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Nanomotors that use polymers to gain locomotion is an upcoming concept. Here, we made use of self-immolative polymers (SIP), i. e., polymers that disintegrate in a domino-like fashion, to initiate motion in 500 nm silica particles. We selected a BSA-triggered SIP and assessed its degradation both in solution and when deposited onto the silica particles. A 1.5-fold increase of monomer was found in the solution compared to the controls, suggesting the SIP disintegration. The locomotion of the SIP-coated motors was shown to have an average velocity of up to ∼3 μm s−1 when incubated with BSA. These proof of concept findings illustrate an alternative polymer-powered motor design, which benefits from modern polymer chemistry concepts.

The immobilization of enzymes on solid supports is an important challenge in biotechnology and biomedicine. In contrast to other methods, enzyme deposition in polymer brushes offers the benefit of high protein loading that preserves enzymatic activity in part due to the hydrated 3D environment that is available within the brush structure. The authors equipped planar and colloidal silica surfaces with poly(2-(diethylamino)ethyl methacrylate)-based brushes to immobilize Thermoplasma acidophilum histidine ammonia lyase, and analyzed the amount and activity of the immobilized enzyme. The poly(2-(diethylamino)ethyl methacrylate) brushes are attached to the solid silica supports either via a "grafting-to" or a "grafting-from" method. It is found that the grafting-from method results in higher amounts of deposited polymer and, consequently, higher amounts of Thermoplasma acidophilum histidine ammonia lyase. All polymer brush-modified surfaces show preserved catalytic activity of the deposited Thermoplasma acidophilum histidine ammonia lyase. However, immobilizing the enzyme in polymer brushes using the grafting-from method resulted in twice the enzymatic activity from the grafting-to approach, illustrating a successful enzyme deposition on a solid support.

Extremophile enzymes are useful in biotechnology and biomedicine due to their abilities to withstand harsh environments. The abilities of histidine ammonia lyases from different extremophiles to preserve their catalytic activities after exposure to acid were assessed. Thermoplasma acidophilum histidine ammonia lyase was identified as an enzyme with a promising catalytic profile following acid treatment. The fusion of this enzyme with the maltose-binding protein or co-incubation with the chaperone HdeA further helped Thermoplasma acidophilum histidine ammonia lyase to withstand acid treatments down to pH 2.8. The assembly of a microreactor by encapsulation of MBP-Thermoplasma acidophilum histidine ammonia lyase into a photocrosslinked poly(vinyl alcohol) hydrogel allowed the enzyme to recover over 50% of its enzymatic activity following exposure to simulated gastric and intestinal fluids. Our results show that using engineered proteins obtained from extremophiles in combination with polymer-based encapsulation can advance the oral formulations of biologicals.

Supporting mammalian cells against reactive oxygen species such as hydrogen peroxide (H2O2) is essential. Bottom-up synthetic biology aims to integrate designed artificial units with mammalian cells. Here, we used manganese dioxide nanosheets (MnO2-NSs) as catalytically active entities that have superoxide dismutase-like and catalase-like activities. The integration of these MnO2-NSs into 7 μm reactors was able to assist SH-SY5Y neuroblastoma cells when stressed with H2O2. Complementary, Janus-shaped 800 nm reactors with one hemisphere coated with MnO2-NSs showed directed locomotion in cell media with top speeds up to 50 μm s−1 when exposed to 300 mM H2O2 as a fuel, while reactors homogeneously coated with MnO2-NSs were not able to outperform Brownian motion. These Janus-shaped reactors were able to remove H2O2 from the media, protecting cells cultured in the proximity. This effort advanced the use of bottom-up synthetic biology concepts in neuroscience.

Bottom-up synthetic biology aims to integrate artificial moieties with living cells and tissues. Here, two types of structural scaffolds for artificial organelles were compared in terms of their ability to interact with macrophage-like murine RAW 264.7 cells. The amphiphilic block copolymer poly(cholesteryl methacrylate)-block-poly(2-carboxyethyl acrylate) was used to assemble micelles and polymer-lipid hybrid vesicles together with 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipids in the latter case. In addition, the pH-sensitive fusogenic peptide GALA was conjugated to the carriers to improve their lysosomal escape ability. All assemblies had low short-term toxicity toward macrophage-like murine RAW 264.7 cells, and the cells internalized both the micelles and hybrid vesicles within 24 h. Assemblies containing DOPE lipids or GALA in their building blocks could escape the lysosomes. However, the intracellular retention of the building blocks was only a few hours in all the cases. Taken together, the provided comparison between two types of potential scaffolds for artificial organelles lays out the fundamental understanding required to advance soft material-based assemblies as intracellular nanoreactors.

