Bioresorbable Polymeric Scaffold in Cardiovascular Applications

Optimization of polymer coating thickness and strut width in drug Eluting stents using Magnetic field

The transport of drug/magnetic particle (MP) conjugates in the presence of a Magnetic Field (MF) in Drug Eluting Stents (DESs) is modeled numerically using the Finite Volume Method (FVM). The effects of physiological conditions corresponding to different degrees of calcification, drug particles sizes and hematocrit level, were analyzed by investigating the roles of the tissue permeability, its anisotropy and the plasma viscosity. It was found that both in the absence and presence of the MF, as the tissue permeability decreases or the plasma viscosity increases, the free-phase drug and Extracellular Matrix (ECM)-bound phase contents increase. Stronger tissue anisotropy leads to a decrease of the free-phase drug content and an increase of the ECM-bound phase content. Within the explored ranges, the Specific Receptor (SR)-bound phase of the drug was found to be insensitive to the tissue permeability and plasma viscosity, and to be larger in anisotropic tissues. The activation of the MF leads systematically to larger free-phase drug contents, with the increases most prominent at smaller tissue permeability, anisotropy and plasma viscosity. On the other hand, the effects on the ECM-bound phase content are found to be stronger at larger permeability, smaller plasma viscosity and lower tissue anisotropy. For an isotropic tissue, the MF induces a decrease of the ECM-bound phase content at early times, followed by an increase at later times. For the considered ranges of permeability and viscosity, the MF does not seem to have any noticeable effects on the SR-bound phase. However, this phase of the drug tends to increase with the activation of the MF in isotropic tissues and is unchanged in anisotropic ones. These reported effects of the MF hold promise for alleviating two factors contributing to In-Stent Restenosis, namely the polymer coating width and thickness. The study reveals that a narrower or thinner polymer layer, in combination with the MF, can mimic the drug release dynamics of a wider or thicker polymer layer in the absence of the MF. The corresponding width and thickness of the magnetized stents, that we referred to as the equivalent polymer width (EPW) and equivalent polymer thickness (EPT) were determined and their dependence on the tissue permeability, isotropy and the plasma viscosity, was investigated. The study shows that it is possible to achieve the same drug delivery with polymer coating of half the width or half the thickness of the non-magnetized stent when an electric intensity of 3A is used.

Study onin vivoandin vitrodegradation of polydioxanone weaving tracheal stents

The appropriate degradation characteristics of polydioxanone (PDO) are necessary for the safety and effectiveness of stents. This study aimed to investigate the degradation of PDO weaving tracheal stents (PW stents)in vitroandin vivo. The degradation solution ofS. aureus(SAU),E. coli(ECO),P. aeruginosa(PAE), and control (N) were prepared, and the PW stents were immersed for 12 weeks. Then, the radial support force, weight retention, pH, molecular structure, thermal performance, and morphology were determined. Furthermore, the PW stents were implanted into the abdominal cavity of rabbits, and omentum was embedded. At feeding for 16 weeks, the mechanical properties, and morphology were measured. During the first 8 weeks, the radial support force in all groups was progressively decreased. At week 2, the decline rate of radial support force in the experimental groups was significantly faster compared to the N group, and the difference was narrowed thereafter. The infrared spectrum showed that during the whole degradation process, SAU, ECO and PAE solution did not lead to the formation of new functional groups in PW stents.In vitroscanning electron microscope observation showed that SAU and ECO were more likely to gather and multiply at the weaving points of the PW stents, forming colonies.In vivoexperiments showed that the degradation in the concavity of weaving points of PW stents was more rapid and severe. The radial support loss rate reached more than 70% at week 4, and the radial support force was no longer measurable after week 8. In omentum, multinuclear giant cells and foreign giant cells were found to infiltrate. PW stents have good biocompatibility. The degradation rate of PW stents in the aseptic conditionsin vivowas faster than in the bacteriological environmentin vitro.

Triggerable Patches for Medical Applications

Medical patches have garnered increasing attention in recent decades for several diagnostic and therapeutic applications. Advancements in material science, manufacturing technologies, and bioengineering have significantly widened their functionalities, rendering them highly versatile platforms for wearable and implantable applications. Of particular interest are triggerable patches designed for drug delivery and tissue regeneration purposes, whose action can be controlled by an external signal. Stimuli-responsive patches are particularly appealing as they may enable a high level of temporal and spatial control over the therapy, allowing high therapeutic precision and the possibility to adjust the treatment according to specific clinical and personal needs. This review aims to provide a comprehensive overview of the existing extensive literature on triggerable patches, emphasizing their potential for diverse applications and highlighting the strengths and weaknesses of different triggering stimuli. Additionally, the current open challenges related to the design and use of efficient triggerable patches, such as tuning their mechanical and adhesive properties, ensuring an acceptable trade-off between smartness and biocompatibility, endowing them with portability and autonomy, accurately controlling their responsiveness to the triggering stimulus and maximizing their therapeutic efficacy, are reviewed.

