Correction: Quantitative assessment of cardiomyocyte mechanobiology through high-throughput cantilever-based functional well plate systems.

Correction for 'Quantitative assessment of cardiomyocyte mechanobiology through high-throughput cantilever-based functional well plate systems' by Jongyun Kim et al., Analyst, 2023, 148, 5133-5143, https://doi.org/10.1039/D3AN01286G.

Implantable Self-Reporting Stents for Detecting In-Stent Restenosis and Cardiac Functional Dynamics.

Despite the increasing number of stents implanted each year worldwide, patients remain at high risk for developing in-stent restenosis. Various self-reporting stents have been developed to address this challenge, but their practical utility has been limited by low sensitivity and limited data collection. Herein, we propose a next-generation self-reporting stent that can monitor blood pressure and blood flow inside the blood arteries. This proposed self-reporting stent utilizes a larger inductor coil encapsulated on the entire surface of the stent strut, resulting in a 2-fold increase in the sensing resolution and coupling distance between the sensor and external antenna. The dual-pressure sensors enable the detection of blood flow in situ. The feasibility of the proposed self-reporting stent is successfully demonstrated through in vivo analysis in rats, verifying its biocompatibility and multifunctional utilities. This multifunctional self-reporting stent has the potential to greatly improve cardiovascular care by providing real-time monitoring and unprecedented insight into the functional dynamics of the heart.

Correction: Enhanced cardiomyocyte structural and functional anisotropy through synergetic combination of topographical, conductive, and mechanical stimulation.

Correction for 'Enhanced cardiomyocyte structural and functional anisotropy through synergetic combination of topographical, conductive, and mechanical stimulation' by Jongyun Kim et al., Lab Chip, 2023, 23, 4540-4551, https://doi.org/10.1039/D3LC00451A.

Enhanced cardiomyocyte structural and functional anisotropy through synergetic combination of topographical, conductive, and mechanical stimulation.

Drug-induced cardiotoxicity, a significant concern in the pharmaceutical industry, often results in the withdrawal of drugs from the market. The main cause of drug-induced cardiotoxicity is the use of immature cardiomyocytes during in vitro drug screening procedures. Over time, several methods such as topographical, conductive, and mechanical stimulation have been proposed to enhance both maturation and contractile properties of these cardiomyocytes. However, the synergistic effects of integrating topographical, conductive, and mechanical stimulation for cardiomyocyte maturation remain underexplored and poorly understood. To address this limitation, herein, we propose a grooved polydimethylsiloxane (PDMS) membrane embedded with silver nanowires (AgNWs-E-PDMS). The proposed AgNWs-E-PDMS membrane enhances the maturation of cardiomyocytes and provides a more accurate evaluation of drug-induced cardiotoxicity. When subjected to 10% tensile stress on the AgNWs-E-PDMS membrane, cardiomyocytes displayed substantial enhancements. Specifically, the contraction force, sarcomere length, and connexin-43 (Cx43) expression are increased by 2.0-, 1.5-, and 2.4-times, respectively, compared to the control state. The practical feasibility of the proposed device as a drug screening platform is demonstrated by assessing the adverse effects of lidocaine on cardiomyocytes. The contraction force and beat rate of lidocaine treated cardiomyocytes cultured on the AgNWs-E-PDMS membrane under mechanical stimulation decreased to 0.9 and 0.64 times their initial values respectively, compared to 0.6 and 0.51 times in the control state. These less pronounced changes in the contraction force and beat rate signify the superior drug response in the cardiomyocytes, a result of their enhanced maturation and growth on the AgNWs-E-PDMS membrane combined with mechanical stimulation.

Quantitative assessment of cardiomyocyte mechanobiology through high-throughput cantilever-based functional well plate systems.

