3D Printed Polycaprolactone Carbon Nanotube Composite Scaffolds for Cardiac Tissue Engineering

Recent Advances in Two-Dimensional Nanomaterials for Healthcare Monitoring

The development of advanced technologies for the fabrication of functional nanomaterials, nanostructures, and devices has facilitated the development of biosensors for analyses. Two-dimensional (2D) nanomaterials, with unique hierarchical structures, a high surface area, and the ability to be functionalized for target detection at the surface, exhibit high potential for biosensing applications. The electronic properties, mechanical flexibility, and optical, electrochemical, and physical properties of 2D nanomaterials can be easily modulated, enabling the construction of biosensing platforms for the detection of various analytes with targeted recognition, sensitivity, and selectivity. This review provides an overview of the recent advances in 2D nanomaterials and nanostructures used for biosensor and wearable-sensor development for healthcare and health-monitoring applications. Finally, the advantages of 2D-nanomaterial-based devices and several challenges in their optimal operation have been discussed to facilitate the development of smart high-performance biosensors in the future.

3D printed polycaprolactone/β-tricalcium phosphate/carbon nanotube composite - Physical properties and biocompatibility

Three-dimensional (3D) printing is a bio-fabrication technique used to process tissue-engineered scaffolds for bone repair and remodeling. Polycaprolactone (PCL)/β-tricalcium phosphate (TCP) has been used as a base and osteoconductive biomaterial for bone tissue engineering in the past decades. The current study reveals the fabrication of a polycaprolactone (PCL)/β-tricalcium phosphate (TCP) scaffold by incorporating carbon nanotubes (CNT) via 3D printing. The physical properties and cytocompatibility of a new type of tissue engineering composite from polycaprolactone/β-tri-calcium phosphate/carbon nanotubes were investigated, and it was an absorbable scaffold prepared via furnace deposition 3D printing technology. The scaffold was designed with CAD software, and the composite material was fabricated via 3D printing. The printed composite material was tested for mechanical strength, scanning electron microscope (SEM) analysis, porosity calculation, systemic toxicity test, hemolysis rate determination, and effect on the proliferation of rat adipose-derived stem cells cultured in vitro. A composite scaffold with a length of 15 mm, width of 10 mm, and height of 5 mm was manufactured through CAD software drawing and 3D printing technology. Scanning electron microscopy measurements and analysis of the internal pore size of the stent are appropriate; the pores are interconnected, and the mechanical strength matches the strength of human cancellous bone. The calculated porosity of the stent was >60%, non-toxic, and non-hemolytic. The proliferation activity of the ADSC co-cultured with different scaffold materials was as follows: polycaprolactone/β-tricalcium phosphate/0.2% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate/0.1% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate/0.3% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate scaffolds (P < 0.05). The results showed that polycaprolactone/β-tricalcium phosphate/0.2% carbon nanotube scaffolds promoted the adhesion and proliferation of ADSC. The combination of 3D printing technology and CAD software can be used to print personalized composite stents, which have the characteristics of repeatability, high precision, and low cost. Through 3D printing technology, combining a variety of materials with each other can provide the greatest advantages of materials. The waste of resources was avoided. The prepared polycaprolactone/β-tri-calcium phosphate/0.2% carbon nanotube scaffold has a good pore structure and mechanical properties that mimic human cancellous bone, is non-toxic and non-hemolytic, and is effective in promoting ADSC proliferation in vitro. Given this correspondence, 3D printed scaffold shows good biocompatibility and strength, and the fabrication method provides a proof of concept for developing scaffolds for bone tissue engineering applications.

Carbon nanotube nanocomposite scaffolds: advances in fabrication and applications for tissue regeneration and cancer therapy

Carbon nanotube (CNT) nanocomposite scaffolds have emerged as highly promising frameworks for tissue engineering research. By leveraging their intrinsic electrical conductivity and valuable mechanical properties, CNTs are commonly dispersed into polymers to create robust, electrically conductive scaffolds that facilitate tissue regeneration and remodeling. This article explores the latest progress and challenges related to CNT dispersion, functionalization, and scaffold printing techniques, including electrospinning and 3D printing. Notably, these CNT scaffolds have demonstrated remarkable positive effects across various cell culture systems, stimulating neuronal growth, promoting cardiomyocyte maturation, and facilitating osteocyte differentiation. These encouraging results have sparked significant interest within the regenerative medicine field, including neural, cardiac, muscle, and bone regenerations. However, addressing the concern of CNT cytotoxicity in these scaffolds remains critical. Consequently, substantial efforts are focused on exploring strategies to minimize cytotoxicity associated with CNT-based scaffolds. Moreover, researchers have also explored the intriguing possibility of utilizing the natural cytotoxic properties of CNTs to selectively target cancer cells, opening up promising avenues for cancer therapy. More research should be conducted on cutting-edge applications of CNT-based scaffolds through phototherapy and electrothermal ablation. Unlike drug delivery systems, these novel methodologies can combine 3D additive manufacturing with the innate physical properties of CNT in response to electromagnetic stimuli to efficiently target localized tumors. Taken together, the unique properties of CNT-based nanocomposite scaffolds position them as promising candidates for revolutionary breakthroughs in both regenerative medicine and cancer treatment. Continued research and innovation in this area hold significant promise for improving healthcare outcomes.

Recent advances in tailoring stimuli-responsive hybrid scaffolds for cardiac tissue engineering and allied applications

To recapitulate bio-physical properties and functional behaviour of native heart tissues, recent tissue engineering-based approaches are focused on developing smart/stimuli-responsive materials for interfacing cardiac cells. Overcoming the drawbacks of the traditionally used biomaterials, these smart materials portray outstanding mechanical and conductive properties while promoting cell-cell interaction and cell-matrix transduction cues in such excitable tissues. To date, a large number of stimuli-responsive materials have been employed for interfacing cardiac tissues alone or in combination with natural/synthetic materials for cardiac tissue engineering. However, their comprehensive classification and a comparative analysis of the role played by these materials in regulating cardiac cell behaviour and in vivo metabolism are much less discussed. In an attempt to cover the recent advances in fabricating stimuli-responsive biomaterials for engineering cardiac tissues, this review details the role of these materials in modulating cardiomyocyte behaviour, functionality and surrounding matrix properties. Furthermore, concerns and challenges regarding the clinical translation of these materials and the possibility of using such materials for the fabrication of bio-actuators and bioelectronic devices are discussed.

