Engineering Cardiac Tissue for Advanced Heart-On-A-Chip Platforms

Imaging 3D cell cultures with optical microscopy

Three-dimensional (3D) cell cultures have gained popularity in recent years due to their ability to represent complex tissues or organs more faithfully than conventional two-dimensional (2D) cell culture. This article reviews the application of both 2D and 3D microscopy approaches for monitoring and studying 3D cell cultures. We first summarize the most popular optical microscopy methods that have been used with 3D cell cultures. We then discuss the general advantages and disadvantages of various microscopy techniques for several broad categories of investigation involving 3D cell cultures. Finally, we provide perspectives on key areas of technical need in which there are clear opportunities for innovation. Our goal is to guide microscope engineers and biomedical end users toward optimal imaging methods for specific investigational scenarios and to identify use cases in which additional innovations in high-resolution imaging could be helpful.

Bioengineering Approaches to In Vitro Modeling of Genetic and Acquired Cardiac Diseases

PURPOSE OF REVIEW

This review aims to explore recent advancements in bioengineering approaches used in developing and testing in vitro cardiac disease models. It seeks to find out how these tools can address the limitations of traditional in vitro models and be applied to improve our understanding of cardiac disease mechanisms, facilitate preclinical drug screening, and equip the development of personalized therapeutics.

RECENT FINDINGS

Human induced pluripotent stem cells have enabled the generation of diverse cardiac cell types and patient-specific models. Techniques like 3D tissue engineering, heart-on-a-chip platforms, biomechanical conditioning, and CRISPR-based gene editing have enabled faithful recreation of complex cardiac microenvironments and disease conditions. These models have advanced the study of both genetic and acquired cardiac disorders. Bioengineered in vitro models are transforming the basic science and clinical research in cardiovascular disease by improving the biomimicry and complexity of tissue analogues, increasing throughput and reproducibility of screening platforms, as well as offering patient and disease specificity. Despite challenges in scalability and functional maturity, integrating multiple bioengineering techniques with advanced analytical tools in in vitro modeling platforms holds promise for future precision and personalized medicine and therapeutic innovations.

Stretchable impedance electrode array with high durability for monitoring of cells under mechanical and chemical stimulations

Electrochemical impedance spectroscopy (EIS) serves as a non-invasive technique for assessing cell status, while mechanical stretching plays a pivotal role in stimulating cells to emulate their natural environment. Integrating these two domains enables the concurrent application of mechanical stimulation and EIS in a stretchable cell culture system. However, challenges arise from the difficulty in creating a durable and stable stretchable impedance electrode array. To overcome this limitation, we have developed a cell culture system integrated with a stretchable impedance electrode array (SIEA). This design enabled impedance monitoring during cell proliferation under mechanical stimulation over a long period of time due to the high mechanical durability and electrochemical stability of the SIEA. Our evaluation also involved testing the cytotoxicity of doxorubicin on H9C2 cells directly on the SIEA. The results underscore the significant potential of our SIEA device as an effective tool for monitoring cells subjected to mechanical stimulation and as a platform for drug toxicity testing.

Advances in cardiac organoid research: implications for cardiovascular disease treatment

Globally, cardiovascular diseases remain among the leading causes of mortality, highlighting the urgent need for innovative research models. Consequently, the development of accurate models that simulate cardiac function holds significant scientific and clinical value for both disease research and therapeutic interventions. Cardiac organoids, which are three-dimensional structures derived from the induced differentiation of stem cells, are particularly promising. These organoids not only replicate the autonomous beating and essential electrophysiological properties of the heart but are also widely employed in studies related to cardiac diseases, drug efficacy testing, and regenerative medicine. This review comprehensively surveys the various fabrication techniques used to create cardiac organoids and their diverse applications in modeling a range of cardiac diseases. We emphasize the role of advanced technologies in enhancing the maturation and functionality of cardiac cells, ensuring that these models closely resemble native cardiac tissue. Furthermore, we discuss monitoring techniques and evaluation parameters critical for assessing the performance of cardiac organoids, considering the complex interactions within multi-organ systems. This approach is vital for enhancing precision and efficiency in drug development, allowing for more effective therapeutic strategies. Ultimately, this review aims to provide a thorough and innovative perspective on both fundamental research and clinical treatment of cardiovascular diseases, offering insights that could pave the way for future advancements in understanding and addressing these prevalent health challenges.