Scaffold-Mediated Drug Delivery for Enhanced Wound Healing: A Review

Wound healing is a complex physiological process involving coordinated cellular and molecular events aimed at restoring tissue integrity. Acute wounds typically progress through the sequential phases of hemostasis, inflammation, proliferation, and remodeling, while chronic wounds, such as venous leg ulcers and diabetic foot ulcers, often exhibit prolonged inflammation and impaired healing. Traditional wound dressings, while widely used, have limitations such poor moisture retention and biocompatibility. To address these challenges and improve patient outcomes, scaffold-mediated delivery systems have emerged as innovative approaches. They offer advantages in creating a conducive environment for wound healing by facilitating controlled and localized drug delivery. The manuscript explores scaffold-mediated delivery systems for wound healing applications, detailing the use of natural and synthetic polymers in scaffold fabrication. Additionally, various fabrication techniques are discussed for their potential in creating scaffolds with controlled drug release kinetics. Through a synthesis of experimental findings and current literature, this manuscript elucidates the promising potential of scaffold-mediated drug delivery in improving therapeutic outcomes and advancing wound care practices.

Two-Year Outcomes for Patients with Non-ST-Elevation Acute Coronary Syndrome Treated with Magmaris and Absorb Bioresorbable Scaffolds in Large-Vessel Lesions

BACKGROUND

The acute coronary syndrome (ACS) continues to be a fundamental indication for revascularization by percutaneous coronary intervention (PCI). Drug-eluting stent (DES) implantation remains a part of contemporary practice but permanent caging of the vascular structure with the metallic stent structure may increase the rate of device-related adverse clinical events. As an alternative to classic metallic DESs, the bioresorbable scaffolds (BRSs) have emerged as a temporary vascular support technology. We evaluated the mid-term outcomes of two generations of bioresorbable scaffolds-Absorb (Abbott-Vascular, Chicago, IL, USA) and Magmaris (Biotronik, Germany)-in patients with non-ST-elevation ACS.

METHODS

The study cohort consisted of 193 subjects after Magmaris implantation and 160 patients following Absorb implantation in large-vessel lesions.

RESULTS

At 2 years, a significantly lower rate of a primary outcome (cardiac death, myocardial infarction, stent thrombosis) was observed with Magmaris (5.2% vs. 15%; p = 0.002). In addition, we observed a significantly lower rate of MI in the target vessel (2.6% vs. 9.4%; p = 0.009) and a lower rate of scaffold thrombosis (0% vs. 3.7%; p = 0.008). The TLF rate between the two groups was not significantly different.

CONCLUSION

Magmaris demonstrated a good safety profile and more favorable clinical outcomes when compared to Absorb in patients with non-ST-elevation ACS.

Nitric Oxide Releasing Nanomaterials for Cardiovascular Applications

A central paradigm of cardiovascular homeostasis is that impaired nitric oxide (NO) bioavailability results in a wide array of cardiovascular dysfunction including incompetent endothelium-dependent vasodilatation, thrombosis, vascular inflammation, and proliferation of the intima. Over the course of more than a century, NO donating formulations such as organic nitrates and nitrites have remained a cornerstone of treatment for patients with cardiovascular diseases. These donors primarily produce NO in the circulation and are not targeted to specific (sub)cellular sites of action. However, safe, and therapeutic levels of NO require delivery of the right amount to a precise location at the right time. To achieve these aims, several recent strategies aimed at therapeutically generating or releasing NO in living systems have shown that polymeric and inorganic (silica, gold) nanoparticles and nanoscale metal-organic frameworks could either generate NO endogenously by the catalytic decomposition of endogenous NO substrates or can store and release therapeutically relevant amounts of NO gas. NO-releasing nanomaterials have been developed for vascular implants (such as stents and grafts) to target atherosclerosis, hypertension, myocardial ischemia-reperfusion injury, and cardiac tissue engineering. In this review, we discuss the advances in design and development of novel NO-releasing nanomaterials for cardiovascular therapeutics and critically examine the therapeutic potential of these nanoplatforms to modulate cellular metabolism, to regulate vascular tone, inhibit platelet aggregation, and limit proliferation of vascular smooth muscle with minimal toxic effects.

A synergistic strategy based on active hydroxymethyl amine compounds and fucoidan for bioprosthetic heart valves with enhancing anti-coagulation and anti-calcification properties

With an aging population, the patients with valvular heart disease (VHD) are growing worldwide, and valve replacement is a primary choice for these patients with severe valvular disease. Among them, bioprosthetic heart valves (BHVs), especially BHVs trough transcatheter aortic valve replacement, are widely accepted by patients on account of their good hemodynamics and biocompatibility. Commercial BHVs in clinic are prepared by glutaraldehyde cross-linked pericardial tissue with the risk of calcification and thrombotic complications. In the present study, a strategy combines improved hemocompatibility and anti-calcification properties for BHVs has been developed based on a novel non-glutaraldehyde BHV crosslinker hexakis(hydroxymethyl)melamine (HMM) and the anticoagulant fucoidan. Besides the similar mechanical properties and enhanced component stability compared to glutaraldehyde crosslinked PP (G-PP), the fucoidan modified HMM-crosslinked PPs (HMM-Fu-PPs) also exhibit significantly enhanced anticoagulation performance with a 72 % decrease in thrombus weight compared with G-PP in ex-vivo shunt assay, along with the superior biocompatibility, satisfactory anti-calcification properties confirmed by subcutaneous implantation. Owing to good comprehensive performance of these HMM-Fu-PPs, this simple and feasible strategy may offer a great potential for BHV fabrication in the future, and open a new avenue to explore more N-hydroxymethyl compound based crosslinker with excellent performance in the field of biomaterials.

