Microliter Volumes Research Articles

Unlocking Intracellular Protein Delivery by Harnessing Polymersomes Synthesized at Microliter Volumes using Photo-PISA.

Efficient delivery of therapeutic proteins and vaccine antigens to intracellular targets is challenging due to generally poor cell membrane permeation and endolysosomal entrapment causing degradation. Herein, these challenges are addressed by developing an oxygen-tolerant photoinitiated polymerization-induced self-assembly (Photo-PISA) process, allowing for the microliter-scale (10µL) synthesis of protein-loaded polymersomes directly in 1536-well plates. High-resolution techniques capable of analysis at a single particle level are employed to analyze protein encapsulation and release mechanisms. Using confocal microscopy and super-resolution stochastic optical reconstruction microscopy (STORM) imaging, their ability to deliver proteins into the cytosol following endosomal escape is subsequently visualized. Lastly, the adaptability of these polymersomes is exploited to encapsulate and deliver a prototype vaccine antigen, demonstrating its ability to activate antigen-presenting cells and support antigen cross-presentation for applications in subunit vaccines and cancer immunotherapy. This combination of ultralow volume synthesis and efficient intracellular delivery holds significant promise for unlocking the high throughput screening of a broad range of otherwise cost-prohibitive or early-stage therapeutic protein and vaccine antigen candidates that can be difficult to obtain in large quantities. The versatility of this platform for rapid screening of intracellular protein delivery can result in significant advancements across the fields of nanomedicine and biomedical engineering.

Microscale sampling of the coral gastrovascular cavity reveals a gut-like microbial community

Animal guts contain numerous microbes, which are critical for nutrient assimilation and pathogen defence. While corals and other Cnidaria lack a true differentiated gut, they possess semi-enclosed gastrovascular cavities (GVCs), where vital processes such as digestion, reproduction and symbiotic exchanges take place. The microbiome harboured in GVCs is therefore likely key to holobiont fitness, but remains severely understudied due to challenges of working in these small compartments. Here, we developed minimally invasive methodologies to sample the GVC of coral polyps and characterise the microbial communities harboured within. We used glass capillaries, low dead volume microneedles, or nylon microswabs to sample the gastrovascular microbiome of individual polyps from six species of corals, then applied low-input DNA extraction to characterise the microbial communities from these microliter volume samples. Microsensor measurements of GVCs revealed anoxic or hypoxic micro-niches, which persist even under prolonged illumination with saturating irradiance. These niches harboured microbial communities enriched in putatively microaerophilic or facultatively anaerobic taxa, such as Epsilonproteobacteria. Some core taxa found in the GVC of Lobophyllia hemprichii from the Great Barrier Reef were also detected in conspecific colonies held in aquaria, indicating that these associations are unlikely to be transient. Our findings suggest that the coral GVC is chemically and microbiologically similar to the gut of higher Metazoa. Given the importance of gut microbiomes in mediating animal health, harnessing the coral “gut microbiome” may foster novel active interventions aimed at increasing the resilience of coral reefs to the climate crisis.

Room-temperature mL-to-μL quantitative liquid concentration device for cyclone flow.

Highly sensitive quantitative analysis of liquids is required in various fields. Analytical instruments and devices such as chromatography, spectroscopic analysis, DNA sequencers, immunoassay, mass spectrometry, and microfluidic devices are utilized for this purpose. Typically, the sample volume is at the milliliter scale, while the analysis volume is at the microliter scale. Consequently, most of the sample is discarded. Therefore, a universal volume interface is required to quantitatively concentrate samples from milliliter to microliter volume. This study introduces a liquid quantitative function to the cyclone concentration method using a millimeter-scale channel, which is highly suitable for controlling liquids at the microliter scale due to its high fluidic resistance against cyclone flow. This method enables the effective control of liquid concentration by cyclone flow. The optimum channel structure is investigated, and a 33-fold concentration of aqueous solutions is demonstrated. Finally, the concentration device is applied to measure molybdenum ions in a river.