Proper regulation of the in vitro cell culture environment is essential for disease modelling and drug toxicity screening. The main limitation of well plates used for cell culture is that they cannot accurately maintain energy sources and compounds needed during cell growth. Herein, to understand the importance of perfusion in cardiomyocyte culture, changes in contractile force and heart rate during cardiomyocyte growth are systematically investigated, and the results are compared with those of a perfusion-free system. The proposed perfusion system consists of a Peltier refrigerator, a peristaltic pump, and a functional well plate. A functional well plate with 12 wells is made through injection moulding, with two tubes integrated in the cover for each well to continuously circulate the culture medium. The contractile force of cardiomyocytes growing on the cantilever surface is analysed through changes in cantilever displacement. The maturation of cardiomyocytes is evaluated through fluorescence staining and western blot; cardiomyocytes cultured in the perfusion system show greater maturity than those cultured in a manually replaced culture medium. The pH of the culture medium manually replaced at intervals of 3 days decreases to 6.8, resulting in an abnormal heartbeat, while cardiomyocytes cultured in the perfusion system maintained at pH 7.4 show improved contractility and a uniform heart rate. Two well-known ion channel blockers, verapamil and quinidine, are used to measure changes in the contractile force of cardiomyocytes from the two systems. Cardiomyocytes in the perfusion system show greater stability during drug toxicity screening, proving that the perfusion system provides a better environment for cell growth.

Stress induced self-rollable smart-stent-based U-health platform for in-stent restenosis monitoring.

To date, several smart stents have been proposed to continuously detect biological cues, which is essential for tracking patients' critical vital signs and therapy. However, the proposed smart stent fabrication techniques rely on conventional laser micro-cutting or 3D printing technologies. The sensors are then integrated into the stent structure using an adhesive, conductive epoxy, or laser micro-welding process. The sensor packaging method using additional fabrication processes can cause electrical noise, and there is a possibility of sensor detachment from the sent structure after implantation, which may pose a significant risk to patients. Herein, we are demonstrating for the first time a single-step fabrication method to develop a smart stent with an integrated sensor for detecting in-stent restenosis and assessing the functional dynamics of the heart. The smart stent is fabricated using a microelectromechanical system (MEMS)-based micromachining technology. The proposed smart stent can detect biological cues without additional power and wirelessly transmit the signal to the network analyzer. The cytocompatibility of the smart stent is confirmed through a cytotoxicity test by monitoring the cell growth, proliferation, and viability of the cultured cardiomyocytes. The capacitance of the smart stent exhibits an excellent linear relationship with the applied pressure. The exceptional sensitivity of the pressure sensor enabled the proposed smart stent to detect biological cues during in vivo analysis. The preliminary findings confirmed the proposed smart stent's higher level of structural integrity, durability and repeatability. Finally, the practical feasibility of the smart stent is demonstrated by monitoring diastole and systole at various beat rates using a phantom. The results of the phantom study showed a similar pattern to the human model, indicating the potential use of the proposed multifunctional smart stent for real-time applications.

MEA-integrated cantilever platform for comparison of real-time change in electrophysiology and contractility of cardiomyocytes to drugs.

Drug-induced cardiotoxicity is a potentially severe side effect that can alter the contractility and electrophysiology of the cardiomyocytes. Cardiotoxicity is generally assessed through animal models using conventional drug screening platforms. Despite significant developments in drug screening platforms, the difficulty in measuring electrophysiology and contractile profile together affects the investigation of cardiotoxicity in potential drugs. Some drugs can prove to be more toxic to contractility than electrophysiology, which demands the need for a reliable, dual, and simultaneous drug screening platform. Herein, we propose the microelectrode array integrated SU-8 cantilever for dual and simultaneous measurement of electrophysiology and contractility of cardiomyocytes. The SU-8 cantilever is integrated with microelectrode array (C-MEA) using conventional photolithographic techniques. Drug tests are conducted to verify the feasibility of the C-MEA platform using three cardiovascular drugs. Clinically recognized drugs, quinidine and verapamil, are used to activate both the hERG channel and the contractile characteristics of cardiomyocytes. The effect of ion channel blockers on the field potential duration (FPD) of the cardiomyocytes is compared with several contractility-based parameters. The contraction-relaxation duration (CRD) profile is relatively close to that of FPD in tested drugs (half-maximal (IC50) toxicities are 1.093 µM (FPD) and 1.924 µM (CRD) for quinidine and 166.2 nM (FPD) and 459.4 nM (CRD) for verapamil). Blebbistatin, a known myosin II inhibitor, primarily affects the contractile profile of cardiomyocytes but not their field potential, with no evident correlation between contractility and field potential profiles. The proposed cantilever-based mechano-electrophysiology measurements platform provides a promising and accurate means to assess cardiotoxicity.