Additive manufacturing of sustainable biomaterials for biomedical applications

Biopolymers are promising environmentally benign materials applicable in multifarious applications. They are especially favorable in implantable biomedical devices thanks to their excellent unique properties, including bioactivity, renewability, bioresorbability, biocompatibility, biodegradability and hydrophilicity. Additive manufacturing (AM) is a flexible and intricate manufacturing technology, which is widely used to fabricate biopolymer-based customized products and structures for advanced healthcare systems. Three-dimensional (3D) printing of these sustainable materials is applied in functional clinical settings including wound dressing, drug delivery systems, medical implants and tissue engineering. The present review highlights recent advancements in different types of biopolymers, such as proteins and polysaccharides, which are employed to develop different biomedical products by using extrusion, vat polymerization, laser and inkjet 3D printing techniques in addition to normal bioprinting and four-dimensional (4D) bioprinting techniques. This review also incorporates the influence of nanoparticles on the biological and mechanical performances of 3D-printed tissue scaffolds. This work also addresses current challenges as well as future developments of environmentally friendly polymeric materials manufactured through the AM techniques. Ideally, there is a need for more focused research on the adequate blending of these biodegradable biopolymers for achieving useful results in targeted biomedical areas. We envision that biopolymer-based 3D-printed composites have the potential to revolutionize the biomedical sector in the near future.

Current Status and Future Outlook of Additive Manufacturing Technologies for the Reconstruction of the Trachea

Tracheal stenosis and defects occur congenitally and in patients who have undergone tracheal intubation and tracheostomy due to long-term intensive care. Such issues may also be observed during tracheal removal during malignant head and neck tumor resection. However, to date, no treatment method has been identified that can simultaneously restore the appearance of the tracheal skeleton while maintaining respiratory function in patients with tracheal defects. Therefore, there is an urgent need to develop a method that can maintain tracheal function while simultaneously reconstructing the skeletal structure of the trachea. Under such circumstances, the advent of additive manufacturing technology that can create customized structures using patient medical image data provides new possibilities for tracheal reconstruction surgery. In this study, the three-dimensional (3D) printing and bioprinting technologies used in tracheal reconstruction are summarized, and various research results related to the reconstruction of mucous membranes, cartilage, blood vessels, and muscle tissue, which are tissues required for tracheal reconstruction, are classified. The prospects for 3D-printed tracheas in clinical studies are also described. This review serves as a guide for the development of artificial tracheas and clinical trials using 3D printing and bioprinting.

Fundamentals and Applications of Raman-Based Techniques for the Design and Development of Active Biomedical Materials

Raman spectroscopy is an analytical method based on light-matter interactions that can interrogate the vibrational modes of matter and provide representative molecular fingerprints. Mediated by its label-free, non-invasive nature, and high molecular specificity, Raman-based techniques have become ubiquitous tools for in situ characterization of materials. This review comprehensively describes the theoretical and practical background of Raman spectroscopy and its advanced variants. The numerous facets of material characterization that Raman scattering can reveal, including biomolecular identification, solid-to-solid phase transitions, and spatial mapping of biomolecular species in bioactive materials, are highlighted. The review illustrates the potential of these techniques in the context of active biomedical material design and development by highlighting representative studies from the literature. These studies cover the use of Raman spectroscopy for the characterization of both natural and synthetic biomaterials, including engineered tissue constructs, biopolymer systems, ceramics, and nanoparticle formulations, among others. To increase the accessibility and adoption of these techniques, the present review also provides the reader with practical recommendations on the integration of Raman techniques into the experimental laboratory toolbox. Finally, perspectives on how recent developments in plasmon- and coherently-enhanced Raman spectroscopy can propel Raman from underutilized to critical for biomaterial development are provided.

Molecular dynamics simulations and in vitro studies of hybrid decellularized leaf-peptide-polypyrrole composites for potential tissue engineering applications

Tissue engineering (TE) aims to repair and regenerate damaged tissue by an assimilation of optimal combination of cells specific to the tissue with an appropriate biomaterial. In this work, a new biomaterial for potential cardiac TE applications was developed by utilizing a combination of in silico studies and in vitro experiments. Molecular dynamics (MD) simulations for the formation of the novel composite prepared from the decellularized leaf components cellulose and pectin along with the VEGF derived peptide (NYLTHRQ) and polypyrrole (PPy) was carried out to assess self-assembly, mechanical properties, and interactions with integrin and NPR-C receptors which are commonly found in cells of cardiac tissue. Results of molecular dynamics simulations indicated the successful formation of stable assemblies. MD simulations also revealed that the scaffold successfully interacted with integrin and NPR-C receptors. As a proof of concept, beet leaves were decellularized (DC) and cross-linked with NYLTHRQ and PPy using layer-by-layer assembly. Decellularization (DC) was confirmed by DNA and protein quantification. Incorporation of the NYLTHRQ peptide and polypyrrole was confirmed by FTIR spectroscopy and SEM imaging. The DC-NYLTHRQ-PPy scaffold was seeded with co-cultured cardiomyocytes and vascular smooth muscle cells. The scaffold promoted cell proliferation and adhesion. Actin and Troponin T immunofluorescence staining showed the presence of these critical cardiomyocyte markers. Thus, for the first time we have developed a decellularized leaf-peptide-PPy composite scaffold by a combination of in silico studies and laboratory analyses that may have potential applications in cardiac TE.Communicated by Ramaswamy H. Sarma.

Fabrication and Characterization Techniques of In Vitro 3D Tissue Models

The culturing of cells in the laboratory under controlled conditions has always been crucial for the advancement of scientific research. Cell-based assays have played an important role in providing simple, fast, accurate, and cost-effective methods in drug discovery, disease modeling, and tissue engineering while mitigating reliance on cost-intensive and ethically challenging animal studies. The techniques involved in culturing cells are critical as results are based on cellular response to drugs, cellular cues, external stimuli, and human physiology. In order to establish in vitro cultures, cells are either isolated from normal or diseased tissue and allowed to grow in two or three dimensions. Two-dimensional (2D) cell culture methods involve the proliferation of cells on flat rigid surfaces resulting in a monolayer culture, while in three-dimensional (3D) cell cultures, the additional dimension provides a more accurate representation of the tissue milieu. In this review, we discuss the various methods involved in the development of 3D cell culture systems emphasizing the differences between 2D and 3D systems and methods involved in the recapitulation of the organ-specific 3D microenvironment. In addition, we discuss the latest developments in 3D tissue model fabrication techniques, microfluidics-based organ-on-a-chip, and imaging as a characterization technique for 3D tissue models.

