Surface functionalization of polyurethane scaffolds mimicking the myocardial microenvironment to support cardiac primitive cells

Double-crosslinkable poly(urethane)-based hydrogels relying on supramolecular interactions and light-initiated polymerization: promising tools for advanced applications in drug delivery

Physical and chemical hydrogels are promising platforms for tissue engineering/regenerative medicine (TERM). In particular, physical hydrogels are suitable for use in the design of drug delivery systems owing to their reversibility and responsiveness to applied stimuli and external environment. Alternatively, the use of chemical hydrogels represents a better strategy to produce stable 3D constructs in the TERM field. In this work, these two strategies were combined to develop multi-functional formulations integrating both drug delivery potential and TERM approaches in a single device. Specifically, a novel photo-sensitive poly(ether urethane) (PEU) was developed to form supramolecular networks with α-cyclodextrins (α-CDs). The PEU was successfully synthesized using Poloxamer® 407, 1,6-diisocyanatohexane and 2-hydroxyethyl methacrylate, as assessed by infrared spectroscopy, size exclusion chromatography and proton nuclear magnetic resonance (1H NMR) spectroscopy. Subsequently, PEU thermo-responsiveness was characterized through critical micelle temperature evaluation and dynamic light scattering analyses, which suggested the achievement of a good balance between molecular mass and overall hydrophobicity. Consequently, the formation of supramolecular domains with α-CDs was demonstrated through X-ray diffraction and 1H NMR spectroscopy. Supramolecular hydrogels with remarkably fast gelation kinetics (i.e., few minutes) were designed using a low PEU concentration (≤5% w/v). All formulations were found to be cytocompatible according to the ISO 10993-5 regulation. Notably, the hydrogels were observed to possess mechanical properties and self-healing ability, according to rheological tests, and their fast photo-crosslinking was evidenced (<60 s) by photo-rheology. A high curcumin payload (570 μg mL-1) was encapsulated in the hydrogels, which was released with highly tunable and progressive kinetics in a physiological-simulated environment for up to 5 weeks. Finally, a preliminary evaluation of hydrogel extrudability was performed using an extrusion-based bioprinter, obtaining 3D-printed structures showing good morphological fidelity to the original design. Overall, the developed hydrogel platform showed promising properties for application in the emerging field of regenerative pharmacology as (i) easily injectable drug-loaded formulations suitable for post-application stabilization through light irradiation, and (ii) biomaterial inks for the fabrication of patient-specific drug-loaded patches.

Reduced Graphene-Oxide-Doped Elastic Biodegradable Polyurethane Fibers for Cardiomyocyte Maturation

Conductive biomaterials offer promising solutions to enhance the maturity of cultured cardiomyocytes. While the conventional culture of cardiomyocytes on nonconductive materials leads to more immature characteristics, conductive microenvironments have the potential to support sarcomere development, gap junction formation, and beating of cardiomyocytes in vitro. In this study, we systematically investigated the behaviors of cardiomyocytes on aligned electrospun fibrous membranes composed of elastic and biodegradable polyurethane (PU) doped with varying concentrations of reduced graphene oxide (rGO). Compared to PU and PU-4%rGO membranes, the PU-10%rGO membrane exhibited the highest conductivity, approaching levels close to those of native heart tissue. The PU-rGO membranes retained anisotropic viscoelastic behavior similar to that of the porcine left ventricle and a superior tensile strength. Neonatal rat cardiomyocytes (NRCMs) and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) on the PU-rGO membranes displayed enhanced maturation with cell alignment and enhanced sarcomere structure and gap junction formation with PU-10%rGO having the most improved sarcomere structure and CX-43 presence. hiPSC-CMs on the PU-rGO membranes exhibited a uniform and synchronous beating pattern compared with that on PU membranes. Overall, PU-10%rGO exhibited the best performance for cardiomyocyte maturation. The conductive PU-rGO membranes provide a promising matrix for in vitro cardiomyocyte culture with promoted cell maturation/functionality and the potential for cardiac disease treatment.

Three-Dimensional Microfibrous Scaffold with Aligned Topography Produced via a Combination of Melt-Extrusion Additive Manufacturing and Porogen Leaching for In Vitro Skeletal Muscle Modeling

Skeletal muscle tissue (SMT) has a highly hierarchical and anisotropic morphology, featuring aligned and parallel structures at multiple levels. Various factors, including trauma and disease conditions, can compromise the functionality of skeletal muscle. The in vitro modeling of SMT represents a useful tool for testing novel drugs and therapies. The successful replication of SMT native morphology demands scaffolds with an aligned anisotropic 3D architecture. In this work, a 3D PCL fibrous scaffold with aligned morphology was developed through the synergistic combination of Melt-Extrusion Additive Manufacturing (MEAM) and porogen leaching, utilizing PCL as the bulk material and PEG as the porogen. PCL/PEG blends with different polymer ratios (60/40, 50/50, 40/60) were produced and characterized through a DSC analysis. The MEAM process parameters and porogen leaching in bi-distilled water allowed for the development of a micrometric anisotropic fibrous structure with fiber diameters ranging from 10 to 100 µm, depending on PCL/PEG blend ratios. The fibrous scaffolds were coated with Gelatin type A to achieve a biomimetic coating for an in vitro cell culture and mechanically characterized via AFM. The 40/60 PCL/PEG scaffolds yielded the most homogeneous and smallest fibers and the greatest physiological stiffness. In vitro cell culture studies were performed by seeding C2C12 cells onto a selected scaffold, enabling their attachment, alignment, and myotube formation along the PCL fibers during a 14-day culture period. The resultant anisotropic scaffold morphology promoted SMT-like cell conformation, establishing a versatile platform for developing in vitro models of tissues with anisotropic morphology.