Magnesium bioresorbable scaffold (Magmaris) versus polymer biodegradable ultrathin drug-eluting stent (Ultimaster) in acute coronary syndrome. Mid-term outcomes (2 years)

Introduction

Acute coronary syndrome (ACS) is a well-known risk factor for adverse clinical outcomes in percutaneous coronary intervention (PCI). Therefore, evaluation of coronary stents in this challenging clinical scenario can provide unique information on device safety and efficacy. Bioresorbable scaffolds (BRS) were designed to overcome long-term complications related to permanent vessel caging with a permanent metallic drug-eluting stent (DES).

Aim

We designed this study to evaluate the mid-term safety and efficiency of the Magmaris BRS in comparison to the leading new-generation ultrathin DES Ultimaster in the ACS population.

Material and methods

We present a retrospective analysis of 2-year follow-up data. The primary outcomes consisted of death from cardiac causes, myocardial infarction, and in-stent thrombosis. The second main study endpoint was defined as target-lesion failure (TLF).

Results

The study population consisted of two cohorts, the first of 193 patients treated with Magmaris implantation and the second of 169 patients treated with Ultimaster implantation. At the 2-year follow-up, there were no significant differences in both study cohorts in terms of primary outcome (5.1% vs. 11%; p = 0.051), and TLF (5.6% vs. 8%, p = 0.41).

Conclusions

Treatment with a second-generation BRS (Magmaris) versus a novel second-generation DES (Ultimaster) in non-ST-elevation acute coronary syndrome (NSTE-ACS) was associated with similar rates of target lesion failure at 2-year follow-up.

A review: analysis of technical challenges in cultured meat production and its commercialization

The cultured meat technology has developed rapidly in recent years, but there are still many technical challenges that hinder the large-scale production and commercialization of cultured meat. Firstly, it is necessary to lay the foundation for cultured meat production by obtaining seed cells and maintaining stable cell functions. Next, technologies such as bioreactors are used to expand the scale of cell culture, and three-dimensional culture technologies such as scaffold culture or 3D printing are used to construct the three-dimensional structure of cultured meat. At the same time, it can reduce production costs by developing serum-free medium suitable for cultured meat. Finally, the edible quality of cultured meat is improved by evaluating food safety and sensory flavor, and combining ethical and consumer acceptability issues. Therefore, this review fully demonstrates the current development status and existing technical challenges of the cultured meat production technology with regard to the key points described above, in order to provide research ideas for the industrial production of cultured meat.

Bisphosphonate-incorporated coatings for orthopedic implants functionalization

Bisphosphonates (BPs), the stable analogs of pyrophosphate, are well-known inhibitors of osteoclastogenesis to prevent osteoporotic bone loss and improve implant osseointegration in patients suffering from osteoporosis. Compared to systemic administration, BPs-incorporated coatings enable the direct delivery of BPs to the local area, which will precisely enhance osseointegration and bone repair without the systemic side effects. However, an elaborate and comprehensive review of BP coatings of implants is lacking. Herein, the cellular level (e.g., osteoclasts, osteocytes, osteoblasts, osteoclast precursors, and bone mesenchymal stem cells) and molecular biological regulatory mechanism of BPs in regulating bone homeostasis are overviewed systematically. Moreover, the currently available methods (e.g., chemical reaction, porous carriers, and organic material films) of BP coatings construction are outlined and summarized in detail. As one of the key directions, the latest advances of BP-coated implants to enhance bone repair and osseointegration in basic experiments and clinical trials are presented and critically evaluated. Finally, the challenges and prospects of BP coatings are also purposed, and it will open a new chapter in clinical translation for BP-coated implants.

Novel Molecular Vehicle-Based Approach for Cardiac Cell Transplantation Leads to Rapid Electromechanical Graft-Host Coupling

