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Helical alignments within the heart’s musculature have been speculated to be important in achieving physiological pumping efficiencies. Testing this possibility is difficult, however, because it is challenging to reproduce the fine spatial features and complex structures of the heart’s musculature using current techniques. Here we report focused rotary jet spinning (FRJS), an additive manufacturing approach that enables rapid fabrication of micro/nanofiber scaffolds with programmable alignments in three-dimensional geometries. Seeding these scaffolds with cardiomyocytes enabled the biofabrication of tissue-engineered ventricles, with helically aligned models displaying more uniform deformations, greater apical shortening, and increased ejection fractions compared with circumferential alignments. The ability of FRJS to control fiber arrangements in three dimensions offers a streamlined approach to fabricating tissues and organs, with this work demonstrating how helical architectures contribute to cardiac performance.

Previously, we identified that GJA1-20k, an internally translated isoform of Connexin 43, mediates an actin-dependent protective form of mitochondrial fission (Shimura, Nuebel et al. 2021). We found that when GJA1-20k is present, bands of actin surround mitochondria at locations enriched with GJA1-20k, inducing mitochondrial fission which generates less oxygen free radicals, protecting hearts subjected to ischemia-reperfusion injury. Here, we report that GJA1-20k is a direct actin binding protein and thereby identify the mechanism by which GJA1-20k is able to recruit and stabilize actin filaments around the mitochondria. Surprisingly, GJA1-20k functions as a canonical actin capping protein, producing both truncated actin puncta and stabilized actin filaments. GJA1-20k contains an RPEL-like actin binding motif, and we confirm with both computational modeling and biochemistry, that this domain is crucial for actin capping. The actin capping functionality of GJA1-20k adds GJA1-20k to the family of proteins that regulate actin dynamics. As a stress responsive protein, GJA1-20k can help explain cytoskeletal dependent responses to cellular stress, from delivery of channels to affecting mitochondrial size and function.

For more than fifty years, it has been hypothesized that the helical alignment of the heart gives rise to its mechanical function. Testing this hypothesis in an engineered environment is difficult, as the fine spatial features and complex three-dimensional (3D) structures of the cardiac musculature are challenging to reproduce using current biofabrication techniques. Addressing this, here we report a new form of additive textile manufacturing, Focused Rotary Jet Spinning (FRJS). FRJS allows for the rapid manufacturing of micro/nanofibers with controlled alignments. Using this method, we manufacture 3D models of the left ventricle, showing that helically aligned scaffolds display increased strain uniformity, axial shortening, cardiac output, and ejection fractions as compared to circumferential models. We then demonstrate how FRJS can enable the assembly of a full-sized model of the human heart’s musculature. This work experimentally confirms that ventricular alignment plays a critical role in ensuring healthy cardiac performance.

Cardiac arrhythmias are an important cause of sudden cardiac death-a devastating manifestation of many underlying causes, such as heart failure and ischemic heart disease leading to ventricular tachyarrhythmias and ventricular fibrillation, and atrial fibrillation causing cerebral embolism. Cardiac electrical propagation is a main factor in the initiation and maintenance of cardiac arrhythmias. In the heart, gap junctions are the basic unit at the cellular level that host intercellular low-resistance channels for the diffusion of ions and small regulatory molecules. The dual voltage clamp technique enabled the direct measurement of electrical conductance between cells and recording of single gap junction channel openings. The rapid turnover of gap junction channels at the intercalated disk implicates a highly dynamic process of trafficking and internalization of gap junction connexons. Recently, non-canonical roles of gap junction proteins have been discovered in mitochondria function, cytoskeletal organization, trafficking, and cardiac rescue. At the tissue level, we explain the concepts of linear propagation and safety factor based on the model of linear cellular structure. Working myocardium is adequately represented as a discontinuous cellular network characterized by cellular anisotropy and connective tissue heterogeneity. Electrical propagation in discontinuous cellular networks reflects an interplay of three main factors: cell-to-cell electrical coupling, flow of electrical charge through the ion channels, and the microscopic tissue structure. This review provides a state-of-the-art update of the cardiac gap junction channels and their role in cardiac electrical impulse propagation and highlights a combined approach of genetics, cell biology, and physics in modern cardiac electrophysiology.