The effect of topographical and mechanical stimulation on the structural and functional anisotropy of cardiomyocytes grown on a circular PDMS diaphragm.

Due to their immature morphology and functional immaturity, cardiomyocytes have limited use as an in vitro disease model of the native heart. Mechanical stimulation induces structural growth in cardiomyocytes in vitro by addressing the electrical-mechanical interactions between the tissues. However, current in vitro models are restricted in their capacity to replicate the milieu observed in natural myocardium. Herein, we proposed a Galinstan strain sensor integrated nanogrooved circular PDMS diaphragm to mimic the native cardiac tissues. The impact of combined topographical and mechanical stimulation on cultured cardiomyocytes at various strain areas on a circular PDMS diaphragm is studied in detail. An inverted microscope is used to image live cells and video acquisition to study the contractility of cultured cardiomyocytes. The structural changes of the cultured cardiomyocytes are investigated by its sarcomere length and connexin-43 (Cx43) expression using immunocytochemistry analysis. Cyclic strain is found to promote structural development in cultured cardiomyocytes, and diaphragms with nano-groove patterns displayed increased contractile activity and gene expression (sarcomere length ∼1.97 ± 0.03 µm and normalized Cx43-1.57) as compared to flat diaphragms (sarcomere length ∼1.82 ± 0.02 µm and normalized Cx43-1.32). The nanogrooved circular diaphragm exhibited distinct stretching mechanisms at various places, with the equibi-axial stretching regions providing the optimal structural growth and formation of natural myocardium at the diaphragm's center. Cardiomyocytes that are more mature have the potential to produce a more realistic in vitro cardiac model for disease modeling and medication development.

Crack-Based Sensor by Using the UV Curable Polyurethane-Acrylate Coated Film with V-Groove Arrays.

Over the years, several bare metal and crack-based strain sensors have been proposed for various fields of science and technology. However, due to their low gauge factor, metal-based strain sensors have limited practical applications. The crack-based strain sensor, on the other hand, demonstrated excellent sensitivity and a high gauge factor. However, the crack-based strain sensor exhibited non-linear behavior at low strains, severely limiting its real-time applications. Generally, the crack-based strain sensors are fabricated by generating cracks by bending a polymer film on which a metal layer has been deposited with a constant curvature. However, the random formation of cracks produces nonlinear behavior in the crack sensors. To overcome the limitations of the current state of the art, we propose a V-groove-based metal strain sensor for human motion monitoring and Morse code generation. The V-groove crack-based strain sensor is fabricated on polyurethane acrylate (PUA) using the modified photolithography technique. During the procedure, a V-groove pattern formed on the surface of the sensor, and a uniform crack formed over the entire surface by concentrating stress along the groove. To improve the sensitivity and selectivity of the sensor, we generated the cracks in a controlled direction. The proposed strain sensor exhibited high sensitivity and excellent fidelity compared to the other reported metal strain sensors. The gauge factor of the proposed V-groove-induced crack sensor is 10-fold higher than the gauge factor of the reported metal strain sensors. In addition, the fabricated V-groove-based strain sensor exhibited rapid response and recovery times. The practical feasibility of the proposed V-groove-induced crack-based strain sensor is demonstrated through human motion monitoring and the generation of Morse code. The proposed V-groove crack sensor can detect multiple motions in a variety of human activities and is anticipated to be utilized in several applications due to its high durability and reproducibility.

Enhancement of cardiac contractility using gold-coated SU-8 cantilevers and their application to drug-induced cardiac toxicity tests.

