Membrane protein channels equipped with a cleavable linker for inducing catalysis inside nanocompartments

Precisely timed initiation of reactions and stability of the catalysts are fundamental in catalysis. We introduce here an efficient closing-opening method for nanocompartments that contain sensitive catalysts and so achieve a controlled and extended catalytic activity. We developed a chemistry-oriented approach for modifying a pore-forming membrane protein which allows for a stimuli-responsive pore opening within the membrane of polymeric nanocompartments. We synthesized a diol-containing linker that selectively binds to the pores, blocking them completely. In the presence of an external stimulus (periodate), the linker is cleaved allowing the diffusion of substrate through the pores to the nanocompartment interior where it sets off the in situ enzymatic reaction. Besides the precise initiation of catalytic activity by opening of the pores, oxidation by periodate guarantees the cleavage of the linker under mild conditions. Accordingly, this kind of responsive nanocompartment lends itself to harboring a large variety of sensitive catalysts such as proteins and enzymes

The rise of bio-inspired polymer compartments responding to pathology-related signals

Self-organized nano- and microscale polymer compartments such as polymersomes, giant unilamellar vesicles (GUVs), polyion complex vesicles (PICsomes) and layer-by-layer (LbL) capsules have increasing potential in many sensing applications. Besides modifying the physicochemical properties of the corresponding polymer building blocks, the versatility of these compartments can be markedly expanded by biomolecules that endow the nanomaterials with specific molecular and cellular functions. In this review, we focus on polymer-based compartments that preserve their structure, and highlight the key role they play in the field of medical diagnostics: first, the self-assembling abilities that result in preferred architectures are presented for a broad range of polymers. In the following, we describe different strategies for sensing disease-related signals (pH-change, reductive conditions, and presence of ions or biomolecules) by polymer compartments that exhibit stimuli-responsiveness. In particular, we distinguish between the stimulus-sensitivity contributed by the polymer itself or by additional compounds embedded in the compartments in different sensing systems. We then address necessary properties of sensing polymeric compartments, such as the enhancement of their stability and biocompatibility, or the targeting ability, that open up new perspectives for diagnostic applications

Biomimicking And Bioactive Compartments: From Nanoscale To Microscale Vesicles

Cellular model systems are essential platforms used across multiple research fields for exploring the fundaments of biology and biochemistry. By multicompartmentalization, systems can be created where nanocompartments (serving as artficial organelles) are encapsulated in microscale compartments (serving as the cellular structure). The first topic of this thesis focusses on polymersomes that are supplemented with membrane proteins and enzymes. The biomolecules endow such bioactive vesicles with specific cellular functions and enable diverse applications in nano- or pharmatechnology. In this work, we particularly introduce a new strategy for modifying the membrane proteins via chemical-oriented approach. Until now, significant progress in functionalization of polymersomes has been obtained by embedding modified proteins into the membrane for stimuli-responsive permeability. Inside the polymersomes, enzymes are encapsulated and catalyze distinct reactions with molecules diffusing through the membrane. Due to the resulting triggerable activity, such bioinspired vesicles are able to detect diverse environmental signals and show a remarkable potential for diverse applications such as biosensing and triggerable drug release. We introduce a small, periodate-sensitive designed linker blocking the passage through a protein channel (OmpF) reconstituted into the membrane of polymersomes. By combining tools of organic and bioconjugation crosslinkers, we synthetized this organic linker. OmpF was successfully modified with the linker and led to a stimuli-responsive permeability of the vesicles. In presence of periodate, the linker was cleaved and allowed substrates to diffuse inside the compartments where encapsulated laccase catalyzed the reaction to the respective radicals with a characteristic absorbance that was detected. Additionally, the labelling of OmpF with the stimuli-responsive linker is performed under mild conditions (no organic solvents, room temperature, pH 7) and therefore it has the potential to be adapted for diverse proteins that are more sensitive than OmpF. With regard to the microscale compartments, synthetic Giant Unilamellar Vesicles (GUVs) and Giant Plasma Membrane Vesicles (GPMVs) are one of the most prominent cell-like compartments. GUVs are formed by self-assembled lipids or polymers while GPMVs, are directly derived from cells. The second project presented here, focusses on GPMVs as a platform of cell-like compartments. GPMVs include most of the cellular components and thus, provide the highest similarity to real cells. GPMVs will facilitate the investigation and the understanding of different behaviors and characteristics of cellular processes. Our aim is to promote the further development of GPMVs with regard to the study of nanoparticles (NPs) under physiological conditions. We studied molecular factors that determine the successful transfer of cellularly taken-up NPs transferred into formed GPMVs. In particular, we investigated the impact of size, concentration and surface charge of NPs in correlation with three different cell lines: HepG2, HeLa, and Caco-2. We observed that polystyrene (PS) carboxylated NPs with a size of 40 nm and 100 nm were successfully and efficiently transferred to GPMVs derived from all cell lines. Then, we investigated the distribution of NPs inside formed GPMVs and established the average number of NPs/GPMVs and the percentage of all GPMVs with NPs in their cavity

How Can Giant Plasma Membrane Vesicles Serve as a Cellular Model for Controlled Transfer of Nanoparticles?

Cellular model systems are essential platforms used across multiple research fields for exploring the fundaments of biology and biochemistry. Here, we present giant plasma membrane vesicles (GPMVs) as a platform of cell-like compartments that will facilitate the study of particles within a biorelevant environment and promote their further development. We studied how cellularly taken up nanoparticles (NPs) can be transferred into formed GPMVs and which are the molecular factors that play a role in successful transfer (size, concentration, and surface charge along with 3 different cell lines: HepG2, HeLa, and Caco-2). We observed that polystyrene (PS) carboxylated NPs with a size of 40 and 100 nm were successfully and efficiently transferred to GPMVs derived from all cell lines. We then investigated the distribution of NPs inside formed GPMVs and established the average number of NPs/GPMVs and the percentage of all GPMVs with NPs in their cavity. We pave the way for GPMV usage as superior cell-like mimics in medically relevant applications

Nanosensors based on polymer vesicles and planar membranes: A short review

This review aims to summarize the advance in the field of nanosensors based on two particular materials: polymer vesicles (polymersomes) and polymer planar membranes. These two types of polymer-based structural arrangements have been shown to be efficient in the production of sensors as their features allow to adapt to different environment but also to increase the sensitivity and the selectivity of the sensing device. Polymersomes and planar polymer membranes offer a platform of choice for a wide range of chemical functionalization and characteristic structural organization which allows a convenient usage in numerous sensing applications. These materials appear as great candidates for such nanosensors considering the broad variety of polymers. They also enable the confection of robust nanosized architectures providing interesting properties for numerous applications in many domains ranging from pollution to drug monitoring. This report gives an overview of these different sensing strategies whether the nanosensors aim to detect chemicals, biological or physical signals