Locomotion of nano/micromotors in non-aqueous environments remains a challenging task. We assembled magnetic micromotors with different surface coatings and explored their locomotion in paper chips. Poly(l-lysine) deposition resulted in positively charged micromotors. Immobilized cellulase was used to increase the micromotors' paper penetration depth while a polyethylene glycol (PEG) coating was employed to limit the interaction between the micromotors and the cellulose fibers. All micromotors were able to move in the top layers of the paper chips with velocities dependent on the magnetic forces used to induce their locomotion, their sizes and the types of employed paper chips. Maximum speeds of up to ∼25 μm s-1 were observed for PEGylated micromotors in the fibrous cellulose environment. This type of micromotors has the potential to be considered in the area of paper microfluidics to facilitate distribution, or collection of moieties for biosensing or cell culture. This journal is

© 2022 The Authors. Advanced Biology published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., The role of astrocytes in brain function has received increased attention lately due to their critical role in brain development and function under physiological and pathophysiological conditions. However, the biological evaluation of soft material nanoparticles in astrocytes remains unexplored. Here, the interaction of crosslinked hybrid vesicles (HVs) and either C8-D1A astrocytes or primary astrocytes cultured in polystyrene tissue culture or floatable paper-based chips is investigated. The amphiphilic block copolymer poly(cholesteryl methacrylate)-block-poly(2-carboxyethyl acrylate) (P1) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine lipids are used for the assembly of HVs with crosslinked membranes. The assemblies show no short-term toxicity towards the C8-D1A astrocytes and the primary astrocytes, and both cell types internalize the HVs when cultured in 2D cell culture. Further, it is demonstrated that both the C8-D1A astrocytes and the primary astrocytes could mature in paper-based chips with preserved calcium signaling and glial fibrillary acidic protein expression. Last, it is confirmed that both types of astrocytes could internalize the HVs when cultured in paper-based chips. These findings lay out a fundamental understanding of the interaction between soft material nanoparticles and astrocytes, even when primary astrocytes are cultured in paper-based chips offering a 3D environment., This project was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 818890), the Lundbeck Foundation (R346-2020-1617), and the Carlsberg Foundation (CF 20–0418). The HRM Queen Margrethe II's travel grant (C.A.M.) is acknowledged for support. T

Materials containing zwitterionic polymers are interesting candidates for diverse applications due to their versatile properties. The assembly of the amphiphilic block copolymer poly(cholesteryl methacrylate)-block-poly(2-methacryloyloxyethyl phosphorylcholine) with three different phospholipids (1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE)) into small and giant vesicles is reported focusing on their morphology, size, and membrane properties. Giant hybrid vesicles were obtained for all types of lipids, but DOPC was more suitable to assemble small hybrid vesicles without a large fraction of hybrid micelles present. Further, the permeability of the small vesicle membranes towards 5(6)-carboxyfluorescein is very similar to comparable sized liposomes. In contrast, the permeability of the giant hybrid vesicle membranes towards 5(6)-carboxy-X-rhodamine is higher compared to only cholesterol-containing lipid giant vesicles. DOPS-containing vesicles showed pH-dependent morphology changes. Hybrid vesicles containing DOPS and DOPE in addition to the block copolymer have the highest association with HepG2 cells. In contrast, only DOPC-containing hybrid vesicles can be incorporated into alginate beads. Taken together, using these block copolymer with a zwitterionic hydrophilic extension of the chosen architecture offers fundamental insight into the possibility to assemble hybrid vesicles and their potential in bottom-up synthetic biology.

Cell culture-based intestinal models are important to evaluate nanoformulations intended for oral drug delivery. We report the use of a floating structured paper chip as a scaffold for Caco-2 cells and HT29-MTX-E12 cells that are two established cell types used in intestinal cell models. The formation of cell monolayers for both mono- and cocultures in the paper chip are confirmed and the level of formed cell-cell junctions is evaluated. Further, cocultures show first mucus formation between 6-10 days with the mucus becoming more pronounced after 19 days. Hybrid vesicles (HVs) made from phospholipids and the amphiphilic block copolymer poly(cholesteryl methacrylate)-block-poly(2-carboxyethyl acrylate) in different ratios are used as a representative soft nanoparticle to assess their mucopenetration ability in paper chip-based cell cultures. The HV assembly is characterized, and it is illustrated that these HVs cross the mucus layer and are found intracellularly within 3 h when the cells are grown in the paper chips. Taken together, the moist three-dimensional cellulose environment of structured paper chips offers an interesting cell culture-based intestinal model that can be further integrated with fluidic systems or online read-out opportunities.

