Tailoring the Heterogeneous Structure of Macro-Fibers Assembled by Bacterial Cellulose Nanofibrils for Tissue Engineering Scaffolds.

Bacterial cellulose/oxidized bacterial cellulose nanofibrils (BC/oxBCNFs) macro-fibers are developed as a novel scaffold for vascular tissue engineering. Utilizing a low-speed rotary coagulation spinning technique and precise solvent control, macro-fibers with a unique heterogeneous structure with dense surface and porous core are created. Enhanced by a polydopamine (PDA) coating, these macro-fibers offer robust mechanical integrity, high biocompatibility, and excellent cell adhesion. When cultured with endothelial cells (ECs) and smooth muscle cells (SMCs), the macro-fibers support healthy cell proliferation and exhibit a unique spiral SMC alignment, demonstrating their vascular suitability. This innovative strategy opens new avenues for advances in tissue engineering.

NIR-II-activated biocompatible hollow nanocarbons for cancer photothermal therapy.

Photothermal therapy has attracted extensive attentions in cancer treatment due to its precise spatial-temporal controllability, minimal invasiveness, and negligible side effects. However, two major deficiencies, unsatisfactory heat conversion efficiency and limited tissue penetration depth, hugely impeded its clinical application. In this work, hollow carbon nanosphere modified with polyethylene glycol-graft-polyethylenimine (HPP) was elaborately synthesized. The synthesized HPP owns outstanding physical properties as a photothermal agent, such as uniform core-shell structure, good biocompatibility and excellent heat conversion efficiency. Upon NIR-II laser irradiation, the intracellular HPP shows excellent photothermal activity towards cancer cell killing. In addition, depending on the large internal cavity of HPP, the extended biomedical application as drug carrier was also demonstrated. In general, the synthesized HPP holds a great potential in NIR-II laser-activated cancer photothermal therapy.

All-aqueous synthesis of alginate complexed with fibrillated protein microcapsules for membrane-bounded culture of tumor spheroids.

Water-in-water (W/W) emulsions provide bio-compatible all-aqueous compartments for artificial patterning and assembly of living cells. Successful entrapment of cells within a W/W emulsion via the formation of semipermeable capsules is a prerequisite for regulating on the size, shape, and architecture of cell aggregates. However, the high permeability and instability of the W/W interface, restricting the assembly of stable capsules, pose a fundamental challenge for cell entrapment. The current study addresses this problem by synthesizing multi-armed protein fibrils and controlling their assembly at the W/W interface. The multi-armed protein fibrils, also known as 'fibril clusters', were prepared by cross-linking lysozyme fibrils with multi-arm polyethylene glycol (PEG) via click chemistry. Compared to linear-structured fibrils, fibril clusters are strongly adsorbed at the W/W interface, forming an interconnected meshwork that better stabilizes the W/W emulsion. Moreover, when fibril clusters are complexed with alginate, the hybrid microcapsules demonstrate excellent mechanical robustness, semi-permeability, cytocompatibility and biodegradability. These advantages enable the encapsulation, entrapment and long-term culture of tumor spheroids, with great promise for applications for anti-cancer drug screening, tumor disease modeling, and tissue repair engineering.

Multicompartmental coacervate-based protocell by spontaneous droplet evaporation.

Hierarchical compartmentalization, a hallmark of both primitive and modern cells, enables the concentration and isolation of biomolecules, and facilitates spatial organization of biochemical reactions. Coacervate-based compartments can sequester and recruit a large variety of molecules, making it an attractive protocell model. In this work, we report the spontaneous formation of core-shell cell-sized coacervate-based compartments driven by spontaneous evaporation of a sessile droplet on a thin-oil-coated substrate. Our analysis reveals that such far-from-equilibrium architectures arise from multiple, coupled segregative and associative liquid-liquid phase separation, and are stabilized by stagnation points within the evaporating droplet. The formation of stagnation points results from convective capillary flows induced by the maximum evaporation rate at the liquid-liquid-air contact line. This work provides valuable insights into the spontaneous formation and maintenance of hierarchical compartments under non-equilibrium conditions, offering a glimpse into the real-life scenario.

Bacteria-Inspired Aqueous-in-Aqueous Compartmentalization by In Situ Interfacial Biomineralization.

