecosystems remains understudied. This study aims to investigate the internalization and potential trophic transfer of fluorescent polystyrene (PS) beads (0.5 μm, 3.6 × 108 particles/mL; 6 μm, 2.1 × 105 particles/mL) and fragments (<30 μm, 5 × 103 particles/mL) in three unicellular eukaryotes. This study focuses on the size-dependent uptake of MP by two freshwater Ciliophora, Tetrahymena pyriformis, Paramecium caudatum and one Amoebozoa, Amoeba proteus, serving also as predator for experiments on potential trophic transfer. Size-dependent uptake of MP in all three unicellular eukaryotes was shown. P. caudatum is able to take up MP fragments up to 27.7 μm, while T. pyriformis ingests particles up to 10 μm. In A. proteus, small MP (PS0.5μm and PS6μm) were taken up via pinocytosis and were detected in the cytoplasm for up to 14 days after exposure. Large PS-MP (PS<30μm) were detected in A. proteus only after predation on MP-fed Ciliophora. These results indicate that A. proteus ingests larger MP via predation on Ciliophora (PS<30μm), which would not be taken up otherwise. This study shows trophic transfer of MP at the base of the aquatic food web and serves as basis to study the impact of MP in freshwater ecosystems.

Influence of the polymer type of a microplastic challenge on the reaction of murine cells

Due to global pollution derived from plastic waste, the research on microplastics is of increasing public interest. Until now, most studies addressing the effect of microplastic particles on vertebrate cells have primarily utilized polystyrene particles (PS). Other studies on polymer microparticles made, e.g., of polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), or poly (ethylene terephthalate) (PET), cannot easily be directly compared to these PS studies, since the used microparticles differ widely in size and surface features. Here, effects caused by pristine microparticles of a narrow size range between 1 - 4 µm from selected conventional polymers including PS, PE, and PVC, were compared to those of particles made of polymers derived from biological sources like polylactic acid (PLA), and cellulose acetate (CA). The microparticles were used to investigate cellular uptake and assess cytotoxic effects on murine macrophages and epithelial cells. Despite differences in the particles' properties (e.g. ζ-potential and surface morphology), macrophages were able to ingest all tested particles, whereas epithelial cells ingested only the PS-based particles, which had a strong negative ζ-potential. Most importantly, none of the used model polymer particles exhibited significant short-time cytotoxicity, although the general effect of environmentally relevant microplastic particles on organisms requires further investigation.

Detection and specific chemical identification of submillimeter plastic fragments in complex matrices such as compost

Research on the plastic contamination of organic fertilizer (compost) has largely concentrated on particles and fragments > 1 mm. Small, submillimeter microplastic particles may be more hazardous to the environment. However, research on their presence in composts has been impeded by the difficulty to univocally identify small plastic particles in such complex matrices. Here a method is proposed for the analysis of particles between 0.01 and 1.0 mm according to number, size, and polymer type in compost. As a first demonstration of its potential, the method is used to determine large and small microplastic in composts from eight municipal compost producing plants: three simple biowaste composters, four plants processing greenery and cuttings and one two-stage biowaste digester-composter. While polyethylene, PE, tends to dominate among fragments > 1 mm, the microplastic fraction contained more polypropylene, PP. Whereas the contamination with PE/PP microplastic was similar over the investigated composts, only composts prepared from biowaste contained microplastic with a signature of biodegradable plastic, namely poly(butylene adipate co-terephthalate), PBAT. Moreover, in these composts PBAT microplastic tended to form the largest fraction. When the bulk of residual PBAT in the composts was analyzed by chloroform extraction, an inverse correlation between the number of particles > 0.01 mm and the total extracted amount was seen, arguing for breakdown into smaller particles, but not necessarily a mass reduction. PBAT oligomers and monomers as possible substrates for subsequent biodegradation were not found. Remaining microplastic will enter the environment with the composts, where its subsequent degradability depends on the local conditions and is to date largely uninvestigated.

Thoroughly Hydrophilized Electrospun Poly(L-Lactide)/ Poly(ε-Caprolactone) Sponges for Tissue Engineering Application

Biodegradable electrospun sponges are of interest for various applications including tissue engineering, drug release, dental therapy, plant protection, and plant fertilization. Biodegradable electrospun poly(l-lactide)/poly(ε-caprolactone) (PLLA/PCL) blend fiber-based sponge with hierarchical pore structure is inherently hydrophobic, which is disadvantageous for application in tissue engineering, fertilization, and drug delivery. Contact angles and model studies for staining with a hydrophilic dye for untreated, plasma-treated, and surfactant-treated PLLA/PCL sponges are reported. Thorough hydrophilization of PLLA/PCL sponges is found only with surfactant-treated sponges. The MTT assay on the leachates from the sponges does not indicate any cell incompatibility. Furthermore, the cell proliferation and penetration of the hydrophilized sponges are verified by in vitro cell culture studies using MG63 and human fibroblast cells.