Nano-and micromotors are self-navigating particles that gain locomotion using fuel from the environment or external power sources to outperform Brownian motion. Herein, motors that make use of surface polymerization of hydroxyethylmethylacrylate to gain locomotion are reported, synthetically mimicking microorganisms' way of propulsion. These motors have enhanced Brownian motion with effective diffusion coefficients up to ∼0.5 μm2 s-1 when mesoporous Janus particles are used. Finally, indication of swarming is observed when high numbers of motors homogenously coated with atom-transfer radical polymerization initiators are used, while high-density Janus motors lost their ability to exhibit enhanced Brownian motion. This report illustrates an alternative route to self-propelled particles, employing a polymerization process that has the potential to be applied for various purposes benefiting from the tool box of modern polymer chemistry.

Crossing the intestinal mucus layer remains a great hurdle in oral drug delivery. The viscous mucus gel protects the body from pathogens but simultaneously traps many types of delivery vehicles, limiting their therapeutic efficacy. We report the assembly of mucopenetrating PEG-based polymer-lipid hybrid vesicles encapsulated in mucoadhesive alginate carriers aiming to increase their residence time in the intestine. The stability of the formulations was evaluated in simulated gastrointestinal conditions, showing negligible subunit leakage in the gastric fluid but a substantial release in the intestinal fluid. Mucopenetration of the free and encapsulated subunits was first demonstrated in vitro in a microfluidic set-up filled with reconstituted porcine mucus and in a mucus-covered co-culture of Caco-2 cells and HT29-MTX-E12 cells. Finally, the free and encapsulated subunits remained adhered in close proximity to the intestinal epithelium after oral administration to rats while the alginate carriers were washed away. In conclusion, the double-encapsulated system with combined mucoadhesive and mucopenetrating properties is a promising alternative drug carrier for oral delivery.

Conjugated polymers are intriguing materials that have potential practical applications in diverse interdisciplinary subjects. Among them, polydiacetylenes (PDAs) have been extensively studied due to their interesting structural, spectral, and optical features. In particular, the unique colorimetric and fluorescent transition of PDAs in response to different external stimuli makes them a novel class of sensing materials, and numerous applications of PDAs as bio- or chemosensors have been explored in the past few decades. In this review, we summarize the latest developments with regard to the applications of PDAs as a class of sensing materials presented in the literature since 2014. This review is sorted into categories based on the structural differences of diacetylene monomers, from which PDAs are generated. In addition, different forms of PDAs and various methods for improving the sensing performance of PDAs are also emphasized.

Colloidal systems with autonomous mobility are attractive alternatives to static particles for diverse applications. We present a complementary approach using pH-triggered disintegrating polymer multilayers for self-propulsion of swimmers. It is illustrated both experimentally and theoretically that homogenously coated swimmers exhibit higher velocity in comparison to their Janus-shaped counterparts. These swimmers show directional and random motion in microfluidic channels with a steep and shallow pH gradient, respectively. Further, a higher number of deposited polymer multilayers, steeper pH gradients and lower mass of the swimmers result in higher self-propulsion velocities. This new self-propulsion mechanism opens up unique opportunities to design, for instance, fast and yet biocompatible swimmers using the diverse tools of polymer chemistry to custom-synthesise the polymeric building blocks to assemble multilayers.

Artificial organelles are envisioned as nanosized assemblies with intracellular biocatalytic activity to provide the host cells with non-native or missing/lost function. Hybrid vesicles loaded with glucose oxidase (NR GOx) or β-galactosidase (NR β-Gal) and equipped with lysosomal escape ability are assembled using phospholipids and the block copolymer poly(cholesteryl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate). The co-localization of the building blocks and the catalytic activity of NR GOx and NR β-Gal are illustrated. The intracellular activity of the nanoreactors in RAW 264.7 macrophages is confirmed by an enhanced reduction in viability for cells pre-incubated with NR GOx in the presence of glucose due to the generation of cytotoxic hydrogen peroxide compared to the controls. In addition, RAW 264.7 macrophages and primary human macrophages equipped with NR β-Gal are able to intracellularly convert β-Gal-NONOate into nitric oxide. The successful use of these hybrid vesicles to equip host macrophages with additional catalytic activity diversifies the available toolbox of nanocarriers with envisioned application in cell mimicry.

