Hemocompatible surface of electrospun nanofibrous scaffolds by ATRP modification

Surface functionalization of polyurethanes: A critical review

Synthetic polymers, particularly polyurethanes (PUs), have revolutionized bioengineering and biomedical devices due to their customizable mechanical properties and long-term stability. However, the inherent hydrophobic nature of PU surfaces arises common issues such as high friction, strong protein adsorption, and thrombosis, especially in the physiological environment of blood contact. To overcome these issues, researchers have explored various modification techniques to improve the surface biofunctionality of PUs. In this review, we have systematically summarized several typical surface modification methods including surface plasma modification, surface oxidation-induced grafting polymerization, isocyanate-based chemistry coupling, UV-induced surface grafting polymerization, adhesives-assisted attachment strategy, small molecules-bridge grafting, solvent evaporation technique, and hydrogen bonding interaction. Correspondingly, the advantages, limitations, and future prospects of these surface modification methods were discussed. This review provides an important guidance or tool for developing surface functionalized PUs in the fields of bioengineering and medical devices.

Engineering pH-sensitive erodible chitosan hydrogel composite containing bacteriophage: An interplay between hydrogel and bacteriophage against Staphylococcus aureus

Encapsulation of phages represents a key approach for improving phage stability and controlling phage delivery dosage. The hydrogel made from positively charged quaternized chitosan (QCS) and multivalent crosslinker, aldehyde-modified poly(xylitol sebacate)-co-poly(ethylene glycol) (APP) was introduced for the first time for drug (phage 44AHJD) delivery. The freeze-thawing (FT) treatment enhanced the porous structure and the stress resistance of native hydrogel with increased compression stress (stiffness) from 10 to 20 kPa. The stiffness of the phage-loaded hydrogel (FTP) was suitable for the proper release of phage particles and polymer chains, both working synergistically against bacterial growth. The FTP followed the Korsmeyer-Peppas model's anomalous diffusion of phage particles at different temperatures (30-45 °C) and pH (6.6-8.5) conditions. FTP was sensitive to pH, which released more phage particles at pH-neutral conditions, while the release under acidic and alkaline conditions was more based on gel degradation. The high biocompatibility of FTP hydrogel at its working concentration of 30 mg mL-1 was demonstrated through a hemolysis ratio of <2 %. Sixty percent of the total encapsulated phages and 6 mg mL-1 of hydrogel debris were released after 10 h of hydrogel submerge treatment, which can fight the growing bacteria and the emergence of phage-resistant bacteria.

Enhanced Anticoagulation of Hierarchy Liquid Infused Surfaces in Blood Flow

Liquid infused surfaces (LIS) hold remarkable potential in anticoagulation. However, liquid loss of LIS in the bloodstream remains a challenge toward its clinical application. Here, micronano hierarchy structures are obtained on the titanium alloy substrate by regulating the microspheres' distribution. When the gap between the microspheres is smaller than the diameter of the red blood cell (RBC), the LIS is more stable under the blood wash and presents a better anticoagulation performance. The proper interval is found to prevent the RBCs from entering the gap and remove the liquid on the surface. The retained thickness of the liquid film is measured by the atomic force microscopy (AFM) technique. The LIS is applied on the front guide vane of an artificial heart pump and exhibits significant improvement on anticoagulation in the blood circulation in vitro for 25 h. The techniques and findings can be used to optimize the anticoagulation performance of LIS-related biomedical implant devices.

Chitosan Hydrogel as Tissue Engineering Scaffolds for Vascular Regeneration Applications

Chitosan hydrogels have a wide range of applications in tissue engineering scaffolds, mainly due to the advantages of their chemical and physical properties. This review focuses on the application of chitosan hydrogels in tissue engineering scaffolds for vascular regeneration. We have mainly introduced these following aspects: advantages and progress of chitosan hydrogels in vascular regeneration hydrogels and the modification of chitosan hydrogels to improve the application in vascular regeneration. Finally, this paper discusses the prospects of chitosan hydrogels for vascular regeneration.

