4D Printing Applications in the Development of Smart Cardiovascular Implants

Printable Poly(3,4-ethylenedioxythiophene)-Based Conductive Patches for Cardiac Tissue Remodeling

Myocardial cardiopathy is one of the highest disease burdens worldwide. The damaged myocardium has little intrinsic repair ability, and as a result, the distorted muscle loses strength for contraction, producing arrhythmias and fainting, and entails a high risk of sudden death. Permanent implantable conductive hydrogels that can restore contraction strength and conductivity appear to be promising candidates for myocardium functional recovery. In this work, we present a printable cardiac hydrogel that can exert functional effects on networks of cardiac myocytes. The hydrogel matrix was designed from poly(vinyl alcohol) (PVA) dynamically cross-linked with gallic acid (GA) and the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT). The resulting patches exhibited excellent electrical conductivity, elasticity, and mechanical and contractile strengths, which are critical parameters for reinforcing weakened cardiac contraction and impulse propagation. Furthermore, the PVA-GA/PEDOT blend is suitable for direct ink writing via a melting extrusion. As a proof of concept, we have proven the efficiency of the patches in propagating the electrical signal in adult mouse cardiomyocytes through in vitro recordings of intracellular Ca2+ transients during cell stimulation. Finally, the patches were implanted in healthy mouse hearts to demonstrate their accommodation and biocompatibility. Magnetic resonance imaging revealed that the implants did not affect the essential functional parameters after 2 weeks, thus showing great potential for treating cardiomyopathies.

Patient-specific 3D in vitro modeling and fluid dynamic analysis of primary pulmonary vein stenosis

Introduction

Primary pulmonary vein stenosis (PVS) is a rare congenital heart disease that proves to be a clinical challenge due to the rapidly progressive disease course and high rates of treatment complications. PVS intervention is frequently faced with in-stent restenosis and persistent disease progression despite initial venous recanalization with balloon angioplasty or stenting. Alterations in wall shear stress (WSS) have been previously associated with neointimal hyperplasia and venous stenosis underlying PVS progression. Thus, the development of patient-specific three-dimensional (3D) in vitro models is needed to further investigate the biomechanical outcomes of endovascular and surgical interventions.

Methods

In this study, deidentified computed tomography images from three patients were segmented to generate perfusable phantom models of pulmonary veins before and after catheterization. These 3D reconstructions were 3D printed using a clear resin ink and used in a benchtop experimental setup. Computational fluid dynamic (CFD) analysis was performed on models in silico utilizing Doppler echocardiography data to represent the in vivo flow conditions at the inlets. Particle image velocimetry was conducted using the benchtop perfusion setup to analyze WSS and velocity profiles and the results were compared with those predicted by the CFD model.

Results

Our findings indicated areas of undesirable alterations in WSS before and after catheterization, in comparison with the published baseline levels in the healthy in vivo tissues that may lead to regional disease progression.

Discussion

The established patient-specific 3D in vitro models and the developed in vitro-in silico platform demonstrate great promise to refine interventional approaches and mitigate complications in treating patients with primary PVS.

Advancing Organoid Engineering for Tissue Regeneration and Biofunctional Reconstruction

Tissue damage and functional abnormalities in organs have become a considerable clinical challenge. Organoids are often applied as disease models and in drug discovery and screening. Indeed, several studies have shown that organoids are an important strategy for achieving tissue repair and biofunction reconstruction. In contrast to established stem cell therapies, organoids have high clinical relevance. However, conventional approaches have limited the application of organoids in clinical regenerative medicine. Engineered organoids might have the capacity to overcome these challenges. Bioengineering-a multidisciplinary field that applies engineering principles to biomedicine-has bridged the gap between engineering and medicine to promote human health. More specifically, bioengineering principles have been applied to organoids to accelerate their clinical translation. In this review, beginning with the basic concepts of organoids, we describe strategies for cultivating engineered organoids and discuss the multiple engineering modes to create conditions for breakthroughs in organoid research. Subsequently, studies on the application of engineered organoids in biofunction reconstruction and tissue repair are presented. Finally, we highlight the limitations and challenges hindering the utilization of engineered organoids in clinical applications. Future research will focus on cultivating engineered organoids using advanced bioengineering tools for personalized tissue repair and biofunction reconstruction.