The fast and effective discrimination of different liquid mixtures such as beers is a long-standing challenge in the food and beverage industry. We report the fabrication of a solution-based sensor array derived from nanoscale polydiacetylene (PDA) vesicles to distinguish different ethanol containing aqueous solutions supplemented with different model flavor compounds relevant in beers. The sensitivity of the sensors was significantly affected by the head group modification of the diacetylenes and the composition of the sensors. Finally, a selected set of sensors was utilized as a sensor array to distinguish different commercial beers in combination with statistical data analysis. This approach represents an effort toward the employment of low-cost sensors with an easy read-out for the fast discrimination of different beverages.

Biosensors for the rapid, specific, and sensitive detection of analytes play a vital role in healthcare, drug discovery, food safety, and environmental monitoring. Although a number of sensing concepts and devices have been developed, many longstanding challenges to obtain inexpensive, easy-to-use, and reliable sensor platforms remain largely unmet. Nanomaterials offer exciting possibilities for enhancing the assay sensitivity and for lowering the detection limits down to single-molecule resolution. In this review, we present an overview of liposomes and lipid bilayers in biosensing applications. Lipid assemblies in the form of spherical liposomes or two-dimensional planar membranes have been widely used in the design of biosensing assays; in particular, we highlight a number of recent promising developments of biosensors based on liposomes in suspension, liposome arrays, and lipid bilayers arrays. Assay sensitivity and specificity are discussed, advantages and drawbacks are reviewed, and possible further developments are outlined.

Excitotoxicity is a common phenomenon in several neurological diseases, associated with an impaired clearance of synaptically released glutamate, which leads to an overactivation of postsynaptic glutamate receptors. This will, in turn, start an intracellular cascade of neurotoxic events, which include exacerbated production of reactive oxygen species and ammonia toxicity. We report the assembly of microreactors equipped with platinum nanoparticles as artificial enzymes and polymer terminating layers including poly(dopamine). The biological response to these microreactors is assessed in human neuroblastoma cell culture. The microreactors’ function to deplete hydrogen peroxide (H2O2) and ammonia is confirmed. While the proliferation of the cells depends on the number of microreactors present, no inherent toxicity is found. Furthermore, the microreactors are able to ameliorate the effects of excitotoxicity in cell culture by scavenging H2O2 and ammonia, thus having the potential to provide a therapeutic appr...

Cell mimicry is a nature inspired concept that aims to substitute for missing or lost (sub)cellular function. This review focuses on the latest advancements in the use of enzymes in cell mimicry for encapsulated catalysis and artificial motility in synthetic bottom-up assemblies with emphasis on the biological response in cell culture or more rarely in animal models. Entities across the length scale from nano-sized enzyme mimics, sub-micron sized artificial organelles and self-propelled particles (swimmers) to micron-sized artificial cells are discussed. Although the field remains in its infancy, the primary aim of this review is to illustrate the advent of nature-mimicking artificial molecules and assemblies on their way to become a complementary alternative to their role models for diverse biomedical purposes.

Synthetic micromotors are evaluated extensively in a range of biomedical, microscale transport, and environmental applications. Fundamental insight into micromotors that exhibit locomotion due to triggered disintegration of their associated liposomes is provided. Directed self-propulsion is observed when the lipid vesicles are solubilized using Triton X-100 (TX) and bile at sufficiently high concentrations. Directional motion, initiated by a propagating TX or bile gradient, is found when using a sufficiently high concentration of solubilization agents. On the other hand, a low bile concentration results in short-term reverse directional motion. The experimental and theoretical considerations offer valid fundamental understanding to complement the list of explored locomotion mechanisms for micromotors.

© 2020 Wiley-VCH GmbH, Excitotoxicity is a cellular phenomenon that comprises the consequences of toxic actions of excitatory neurotransmitters, such as glutamate. This process is usually related to overproduction of reactive oxygen species (ROS) and ammonia (NH4+ ) toxicity. Platinum nanoparticle (Pt-NP)-based microreactors able to degrade hydrogen peroxide (H2 O2 ) and NH4+ , are previously described as a novel therapeutical approach against excitotoxicity, conferring protection to neuroblasts. Now, it is demonstrated that these microreactors are compatible with rat primary cortical neurons, show high levels of neuronal membrane interaction, and are able to improve cell survival and neuronal activity when neurons are exposed to H2 O2 or NH4+ . Additionally, more complex microreactors are assembled, including enzyme-loaded liposomes containing glutamate dehydrogenase and glutathione reductase, in addition to Pt-NP. The in vitro activity of these microreactors is characterized and they are compared to the Pt-NP-based microreactors in terms of biological activity, concluding that they enhance cell viability similarly or more extensively than the latter. Extracellular electrophysiological recordings demonstrate that these microreactors rescue neuronal functionality lost upon incubation with H2 O2 or NH4+ . This study provides more evidence for the potential application of these microreactors in a biomedical context with more complex cellular environments., This work was supported by Fundação para a Ciência e Tecnologia (FCT), Portugal (PTDC/BTM-SAL/32147/2017, PD/BD/114278/2016, IMM/BI/2-2020) and the Aarhus University Research Foundation, Denmark.