How to fix a broken heart-designing biofunctional cues for effective, environmentally-friendly cardiac tissue engineering

Cardiovascular diseases bear strong socioeconomic and ecological impact on the worldwide healthcare system. A large consumption of goods, use of polymer-based cardiovascular biomaterials, and long hospitalization times add up to an extensive carbon footprint on the environment often turning out to be ineffective at healing such cardiovascular diseases. On the other hand, cardiac cell toxicity is among the most severe but common side effect of drugs used to treat numerous diseases from COVID-19 to diabetes, often resulting in the withdrawal of such pharmaceuticals from the market. Currently, most patients that have suffered from cardiovascular disease will never fully recover. All of these factors further contribute to the extensive negative toll pharmaceutical, biotechnological, and biomedical companies have on the environment. Hence, there is a dire need to develop new environmentally-friendly strategies that on the one hand would promise cardiac tissue regeneration after damage and on the other hand would offer solutions for the fast screening of drugs to ensure that they do not cause cardiovascular toxicity. Importantly, both require one thing-a mature, functioning cardiac tissue that can be fabricated in a fast, reliable, and repeatable manner from environmentally friendly biomaterials in the lab. This is not an easy task to complete as numerous approaches have been undertaken, separately and combined, to achieve it. This review gathers such strategies and provides insights into which succeed or fail and what is needed for the field of environmentally-friendly cardiac tissue engineering to prosper.

Construction of cardiac fibrosis for biomedical research

Cardiac remodeling is critical for effective tissue recuperation, nevertheless, excessive formation and deposition of extracellular matrix components can result in the onset of cardiac fibrosis. Despite the emergence of novel therapies, there are still no lifelong therapeutic solutions for this issue. Understanding the detrimental cardiac remodeling may aid in the development of innovative treatment strategies to prevent or reverse fibrotic alterations in the heart. Further combining the latest understanding of disease pathogenesis with cardiac tissue engineering has provided the conversion of basic laboratory studies into the therapy of cardiac fibrosis patients as an increasingly viable prospect. This review presents the current main mechanisms and the potential tissue engineering of cardiac fibrosis. Approaches using biomedical materials-based cardiac constructions are reviewed to consider key issues for simulating in vitro cardiac fibrosis, outlining a future perspective for preclinical applications.

Biomimetic design of bioartificial scaffolds for the in vitro modelling of human cardiac fibrosis

In vitro models of pathological cardiac tissue have attracted interest as predictive platforms for preclinical validation of therapies. However, models reproducing specific pathological features, such as cardiac fibrosis size (i.e., thickness and width) and stage of development are missing. This research was aimed at engineering 2D and 3D models of early-stage post-infarct fibrotic tissue (i.e., characterized by non-aligned tissue organization) on bioartificial scaffolds with biomimetic composition, design, and surface stiffness. 2D scaffolds with random nanofibrous structure and 3D scaffolds with 150 µm square-meshed architecture were fabricated from polycaprolactone, surface-grafted with gelatin by mussel-inspired approach and coated with cardiac extracellular matrix (ECM) by 3 weeks culture of human cardiac fibroblasts. Scaffold physicochemical properties were thoroughly investigated. AFM analysis of scaffolds in wet state, before cell culture, confirmed their close surface stiffness to human cardiac fibrotic tissue. Following 3 weeks culture, biomimetic biophysical and biochemical scaffold properties triggered the activation of myofibroblast phenotype. Upon decellularization, immunostaining, SEM and two-photon excitation fluorescence microscopy showed homogeneous decoration of both 2D and 3D scaffolds with cardiac ECM. The versatility of the approach was demonstrated by culturing ventricular or atrial cardiac fibroblasts on scaffolds, thus suggesting the possibility to use the same scaffold platforms to model both ventricular and atrial cardiac fibrosis. In the future, herein developed in vitro models of cardiac fibrotic tissue, reproducing specific pathological features, will be exploited for a fine preclinical tuning of therapies.