Plasmonic Optical Fiber Sensors and Molecularly Imprinted Polymers for Glyphosate Detection at an Ultra-Wide Range

In this study, a surface plasmon resonance (SPR) sensor based on modified plastic optical fibers (POFs) was combined with a specific molecularly imprinted polymer (MIP), used as a synthetic receptor, for glyphosate (GLY) determination in aqueous solutions. Since GLY is a non-selective herbicide associated with severe environmental and health problems, detecting glyphosate in environmental and biological samples remains challenging. The selective interaction between the MIP layer and GLY is monitored by exploiting the SPR phenomenon at the POF’s gold surface. Experimental results show that in about ten minutes and by dropping microliter volume samples, the presented optical–chemical sensor can quantify up to three orders of magnitude of GLY concentrations, from nanomolar to micromolar, due to a thin MIP layer over the SPR surface. The developed optical–chemical sensor presents a detection limit of about 1 nM and can be used for onsite GLY measurements. Moreover, the experimental analysis demonstrated the high selectivity of the proposed POF-based chemical sensor.

Stromal cells engineered to express T cell factors induce robust CLL cell proliferation in vitro and in PDX co-transplantations allowing the identification of RAF inhibitors as anti-proliferative drugs

Several in vitro models have been developed to mimic chronic lymphocytic leukemia (CLL) proliferation in immune niches; however, they typically do not induce robust proliferation. We prepared a novel model based on mimicking T-cell signals in vitro and in patient-derived xenografts (PDXs). Six supportive cell lines were prepared by engineering HS5 stromal cells with stable expression of human CD40L, IL4, IL21, and their combinations. Co-culture with HS5 expressing CD40L and IL4 in combination led to mild CLL cell proliferation (median 7% at day 7), while the HS5 expressing CD40L, IL4, and IL21 led to unprecedented proliferation rate (median 44%). The co-cultures mimicked the gene expression fingerprint of lymph node CLL cells (MYC, NFκB, and E2F signatures) and revealed novel vulnerabilities in CLL-T-cell-induced proliferation. Drug testing in co-cultures revealed for the first time that pan-RAF inhibitors fully block CLL proliferation. The co-culture model can be downscaled to five microliter volume for large drug screening purposes or upscaled to CLL PDXs by HS5-CD40L-IL4 ± IL21 co-transplantation. Co-transplanting NSG mice with purified CLL cells and HS5-CD40L-IL4 or HS5-CD40L-IL4-IL21 cells on collagen-based scaffold led to 47% or 82% engraftment efficacy, respectively, with ~20% of PDXs being clonally related to CLL, potentially overcoming the need to co-transplant autologous T-cells in PDXs.

Frequency multiplexing enables parallel multi-sample EPR

Electron paramagnetic resonance (EPR) spectroscopy stands out as a powerful analytical technique with extensive applications in the fields of biology, chemistry, physics, and material sciences. It proves invaluable for investigating the molecular structure and reaction mechanisms of substances containing unpaired electrons, such as metal complexes, organic and inorganic radicals, and intermediate states in chemical reactions. However, despite their remarkable capabilities, EPR systems face significant limitations in terms of sample throughput, as current commercial systems only target the analysis of one sample at a time. Here we introduce a novel scheme for conducting ultra-high frequency continuous-wave EPR (CW EPR) targeting the EPR spectroscopy of multiple microliter volume samples in parallel. Our proof-of-principle prototype involves two decoupled detection cells equipped with high qualty factor Q=104\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q=104$$\\end{document} solenoidal coils tuned to 488 and 589 MHz, ensuring a significant frequency gap for effective radio frequency (RF) decoupling between the channels. To further enhance electromagnetic decoupling, an orthogonal alignment of the coils was adopted. The paper further presents an innovative radiofrequency circuit concept that utilizes a single physical RF channel to simultaneously conduct parallel EPR on up to eight cells. Parallel EPR experiments on two BDPA samples, each with a sample volume of 18.3 μL, registered signal-to-noise ratios of 255 and 252 for the two EPR measurement cells, with no observable coupling. The showcased prototype, built using cost-effective commercially available fabrication technology, is readily scalable and represents an initial step with promising potential for advancing sample screening with high-throughput parallel EPR.