Progress on a Novel, 3D-Printable Heart Valve Prosthesis

(1) Background: Polymeric heart valves are prostheses constructed out of flexible, synthetic materials to combine the advantageous hemodynamics of biological valves with the longevity of mechanical valves. This idea from the early days of heart valve prosthetics has experienced a renaissance in recent years due to advances in polymer science. Here, we present progress on a novel, 3D-printable aortic valve prosthesis, the TIPI valve, removing the foldable metal leaflet restrictor structure in its center. Our aim is to create a competitive alternative to current valve prostheses made from flexible polymers. (2) Methods: Three-dimensional (3D) prototypes were designed and subsequently printed in silicone. Hemodynamic performance was measured with an HKP 2.0 hemodynamic testing device using an aortic valve bioprosthesis (BP), a mechanical prosthesis (MP), and the previously published prototype (TIPI 2.2) as benchmarks. (3) Results: The latest prototype (TIPI 3.4) showed improved performance in terms of regurgitation fraction (TIPI 3.4: 15.2 ± 3.7%, TIPI 2.2: 36.6 ± 5.0%, BP: 8.8 ± 0.3%, MP: 13.2 ± 0.7%), systolic pressure gradient (TIPI 3.4: 11.0 ± 2.7 mmHg, TIPI 2.2: 12.8 ± 2.2 mmHg, BP: 8.2 ± 0.9 mmHg, MP: 10.5 ± 0.6 mmHg), and effective orifice area (EOA, TIPI 3.4: 1.39 cm2, TIPI 2.2: 1.28 cm2, BP: 1.58 cm2, MP: 1.38 cm2), which was equivalent to currently used aortic valve prostheses. (4) Conclusions: Removal of the central restrictor structure alleviated previous concerns about its potential thrombogenicity and significantly increased the area of unobstructed opening. The prototypes showed unidirectional leaflet movement and very promising performance characteristics within our testing setup. The resulting simplicity of the shape compared to other approaches for polymeric heart valves could be suitable not only for 3D printing, but also for fast and easy mass production using molds and modern, highly biocompatible polymers.

Incorporation of Controlled Release Systems Improves the Functionality of Biodegradable 3D Printed Cardiovascular Implants

New horizons in cardiovascular research are opened by using 3D printing for biodegradable implants. This additive manufacturing approach allows the design and fabrication of complex structures according to the patient's imaging data in an accurate, reproducible, cost-effective, and quick manner. Acellular cardiovascular implants produced from biodegradable materials have the potential to provide enough support for in situ tissue regeneration while gradually being replaced by neo-autologous tissue. Subsequently, they have the potential to prevent long-term complications. In this Review, we discuss the current status of 3D printing applications in the development of biodegradable cardiovascular implants with a focus on design, biomaterial selection, fabrication methods, and advantages of implantable controlled release systems. Moreover, we delve into the intricate challenges that accompany the clinical translation of these groundbreaking innovations, presenting a glimpse of potential solutions poised to enable the realization of these technologies in the realm of cardiovascular medicine.

A systematic review of the role of 4D printing in sustainable civil engineering solutions

This systematic review, not financially supported by any funding body, aims to synthesize the current knowledge on the applications, potential benefits, and challenges of 4D printing in civil engineering, with a focus on its role in sustainable solutions. Comprehensive searches were conducted in Scopus, Web of Science, and Google Scholar using related keywords. Articles that discussed 4D printing within civil engineering and construction contexts, encompassing both conceptual and empirical studies, were included. The findings suggest that 4D printing, with its time-responsive transformation feature, can enhance design freedom, improve structural performance, and increase environmental efficiency in construction. However, challenges persist in material performance, scalability, and cost. Despite these, ongoing advancements signal potential future developments that could widen the opportunities for large-scale applications of 4D printing in civil engineering. The potential use of renewable, bio-based materials could also lead to more sustainable construction practices. This review highlights the transformative potential of 4D printing, underlining the need for further research to fully leverage its capabilities and address current limitations. 4D printing emerges as a promising avenue for sustainable civil engineering solutions, offering a transformative approach that calls for continued exploration and development.

Application of 4D printing and bioprinting in cardiovascular tissue engineering

Cardiovascular diseases have remained the leading cause of death worldwide for the past 20 years. The current clinical therapeutic measures, including bypass surgery, stent implantation and pharmacotherapy, are not enough to repair the massive loss of cardiomyocytes after myocardial ischemia. Timely replenishment with functional myocardial tissue via biomedical engineering is the most direct and effective means to improve the prognosis and survival rate of patients. It is widely recognized that 4D printing technology introduces an additional dimension of time in comparison with traditional 3D printing. Additionally, in the context of 4D bioprinting, both the printed material and the resulting product are designed to be biocompatible, which will be the mainstream of bioprinting in the future. Thus, this review focuses on the application of 4D bioprinting in cardiovascular diseases, discusses the bottleneck of the development of 4D bioprinting, and finally looks forward to the future direction and prospect of this revolutionary technology.