3D Nanofiber-Assisted Embedded Extrusion Bioprinting for Oriented Cardiac Tissue Fabrication

Three-dimensional (3D) bioprinting technology stands out as a promising tissue manufacturing process to control the geometry precisely with cell-loaded bioinks. However, the isotropic culture environment within the bioink and the lack of topographical cues impede the formation of oriented cardiac tissue. To overcome this limitation, we present a novel method named 3D nanofiber-assisted embedded bioprinting (3D-NFEP) to fabricate cardiac tissue with an oriented morphology. Aligned 3D nanofiber scaffolds were fabricated by divergence electrospinning, which provided structural support for printing of the low-viscosity bioink and structural induction to cardiomyocytes. Cells adhered to the aligned fibers after hydrogel degradation, and a high degree of cell alignment was observed. This technology was also demonstrated as a feasible solution for multilayer cell printing. Therefore, 3D-NFEP was demonstrated as a promising method for bioprinting oriented cardiac tissue with low-viscosity bioink and is expected to be applied for structured and cardiac tissue engineering.

Revolutionizing Drug Discovery: The Impact of Distinct Designs and Biosensor Integration in Microfluidics-Based Organ-on-a-Chip Technology

Traditional drug development is a long and expensive process with high rates of failure. This has prompted the pharmaceutical industry to seek more efficient drug development frameworks, driving the emergence of organ-on-a-chip (OOC) based on microfluidic technologies. Unlike traditional animal experiments, OOC systems provide a more accurate simulation of human organ microenvironments and physiological responses, therefore offering a cost-effective and efficient platform for biomedical research, particularly in the development of new medicines. Additionally, OOC systems enable quick and real-time analysis, high-throughput experimentation, and automation. These advantages have shown significant promise in enhancing the drug development process. The success of an OOC system hinges on the integration of specific designs, manufacturing techniques, and biosensors to meet the need for integrated multiparameter datasets. This review focuses on the manufacturing, design, sensing systems, and applications of OOC systems, highlighting their design and sensing capabilities, as well as the technical challenges they currently face.

Electrospun Aligned Nanofiber Yarns Constructed Biomimetic M-Type Interface Integrated into Precise Co-Culture System as Muscle-Tendon Junction-on-a-Chip for Drug Development

The incorporation of engineered muscle-tendon junction (MTJ) with organ-on-a-chip technology provides promising in vitro models for the understanding of cell-cell interaction at the interface between muscle and tendon tissues. However, developing engineered MTJ tissue with biomimetic anatomical interface structure remains challenging, and the precise co-culture of engineered interface tissue is further regarded as a remarkable obstacle. Herein, an interwoven waving approach is presented to develop engineered MTJ tissue with a biomimetic "M-type" interface structure, and further integrated into a precise co-culture microfluidic device for functional MTJ-on-a-chip fabrication. These multiscale MTJ scaffolds based on electrospun nanofiber yarns enabled 3D cellular alignment and differentiation, and the "M-type" structure led to cellular organization and interaction at the interface zone. Crucially, a compartmentalized co-culture system is integrated into an MTJ-on-a-chip device for the precise co-culture of muscle and tendon zones using their medium at the same time. Such an MTJ-on-a-chip device is further served for drug-associated MTJ toxic or protective efficacy investigations. These results highlight that these interwoven nanofibrous scaffolds with biomimetic "M-type" interface are beneficial for engineered MTJ tissue development, and MTJ-on-a-chip with precise co-culture system indicated their promising potential as in vitro musculoskeletal models for drug development and biological mechanism studies.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

From Organ-on-a-Chip to Human-on-a-Chip: A Review of Research Progress and Latest Applications

Organ-on-a-Chip (OOC) technology, which emulates the physiological environment and functionality of human organs on a microfluidic chip, is undergoing significant technological advancements. Despite its rapid evolution, this technology is also facing notable challenges, such as the lack of vascularization, the development of multiorgan-on-a-chip systems, and the replication of the human body on a single chip. The progress of microfluidic technology has played a crucial role in steering OOC toward mimicking the human microenvironment, including vascularization, microenvironment replication, and the development of multiorgan microphysiological systems. Additionally, advancements in detection, analysis, and organoid imaging technologies have enhanced the functionality and efficiency of Organs-on-Chips (OOCs). In particular, the integration of artificial intelligence has revolutionized organoid imaging, significantly enhancing high-throughput drug screening. Consequently, this review covers the research progress of OOC toward Human-on-a-chip, the integration of sensors in OOCs, and the latest applications of organoid imaging technologies in the biomedical field.

