Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter

Microfluidic fluorescence‐activated cell sorters (μFACS) have attracted considerable interest because of their ability to identify and separate cells in inexpensive and biosafe ways. Here a high‐performance μFACS is presented by integrating a standing surface acoustic wave (SSAW)‐based, 3D cell‐focusing unit, an in‐plane fluorescent detection unit, and an SSAW‐based cell‐deflection unit on a single chip. Without using sheath flow or precise flow rate control, the SSAW‐based cell‐focusing technique can focus cells into a single file at a designated position. The tight focusing of cells enables an in‐plane‐integrated optical detection system to accurately distinguish individual cells of interest. In the acoustic‐based cell‐deflection unit, a focused interdigital transducer design is utilized to deflect cells from the focused stream within a minimized area, resulting in a high‐throughput sorting ability. Each unit is experimentally characterized, respectively, and the integrated SSAW‐based FACS is used to sort mammalian cells (HeLa) at different throughputs. A sorting purity of greater than 90% is achieved at a throughput of 2500 events s^?1. The SSAW‐based FACS is efficient, fast, biosafe, biocompatible and has a small footprint, making it a competitive alternative to more expensive, bulkier traditional FACS.     

Design of Plasma Surface‐Activated,Electrospun Polylactide Non‐Wovens with Improved Cell Acceptance

Electrospinning is a versatile technique to generate tissue engineering matrices possessing structural features similar to the extracellular matrix. Biodegradable polylactides are well suited for processing by this technique, but their innate hydrophobicity impairs initial protein adsorption and cell adhesion. In this work, therefore, electrospun poly(L ‐lactide‐co‐D,L ‐lactide) (70/30) non‐wovens are modified with an ultrathin plasma‐polymerized allylamine (PPAAm) coating. Using scanning electron microsocopy (SEM), it is shown that the fiber structure of the non‐woven is not affected by the plasma treatment. X‐ray photoelectron spectroscopy (XPS) and contact angle measurements of PPAAm‐coated non‐wovens confirm the presence of nitrogen and oxygen‐functional groups in the coating and a hydrophilic nature of the coated non‐woven surface. Cell experiments in vitro demonstrate that the PPAAm‐coated surface promotes occupancy of the non‐woven by human MG‐63 osteoblasts accompanied by improved initial cell spreading and filopodia formation along and between the electrospun polylactide fibers. Overall, plasma‐assisted incorporation of amino groups into electrospun polylactone non‐wovens represents a promising approach to tissue engineering scaffolds with improved cell–material interfaces.     

A Fluorescence–Phosphorescence–Phosphorescence Triple‐Channel Emission Strategy for Full‐Color Luminescence

Organic luminogens constitute promising prototypes for various optoelectronic applications. Since gaining distinct color emissions normally requires the alternation of the conjugated backbone, big issues remain in material synthetic cost and skeleton compatibility while pursuing full‐color luminescence. Upon a facile one‐step coupling, three simple but smart perchalcogenated (O, S, and Se) arenes are synthesized. They exhibit strong luminescent tricolor primaries (i.e., blue, green, and red, respectively) in the solid state with a superior quantum yield up to >40% (5–10 times higher than that in corresponding solutions). The properties originate from a fluorescence–phosphorescence–phosphorescence triple‐channel emission effect, which is regulated by S and Se heavy atoms–dependent intersystem crossing upon molecular packing, as well as Se–Se atom interaction–caused energy splittings. Consequently, full‐color luminescence, including a typical white‐light luminescence with a Commission Internationale de I'Eclairage coordinate of (0.30, 0.35), is realized by complementarily incorporating these tricolor luminescent materials in the film. Moreover, mechanochromic luminescent color conversions are also observed to achieve the fine‐tuning of the luminescent tints. This strategy can be smart to address full‐color luminescence on the same molecular skeleton, showing better material compatibility as an alternative to the traditional multiple‐luminophore engineering.     

Phenome–Genome Profiling of Single Bacterial Cell by Raman‐Activated Gravity‐Driven Encapsulation and Sequencing

The small size and low DNA amount of bacterial cells have hindered establishing phenome–genome links in a precisely indexed, one‐cell‐per‐reaction manner. Here, Raman‐Activated Gravity‐driven single‐cell Encapsulation and Sequencing (RAGE‐Seq) is presented, where individual cells are phenotypically screened via single‐cell Raman spectra (SCRS) in an aquatic, vitality‐preserving environment, then the cell with targeted SCRS is precisely packaged in a picoliter microdroplet and readily exported in a precisely indexed, “one‐cell‐one‐tube” manner. Such integration of microdroplet encapsulation to Raman‐activated sorting ensures high‐coverage one‐cell genome sequencing or cultivation that is directly linked to metabolic phenotype. For clinical Escherichia coli isolates, genome assemblies derived from precisely one cell via RAGE‐Seq consistently reach >95% coverage. Moreover, directly from a urine sample of urogenital tract infection, metabolic‐activity‐based antimicrobial susceptibility phenotypes and genome sequence of 99.5% coverage are obtained simultaneously from precisely one cell. This single‐cell global mutation map corroborates resistance phenotype and genotype, and unveils epidemiological features with high specificity and sensitivity. The ability to profile and correlate bacterial metabolic phenome and high‐quality genome sequences at one‐cell resolution suggests broad application of RAGE‐Seq.     