The development of magnetically-powered microswimmers that mimic the swimming mechanisms of microorganisms are important for lab-on-a-chip devices, robotics, and next-generation minimally-invasive surgical interventions. Governed by their design, most previously described untethered swimmers can be maneuvered only by varying the direction of applied rotational magnetic fields. This constraint makes even state-of-the-art swimmers incapable of reversing their direction of motion without a prior change in the direction of field rotation, which limits their autonomy and ability to adapt to their environments. Also, owing to constant magnetization profiles, swarms of magnetic swimmers respond in the same manner, which limits multi-agent control only to parallel formations. Herein, we present a new class of microswimmers which are capable of reversing their direction of swimming without requiring a reversal in direction of field rotation. These swimmers exploit heterogeneity in their design and composition to exhibit reversible bidirectional motion determined by the field precession angle. Thus, the precession angle can be used as an independent control input for bi-directional swimming. Design variability is explored in the systematic study of two swimmer designs with different construction. Two different precession angles are observed for motion reversal, which is exploited to demonstrate independent control of the two swimmer designs.

Single cell manipulation is important in biosensing, biorobotics, and quantitative cell analysis. Although microbeads, droplets, and microrobots have been developed previously, it is still challenging to simultaneously excise, capture, and manipulate single cells in a biocompatible manner. Here, we describe untethered single cell grippers, that can be remotely guided and actuated on-demand to actively capture or excise individual or few cells. We describe a novel molding method to micropattern a thermally responsive wax layer for biocompatible motion actuation. The multi-fingered grippers derive their energy from the triggered release of residual differential stress in bilayer hinges composed of silicon oxides. A magnetic layer enables remote guidance through narrow conduits and fixed tissues sections ex vivo. Our results provide an important advance in high-throughput single cell scale biopsy tools important to lab-on-a-chip devices, microrobotics, and minimally invasive surgery.

Biofabricated mass-producible arteries containing layered and aligned cells and matrix exhibit enhanced cellular function., Changes in structure and function of small muscular arteries play a major role in the pathophysiology of pulmonary hypertension, a burgeoning public health challenge. Improved anatomically mimetic in vitro models of these microvessels are urgently needed because nonhuman vessels and previous models do not accurately recapitulate the microenvironment and architecture of the human microvascular wall. Here, we describe parallel biofabrication of photopatterned self-rolled biomimetic pulmonary arterial microvessels of tunable size and infrastructure. These microvessels feature anatomically accurate layering and patterning of aligned human smooth muscle cells, extracellular matrix, and endothelial cells and exhibit notable increases in endothelial longevity and nitric oxide production. Computational image processing yielded high-resolution 3D perspectives of cells and proteins. Our studies provide a new paradigm for engineering multicellular tissues with precise 3D spatial positioning of multiple constituents in planar moieties, providing a biomimetic platform for investigation of microvascular pathobiology in human disease.

Silica nanowires (NWs) with tailored hydrophobicity are synthesized by capping different length of alkyl groups on surface via a one-pot anisotropic sol-gel growth approach. Lipase from Burkholderia Cepacia (BCL) is successfully immobilized onto the silica NWs via hydrophobic interaction. The specific activity of the immobilized BCL increases with the increasing length of the capping alkyl groups and surface hydrophobicity of the NWs. BCL immobilized onto the octadecyl groups-capped silica NWs displays the highest specific catalytic activity, which is also notably higher than that of BCL immobilized on octadecyl groups-modified mesoporous silicate. The superior performance can be ascribed to the combination of the interfacial activation of lipases induced by capped-octadecyl groups on the NWs and the improved mass transfer efficiency of reactants around the one-dimensional silica NWs. The BCL-loaded NWs are further used as "building blocks" to assemble filter paper-like biocatalytic membrane via vacuum-assisted filtration method. The free-standing biocatalytic membrane can be operated in a continuous mode to avoid the separation of catalyst from reaction products. This work provides new opportunity in enzyme immobilization and biocatalytic membrane preparation through using discrete silica NWs as supports and building blocks.