Angiogenic stem cell delivery platform to augment post-infarction neovasculature and reverse ventricular remodeling

Many cell-based therapies are challenged by the poor localization of introduced cells and the use of biomaterial scaffolds with questionable biocompatibility or bio-functionality. Endothelial progenitor cells (EPCs), a popular cell type used in cell-based therapies due to their robust angiogenic potential, are limited in their therapeutic capacity to develop into mature vasculature. Here, we demonstrate a joint delivery of human-derived endothelial progenitor cells (EPC) and smooth muscle cells (SMC) as a scaffold-free, bi-level cell sheet platform to improve ventricular remodeling and function in an athymic rat model of myocardial infarction. The transplanted bi-level cell sheet on the ischemic heart provides a biomimetic microenvironment and improved cell-cell communication, enhancing cell engraftment and angiogenesis, thereby improving ventricular remodeling. Notably, the increased density of vessel-like structures and upregulation of biological adhesion and vasculature developmental genes, such as Cxcl12 and Notch3, particularly in the ischemic border zone myocardium, were observed following cell sheet transplantation. We provide compelling evidence that this SMC-EPC bi-level cell sheet construct can be a promising therapy to repair ischemic cardiomyopathy.

Rational design of biodegradable thermoplastic polyurethanes for tissue repair

As a type of elastomeric polymers, non-degradable polyurethanes (PUs) have a long history of being used in clinics, whereas biodegradable PUs have been developed in recent decades, primarily for tissue repair and regeneration. Biodegradable thermoplastic (linear) PUs are soft and elastic polymeric biomaterials with high mechanical strength, which mimics the mechanical properties of soft and elastic tissues. Therefore, biodegradable thermoplastic polyurethanes are promising scaffolding materials for soft and elastic tissue repair and regeneration. Generally, PUs are synthesized by linking three types of changeable blocks: diisocyanates, diols, and chain extenders. Alternating the combination of these three blocks can finely tailor the physio-chemical properties and generate new functional PUs. These PUs have excellent processing flexibilities and can be fabricated into three-dimensional (3D) constructs using conventional and/or advanced technologies, which is a great advantage compared with cross-linked thermoset elastomers. Additionally, they can be combined with biomolecules to incorporate desired bioactivities to broaden their biomedical applications. In this review, we comprehensively summarized the synthesis, structures, and properties of biodegradable thermoplastic PUs, and introduced their multiple applications in tissue repair and regeneration. A whole picture of their design and applications along with discussions and perspectives of future directions would provide theoretical and technical supports to inspire new PU development and novel applications.

Human Cardiac Progenitor Cell-Derived Extracellular Vesicles Exhibit Promising Potential for Supporting Cardiac Repair in Vitro

Although human Cardiac Progenitor Cells (hCPCs) are not retained by host myocardium they still improve cardiac function when injected into ischemic heart. Emerging evidence supports the hypothesis that hCPC beneficial effects are induced by paracrine action on resident cells. Extracellular vesicles (EVs) are an intriguing mechanism of cell communication based on the transport and transfer of peptides, lipids, and nucleic acids that have the potential to modulate signaling pathways, cell growth, migration, and proliferation of recipient cells. We hypothesize that EVs are involved in the paracrine effects elicited by hCPCs and held accountable for the response of the infarcted myocardium to hCPC-based cell therapy. To test this theory, we collected EVs released by hCPCs isolated from healthy myocardium and evaluated the effects they elicited when administered to resident hCPC and cardiac fibroblasts (CFs) isolated from patients with post-ischemic end-stage heart failure. Evidence emerging from our study indicated that hCPC-derived EVs impacted upon proliferation and survival of hCPCs residing in the ischemic heart and regulated the synthesis and deposition of extracellular-matrix by CFs. These findings suggest that beneficial effects exerted by hCPC injection are, at least to some extent, ascribable to the delivery of signals conveyed by EVs.

From Soft to Hard Biomimetic Materials: Tuning Micro/Nano-Architecture of Scaffolds for Tissue Regeneration

Failure of tissues and organs resulting from degenerative diseases or trauma has caused huge economic and health concerns around the world. Tissue engineering represents the only possibility to revert this scenario owing to its potential to regenerate or replace damaged tissues and organs. In a regeneration strategy, biomaterials play a key role promoting new tissue formation by providing adequate space for cell accommodation and appropriate biochemical and biophysical cues to support cell proliferation and differentiation. Among other physical cues, the architectural features of the biomaterial as a kind of instructive stimuli can influence cellular behaviors and guide cells towards a specific tissue organization. Thus, the optimization of biomaterial micro/nano architecture, through different manufacturing techniques, is a crucial strategy for a successful regenerative therapy. Over the last decades, many micro/nanostructured biomaterials have been developed to mimic the defined structure of ECM of various soft and hard tissues. This review intends to provide an overview of the relevant studies on micro/nanostructured scaffolds created for soft and hard tissue regeneration and highlights their biological effects, with a particular focus on striated muscle, cartilage, and bone tissue engineering applications.