The intestinal mucus layer remains a challenging biological barrier to cross for nanoformulations. We report the assembly of zwitterionic micelles with 2-methacryloyloxyethyl phosphorylcholine as the zwitterionic entity in the corona-forming part of the amphiphilic block copolymers. These ca. 200 nm micelles do not have inherent cytotoxicity in Caco-2 cells for a 24 h incubation time. The time-resolved crossing of the mucus layer in Caco-2/HT29-MTX-E12 co-cultures of these spherical micelles with narrow polydispersity is shown.

Micro- and nanoswimmers are a fast emerging concept that changes how colloidal and biological systems interact. They can support drug delivery vehicles, assist in crossing biological barriers, or improve diagnostics. We report microswimmers that employ collagen, a major extracellular matrix (ECM) constituent, as fuel and that have the ability to deliver heat via incorporated magnetic nanoparticles when exposed to an alternating magnetic field (AMF). Their assembly and heating properties are outlined followed by the assessment of their calcium-triggered mobility in aqueous solution and collagen gels. It is illustrated that the swimmers in collagen gel in the presence of a steep calcium gradient exhibit fast and directed mobility. The experimental data are supported with theoretical considerations. Finally, the successful penetration of the swimmers into 3D cell spheroids is shown, and upon exposure to an AMF, the cell viability is impaired due to the locally delivered heat. This report illustrates an opportunity to employ swimmers to enhance tissue penetration for cargo delivery via controlled interaction with the ECM.

It has long been a central tenet of biomedical research that coating of nanoparticles with hydrated polymers can improve their performance in biomedical applications. However, the efficacy of the approach in vivo is still debated. In vitro model systems to test the performance of engineered nanoparticles for in vivo applications often use nonrepresentative cell lines and conditions for uptake and toxicity tests. We use our platform of monodisperse iron oxide nanoparticles densely grafted with nitrodopamide-poly(ethylene glycol) (PEG) to probe cell interactions with a set of cell types and culture conditions that are relevant for applications in which nanoparticles are injected into the bloodstream. In the past, these particles have proved to have excellent stability and negligible interaction with proteins and membranes under physiological conditions. We test the influence of flow on the uptake of nanoparticles. We also investigate the transport through endothelial barrier cell layers, as well as the effect that PEG-grafted iron oxide nanoparticles have on cell layers relevant for nanoparticles injected into the bloodstream. Our results show that the dense PEG brush and resulting lack of nonspecific protein and membrane interaction lead to negligible cell uptake, toxicity, and transport across barrier layers. These results contrast with far less well-defined polymer-coated nanoparticles that tend to aggregate and consequently strongly interact with cells, for example, by endocytosis.

Biocatalytic intracellular active nanoreactors (artificial organelles) aim to support their host cells. Here, we report the first successful micelle-based artificial organelles containing a salen–manganese complex (EUK) as catalase mimic with intracellular activity in HepG2 cells to act as reactive oxygen species (ROS) scavengers. Four different EUKs were synthesized and compared in their ability to convert hydrogen peroxide to water and oxygen as free compounds and when encapsulated into micelles assembled from the amphiphilic block copolymer poly(cholesteryl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate). An EUK candidate with an asymmetric substitution of chemical groups at the ortho and the meta position (EUK-B) was identified as lead candidate. HepG2 cells continued proliferating when preincubated with low concentrations of EUK-B-containing micelles (MB). Importantly, HepG2 cells equipped with MB showed improved viability compared to the controls when stressed with paraquat, a compound that induces ROS generation. The intracellular activity of MB was supported by lower amounts of intracellular detectable ROS. This first report on the combination of artificial enzymes and artificial organelles further extends the opportunities in therapeutic cell mimicry.