While there is a growing need for soft and 3D cell interfacing, present‐day microelectrode arrays are largely rigid and planar. In article number https://doi.org/10.1002/advs.201700731, Dries Braeken, David H. Gracias, and co‐workers realize flexible multielectrode shells that can wrap around cardiomyocytes, allowing parallel readout of all cardinal points of the cell with higher signal‐to‐noise ratios compared to planar electrodes.

Given the heterogeneous nature of cultures, tumors, and tissues, the ability to capture, contain, and analyze single cells is important for genomics, proteomics, diagnostics, therapeutics, and surgery. Moreover, for surgical applications in small conduits in the body such as in the cardiovascular system, there is a need for tiny tools that approach the size of the single red blood cells that traverse the blood vessels and capillaries. We describe the fabrication of arrayed or untethered single cell grippers composed of biocompatible and bioresorbable silicon monoxide and silicon dioxide. The energy required to actuate these grippers is derived from the release of residual stress in 3–27 nm thick films, did not require any wires, tethers, or batteries, and resulted in folding angles over 100° with folding radii as small as 765 nm. We developed and applied a finite element model to predict these folding angles. Finally, we demonstrated the capture of live mouse fibroblast cells in an array of grippers and individual red blood cells in untethered grippers which could be released from the substrate to illustrate the potential utility for in vivo operations.

Supported Pd nanoparticles (PdNPs) were modified with various alkalic salts by incipient wetness impregnation method. The effect of the salts on the catalytic activity and selectivity behavior of Pd catalysts for the racemization of (S)-1-phenylethylamine was investigated. The presence of alkalic salts can greatly enhance the selectivity of Pd catalysts, without significantly decreasing the catalytic activity. This modification method is suitable for PdNPs supported on various supports, such as micro/mesoporous silica and activated carbon. Combined with the immobilized lipases (Novozyme 435), this catalyst system can efficiently catalyze the dynamic kinetic resolution (DKR) of 1-phenylethylamine with yield and enantioselectivity up to 97% and 99%, respectively.

The effects of a kosmotropic phosphate buffer (PB) or sodium sulfate (SS) on the enzymatic activity of crude Pseudomonas cepacia lipase (PCL) in organic media were explored. Previously, it was believed that SS acts as an effective enzyme activator, and PB was only used to adjust the solution pH. The present work showed PB-induced activation of PCL in the transesterification activity, where an increase of nearly 10-fold was achieved by carefully controlling the lyophilization condition. This activation, which gave about one-half of the native catalytic efficiency of PCL in aqueous media, was even more effective than the SS-induced activation. Thermogravimetric analysis of PCL preparations showed that different local environments surrounded PCL due to the presence of PB or SS. The local polarity of PCL preparations suspended in n-hexane was investigated by fluorescence spectroscopy using 2-(4'-amino-2'-hydroxy phenyl)benzoxazole as the probe. SS-incorporated PCL showed a much stronger local polarity than PB-incorporated and salt-free PCL. A correlation was found between the transesterification activity and local polarity of the enzyme preparation as a function of salt content The data confirmed that the salt-induced activation of PCL in organic media can be attributed in part to the polar environment constituted by the salt-bonded water surrounding the PCL. (c) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Reported is a new shell-based spectroscopic platform, named mechanical trap surface-enhanced Raman spectroscopy (MTSERS), for simultaneous capture, profiling, and 3D microscopic mapping of the intrinsic molecular signatures on the membrane of single live cells. By leveraging the functionalization of the inner surfaces of the MTs with plasmonic gold nanostars, and conformal contact of the cell membrane, MTSERS permits excellent signal enhancement, reliably detects molecular signatures, and allows non-perturbative, multiplex 3D surface imaging of analytes, such as lipids and proteins on the surface of single cells. The demonstrated ability underscores the potential of MTSERS to perform 3D spectroscopic microimaging and to furnish biologically interpretable, quantitative, and dynamic molecular maps in live cell populations.