Use of Polyesters in Fused Deposition Modeling for Biomedical Applications

In recent years, 3D printing techniques experienced a growing interest in several sectors, including the biomedical one. Their main advantage resides in the possibility to obtain complex and personalized structures in a cost-effective way impossible to achieve with traditional production methods. This is especially true for Fused Deposition Modeling (FDM), one of the most diffused 3D printing methods. The easy customization of the final products' geometry, composition and physico-chemical properties is particularly interesting for the increasingly personalized approach adopted in modern medicine. Thermoplastic polymers are the preferred choice for FDM applications, and a wide selection of biocompatible and biodegradable materials is available to this aim. Moreover, these polymers can also be easily modified before and after printing to better suit the body environment and the mechanical properties of biological tissues. This review focuses on the use of thermoplastic aliphatic polyesters for FDM applications in the biomedical field. In detail, the use of poly(ε-caprolactone), poly(lactic acid), poly(lactic-co-glycolic acid), poly(hydroxyalkanoate)s, thermo-plastic poly(ester urethane)s and their blends has been thoroughly surveyed, with particular attention to their main features, applicability and workability. The state-of-the-art is presented and current challenges in integrating the additive manufacturing technology in the medical practice are discussed. This article is protected by copyright. All rights reserved.

Surface Functionalization of Ureteral Stents-Based Polyurethane: Engineering Antibacterial Coatings

Bacterial colonization of polyurethane (PU) ureteral stents usually leads to severe and challenging clinical complications. As such, there is an increasing demand for an effective response to this unmet medical challenge. In this study, we offer a strategy based on the functionalization of PU stents with chitosan-fatty acid (CS-FA) derivatives to prevent bacterial colonization. Three different fatty acids (FAs), namely stearic acid (SA), oleic acid (OA), and linoleic acid (LinA), were successfully grafted onto chitosan (CS) polymeric chains. Afterwards, CS-FA derivatives-based solutions were coated on the surface of PU stents. The biological performance of the modified PU stents was evaluated against the L929 cell line, confirming negligible cytotoxicity of the developed coating formulations. The antibacterial potential of coated PU stents was also evaluated against several microorganisms. The obtained data indicate that the base material already presents an adequate performance against Staphylococcus aureus, which slightly improved with the coating. However, the performance of the PU stents against Gram-negative bacteria was markedly increased with the surface functionalization approach herein used. As a result, this study reveals the potential use of CS-FA derivatives for surface functionalization of ureteral PU stents and allows for conjecture on its successful application in other biomedical devices.

Photo-oxidative degradation of polyacids derived ceria nanoparticle modulation for chemical mechanical polishing

The effects of photo-oxidative degradation of polyacids at various concentrations and with different durations of ultraviolet (UV) irradiation on the photo-reduction of ceria nanoparticles were investigated. The effect of UV-treated ceria on the performance of chemical mechanical polishing (CMP) for the dielectric layer was also evaluated. When the polyacids were exposed to UV light, they underwent photo-oxidation with consumption of the dissolved oxygen in slurry. UV-treated ceria particles formed oxygen vacancies by absorbing photon energy, resulting in increased Ce³⁺ ions concentration on the surface, and when the oxygen level of the solution was lowered by the photo-oxidation of polymers, the formation of Ce³⁺ ions was promoted from 14.2 to 36.5%. Furthermore, chain scissions of polymers occurred during the oxidation process, and polyacids with lower molecular weights were found to be effective in ceria particle dispersion in terms of the decrease in the mean diameter and size distribution maintaining under 0.1 of polydispersity index. With increasing polyacid concentration and UV irradiation time, the Ce³⁺ concentration and the dispersity of ceria both increased due to the photo-oxidative degradation of the polymer; this enhanced the CMP performance in terms of 87% improved material removal rate and 48% lowered wafer surface roughness.

Custom-Made Poly(urethane) Coatings Improve the Mechanical Properties of Bioactive Glass Scaffolds Designed for Bone Tissue Engineering

The replication method is a widely used technique to produce bioactive glass (BG) scaffolds mimicking trabecular bone. However, these scaffolds usually exhibit poor mechanical reliability and fast degradation, which can be improved by coating them with a polymer. In this work, we proposed the use of custom-made poly(urethane)s (PURs) as coating materials for 45S5 Bioglass®-based scaffolds. In detail, BG scaffolds were dip-coated with two PURs differing in their soft segment (poly(ε-caprolactone) or poly(ε-caprolactone)/poly(ethylene glycol) 70/30 w/w) (PCL-PUR and PCL/PEG-PUR) or PCL (control). PUR-coated scaffolds exhibited biocompatibility, high porosity (ca. 91%), and improved mechanical properties compared to BG scaffolds (2-3 fold higher compressive strength). Interestingly, in the case of PCL-PUR, compressive strength significantly increased by coating BG scaffolds with an amount of polymer approx. 40% lower compared to PCL/PEG-PUR- and PCL-coated scaffolds. On the other hand, PEG presence within PCL/PEG-PUR resulted in a fast decrease in mechanical reliability in an aqueous environment. PURs represent promising coating materials for BG scaffolds, with the additional pros of being ad-hoc customized in their physico-chemical properties. Moreover, PUR-based coatings exhibited high adherence to the BG surface, probably because of the formation of hydrogen bonds between PUR N-H groups and BG surface functionalities, which were not formed when PCL was used.