Myocardial remodeling is an inevitable risk factor for cardiac arrhythmias and can potentially be corrected with cell therapy. Although the generation of cardiac cells ex vivo is possible, specific approaches to cell replacement therapy remain unclear. On the one hand, adhesive myocyte cells must be viable and conjugated with the electromechanical syncytium of the recipient tissue, which is unattainable without an external scaffold substrate. On the other hand, the outer scaffold may hinder cell delivery, for example, making intramyocardial injection difficult. To resolve this contradiction, we developed molecular vehicles that combine a wrapped (rather than outer) polymer scaffold that is enveloped by the cell and provides excitability restoration (lost when cells were harvested) before engraftment. It also provides a coating with human fibronectin, which initiates the process of graft adhesion into the recipient tissue and can carry fluorescent markers for the external control of the non-invasive cell position. In this work, we used a type of scaffold that allowed us to use the advantages of a scaffold-free cell suspension for cell delivery. Fragmented nanofibers (0.85 µm ± 0.18 µm in diameter) with fluorescent labels were used, with solitary cells seeded on them. Cell implantation experiments were performed in vivo. The proposed molecular vehicles made it possible to establish rapid (30 min) electromechanical contact between excitable grafts and the recipient heart. Excitable grafts were visualized with optical mapping on a rat heart with Langendorff perfusion at a 0.72 ± 0.32 Hz heart rate. Thus, the pre-restored grafts' excitability (with the help of a wrapped polymer scaffold) allowed rapid electromechanical coupling with the recipient tissue. This information could provide a basis for the reduction of engraftment arrhythmias in the first days after cell therapy.

Calcification of Synthetic Vascular Grafts: A Systematic Review

Objective

Calcification of vascular grafts, including polyethylene terephthalate (PET) and expanded polytetrafluoroethylene (ePTFE) grafts may contribute to graft failure, but is under reported. The aim of this study was to review the literature to assess whether vascular graft calcification is deleterious to vascular graft outcomes.

Data sources

The Medline and Embase databases were searched.

Review methods

A systematic literature search according to PRISMA Guidelines was performed using a combined search strategy of MeSH terms. The MeSH terms used were "calcification, physiologic", "calcinosis", "vascular grafting", "blood vessel prosthesis", "polyethylene terephthalates", and "polytetrafluoroethylene".

Results

The systematic search identified 17 cases of PET graft calcification and 73 cases of ePTFE graft calcification over a 35 year period. All cases of PET graft calcification were reported in grafts explanted for graft failure. The majority of cases of ePTFE graft calcification were unexpectedly noted in grafts used during cardiovascular procedures and subsequently removed.

Conclusion

Calcification of synthetic vascular grafts is under reported but can compromise the long term performance of the grafts. More data, including specific analysis of radiological findings as well as explant analysis are needed to obtain a more sensitive and specific analysis of the prevalence and incidence of vascular graft calcification and the impact of calcification on synthetic graft outcomes.

Prosthetic vascular grafts engineered to combat calcification: Progress and future directions

Calcification in prosthetic vascular conduits is a major challenge in cardiac and vascular surgery that compromises the long-term performance of these devices. Significant research efforts have been made to understand the etiology of calcification in the cardiovascular system and to combat calcification in various cardiovascular devices. Novel biomaterial design and tissue engineering strategies have shown promise in preventing or delaying calcification in prosthetic vascular grafts. In this review, we highlight recent advancements in the development of acellular prosthetic vascular grafts with preclinical success in attenuating calcification through advanced biomaterial design. We also discuss the mechanisms of action involved in the designs that will contribute to the further understanding of cardiovascular calcification. Lastly, recent insights into the etiology of vascular calcification will guide the design of future prosthetic vascular grafts with greater potential for translational success.

Novel Self-expanding Shape-Memory Bioresorbable Peripheral Stent Displays Efficient Delivery, Accelerated Resorption, and Low Luminal Loss in a Porcine Model

OBJECTIVE AND DESIGN

The search for improved stenting technologies to treat peripheral artery disease is trending toward biodegradable self-expanding shape-memory stents that, as of now, still suffer from the acute trade-off between deliverability and luminal stability: Higher deliverability leads to lower lumen stability, vessel recoil, and stent breakage. This study was aimed at the development and testing of a self-expanding bioresorbable poly(l,l-lactide-co-ε-caprolactone) stent that was designed to produce confident self-expansion after efficient crimping, as well as quick bioresorption, and sufficient radial force.

MATERIALS AND METHODS

Bench tests were employed to measure shape-memory properties, radial force, and hydrolytic degradation of the stent. The porcine model was employed to study deliverability, lumen stability, biocompatibility, and stent integrity. A total of 32 stents were implanted in the iliac arteries of 16 pigs with 15 to 180 day follow-up periods. The stented vessels were studied by angiography and histological evaluation.

RESULTS

Recovery of the diameter of the stent due to shape-memory effect was equal to 90.6% after 6Fr crimping and storage in refrigeration for 1 week. Radial force measured after storage was equal to 0.7 N/mm. Technical success of implantation in pigs (after the delivery implemented by pusher) was 94%. At 180 days, no implanted stents were found to be fragmented: All of the devices remained at the site of implantation with no stent migration and all stents retained their luminal support. Only moderate inflammation and neoepithelialization were detected by histological assessment at 60, 90, 120, and 180 days. Lumen loss at 180 days was less than 25% of the vessel diameter.

CONCLUSIONS

The stent with the mechanical and chemical properties described in this study may present the optimal solution of the trade-off between deliverability and luminal stability that is necessary for designing the next generation stent for endovascular therapy of peripheral arterial disease.