Role of Residual Monomers in the Manifestation of (Cyto)toxicity by Polystyrene Microplastic Model Particles

Polystyrene (PS) is an important model polymer for the investigation of effects of microplastic (MP) and nanoplastic (NP) particles on living systems. Aqueous dispersions of PS MP or NP contain residual monomers of styrene. In consequence, it is not clear if the effects observed in standard (cyto)toxicity studies are evoked by the polymer (MP/NP) particle or by residual monomers. We addressed that question by comparing standard PS model particle dispersions with in-house synthesized PS particle dispersions. We proposed a rapid purification method of PS particle dispersions by dialysis against mixed solvents and developed a simple method of UV-vis spectrometry to detect residual styrene in the dispersions. We found that standard PS model particle dispersions, which contain residual monomers, exerted a low but significant cytotoxicity on mammalian cells, while the in-house synthesized PS, after rigorous purification to reduce the styrene content, did not. However, the PS particles per se but not the residual styrene in both PS particle dispersions resulted in immobilization of Daphnia. Only by using freshly monomer-depleted particles, will it be possible in the future to assess the (cyto)toxicities of PS particles, avoiding an otherwise not controllable bias effect of the monomer.

Polystyrene microparticle distribution after ingestion by murine macrophages

The impact of microplastic particles on organisms is currently intensely researched. Although it is well established that macrophages ingest polystyrene (PS) microparticles, little is known about the subsequent fate of the particles, such as entrapment in organelles, distribution during cell division, as well as possible mechanisms of excretion. Here, submicrometer (0.2 and 0.5 µm) and micron-sized (3 µm) particles were used to analyze particle fate upon ingestion of murine macrophages (J774A.1 and ImKC). Distribution and excretion of PS particles was investigated over cycles of cellular division. The distribution during cell division seems cell-specific upon comparing two different macrophage cell lines, and no apparent active excretion of microplastic particles could be observed. Using polarized cells, M1 polarized macrophages show higher phagocytic activity and particle uptake than M2 polarized ones or M0 cells. While particles with all tested diameters were found in the cytoplasm, submicron particles were additionally co-localized with the endoplasmic reticulum. Further, 0.5 µm particles were occasionally found in endosomes. Our results indicate that a possible reason for the previously described low cytotoxicity upon uptake of pristine PS microparticles by macrophages may be due to the preferential localization in the cytoplasm.

Cultivation of Encapsulated Primary Human B Lymphocytes: A First Step toward a Bioartificial Germinal Center

Polyelectrolyte microcapsules based on sodium cellulose sulfate (SCS) and poly-diallyl-dimethyl-ammonium chloride (PDADMAC) have previously been proposed as a suitable ex vivo microenvironment for the cultivation and differentiation of primary human T lymphocytes. Here, the same system is investigated for the cultivation of human primary B cells derived from adult tonsillar tissue. Proliferation and differentiation into subtypes are followed and compared to suspension cultures of B cells from the same pool performed in parallel. Total cell expansion is somewhat lower in the capsules than in the suspension cultures. More importantly, however, the differentiation of the initially mainly memory B cells into various subtypes, in particular into plasma cell (PC), shows significant differences. Clearly, the microenvironment provided by the microcapsules is beneficial for an accelerated induction of a germinal center-like B cell phenotype and afterward supports the long-term survival of the PC cells. Then, varying the encapsulation conditions (i.e., presence of human serum and dedicated cytokines in the capsule core) provides a tool for finetuning the B cell response. Hence, this methodology is suggested to pave the way toward ex vivo development of human immune organoids.

High Strength and High Toughness Electrospun Multifibrillar Yarns with Highly Aligned Hierarchy Intended as Anisotropic Extracellular Matrix

Electrospun nanofibers can be effectively used as a surrogate for extracellular matrices (ECMs). However, in the context of cellular mechanobiology, their mechanical performances can be enhanced by using nanofibrous materials with a high level of structural organization. Herein, this work develops multifibrillar yarns with superior mechanical performance based on biocompatible polyacrylonitrile (PAN) as surrogate ECM. Nearly perfect aligned nanofibers along with the axis of the multifibrillar yarn are prepared. These highly aligned yarns exhibit high strength, high toughness, good stress relaxation behavior, and are robust enough for technical or medical applications. Further, this work analyzes the influence of the highly aligned-hierarchical topological structure of the material on cell proliferation and cell orientation using cells derived from epithelial and connective tissues. Compared to nonoriented electrospun multifibrillar yarns and flat films, the well-ordered topology in the electrospun PAN multifibrillar yarns triggers an improved proliferation of fibroblasts and epithelial cells. Fibroblasts acquire an elongated morphology analogous to their behavior in the natural ECM. Hence, this heterogeneous multifibrillar material can be used to restore or reproduce the ECM for tissue engineering applications, notably in the skeletal muscle and tendon.

Optimization of soil microbial fuel cell for sustainable bio-electricity production: combined effects of electrode material, electrode spacing, and substrate feeding frequency on power generation and microbial community diversity

BACKGROUND

Microbial fuel cells (MFCs) are among the leading research topics in the field of alternative energy sources due to their multifunctional potential. However, their low bio-energy production rate and unstable performance limit their application in the real world. Therefore, optimization is needed to deploy MFCs beyond laboratory-scale experiments. In this study, we investigated the combined influence of electrode material (EM), electrode spacing (ES), and substrate feeding interval (SFI) on microbial community diversity and the electrochemical behavior of a soil MFC (S-MFC) for sustainable bio-electricity generation.

