Many extracellular matrices (ECMs) have a filamentous architecture, which influences cell growth and phenotype and imparts tissues with specific properties. Man-made fibrillar hydrogels can function ...as biomimetic materials to reproduce the filamentous nature and properties of ECMs and to serve as scaffolds for 3D cell culture and tissue engineering. Different types of synthetic nanofibrillar hydrogels have been developed, with diverse mechanisms of assembly and a variety of physical properties and applications. In this Review, we explore the design and properties of biomimetic man-made nanofibrillar hydrogels. We discuss the assembly of peptides, block copolymer worm-like micelles and filamentous nanoparticles into fibrillar hydrogels and investigate the relationship between structure and physical as well as biochemical properties. Potential applications for 3D cell culture and tissue engineering are examined, and the properties and structure of natural and man-made fibrillar hydrogels are compared. Finally, we critically assess current challenges and future directions of the field.Man-made fibrillar hydrogels mimic the structure of filamentous extracellular matrices and can be used as biomaterials for 3D cell culture and tissue engineering. In this Review, the authors discuss the design and properties of fibrillar hydrogels and explore different building blocks, assembly mechanisms, properties and applications.
Just as nanoparticles display properties that differ from those of bulk samples of the same material, ensembles of nanoparticles can have collective properties that are different to those displayed ...by individual nanoparticles and bulk samples. Self-assembly has emerged as a powerful technique for controlling the structure and properties of ensembles of inorganic nanoparticles. Here we review different strategies for nanoparticle self-assembly, the properties of self-assembled structures of nanoparticles, and potential applications of such structures. Many of these properties and possible applications rely on our ability to control the interactions between the electronic, magnetic and optical properties of the individual nanoparticles.
In this tutorial review we discuss recent advances in the application of microfluidics for the generation of microgels from synthetic and biological polymers. We summarize advantages and drawbacks of ...the current methods used in microfluidic synthesis and assembly of polymer microgels. Continuous microfluidic encapsulation of cells is discussed as an exemplary application of the microgels. The article is finalized with a perspective on future research in the field. The article will be of interest to chemists, cell biologists, pharmacologists, and medicinal chemists.
In this Concept article, recent advances in microfluidic platforms for the generation of cell‐laden hydrogel particles (microgels) are reported. Advances in the continuous microfluidic encapsulation ...of cells in droplets and microgels are critically reviewed, and currently used methods for the encapsulation of cells in polymer microgels are discussed. An outlook on current applications and future directions in this field of research are also presented. This article will be of interest to chemists, materials scientists, cell biologists, bioengineers, and pharmacologists.
The most recent advances in the use of microfluidic technology for the rapid high‐throughput production of highly monodisperse cell‐laden microgels are described. The review discusses the current state‐of‐art techniques in the field, followed by a discussion of future directions.
Many properties of nanoparticles are governed by their shape, size, polydispersity and surface chemistry. To apply nanoparticles in chemical sensing, medical diagnostics, catalysis, thermoelectrics, ...photovoltaics or pharmaceutics, they have to be synthesized with precisely controlled characteristics. This is a time-consuming, laborious and resource-intensive task, because nanoparticle syntheses often include multiple reagents and are conducted under interdependent experimental conditions. Machine learning (ML) offers a promising tool for the accelerated development of efficient protocols for nanoparticle synthesis and, potentially, for the synthesis of new types of nanoparticles. In this Review, we discuss ML algorithms that can be used for nanoparticle synthesis and highlight key approaches for the collection of large datasets. We examine ML-guided synthesis of semiconductor, metal, carbon-based and polymeric nanoparticles, and conclude with a discussion of current limitations, advantages and perspectives in the development of ML-assisted nanoparticle synthesis.Machine learning can be applied for the controlled synthesis of nanoparticles with precise properties. This Review discusses different machine learning approaches for the synthesis of semiconductor, metal, carbon-based and polymeric nanoparticles, and highlights key approaches for the collection of large datasets.
A polymer ligand–based strategy enables assembly of nanoscale particles into configurations reminiscent of molecules.
Self-limiting bonding
Although many routes have been developed to link together ...colloidal particles into controlled superstructures from dimers all the way up to three-dimensional lattices, they generally depend on coating the nanoparticle surfaces in specific ways to control the way they link up. By contrast, Yi
et al.
developed a ligand chemistry such that, when two particles link together, it changes the electrostatic properties to limit subsequent bonding (see the Perspective by Gang). Particles are coated with complementary polymer strands that undergo an acid-base neutralization reaction. This bonding is controlled by the length of the flexible ligands, whereas the arrangement of the bonded particles is controlled by electrostatic repulsions, thus giving two parameters to tune the shape of the assemblies that form.