Design and engineering of organ-on-a-chip

Organ-on-a-chip (OOC) is an emerging interdisciplinary technology that reconstitutes the structure, function, and physiology of human tissues as an alternative to conventional preclinical models for drug screening. Over the last decade, substantial progress has been made in mimicking tissue- and organ-level functions on chips through technical advances in biomaterials, stem cell engineering, microengineering, and microfluidic technologies. Structural and engineering constituents, as well as biological components, are critical factors to be considered to reconstitute the tissue function and microenvironment on chips. In this review, we highlight critical engineering technologies for reconstructing the tissue microarchitecture and dynamic spatiotemporal microenvironment in OOCs. We review the technological advances in the field of OOCs for a range of applications, including systemic analysis tools that can be integrated with OOCs, multiorgan-on-chips, and large-scale manufacturing. We then discuss the challenges and future directions for the development of advanced end-user-friendly OOC systems for a wide range of applications.

Electrically conductive carbon-based (bio)-nanomaterials for cardiac tissue engineering

A proper self-regenerating capability is lacking in human cardiac tissue which along with the alarming rate of deaths associated with cardiovascular disorders makes tissue engineering critical. Novel approaches are now being investigated in order to speedily overcome the challenges in this path. Tissue engineering has been revolutionized by the advent of nanomaterials, and later by the application of carbon-based nanomaterials because of their exceptional variable functionality, conductivity, and mechanical properties. Electrically conductive biomaterials used as cell bearers provide the tissue with an appropriate microenvironment for the specific seeded cells as substrates for the sake of protecting cells in biological media against attacking mechanisms. Nevertheless, their advantages and shortcoming in view of cellular behavior, toxicity, and targeted delivery depend on the tissue in which they are implanted or being used as a scaffold. This review seeks to address, summarize, classify, conceptualize, and discuss the use of carbon-based nanoparticles in cardiac tissue engineering emphasizing their conductivity. We considered electrical conductivity as a key affecting the regeneration of cells. Correspondingly, we reviewed conductive polymers used in tissue engineering and specifically in cardiac repair as key biomaterials with high efficiency. We comprehensively classified and discussed the advantages of using conductive biomaterials in cardiac tissue engineering. An overall review of the open literature on electroactive substrates including carbon-based biomaterials over the last decade was provided, tabulated, and thoroughly discussed. The most commonly used conductive substrates comprising graphene, graphene oxide, carbon nanotubes, and carbon nanofibers in cardiac repair were studied.

Bioadhesive Gauze Embedded with Chitosan-Butein Bioconjugate: A Redox-Active pH Sensor Platform

With the ever-growing global wound care market, demand for robust redox-active healthcare material is obvious for the construction of wearable sensor platforms. Surface reactive functional group-rich material like chitosan holds huge potential for electrochemical biosensor application. Herein, a metal-free redox-active chitosan-butein (CSB) bioconjugate is processed into epidermal bioadhesive electrode material useful for pH sensors promising toward wound site analysis. A two-electrode system devised for conducting carbon-reinforced silver chloride paste and CSB-modified carbon/silver chloride matrix was used as a reference and working electrodes, respectively. Dimensions of working and reference electrodes (4 mm) were designed by 2D cutter plotter-assisted stenciling. The cross-sectional topology of the constructed adhesive CSB-sensor platform exhibits an average surface thickness of 183 ± 2 μm. Cyclic voltammetric analysis revealed the inherent 2e^-/2H⁺ transfer attributed to the catechol OH groups of graft polymerized CSB modified on adhesive gauze. As-fabricated modified electrode substrates exhibit distinguishable potential differences with respect to electrolytes of varied pH (between 5 to 9), promising for wound site analysis.

Conductive and Semiconductive Nanocomposite-Based Hydrogels for Cardiac Tissue Engineering

Cardiovascular disease is the leading cause of death worldwide and the most common cause is myocardial infarction. Therefore, appropriate approaches should be used to repair damaged heart tissue. Recently, cardiac tissue engineering approaches have been extensively studied. Since the creation of the nature of cardiovascular tissue engineering, many advances have been made in cellular and scaffolding technologies. Due to the hydrated and porous structures of the hydrogel, they are used as a support matrix to deliver cells to the infarct tissue. In heart tissue regeneration, bioactive and biodegradable hydrogels are required by simulating native tissue microenvironments to support myocardial wall stress in addition to preserving cells. Recently, the use of nanostructured hydrogels has increased the use of nanocomposite hydrogels and has revolutionized the field of cardiac tissue engineering. Therefore, to overcome the limitation of the use of hydrogels due to their mechanical fragility, various nanoparticles of polymers, metal, and carbon are used in tissue engineering and create a new opportunity to provide hydrogels with excellent properties. Here, the types of synthetic and natural polymer hydrogels, nanocarbon-based hydrogels, and other nanoparticle-based materials used for cardiac tissue engineering with emphasis on conductive nanostructured hydrogels are briefly introduced.

Advances in 3D bioprinting of tissues/organs for regenerative medicine and in-vitro models

Tissue/organ shortage is a major medical challenge due to donor scarcity and patient immune rejections. Furthermore, it is difficult to predict or mimic the human disease condition in animal models during preclinical studies because disease phenotype differs between humans and animals. Three-dimensional bioprinting (3DBP) is evolving into an unparalleled multidisciplinary technology for engineering three-dimensional (3D) biological tissue with complex architecture and composition. The technology has emerged as a key driver by precise deposition and assembly of biomaterials with patient's/donor cells. This advancement has aided in the successful fabrication of in vitro models, preclinical implants, and tissue/organs-like structures. Here, we critically reviewed the current state of 3D-bioprinting strategies for regenerative therapy in eight organ systems, including nervous, cardiovascular, skeletal, integumentary, endocrine and exocrine, gastrointestinal, respiratory, and urinary systems. We also focus on the application of 3D bioprinting to fabricated in vitro models to study cancer, infection, drug testing, and safety assessment. The concept of in situ 3D bioprinting is discussed, which is the direct printing of tissues at the injury or defect site for reparative and regenerative therapy. Finally, issues such as scalability, immune response, and regulatory approval are discussed, as well as recently developed tools and technologies such as four-dimensional and convergence bioprinting. In addition, information about clinical trials using 3D printing has been included.

Recent advances in 3D-printed polylactide and polycaprolactone-based biomaterials for tissue engineering applications

The three-dimensional printing (3DP) also known as the additive manufacturing (AM), a novel and futuristic technology that facilitates the printing of multiscale, biomimetic, intricate cytoarchitecture, function-structure hierarchy, multi-cellular tissues in the complicated micro-environment, patient-specific scaffolds, and medical devices. There is an increasing demand for developing 3D-printed products that can be utilized for organ transplantations due to the organ shortage. Nowadays, the 3DP has gained considerable interest in the tissue engineering (TE) field. Polylactide (PLA) and polycaprolactone (PCL) are exemplary biomaterials with excellent physicochemical properties and biocompatibility, which have drawn notable attraction in tissue regeneration. Herein, the recent advancements in the PLA and PCL biodegradable polymer-based composites as well as their reinforcement with hydrogels and bio-ceramics scaffolds manufactured through 3DP are systematically summarized and the applications of bone, cardiac, neural, vascularized and skin tissue regeneration are thoroughly elucidated. The interaction between implanted biodegradable polymers, in-vivo and in-vitro testing models for possible evaluation of degradation and biological properties are also illustrated. The final section of this review incorporates the current challenges and future opportunities in the 3DP of PCL- and PLA-based composites that will prove helpful for biomedical engineers to fulfill the demands of the clinical field.