Polymeric Biomaterials for the Treatment of Cardiac Post-Infarction Injuries

Cardiac regeneration aims to reconstruct the heart contractile mass, preventing the organ from a progressive functional deterioration, by delivering pro-regenerative cells, drugs, or growth factors to the site of injury. In recent years, scientific research focused the attention on tissue engineering for the regeneration of cardiac infarct tissue, and biomaterials able to anatomically and physiologically adapt to the heart muscle have been proposed as valuable tools for this purpose, providing the cells with the stimuli necessary to initiate a complete regenerative process. An ideal biomaterial for cardiac tissue regeneration should have a positive influence on the biomechanical, biochemical, and biological properties of tissues and cells; perfectly reflect the morphology and functionality of the native myocardium; and be mechanically stable, with a suitable thickness. Among others, engineered hydrogels, three-dimensional polymeric systems made from synthetic and natural biomaterials, have attracted much interest for cardiac post-infarction therapy. In addition, biocompatible nanosystems, and polymeric nanoparticles in particular, have been explored in preclinical studies as drug delivery and tissue engineering platforms for the treatment of cardiovascular diseases. This review focused on the most employed natural and synthetic biomaterials in cardiac regeneration, paying particular attention to the contribution of Italian research groups in this field, the fabrication techniques, and the current status of the clinical trials.

Designing Multifunctional Devices for Regenerative Pharmacology Based on 3D Scaffolds, Drug-Loaded Nanoparticles, and Thermosensitive Hydrogels: A Proof-of-Concept Study

Regenerative pharmacology combines tissue engineering/regenerative medicine (TERM) with drug delivery with the aim to improve the outcomes of traditional TERM approaches. In this work, we aimed to design a multicomponent TERM platform comprising a three-dimensional scaffold, a thermosensitive hydrogel, and drug-loaded nanoparticles. We used a thermally induced phase separation method to obtain scaffolds with anisotropic mechanical properties, suitable for soft tissue engineering. A thermosensitive hydrogel was developed using a Poloxamer^® 407-based poly(urethane) to embed curcumin-loaded nanoparticles, obtained by the single emulsion nanoprecipitation method. We found that encapsulated curcumin could retain its antioxidant activity and that embedding nanoparticles within the hydrogel did not affect the hydrogel gelation kinetics nor the possibility to progressively release the drug. The porous scaffold was easily loaded with the hydrogel, resulting in significantly enhanced (4-fold higher) absorption of a model molecule of nutrients (fluorescein isothiocyanate dextran 4kDa) from the surrounding environment compared to pristine scaffold. The developed platform could thus represent a valuable alternative in the treatment of many pathologies affecting soft tissues, by concurrently exploiting the therapeutic effects of drugs, with the 3D framework acting as a physical support for tissue regeneration and the cell-friendly environment represented by the hydrogel.

3D-Printed Objects for Multipurpose Applications

3D printing is a popular nonconventional manufacturing technique used to print 3D objects by using conventional and nonconventional materials. The application and uses of 3D printing are rapidly increasing in each dimension of the engineering and medical sectors. This article overviews the multipurpose applications of 3D printing based on current research. In the beginning, various popular methods including fused deposition method, stereolithography 3D printing method, powder bed fusion method, digital light processing method, and metal transfer dynamic method used in 3D printing are discussed. Popular materials utilized randomly in printing techniques such as hydrogel, ABS, steel, silver, and epoxy are overviewed. Engineering applications under the current development of the printing technique which include electrode, 4D printing technique, twisting object, photosensitive polymer, and engines are focused. Printing of medical equipment including artificial tissues, scaffolds, bioprinted model, prostheses, surgical instruments, COVID-19, skull, and heart is of major focus. Characterization techniques of the printed 3D products are mentioned. In addition, potential challenges and future prospects are evaluated based on the current scenario. This review article will work as a masterpiece for the researchers interested to work in this field.

Biomaterial-directed cell behavior for tissue engineering

Successful tissue regeneration strategies focus on the use of novel biomaterials, structures, and a variety of cues to control cell behavior and promote regeneration. Studies discovered how biomaterial/ structure cues in the form of biomaterial chemistry, material stiffness, surface topography, pore, and degradation properties play an important role in controlling cellular events in the contest of in vitro and in vivo tissue regeneration. Advanced biomaterials structures and strategies are developed to focus on the delivery of bioactive factors, such as proteins, peptides, and even small molecules to influence cell behavior and regeneration. The present article is an effort to summarize important findings and further discuss biomaterial strategies to influence and control cell behavior directly via physical and chemical cues. This article also touches on various modern methods in biomaterials processing to include bioactive factors as signaling cues to program cell behavior for tissue engineering and regenerative medicine.