Facile fabrication of high thickness hydrophilic polymer brushes via Surface-Initiated Microliter-Scale copper mediated PhotoATRP toward antifouling surfaces

The recent development of sustainable chemistry motivates scientists to develop economically favourable, highly efficient, and environmentally friendly polymerization techniques. This contribution demonstrates a facile fabrication of hydrophilic polymer brushes via surface-initiated photochemically induced atom transfer radical polymerization using a copper catalyst in low concentrations and microlitre volume of polymerization mixture (SI-μL-CuPhotoATRP). The fabrication proceeds by sandwiching of μL reaction solution between a Si-wafer modified with ATRP-initiator and a glass slide under atmospheric and ambient conditions. Optimization of reaction conditions was realized on hydrophilic monomer such as 2-hydroxyethyl methacrylate (HEMA). Effect of various experimental parameters such as light intensity, solvents, ligands, the volume of the reaction solution, size of the Si-wafers, amount of CuBr2, and CuBr2/ligand ratio in kinetics, linear increase of polymer layer thickness, final thickness and profile of unmodified edges were investigated. The successful fabrication of hydrophilic polymer brushes is confirmed via Fourier transfer infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), profilometry and water contact angle. A linear thickness increase with time up to at least 300 nm was achieved, compared to polymethacrylate layers with thickness up to approximately 100 nm previously published by using photoATRP. The general applicability of the optimized conditions for SI-μL-CuPhotoATRP was further proved for two additional hydrophilic monomers, such as glycidyl methacrylate and 2-hydroxypropyl methacrylate. Furthermore, sequential homo and block copolymerization demonstrated the living character of fabrication conditions, permitting facile fabrication of well-controlled tetra block homo/copolymer brushes with a pyramid-like pattern on Si-wafer. Poly(2-hydroxyethyl methacrylate) (PHEMA) brushes-grown surfaces exhibit excellent antifouling properties and long-term structural stability. The facile, affordable, and environmentally friendly SI-μL-CuPhotoATRPapproachprovides avenues for various surface modifications, such as biomedical, soft robotic, and coating applications.

Advantages of the low-temperature secondary emission mass spectrometry in analysis of metal ions in water samples revisited

A problem of necessity of concentrating trace admixtures of metal ions required for ecological water analysis can be overcome by harnessing a physical phenomenon of phase separation in aqueous solutions during their freezing. It is shown that the accumulation of metal-containing solutes in the channels between ice crystallites in the frozen solids is sufficient for their successful detection by means of low-temperature secondary emission mass spectrometry. Sufficiency of microliters volumes of water is an advantage of such an approach. Observation of various types of metal ions in frozen water samples is demonstrated on the examples of tap water, sea water, snow and a medicinal preparation. Revisiting and summation of physical basics of mass spectrometric examining of frozen water-inorganic salt solutions and estimates of advancement of mass spectrometric instrumentation permit us to propose a workflow for accelerated and simplified mass spectrometric detection of metal pollutants in water.

A skin-interfaced, miniaturized platform for triggered induction, capture and colorimetric multicomponent analysis of microliter volumes of sweat

Eccrine sweat can serve as a source of biomarkers for assessing physiological health and nutritional balance, for tracking loss of essential species from the body and for evaluating exposure to hazardous substances. The growing interest in this relatively underexplored class of biofluid arises in part from its non-invasive ability for capture and analysis. The simplest devices, and the only ones that are commercially available, exploit soft microfluidic constructs and colorimetric assays with purely passive modes of operation. The most sophisticated platforms exploit batteries, electronic components and radio hardware for inducing sweat, for electrochemical evaluation of its content and for wireless transmission of this information. The work reported here introduces a technology that combines the advantages of these two different approaches, in the form of a cost-effective, easy-to-use device that supports on-demand evaluation of multiple biomarkers in sweat. This flexible, skin-interfaced, miniaturized system incorporates a hydrogel that contains an approved drug to activate eccrine sweat glands, electrodes and a simple circuit and battery to delivery this drug by iontophoresis through the surface of the skin, microfluidic channels and microreservoirs to capture the induced sweat, and multiple colorimetric assays to evaluate the concentrations of chloride, zinc, and iron. As demonstrated in healthy human participants monitored before and after a meal, such devices yield results that match those of traditional laboratory analysis techniques. Clinical studies that involve cystic fibrosis pediatric patients illustrate the use of this technology as a simple, painless, and reliable alternative to traditional hospital systems for measurements of sweat chloride.

