Ultralarge suspended and perforated graphene membranes for cell culture applications.

With its high mechanical strength and its remarkable thermal and electrical properties, suspended graphene has long been expected to find revolutionary applications in optoelectronics or as a membrane in nano-devices. However, the lack of efficient transfer and patterning processes still limits its potential. In this work, we report an optimized anthracene-based transfer process to suspend few layers of graphene (1-, 2- and 4-layers) in the millimeter range (up to 3 mm) with high reproducibility. We have explored the advantages and limitations for patterning of these membranes with micrometer-resolution by focused ion beam (FIB) and picosecond pulsed laser ablation techniques. The FIB approach offers higher patterning resolution but suffers from the low throughput. We demonstrate that cold laser ablation is a fast and flexible method for micro-structuring of suspended graphene. One promising field of application of ultimately thin, microporous graphene membranes is their use as next-generation cell culture supports as alternative to track-etched polymer membranes, which often exhibit poor permeability and limited cell-to-cell communication across the membranes. To this end, we confirmed good adhesion and high viability of placental trophoblast cells cultivated on suspended porous graphene membranes without rupturing of the membranes. Overall, there is high potential for the further development of ultrathin suspended graphene membranes for many future applications, including their use for biobarrier cell culture models to enable predictive transport and toxicity assessment of drugs, environmental pollutants, and nanoparticles.

A novel inactivated virus system (InViS) for a fast and inexpensive assessment of viral disintegration.

The COVID-19 pandemic has caused considerable interest worldwide in antiviral surfaces, and there has been a dramatic increase in the research and development of innovative material systems to reduce virus transmission in the past few years. The International Organization for Standardization (ISO) norms 18,184 and 21,702 are two standard methods to characterize the antiviral properties of porous and non-porous surfaces. However, during the last years of the pandemic, a need for faster and inexpensive characterization of antiviral material was identified. Therefore, a complementary method based on an Inactivated Virus System (InViS) was developed to facilitate the early-stage development of antiviral technologies and quality surveillance of the production of antiviral materials safely and efficiently. The InViS is loaded with a self-quenched fluorescent dye that produces a measurable increase in fluorescence when the viral envelope disintegrates. In the present work, the sensitivity of InViS to viral disintegration by known antiviral agents is demonstrated and its potential to characterize novel materials and surfaces is explored. Finally, the InViS is used to determine the fate of viral particles within facemasks layers, rendering it an interesting tool to support the development of antiviral surface systems for technical and medical applications.

Novel electrospun chitosan/PEO membranes for more predictive nanoparticle transport studies at biological barriers.

The design of safe and effective nanoparticles (NPs) for commercial and medical applications requires a profound understanding of NP translocation and effects at biological barriers. To gain mechanistic insights, physiologically relevant and accurate human in vitro biobarrier models are indispensable. However, current transfer models largely rely on artificial porous polymer membranes for the cultivation of cells, which do not provide a close mimic of the natural basal membrane and intrinsically provide limited permeability for NPs. In this study, electrospinning is exploited to develop thin chitosan/polyethylene oxide (PEO) membranes with a high porosity and nanofibrous morphology for more predictive NP transfer studies. The nanofiber membranes allow the cultivation of a tight and functional placental monolayer (BeWo trophoblasts). Translocation studies with differently sized molecules and NPs (Na-fluorescein; 40 kDa FITC-Dextran; 25 nm PMMA; 70, 180 and 520 nm polystyrene NPs) across empty and cell containing membranes reveal a considerably enhanced permeability compared to commercial microporous membranes. Importantly, the transfer data of NPs is highly similar to data from ex vivo perfusion studies of intact human placental tissue. Therefore, the newly developed membranes may decisively contribute to establish physiologically relevant in vitro biobarrier transfer models with superior permeability for a wide range of molecules and particles.

Research on nanoparticles in human perfused placenta: State of the art and perspectives.

Increasing human exposure to nanoparticles (NPs) from various sources raises concerns for public health, especially for vulnerable risk groups like pregnant women and their developing fetuses. However, nanomedicine and the prospect of creating safe and effective NP-based formulations of drugs hold great promise to revolutionize treatment during pregnancy. With maternal and fetal health at stake, risks and opportunities of NPs in pregnancy need to be carefully investigated. Importantly, a comprehensive understanding of NP transport and effects at the placenta is urgently needed considering the central position of the placenta at the maternal-fetal interface and its many essential functions to enable successful pregnancy. The perfusion of human placental tissue provides a great opportunity to achieve predictive human relevant insights, circumventing uncertainties due to considerable differences in placental structure and function across species. Here, we have reviewed the current literature on the ex vivo human placenta perfusion of NPs. From 16 available studies, it was evident that placental uptake and transfer of NPs are highly dependent on their characteristics like size and surface modifications, which is in line with previous observations from in vitro and animal transport studies. These studies further revealed that special considerations apply for the perfusion of NPs and we identified relevant controls that should be implemented in future perfusion studies. While current studies mostly focused on placental transfer of NPs to conclude on potential fetal exposure, the ex vivo placental perfusion model has considerable potential to reveal novel insights on NP effects on placental tissue functionality and signaling that could indirectly affect maternal-fetal health.

Microfluidic Co-Culture Platform to Recapitulate the Maternal-Placental-Embryonic Axis.

Safety assessment of the effects of developmental toxicants on pregnant women is challenging, and systemic effects in embryo-maternal interactions are largely unknown. However, most developmental toxicity studies rely on animal trials, while in vitro platforms that recapitulate the maternal-placental-embryonic axis are missing. Here, the development of a dedicated microfluidic device for co-cultivation of a placental barrier and 3D embryoid bodies to enable systemic toxicity testing at the embryo-maternal interface is reported. The microfluidic platform features simple handling and recuperation of both tissue models, which facilitates post-hoc in-depth analysis at the tissue and single-cell level. Gravity-driven flow enables inter-tissue communication through the liquid phase as well as simple and robust operation and renders the platform parallelizable. As a proof of concept and to demonstrate platform use for systemic embryotoxicity testing in vitro, maternal exposure to plastic microparticles is emulated, and microparticle effects on the embryo-placental co-culture are investigated.

Engineering the Bioactivity of Flame-Made Ceria and Ceria/Bioglass Hybrid Nanoparticles.

Despite its use as a highly efficient and reusable catalyst in research and industrial settings, cerium oxide nanoparticles or nanoceria have yet to gain a foothold in the biomedical field. A variety of beneficial effects of nanoceria have been demonstrated, including its use as an inorganic nanoenzyme to mimic antioxidant enzymes, to protect mammalian cells, and to suppress microbial growth. While these properties are of high interest for wound-management applications, the literature offers contradicting reports on toxicity and enzymatic activity of nanoceria. These discrepancies can be attributed to differences between synthesis methods and insufficient physicochemical characterization, leading to incomparable studies. The activity of nanoceria is mostly governed by its Ce3+/Ce4+ ratio which needs to be controlled to compare different nanoceria systems. In this work, we demonstrate that liquid-feed flame spray pyrolysis offers excellent control over the oxidation state in a one-step synthesis of nanoceria. This control allows a comprehensive comparison of different types of ceria nanoparticles. We connect physicochemical characteristics to biomedically relevant properties such as superoxide dismutase and catalase mimicry, human monocyte and macrophage protection, and antimicrobial activity. Furthermore, we demonstrate how the synthesis method also allows tailoring the properties of ceria/bioglass hybrid nanoparticles, thus creating nanoparticles with manifold biomedical prospects.