A hybrid electrospun PU/PCL scaffold satisfied the requirements of blood vessel prosthesis in terms of mechanical properties, pore size, and biocompatibility

The influence of physical and spatial substrate characteristics on endothelial cells

Cardiovascular diseases are a main cause of death worldwide, leading to a growing demand for medical devices to treat this patient group. Central to the engineering of such devices is a good understanding of the biology and physics of cell-surface interactions. In existing blood-contacting devices, such as vascular grafts, the interaction between blood, cells, and material is one of the main limiting factors for their long-term durability. An improved understanding of the material's chemical- and physical properties as well as its structure all play a role in how endothelial cells interact with the material surface. This review provides an overview of how different surface structures influence endothelial cell responses and what is currently known about the underlying mechanisms that guide this behavior. The structures reviewed include decellularized matrices, electrospun fibers, pillars, pits, and grated surfaces.

Fabrication of an Artificial Pulley Based on Electrospun Composite Polyurethane/Polycaprolactone Nanofibers for Hand Surgery: Structural, Mechanical, In Vitro, and In Vivo Examinations

Injuries to the hand's flexor pulley system can be debilitating, causing pain and restricting movement of the affected finger(s). The creation of a biocompatible artificial pulley could potentially alleviate some of the complications associated with current surgical treatments. In this study, a biocompatible artificial pulley was fabricated by using polycaprolactone (PCL) and polyurethane (PU) in the form of an electrospun nanofiber structure. All scaffolds were structurally analyzed using FESEM imaging, porosity, FTIR, and DSC examinations. Mechanical properties were evaluated, and in vitro studies were conducted on the degradation rate, swelling ratio, and toxicity. Immune response to fabricated scaffolds was evaluated by implanting them under the skin of rats for further pathological examination. All scaffolds exhibited a nanoscale structure and high porosity without any undesirable functional groups. The 25% PCL scaffold showed 17%, 20%, 80%, 17%, and 70% significant increases in Fmax, final stress, final strain, Young's modulus, and elongation percentage, respectively. In fact, the PCL25% scaffold demonstrated more than 100% improvement in mechanical properties compared to those of A2 and A4 natural pulleys. Additionally, all scaffold structures showed cell viability similar to that of the control sample. The study suggests that scaffolds made of 25% PCL hold promise as effective artificial pulleys for reconstructing the flexor tendon pulley system in cases of injury.

Anticancer potential of Carica papaya Linn black seed extract against human colon cancer cell line: in vitro study

BACKGROUND

Since cancer is one of the most prevalent diseases in the world, further studies are needed to identify the effective therapeutic modalities. The second deadliest and third most common cancer is colorectal cancer (CRC). Papaya (Carica papaya Linn) seeds offer anti-cancer properties that can cure various types of cancer, such as liver and prostate cancer.

METHODS

The study aimed to evaluate the anti-cancer activity of Carica papaya seed extract on colorectal cancer cell lines (Caco-2) and used techniques to assess the anti-cancer potential. The effectiveness of SE on cell proliferation and the viability of HTB-37 Caco-2 and C-166 cells were assessed using the MTT test. Real-time RT-PCR was used to measure gene expression levels and evaluate the activity of genes involved in apoptosis, including caspase-3, p53, Cycs, and Bcl-2. Finally, flow cytometry was used to analyze apoptosis induction by detecting changes in cell morphology and DNA content.

RESULTS

The study showed that the MTT reduction assay was dependent on cancer cell type and concentration of SE compared to the control cells and C-166, with a mean IC₅₀ value of 9.734 ug/ml. The cytotoxicity was accompanied by some morphological alterations in the colorectal cancer cell line (Caco-2). The expression of the genes for p53, Cycs, and caspase-3 was substantially up-regulated, while Bcl-2 was dramatically down-regulated compared to control cells. The cell cycle arrested at the G2-M phase and the presence of early and late apoptotic characteristics post-treatment increased the apoptotic profile.

CONCLUSION

It concluded that papaya seeds aqueous extract could act as a novel therapeutic option for colorectal cancer (CRC).

