Heterogeneous multi-compartmental hydrogel particles as synthetic cells for incompatible tandem reactions

Self-Orienting Hydrogel Micro-Buckets as Novel Cell Carriers

Hydrogel microparticles are important in materials engineering, but their applications remain limited owing to the difficulties associated with their manipulation. Herein, we report the self‐orientation of crescent‐shaped hydrogel microparticles and elucidate its mechanism. Additionally, the microparticles were used, for the first time, as micro‐buckets to carry living cells. In aqueous solution, the microparticles spontaneously rotated to a preferred orientation with the cavity facing up. We developed a geometric model that explains the self‐orienting behavior of crescent‐shaped particles by minimizing the potential energy of this specific morphology. Finally, we selectively modified the particles’ cavities with RGD peptide and exploited their preferred orientation to load them with living cells. Cells could adhere, proliferate, and be transported and released in vitro. These micro‐buckets hold a great potential for applications in smart materials, cell therapy, and biological engineering.

Multicompartment Polymeric Nanoreactors for Non-Orthogonal Cascade Catalysis

Spatial confinement of multiple catalysts presents an effective strategy for performing sequential or tandem chemical transformations in a one-pot reaction. These methods may be used to catalyze numerous reactions in conditions that are otherwise incompatible between catalyst and solvent, different catalysts, or reagents. Appropriate site isolation or support structure design will lead to significant advantages in atom economy, purification, and costs; the development of the interface between a catalyst and its confined microenvironment is paramount for realizing the next generation of nanoreactors. Polymer scaffolds can create tailor-made microenvironments resulting in catalyst compartmentalization. Through the optimization of a number of variables such as size, solubility, functionality, and morphology of the nanoreactor, catalyst activity and selectivity can be tuned. In this feature article, design principles and early strategies for polymer supports for catalyst site-isolation are introduced, and current strategies toward multicompartment polymer nanoreactors for non-orthogonal cascade catalysis are discussed. Future design trends in this burgeoning field are outlined in the conclusion.

In Situ Cross-Linkable Hydrogels as a Dynamic Matrix for Tissue Regenerative Medicine

BACKGROUND

Polymeric hydrogels are extensively used as promising biomaterials in a broad range of biomedical applications, including tissue engineering, regenerative medicine, and drug delivery. These materials have advantages such as structural similarity to the native extracellular matrix (ECM), multi-tunable physicochemical and biological properties, and biocompatibility.

METHODS

In situ forming hydrogels show a phase transition from a solution to a gel state through various physical and chemical cross-linking reactions. These advanced hydrogel materials have been widely used for tissue regenerative medicine because of the ease of encapsulating therapeutic agents, such as cells, drugs, proteins, and genes.

RESULTS

With advances in biomaterials engineering, these hydrogel materials have been utilized as either artificial cellular microenvironments to create engineered tissue constructs or as bioactive acellular matrices to stimulate the native ECM for enhanced tissue regeneration and restoration.

CONCLUSION

In this review, we discuss the use of in situ cross-linkable hydrogels in tissue engineering and regenerative medicine applications. In particular, we focus on emerging technologies as a powerful therapeutic tool for tissue regenerative medicine applications.

Membraneless Compartmentalization Facilitates Enzymatic Cascade Reactions and Reduces Substrate Inhibition

Living cells possess membraneless organelles formed by liquid-liquid phase separation. With the aim of better understanding the general functions of membraneless microcompartments, this paper constructs acellular multicompartment reaction systems using an aqueous multiphase system. Membraneless coacervate droplets are placed within a molecularly crowded environment, where a larger dextran (DEX) droplet is submerged in a polyethylene glycol (PEG) solution. The coacervate droplets are capable of sequestering reagents and enzymes with a long retention time, and demonstrate multistep cascading reactions through the liquid-liquid interfaces. The ability to change phase dynamics is also demonstrated through salt-mediated dissolution of coacervate droplets, which leads to the release and mixing of separately sequestered reagents and enzymes. Finally, as phase-separated materials in membraneless organelles are often substrates and substrate analogues for the enzymes sequestered or excluded in the organelles, this paper explores the interaction between DEX and dextranase, an enzyme that hydrolyzes DEX. The results reveal that dextranase suffers from substrate inhibition when partitioned directly in a DEX phase but that this inhibition can be mitigated and reactions greatly accelerated by compartmentalization of dextranase inside a coacervate droplet that is adjacent to, but phase-separated from, the DEX phase. The insight that compartmentalization of enzymes can accelerate reactions by mitigating substrate inhibition is particularly novel and is an example where artificial membraneless organelle-like systems may provide new insights into physiological cell functions.