Single‐Layer Ternary Chalcogenide Nanosheet as a Fluorescence‐Based “Capture‐Release” Biomolecular Nanosensor

The novel application of two‐dimensional (2D) single‐layer ternary chalcogenide nanosheets as “capture‐release” fluorescence‐based biomolecular nanosensors is demonstrated. Fluorescently labeled biomolecular probe is first captured by the ultrathin Ta₂NiS₅ nanosheets and then released upon adding analyte containing a target biomolecule due to the higher probe‐target affinity. Here, the authors use a nucleic acid probe for the model target biomolecule Plasmodium lactate dehydrogenase, which is an important malarial biomarker. The ultrathin Ta₂NiS₅ nanosheet serves as a highly efficient fluorescence quencher and the nanosensor developed from the nanosheet is highly sensitive and specific toward the target biomolecule. Apart from the specificity toward the target biomolecule in homogeneous solutions, the developed nanosensor is capable of detecting and differentiating the target in heterogeneous solutions consisting of either a mixture of biomolecules or serum, with exceptional specificity. The simplicity of the “capture‐release” method, by eliminating the need for preincubation of the probe with the test sample, may facilitate further development of portable and rapid biosensors. The authors anticipate that this ternary chalcogenide nanosheet‐based biomolecular nanosensor will be useful for the rapid detection and differentiation of a wide range of chemical and biological species.     

Design of Diketopyrrolopyrrole (DPP)‐Based Small Molecules for Organic‐Solar‐Cell Applications

After the first report in 2008, diketopyrrolopyrrole (DPP)‐based small‐molecule photovoltaic materials have been intensively explored. The power conversion efficiencies (PCEs) for the DPP‐based small‐molecule donors have been improved up to 8%. Furthermore, through judicious structure modification, DPP‐based small molecules can also be converted into electron‐acceptor materials, and, recently, some exciting progress has been achieved. The development of DPP‐based photovoltaic small molecules is summarized here, and the photovoltaic performance is discussed in relation to structural modifications, such as the variations of donor–acceptor building blocks, alkyl substitutions, and the type of conjugated bridges, as well as end‐capped groups. It is expected that the discussion will provide a guideline in the exploration of novel and promising DPP‐containing photovoltaic small molecules.     

Inertial Microfluidic Cell Stretcher (iMCS): Fully Automated,High‐Throughput,and Near Real‐Time Cell Mechanotyping

Mechanical biomarkers associated with cytoskeletal structures have been reported as powerful label‐free cell state identifiers. In order to measure cell mechanical properties, traditional biophysical (e.g., atomic force microscopy, micropipette aspiration, optical stretchers) and microfluidic approaches were mainly employed; however, they critically suffer from low‐throughput, low‐sensitivity, and/or time‐consuming and labor‐intensive processes, not allowing techniques to be practically used for cell biology research applications. Here, a novel inertial microfluidic cell stretcher (iMCS) capable of characterizing large populations of single‐cell deformability near real‐time is presented. The platform inertially controls cell positions in microchannels and deforms cells upon collision at a T‐junction with large strain. The cell elongation motions are recorded, and thousands of cell deformability information is visualized near real‐time similar to traditional flow cytometry. With a full automation, the entire cell mechanotyping process runs without any human intervention, realizing a user friendly and robust operation. Through iMCS, distinct cell stiffness changes in breast cancer progression and epithelial mesenchymal transition are reported, and the use of the platform for rapid cancer drug discovery is shown as well. The platform returns large populations of single‐cell quantitative mechanical properties (e.g., shear modulus) on‐the‐fly with high statistical significances, enabling actual usages in clinical and biophysical studies.     

Light‐Activated,Multi‐Semiconductor Hybrid Microswimmers

Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO₂) and cuprous oxide (Cu₂O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light‐activated microswimmers made from only TiO₂ or Cu₂O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength‐dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel‐free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO₂/Cu₂O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light‐activated particle, which is not limited to the specific geometries and materials presented in this study.     

Non‐Equilibrium Assembly of Light‐Activated Colloidal Mixtures

The collective phenomena exhibited by artificial active matter systems present novel routes to fabricating out‐of‐equilibrium microscale assemblies. Here, the crystallization of passive silica colloids into well‐controlled 2D assemblies is shown, which is directed by a small number of self‐propelled active colloids. The active colloids are titania–silica Janus particles that are propelled when illuminated by UV light. The strength of the attractive interaction and thus the extent of the assembled clusters can be regulated by the light intensity. A remarkably small number of the active colloids is sufficient to induce the assembly of the dynamic crystals. The approach produces rationally designed colloidal clusters and crystals with controllable sizes, shapes, and symmetries. This multicomponent active matter system offers the possibility of obtaining structures and assemblies that cannot be found in equilibrium systems.