Current Applications of Polycaprolactone as a Scaffold Material for Heart Regeneration

Despite numerous advances in treatments for cardiovascular disease, heart failure (HF) remains the leading cause of death worldwide. A significant factor contributing to the progression of cardiovascular diseases into HF is the loss of functioning cardiomyocytes. The recent growth in the field of cardiac tissue engineering has the potential to not only reduce the downstream effects of injured tissues on heart function and longevity but also re-engineer cardiac function through regeneration of contractile tissue. One leading strategy to accomplish this is via a cellularized patch that can be surgically implanted onto a diseased heart. A key area of this field is the use of tissue scaffolds to recapitulate the mechanical and structural environment of the native heart and thus promote engineered myocardium contractility and function. While the strong mechanical properties and anisotropic structural organization of the native heart can be largely attributed to a robust extracellular matrix, similar strength and organization has proven to be difficult to achieve in cultured tissues. Polycaprolactone (PCL) is an emerging contender to fill these gaps in fabricating scaffolds that mimic the mechanics and structure of the native heart. In the field of cardiovascular engineering, PCL has recently begun to be studied as a scaffold for regenerating the myocardium due to its facile fabrication, desirable mechanical, chemical, and biocompatible properties, and perhaps most importantly, biodegradability, which make it suitable for regenerating and re-engineering function to the heart after disease or injury. This review focuses on the application of PCL as a scaffold specifically in myocardium repair and regeneration and outlines current fabrication approaches, properties, and possibilities of PCL incorporation into engineered myocardium, as well as provides suggestions for future directions and a roadmap toward clinical translation of this technology.

Interfaces Based on Laser-Structured Arrays of Carbon Nanotubes with Albumin for Electrical Stimulation of Heart Cell Growth

Successful formation of electronic interfaces between living cells and electronic components requires both good cell viability and performance level. This paper presents a technology for the formation of nanostructured arrays of multi-walled carbon nanotubes (MWCNT) in biopolymer (albumin) layer for higher biocompatibility. The layer of liquid albumin dispersion was sprayed on synthesized MWCNT arrays by deposition system. These nanostructures were engineered using the nanosecond pulsed laser radiation mapping in the near-IR spectral range (λ = 1064 nm). It was determined that the energy density of 0.015 J/cm² provided a sufficient structuring of MWCNT. The structuring effect occurred during the formation of C–C bonds simultaneously with the formation of a cellular structure of nanotubes in the albumin matrix. It led to a decrease in the nanotube defectiveness, which was observed during the Raman spectroscopy. In addition, laser structuring led to a more than twofold increase in the electrical conductivity of MWCNT arrays with albumin (215.8 ± 10 S/m). Successful electric stimulation of cells on the interfaces with the system based on a culture plate was performed, resulting in the enhanced cell proliferation. Overall, the MWCNT laser-structured arrays with biopolymers might be a promising material for extended biomedical applications.

Electrospun Nanofibers Revisited: An Update on the Emerging Applications in Nanomedicine

Electrospinning (ES) has become a straightforward and customizable drug delivery technique for fabricating drug-loaded nanofibers (NFs) using various biodegradable and non-biodegradable polymers. One of NF's pros is to provide a controlled drug release through managing the NF structure by changing the spinneret type and nature of the used polymer. Electrospun NFs are employed as implants in several applications including, cancer therapy, microbial infections, and regenerative medicine. These implants facilitate a unique local delivery of chemotherapy because of their high loading capability, wide surface area, and cost-effectiveness. Multi-drug combination, magnetic, thermal, and gene therapies are promising strategies for improving chemotherapeutic efficiency. In addition, implants are recognized as an effective antimicrobial drug delivery system overriding drawbacks of traditional antibiotic administration routes such as their bioavailability and dosage levels. Recently, a sophisticated strategy has emerged for wound healing by producing biomimetic nanofibrous materials with clinically relevant properties and desirable loading capability with regenerative agents. Electrospun NFs have proposed unique solutions, including pelvic organ prolapse treatment, viable alternatives to surgical operations, and dental tissue regeneration. Conventional ES setups include difficult-assembled mega-sized equipment producing bulky matrices with inadequate stability and storage. Lately, there has become an increasing need for portable ES devices using completely available off-shelf materials to yield highly-efficient NFs for dressing wounds and rapid hemostasis. This review covers recent updates on electrospun NFs in nanomedicine applications. ES of biopolymers and drugs is discussed regarding their current scope and future outlook.

Nanomaterials: A Promising Therapeutic Approach for Cardiovascular Diseases

Cardiovascular diseases (CVDs) are a primary cause of death globally. A few classic and hybrid treatments exist to treat CVDs. However, they lack in both safety and effectiveness. Thus, innovative nanomaterials for disease diagnosis and treatment are urgently required. The tiny size of nanomaterials allows them to reach more areas of the heart and arteries, making them ideal for CVDs. Atherosclerosis causes arterial stenosis and reduced blood flow. The most common treatment is medication and surgery to stabilize the disease. Nanotechnologies are crucial in treating vascular disease. Nanomaterials may be able to deliver medications to lesion sites after being infused into the circulation. Newer point-of-care devices have also been considered together with nanomaterials. For example, this study will look at the use of nanomaterials in imaging, diagnosing, and treating CVDs.

2D Materials for Cardiac Tissue Repair and Regeneration

Cardiovascular diseases (CVDs) have a massive impact on human health. Due to the limited regeneration capacity of adult heart tissue, CVDs are the leading cause of death and disability worldwide. Even though there are surgical and pharmacological treatments for CVDs, regenerative strategies are the most promising approaches and have the potential to benefit millions of people. As in any other tissue engineering approach, the repair and regeneration of damaged cardiac tissues generally involve scaffolds made up of biodegradable and biocompatible materials, cellular components such as stem cells, and growth factors. This review provides an overview of biomaterial-based tissue engineering approaches for CVDs with a specific focus on the potential of 2D materials. It is essential to consider both physicochemical and immunomodulatory properties for evaluating the applicability of 2D materials in cardiac tissue repair and regeneration. As new members of the 2D materials will be explored, they will quickly become part of cardiac tissue engineering technologies.