Biodegradable polymer everolimus-eluting stents versus contemporary drug-eluting stents: a systematic review and meta‑analysis

In spite of similar efficacy and safety in pilot studies, compared with the contemporary durable polymer drug-eluting stent (DP-DES), the bioabsorbable polymer drug-eluting stent (BP-DES) may be more superior in promoting blood vessel healing. We sought to compare the safety and efficacy of everolimus-eluting BP-DES (BP-EES) with contemporary DP-DES through a meta-analysis. We performed this meta-analysis to provide further evidence of the safety and efficacy of BP-EES. Medline, Embase and the Cochrane library databases were searched for randomized controlled trials comparing clinical efficacy and safety of BP-EES versus contemporary DP-DES. Fifteen RCTs with a total of 15,572 patients were selected. The rate of MACE was 9.4% in patients receiving BP-EES and 7.3% receiving DP-EES (RR 1.13, 95% CI 0.99-1.29, p = 0.05; I² = 46%). TLF and MI were also similar in both groups. Based on the available data, this review demonstrates that BP-EES displays a clinically comparable efficacy and safety profile to that of contemporary DP-DES at years of follow-up in patients undergoing PCI.

Controlled and Synchronised Vascular Regeneration upon the Implantation of Iloprost- and Cationic Amphiphilic Drugs-Conjugated Tissue-Engineered Vascular Grafts into the Ovine Carotid Artery: A Proteomics-Empowered Study

Implementation of small-diameter tissue-engineered vascular grafts (TEVGs) into clinical practice is still delayed due to the frequent complications, including thrombosis, aneurysms, neointimal hyperplasia, calcification, atherosclerosis, and infection. Here, we conjugated a vasodilator/platelet inhibitor, iloprost, and an antimicrobial cationic amphiphilic drug, 1,5-bis-(4-tetradecyl-1,4-diazoniabicyclo [2.2.2]octan-1-yl) pentane tetrabromide, to the luminal surface of electrospun poly(ε-caprolactone) (PCL) TEVGs for preventing thrombosis and infection, additionally enveloped such TEVGs into the PCL sheath to preclude aneurysms, and implanted PCL^Ilo/CAD TEVGs into the ovine carotid artery (n = 12) for 6 months. The primary patency was 50% (6/12 animals). TEVGs were completely replaced with the vascular tissue, free from aneurysms, calcification, atherosclerosis and infection, completely endothelialised, and had clearly distinguishable medial and adventitial layers. Comparative proteomic profiling of TEVGs and contralateral carotid arteries found that TEVGs lacked contractile vascular smooth muscle cell markers, basement membrane components, and proteins mediating antioxidant defense, concurrently showing the protein signatures of upregulated protein synthesis, folding and assembly, enhanced energy metabolism, and macrophage-driven inflammation. Collectively, these results suggested a synchronised replacement of PCL with a newly formed vascular tissue but insufficient compliance of PCL^Ilo/CAD TEVGs, demanding their testing in the muscular artery position or stimulation of vascular smooth muscle cell specification after the implantation.

The bioresorbable magnesium scaffold (Magmaris)-State of the art: From basic concept to clinical application

Since its introduction to clinical practice, coronary artery stent implantation has become a crucial part of the therapy of coronary artery disease (CAD). Despite the undeniable evolution of percutaneous coronary revascularization procedures, drug-eluting stent (DES) technology shows some limitations. To overcome these limitations bioresorbable vascular scaffolds (BRS) were designed as a vessel-supporting technology allowing for anatomical and functional restoration of the vessel after the scaffold intended resorption. Various materials have been proposed as the basis of the scaffold backbone. In this narrative review, we present second-generation magnesium-alloy bioresorbable scaffold devices (Magmaris; Biotronik). Additionally, we discuss available preclinical and clinical data regarding this new magnesium BRS.

Dual-jet electrospun PDLGA/PCU nonwovens as promising mesh implant materials with controlled release of sirolimus and diclofenac

Dual-jet electrospinning was employed to produce two-component, partially degradable drug releasing nonwovens with interlacing of poly(D,L-lactide-co-glycolide) (PDLGA) and different poly(carbonate urethanes) (PCUs). Diclofenac sodium and sirolimus were released simultaneously from the copolyester carrier. The research focused on determining of release profiles of drugs, depending on the hydrophilicity of introduced PCU nanofibers. The influence of drugs incorporation on the hydrolytic degradation of the PDLGA and mechanical properties of nonwovens was also studied. Evaluation for interaction with cells in vitro was investigated on a fibroblast cell line in cytotoxicity and surface adhesion tests. Significant changes in drugs release rate, depending on the applied PCU were observed. It was also noticed, that hydrophilicity of drugs significantly influenced the hydrolytic degradation mechanism and surface erosion of the PDLGA, as well as the tensile strength of nonwovens. Tests carried out on cells in an in vitro experiment showed that introduction of sirolimus caused a slight reduction in the viability of fibroblasts as well as a strong limitation in their capability to colonize the surface of fibers. Due to improvement of mechanical strength and the ability to controlled drugs release, the obtained material may be considered as prospect surgical mesh implant in the treatment of hernia.