RESULTS

Two EMs (carbon felt (CF) and stainless steel/epoxy/carbon black composite (SEC)) were tested in an S-MFC under three levels of ES (2, 4, and 8 cm) and SFI (4, 6, and 8 days). After 30 days of operation, all MFCs achieved open-circuit voltage in the range of 782 + 12.2 mV regardless of the treatment. However, the maximum power of the SEC-MFC was 3.6 times higher than that of the CF-MFC under the same experimental conditions. The best solution, based on the interactive influence of the two discrete variables, was obtained with SEC at an ES of 4.31 cm and an SFI of 7.4 days during an operating period of 66 days. Analysis of the experimental treatment effects of the variables revealed the order SFI < ES < EM, indicating that EM is the most influential factor affecting the performance of S-MFC. The performance of S-MFC at a given ES value was found to be dependent on the levels of SFI with the SEC electrode, but this interactive influence was found to be insignificant with the CF electrode. The microbial bioinformatic analysis of the samples from the S-MFCs revealed that both electrodes (SEC and CF) supported the robust metabolism of electroactive microbes with similar morphological and compositional characteristics, independent of ES and SFI. The complex microbial community showed significant compositional changes at the anode and cathode over time.

CONCLUSION

This study has demonstrated that the performance of S-MFC depends mainly on the electrode materials and not on the diversity of the constituent microbial communities. The performance of S-MFCs can be improved using electrode materials with pseudocapacitive properties and a larger surface area, instead of using unmodified CF electrodes commonly used in S-MFC systems.

Tailor-Made Protein Corona Formation on Polystyrene Microparticles and its Effect on Epithelial Cell Uptake

Microplastic particles are pollutants in the environment with a potential impact on ecology and human health. As soon as microplastic particles get in contact with complex (biological) environments, they will be covered by an eco- and/or protein corona. In this contribution, protein corona formation was conducted under defined laboratory conditions on polystyrene (PS) microparticles to investigate the influence on surface properties, protein corona evolution, particle-cell interactions, and uptake in two murine epithelial cells. To direct protein corona formation, PS particles were preincubated with five model proteins, namely, bovine serum albumin (BSA), myoglobin, β-lactoglobulin, lysozyme, and fibrinogen. Subsequently, the single-protein-coated particles were incubated in a cell culture medium containing a cocktail of serum proteins to analyze changes in the protein corona profile as well as in the binding kinetics of the model proteins. Therein, we could show that the precoating step has a critical impact on the final composition of the protein corona. Yet, since proteins building the primary corona were still detectable after additional incubations in a protein-containing medium, backtracking of the particle's history is possible. Interestingly, whereas the precoating history significantly disturbs particle-cell interactions (PCIs), the cellular response (i.e., metabolic activity, MTT assay) stays unaffected. Of note, lysozyme precoating revealed one of the highest rates in PCI for both epithelial cell lines. Taken together, we could show that particle history has a significant impact on protein corona formation and subsequently on the interaction of particles with murine intestinal epithelial-like cells. However, as this study was limited to one cell type, further work is needed to assess if these observations can be generalized to other cell types.

The transcriptomic landscape of Magnetospirillum gryphiswaldense during magnetosome biomineralization

BACKGROUND

One of the most complex prokaryotic organelles are magnetosomes, which are formed by magnetotactic bacteria as sensors for navigation in the Earth's magnetic field. In the alphaproteobacterium Magnetospirillum gryphiswaldense magnetosomes consist of chains of magnetite crystals (Fe₃O₄) that under microoxic to anoxic conditions are biomineralized within membrane vesicles. To form such an intricate structure, the transcription of > 30 specific structural genes clustered within the genomic magnetosome island (MAI) has to be coordinated with the expression of an as-yet unknown number of auxiliary genes encoding several generic metabolic functions. However, their global regulation and transcriptional organization in response to anoxic conditions most favorable for magnetite biomineralization are still unclear.

RESULTS

Here, we compared transcriptional profiles of anaerobically grown magnetosome forming cells with those in which magnetosome biosynthesis has been suppressed by aerobic condition. Using whole transcriptome shotgun sequencing, we found that transcription of about 300 of the > 4300 genes was significantly enhanced during magnetosome formation. About 40 of the top upregulated genes are directly or indirectly linked to aerobic and anaerobic respiration (denitrification) or unknown functions. The mam and mms gene clusters, specifically controlling magnetosome biosynthesis, were highly transcribed, but constitutively expressed irrespective of the growth condition. By Cappable-sequencing, we show that the transcriptional complexity of both the MAI and the entire genome decreased under anaerobic conditions optimal for magnetosome formation. In addition, predominant promoter structures were highly similar to sigma factor σ⁷⁰ dependent promoters in other Alphaproteobacteria.