Biological Effects, Applications and Design Strategies of Medical Polyurethanes Modified by Nanomaterials

Polyurethane (PU) has wide application and popularity as medical apparatus due to its unique structural properties relationship. However, there are still some problems with medical PUs, such as a lack of functionality, insufficient long-term implantation safety, undesired stability, etc. With the rapid development of nanotechnology, the nanomodification of medical PU provides new solutions to these clinical problems. The introduction of nanomaterials could optimize the biocompatibility, antibacterial effect, mechanical strength, and degradation of PUs via blending or surface modification, therefore expanding the application range of medical PUs. This review summarizes the current applications of nano-modified medical PUs in diverse fields. Furthermore, the underlying mechanisms in efficiency optimization are analyzed in terms of the enhanced biological and mechanical properties critical for medical use. We also conclude the preparation schemes and related parameters of nano-modified medical PUs, with discussions about the limitations and prospects. This review indicates the current status of nano-modified medical PUs and contributes to inspiring novel and appropriate designing of PUs for desired clinical requirements.

Development of chloramphenicol wound dressing protein-based microparticles in chitosan hydrogel system for improved effectiveness of dermal wound therapy

Skin wounds have been reported to increase the number of microbial colonies susceptible to infection. Treatments using oral antibiotics have been limited due to their toxicity and hydrophobic characteristics. In this study, we developed a formulation of chloramphenicol microparticles (CPL MPs), which was modified into chitosan hydrogel to increase treatment efficiency in targeting infections and creating an optimal environment to support the healing process. CPL MPs were prepared by a cross-linker stabilized method using whey protein (WPI) biopolymer, and the CPL MPs hydrogel was designed using chitosan biopolymer. Based on the result, CPL-loaded MPs showed desired physical and encapsulation characteristics. In the in vitro study, drug release of CPL MPs in simulated wound fluid represented approximately 99.40 ± 7.01 % of the system after 24 h. The antibacterial activity of CPL-loaded MPs formulation (MIC value 12.5 μg/mL, MBC 25 μg/mL) was effective as MIC concentration increased. Furthermore, the formulation of CPL MPs into hydrogel showed a better dermatokinetic profile compared to hydrogel with pure CPL. Interestingly, the antibacterial activity of the ex vivo infection model showed that Staphylococcus aureus activity decreased by up to 99.98 % after 24 h administration of CPL MPs hydrogel when compared to pure-CPL hydrogel and blank hydrogel. These studies have confirmed that incorporating CPL MPs into hydrogel can provide a promising approach to skin infection treatment.

Surface Modification of Polyurethane Membrane with Various Hydrophilic Monomers and N-Halamine: Surface Characterization and Antimicrobial Properties Evaluation

Reducing microbial infections associated with biomedical devices or articles/furniture noted in a hospital or outpatient clinic remains a great challenge to researchers. Due to its stability and low toxicity, the N-halamine compound has been proposed as a potential antimicrobial agent. It can be incorporated into or blended with the FDA-approved biomaterials. Surface grafting or coating of N-halamine was also reported. Nevertheless, the hydrophobic nature associated with its chemical configuration may affect the microbial interactions with the chlorinated N-halamine-containing substrate. In this study, a polymerizable N-halamine compound was synthesized and grafted onto a polyurethane surface via a surface-initiated atom transfer radical polymerization (SI-ATRP) scheme. Further, using the sequential SI-ATRP reaction method, different hydrophilic monomers, namely poly (ethylene glycol) methacrylate (PEGMA), hydroxyethyl methacrylate (HEMA), and [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), were also grafted onto the polyurethane (PU) substrate before the N-halamine grafting reaction to change the surface properties of the N-halamine-modified substrate. It was noted that the chains containing the hydrophilic monomer and the polymerizable N-halamine compound were successfully grafted onto the PU substrate. The degree of chlorination was improved with the introduction of a hydrophilic monomer, except the HEMA. All of these hydrophilic monomer-containing N-halamine-modified PU substrates demonstrated a more than 2 log CFU reduction after microbial incubation. In contrast, the surface modified with N-halamine only exhibited significantly less antimicrobial efficacy instead. This is likely due to the synergistic effects caused by the reduced chlorine content, as well as the reduced surface interactions with the microbes.