Microfluidic-based cardiovascular systems for advanced study of atherosclerosis

Atherosclerosis (AS) is a significant global health concern due to its high morbidity and mortality rates. Extensive efforts have been made to replicate the cardiovascular system and explore the pathogenesis, diagnosis, and treatment of AS. Microfluidics has emerged as a valuable technology for modeling the cardiovascular system and studying AS. Here a brief review of the advances of microfluidic-based cardiovascular systems for AS research is presented. The critical pathogenetic mechanisms of AS investigated by microfluidic-based cardiovascular systems are categorized and reviewed, with a detailed summary of accurate diagnostic methods for detecting biomarkers using microfluidics represented. Furthermore, the review covers the evaluation and screening of AS drugs assisted by microfluidic systems, along with the fabrication of novel drug delivery carriers. Finally, the challenges and future prospects for advancing microfluidic-based cardiovascular systems in AS research are discussed and proposed, particularly regarding new opportunities in multi-disciplinary fundamental research and therapeutic applications for a broader range of disease treatments.

The Biomedical Applications of Biomolecule Integrated Biosensors for Cell Monitoring

Cell monitoring is essential for understanding the physiological conditions and cell abnormalities induced by various stimuli, such as stress factors, microbial invasion, and diseases. Currently, various techniques for detecting cell abnormalities and metabolites originating from specific cells are employed to obtain information on cells in terms of human health. Although the states of cells have traditionally been accessed using instrument-based analysis, this has been replaced by various sensor systems equipped with new materials and technologies. Various sensor systems have been developed for monitoring cells by recognizing biological markers such as proteins on cell surfaces, components on plasma membranes, secreted metabolites, and DNA sequences. Sensor systems are classified into subclasses, such as chemical sensors and biosensors, based on the components used to recognize the targets. In this review, we aim to outline the fundamental principles of sensor systems used for monitoring cells, encompassing both biosensors and chemical sensors. Specifically, we focus on biosensing systems in terms of the types of sensing and signal-transducing elements and introduce recent advancements and applications of biosensors. Finally, we address the present challenges in biosensor systems and the prospects that should be considered to enhance biosensor performance. Although this review covers the application of biosensors for monitoring cells, we believe that it can provide valuable insights for researchers and general readers interested in the advancements of biosensing and its further applications in biomedical fields.

Progress in cardiac tissue engineering and regeneration: Implications of gelatin-based hybrid scaffolds

Cardiovascular diseases, particularly myocardial infarction (MI), remain a leading cause of morbidity and mortality worldwide. Current treatments for MI, more palliative than curative, have limitations in reversing the disease completely. Tissue engineering (TE) has emerged as a promising strategy to address this challenge and may lead to improved therapeutic approaches for MI. Gelatin-based scaffolds, including gelatin and its derivative, gelatin methacrylate (GelMA), have attracted significant attention in cardiac tissue engineering (CTE) due to their optimal physical and biochemical properties and capacity to mimic the native extracellular matrix (ECM). CTE mainly recruits two classes of gelatin/GelMA-based scaffolds: hydrogels and nanofibrous. This article reviews state-of-the-art gelatin/GelMA-based hybrid scaffolds currently applied for CTE and regenerative therapy. Hybrid scaffolds, fabricated by combining gelatin/GelMA hydrogel or nanofibrous scaffolds with other materials such as natural/synthetic polymers, nanoparticles, protein-based biomaterials, etc., are explored for enhanced cardiac tissue regeneration functionality. The engraftment of stem/cardiac cells, bioactive molecules, or drugs into these hybrid systems shows great promise in cardiac tissue repair and regeneration. Finally, the role of gelatin/GelMA scaffolds combined with the 3D bioprinting strategy in CTE will also be briefly highlighted.