PLGA Membranes Functionalized with Gelatin through Biomimetic Mussel-Inspired Strategy

Electrospun membranes have been widely used as scaffolds for soft tissue engineering due to their extracellular matrix-like structure. A mussel-inspired coating approach based on 3,4-dihydroxy-DL-phenylalanine (DOPA) polymerization was proposed to graft gelatin (G) onto poly(lactic-co-glycolic) acid (PLGA) electrospun membranes. PolyDOPA coating allowed grafting of gelatin to PLGA fibers without affecting their bulk characteristics, such as molecular weight and thermal properties. PLGA electrospun membranes were dipped in a DOPA solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 7 h and then incubated in G solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 16 h. PLGA fibers had an average diameter of 1.37 ± 0.23 µm. Quartz crystal microbalance with dissipation technique (QCM-D) analysis was performed to monitor DOPA polymerization over time: after 7 h the amount of deposited polyDOPA was 71 ng/cm2. After polyDOPA surface functionalization, which was, also revealed by Raman spectroscopy, PLGA membranes maintained their fibrous morphology, however the fiber size and junction number increased. Successful functionalization with G was demonstrated by FTIR-ATR spectra, which showed the presence of G adsorption bands at 1653 cm-1 (Amide I) and 1544 cm-1 (Amide II) after G grafting, and by the Kaiser Test, which revealed a higher amount of amino groups for G functionalized membranes. Finally, the biocompatibility of the developed substrates and their ability to induce cell growth was assessed using Neonatal Normal Human Dermal Fibroblasts.

A Concise Review on Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Personalized Regenerative Medicine

The induced pluripotent stem cells (iPSCs) are derived from somatic cells by using reprogramming factors such as Oct4, Sox2, Klf4, and c-Myc (OSKM) or Oct4, Sox2, Nanog and Lin28 (OSNL). They resemble embryonic stem cells (ESCs) and have the ability to differentiate into cell lineage of all three germ-layer, including cardiomyocytes (CMs). The CMs can be generated from iPSCs by inducing embryoid bodies (EBs) formation and treatment with activin A, bone morphogenic protein 4 (BMP4), and inhibitors of Wnt signaling. However, these iPSC-derived CMs are a heterogeneous population of cells and require purification and maturation to mimic the in vivo CMs. The matured CMs can be used for various therapeutic purposes in regenerative medicine by cardiomyoplasty or through the development of tissue-engineered cardiac patches. In recent years, significant advancements have been made in the isolation of iPSC and their differentiation, purification, and maturation into clinically usable CMs. Newer small molecules have also been identified to substitute the reprogramming factors for iPSC generation as well as for direct differentiation of somatic cells into CMs without an intermediary pluripotent state. This review provides a concise update on the generation of iPSC-derived CMs and their application in personalized cardiac regenerative medicine. It also discusses the current limitations and challenges in the application of iPSC-derived CMs. Graphical abstract.

Recent advances in tissue engineering scaffolds based on polyurethane and modified polyurethane

Organ repair, regeneration, and transplantation are constantly in demand due to various acute, chronic, congenital, and infectious diseases. Apart from traditional remedies, tissue engineering (TE) is among the most effective methods for the repair of damaged tissues via merging the cells, growth factors, and scaffolds. With regards to TE scaffold fabrication technology, polyurethane (PU), a high-performance medical grade synthetic polymer and bioactive material has gained significant attention. PU possesses exclusive biocompatibility, biodegradability, and modifiable chemical, mechanical and thermal properties, owing to its unique structure-properties relationship. During the past few decades, PU TE scaffold bioactive properties have been incorporated or enhanced with biodegradable, electroactive, surface-functionalised, ayurvedic products, ceramics, glass, growth factors, metals, and natural polymers, resulting in the formation of modified polyurethanes (MPUs). This review focuses on the recent advances of PU/MPU scaffolds, especially on the biomedical applications in soft and hard tissue engineering and regenerative medicine. The scientific issues with regards to the PU/MPU scaffolds, such as biodegradation, electroactivity, surface functionalisation, and incorporation of active moieties are also highlighted along with some suggestions for future work.

Why Polyurethanes Have Been Used in the Manufacture and Design of Cardiovascular Devices: A Systematic Review

We conducted a systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to ascertain why polyurethanes (PUs) have been used in the manufacture and design of cardiovascular devices. A complete database search was performed with PubMed, Scopus, and Web of Science as the information sources. The search period ranged from 1 January 2005 to 31 December 2019. We recovered 1552 articles in the first stage. After the duplicate selection and extraction procedures, a total of 21 papers were included in the analysis. We concluded that polyurethanes are being applied in medical devices because they have the capability to tolerate contractile forces that originate during the cardiac cycle without undergoing plastic deformation or failure, and the capability to imitate the behaviors of different tissues. Studies have reported that polyurethanes cause severe problems when applied in blood-contacting devices that are implanted for long periods. However, the chemical compositions and surface characteristics of polyurethanes can be modified to improve their mechanical properties, blood compatibility, and endothelial cell adhesion, and to reduce their protein adhesion. These modifications enable the use of polyurethanes in the manufacture and design of cardiovascular devices.