Distributed fibre optofluidic laser for chip-scale arrayed biochemical sensing

Optofluidic lasers (OFLs) are an emerging technological platform for biochemical sensing, and their good performance especially high sensitivity has been demonstrated. However, high-throughput detection with an OFL remains a major challenge due to the lack of reproducible optical microcavities. Here, we introduce the concept of a distributed fibre optofluidic laser (DFOFL) and demonstrate its potential for high-throughput sensing applications. Due to the precise fibre geometry control via fibre drawing, a series of identical optical microcavities uniformly distributed along a hollow optical fibre (HOF) can be achieved to obtain a one-dimensional (1D) DFOFL. An enzymatic reaction catalysed by horseradish peroxidase (HRP) can be monitored over time, and the HRP concentration is detected by DFOFL-based arrayed colorimetric detection. Experimentally, five-channel detection in parallel with imaging has been demonstrated. Theoretically, spatial multiplexing of hundreds of channels is achievable with DFOFL-based detection. The DFOFL wavelength is tuned over hundreds of nanometers by optimizing the dye concentration or reconfiguring the liquid gain materials. Extending this concept to a two-dimensional (2D) chip through wavelength multiplexing can further enhance its multi-functionality, including multi-sample detection and spectral analysis. This work opens the door to high-throughput biochemical sensing.

Antagonistic chemical coupling in self-reconfigurable host-guest protocells

Fabrication of compartmentalised chemical systems with nested architectures and biomimetic properties has important implications for controlling the positional assembly of functional components, spatiotemporal regulation of enzyme cascades and modelling of proto-organelle behaviour in synthetic protocells. Here, we describe the spontaneous capture of glucose oxidase-containing proteinosomes in pH-sensitive fatty acid micelle coacervate droplets as a facile route to multi-compartmentalised host–guest protocells capable of antagonistic chemical and structural coupling. The nested system functions co-operatively at low-substrate turnover, while high levels of glucose give rise to pH-induced disassembly of the droplets, release of the incarcerated proteinosomes and self-reconfiguration into spatially organised enzymatically active vesicle-in-proteinosome protocells. Co-encapsulation of antagonistic enzymes within the proteinosomes produces a sequence of self-induced capture and host–guest reconfiguration. Taken together, our results highlight opportunities for the fabrication of self-reconfigurable host–guest protocells and provide a step towards the development of protocell populations exhibiting both synergistic and antagonistic modes of interaction.

Multi-compartmentalised soft micro-systems are used as models of synthetic protocells. Here, the authors developed nested host–guest protocell constructs capable of self-reconfiguration in response to changes in pH generated by antagonistic modes of enzyme-mediated coupling.

Creation of Bifunctional Indicating Complex Based on Nanodiamonds and Extracellular Oxidases of Luminous Fungus Neonothopanus nambi

A bifunctional indicating complex was created by immobilization of extracellular oxidases (glucose oxidase and peroxidases) of luminous fungus Neonothopanus nambi onto modified nanodiamonds (MNDs) synthesized by detonation. It was found that the enzymes firmly adsorb onto MND particles and exhibit their catalytic activity. Model in vitro experiments showed that the created MND-enzymes complex is suitable for repeated use for analyte (glucose and phenol) testing and retains its activity after storage at 4°C in deionized water for 1 month. The data obtained offer the prospects for developing a new class of reusable multifunctional indicating and diagnostic test systems on the basis of MNDs and higher fungal enzymes for medical and ecological analytics.

Catalytic chemistry of glucose oxidase in cancer diagnosis and treatment

This tutorial review focuses on the state-of-the-art progress in GOx-based cancer diagnosis and treatment, including the general principles for the design and construction of GOx-based biosensors and cancer therapeutic approaches, and their biological applications in detail. Moreover, the current trends and key problems, as well as the challenges and future prospects of GOx-based catalytic systems in biomedicine are also discussed in the end.

An enzyme-like imprinted-polymer reactor with segregated quantum confinements for a tandem catalyst

This study was aimed at addressing the present challenge in tandem catalysts, as to how to furnish catalysts with tandem catalytic-ability without involving the precise control and man-made isolation of different types of catalytic sites. This objective was realized by constructing an enzyme-like imprinted-polymer reactor made of a unique polymer composite inspired from the compartmentalization of cells, a composite of a reactive imprinted polymer (containing acidic catalytic sites), and encapsulated metal nanoparticles (acting as catalytic reduction sites). The compilation of two types of catalytic sites with admissible access allowed this reactor to behave like compartments of cells for enzymatic reactions and hence catalytically constituted two quantum interaction-segregated domains, which led to the occurrence of catalytic tandem processes. Unlike the reported functional reactors that run tandem catalysis by largely depending on the precise control and man-made isolation of different types of catalytic sites, tandem catalysis in this reactor run naturally with segregated quantum confinements, which does not involve the precise control and isolation of different types of catalytic sites. This protocol presents new opportunities for the development of functional catalysts for complicated chemical processes.

This study was aimed at addressing the present challenge in tandem catalysts: how to furnish catalysts with tandem catalytic-ability without involving the precise control and man-made isolation of different types of catalytic sites.