CONCLUSIONS

Our transcriptome-wide analysis revealed that magnetite biomineralization relies on a complex interplay between generic metabolic processes such as aerobic and anaerobic respiration, cellular redox control, and the biosynthesis of specific magnetosome structures. In addition, we provide insights into global regulatory features that have remained uncharacterized in the widely studied model organism M. gryphiswaldense, including a comprehensive dataset of newly annotated transcription start sites and genome-wide operon detection as a community resource (GEO Series accession number GSE197098).

Influence of NH3 and NH4+ on anaerobic digestion and microbial population structure at increasing total ammonia nitrogen concentrations

Despite the extensive research dedicated to ammonia inhibition, the effect of NH₃ and NH₄⁺ on each anaerobic digestion stage and the associated microorganisms is still not completely understood. In the past, the focus was mainly on methanogenesis and either on NH₃ or total ammonia nitrogen (TAN). Here, anaerobic digestion of two defined substrates, namely starch/NH₄Cl and casein, was investigated particularly regarding the effects of different NH₃/NH₄⁺ ratios on the involved microorganisms. TAN affected bacteria, primarily gram-positive ones, whereas archaea responded largely to the NH₃ concentration. These sensitivity differences are attributed to differences in the corresponding cell-membrane structures. A TAN decrease via stripping performed in two full-scale agricultural biogas plants resulted in increased bacterial diversity, with a pronounced increase in the propionate acetogens' abundance. Based on these data, it is suggested that inhibition can be avoided and processes stabilized in biogas plants by adjusting the NH₃/NH₄⁺ ratio, when feeding nitrogen-rich substrates.

Disentangling biological effects of primary nanoplastics from dispersion paints' additional compounds

Microplastic particles (MP) and nanoplastic particles (NP) as persistent anthropogenic pollutants may impact environmental and human health. A relevant potential source of primary MP and NP is water-based dispersion paint which are commonly used in any household. Given the worldwide high application volume of dispersion paint and their diverse material composition MP and NP may enter the environment with unforeseeable consequences. In order to understand the relevance of these MP and NP from paint dispersion we investigated the components of two representative wall paints and analyzed their composition in detail. The different paint components were then investigated for their impact on the model organism Daphnia magna and on a murine cell line. Plastic NP, dissolved polymers, titanium dioxide NPs, and calcium carbonate MPs demonstrated adverse effects in both biological test systems, indicating detrimental consequences of several typical components of wall paints upon release into the environment. The outcome of this study may form the basis for the evaluation of impact on other organisms, environmental transport and impact, other related technical materials and for the development of strategies for the prevention of potential detrimental effects on organisms.

Pristine and artificially-aged polystyrene microplastic particles differ in regard to cellular response

Microplastic particles (MP), arising from the gradual decomposition of plastics in the environment, have been identified as a global problem. Most investigations of MP cytotoxicity use pristine spherical particles available from commercial sources when evaluating their impact on mammalian cells, while only limited data is available for the more relevant "weathered microplastic". In this study, we exposed murine macrophages to polystyrene MP either after up to 130 days of accelerated ageing or in pristine condition. Weathered and pristine MP were physicochemically characterized, and their cytotoxicity was investigated using biological assays, transcriptome analysis, and metabolic pathways prediction. Whereas the response to pristine MP is mainly dominated by a TNF-α release, sharp-edged weathered MP induce broader adverse cellular reactions. This study stresses the importance of including more realistic test particles (e.g., weathered particles) in combination with a broad range of biological assays when evaluating the potential risk of microplastic exposure.

Supposedly identical microplastic particles substantially differ in their material properties influencing particle-cell interactions and cellular responses

Microplastics and its putative adverse effects on environmental and human health increasingly gain scientific and public attention. Systematic studies on the effects of microplastics are currently hampered by using rather poorly characterised particles, leading to contradictory results for the same particle type. Here, surface properties and chemical composition of two commercially available nominally identical polystyrene microparticles, frequently used in effect studies, were characterised. We show distinct differences in monomer content, ζ-potentials and surface charge densities. Cells exposed to particles showing a lower ζ-potential and a higher monomer content displayed a higher number of particle-cell-interactions and consequently a decrease in cell metabolism and proliferation, especially at higher particle concentrations. Our study emphasises that no general statements can be made about the effects of microplastics, not even for the same polymer type in the same size class, unless the physicochemical properties are well characterised.

In vitro cultivation of primary intestinal cells from Eisenia fetida as basis for ecotoxicological studies

The earthworm Eisenia fetida is a commonly used model organism for unspecific soil feeders in ecotoxicological studies. Its intestinal cells are the first to encounter possible pollutants co-ingested by the earthworm, which makes them prime candidates for studies of toxic effects of environmental pollutants on the cellular as compared to the organismic level. In this context, the aim of this study was to demonstrate the suitability of preparations of primary intestinal E. fetida cells for in vitro ecotoxicological studies. For this purpose, a suitable isolation and cultivation protocol was established. Cells were isolated directly from the intestine, maintaining >85% viability during subsequent cultivations (up to 144 h). Exposure to established pollutants and soil elutriates comprising silver nanoparticles and metal ions (Cu²⁺, Cd²⁺) induced a significant decrease in the metabolic activity of the cells. In case of microplastic particles (MP particles), namely 0.2, 0.5, 2.0, and 3.0 µm diameter polystyrene (PS) beads as well as 0.5 and 2.0 µm diameter polylactic acid (PLA) beads, no active uptake was observed. Slight positive as well as negative dose and size dependent effects on the metabolism were seen, which to some extent might correlate with effects on the organismic level.