Herein, we propose an array of gold (Au)-coated SU-8 cantilevers with microgrooves for improved maturation of cardiomyocytes and describe its applications to drug-induced cardiac toxicity tests. Firstly, we evaluated the effect of cell culture substrates such as polydimethylsiloxane (PDMS), polyimide (PI), and SU-8 on the cardiomyocyte's maturation. Among these, the SU-8 with microgroove structures exhibits improved cardiomyocyte maturation. Further, thin layers of graphene and Au are coated on SU-8 substrates and the effects of these materials on cardiomyocyte maturation are evaluated by analyzing the expression of proteins such as alpha-actinin, Connexin 43 (Cx43), and Vinculin. While both conductive materials enhanced protein expression when compared to bare SU-8, the Au-coated SU-8 substrates demonstrated superior cardiomyocyte maturation. The cantilever structure is constructed using microgroove patterned SU-8 with and without an Au coating. The Au-coated SU-8 cantilever showed maximum displacement of 17.6 ± 0.3 µm on day 21 compared to bare SU-8 (14.2 ± 0.4 µm) owing to improved cardiomyocytes maturation. Verapamil and quinidine are used to characterize drug-induced changes in the contraction characteristics of cardiomyocytes on bare and Au-coated SU-8 cantilevers. The relative contraction forces and beat rates changed according to the calcium and sodium channel related drugs. Matured cardiomyocytes are less influenced by the drugs compared to immature cardiomyocytes and showed reliable IC50 values. These results indicate that the proposed Au-coated SU-8 cantilever array could help improve the accuracy of toxicity screening results by allowing for the use of cardiomyocytes that have been matured on the drug screening platform.

Multi-layered polymer cantilever integrated with full-bridge strain sensor to enhance force sensitivity in cardiac contractility measurement.

In this study, we developed a multi-layered functional cantilever for real-time force measurement of cardiomyocytes in cell culture media. The functional cantilever with a full-bridge circuit configuration was composed of one polydimethylsiloxane (PDMS) and two polyimide (PI) layers, forming two resistive sensors on each upper side of the two PI layers. The PI layers were chemically bonded using an oxygen plasma treatment, with a thin composite layer consisting of Cr/SiO2/PDMS. These greatly improved the force sensitivity and the long-term reliability of the integrated strain sensor operating in liquids. The nanogrooved PDMS top layer bonded on the upper PI layer was employed to further improve the growth of cardiomyocytes on the functional cantilever. The difference in resistance changes and response characteristics was confirmed by evaluating the characteristics of the multi-layered polymer cantilevers with half-bridge and full-bridge circuit configurations. We also employed the cantilever devices to measure the contraction force of cardiomyocytes for 16 days and side effects in real time in human-induced pluripotent stem cells treated with the cardiovascular drug verapamil. The sensor-integrated cantilever devices are expected to be utilized as a novel biomedical sensor for evaluating the mechanobiology of cardiomyocytes, as well as in drug screening tests.

64 PI/PDMS hybrid cantilever arrays with an integrated strain sensor for a high-throughput drug toxicity screening application.

Herein, we propose a novel biosensing platform involving an array of 64 hybrid cantilevers and integrated strain sensors to measure the real-time contractility of the drug-treated cardiomyocytes (CMs). The strain sensor is integrated on the polyimide (PI) cantilever. To improve the strain sensor reliability and construct the engineered cardiac tissue, the nanogroove-patterned polydimethylsiloxane (PDMS) encapsulation layer is bonded on the PI cantilever. The preliminary sensing characteristics demonstrate the superior structural integrity, robustness, enhanced sensitivity, and repeatability of the proposed devices. The long-term durability and biocompatibility of the PI/PDMS hybrid cantilever is verified by evaluating the cell viability and contractility. We also validate the proposed biosensing platform for cardiotoxicity measurement by applying it to two specific cardiovascular drugs: quinidine and verapamil. In response to quinidine and verapamil, the engineered CMs exhibited negative inotropic and chronotropic effects. The fabricated cantilever device successfully detected the quinidine-induced adverse effects in CMs such as early after depolarization (EADs) and Torsade de points (TdP) in real-time. The array of hybrid cantilevers with integrated strain sensors has the potential to satisfy the need for innovative analytic platforms owing to its high throughput and simplified data analysis.

On-stage bioreactor platform integrated with nano-patterned and gold-coated PDMS diaphragm for live cell stimulation and imaging.

Over the years, several in-vitro biosensing platforms have been developed for enhancing the maturation of the cultured cells. However, most of the proposed platforms met with limited success due to its inability for live-cell imaging, complicated fabrication, and not being advantageous from an economic perspective due to a higher price. To overcome the drawbacks of the current state-of-the-art, herein, we developed a next-generation stage-top incubator (STI) incorporated with nano grooves patterned PDMS diaphragm (NGPPD). The proposed device consists of a miniatured STI, the NGPPD functional well plates, and a mechanical stimulator. A thin layer of gold (Au) is deposited on the NGPPD to enhanced myogenic differentiation, cell maturation, and cell-cell interactions. The nano grooves are integrated on the PDMS surface to align the cardiomyocytes in the grooved direction during the culture period. The cardiomyocytes cultivated on the Au-deposited NGPPD are stimulated topographically and mechanically during the cultivation period. The enhanced cardiomyocytes maturation cultured on the Au-deposited NGPPD is experimentally demonstrated using immunofluorescence staining and PCR analysis.