Electrospun Antibacterial Composites for Cartilage Tissue Engineering

Implantation of biomaterials capable of the controlled release of antibacterials during articular cartilage repair may prevent postoperative infections. Herein, biomaterials are prepared with biomimetic architectures (nonwoven mats of fibers) via electrospinning that are composed of poly(ɛ-caprolactone), poly(lactic acid), and Bombyx mori silk fibroin (with varying ratios) and, optionally, an antibiotic drug (cefixime trihydrate). The composition, morphology, and mechanical properties of the nanofibrous mats are characterized using scanning electron microscope, Fourier transform infrared spectroscopy, and tensile testing. The nonwoven mats have nanoscale fibers (typical diameters of 324-725 nm) and are capable of controlling the release profiles of the drug, with antibacterial activity against Gram +ve and Gram -ve bacteria (two common strains of human pathogenic bacteria, Staphylococcus aureus and Escherichia coli) under in vitro static conditions. The drug loaded nanofiber mats display cytocompatibility comparable to pure poly(ɛ-caprolactone) nanofibers when cultured with National Institutes of Health (NIH) NIH-3T3 fibroblast cell line and have long-term potential for clinical applications in the field of pharmaceutical sciences.

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.

A critical review of fibrous polyurethane-based vascular tissue engineering scaffolds

Certain polymeric materials such as polyurethanes (PUs) are the most prevalent class of used biomaterials in regenerative medicine and have been widely explored as vascular substitutes in several animal models. It is thought that PU-based biomaterials possess suitable hemo-compatibility with comparable performance related to the normal blood vessels. Despite these advantages, the possibility of thrombus formation and restenosis limits their application as artificial functional vessels. In this regard, various surface modification approaches have been developed to enhance both hemo-compatibility and prolong patency. While critically reviewing the recent advances in vascular tissue engineering, mainly PU grafts, this paper summarizes the application of preferred cell sources to vascular regeneration, physicochemical properties, and some possible degradation mechanisms of PU to provide a more extensive perspective for future research.

Influence of Fused Deposition Modelling Nozzle Temperature on the Rheology and Mechanical Properties of 3D Printed β-Tricalcium Phosphate (TCP)/Polylactic Acid (PLA) Composite

The primary goal of this study is to develop and analyze 3D printed structures based on a well-known composite known as β-Tricalcium Phosphate (TCP)- polylactic acid (PLA). There are some interesting aspects of this study. First, we developed 3D printable TCP-PLA composite filaments in-house, with high reproducibility, by a one-step process method using a single screw extruder. Second, we explored the physicochemical properties of the developed TCP-PLA composite filaments. Third, we investigated the effect of an FDM-based nozzle temperature of 190 °C, 200 °C, 210 °C, and 220 °C on the composite's crystallinity and rheological and mechanical properties. Results confirmed the successful development of constant-diameter TCP-PLA composite filaments with a homogeneous distribution of TCP particles in the PLA matrix. We observed that a higher nozzle temperature in the FDM process increased the crystallinity of the printed PLA and TCP-PLA structures. As a result, it also helped to enhance the mechanical properties of the printed structures. The rheological studies were performed in the same temperature range used in the actual FDM process, and results showed an improvement in rheological properties at higher nozzle temperatures. The bare polymer and the composite polymer-ceramic melts exhibited lower viscosity and less rigidity at higher nozzle temperatures, which resulted in enhancing the polymer melt flowability and interlayer bonding between the printed layers. Overall, our results confirmed that 3D printable TCP-PLA filaments could be made in-house, and optimization of the nozzle temperature is essential to developing 3D printed composite parts with favorable mechanical properties.

Surface engineering and the application of laser-based processes to stents - A review of the latest development

Late in-stent thrombus and restenosis still represent two major challenges in stents’ design. Surface treatment of stent is attracting attention due to the increasing importance of stenting intervention for coronary artery diseases. Several surface engineering techniques have been utilised to improve the biological response in vivo on a wide range of biomedical devices. As a tailorable, precise, and ultra-fast process, laser surface engineering offers the potential to treat stent materials and fabricate various 3D textures, including grooves, pillars, nanowires, porous and freeform structures, while also modifying surface chemistry through nitridation, oxidation and coatings. Laser-based processes can reduce the biodegradable materials' degradation rate, offering many advantages to improve stents’ performance, such as increased endothelialisation rate, prohibition of SMC proliferation, reduced platelet adhesion and controlled corrosion and degradation. Nowadays, adequate research has been conducted on laser surface texturing and surface chemistry modification. Laser texturing on commercial stents has been also investigated and a promotion of performance of laser-textured stents has been proved.

In this critical review, the influence of surface texture and surface chemistry on stents performance is firstly reviewed to understand the surface characteristics of stents required to facilitate cellular response. This is followed by the explicit illustration of laser surface engineering of stents and/or related materials. Laser induced periodic surface structure (LIPSS) on stent materials is then explored, and finally the application of laser surface modification techniques on latest generation of stent devices is highlighted to provide future trends and research direction on laser surface engineering of stents.

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Compared conventional surface engineering with laser-based methods for biomedical devices.

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Explained the influence of texture geometry and surface chemistry on stents biological response.