Self-propelled particles attract a great deal of attention due to the auspicious range of applications for which nanobots can be used. In a biomedical context, self-propelled swimmers hold promise to autonomously navigate to a desired location in an attempt to counteract cell/tissue defects either by releasing drugs or by performing surgical tasks. The vast majority of prior reports deal with single engine assemblies, often utilizing fuel molecules which are considered to be highly cytotoxic. Herein, we introduce two engines: (1) a motor which couples enzymes (i.e., glucose oxidase) and inorganic nanoparticles (i.e., platinum nanoparticles) to gain power and (2) a peptide-fueled trypsin motor. We demonstrate that both engines can induce enhanced diffusion properties of (Janus) particles using bioavailable and completely harmless fuel molecules. By combining both engines on the same carrier, we show self-propelled particles employing two independent engines, using two different fuels. A collaborative enhancement of the swimmer's diffusion properties upon powering-up both engines simultaneously is observed. Additionally, the incorporation of magnetic nanoparticles allows for the swimmer to move in a magnetic gradient upon applying an external magnetic field, yielding in directional motion of the double-fueled particles. These multiple-fueled biocompatible swimmers are a significant contribution to make them applicable in a biomedical context.

Crossing the intestinal mucus layer is a long-standing challenge for orally delivered nanoparticles carrying therapeutic cargo. We report the assembly of mucopenetrating cargo-loaded micelles using block copolymers consisting of either linear poly(ethylene glycol) (PEG) or bottle-brush poly(oligo(ethylene glycol)methacrylate) (PEGb) as the hydrophilic block and poly(caprolactone) (PCL) or poly(cholesteryl methacrylate) (PCMA) as the hydrophobic extension. The micelles were shown to preserve their stability and retain ∼50% of their cargo in simulated gastric fluid. The ability of micelles to diffuse through reconstituted porcine mucus was assessed in a microfluidic set-up. Finally, the delivery of Nile Red as a hydrophobic model cargo across a mucus layer produced by epithelial cells was demonstrated. These engineered mucopenetrating micelles have potential to be developed into efficient absorption enhancers, contributing a nanotechnology solution to oral drug delivery.

Cell mimicry aims to create artificial structures capable of mimicking certain functions of living cells. However, cell mimics are tremendously simpler than their natural role models. Thus, increasing their complexity is of great importance for the advancement of cell mimicry concepts and for further understanding of biological intracellular processes. Here, the successful co-encapsulation of two enzymatic pathways with up to five enzymes into compartmentalized microreactors is reported. The microreactors are assembled by combining polymer layers and enzyme-loaded liposomal subunits, which physically separate the two encapsulated enzymatic pathways. Specifically, this report confirms the activity of an encapsulated enzymatic cycle that conjugates the actions of glutamate dehydrogenase and glutathione reductase, using NADP+ /NADPH as a common co-factor, as well as an encapsulated enzymatic cascade combining β-galactosidase, glucose oxidase, and catalase. This work represents a relevant advancement in encapsulated catalysis toward the assembly of therapeutic cell mimics.

Nanoformulations are widely considered in the biomedical field for drug delivery, imaging, or detoxification purposes. Cell membrane coatings are a growing concept that aims to camouflage nanomaterials. The cell membranes are the first point of contact for cells to other biological or synthetic materials and nature has established signaling pathways in this context. In contrast to using purified membrane associated proteins, the use of purified cell membranes contains the protein of interest in a very native environment. This report provides an overview over the advances in cell membrane coated (nano)particles from the past 2–3 years. The progress in using cell membranes from mammalian cells without nuclei, i.e., red blood cells and platelets, as well as nucleus-containing cells in particular white blood cell and specific cancer cells is outlined. Additionally, highlights from recent reports considering hybrid cell membrane coating that originate from at least two different cell types are discussed. Finally, a future perspective indicating the challenges and potential of cell membrane coated nanomaterials and biomaterials is provided.

Viruses are a major threat to the wellbeing of humans, animals, and plants. The current diagnostics of viral RNA/DNA are largely dependent on polymerase chain reaction (PCR) and related concepts. Serological and immunological assays on the other hand aim to identify the presence of antibodies. Alternative approaches that consider non-biological entities as part of the sensing set-up might be a complementary path to alleviate the pressure on access to high-quality biomolecules and PCR reagents. In this context, polydiacetylenes are widely explored as biosensors because these polymers can be synthesized in situ only with the assistance of light in the desired environment. In addition, this unique group of polymers can be utilized as biosensors to detect an assortment of biomolecules and pathogens with dual optical outputs. The detection of viruses and related biomolecules with polydiacetylenes have been explored over the course of the past three decades. This progress report aims to provide a comprehensive summary of polydiacetylene-based biosensors for the detection of viruses and also related biomolecules, including nucleic acids and proteins. Given the current situation, this progress report will hopefully inspire scientists and contribute to the development of novel biosensors for the fast and effective detection of viruses.