Poloxamer-Based Scaffolds for Tissue Engineering Applications: A Review

Poloxamer is a triblock copolymer with amphiphilicity and reversible thermal responsiveness and has wide application prospects in biomedical applications owing to its multifunctional properties. Poloxamer hydrogels play a crucial role in the field of tissue engineering and have been regarded as injectable scaffolds for loading cells or growth factors (GFs) in the last few years. Hydrogel micelles can maintain the integrity and stability of cells and GFs and form an appropriate vascular network at the application site, thus creating an appropriate microenvironment for cell growth, nerve growth, or bone integration. The injectability and low toxicity of poloxamer hydrogels make them a noninvasive method. In addition, they can also be good candidates for bio-inks, the raw material for three-dimensional (3D) printing. However, the potential of poloxamer hydrogels has not been fully explored owing to the complex biological challenges. In this review, the latest progress and cutting-edge research of poloxamer-based scaffolds in different fields of application such as the bone, vascular, cartilage, skin, nervous system, and organs in tissue engineering and 3D printing are reviewed, and the important roles of poloxamers in tissue engineering scaffolds are discussed in depth.

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.

Statistical modelling and optimization of print quality and mechanical properties of customized tubular scaffolds fabricated using solvent-based extrusion 3D printing process

Tissue-engineered tubular scaffolds offer huge potential to heal or replace the diseased organ parts like blood vessels, trachea, oesophagus and ureter. However, manufacturing these scaffolds in various scales and shapes is always challenging and requires progressive technology. Developing a flexible and accurate manufacturing method is a major developmental direction in the field of tubular scaffold fabrication. In this context, the present work presents a novel solvent-based extrusion 3D printing which allows extruding over a rotating mandrel to fabricate tubular scaffolds of polycaprolactone (PCL) and polyurethane (PU). Experimental runs were planned as per the central composite design (CCD) to evaluate the effects of input parameters like infill density, layer thickness, print speed and percentage of PU on the output responses like printing quality and mechanical characteristics. The printing quality was quantified by measuring average surface roughness of the printed scaffolds and mechanical properties were evaluated by measuring radial compressive load, and percentage of elongation. The experimental investigations revealed that printing quality was improved at higher infill densities and was deteriorated at higher print speeds and layer thicknesses. Similarly, the radial compressive load was improved with the increase in infill density and was decreased with an increase in layer thickness, print speed and percentage of PU. The percentage of elongation was found to improve at higher infill densities and percentages of PU and was reduced with an increase in layer thickness and print speed. Additionally, a multi-objective optimization using Genetic Algorithm was used to evaluate the optimum conditions to minimize surface roughness and maximizing radial compression load and percentage of elongation. Finally, a case study was performed by comparing the mechanical properties of tubular organs and scaffolds from the existing reports and results of the present work.

Biofabrication of tissue engineering vascular systems

Cardiovascular disease (CVD) is the leading cause of death among persons aged 65 and older in the United States and many other developed countries. Tissue engineered vascular systems (TEVS) can serve as grafts for CVD treatment and be used as in vitro model systems to examine the role of various genetic factors during the CVD progressions. Current focus in the field is to fabricate TEVS that more closely resembles the mechanical properties and extracellular matrix environment of native vessels, which depends heavily on the advance in biofabrication techniques and discovery of novel biomaterials. In this review, we outline the mechanical and biological design requirements of TEVS and explore the history and recent advances in biofabrication methods and biomaterials for tissue engineered blood vessels and microvascular systems with special focus on in vitro applications. In vitro applications of TEVS for disease modeling are discussed.

Melt Electrospinning of Polymers: Blends, Nanocomposites, Additives and Applications

Melt electrospinning has been developed in the last decade as an eco-friendly and solvent-free process to fill the gap between the advantages of solution electrospinning and the need of a cost-effective technique for industrial applications. Although the benefits of using melt electrospinning compared to solution electrospinning are impressive, there are still challenges that should be solved. These mainly concern to the improvement of polymer melt processability with reduction of polymer degradation and enhancement of fiber stability; and the achievement of a good control over the fiber size and especially for the production of large scale ultrafine fibers. This review is focused in the last research works discussing the different melt processing techniques, the most significant melt processing parameters, the incorporation of different additives (e.g., viscosity and conductivity modifiers), the development of polymer blends and nanocomposites, the new potential applications and the use of drug-loaded melt electrospun scaffolds for biomedical applications.