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Reviewed state of the art in laser surface engineering of stents for improved biological response.

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Reviewed state of the art in laser surface engineering to control degradation of bioresorbable stents.

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Highlighted novel laser surface engineering designs for improved stents'performance.

Nanoparticles-reinforced poly-l-lactic acid composite materials as bioresorbable scaffold candidates for coronary stents: Insights from mechanical and finite element analysis

Current generation of bioresorbable coronary scaffolds (BRS) posed thrombogenicity and deployment issues owing to its thick struts and overall profile. To this end, we hypothesize that the use of nanocomposite materials is able to provide improved material properties and sufficient radial strength for the intended application even at reduced strut thickness. The nanocomposite formulations of tantalum dioxide (Ta₂O₅), L-lactide functionalized (LA)-Ta₂O₅, hydroxyapatite (HA) and LA-HA with poly-l-lactic acid (PLLA) were evaluated in this study. Results showed that tensile modulus and strength were enhanced with non-functionalized nanofillers up until 15 wt% loading, whereas ductility was compromised. On the other hand, functionalized nanofillers/PLLA exhibited improved nanofiller dispersion which resulted higher tensile modulus, strength, and ductility. Selected nanocomposite formulations were evaluated using finite element analysis (FEA) of a stent with varying strut thickness (80, 100 and 150 μm). FEA data has shown that nanocomposite BRS with thinner struts (80-100 μm) made with 15 wt% LA-Ta₂O₅/PLLA and 10 wt% LA-HA/PLLA have increased radial strength, stiffness and reduced recoil compared to PLLA BRS at 150 μm. The reduced strut thickness can potentially mitigate issues such as scaffold thrombosis and promote re-endothelialisation of the vessel.

Biomechanics of Additively Manufactured Metallic Scaffolds-A Review

This review paper is related to the biomechanics of additively manufactured (AM) metallic scaffolds, in particular titanium alloy Ti6Al4V scaffolds. This is because Ti6Al4V has been identified as an ideal candidate for AM metallic scaffolds. The factors that affect the scaffold technology are the design, the material used to build the scaffold, and the fabrication process. This review paper includes thus a discussion on the design of Ti6A4V scaffolds in relation to how their behavior is affected by their cell shapes and porosities. This is followed by a discussion on the post treatment and mechanical characterization including in-vitro and in-vivo biomechanical studies. A review and discussion are also presented on the ongoing efforts to develop predictive tools to derive the relationships between structure, processing, properties and performance of powder-bed additive manufacturing of metals. This is a challenge when developing process computational models because the problem involves multi-physics and is of multi-scale in nature. Advantages, limitations, and future trends in AM scaffolds are finally discussed. AM is considered at the forefront of Industry 4.0, the fourth industrial revolution. The market of scaffold technology will continue to boom because of the high demand for human tissue repair.

Poly(L-Lactic Acid) Composite with Surface-Modified Magnesium Hydroxide Nanoparticles by Biodegradable Oligomer for Augmented Mechanical and Biological Properties

Poly(L-lactic acid) (PLLA) has attracted a great deal of attention for its use in biomedical materials such as biodegradable vascular scaffolds due to its high biocompatibility. However, its inherent brittleness and inflammatory responses by acidic by-products of PLLA limit its application in biomedical materials. Magnesium hydroxide (MH) has drawn attention as a potential additive since it has a neutralizing effect. Despite the advantages of MH, the MH can be easily agglomerated, resulting in poor dispersion in the polymer matrix. To overcome this problem, oligo-L-lactide-ε-caprolactone (OLCL) as a flexible character was grafted onto the surface of MH nanoparticles due to its acid-neutralizing effect and was added to the PLLA to obtain PLLA/MH composites. The pH neutralization effect of MH was maintained after surface modification. In an in vitro cell experiment, the PLLA/MH composites including OLCL-grafted MH exhibited lower platelet adhesion, cytotoxicity, and inflammatory responses better than those of the control group. Taken together, these results prove that PLLA/MH composites including OLCL-grafted MH show excellent augmented mechanical and biological properties. This technology can be applied to biomedical materials for vascular devices such as biodegradable vascular scaffolds.

PLCL vascular external sheath carrying prednisone for improving patency rate of the vein graft

Coronary artery bypass graft surgery (CABG) is an impactful treatment for coronary heart disease. Intimal hyperplasia is the central reason for the restenosis of vein grafts after CABG. The introduction of external vascular sheaths around VGs (VGs) can effectively inhibit intimal hyperplasia and ensure the patency of VGs. In this study, the well-known biodegradable copolymer poly (ε-caprolactone-co-L, L-lactide) (PLCL) was electrospun into high porosity external sheaths. The prednisone loaded in the PLCL sheath was slowly released during the degradation process of PLCL. Under the combined effects of sheath and prednisone, intimal hyperplasia was inhibited. For the cell experiments, all sheaths show low cytotoxicity to L929 cells at different concentrations at different time intervals. The ultrasonography and histological results showed prominent dilation and intimal hyperplasia of VG without sheath after two months of surgery. But there was no dilation in PLCL and PLCL_Prednisone groups. Notably, the prednisone-loaded sheath group exhibited efficacy in inhibiting intimal hyperplasia and ensured graft patency.