Extracellular matrix-based biomaterials for cardiac regeneration and repair

The spectrum of ischemic heart diseases, encompassing acute myocardial infarction to heart failure, represents the leading cause of death worldwide. Although extensive progress in cardiovascular diagnoses and therapy has been made, the prevalence of the disease continues to increase. Cardiac regeneration has a promising perspective for the therapy of heart failure. Recently, extracellular matrix (ECM) has been shown to play an important role in cardiac regeneration and repair after cardiac injury. There is also evidence that the ECM could be directly used as a drug to promote cardiomyocyte proliferation and cardiac regeneration. Increasing evidence supports that applying ECM biomaterials to maintain heart function recovery is an important approach to apply the concept of cardiac regenerative medicine to clinical practice in the future. Here, we will introduce the essential role of cardiac ECM in cardiac regeneration and summarize the approaches of delivering ECM biomaterials to promote cardiac repair in this review.

Azido-Functionalized Polyurethane Designed for Making Tunable Elastomers by Click Chemistry

Polyurethane is an important biomaterial with wide applications in biomedical engineering. Here, we report a new method to make an azido-functionalized polyurethane prepolymer with no need of postmodification. This prepolymer can easily form stable porous elastomers through click chemistry for cross-linking, instead of using a toxic polyisocyanate. The mechanical properties can be modulated by simply adjusting either the prepolymer concentrations or azido/alkyne ratios for cross-linking. Young's modulus therefore varies from 0.52 to 2.02 MPa for the porous elastomers. When the azido-functionalized polyurethane elastomer is made with a compact structure, Young's modulus increases up to 28.8 MPa at 0-15% strain. The strain at break reaches 150% that is comparable to the commercially resourced Nylon-12. Both the porous and compact elastomers could undergo reversible elastic deformations for at least 200 and 1000 cycles, respectively, within 20% strain without failure. The material showed a considerable stability against erosion in a basic solution. In vivo biocompatibility study demonstrated no degradation by subcutaneous implantation in mice over 2 months. The implant induced only a mild inflammatory response and fibrotic capsule. This material might be useful to make elastomeric components of biomedical devices.

Current advances in biodegradable synthetic polymer based cardiac patches

The number of people affected by heart disease such as coronary artery disease and myocardial infarction increases at an alarming rate each year. Currently, the methods to treat these diseases are restricted to lifestyle change, pharmaceuticals, and eventually heart transplant if the condition is severe enough. While these treatment options are the standard for caring for patients who suffer from heart disease, limited regenerative ability of the heart restricts the effectiveness of treatment and may lead to other heart-related health problems in the future. Because of the increasing need for more effective therapeutic technologies for treating diseased heart tissue, cardiac patches are now a large focus for researchers. The cardiac patches are designed to be integrated into the patients' natural tissue to introduce mechanical support and healing to the damaged areas. As a promising alternative, synthetic biodegradable polymer based biomaterials can be easily manipulated to customize material properties, as well as possess certain desired characteristics for cardiac patch use. This comprehensive review summarizes recent works on synthetic biodegradable cardiac patches implanted into infarcted animal models. In addition, this review describes the basic requirements that should be met for cardiac patch development, and discusses the inspirations to designing new biomaterials and technologies for cardiac patches.

Plasma Treatment of Polymer Powder as an Effective Tool to Functionalize Polymers: Case Study Application on an Amphiphilic Polyurethane

Plasma treatment is a widely applied, easy, fast, and highly reproducible surface modification technique. In this work powder plasma treatment was exploited to expose carboxylic groups along the backbone of a water soluble polymer. Specifically, a custom-made amphiphilic poly(ether urethane) containing Poloxamer® 407 blocks (Mw = 54,000 Da) was first synthesized and its powders were plasma treated in the presence of Acrylic Acid vapor. To maximize -COOH group exposure while preventing polymer degradation, different Ar gas flow rates (i.e., 10, 30, and 50 sccm) were investigated. Upon gas flow increase, significant polymer degradation was observed, with a 35% molecular weight reduction at 50 sccm Ar flow rate. On the other hand, the highest number of exposed carboxylic groups (5.3 × 1018 ± 5.5 × 1017 units/gpolymer) was obtained by setting gas flow at 10 sccm. Hence, a gas flow of 10 sccm turned out to be the best set-up to maximize -COOH exposure while preventing degradation phenomena. Additionally, upon plasma treatment, no detrimental effects were observed in the thermoresponsiveness of polymer aqueous solutions, which was ensured by Poloxamer® 407 blocks. Therefore, the newly developed technology here applied on an amphiphilic poly(ether urethane) could pave the way to the tailored design of a plethora of different multifunctional hydrogels.

Polymers for Regenerative Medicine Structures Made via Multiphoton 3D Lithography

Multiphoton 3D lithography is becoming a tool of choice in a wide variety of fields. Regenerative medicine is one of them. Its true 3D structuring capabilities beyond diffraction can be exploited to produce structures with diverse functionality. Furthermore, these objects can be produced from unique materials allowing expanded performance. Here, we review current trends in this research area. We pay particular attention to the interplay between the technology and materials used. Thus, we extensively discuss undergoing light-matter interactions and peculiarities of setups needed to induce it. Then, we continue with the most popular resins, photoinitiators, and general material functionalization, with emphasis on their potential usage in regenerative medicine. Furthermore, we provide extensive discussion of current advances in the field as well as prospects showing how the correct choice of the polymer can play a vital role in the structure’s functionality. Overall, this review highlights the interplay between the structure’s architecture and material choice when trying to achieve the maximum result in the field of regenerative medicine.