Development of poly(ethyleneimine) grafted amphiphilic copolymers: Evaluation of their cytotoxicity and ability to complex DNA

Poly(ethyleneimine) (PEI) is one of the most widely used cationic polymers for gene delivery. The high molecular weight polymer, which is commercially available, is highly efficient but also very cytotoxic. The reduction in charge density by using nonlinear architectures based on low molecular weight (LMW) PEI is a promising approach to produce safer DNA-vectors. Herein, a group of cationic graft copolymers with different composition containing a hydrophobic biocompatible backbone and LMW linear PEI (lPEI) grafts obtained by ring opening polymerization and click chemistry was studied. The self-assembly and DNA complexation behavior of these materials was analyzed by the gel retardation assay, zeta potential measurements, and dynamic light scattering. The copolymers formed positively charged particles in water with average sizes between 270 and 377 nm. After they were added to DNA in serum-free medium, these particles acquired negative/near-neutral charges and increased in size depending on the N/P ratio. All copolymers showed reduced cytotoxicity compared to the 25 kDa lPEI used as reference, but the transfection efficiency was reduced. This result suggested that the cationic segments were too small to fully condense the DNA and promote cellular uptake, even with the use of several grafts and the introduction of hydrophobic domains. The trends found in this research showed that a higher degree of hydrophobicity and a higher grafting density can enhance the interaction between the copolymers and DNA. These trends could direct further structural modifications in the search for effective and safe vectors based on this polycation.

Noxic effects of polystyrene microparticles on murine macrophages and epithelial cells

Microplastic (MP) contamination has been identified as an ecological problem with an increasing impact on everyday life. Yet, possible effects of MP at the cellular level are still poorly understood. Here, the interaction of murine macrophages (J774A.1, ImKC) and epithelial cells (STC-1, BNL CL.2) with well-characterized poly(styrene) MP particles (MPP) of varying sizes (0.2-6.0 µm) was studied. Macrophages are expected to actively engulf particles which could be confirmed in this study, while epithelial cells are found in tissues with direct contact with ingested or inhaled MPP. Here, the epithelial cells from both investigated cell lines did not ingest MPP in significant numbers. Concomitantly, no cytotoxic effects nor any influence on cellular proliferation were observed. Cells from the two macrophage cell lines showed high ingestion of MPP of all sizes, but cytotoxic effects were observed only for one of them (ImKC) and only at MPP concentrations above 250 µg/mL. Indications of cellular stress as well as effects on cell proliferation were observed for cell populations with high particle cell interactions.

Generation of Recombinant Primary Human B Lymphocytes Using Non-Viral Vectors

Although the development of gene delivery systems based on non-viral vectors is advancing, it remains a challenge to deliver plasmid DNA into human blood cells. The current "gold standard", namely linear polyethyleneimine (l-PEI 25 kDa), in particular, is unable to produce transgene expression levels >5% in primary human B lymphocytes. Here, it is demonstrated that a well-defined 24-armed poly(2-dimethylamino) ethyl methacrylate (PDMAEMA, 755 kDa) nano-star is able to reproducibly elicit high transgene expression (40%) at sufficient residual viability (69%) in primary human B cells derived from tonsillar tissue. Moreover, our results indicate that the length of the mitogenic stimulation prior to transfection is an important parameter that must be established during the development of the transfection protocol. In our hands, four days of stimulation with rhCD40L post-thawing led to the best transfection results in terms of TE and cell survival. Most importantly, our data argue for an impact of the B cell subsets on the transfection outcomes, underlining that the complexity and heterogeneity of a given B cell population pre- and post-transfection is a critical parameter to consider in the multiparametric approach required for the implementation of the transfection protocol.

Towards standardized purification of bacterial magnetic nanoparticles for future in vivo applications