Future Perspectives in Small-Diameter Vascular Graft Engineering

The increased demands of small-diameter vascular grafts (SDVGs) globally has forced the scientific society to explore alternative strategies utilizing the tissue engineering approaches. Cardiovascular disease (CVD) comprises one of the most lethal groups of non-communicable disorders worldwide. It has been estimated that in Europe, the healthcare cost for the administration of CVD is more than 169 billion €. Common manifestations involve the narrowing or occlusion of blood vessels. The replacement of damaged vessels with autologous grafts represents one of the applied therapeutic approaches in CVD. However, significant drawbacks are accompanying the above procedure; therefore, the exploration of alternative vessel sources must be performed. Engineered SDVGs can be produced through the utilization of non-degradable/degradable and naturally derived materials. Decellularized vessels represent also an alternative valuable source for the development of SDVGs. In this review, a great number of SDVG engineering approaches will be highlighted. Importantly, the state-of-the-art methodologies, which are currently employed, will be comprehensively presented. A discussion summarizing the key marks and the future perspectives of SDVG engineering will be included in this review. Taking into consideration the increased number of patients with CVD, SDVG engineering may assist significantly in cardiovascular reconstructive surgery and, therefore, the overall improvement of patients' life.

Preparation of PU/Fibrin Vascular Scaffold with Good Biomechanical Properties and Evaluation of Its Performance in vitro and in vivo

PURPOSE

The development of tissue-engineered blood vessels provides a new source of donors for coronary artery bypass grafting and peripheral blood vessel transplantation. Fibrin fiber has good biocompatibility and is an ideal tissue engineering vascular scaffold, but its mechanical property needs improvement.

METHODS

We mixed polyurethane (PU) and fibrin to prepare the PU/fibrin vascular scaffolds by using electrospinning technology in order to enhance the mechanical properties of fibrin scaffold. We investigated the morphological, mechanical strength, hydrophilicity, degradation, blood and cell compatibility of PU/fibrin (0:100), PU/fibrin (5:95), PU/fibrin (15:85) and PU/fibrin (25:75) vascular scaffolds. Based on the results in vitro, PU/fibrin (15:85) was selected for transplantation in vivo to repair vascular defects, and the extracellular matrix formation, vascular remodeling, and immune response were evaluated.

RESULTS

The results indicated that the fiber diameter of the PU/fibrin (15:85) scaffold was about 712nm. With the increase of PU content, the mechanical strength of the composite scaffolds increased, however, the degradation rate decreased gradually. The PU/fibrin scaffold showed good hydrophilicity and hemocompatibility. PU/fibrin (15:85) vascular scaffold could promote the adhesion and proliferation of mesenchymal stromal cells (MSCs). Quantitative RT-PCR experimental results showed that the expression of collagen, survivin and vimentin genes in PU/fibrin (15:85) was higher than that in PU/fibrin (25:75). The results in vivo indicated the mechanical properties and compliance of PU/fibrin grafts could meet clinical requirements and the proportion of thrombosis or occlusion was significantly lower. The graft showed strong vasomotor response, and the smooth muscle cells, endothelial cells, and ECM deposition of the neoartery were comparable to that of native artery after 3 months. At 3 months, the amount of macrophages in PU/fibrin grafts was significantly lower, and the secretion of pro-inflammatory and anti-inflammatory cytokines decreased.

CONCLUSION

PU/fibrin (15:85) vascular scaffolds had great potential to be used as small-diameter tissue engineering blood vessels.