Microfluidic devices, materials, and recent progress for petroleum applications: A review

AbstractMicrofluidic devices are miniaturized systems that manipulate fluids on a small scale, typically at microlitre or nanolitre volumes. They have received significant attention in various industries, including petroleum applications. The recent advancements in microfluidic devices for petroleum applications have the potential to improve oil recovery efficiency, reduce costs, and provide valuable insights into fluid behaviour and reservoir characterization. This paper aims to provide a comprehensive overview of microfluidic devices, their materials, and their applications in the petroleum industry. The first section of the paper focuses on describing the materials used in microfluidic devices specifically tailored for energy sector applications. In the second section, the paper highlights relevant applications and discoveries in petroleum research, showcasing the innovative techniques and special features enabled by microfluidic devices. These applications include but are not limited to asphaltenes characterization, enhanced oil recovery (EOR), and water treatment. The versatility and customization of microfluidic devices have allowed researchers to accurately represent fractures, ensure chemical conformance, simulate high pressure–high temperature conditions and reservoir heterogeneity, and study geochemical interaction. Additionally, molecular tagging and machine learning techniques have been employed for image analysis, further enhancing the capabilities of microfluidic devices. Throughout the paper, the advantages and disadvantages of implementing microfluidic devices and utilizing specific materials are thoroughly discussed. This analysis provides valuable insights into the challenges and potential limitations associated with this technology. To conclude, the paper offers suggestions, ideas, and highlights for future research paths, pointing toward promising directions for further exploration in this field.

Self-Templating Copolymerization to Produce Robust Conductive Nanocoatings Based on Conjugated Polymer Brushes with Implementable Memristive Characteristics.

An effective synthesis of conductive polymer brushes, i.e., self-templating surface-initiated copolymerization (ST-SICP), is developed. It proceeds through copolymerization of pendant thiophene groups in the precursor multimonomer poly(3-methylthienyl methacrylate) (PMTM) brushes with free 3-methylthiophene (3MT) monomers leading to PMTM-co-P3MT brushes. This approach leads to improved conformational freedom of generated conjugated poly(thiophene)-based chains and their higher share in the brushes with respect to conjugation of pendant thiophene groups only. As a result, best performing conjugated PMTM-co-P3MT brushes demonstrate high ohmic conductivity in both out-of-plane and in-plane direction. Furthermore, thanks to the covalent anchoring as well as intra- and intermolecular connections, highly stable and mechanically robust nanocoatings are produced which can survive mechanical cleaning and long-term storage under ambient conditions. Grafting of ionic poly(sodium 4-styrenesulfonate) (PSSNa) in between PMTM-co-P3MT chains brings new properties to such binary mixed brushes that can operate as thin-film memristive coating with switchable conductance. It is worth mentioning that the crucial synthetic steps, i.e., grafting of precursor PMTM brushes by surface-initiated organocatalyzed atom transfer radical polymerization (SI-O-ATRP) and PSSNa chains by surface-initiated photoiniferter-mediated polymerization (SI-PIMP) are conducted under ambient conditions using only microliter volumes of reagents providing methodology that can be considered for use beyond the laboratory scale.