Bacterial magnetosomes (MS) are well-defined membrane-enveloped single-domain iron oxide (magnetite) nanoparticles, which are susceptible to genetic and chemical engineering. Additionally, the possibility to manipulate these particles by external magnetic fields facilitates their application in biomedicine and biotechnology, e.g. as magnetic resonance imaging probes or for drug delivery purposes. However, current purification protocols are poorly characterized, thereby hampering standardized and reproducible magnetosome production and thus, reliable testing for in vivo applications. In that context, the establishment of reproducible particle isolation procedures as well as the identification of high quality control parameters and the evaluation of potential cytotoxic effects of purified particles are of major importance. In this study, we characterize a multi-step purification protocol for MS with regard to purity, iron content, size and polydispersity of magnetite particles. In addition, we address potential cytotoxic effects of isolated MS when incubated with mammalian cells. Overall, we provide a detailed overview of the process-structure relationship during the isolation of MS and thus, identify prerequisites for high-yield MS production and their future application in the biomedical and biotechnological field. STATEMENT OF SIGNIFICANCE: Magnetic nanoparticles are of increasing interest for a variety of biomedical and biotechnological applications. Due to their unprecedented material characteristics, bacterial magnetosomes represent a promising alternative to chemically synthesized iron oxide nanoparticles. As applications require well-defined, highly purified and fully characterized nanoparticles, reliable protocols are necessary for efficient and reproducible magnetosome isolation. In our study, we evaluate an improved magnetosome extraction procedure and monitor quality parameters such as particle size distribution, membrane integrity and purity of the suspension by a combination of physicochemical and biochemical methods. Furthermore, the cytotoxicity of the isolated magnetosomes is assessed using different cell lines. In summary, our study helps to establish prerequisites for many real-world applications of magnetosomes in the field of biotechnology and biomedicine.

Flexible feeding in anaerobic digestion - Impact on process stability, performance and microbial community structures

Biogas has the potential to contribute to some of the most urgent issues of the energy transition, including mobility, energy storage, and grid stability. Flexibilization has been discussed as a means to improve the economics of biogas production, ideally restricting the production of electricity to times of strong need. Here the possibility of demand-driven, flexible biogas production is investigated, which saves substrates and storage capacity, while still enabling control over the production of electricity. Effects of different flexible feeding regimes were tested in a continuously operated 200 L reactor. After a period of 300 days under steady conditions (6.4 kg feed m^-3d^-1), varying flexible feeding patterns were applied over the next 700 days. Biogas production, volatile organic acid concentrations, and microbial dynamics were documented. Reduction of feeding resulted in reducing the gas production by up to 80% within a day. By increasing the feed, gas production could rapidly be reinitiated at similar levels as before even after fasting periods of up to 22 days. CH₄-contents of the produced biogas were nearly constant over the investigation period. As a response to the flexible feeding, a reorganization of the microbial community was observed, which came to an end after 800 days and then was no longer affected by further changes in the feeding patterns or the substrate composition. Dominating archaea were of the order Methanosarcinales. During the experiment, representatives from the class Methanosaetaceae replaced representatives from the class Methanosarcinaceae.

An automated oxystat fermentation regime for microoxic cultivation of Magnetospirillum gryphiswaldense

BACKGROUND

Magnetosomes produced by magnetotactic bacteria represent magnetic nanoparticles with unprecedented characteristics. However, their use in many biotechnological applications has so far been hampered by their challenging bioproduction at larger scales.

RESULTS

Here, we developed an oxystat batch fermentation regime for microoxic cultivation of Magnetospirillum gryphiswaldense in a 3 L bioreactor. An automated cascade regulation enabled highly reproducible growth over a wide range of precisely controlled oxygen concentrations (1-95% of air saturation). In addition, consumption of lactate as the carbon source and nitrate as alternative electron acceptor were monitored during cultivation. While nitrate became growth limiting during anaerobic growth, lactate was the growth limiting factor during microoxic cultivation. Analysis of microoxic magnetosome biomineralization by cellular iron content, magnetic response, transmission electron microscopy and small-angle X-ray scattering revealed magnetosomal magnetite crystals were highly uniform in size and shape.

CONCLUSION

The fermentation regime established in this study facilitates stable oxygen control during culturing of Magnetospirillum gryphiswaldense. Further scale-up seems feasible by combining the stable oxygen control with feeding strategies employed in previous studies. Results of this study will facilitate the highly reproducible laboratory-scale bioproduction of magnetosomes for a diverse range of future applications in the fields of biotechnology and biomedicine.

Transient Destabilization of Biological Membranes Contributes to the Superior Performance of Star-Shaped PDMAEMA in Delivering pDNA

Nonviral DNA vectors are promising alternatives to viral ones. Their use in DNA medicine is limited by an inability to transfect, for example, nondividing or suspension cells. In recent years, star-shaped synthetic polycationic vectors, so called "Nanostars", have shown some promise in this regard, at least when compared to the "gold standard" in nonviral vectors, namely, linear poly(ethyleneimine) (l-PEI). It has been hypothesized that an ability to transiently destabilize cellular membranes is partially responsible for the phenomenon. This hypothesis is investigated here, taking human leukemia suspension cells (Jurkat cells) as an example. Contrary to l-PEI, the Nanostars promote the cellular uptake of small, normally membrane-impermeant molecules (trypan blue and propidium iodide) as well as that of fluorescent polystyrene beads (average diameter 100 nm). Since Nanostars, but not l-PEI, are apparently able to deliver DNA to nuclei of nondividing cells, nuclear uptake is, in addition, investigated with isolated cell nuclei. Our results provide evidence that Nanostars are more efficient than l-PEI in increasing the nuclear membrane association/permeability, allowing accumulation of their cargo on/in the nucleus.