Effect of elasticity on electrospun styrene-butadiene-styrene fibrous membrane cell culture behaviors

In this study, elastic styrene-butadiene-styrene (SBS), non-elastic SBS and their blends at different ratios were electrospun into fibrous membranes and their cell biocompatibility was evaluated. The as-spun fibers showed an average fiber diameter of 2 µm, and the fibrous membranes had pore size of 8 ± 0.01 µm. The blending ratios of the elastic with non-elastic SBSs showed little effect on fibrous structure, but affected the mechanical properties. All SBS membrane showed no cytotoxicity on endothelial cells (ECs). ECs attached and proliferated on all the SBS fibrous membrane scaffolds regardless of their elasticity. ECs maintained their polygonal shape on the scaffolds and they tended to orient along the fiber length. The SBS fibrous samples with elastic:non-elastic SBS weight ratios of 1:1 and 2:3 showed better cell viability than that of elastic and non-elastic SBS.

Conjugated Linoleic Acid Grafting Improved Hemocompatibility of the Polycaprolactone Electrospun Membrane

Polycaprolactone (PCL) is a versatile biomaterial with a wide range of medical applications, but its use in blood-contacting devices is hampered due to insufficient hemocompatibility. In this work, electrospun polycaprolactone (PCL) membranes were chemically grafted with conjugated linoleic acid (CLA) to prevent induced blood coagulation. The density of grafted CLA and its effects on the morphology and wettability of the membranes were examined. The study also investigated how the membrane interacted with human whole blood and platelets to determine its antithrombotic properties. As the results suggested, the grafting caused a negligible effect on the physical properties of the membrane but greatly improved its compatibility with blood, showing that the approach can be investigated further for blood-contacting applications.

Polyurethane/polycaprolactone membrane grafted with conjugated linoleic acid for artificial vascular graft application

Constructing satisfied small-diameter vascular graft (diameter less than 6 mm) remains an unsolvable challenge in vascular tissue engineering. This study described the fabrication of electrospun polyurethane/polycaprolactone (PU/PCL) membranes chemically grafted with various densities of conjugated linoleic acid (CLA) - an antithrombotic fatty acid - for making small-diameter blood vessel. Differences in mechanical, antithrombotic properties and biocompatibility of the membranes resulting from the CLA-grafting procedure were the focus of the study. Investigation of mechanical properties relevant to vascular graft application revealed that these properties of the membranes remained unaffected and satisfied clinical criteria following the CLA graft. Blood-membrane interaction assays showed that the CLA-grafted membranes mitigated the adhesion of blood cells, as well as preventing blood coagulation. These effects were also commensurate with increasing density of CLA, suggesting an effective approach to improve antithromboticity. Cellular tests suggested that CLA has an optimal density at which it promoted cell proliferation on the surface of the membranes; however, excessive presence of CLA might cause undesirable inhibition on cells. In conclusion, PU/PCL membrane grafted with CLA could be a prospective material for vascular tissue engineering with further development and investigation.

Nanocomposite foams based on flexible biobased thermoplastic polyurethane and ZnO nanoparticles as potential wound dressing materials

In the present study biobased and soft thermoplastic polyurethane (TPU), obtained by polymerization from fatty acids, was used to produce TPU/ZnO nanocomposite foams by thermally induced phase separation method (TIPS). The produced foams were characterized and evaluated regarding their potential uses as wound dressing materials. The structure and morphology of the prepared flexible polymer foams with different content of ZnO nanofiller (1, 2, 5 and 10 wt% related to the polymer) were studied by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Highly porous nanocomposite structure made of interconnected pores with dimensions between 10 and 60 μm was created allowing water vapor transmission rate (WVTR) up to 8.9 mg/cm²·h. The TPU/ZnO foams, tested for their ability to support cells and their growth, showed highest cell proliferation for TPU nanocomposite foams with 2 and 5 wt% ZnO. Overall, the nanocomposite foams displayed a low cytotoxic potential (varied proportionally to the ZnO content) and good biocompatibility. All tested nanocomposite foams were found to be significantly active against biofilms formed by different Gram-positive (Enterococcus faecalis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. Based on their behaviors, flexible TPU/ZnO nanocomposite foams can be considered for biomedical applications such as potential active wound dressing.