Multicompartmentalized microreactors are considered as cell mimics with hierarchical structures inspired by mammalian cells. We report the successful assembly and encapsulation of purified nuclei from RAW 264.7 cells (pNuc) into alginate-based micro reactors. We demonstrate the preserved function of nuclei within the microreactors for mRNA production. Further, we load catalase-loaded liposomes (Lcat) into the microreactors to break down hydrogen peroxide (H2O2) into oxygen and water. Assemblies containing both natural pNuc and synthetic Lcat show significantly higher mRNA production in the presence of H2O2 compared to microreactors without Lcat or no H2O2 present, suggesting a beneficial effect of the locally enzymatically produced oxygen for transcription. This novel type of microreactors, containing both natural and synthetic compartments, presents a substantial advancement from assemblies equipped with solely synthetic units and offers opportunities as hypoxia models or for cell-free protein synthesis.

Therapeutic cell mimicry aims to provide a source of cell-like assemblies, which exhibit the core structural or functional properties of their natural counterparts with broad envisioned applications in biomedicine. Bone tissue engineering (BTE) aims at promoting and inciting the natural healing process of, for instance, critically sized bone defects Microreactors designed to co-assemble with biological bone forming osteoblasts like SaOS-2 cells to start biomineralization are reported for the first time. The alginate-based microparticles are equipped with active alkaline phosphatase-loaded artificial liposomes or SaOS-2-derived matrix vesicles (MVs). Spheroids assembled from SaOS-2 cells and microreactors not only exhibit higher cell viability, but also show enhanced biomineralization when MVs are present. The active biomineralization stimulation of the microreactors is illustrated by colorimetric calcium quantification and micro-computed tomography. These findings show the promising potential of applying cell mimicry in BTE.

The success of nanoparticulate formulations in drug delivery depends on various aspects including their toxicity, internalization, and intracellular location. Vesicular assemblies consisting of phospholipids and amphiphilic block copolymers are an emerging platform, which combines the benefits from liposomes and polymersomes while overcoming their challenges. We report the synthesis of poly(cholesteryl methacrylate)-block-poly(2-(dimethylamino) ethyl methacrylate) (pCMA-b-pDMAEMA) block copolymers and their assembly with phospholipids into hybrid vesicles. Their geometry, their ζ-potential, and their ability to adsorb onto polymer-coated surfaces were assessed. Giant unilamellar vesicles were employed to confirm the presence of both the phospholipids and the block copolymer in the same membrane. Furthermore, the cytotoxicity of selected hybrid vesicles was determined in RAW 264.7 mouse macrophages, primary rat Kupffer cells, and human macrophages. The internalization and lysosomal escape ability of the hybrid vesicles were confirmed using RAW 264.7 mouse macrophages. Taken together, our findings illustrate that the reported hybrid vesicles are a promising complementary drug delivery platform for existing liposomes and polymersomes.

Cell mimicry is an approach which aims at substituting missing or lost activity. In this context, the goal of artificial organelles is to provide intracellularly active nanoreactors to affect the cellular performance. So far, only a handful of reports discuss concepts addressing this challenge based on single-component reactors. Here, the assembly of nanoreactors equipped with glucose oxidase (GOx)-loaded liposomal subunits coated with a poly(dopamine) polymer layer and RGD targeting units is reported. When comparing different surface modifications, the uptake of the nanoreactors by endothelial cells and macrophages with applied shear stress is confirmed without inherent cytotoxicity. Furthermore, the encapsulation and preserved activity of GOx within the nanoreactors is shown. The intracellular activity is demonstrated by exposing macrophages with internalized nanoreactors to glucose and assessment of the cell viability after 6 and 24 h. The macrophage viability is found to be reduced due to the intracellularly produced hydrogen peroxide by GOx. This report on the first intracellular active subcompartmentalized nanoreactors is a considerable step in therapeutic cell mimicry.

The search for biocompatible fuels to induce autonomous motion in particles is a long-standing challenge in the field of nanorobotics. Hydrogen peroxide (H2O2) is the most utilized fuel for micro/nanomotors, although its cytotoxicity impedes its application in a biomedical context. Biocompatibility not only involves the adjustment of the motor, which should convert the energy from a stable compound into locomotion, but also requires new fabrication methods and the generation of nontoxic products resulting from fuel consumption. To address this challenge, we present the assembly and enhanced diffusion of sub-micron-sized Janus particles that feature one hemisphere decorated with the enzyme pair glucose oxidase and catalase and the use of glucose as fuel. It is found that the colloids exhibit glucose-concentration-dependent enhanced diffusion behavior, thus bringing the concept of nanomachines closer to use in biomedical applications.