Macromolecular crowding is an ubiquitous phenomenon in living cells that significantly affects the function of enzymes in vivo. However, this effect has not been paid much attention in the research of the immobilization of enzymes onto mesoporous silica. Herein, we report the combined effects of macromolecular crowding and surface hydrophobicity on the performance of an immobilized enzyme by accommodating lipase molecules into a series of mesoporous silicas with different amounts of inert poly(methacrylate) (PMA) covalently anchored inside the nanopores. The incorporation of the PMA polymer into the nanopores of mesoporous silica enables the fabrication of a crowded and hydrophobic microenvironment for the immobilized enzyme and the variation in polymer content facilitates an adjustment of the degree of crowding and surface properties of this environment. Based on this system, the catalytic features of immobilized lipase were investigated as a function of polymer content in nanopores and the results indicated that the catalytic efficiency, thermostability, and reusability of immobilized lipase could all be improved by taking advantage of the macromolecular crowding effect and surface hydrophobicity. These findings provide insight into the possible functions of the macromolecular crowding effect, which should be considered and integrated into the fabrication of suitable mesoporous silicas to improve enzyme immobilization.

highlights " The kinetics of dehydrochlorination of dichloropropanol is studied in a microreactor. " 2,3-Dichloro-1-propanol is much less reactive than 1,3-dichloro-2-propanol. " Rate constants are determined in the temperature range of 50-80 C. " The kinetics is found to be first order to (OH � ) and second order to (DCP). abstract The reaction kinetics of dehydrochlorination of dichloropropanol (including 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol) is investigated with a microchemical system, which is constructed with a micromixer, a micro-tube and a microneutralizer. The reaction starts up by mixing dichloropropanol solution and sodium hydroxide solution in the micromixer, proceeds in the following micro-tube for a residence time strictly controlled to several seconds, and quenches in the microneutralizer. The results show that 2,3-dichloro-1-propanol is much less reactive than 1,3-dichloro-2-propanol. Rate constants of the dehydrochlorination reaction (2,3-dichloro-1-propanol) are determined in the temperature range of 50-80 C. The reaction kinetics is found to be first order with respect to hydroxyl ion concentration and second order to dichloropropanol concentration. The activation energy is 150 (±10) kJ mol � 1 and the pre

It is extremely challenging to enable nanoscale patterning in three dimensional (3D) curved geometries using conventional nanolithographic approaches. In this paper, we describe a highly parallel approach that combines nanoimprint lithography (NIL) and thin film bilayer strain engineering to spontaneously roll-up nanopatterned membranes into curved geometries. Specifically, we first patterned a silicon nitride (Si 3 N 4 ) / silicon (Si) bilayer using nanoimprint lithography followed by plasma etching to create well defined pores. The diameter of the pores was further reduced by physical vapor deposition of platinum to sizes as small as 50 nm. After patterning, the bilayers were released from the substrate by etching an underlying SiO 2 sacrificial layer. Based on the high deposition stress values for low pressure chemical vapor deposition (LPCVD) deposited Si 3 N 4 and Si, we varied the thickness of the bilayer to realize rolled-up tubes with different radii of curvature; these curvature values were in good agreement with a finite element analysis model (FEM). The assembled nanoporous tubes had well defined pores along their curved interface and can be applied for drug delivery, separations and ion-sensing devices. We highlight biocompatibility of the devices by encapsulating β-TC-6 islet cells of relevance to cell encapsulation therapy for diabetes. More broadly, we believe that this approach of combining NIL with strain engineering processes could be utilized to create a range of precisely nanopatterned curved structures in a highly parallel manner.