Electrospun Fibrous Scaffolds for Small-Diameter Blood Vessels: A Review

Small-diameter blood vessels (SDBVs) are still a challenging task to prepare due to the occurrence of thrombosis formation, intimal hyperplasia, and aneurysmal dilation. Electrospinning technique, as a promising tissue engineering approach, can fabricate polymer fibrous scaffolds that satisfy requirements on the construction of extracellular matrix (ECM) of native blood vessel and promote the adhesion, proliferation, and growth of cells. In this review, we summarize the polymers that are deployed for the fabrication of SDBVs and classify them into three categories, synthetic polymers, natural polymers, and hybrid polymers. Furthermore, the biomechanical properties and the biological activities of the electrospun SBVs including anti-thrombogenic ability and cell response are discussed. Polymer blends seem to be a strategic way to fabricate SDBVs because it combines both suitable biomechanical properties coming from synthetic polymers and favorable sites to cell attachment coming from natural polymers.

A novel layer-structured scaffold with large pore sizes suitable for 3D cell culture prepared by near-field electrospinning

Electrospinning is a powerful method for preparing porous materials that can be applied as biomedical materials for implantation or tissue engineering or as scaffolds for 3D cell culture experiments. However, this technique is limited in practical applications because the pore size of 3D scaffolds directly prepared by conventional electrospinning is usually less than several tens of micrometres, which may not be suitable for 3D cell culture and tissue growth. To allow for satisfactory 3D cell culture and tissue engineering, the pore size of the scaffold should be controllable according to the requirement of the specific cells to be cultured. Here, we show that layer-structured scaffolds with pore sizes larger than 100μm can be obtained by stacking meshes prepared by direct-writing using the near-field electrospinning (NFES) technique. In the study, we prepared composite scaffolds made of polycaprolactone (PCL) and hydroxyapatite (HAp) via the above-mentioned method and tested the effectiveness of the novel scaffold in cell culture using mouse pre-osteoblast cells (MC3T3-E1). The pore size and the degradability of the PCL/HAp scaffolds were characterized. The results showed that the average pore size of the scaffolds was 167μm, which was controllable based on the required application; the degradation rate was controllable depending on the ratio of PCL to HAp. The biocompatibility of the scaffolds in vitro was studied, and it was found that the scaffolds showed no toxicity and that the cells could effectively attach, proliferate, and differentiate in the 3D skeleton of the scaffolds. Our studies showed that a simple modification of the preparation procedure can lead to a new way to fabricate novel layer-structured 3D scaffolds with controllable structures and pore sizes suitable for practical applications in implantation, tissue engineering and 3D cell culture.

Fabrication and Characterization of Electrospun Bi-Hybrid PU/PET Scaffolds for Small-Diameter Vascular Grafts Applications

In spite of advances have been made during the past decades, the problems associated with small-diameter vascular grafts, including low patency and compliance mismatch and in consequence of that thrombosis, aneurysm and intimal hyperplasia are still challenges. To address these problems, net polyurethane (PU) and poly (ethylene terephthalate) (PET) polymers and hybrid PU/PET were electrospun to create three different types of small-diameter vascular scaffolds due to their unique physicochemical characteristics: PU, PET, and novel hybrid PU/PET scaffolds. The results show that the PU and PET composite can improve the mechanical properties of the tissue-engineered vascular scaffolds in the range of the native vessels where the non-cytotoxicity characteristic of these well-known polymers is still immutable. The compliance and stiffness factor of the fabricated hybrid scaffolds were 4.468 ± 0.177 and 22.718 ± 0.896%/0.01 mmHg, respectively, which were significantly different with that of the net PU and PET electrospun scaffolds. Other properties such as ultimate tensile stress (UTS) (3.56 ± 1.21 MPa) were also in good accordance with the native vessels. Furthermore, FT-IR analysis testified the presence of both PU and PET in the hybrid scaffolds. Overall, we were able to fabricate a hybrid scaffold as a small-diameter vascular graft that mechanically matched the gold standard of blood vessel substitution.