Modular Strategies to Build Cell-Free and Cell-Laden Scaffolds towards Bioengineered Tissues and Organs

Engineering three-dimensional (3D) scaffolds for functional tissue and organ regeneration is a major challenge of the tissue engineering (TE) community. Great progress has been made in developing scaffolds to support cells in 3D, and to date, several implantable scaffolds are available for treating damaged and dysfunctional tissues, such as bone, osteochondral, cardiac and nerve. However, recapitulating the complex extracellular matrix (ECM) functions of native tissues is far from being achieved in synthetic scaffolds. Modular TE is an intriguing approach that aims to design and fabricate ECM-mimicking scaffolds by the bottom-up assembly of building blocks with specific composition, morphology and structural properties. This review provides an overview of the main strategies to build synthetic TE scaffolds through bioactive modules assembly and classifies them into two distinct schemes based on microparticles (µPs) or patterned layers. The µPs-based processes section starts describing novel techniques for creating polymeric µPs with desired composition, morphology, size and shape. Later, the discussion focuses on µPs-based scaffolds design principles and processes. In particular, starting from random µPs assembly, we will move to advanced µPs structuring processes, focusing our attention on technological and engineering aspects related to cell-free and cell-laden strategies. The second part of this review article illustrates layer-by-layer modular scaffolds fabrication based on discontinuous, where layers' fabrication and assembly are split, and continuous processes.

Interactions at scaffold interfaces: Effect of surface chemistry, structural attributes and bioaffinity

Effective regenerative medicine relies on understanding the interplay between biomaterial implants and the adjoining cells. Scaffolds contribute by presenting sites for cellular adhesion, growth, proliferation, migration, and differentiation which lead to regeneration of tissues over desired periods of time. The fabrication and recruitment of scaffolds often fail to consider the interactions that occur at the interfaces, thereby risking rejection. This lack of knowledge on interfacial microenvironments and related exchanges often causes reduced cellular interactions, poor cell survival and intervention failure. Successful regenerative therapy requires scaffolds with bespoke biocompatibility, optimum pore structure, and cues for cell attachments. These factors determine the development of cellular affinity in scaffolds. For biomedical applications, a detailed understanding of scaffolds and their interfaces is required for better tuning of biomaterials to suit the microenvironments. In this review, we discuss the role of biointerfaces with a focus on surface chemistry, pore structure, scaffold hydro-affinity and their biointeractions. An understanding of the effect of scaffold interfacial properties is crucial for enhancing the progress of tissue engineering towards clinical applications.

Unchain My Heart: Integrins at the Basis of iPSC Cardiomyocyte Differentiation

The cellular response to the extracellular matrix (ECM) microenvironment mediated by integrin adhesion is of fundamental importance, in both developmental and pathological processes. In particular, mechanotransduction is of growing importance in groundbreaking cellular models such as induced pluripotent stem cells (iPSC), since this process may strongly influence cell fate and, thus, augment the precision of differentiation into specific cell types, e.g., cardiomyocytes. The decryption of the cellular machinery starting from ECM sensing to iPSC differentiation calls for new in vitro methods. Conveniently, engineered biomaterials activating controlled integrin-mediated responses through chemical, physical, and geometrical designs are key to resolving this issue and could foster clinical translation of optimized iPSC-based technology. This review introduces the main integrin-dependent mechanisms and signalling pathways involved in mechanotransduction. Special consideration is given to the integrin-iPSC linkage signalling chain in the cardiovascular field, focusing on biomaterial-based in vitro models to evaluate the relevance of this process in iPSC differentiation into cardiomyocytes.

Impact of Biomaterials on Differentiation and Reprogramming Approaches for the Generation of Functional Cardiomyocytes

The irreversible loss of functional cardiomyocytes (CMs) after myocardial infarction (MI) represents one major barrier to heart regeneration and functional recovery. The combination of different cell sources and different biomaterials have been investigated to generate CMs by differentiation or reprogramming approaches although at low efficiency. This critical review article discusses the role of biomaterial platforms integrating biochemical instructive cues as a tool for the effective generation of functional CMs. The report firstly introduces MI and the main cardiac regenerative medicine strategies under investigation. Then, it describes the main stem cell populations and indirect and direct reprogramming approaches for cardiac regenerative medicine. A third section discusses the main techniques for the characterization of stem cell differentiation and fibroblast reprogramming into CMs. Another section describes the main biomaterials investigated for stem cell differentiation and fibroblast reprogramming into CMs. Finally, a critical analysis of the scientific literature is presented for an efficient generation of functional CMs. The authors underline the need for biomimetic, reproducible and scalable biomaterial platforms and their integration with external physical stimuli in controlled culture microenvironments for the generation of functional CMs.