Microelectrode arrays (MEAs) have proved to be useful tools for characterizing electrically active cells such as cardiomyocytes and neurons. While there exist a number of integrated electronic chips for recording from small populations or even single cells, they rely primarily on the interface between the cells and 2D flat electrodes. Here, an approach that utilizes residual stress‐based self‐folding to create individually addressable multielectrode interfaces that wrap around the cell in 3D and function as an electrical shell‐like recording device is described. These devices are optically transparent, allowing for simultaneous fluorescence imaging. Cell viability is maintained during and after electrode wrapping around the cel and chemicals can diffuse into and out of the self‐folding devices. It is further shown that 3D spatiotemporal recordings are possible and that the action potentials recorded from cultured neonatal rat ventricular cardiomyocytes display significantly higher signal‐to‐noise ratios in comparison with signals recorded with planar extracellular electrodes. It is anticipated that this device can provide the foundation for the development of new‐generation MEAs where dynamic electrode–cell interfacing and recording substitutes the traditional method using static electrodes.

Lipase from Pseudomonas cepacia (PCL) was successfully immobilized into siliceous mesocellular foams (MCFs) with various hydrophobic/hydrophilic surfaces. The catalytic performances of immobilized PCL were investigated using the transesterification reaction and hydrolytic reaction as model reactions. The specific activity of immobilized PCL greatly increased with enhanced surface hydrophobicity of MCFs, mainly because of lipase activation via hydrophobic interaction between alkyl groups in MCFs and the surface loop (so-called "lid") of PCL. Conformational changes of immobilized PCL were further investigated using time-resolved fluorescence spectroscopy with Trp as an intrinsic probe. When the immobilized PCL was suspended in phosphate buffer, short-lived τ(1) shortened and the fractional contribution of τ(1) significantly increased with the increasing level of surface hydrophobicity of MCFs. These results revealed that Trp(s) of the immobilized PCL were surrounded by a hydrophilic microenvironment because of the fact that the opened "lid" permitted the diffusion of water to the active site cleft. However, for the immobilized PCL suspended in n-hexane, long-lived τ(3) increased with the increase of surface hydrophobicity of MCFs. The reduced interaction between Trp(s) and the surrounding protein matrix was due to intercalation of n-hexane into the active site cleft when the lipase was in open conformation. The above results demonstrated that PCL immobilized into MCF with hydrophobic surfaces were in an activated open conformation.

In order to incorporate the extraordinary intrinsic thermal, electrical, mechanical, and optical properties of graphene with three dimensional (3D) flexible substrates, we introduce a solvent-driven self-folding approach using graphene-polymer bilayers. A polymer (SU-8) film was spin coated atop chemically vapor deposited graphene films on wafer substrates and graphene-polymer bilayers were patterned with or without metal electrodes using photolithography, thin film deposition, and etching. After patterning, the bilayers were released from the substrates and they self-folded to form fully integrated, curved, and folded structures. In contrast to planar graphene sensors on rigid substrates, we assembled curved and folded sensors that are flexible and they feature smaller form factors due to their 3D geometry and large surface areas due to their multiple rolled architectures. We believe that this approach could be used to assemble a range of high performance 3D electronic and optical devices of relevance to sensing, diagnostics, wearables, and energy harvesting.

The crowded and hydrophobic microenvironment was created for immobilized enzymes via the thermally-initiated shrinkage of PNIPAM polymers anchored in the nanopores of mesoporous silica. This extraordinary microenvironment can greatly enhance both the catalytic efficiency and thermostability of lipases, which provides a new approach for fabricating robust heterogeneous biocatalysts.