Hemolytic, Biocompatible, and Functional Effect of Cellularized Polycaprolactone-Hydrolyzed Collagen Electrospun Membranes for Possible Application as Vascular Implants

In search of bioactive vascular prostheses that exhibit greater biocompatibility through the combination of natural and synthetic polymers, tissue engineering from a biomimetic perspective has proposed the development of three-dimensional structures as therapeutic strategies in the field of cardiovascular medicine. Techniques such as electrospinning allow obtaining of scaffolds that emulate the microarchitecture of the extracellular matrix of native vessels; thus, this study aimed to evaluate the biological influence of microarchitecture on polycaprolactone (PCL) and hydrolyzed collagen (H-Col) electrospun scaffolds, which have a homogeneous (microscale) or heterogeneous (micro-nanoscale) fibrillar structure. The hemolytic, biocompatible, and functional effect of the scaffolds in interaction with an in vitro fibroblast model was determined, in view of its potential use for vascular implants. Scaffolds were characterized by scanning electron microscopy and atomic force microscopy, Fourier transform infrared spectroscopy, wettability, static permeability, tensile test, and degradation. In addition, direct and indirect 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays were used to identify the cell viability of fibroblasts, fluorescence assays were performed to establish morphological changes of the cell nuclei, and the hemolytic effect of the scaffolds was calculated. Results showed that ethanol-treated biocompositescaffolds exhibited mass losses lower than 6.65% and slow wettability and absorption, resulting from an increase in secondary structures that contribute to the crystalline phase of H-Col. The scaffolds demonstrated stable degradation in saline during the incubation period because of the availability of soluble structures in aqueous media, and the inclusion of H-Col increased the elastic properties of the scaffold. As regards hemocompatibility, the scaffolds had hemolysis levels lower than 1%; moreover, in terms of biocompatible characteristics, scaffolds exhibited good adhesion, proliferation, and cell viability and insignificant changes in the circularity of the cell nuclei. However, scaffolds with homogeneous fibers showed cell agglomerates after 48 h of interaction. By contrast, permeability decreased as the incubation period progressed, because of the cellularization of the three-dimensional structure. In conclusion, multiscale scaffolds could exhibit a suitable behavior as a bioactive small-diameter vascular implant.

Cylindrical Polyurethane Scaffold Fabricated Using the Phase Inversion Method: Influence of Process Parameters on Scaffolds' Morphology and Mechanical Properties

This work presents a method of obtaining cylindrical polymer structures with a given diameter (approx. 5 mm) using the phase inversion technique. As part of the work, the influence of process parameters (polymer hardness, polymer solution concentration, the composition of the non-solvent solution, process time) on the scaffolds' morphology was investigated. Additionally, the influence of the addition of porogen on the scaffold's mechanical properties was analyzed. It has been shown that the use of a 20% polymer solution of medium hardness (ChronoFlex C45D) and carrying out the process for 24 h in 0:100 water/ethanol leads to the achievement of repeatable structures with adequate flexibility. Among the three types of porogens tested (NaCl, hexane, polyvinyl alcohol), the most favorable results were obtained for 10% polyvinyl alcohol (PVA). The addition of PVA increases the range of pore diameters and the value of the mean pore diameter (9.6 ± 3.2 vs. 15.2 ± 6.4) while reducing the elasticity of the structure (Young modulus = 3.6 ± 1.5 MPa vs. 9.7 ± 4.3 MPa).