Hybrid biofabrication of 3D osteoconductive constructs comprising Mg-based nanocomposites and cell-laden bioinks for bone repair

Tissue engineering approaches for bone repair have rapidly evolved due to the development of novel biofabrication technologies, providing an opportunity to fabricate anatomically-accurate living implants with precise placement of specific cell types. However, limited availability of biomaterial inks, that can be 3D-printed with high resolution, while providing high structural support and the potential to direct cell differentiation and maturation towards the osteogenic phenotype, remains an ongoing challenge. Aiming towards a multifunctional biomaterial ink with high physical stability and biological functionality, this work describes the development of a nanocomposite biomaterial ink (Mg-PCL) comprising of magnesium hydroxide nanoparticles (Mg) and polycaprolactone (PCL) thermoplastic for 3D printing of strong and bioactive bone regenerative scaffolds. We characterised the Mg nanoparticle system and systematically investigated the cytotoxic and osteogenic effects of Mg supplementation to human mesenchymal stromal cells (hMSCs) 2D-cultures. Next, we prepared Mg-PCL biomaterial ink using a solvent casting method, and studied the effect of Mg over mechanical properties, printability and scaffold degradation. Furthermore, we delivered MSCs within Mg-PCL scaffolds using a gelatin-methacryloyl (GelMA) matrix, and evaluated the effect of Mg over cell viability and osteogenic differentiation. Nanocomposite Mg-PCL could be printed with high fidelity at 20 wt% of Mg content, and generated a mechanical reinforcement between 30%-400% depending on the construct internal geometry. We show that Mg-PCL degrades faster than standard PCL in an accelerated-degradation assay, which has positive implications towards in vivo implant degradation and bone regeneration. Mg-PCL did not affect MSCs viability, but enhanced osteogenic differentiation and bone-specific matrix deposition, as demonstrated by higher ALP/DNA levels and Alizarin Red calcium staining. Finally, we present proof of concept of Mg-PCL being utilised in combination with a bone-specific bioink (Sr-GelMA) in a coordinated-extrusion bioprinting strategy for fabrication of hybrid constructs with high stability and synergistic biological functionality. Mg-PCL further enhanced the osteogenic differentiation of encapsulated MSCs and supported bone ECM deposition within the bioink component of the hybrid construct, evidenced by mineralised nodule formation, osteocalcin (OCN) and collagen type-I (Col I) expression within the bioink filaments. This study demonstrated that magnesium-based nanocomposite bioink material optimised for extrusion-based 3D printing of bone regenerative scaffolds provide enhanced mechanical stability and bone-related bioactivity with promising potential for skeletal tissue regeneration.

Nanoparticles: Promising Tools for the Treatment and Prevention of Myocardial Infarction

Despite several recent advances, current therapy and prevention strategies for myocardial infarction are far from satisfactory, owing to limitations in their applicability and treatment effects. Nanoparticles (NPs) enable the targeted and stable delivery of therapeutic compounds, enhance tissue engineering processes, and regulate the behaviour of transplants such as stem cells. Thus, NPs may be more effective than other mechanisms, and may minimize potential adverse effects. This review provides evidence for the view that function-oriented systems are more practical than traditional material-based systems; it also summarizes the latest advances in NP-based strategies for the treatment and prevention of myocardial infarction.

Converging functionality: Strategies for 3D hybrid-construct biofabrication and the role of composite biomaterials for skeletal regeneration

The evolution of additive manufacturing (AM) technologies, biomaterial development and our increasing understanding of cell biology has created enormous potential for the development of personalized regenerative therapies. In the context of skeletal tissue engineering, physical and biological demands play key roles towards successful construct implantation and the achievement of bone, cartilage and blood vessel tissue formation. Nevertheless, meeting such physical and biological demands to mimic the complexity of human tissues and their functionality is still a significant ongoing challenge. Recent studies have demonstrated that combination of AM technologies and advanced biomaterials has great potential towards skeletal tissue engineering. This review aims to analyze how the most prominent technologies and discoveries in the field converge towards the development of advanced constructs for skeletal regeneration. Particular attention is placed on hybrid biofabrication strategies, combining bioinks for cell delivery with biomaterial inks providing physical support. Hybrid biofabrication has been the focus of recent emerging strategies, however there has been limited review and analysis of these techniques and the challenges involved. Furthermore, we have identified that there are multiple hybrid fabrication strategies, here we present a category system where each strategy is reviewed highlighting their distinct advantages, challenges and potential applications. In addition, bioinks and biomaterial inks are the main components of the hybrid biofabrication strategies, where it is recognized that such platforms still lack optimal physical and biological functionality. Thus, this review also explores the development of composite materials specifically targeting the enhancement of physical and biological functionality towards improved skeletal tissue engineering. STATEMENT OF SIGNIFICANCE: Biofabrication strategies capable of recreating the complexity of native tissues could open new clinical possibilities towards patient-specific regenerative therapies and disease models. Several reviews target the existing additive manufacturing (AM) technologies that may be utilised for biomedical purposes. However, this work presents a unique perspective, describing how such AM technologies have been recently translated towards hybrid fabrication strategies, targeting the fabrication of constructs with converging physical and biological properties. Furthermore, we address composite bioinks and biomaterial inks that have been engineered to overcome traditional limitations, and might be applied to the hybrid fabrication strategies outlined. This work offers ample perspectives and insights into the current and future challenges for the fabrication of skeletal tissues aiming towards clinical and biomedical applications.

Composite Inks for Extrusion Printing of Biological and Biomedical Constructs

Extrusion-based three-dimensional (3D) printing is an emerging technology for the fabrication of complex structures with various biological and biomedical applications. The method is based on the layer-by-layer construction of the product using a printable ink. The material used as the ink should possess proper rheological properties and desirable performances. Composite materials, which are extensively used in 3D printing applications, can improve the printability and offer superior performances for the printed constructs. Herein, we review composite inks with a focus on composite hydrogels. The properties of different additives including fibers and nanoparticles are discussed. The performances of various composite inks in biological and biomedical systems are delineated through analyzing the synergistic effects between the composite ink components. Different applications, including tissue engineering, tissue model engineering, soft robotics, and four-dimensional printing, are selected to demonstrate how 3D-printable composite inks are exploited to achieve various desired functionality. This review finally presents an outlook of future perspectives on the design of composite inks.