Compartmentalization is essential for living cells to orchestrate their biological processes with controlled external influences. Thus, compartmentalization has been a constant theme for cell-mimicking materials. Despite recent advances in engineering compartmentalized materials as synthetic cells and organelles, it remains difficult to produce robust and well-ordered compartments with secluded environments in aqueous surroundings. Nature creates hierarchically ordered compartmentalized materials by utilizing bio-catalyzed mineralization, inspired by which, mechanically robust all-aqueous compartments are developed by engineering a mild biomimetic mineralization at aqueous/aqueous interfaces. The enzyme-induced biomineralization generates a layer of densely-packed particles, acting as an armor to enclose aqueous interiors. This strategy of in situ bio-synthesized compartments is different from current strategies, where compartments are constructed by randomly adsorbed particles at interface, leading to inadequately controlled properties of compartments. To demonstrate the robustness and adaptiveness of the in situ bio-synthesized all-aqueous compartments, these are utilized as drug delivery materials by sequestering protein drugs at their aqueous interiors and releasing when exposing to gastric environments. The study provides new ways to fabricate compartmentalized materials with well-defined properties, unlocking routes to the next generation of self-assembled materials and structures by integrating aqueous two-phase systems with biomineralization.

Facile and Programmable Capillary-Induced Assembly of Prototissues via Hanging Drop Arrays.

An important goal for bottom-up synthetic biology is to construct tissue-like structures from artificial cells. The key is the ability to control the assembly of the individual artificial cells. Unlike most methods resorting to external fields or sophisticated devices, inspired by the hanging drop method used for culturing spheroids of biological cells, we employ a capillary-driven approach to assemble giant unilamellar vesicles (GUVs)-based protocells into colonized prototissue arrays by means of a coverslip with patterned wettability. By spatially confining and controllably merging a mixed population of lipid-coated double-emulsion droplets that hang on a water/oil interface, an array of synthetic tissue-like constructs can be obtained. Each prototissue module in the array comprises multiple tightly packed droplet compartments where interfacial lipid bilayers are self-assembled at the interfaces both between two neighboring droplets and between the droplet and the external aqueous environment. The number, shape, and composition of the interconnected droplet compartments can be precisely controlled. Each prototissue module functions as a processer, in which fast signal transports of molecules via cell-cell and cell-environment communications have been demonstrated by molecular diffusions and cascade enzyme reactions, exhibiting the ability to be used as biochemical sensing and microreactor arrays. Our work provides a simple yet scalable and programmable method to form arrays of prototissues for synthetic biology, tissue engineering, and high-throughput assays.

Micro-/Nano-Structures on Biodegradable Magnesium@PLGA and Their Cytotoxicity, Photothermal, and Anti-Tumor Effects.

The size and structural control of particulate carriers for imaging agents and therapeutics are constant themes in designing smart delivery systems. This is motivated by the causal relationship between geometric parameters and functionalities of delivery vehicles. Here, both in vitro and in vivo, the controlling factors for cytotoxicity, photothermal, and anti-tumor effects of biodegradable magnesium@poly(lactic-co-glycolic acid (Mg@PLGA) particulate carriers with different sizes and shell thicknesses are investigated. Mg@PLGA microspheres fabricated by microfluidic emulsification are shown to have higher Mg encapsulation efficiency, 87%, than nanospheres by ultrasonic homogenization, 50%. The photothermal and anti-tumor effects of Mg@PLGA spheres are found to be dictated by their Mg content, irrelevant to size and structural features, as demonstrated in both in vitro cell assays and in vivo mice models. These results also provide important implications for designing and fabricating stimuli-responsive drug delivery vehicles.

Interface Engineering in Multiphase Systems toward Synthetic Cells and Organelles: From Soft Matter Fundamentals to Biomedical Applications.

Synthetic cells have a major role in gaining insight into the complex biological processes of living cells; they also give rise to a range of emerging applications from gene delivery to enzymatic nanoreactors. Living cells rely on compartmentalization to orchestrate reaction networks for specialized and coordinated functions. Principally, the compartmentalization has been an essential engineering theme in constructing cell-mimicking systems. Here, efforts to engineer liquid-liquid interfaces of multiphase systems into membrane-bounded and membraneless compartments, which include lipid vesicles, polymer vesicles, colloidosomes, hybrids, and coacervate droplets, are summarized. Examples are provided of how these compartments are designed to imitate biological behaviors or machinery, including molecule trafficking, growth, fusion, energy conversion, intercellular communication, and adaptivity. Subsequently, the state-of-art applications of these cell-inspired synthetic compartments are discussed. Apart from being simplified and cell models for bridging the gap between nonliving matter and cellular life, synthetic compartments also are utilized as intracellular delivery vehicles for nuclei acids and nanoreactors for biochemical synthesis. Finally, key challenges and future directions for achieving the full potential of synthetic cells are highlighted.