Phenylketonuria (PKU) is a genetic enzyme defect affecting 1:10 000–20 000 newborn children every year. The amino acid phenylalanine (Phe) is not depleted but accumulates in tissues of several organs, which leads to severe medical conditions. A promising concept to restore the metabolism of the affected patients will be to orally administer the defective enzyme which will remove Phe in the intestine. Herein, capsosomes, a multicompartment carrier consisting of thousands of liposomes embedded within a polymeric carrier, are employed as encapsulation platform for this purpose. It is shown that the enzyme phenylalanine ammonia lyase can be entrapped within the liposomal compartments with preserved activity, demonstrated by the conversion of Phe into trans-cinnamic acid (t-ca). With the aim to mimic the dynamic environment in the intestine, the Phe conversion is performed in a microfluidic set up in the presence of human intestinal epithelial cells with applied intestinal flow and peristaltic motions. It is also shown that the microreactors are neither internalized by the cells nor exhibit inherent cytotoxicity while concurrently converting Phe into t-ca. Taken together, the first active extracellular multicompartment microreactor is reported using the relevant enzymes and settings toward the treatment of the medical condition PKU.

Surface coatings that allow externally controlled interaction with cells are of interested for diverse biomedical applications. We fabricated particle patterns and assessed the interaction of these substrates with endothelial cells and hepatocytes. The particles were turned into subcompartmentalized reactors by immobilizing glucose oxidase loaded liposomes sandwiched between polymer layers. The reactor activities depending on the number of liposome deposition steps were confirmed in solution and on patterned surfaces. Finally, reduced viability of hepatocytes adhering to the reactor patterned surfaces in the presence of glucose was observed due to the local production of hydrogen peroxide. This first report on patterned reactors in combination with cells opens up vast opportunities to assemble interactive nanobiointerfaces.

Although oral is the preferred route of administration of pharmaceutical formulations, the long-standing challenge for medically active compounds to efficiently cross the mucus layer barrier limits its wider applicability. Efforts in nanomedicine to overcome this hurdle consider mucoadhesive and mucopenetrating drug carriers by selectively designing (macromolecular) building blocks. This review highlights and critically discusses recent strategies developed in this context including poly(ethylene glycol)-based modifications, cationic and thiolated polymers, as well as particles with high charge density, zeta-potential shifting ability, or mucolytic properties. The latest advances in ex vivo test platforms are also reviewed.

Oral administration of actives is the most desired form of delivery, but the formulations need to overcome a variety of barriers including the intestinal mucus. This feature article summarizes the developments from the past 2–3 years in this context focusing on polymer-based formulations. The progress in assembling mucopenetrating nanoparticles is outlined considering coatings using noninteracting polymers as well as virus-like particles and charge-shifting particles. Next, polymers and their modification to enhance mucoadhesion are discussed, followed by providing examples of double-encapsulation systems that aim to combine mucopenetration with mucoadhesion in the same formulation. Finally, a short outlook is provided highlighting a few of the most pressing challenges to address.

Nano- and micromotors are fascinating objects that can navigate in complex fluidic environments. Their active motion can be triggered by external power sources or they can exhibit self-propulsion using fuel extracted from their surroundings. The research field is rapidly evolving and has produced nano/micromotors of different geometrical designs, exploiting a variety of mechanisms of locomotion, being capable of achieving remarkable speeds in diverse environments ranging from simple aqueous solutions to complex media including cell cultures or animal tissue. This review aims to provide an overview of the recent developments with focus on predominantly experimental demonstrations of the various motor designs developed in the past 24 months. First, externally driven motors are discussed followed by considering fuel-driven approaches. Finally, a short future perspective is provided.

Implantable devices equipped with coatings which have the ability to carry and deliver active compounds are of great interest. We report the assembly of liposome-containing poly(dopamine) films, and their interaction with adhering cells. The liposome composition is varied by adding lipophilic dopamine-conjugates and charged lipids. The cell mean fluorescence (CMF) of adhering cells due to the internalization of fluorescent cargo is found to be similar for coatings with the lipophilic-dopamine conjugates, while the charge affects the amount and location of the internalized cargo. The uptake mechanism for cargo by myoblasts using chemical inhibitors is found to be dependent on the used type of liposome. The CMF is significantly reduced for endothelial cells adhering to coatings with applied shear stress.

Liposomes, spherical vesicles consisting of one or more lipid bilayer membrane(s) encapsulating an aqueous medium, are among the prominent players in the field of nanomedicine. Herein, we highlight the newest, atypical applications of liposomes towards their use in biomedicine. In particular, we put special emphasis on innovative chemical modification of liposomes, the interactions of liposomes with cells under the influence of shear stress, and the utilisation of liposomes as drug deposits in polymeric films and as components in synthetic cell mimics.