Hemocompatibility Evaluation of Biomaterials-The Crucial Impact of Analyzed Area

The hemocompatibility of blood-contacting medical devices remains one of the major challenges in medical device development. A common tool for the analysis of adherent and activated platelets on materials following in vitro tests is microscopy. Currently, most researchers develop their own routines, resulting in numerous different methods that are applied. The majority of those (semi-)manual methods analyze only a very small fraction of the material surface (<1%), which neglects the inhomogeneity of platelet distribution and makes results hardly comparable. Within this study, we examined the relation between the fraction of analyzed sample area and the platelet adhesion result. By means of image segmentation and machine learning algorithms, 103 100 microscopy images were analyzed automatically. We discovered a crucial impact of the analyzed surface fraction and thus a misrepresentation of a surface's platelet adhesion unless up to 40% of the sample surface is analyzed. These findings underline the necessity of standardization in the field of in vitro hemocompatibility tests and analyses in particular and provide a first basis to make future tests more reliable and comparable.

Biological and mechanical characterization of biodegradable carbonyl iron powder/polycaprolactone composite material fabricated using three-dimensional printing for cardiovascular stent application

Biological and mechanical properties of biodegradable polymeric composite materials are strongly influenced by the choice of appropriate reinforcement in the polymer matrix. Non-compatibility of material in the vascular system could obstruct the way of the biological fluids. The concept of development of polymeric composite material for vascular implants is to provide enough support to the vessel and to restore the vessel in the natural state after degradation. In this research, the polycaprolactone composite materials (carbonyl iron powder/polycaprolactone) were developed by reinforcement of the 0%–2% of carbonyl iron powder using the solvent cast three-dimensional printing technique. The physicochemical properties of developed composites were characterized in conjunction with mechanical and biological properties. The mechanical characterizations were assessed by uniaxial tensile testing as well as flexibility testing. The results of mechanical testing assured that carbonyl iron powder/polycaprolactone composites have shown desirable properties for vascular implants. Besides the mechanical characterization, in vitro biological investigations of carbonyl iron powder/polycaprolactone were done for analyzing blood compatibility and cytocompatibility. The results revealed that the materials developed were biocompatible, less hemolytic, and having non-thrombogenic properties indicating the promising applications in the field of cardiovascular applications.

A multicompartment vascular implant of electrospun wintergreen oil/ polycaprolactone fibers coated with poly(ethylene oxide)

Background

The aim of the present study was to fabricate double layered scaffolds of electrospun polycaprolactone (PCL) and poly(ethylene oxide) (PEO). The electrospun PCL fibers were functionalized with wintergreen oil (WO) as a novel approach to prevent vascular grafts failure due to thrombosis by adjusting biomaterial–blood interactions.

Methods

PCL tubular scaffolds were prepared by electrospinning approach and coated with PEO as a hydrophilic polymer. The single and double layered scaffolds were characterized in terms of their morphological, chemical properties -as well as-hemocompatibility assays (i.e. prothrombin time, hemolysis percentage and platelets adhesion). Moreover, the antioxidant potential of WO-PCL samples were measured by 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical assay.

Results

The results demonstrated that incorporation of WO during the electrospinning process decreased the PCL fiber diameter. In addition, the prothrombine time assay shows that WO could be used to lower the electrospun PCL fiber tendency to induce blood clotting. Moreover, SEM observations of platelets adhesion of both single and double layered PCL/PEO scaffolds fiber shows an increase of platelets number, compared with the scaffolds containing WO.

Conclusions

The antioxidant potential and blood compatibility measurements of WO-PCL/PEO samples highlight the approach made so far as an ideal synthetic small size vascular grafts to overcome autogenous grafts shortages and drawbacks.