Assessment of Eutectic Solvent-Based Liquid-Liquid Microextraction to Determine Ponceau-4R in Various Beverage Samples

A sensitive, rapid, efficient, inexpensive, and easy-to-use vortex-assisted eutectic solvent microextraction process was extended to quantify Ponceau-4R (PN4R) in beverage samples followed by spectrophotometric detection. Here, a green solvent consisting of tetrabutylammonium bromide: n-octanol at a ratio of 1:3 was tested in the PN4R microextraction process. Also, different parameters affecting PN4R quantification through deep eutectic solvent in the microextraction model, including microliter volumes of extraction solvent, concentration of salt, extraction time, and pH were studied using multivariate procedures. Using this model, the maximum response was achieved with a eutectic solvent volume of 262 μL, extraction time of 5.3 min, pH 6.7, and 0.9% salt with Desirability = 1. The linear range was determined in optimum conditions to be from 15 to 1200 μg L−1. The enrichment factor and limit of detection were achieved to be 50-fold and 4.5 μg L−1, respectively. The limit of quantitation was 15 μg L−1. To monitor PN4R, this model has been used in fruit juice samples with favorable recoveries in the range of 97.8%–101%.

CuBr-mediated surface-initiated controlled radical polymerization in air

Herein, we present a straightforward CuBr-mediated surface-initiated controlled radical polymerization (SI-CRP) method for fabricating polymer brushes using microliter volumes of reaction solution in air and at room temperature. The key...

Steady state microdialysis of microliter volumes of body fluids for monitoring of amino acids by capillary electrophoresis with contactless conductivity detection

BackgroundThe availability of dialysis membranes in the form of hollow fibres with diameters compatible with the fused silica capillaries used in capillary electrophoresis is very limited. However, haemodialysis bicarbonate cartridges commonly used in human medicine containing polysulfone hollow fibres are available on the market and are used for the fabrication of coaxial microdialysis probes. The miniature probe design ensures that steady-state conditions are achieved during microdialysis of minimal volumes of body fluids. ResultsA coaxial microdialysis probe with a length of 5 cm and an inner diameter of 200 μm is used for microdialysis of 10 μL of body fluid collected into a sampling fused silica capillary with an inner diameter 430 μm. Microdialysis is performed into 0.01 M HCl as a perfusate at stopped flow and 2 μL of the resulting microdialysate are subjected to analysis by capillary electrophoresis with contactless conductivity detection. Microdialysis pre-treatment is verified by analysis of 11 common amino acids at a 100 μM concentration level, resulting in recoveries of 98.3–102.5%. The electrophoretic separation of amino acids is performed in 8.5 M acetic acid at pH 1.37 as a background electrolyte with analysis time up to 4.5 min and LOD in the range of 0.12–0.28 μM. The reproducibility of the developed technique determined for the peak area ranges from 1.2 to 4.5%. Applicability is tested in the quantification of valine and leucine in plasma during fasting and subsequent reconvalescence. SignificanceThe fabrication of a coaxial microdialysis probe for the laboratory preparation of microliter volumes of various types of clinical samples is described, which is coupled off-line with capillary electrophoretic monitoring of amino acids in 2 μL volumes of microdialysate. The developed methodology is suitable for quantification of 20 amino acids in whole human blood, plasma, tears and has potential for analysis of dry blood spots captured on hollow fibre.

Quantifying picomoles of analyte from less than 100 live bacteria: A novel method with a buffering hydrogel as an electrochemical cell

Microenvironmental changes in the chemical surrounding of bacterial cells might have a profound impact on the ecology of biofilms. However, quantifying total amount of picomoles of analyte from a miniscule number of bacteria is an analytical challenge. Here we provide a novel microliter volume hydrogel based electrochemical cell platform suitable of coulometrically measuring hydrogen peroxide (H2O2) produced by less than 100 cells of Streptococcus sanguinis, a relevant member of the healthy oral microbiome. A morpholine moiety was incorporated into the polymer structure of the hydrogel to create a controlled microenvironment at biological pH. We calculated the buffering capacity of this hydrogel as 0.257 ± 0.135 molHNO3molMEA×ΔpHover the pH range of 7.2–6.2 by using a novel method designed for buffering hydrogels. The H2O2 sensors coated in microliter volume of buffering hydrogel showed no change in sensitivity within the pH range of 7.0–3.0, allowing for H2O2 measurements of S. sanguinis independent of any acid they produce. The novel platform was able to measure down to 22.7 ± 3.5 pmol H2O2 produced by less than 100 bacterial cells, which would otherwise not be attainable in large solution-based assays. These findings indicate that this is a suitable platform for quantifying metabolites from sub-milligram biological samples and may even be suitable for direct analysis of raw biofilms samples with little to no sample pretreatment.