Science
, this issue p.
1369
; see also p.
1305
Nanoparticle clusters with molecular-like configurations are an emerging class of colloidal materials. Particles decorated with attractive surface patches acting as analogs of functional groups are used to assemble colloidal molecules (CMs); however, high-yield generation of patchy nanoparticles remains a challenge. We show that for nanoparticles capped with complementary reactive polymers, a stoichiometric reaction leads to reorganization of the uniform ligand shell and self-limiting nanoparticle bonding, whereas electrostatic repulsion between colloidal bonds governs CM symmetry. This mechanism enables high-yield CM generation and their programmable organization in hierarchical nanostructures. Our work bridges the gap between covalent bonding taking place at an atomic level and colloidal bonding occurring at the length scale two orders of magnitude larger and broadens the methods for nanomaterial fabrication.
Colloidal quantum dot (QD) solids are emerging semiconductors that have been actively explored in fundamental studies of charge transport
and for applications in optoelectronics
. Forming ...high-quality QD solids-necessary for device fabrication-requires substitution of the long organic ligands used for synthesis with short ligands that provide increased QD coupling and improved charge transport
. However, in perovskite QDs, the polar solvents used to carry out the ligand exchange decompose the highly ionic perovskites
. Here we report perovskite QD resurfacing to achieve a bipolar shell consisting of an inner anion shell, and an outer shell comprised of cations and polar solvent molecules. The outer shell is electrostatically adsorbed to the negatively charged inner shell. This approach produces strongly confined perovskite QD solids that feature improved carrier mobility (≥0.01 cm
V
s
) and reduced trap density relative to previously reported low-dimensional perovskites. Blue-emitting QD films exhibit photoluminescence quantum yields exceeding 90%. By exploiting the improved mobility, we have been able to fabricate CsPbBr
QD-based efficient blue and green light-emitting diodes. Blue devices with reduced trap density have an external quantum efficiency of 12.3%; the green devices achieve an external quantum efficiency of 22%.
Over the past decade, droplet microfluidics has attracted growing interest in biology, medicine, and engineering. In this feature article, we review the advances in droplet microfluidics, primarily ...focusing on the research conducted by our group. Starting from the introduction to the mechanisms of microfluidic droplet formation and the strategies for cell encapsulation in droplets, we then focus on droplet transformation into microgels. Furthermore, we review three biomedical applications of droplet microfluidics, that is, 3D cell culture, single-cell analysis, and in vitro organ and disease modeling. We conclude with our perspective on future directions in the development of droplet microfluidics for biomedical applications.
Although Nature has always been a common source of inspiration in the development of artificial materials, only recently has the ability of man-made materials to produce complex three-dimensional ...(3D) structures from two-dimensional sheets been explored. Here we present a new approach to the self-shaping of soft matter that mimics fibrous plant tissues by exploiting small-scale variations in the internal stresses to form three-dimensional morphologies. We design single-layer hydrogel sheets with chemically distinct, fibre-like regions that exhibit differential shrinkage and elastic moduli under the application of external stimulus. Using a planar-to-helical three-dimensional shape transformation as an example, we explore the relation between the internal architecture of the sheets and their transition to cylindrical and conical helices with specific structural characteristics. The ability to engineer multiple three-dimensional shape transformations determined by small-scale patterns in a hydrogel sheet represents a promising step in the development of programmable soft matter.
Patient-derived tumor organoids (PDOs) are a highly promising preclinical model that recapitulates the histology, gene expression, and drug response of the donor patient tumor. Currently, PDO culture ...relies on basement-membrane extract (BME), which suffers from batch-to-batch variability, the presence of xenogeneic compounds and residual growth factors, and poor control of mechanical properties. Additionally, for the development of new organoid lines from patient-derived xenografts, contamination of murine host cells poses a problem. We propose a nanofibrillar hydrogel (EKGel) for the initiation and growth of breast cancer PDOs. PDOs grown in EKGel have histopathologic features, gene expression, and drug response that are similar to those of their parental tumors and PDOs in BME. In addition, EKGel offers reduced batch-to-batch variability, a range of mechanical properties, and suppressed contamination from murine cells. These results show that EKGel is an improved alternative to BME matrices for the initiation, growth, and maintenance of breast cancer PDOs.
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