Preparation and characterization of polycaprolactone–polyethylene glycol methyl ether and polycaprolactone–chitosan electrospun mats potential for vascular tissue engineering

Recently, natural polymers are frequently comingled with synthetic polymers either by physical or chemical modification to prepare numerous tissue-engineered graft with promising biological function, strength, and stability. The aim of this study was to determine the efficiency for vascular tissue engineering of two distinctly different mats, one that comprised polycaprolactone–polyethylene glycol methyl ether and other that comprised polycaprolactone–chitosan. Nano/microfibrous mats prepared from electro-spinning were characterized for fiber diameter, porosity, wettability, and mechanical strength. Biological efficacy on both biodegradable mats was assessed by rat bone marrow mesenchymal stem cells, and polycaprolactone–polyethylene glycol methyl ether showed feasibility for use as an inner layer by inducing endothelial-specific gene expression and polycaprolactone–chitosan as an outer layer on dual layered without sacrificing tensile strength, small-diameter blood vessels. Therefore, scaffolds fabricated from this research could be potential sources for tissue-engineered vascular graft and could also overcome the well-known drawbacks, such as thrombogenicity and stenosis, in managing vascular disease.

Fabrication of Polycaprolactone/Polyurethane Loading Conjugated Linoleic Acid and Its Antiplatelet Adhesion

Polycaprolactone/polyurethane (PCL/PU) fibrous scaffold was loaded with conjugated linoleic acid (CLA) by electrospinning method to improve the hemocompatibility of the polymeric surface. Fourier Transform Infrared Spectroscopy (FT-IR) analysis and Scanning Electron Microscopy (SEM) observation were employed to characterize the chemical structure and the changing morphology of electrospun PCL/PU and PCL/PU loaded with CLA (PCL/PU-CLA) scaffolds. Platelet adhesion and whole blood clot formation tests were used to evaluate the effect of CLA on antithrombotic property of PCL/PU-CLA scaffold. Endothelial cells (EC) were also seeded on the scaffold to examine the difference in the morphology of EC layer and platelet attachment with and without the presence of CLA. SEM results showed that CLA supported the spreading and proliferation of EC and PCL/PU-CLA surface induced lower platelet adhesion as well as attachment of other blood cells compared to the PCL/PU one. These results suggest that electrospinning method can successfully combine the antiplatelet effects of CLA to improve hemocompatibility of PCL/PU scaffolds for applications in artificial blood vessels.

Fabrication of electrospun polycaprolactone coated withchitosan-silver nanoparticles membranes for wound dressing applications

In this study, electrospun polycaprolactone membrane coated with chitosan-silver nanoparticles (CsAg), electrospun polycaprolactone/chitosan/Ag nanoparticles, was fabricated by immersing the plasma-treated electrospun polycaprolactone membrane in the CsAg gel. The plasma modification of electrospun polycaprolactone membrane prior to CsAg coating was tested by methylene blue stain and scanning electron microscope. The presence of silver and chitosan on the plasma-treated electrospun polycaprolactone membrane was confirmed by energy-dispersive X-ray spectroscopy and FT-IR spectrum. Scanning electron microscope observation was employed to observe the morphology of the membranes. The release of Ag ions from electrospun polycaprolactone/chitosan/Ag nanoparticles membrane was tested using atomic absorption spectrometry. Electrospun polycaprolactone/chitosan/Ag nanoparticles membrane inherited advantages from both CsAg gel and electrospun polycaprolactone membrane such as: increasing biocompatibility, mechanical strength, and antibacterial activity against both Gram-negative and Gram-positive bacteria. Thus, this investigation introduces a highly potential membrane that can increase the efficacy of the wound dressing process.

A multi-layered vascular scaffold with symmetrical structure by bi-directional gradient electrospinning

Multi-layered scaffolds are advantageous in vascular tissue engineering, in consideration of better combination of biomechanics, biocompatibility and biodegradability than the scaffolds with single structure. In this study, a bi-directional gradient electrospinning method was developed to fabricate poly(l-lactide-co-caprolactone) (P(LLA-CL)), collagen and chitosan based tubular scaffold with multi-layered symmetrical structure. The multi-layered composite scaffold showed improved mechanical property and biocompatibility, in comparison to the blended scaffold using the same proportion of raw materials. Endothelialization on the multi-layered scaffold was accelerated owing to the bioactive surface made of pure natural materials. hSMCs growth showed the similar results because of its better biocompatibility. Additionally, fibers morphology change, pH value balance and long term mechanical support results showed that the gradient structure effectively improved biodegradability.