4D Printing in Biomedical Engineering: Advancements, Challenges, and Future Directions

4D printing has emerged as a transformative technology in the field of biomedical engineering, offering the potential for dynamic, stimuli-responsive structures with applications in tissue engineering, drug delivery, medical devices, and diagnostics. This review paper provides a comprehensive analysis of the advancements, challenges, and future directions of 4D printing in biomedical engineering. We discuss the development of smart materials, including stimuli-responsive polymers, shape-memory materials, and bio-inks, as well as the various fabrication techniques employed, such as direct-write assembly, stereolithography, and multi-material jetting. Despite the promising advances, several challenges persist, including material limitations related to biocompatibility, mechanical properties, and degradation rates; fabrication complexities arising from the integration of multiple materials, resolution and accuracy, and scalability; and regulatory and ethical considerations surrounding safety and efficacy. As we explore the future directions for 4D printing, we emphasise the need for material innovations, fabrication advancements, and emerging applications such as personalised medicine, nanomedicine, and bioelectronic devices. Interdisciplinary research and collaboration between material science, biology, engineering, regulatory agencies, and industry are essential for overcoming challenges and realising the full potential of 4D printing in the biomedical engineering landscape.

Visible Light-Based 4D-Bioprinted Tissue Scaffold

Emerging four-dimensional (4D) printing strategies offer improved alternatives to conventional three-dimensional (3D)-bioprinted structures for better compliance and simplicity of application for tissue engineering. Little is reported on simple 3D-bioprinted structures prepared by digital light processing (DLP) that can change shape-to-complex constructs (4D bioprinting) in response to cell-friendly stimuli, such as hydration. In the current research work, a bioink consisting of a blend of gelatin methacryloyl (GelMA) and poly(ethylene glycol) dimethacrylate (PEGDM) with a photoinitiator and a photoabsorber was developed and printed by DLP-based 3D bioprinting operated with visible light (405 nm). The 3D-bioprinted constructs combined with differential cross-linking due to photoabsorber-induced light attenuation were leveraged to realize structural anisotropy, which led to rapid shape deformation (as low as ≈30 min) upon hydration. The sheet thickness influenced the degree of curvature, whereas the incorporation of angled strands provided control of the deformation of the 3D-printed structure. The 4D-bioprinted gels supported the viability and proliferation of cells. Overall, this study introduces a cytocompatible bioink formulation for 4D bioprinting to yield shape-morphing, cell-laden hydrogels for tissue engineering.

Evolving Coronary Stent Technologies - A Glimpse Into the Future

One of the most widely accepted forms of treatment for coronary artery disease (CAD) is the implementation of stents into the vessel. This area of research is constantly evolving, ranging from bare-metal stents through drug-eluting stents and, more recently, approaching bioresorbable stents and polymer-free stents. This article reviews the evolution of all these devices and emphasizes how they might be further evolved to provide an optimal coronary stent and overcome unsolved challenges in stent development. We thoroughly evaluated a number of published studies in order to advance coronary stent technologies. Additionally, we looked for various literature that highlighted the inadequacies of the coronary stents that are currently available and how they might be modified to create the optimum coronary stent. Coronary stents have significantly improved clinical outcomes in interventional cardiology, but there are still a number of drawbacks, including an persisted risk of thrombosis due to endothelial injury and in-stent restenosis. Gene eluting stents (GES) and customized coronary stents with self-reporting stent sensors are appealing alternatives to existing stent approaches. Considering the adequacy of these gene eluting stents (GES), customized coronary stents produced by novel 4D printing technologies and integrated self-reporting stent sensors should be assumed for anticipating future advancements to optimal coronary stent devices; however, more interventional evidence is required to determine the future prospects of these stent innovations.

Smart biomaterials: From 3D printing to 4D bioprinting

This century is blessed with enhanced medical facilities on the grounds of the development of smart biomaterials. The rise of the four-dimensional (4D) bioprinting technology is a shining example. Using inert biomaterials as the bioinks for the three-dimensional (3D) printing process, static objects that might not be able to mimic the dynamic nature of tissues would be fabricated; by contrast, 4D bioprinting can be used for the fabrication of stimuli-responsive cell-laden structures that can evolve with time and enable engineered tissues to undergo morphological changes in a pre-planned way. For all the aptitude of 4D bioprinting technology in tissue engineering, it is imperative to select suitable stimuli-responsive biomaterials with cell-supporting functionalities and responsiveness; as a result, in this article, recent advances and challenges in smart biomaterials for 4D bioprinting are briefly discussed. An overview perspective concerning the latest developments in 4D-bioprinting is also provided.