Evaluating Moisture Migration in Schirmer Test Strips: Exploring Brand-Specific Variations and Introducing Calibration and Conversion Methods.

Schirmer test results are widely used for ocular surface disease assessment, but Schirmer strips are not standardized. We compare the characteristics and tear volume with millimeter moisture migration in different brands of Schirmer strips and introduce methods for volume-based, brand-independent calibration. Physical parameters of Haag-Streit, EagleVision, TearFlo, Contacare, and MIPL/A6 Schirmer strip brands were compared. Schirmer strip millimeter moisture migration distances were assessed 5 minutes after application of incremental microliter volumes of human tears. Linear regression analysis of data points from each Schirmer strip brand was performed, and the root-mean-square deviation of data points to the best-fit linear regression was calculated. Calibration correction was performed by converting migration distance to the corresponding tear volume. A reference table and calibration method formulas were created. Schirmer strips differed in design, shape, and manufacturing precision. Strip width, weight, and length were different between the 5 brands ( P < 0.05). A wide range of Schirmer strip moisture migration values for identical tear volumes was observed among brands. Statistical measurement resulted in a root-mean-square deviation of 2.9 mm for all data points from all brands. Millimeter to volume and weight to volume-based calibration correction methods resulted in a 2.2- and 3.1-fold measurement error reduction, respectively. Our findings highlight the lack of standardization among different brands of Schirmer strips, raising concerns about potential sources of unintentional measurement errors. We propose volume-based Schirmer strip calibration methods and conversion of millimeter to microliter results to achieve brand-independent results and improve Schirmer test accuracy.

Real-time surface functionalization of a nanophotonic sensor for liquid biopsy

Today, the search for disease biomarkers and techniques for their detection is one of the most important focuses in modern healthcare. Extracellular vesicles (EVs) are known to be related to the pathogenesis of various illnesses, such as cancer, neurodegenerative disease, and cardiovascular disease. Specific EV detection and potential control of their amount in biological fluids can provide a promising therapeutic strategy that involves reduction in EV production and circulation to normal levels to prevent disease progression. To provide a foundation for such research and development, we report the application of photonic integrated circuits in the form of a Mach–Zehnder interferometer coupled with microfluidics for monitoring each step of a covalent linkage between receptors and silicon nitride. We show that such a biosensor can be used for biological marker quantification, such as EVs containing a specific membrane protein HER2. The developed platform provides real-time results by using microliter volumes of the test sample. This research can be used as a first step toward creation of a laboratory on a chip for the precise control of coating in terms of chemical applications and monitoring the effectiveness of the chosen treatment for medical applications.

Vibration-enhanced disposable electroanalytical platform for selective analysis of tryptophan in fruits based on molecular imprinting

Although electrochemical detection based on molecular imprinting polymers (MIP) could dramatically improve the selectivity, the procedure is time-consuming because of the essential incubation step. In addition, current MIP electrochemical detections were not suitable for analysis of microliter-level sample solutions, limiting their applications for real samples. This investigation aims at applying vibration to enhance efficiency of MIP electrochemical detection of 20 μL sample solutions. MIP analysis of Tryptophan (Trp) was used as the model with disposable MIP electrodes prepared by electrochemical polymerization of o-phenylenediamine on carbon ink coated on stainless steel sheets. The MIP electrode was integrated in a 3D-printed analytical device for vibration-enhanced electrochemical detection of Trp. Our results showed that this vibration-enhanced strategy could significantly increase electrochemical responses of Trp at the same incubation time. Such improvement might be attributed to the enhanced mass transfer at the surface of the working electrode brought by vibration. It needs to be emphasized that this strategy is suitable for analysis of sample solutions with the volume of microliters, which is superior to normal stirring in MIP electrochemical detection. Our approach could be successfully utilized for differentiation of Trp in different fruits, opening more opportunities for MIP electrochemical detection of real samples. The enhanced efficiency by vibration could pave foundation for extensive practical MIP detection of sample solutions at the level of microliters.