Strategies for constructing pluripotent stem cell- and progenitor cell-derived three-dimensional cardiac micro-tissues

Three-dimensional (3D) cardiac micro-tissue is a promising model for simulating the structural and functional features of heart in vitro. This scientific achievement provides a platform for exploration about the mechanisms on the development, damage, and regeneration of tissue, hence, paving a way toward development of novel therapies for heart diseases. However, 3D micro-tissue technology is still in its infant stages faced with many challenges such as incompleteness of the tissue microarchitecture, loss of the resident immune cells, poor reproducibility, and deficiencies in continuously feeding the nutrients and removing wastes during micro-tissue culturing. There is an urgent need to optimize the construction of 3D cardiac micro-tissue and improve functions of the involved cells. Therefore, scaffolds and cell resources for building 3D cardiac micro-tissues, strategies for inducing the maturation and functionalization of pluripotent stem cell- or cardiac progenitor cell-derived cardiomyocytes, and the major challenges were reviewed in this writing to enable future fabrication of 3D cardiac micro-tissues or organoids for drug screening, disease modeling, regeneration treatment, and so on.

Carbon nanomaterials for cardiovascular theranostics: Promises and challenges

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Heart attack and stroke cause irreversible tissue damage. The currently available treatment options are limited to "damage-control" rather than tissue repair. The recent advances in nanomaterials have offered novel approaches to restore tissue function after injury. In particular, carbon nanomaterials (CNMs) have shown significant promise to bridge the gap in clinical translation of biomaterial based therapies. This family of carbon allotropes (including graphenes, carbon nanotubes and fullerenes) have unique physiochemical properties, including exceptional mechanical strength, electrical conductivity, chemical behaviour, thermal stability and optical properties. These intrinsic properties make CNMs ideal materials for use in cardiovascular theranostics. This review is focused on recent efforts in the diagnosis and treatment of heart diseases using graphenes and carbon nanotubes. The first section introduces currently available derivatives of graphenes and carbon nanotubes and discusses some of the key characteristics of these materials. The second section covers their application in drug delivery, biosensors, tissue engineering and immunomodulation with a focus on cardiovascular applications. The final section discusses current shortcomings and limitations of CNMs in cardiovascular applications and reviews ongoing efforts to address these concerns and to bring CNMs from bench to bedside.

Extrinsically Conductive Nanomaterials for Cardiac Tissue Engineering Applications

Myocardial infarction (MI) is the consequence of coronary artery thrombosis resulting in ischemia and necrosis of the myocardium. As a result, billions of contractile cardiomyocytes are lost with poor innate regeneration capability. This degenerated tissue is replaced by collagen-rich fibrotic scar tissue as the usual body response to quickly repair the injury. The non-conductive nature of this tissue results in arrhythmias and asynchronous beating leading to total heart failure in the long run due to ventricular remodelling. Traditional pharmacological and assistive device approaches have failed to meet the utmost need for tissue regeneration to repair MI injuries. Engineered heart tissues (EHTs) seem promising alternatives, but their non-conductive nature could not resolve problems such as arrhythmias and asynchronous beating for long term in-vivo applications. The ability of nanotechnology to mimic the nano-bioarchitecture of the extracellular matrix and the potential of cardiac tissue engineering to engineer heart-like tissues makes it a unique combination to develop conductive constructs. Biomaterials blended with conductive nanomaterials could yield conductive constructs (referred to as extrinsically conductive). These cell-laden conductive constructs can alleviate cardiac functions when implanted in-vivo. A succinct review of the most promising applications of nanomaterials in cardiac tissue engineering to repair MI injuries is presented with a focus on extrinsically conductive nanomaterials.

3D bioprinting in cardiac tissue engineering

Heart disease is the main cause of death worldwide. Because death of the myocardium is irreversible, it remains a significant clinical challenge to rescue myocardial deficiency. Cardiac tissue engineering (CTE) is a promising strategy for repairing heart defects and offers platforms for studying cardiac tissue. Numerous achievements have been made in CTE in the past decades based on various advanced engineering approaches. 3D bioprinting has attracted much attention due to its ability to integrate multiple cells within printed scaffolds with complex 3D structures, and many advancements in bioprinted CTE have been reported recently. Herein, we review the recent progress in 3D bioprinting for CTE. After a brief overview of CTE with conventional methods, the current 3D printing strategies are discussed. Bioink formulations based on various biomaterials are introduced, and strategies utilizing composite bioinks are further discussed. Moreover, several applications including heart patches, tissue-engineered cardiac muscle, and other bionic structures created via 3D bioprinting are summarized. Finally, we discuss several crucial challenges and present our perspective on 3D bioprinting techniques in the field of CTE.

Applications of nanotechnology in 3D printed tissue engineering scaffolds

Tissue engineering is an interdisciplinary field that aims to combine life sciences and engineering to create therapies that regenerate functional tissue. Early work in tissue engineering mostly used materials as inert scaffolding structures, but research has shown that constructing scaffolds from biologically active materials can help with regeneration by enabling cell-scaffold interactions or release of factors that aid in regeneration. Three-dimensional (3D) printing is a promising technique for the fabrication of structurally intricate and compositionally complex tissue engineering scaffolds. Such scaffolds can be functionalized with techniques developed by nanotechnology research to further enhance their ability to stimulate regeneration and interact with cells. Nanotechnological components, nanoscale textures, and microscale/nanoscale printing can all be incorporated into the manufacture of 3D printed scaffolds. This review discusses recent advancements in the merging of nanotechnology with 3D printed tissue engineering scaffolds, with a focus on applications of nanoscale components, nanoscale texture, and innovative printing techniques and the effects observed in vitro and in vivo.

Recent advances in bioprinting technologies for engineering cardiac tissue

Annually increasing incidence of cardiac-related disorders and cardiac tissue's minimal regenerative capacity have motivated the researchers to explore effective therapeutic strategies. In the recent years, bioprinting technologies have witnessed a great wave of enthusiasm and have undergone steady advancements over a short period, opening the possibilities for recreating engineered functional cardiac tissue models for regenerative and diagnostic applications. With this perspective, the current review delineates recent developments in the sphere of engineered cardiac tissue fabrication, using traditional and advanced bioprinting strategies. The review also highlights different printing ink formulations, available cellular opportunities, and aspects of personalized medicines in the context of cardiac tissue engineering and bioprinting. On a concluding note, current challenges and prospects for further advancements are also discussed.