Bacterial Magnetosomes as Novel Platform for the Presentation of Immunostimulatory, Membrane-Bound Ligands in Cellular Biotechnology

Cell-cell interactions involving specific membrane proteins are critical triggers in cellular development. Ex vivo strategies to mimic these effects currently use soluble proteins or (recombinant) presenter cells, albeit with mixed results. A promising alternative are bacterial magnetosomes, which can be selectively transformed into cell-free membrane-protein presenters by genetic engineering. In this study, the human CD40 Ligand (CD40L), a key ligand for B cell activation, is expressed on the particle surface. Functionality is demonstrated on sensor cells expressing the human CD40 receptor. Binding of CD40L magnetosomes to these cells triggers a signaling cascade leading to the secretion of embryonic alkaline phosphatase. Concomitantly, the CD40-CD40L interaction is strong enough to allow cell recovery by magnetic sorting. Overall, this study demonstrates the potential of magnetosomes as promising cell-free tools for cellular biotechnology, based on the display of membrane-bound target molecules, thereby creating a biomimetic interaction.

Arsenic metabolism in technical biogas plants: possible consequences for resident microbiota and downstream units

The metal(loid) and in particular the Arsenic (As) burden of thirteen agricultural biogas plants and two sewage sludge digesters were investigated together with the corresponding microbial consortia. The latter were characterized by ARISA (automated ribosomal intergenetic spacer analysis) and next generation sequencing. The consortia were found to cluster according to digester type rather than substrate or metal(loid) composition. For selected plants, individual As species in the liquid and gaseous phases were quantified, showing that the microorganisms actively metabolize and thereby remove the As from their environment via the formation of (methylated) volatile species. The As metabolites showed some dependency on the microbial consortia, while there was no statistical correlation with the substrate mix. Finally, slurry from one agricultural biogas plant and one sewage sludge digester was transferred into laboratory scale reactors ("satellite reactors") and the response to a defined addition of As (30 and 60 µM sodium arsenite) was studied. The results corroborate the hypothesis of a rapid conversion of dissolved As species into volatile ones. Methanogenesis was reduced during that time, while there was no discernable toxic effect on the microbial population. However, the utilization of the produced biogas as replacement for natural gas, e.g. as fuel, may be problematic, as catalysts and machinery are known to suffer from prolonged exposure even to low As concentrations.

Megabenthic assemblages at the southern Central Indian Ridge - Spatial segregation of inactive hydrothermal vents from active-, periphery- and non-vent sites

Active hydrothermal vents are small-scale habitats hosting endemic fauna in a well-defined zonation around fluid effluents. The fauna of inactive hydrothermal vents and its relation to active vents and non-vent area is poorly known. Characterizing inactive areas is prerequisite to establish protected areas, especially in the context of potential seafloor massive sulfide mining, which targets inactive sites. Hierarchical clustering and Distance-based Redundancy Analysis revealed five assemblages, with significantly associated substrate types: I) active hydrothermal vent, II) periphery, III) inactive hydrothermal vent and IV) soft- and V) hard-substrate within the non-vent area. For the first time, a unique inactive faunal assemblage could be identified within the hydrothermally extinct inactive Gauss field and on adjacent hard substrates. The spatial separation from the active Edmond field and periphery and the non-vent area indicates the existence of an inactive assemblage.

Torquetenovirus viremia for early prediction of graft rejection after kidney transplantation

OBJECTIVES

New biomarkers reflecting the degree of immunosuppression in transplant recipients are needed to provide an optimal personalized balance between rejection and infection risks.

METHODS

For this purpose, we investigated TTV viremia dynamics in 66 kidney transplant recipients followed up for two years after transplantation, in relation to BK virus infection and graft rejection.

RESULTS

After transplantation, TTV viremia rose by ≥2 log₁₀ copies/mL from baseline to month 3, then declined by ≥1 log₁₀ copies/mL thereafter. Higher TTV viremia was associated with recipients of a deceased donor, a lower count of CD8+ T cells and a higher BKV viremia. Importantly, TTV loads were significantly lower in KTR who would later display graft rejection; indeed, patients with TTV viremia lower than 3.4 log₁₀ copies/mL at transplantation or lower than 4.2 log₁₀ copies/mL at month 1 had a higher risk of developing graft rejection in the two following years (hazard ratio (HR) at D0 = 7.30, p = 0.0007 and HR at M1 = 6.16, p = 0.001).

CONCLUSIONS

TTV viremia measurement at early times post transplantation predicts graft rejection and would represent a useful tool to improve kidney transplant monitoring.