Cellular response of blood-borne immune cells to PEEU fiber meshes

BACKGROUND

Polymeric materials have been widely used as artificial grafts in cardiovascular applications. These polymeric implants can elicit a detrimental innate and adaptive immune response after interacting with peripheral blood. A surface modification with components from extracellular matrices (ECM) may minimize the activation of immune cells from peripheral blood. The aim of this study is to compare the cellular response of blood-born immune cells to the fiber meshes from polyesteretherurethane (PEEUm) and PEEUm with ECM coating (PEEUm + E).

MATERIALS AND METHODS

Electrospun PEEUm were used as-is or coated with human cardiac ECM. Different immune cells were isolated form human peripheral blood. Cytokine release profile from naïve and activated monocytes was assessed. Macrophage polarization and T cell proliferation, as indication of immune response were evaluated.

RESULTS

There was no increase in cytokine release (IL-6, TNF-α, and IL-10) from activated monocytes, macrophages and mononuclear cells on PEEUm; neither upon culturing on PEEUm + E. Naïve monocytes showed increased levels of IL-6 and TNF-α, which were not present on PEEUm + E. There was no difference on monocyte derived macrophage polarization towards pro-inflammatory M1 or anti-inflammatory M2 on PEEUm and PEEUm + E. Moreover, T cell proliferation was not increased upon interacting with PEEUm directly.

CONCLUSION

As PEEUm only elicits a minimal response from naïve monocytes but not from monocytes, peripheral blood mononuclear cells (PBMCs) or T cells, the slight improvement in response to PEEUm + E might not justify the additional effort of coating with a human ECM.

Tissue-Engineered Carotid Artery Interposition Grafts Demonstrate High Primary Patency and Promote Vascular Tissue Regeneration in the Ovine Model

Tissue-engineered vascular graft for the reconstruction of small arteries is still an unmet clinical need, despite the fact that a number of promising prototypes have entered preclinical development. Here we test Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)Poly(ε-caprolactone) 4-mm-diameter vascular grafts equipped with vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and stromal cell-derived factor 1α (SDF-1α) and surface coated with heparin and iloprost (PHBV/PCL[VEGF-bFGF-SDF]^Hep/Ilo, n = 8) in a sheep carotid artery interposition model, using biostable vascular prostheses of expanded poly(tetrafluoroethylene) (ePTFE, n = 5) as a control. Primary patency of PHBV/PCL[VEGF-bFGF-SDF]^Hep/Ilo grafts was 62.5% (5/8) at 24 h postimplantation and 50% (4/8) at 18 months postimplantation, while all (5/5) ePTFE conduits were occluded within the 24 h after the surgery. At 18 months postimplantation, PHBV/PCL[VEGF-bFGF-SDF]^Hep/Ilo grafts were completely resorbed and replaced by the vascular tissue. Regenerated arteries displayed a hierarchical three-layer structure similar to the native blood vessels, being fully endothelialised, highly vascularised and populated by vascular smooth muscle cells and macrophages. The most (4/5, 80%) of the regenerated arteries were free of calcifications but suffered from the aneurysmatic dilation. Therefore, biodegradable PHBV/PCL[VEGF-bFGF-SDF]^Hep/Ilo grafts showed better short- and long-term results than bio-stable ePTFE analogues, although these scaffolds must be reinforced for the efficient prevention of aneurysms.

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.

Scaffolds for the manufacture of cultured meat

The cultured meat market has been growing at an accelerated space since the first creation of cultured meat burger back in 2013. Substantial efforts have been made to reduce costs by eliminating serum in growth media and improving process efficiency by employing bioreactors. In parallel, efforts are also being made on scaffolding innovations to offer better cells proliferation, differentiation and tissue development. So far, scaffolds used in cultured meat research are predominantly collagen and gelatin, which are animal-derived. To align with cell-based meat vision i.e. environment conservation and animal welfare, plant-derived biomaterials for scaffolding are being intensively explored. This paper reviews and discusses the advantages and disadvantages of scaffold materials and potential scaffolding related to scale-up solution for the production of cultured meat.

Effect of Homochirality of Dipeptide to Polymers’ Degradation

As natural polymer materials, proteins are readily biodegradable, interestingly, the synthetic polyamides (PAs) that are based on the same amide bonds (also called peptide bonds in proteins) are barely degradable. Whether did the chirality and configuration of the amino acids play an important role. By using different configuration of amino acids, 4 types of polyamide-imides (PAIs) containing dipeptides of LL, DL, LD, and DD configurations, respectively, were synthesized. It was found that the PAIs based on natural LL configuration of dipeptide structure are much more readily biodegradable than those based on non-natural LD, DL, and DD configuration of dipeptides. It was confirmed that the natural L-configuration of amino acids play a critical role in degradability of proteins. And it also suggested that different type and amount of peptide fragments can be introduced in polymer to create series of polymer materials that can be biodegraded at controllable speed.