Highly durable crack sensor integrated with silicone rubber cantilever for measuring cardiac contractility.

To date, numerous biosensing platforms have been developed for assessing drug-induced cardiac toxicity by measuring the change in contractile force of cardiomyocytes. However, these low sensitivity, low-throughput, and time-consuming processes are severely limited in their real-time applications. Here, we propose a cantilever device integrated with a polydimethylsiloxane (PDMS)-encapsulated crack sensor to measure cardiac contractility. The crack sensor is chemically bonded to a PDMS thin layer that allows it to be operated very stably in culture media. The reliability of the proposed crack sensor has been improved dramatically compared to no encapsulation layer. The highly sensitive crack sensor continuously measures the cardiac contractility without changing its gauge factor for up to 26 days (>5 million heartbeats), while changes in contractile force induced by drugs are monitored using the crack sensor-integrated cantilever. Finally, experimental results are compared with those obtained via conventional optical methods to verify the feasibility of building a contraction-based drug-toxicity testing system.

Micro-patterned SU-8 cantilever integrated with metal electrode for enhanced electromechanical stimulation of cardiac cells.

Over the past few years, cardiac tissue engineering has undergone tremendous progress. Various in vitro methods have been developed to improve the accuracy in the result of drug-induced cardiac toxicity screening. Herein, we propose a novel SU-8 cantilever integrated with an electromechanical-stimulator to enhance the maturation of cultured cardiac cells. The simultaneous electromechanical stimulation significantly enhances the contraction force of the cardiomyocytes, thereby increasing cantilever displacement. Fluorescence microscopy analysis was performed to confirm the improved maturation of the cardiomyocytes. After the initial experiments, the contractile behaviors of the cultured cardiomyocytes were investigated by measuring the mechanical deformation of the SU-8 cantilever. Finally, the proposed electromechanical-stimulator-integrated SU-8 cantilever was used to evaluate the adverse effects of different cardiac vascular drugs, i.e., verapamil, lidocaine, and isoproterenol, on the cultured cardiomyocytes. The physiology of the cardiac-drug-treated cardiomyocytes was examined with and without electrical stimulation of the cardiomyocytes. The experimental results indicate that the proposed cantilever platform can be used as a predictive assay system for preliminary cardiac drug toxicity screening applications.

Development of a Next-Generation Biosensing Platform for Simultaneous Detection of Mechano- and Electrophysiology of the Drug-Induced Cardiomyocytes.

Detection of adverse effects of cardiac toxicity at an early stage by in vitro methods is crucial for the preclinical drug screening. Over the years, several kinds of biosensing platforms have been proposed by the scientific society for the detection of cardiac toxicity. However, the proposed tissue platforms have been optimized to measure either mechanophysiology or electrophysiology of the cardiomyocytes but not both. Herein, we demonstrate in detail our successful attempt toward developing a novel "multifunctional microphysiological system" also known as "organs-on-chips" to measure simultaneously the mechanical and electrical characteristics of cardiomyocytes in vitro. The proposed device can rapidly recognize drug-induced cardiovascular toxicity in real time, which is one of the most significant factors for drug discovery and postmarketing surveillance. We confirm that the proposed sensor delivers the direct relationship between the contraction force and cell impedance of cardiomyocytes under the influence of different cardiovascular drugs such as verapamil, astemizole, and lidocaine. The obtained assay results provide a great potential for a deep understanding of the drug effects on the cardiomyocytes in vitro.

Contractile behaviors of cardiac muscle cells on mushroom-shaped micropillar arrays.