Atividade in vitro do óleo essencial de Origanum vulgare L. em isolados clínicos de Aspergillus spp

RESUMO Aspergillus fumigatus, A. flavus e A. niger são os mais importantes agentes etiológicos da aspergilose, relevante micose aviária, com tratamento ineficaz e altas taxas de mortalidade. Em vista da importância da aspergilose, da necessidade de prospectar novos fármacos e do potencial terapêutico do óleo essencial de Origanum vulgare L. (OEO), o orégano, objetivou-se avaliar a sensibilidade in vitro de isolados clínicos de Aspergillus spp. em relação ao OEO. O óleo foi obtido por hidrodestilação em Clevenger, e a análise química realizada por cromatografia de massa (GC/MS). Observaram-se 15 diferentes compostos ativos, sendo 4-terpineol, hidrato de sabinene e timol os majoritários. Nos testes de microdiluição em caldo (Reference..., 2008), todos os isolados (n= 23) foram sensíveis ao OEO: A. fumigatus teve CIM entre 28,125mg/mL (0,1875%) e 450mg/mL (3,0%), A. flavus entre 112,5mg/mL (0,75%) e 450mg/mL, e A. niger 112,5mg/mL. CFM variou de 112,5mg/mL a 450mg/mL nos isolados de A. fumigatus, de 225mg/mL (1,5%) a 450mg/mL em A. flavus, e foi de 450mg/mL em A. niger. CIM e CFM foram idênticos em 6/14 isolados, o que demonstra que o óleo com a mesma concentração pode ter capacidade fungistática e fungicida. CIM 90 correspondeu à CIM máxima. Os resultados demonstram a atividade anti-Aspergillus do OEO, com CIM 90 de 450mg/mL (3%).

pH-Responsive Biohybrid Carrier Material for Phenol Decontamination in Wastewater

Smart polymers are a valuable platform to protect and control the activity of biological agents over a wide range of conditions, such as low pH, by proper encapsulation. Such conditions are present in olive oil mill wastewater with phenol as one of the most problematic constituents. We show that elastic and pH-responsive diblock copolymer fibers are a suitable carrier for Corynebacterium glutamicum, i.e., bacteria which are known for their ability to degrade phenol. Free C. glutamicum does not survive low pH conditions and fails to degrade phenol at low pH conditions. Our tea-bag like biohybrid system, where the pH-responsive diblock copolymer acts as a protecting outer shell for the embedded bacteria, allows phenol degradation even at low pH. Utilizing a two-step encapsulation process, planktonic cells were first encapsulated in poly(vinyl alcohol) to protect the bacteria against the organic solvents used in the second step employing coaxial electrospinning.

Scale-up of the ex vivo expansion of encapsulated primary human T lymphocytes

A number of evolving medical therapies call for the controlled expansion of primary human T lymphocytes. After encapsulation in sodium cellulose sulfate-poly(diallyldimethyl) ammonium chloride polyelectrolyte capsules, T lymphocytes can be expanded without persisting activation. Here, the challenge of scaling up this process is addressed. Encapsulated T lymphocytes were cultured in spinner flasks as well as in several types of the bioreactor, including fixed and fluidized beds, a waved cell bag, and a standard stirred tank reactor (STR; 1-L scale). Two proprietary T lymphocyte culture media as well as a standard RPMI-based medium were used. As before, encapsulation coincided with the presence of only a low fraction of activated T lymphocytes (peripheral blood T cells) in the total population. Unexpectedly, growth rates were lower in well-mixed reactors than those in cultivations under static conditions, that is, in T-flasks. Switching the STR to low oxygen conditions (40% air saturation) improved the growth rates to the level of the static cultures and thus forms the potential basis for efficient scale-up of T lymphocyte expansion.

Preparation of Biocomposite Microfibers Ready for Processing into Biologically Active Textile Fabrics for Bioremediation

Biocomposites, i.e., materials consisting of metabolically active microorganisms embedded in a synthetic extracellular matrix, may find applications as highly specific catalysts in bioproduction and bioremediation. 3D constructs based on fibrous biocomposites, so-called "artificial biofilms," are of particular interest in this context. The inability to produce biocomposite fibers of sufficient mechanical strength for processing into bioactive fabrics has so far hindered progress in the area. Herein a method is proposed for the direct wet spinning of microfibers suitable for weaving and knitting. Metabolically active bacteria (either Shewanella oneidensis or Nitrobacter winogradskyi (N. winogradskyi)) are embedded in these fibers, using poly(vinyl alcohol) as matrix. The produced microfibers have a partially crystalline structure and are stable in water without further treatment, such as coating. In a first application, their potential for nitrite removal (N. winogradskyi) is demonstrated, a typical challenge in potable water treatment.

Ultraporous, Compressible, Wettable Polylactide/Polycaprolactone Sponges for Tissue Engineering

Ultraporous, degradable sponges made of either polylactide or of blends of polylactide/poly(ε-caprolactone) are prepared by freeze-drying of dispersions of short electrospun fibers and subsequent thermal annealing. The sponges feature ultrahigh porosity (99.6%), a hierarchical cellular structure, and high reversible compressibility with fast recovery from deformation in the dry as well as in the wet state. The sponge properties depend on the fiber dispersion concentration and the annealing temperature. Sponge characteristics like fiber density (2.5-20 mg/cm³), size, shape, crystallinity, mechanical strength, wetability, and structural integrity are user adjustable. Cell culture experiments were successfully performed with Jurkat cells with Confocal Laser Scanning Microscopy and MTT staining showing rapid cell proliferation. Live/Dead staining demonstrated high viability of the seeded cells. The sponge characteristics and modifications investigated and presented here reveal that these sponges are highly promising for tissue engineering applications.