3D Bioprinted Cardiac Tissues and Devices for Tissue Maturation

Cardiovascular diseases are the leading cause of mortality worldwide. Given the limited endogenous regenerative capabilities of cardiac tissue, patient-specific anatomy, challenges in treatment options, and shortage of donor tissues for transplantation, there is an urgent need for novel approaches in cardiac tissue repair. 3D bioprinting is a technology based on additive manufacturing which allows for the design of precisely controlled and spatially organized structures, which could possibly lead to solutions in cardiac tissue repair. In this review, we describe the basic morphological and physiological specifics of the heart and cardiac tissues and introduce the readers to the fundamental principles underlying 3D printing technology and some of the materials/approaches which have been used to date for cardiac repair. By summarizing recent progress in 3D printing of cardiac tissue and valves with respect to the key features of cardiovascular tissue (such as contractility, conductivity, and vascularization), we highlight how 3D printing can facilitate surgical planning and provide custom-fit implants and properties that match those from the native heart. Finally, we also discuss the suitability of this technology in the design and fabrication of custom-made devices intended for the maturation of the cardiac tissue, a process that has been shown to increase the viability of implants. Altogether this review shows that 3D printing and bioprinting are versatile and highly modulative technologies with wide applications in cardiac regeneration and beyond.

Nano-Medicine in the Cardiovascular System

Nano-medicines that include nanoparticles, nanocomposites, small molecules, and exosomes represent new viable sources for future therapies for the dysfunction of cardiovascular system, as well as the other important organ systems. Nanomaterials possess special properties ranging from their intrinsic physicochemical properties, surface energy and surface topographies which can illicit advantageous cellular responses within the cardiovascular system, making them exceptionally valuable in future clinical translation applications. The success of nano-medicines as future cardiovascular theranostic agents requires a comprehensive understanding of the intersection between nanomaterial and the biomedical fields. In this review, we highlight some of the major types of nano-medicine systems that are currently being explored in the cardiac field. This review focusses on the major differences between the systems, and how these differences affect the specific therapeutic or diagnostic applications. The important concerns relevant to cardiac nano-medicines, including cellular responses, toxicity of the different nanomaterials, as well as cardio-protective and regenerative capabilities are discussed. In this review an overview of the current development of nano-medicines specific to the cardiac field is provided, discussing the diverse nature and applications of nanomaterials as therapeutic and diagnostic agents.

Additive Manufacturing of Polymer Materials: Progress, Promise and Challenges

The use of additive manufacturing (AM) has moved well beyond prototyping and has been established as a highly versatile manufacturing method with demonstrated potential to completely transform traditional manufacturing in the future. In this paper, a comprehensive review and critical analyses of the recent advances and achievements in the field of different AM processes for polymers, their composites and nanocomposites, elastomers and multi materials, shape memory polymers and thermo-responsive materials are presented. Moreover, their applications in different fields such as bio-medical, electronics, textiles, and aerospace industries are also discussed. We conclude the article with an account of further research needs and future perspectives of AM process with polymeric materials.

Modulating the Biomechanical Properties of Engineered Connective Tissues by Chitosan-Coated Multiwall Carbon Nanotubes

Background

Under certain conditions, the physiological repair of connective tissues might fail to restore the original structure and function. Optimized engineered connective tissues (ECTs) with biophysical properties adapted to the target tissue could be used as a substitution therapy. This study aimed to investigate the effect of ECT enforcement by a complex of multiwall carbon nanotubes with chitosan (C-MWCNT) to meet in vivo demands.

Materials and Methods

ECTs were constructed from human foreskin fibroblasts (HFF-1) in collagen type I and enriched with the three different percentages 0.025, 0.05 and 0.1% of C-MWCNT. Characterization of the physical properties was performed by biomechanical studies using unidirectional strain.

Results

Supplementation with 0.025% C-MWCNT moderately increased the tissue stiffness, reflected by Young’s modulus, compared to tissues without C-MWCNT. Supplementation of ECTs with 0.1% C-MWCNT reduced tissue contraction and increased the elasticity and the extensibility, reflected by the yield point and ultimate strain, respectively. Consequently, the ECTs with 0.1% C-MWCNT showed a higher resilience and toughness as control tissues. Fluorescence tissue imaging demonstrated the longitudinal alignment of all cells independent of the condition.

Conclusion

Supplementation with C-MWCNT can enhance the biophysical properties of ECTs, which could be advantageous for applications in connective tissue repair.

Recent advancements in cardiovascular bioprinting and bioprinted cardiac constructs

Three-dimensionally bioprinted cardiac constructs with biomimetic bioink helps to create native-equivalent cardiac tissues to treat patients with myocardial infarction.

The Electric-Field-Driven Fusion Jetting 3D Printing for Fabricating High Resolution Polylactic Acid/Multi-Walled Carbon Nanotube Composite Micro-Scale Structures

Existing 3D printing techniques are still facing the challenge of low resolution for fabricating polymer matrix composites, inhibiting the wide engineering applications for the biomedical engineering (biomimetic scaffolds), micro fuel cells, and micro-electronics. In order to achieve high resolution fabrication of polylactic acid (PLA)/multi-walled carbon nanotube (MWCNT) composites, this paper presents an electric-field-driven (EFD) fusion jetting 3D printing method by combining the mixing effect and material feeding of the micro-screw and the necking effect of Taylor cone by the EFD. The effects of main process parameters (the carbon loading, the voltage, the screw speed, and the printing speed) on the line width and the printing quality were studied and optimized. To demonstrate the printing capability of this proposed method, meshes with line width of 30 µm to 100 μm and 1 wt.% to 5 wt.% MWCNT for the application of conductive biomimetic scaffold and the anisotropic flexible meshes were prepared. The electrical properties were investigated to present the frequency dependence of the alternating current conductivity and the dielectric loss (tanδ), and the microstructures of printed structures demonstrated the uniformly dispersed MWCNT in PLA matrix. Therefore, it provides a new solution to fabricate micro-scale structures of composite materials, especially the 3D conductive biomimetic scaffolds.

Leveraging advances in chemistry to design biodegradable polymeric implants using chitosan and other biomaterials

The metamorphosis of biodegradable polymers in biomedical applications is an auspicious myriad of indagation. The utmost challenge in clinical conditions includes trauma, organs failure, soft and hard tissues, infection, cancer and inflammation, congenital disorders which are still not medicated efficiently. To overcome this bone of contention, proliferation in the concatenation of biodegradable materials for clinical applications has emerged as a silver bullet owing to eco-friendly, nontoxicity, exorbitant mechanical properties, cost efficiency, and degradability. Several bioimplants are designed and fabricated in a way to reabsorb or degrade inside the body after performing the specific function rather than eliminating the bioimplants. The objective of this comprehensive is to unfurl the anecdote of emerging biological polymers derived implants including silk, lignin, soy, collagen, gelatin, chitosan, alginate, starch, etc. by explicating the selection, fabrication, properties, and applications. Into the bargain, emphasis on the significant characteristics of current discernment and purview of nanotechnology integrated biopolymeric implants has also been expounded. This robust contrivance shed light on recent inclinations and evolution in tissue regeneration and targeting organs followed by precedency and fly in the ointment concerning biodegradable implants evolved by employing fringe benefits provided by 3D printing technology for building tissues or organs construct for implantation.