In this work we propose mushroom-shaped PDMS (Polydimethylsiloxane) µpillar arrays for enhancing the contractile force of cardiomyocytes during cell culturing. Conventional micropillar (µpillar) arrays with flat surfaces were employed as a standard sample to quantitatively recognize experimental data and to conclusively demonstrate the improved performance of mushroom-shaped PDMS µpillar arrays. Cardiomyocytes isolated from experimental animals were cultured on both of the fabricated µpillar arrays and then monitored over a growing period. Deflections of µpillars were precisely measured through a home-built analyzing system quantitatively representing the contractile force of cardiomyocytes. Mushroom-shaped PDMS µpillar arrays exhibited a 20% improved contractile force compared to conventional PDMS µpillar arrays due to their topographical dependency. Preliminary results also show that the proposed mushroom-shaped PDMS µpillar surface positively affects the Z-band width, actin filament polymerization and focal adhesion (FA) of cardiomyocytes. Further, the enhanced performance of mushroom-shaped PDMS µpillar arrays was confirmed by measuring the cardiac sarcomere α-actin length and myofilament width via ICC (immunocytochemistry) staining and western blot experiments.

Realizing Synergy between In2O3 Nanocubes and Nitrogen-Doped Reduced Graphene Oxide: An Excellent Nanocomposite for the Selective and Sensitive Detection of CO at Ambient Temperatures.

Hierarchical mesoporous In2O3 nanocubes and nitrogen-doped reduced graphene oxide-indium oxide nanocube (InNrGO) composites were prepared for carbon monoxide (CO) sensing. The as-synthesized materials were systematically investigated by different characterization techniques such as field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetic analysis, X-ray photoelectron spectroscopy, micro-Raman, Fourier transform infrared spectroscopy, and photoluminesce analysis. The obtained results are consistent with each other. The CO-sensing characteristics of the In2O3 nanocubes and InNrGO composites were examined at different operating temperatures (35 °C < Ts < 300 °C) and CO concentrations (1-1000 ppm). Owing to their large surface-to-volume ratio and porosity, the In2O3 nanocubes exhibited a superior sensitivity with a detection limit of 1 ppm at 250 °C. Furthermore, to enhance the sensing characteristics and reduce the operating temperature, a composite of NrGO and In2O3 nanocubes was fabricated. The incorporation of NrGO drastically improved the sensing performance of the In2O3 nanocubes, showing an excellent sensitivity (SR ∼ 3.6-5 ppm of CO at ∼35 °C) with appreciably fast response (ΓRES ∼ 22 s) and recovery (ΓREC ∼ 32 s) times. The sensing studies supported by the structural and morphological material characteristics lead to the plausible sensing mechanism proposed.

Hierarchical mesoporous In2O3 with enhanced CO sensing and photocatalytic performance: distinct morphologies of In(OH)3 via self assembly coupled in situ solid-solid transformation.

The present investigation details our interesting findings and insights into the evolution of exotic hierarchical superstructures of In(OH)3 under solvothermal conditions. Controlled variation of reaction parameters such as, reactant concentration, solvent system, crystal structure modifiers, water content along with temperature and time, yielded remarkable architectures. Diverse morphologies achieved for the first time includes (i) raspberry-like hollow spheres, (ii) nanosheet-assembled spheres, (iii) nanoparticle-assembled spheres, (iv) nanocube-assembled hollow spheres, (v) yolk-like spheres, (vi) solid spheres, (vii) nanosheets/flakes, and (viii) ultrafine nanosheets. A plausible mechanism is proposed based on the evidence gathered from a comprehensive analysis aided by electron microscopy and X-ray diffraction studies. Key stages of morphological evolution could be discerned and rationally correlated with nucleation, growth, oriented attachment, and Ostwald ripening mediated by dissolution-redeposition mechanism coupled with solid evacuation. Remarkably phase-pure bcc-In2O3 with retention of precursor morphology could be realized postcalcination at 400 °C, which underlines the advantage of this strategy. Two typical hierarchical structures (raspberry-like hollow spheres and nanoparticles assembled spheres) were investigated for their gas sensing and photocatalytic performances to highlight the advantages offered by nanostructuring. An impressive sensor response, Smax ≈ 7340 and 4055, respectively for the two structures along with appreciably fast response/recovery times over a wide concentration range and as low as 1 ppm exhibits the superior sensitivity toward carbon monoxide (CO). When compared to commercial In2O3, estimated rate constant indicates ∼3-4 times enhancement in photocatalytic activity of the substrates toward Rhodamine-B.