Simple Self-Powered Sensor for the Detection of D2O and Other Isotopologues of Liquid Water.

Distinguishing between heavy water and regular water has been a continuing challenge since these isotopologues of water have very similar physical and chemical properties. We report the development and evaluation of a simple, inexpensive sensor capable of detecting liquid D2O and other isotopologues of liquid water through the measurement of electrical signals generated from a nanoporous alumina film. This electrical output, consisting of a sharp voltage pulse followed by a separate broad voltage pulse, is present during the application of microliter volumes of liquid. The amplitude and temporal characteristics of these pulses have been combined to enable four diagnostic parameters for sensing D2O and H218O. The sensing mechanism is based on different modification effects on the alumina surface by H2O and D2O, spatially localized variations in the surface potential of alumina induced by isotopically substituted water molecules, combined with the effect of isotopic composition on charge transfer. As a proof-of-concept demonstration, a sensing system has been developed that provides real-time detection of liquid D2O in a stand-alone system.

Surface-Initiated Zerovalent Metal-Mediated Controlled Radical Polymerization (SI-Mt0CRP) for Brush Engineering.

ConspectusThe surface-tethered polymer brush has become a powerful approach to tailoring the chemical and physical properties of surfaces and interfaces and revealed broad application prospects in widespread fields such as self-cleaning, surface lubrication, and antibiofouling. Access to these diverse functional polymer brushes is highly dependent on versatile and powerful surface-initiated controlled radical polymerization (SI-CRP) strategies. However, conventional SI-CRP typically requires oxygen exclusion, large amounts of catalysts and monomer solution, and a long reaction time, making it time-consuming and sophisticated. When using a two-plate system consisting of an initiator-bearing substrate and a metal plate, we and our collaborators introduced surface-initiated zerovalent metal-mediated controlled radical polymerization (SI-Mt0CRP). In the SI-Mt0CRP setup, a metal(0) plate (Cu, Fe, Zn, or Sn) is placed proximately to an initiator-functionalized substrate and forms a confined polymerization system which considerably simplifies the synthesis of a wide range of polymer brushes with high grafting densities over large areas (up to the meter scale).In comparison to classical SI-ATRP (catalyzed by metal salts), SI-Mt0CRP demonstrates oxygen tolerance, high controllability, good retention of chain-end functionality, and facile recyclability of the metal catalysts (i.e., metal foil/plate). Taking advantage of the confined geometry of the SI-Mt0CRP setup, polymer brushes with various conformations and architectures are easily accessible while consuming only microliter volumes of monomer solution and without complicated operations under ambient conditions. Owing to these attractive characteristics, SI-Mt0CRP has become a versatile technique for functionalizing materials for targeted applications, ranging from the areas of surface science to materials science and nanotechnology.In this Account, we summarize the recent advances of SI-Mt0CRP catalyzed by zerovalent metals (e.g., Cu, Fe, Zn, and Sn) and highlight the intrinsic advantages of the featured experimental setup, compared with the "classical" SI-CRP in which metal salt, powder, or wire is applied. We further discuss the synthetic features and proposed mechanism of SI-Mt0CRP while emphasizing the various external technologies' (including "on water" reaction, galvanic replacement, lithography, and capillary microfluidic) integrated polymerization systems. We also describe structural polymer brushes, including block copolymers, patterned and gradient structures, and arrayed and binary polymer brushes. Finally, we introduce the diverse polymer brushes that have been prepared using these techniques, with a focus on targeted and emerging applications. We anticipate that the discussion presented in this Account will promote a better understanding of the SI-Mt0CRP technique and advance the future development of practical surface brushing.