Biocompatible SWCNT Conductive Composites for Biomedical Applications

The efficiency of devices for biomedical applications, including tissue engineering and neuronal stimulation, heavily depends on their biocompatibility and performance level. Therefore, it is important to find adequate materials that meet the necessary requirements such as (i) being intrinsically compatible with biological systems, (ii) providing a sufficient electronic conductivity that promotes efficient signal transduction, (iii) having "soft" mechanical properties comparable to biological structures, and (iv) being degradable in physiological solution. We have developed organic conducting biocompatible single-walled carbon nanotubes (SWCNT) composites based on bovine serum albumin, carboxymethylcellulose, and acrylic polymer and investigated their properties, which are relevant for biomedical applications. This includes ζ-potential measurements, conductivity analyses, and SEM micrographs, the latter providing a local analysis of SWCNT distribution in the base material. We observed the development of the electrical conductivity of the SWCNT composites exposed to 1 mM KCl electrolyte for 40 days, representing a high stability of the samples. The conductivity of samples reaches 1300 S/m for 0.45 wt.% nanotubes. Moreover, we demonstrated the biocompatibility of the composites via cultivating fibroblast cell culture. Finally, we showed that composite coating results in the longer lifespan of cells on the surface. Overall, the SWCNT-based conductive composites might be a promising material for extended biomedical applications.

Carbon Nanomaterials for Electro-Active Structures: A Review

The use of electrically conductive materials to impart electrical properties to substrates for cell attachment proliferation and differentiation represents an important strategy in the field of tissue engineering. This paper discusses the concept of electro-active structures and their roles in tissue engineering, accelerating cell proliferation and differentiation, consequently leading to tissue regeneration. The most relevant carbon-based materials used to produce electro-active structures are presented, and their main advantages and limitations are discussed in detail. Particular emphasis is put on the electrically conductive property, material synthesis and their applications on tissue engineering. Different technologies, allowing the fabrication of two-dimensional and three-dimensional structures in a controlled way, are also presented. Finally, challenges for future research are highlighted. This review shows that electrical stimulation plays an important role in modulating the growth of different types of cells. As highlighted, carbon nanomaterials, especially graphene and carbon nanotubes, have great potential for fabricating electro-active structures due to their exceptional electrical and surface properties, opening new routes for more efficient tissue engineering approaches.

Nanomaterials for Cardiac Tissue Engineering

End stage heart failure is a major cause of death in the US. At present, organ transplant and left-ventricular assist devices remain the only viable treatments for these patients. Cardiac tissue engineering presents the possibility of a new option. Nanomaterials such as gold nanorods (AuNRs) and carbon nanotubes (CNTs) present unique properties that are beneficial for cardiac tissue engineering approaches. In particular, these nanomaterials can modulate electrical conductivity, hardness, and roughness of bulk materials to improve tissue functionality. Moreover, they can deliver bioactive cargo to affect cell phenotypes. This review covers recent advances in the use of nanomaterials for cardiac tissue engineering.

Bioprinting: From Tissue and Organ Development to in Vitro Models

Bioprinting techniques have been flourishing in the field of biofabrication with pronounced and exponential developments in the past years. Novel biomaterial inks used for the formation of bioinks have been developed, allowing the manufacturing of in vitro models and implants tested preclinically with a certain degree of success. Furthermore, incredible advances in cell biology, namely, in pluripotent stem cells, have also contributed to the latest milestones where more relevant tissues or organ-like constructs with a certain degree of functionality can already be obtained. These incredible strides have been possible with a multitude of multidisciplinary teams around the world, working to make bioprinted tissues and organs more relevant and functional. Yet, there is still a long way to go until these biofabricated constructs will be able to reach the clinics. In this review, we summarize the main bioprinting activities linking them to tissue and organ development and physiology. Most bioprinting approaches focus on mimicking fully matured tissues. Future bioprinting strategies might pursue earlier developmental stages of tissues and organs. The continuous convergence of the experts in the fields of material sciences, cell biology, engineering, and many other disciplines will gradually allow us to overcome the barriers identified on the demanding path toward manufacturing and adoption of tissue and organ replacements.

Carbon nanotubes and their polymeric composites: the applications in tissue engineering

Carbon nanotubes (CNTs), with unique graphitic structure, superior mechanical, electrical, optical and biological properties, has attracted more and more interests in biomedical applications, including gene/drug delivery, bioimaging, biosensor and tissue engineering. In this review, we focus on the role of CNTs and their polymeric composites in tissue engineering applications, with emphasis on their usages in the nerve, cardiac and bone tissue regenerations. The intrinsic natures of CNTs including their physical and chemical properties are first introduced, explaining the structure effects on CNTs electrical conductivity and various functionalization of CNTs to improve their hydrophobic characteristics. Biosafety issues of CNTs are also discussed in detail including the potential reasons to induce the toxicity and their potential strategies to minimise the toxicity effects. Several processing strategies including solution-based processing, polymerization, melt-based processing and grafting methods are presented to show the 2D/3D construct formations using the polymeric composite containing CNTs. For the sake of improving mechanical, electrical and biological properties and minimising the potential toxicity effects, recent advances using polymer/CNT composite the tissue engineering applications are displayed and they are mainly used in the neural tissue (to improve electrical conductivity and biological properties), cardiac tissue (to improve electrical, elastic properties and biological properties) and bone tissue (to improve mechanical properties and biological properties). Current limitations of CNTs in the tissue engineering are discussed and the corresponded future prospective are also provided. Overall, this review indicates that CNTs are promising “next-generation” materials for future biomedical applications.

Engineering Biomaterials to Guide Heart Cells for Matured Cardiac Tissue

The extracellular matrix (ECM) is needed to maintain the structural integrity of tissues and to mediate cellular dynamics. Its main components are fibrous proteins and glycosaminoglycans, which provide a suitable environment for biological functions. Thus, biomaterials with ECM-like properties have been extensively developed by modulating their key components and properties. In the field of cardiac tissue engineering, the use of biomaterials offers several advantages in that biophysical and biochemical cues can be designed to mediate cardiac cells, which is critical for maturation and regeneration. This suggests that understanding biomaterials and their use in vivo and in vitro is beneficial in terms of advancing cardiac engineering. The current review provides an overview of both natural and synthetic biomaterials and their use in cardiac engineering. In addition, we focus on different strategies to recapitulate the cardiac tissue in 2D and 3D approaches, which is an important step for the maturation of cardiac tissues toward regeneration of the adult heart.