Mechanically and functionally strengthened tissue adhesive of chitin whisker complexed chitosan/dextran derivatives based hydrogel.

Schiff base reaction crosslinking hydrogels are advantageous by rapid formation and absence of external crosslinkers. However, poor mechanical hindered their broader applications. Here, a mechanically strengthened tissue adhesive was constructed through incorporation of chitin nano-whiskers (CtNWs) with a Schiff base crosslinking hydrogel of carboxymethyl chitosan (CMCS) and dextran dialdehyde (DDA). The optimal formulation of complexed hydrogel exhibited 1.87 folds higher compressive stress than non-complexed and 1.51 time higher adhesive strength on porcine skin. The complexed hydrogel exhibited negligible cytotoxicity, anti-swelling performance in PBS, optimum antibacterial and hemostatic capacities. In vivo implantation studies confirmed the complexed hydrogel was degradable without long-term inflammatory responses. Desirable efficacy of injectable complexed hydrogel as hemostat was demonstrated in rat liver injury model, which could avoid severe postoperative adhesion and necrosis as observed in the treatment with commercial 3 M™ vetbond™ tissue adhesive. The results highlighted that the complexed hydrogel potentiated rapid hemostasis and wound repair applications.

Bioinspired photonic barcodes for multiplexed target cycling and hybridization chain reaction.

Multiplexed detection of microRNA (miRNA) is of great value in clinical diagnosis. Here, a new type of polydopamine (PDA) encapsulated photonic crystal (PhC) barcodes are employed for target-triggering cycle amplification and hybridization chain reaction (HCR) to achieve multiplex miRNA quantification. The PDA-decorated PhC barcodes not only exhibit distinctive structural color for different encoding miRNAs, they also can immobilize biomolecules, allowing subsequent reaction with amino-modified hairpin probes (H1). When the PDA-decorated PhC barcodes are used in assays, target miRNAs can be circularly used to initiate HCR for cycle amplification. Therefore, by tuning the structural colors of the PDA-integrated PhC, the multiplexed miRNA quantification could be realized. We demonstrate that our strategy for multiplexed detection of miRNA is reasonably accurate, reliable and repeatable, with a detection limit as low as 8.0 fM. Our results show that PDA encapsulated PhC barcodes as a novel platform offer a pathway toward the multiplex analysis of low-abundance biomarkers for biomedical assays.

Manipulation of viscous all-aqueous jets by electrical charging.

We demonstrate the manipulation of viscous all-aqueous jets by electrical charging. At sufficiently high voltages, the folding of an uncharged viscous jet is suppressed, and the jet diameter can be adjusted by varying the applied voltage or the fluid flow rates. This inspires new ways to fabricate biocompatible fibers.

Fabrication and characterization of monodisperse PLGA-alginate core-shell microspheres with monodisperse size and homogeneous shells for controlled drug release.

Monodisperse PLGA-alginate core-shell microspheres with controlled size and homogeneous shells were first fabricated using capillary microfluidic devices for the purpose of controlling drug release kinetics. Sizes of PLGA cores were readily controlled by the geometries of microfluidic devices and the fluid flow rates. PLGA microspheres with sizes ranging from 15 to 50µm were fabricated to investigate the influence of the core size on the release kinetics. Rifampicin was loaded into both monodisperse PLGA microspheres and PLGA-alginate core-shell microspheres as a model drug for the release kinetics studies. The in vitro release of rifampicin showed that the PLGA core of all sizes exhibited sigmoid release patterns, although smaller PLGA cores had a higher release rate and a shorter lag phase. The shell could modulate the drug release kinetics as a buffer layer and a near-zero-order release pattern was observed when the drug release rate of the PLGA core was high enough. The biocompatibility of PLGA-alginate core-shell microspheres was assessed by MTT assay on L929 mouse fibroblasts cell line and no obvious cytotoxicity was found. This technique provides a convenient method to control the drug release kinetics of the PLGA microsphere by delicately controlling the microstructures. The obtained monodisperse PLGA-alginate core-shell microspheres with monodisperse size and homogeneous shells could be a promising device for controlled drug release.