Performance of PEGylated chitosan and poly (L-lactic acid-co-ε-caprolactone) bilayer vascular grafts in a canine femoral artery model

The fabrication of a functional small-diameter vascular graft with good biocompatibility, in particular hemocompatibility, has become an urgent clinical necessity. We fabricated a native bilayer, small-diameter vascular graft using PEGylated chitosan (PEG-CS) and poly (L-lactic acid-co-ε-caprolactone; PLCL). To stabilize the inner layer, a PEG-CS blend with PLCL at ratio of 1:6 was casted on a round metal bar by a drip feed, and the outer layer, a PLCL blend with water-soluble PEG that acted as a sacrificial part to enhance pore size, was fabricated by electrospinning. The results showed excellent hemocompatibility and strong mechanical properties. In vitro, the degradation of the graft was evaluated by measuring the graft structure, mass loss rate, and changes in molecular weight. The results indicated that the graft had adequate support for the regeneration of blood vessels before collapse. An in vivo study was performed in a canine femoral artery model for up to 24 weeks, which demonstrated that the PEGylated bilayer grafts possessed excellent structural integrity, high compatibility with blood, good endothelial cell (EC) and smooth muscle cell (SMC) growth, and high expression levels of angiogenesis-related proteins, features that are highly similar to autologous blood vessels. Moreover, the results showed almost negligible calcification within 24 weeks. These findings confirm that the bilayer graft mimics native cells, thereby effectively improving vascular remodeling.

Controlled polymerization for the development of bioconjugate polymers and materials

Conjugates of various biopolymers with synthetic polymers were preparedvialiving radical polymerization. The conjugates have precise structures and potential for novel biofunctional materials.

Multifunctionalized polyethersulfone membranes with networked submicrogels to improve antifouling property, antibacterial adhesion and blood compatibility

Intensive efforts have been employed in modifying biomedical membranes. Among them, blending is recognized as a simple method. However, the conventional blending materials commonly lead to an insufficient modification, which is mainly caused by the poor miscibility between the blending materials and the matrixes, the elution of the hydrophilic materials from the matrixes during the use and storage, and the insufficient surface enrichment of the blending materials. Aiming to solve the abovementioned disadvantages, we developed novel polyethersulfone/poly(acrylic acid-co-N-vinyl-2-pyrrolidone) networked submicrogels (PES/P(AA-VP) NSs), which were blended with PES to enhance the antifouling properties, antibacterial adhesion and haemocompatible properties of PES membranes. As results, the PES/P(AA-VP) NSs showed good miscibility with the PES matrix, and hydrophilic submicrogels would enrich onto the membrane surface during the phase inversion process due to the surface segregation. The entanglement between the PES matrix and the networked submicrogels would effectively limit the elution of the submicrogels. In conclusion, the modified PES membranes prepared by blending with the PES/P(AA-VP) NSs might draw great attention for the application in haemodialysis fields.

Fabrication and Characterization of Flexible Medical-Grade TPU Filament for Fused Deposition Modeling 3DP Technology

The possibility of using additive manufacturing (AM) in the medicine area has created new opportunities in health care. This has contributed to a sharp increase in demand for 3D printers, their systems and materials that are adapted to strict medical requirements. We described herein a medical-grade thermoplastic polyurethane (S-TPU) which was developed and then formed into a filament for Fused Deposition Modeling (FDM) 3D printers during a melt-extrusion process. S-TPU consisting of aliphatic hexamethylene 1,6-diisocyanate (HDI), amorphous α,ω-dihydroxy(ethylene-butylene adipate) (PEBA) and 1,4 butandiol (BDO) as a chain extender, was synthesized without the use of a catalyst. The filament (F-TPU) properties were characterized by rheological, mechanical, physico-chemical and in vitro biological properties. The tests showed biocompatibility of the obtained filament as well as revealed no significant effect of the filament formation process on its properties. This study may contribute to expanding the range of medical-grade flexible filaments for standard low-budget FDM printers.

Surface modification and endothelialization of polyurethane for vascular tissue engineering applications: a review

Cardiovascular implants, especially vascular grafts made of synthetic polymers, find wide clinical applications in the treatment of cardiovascular diseases. However, cases of failure still exist, notably caused by restenosis and thrombus formation. Aiming to solve these problems, various approaches to surface modification of synthetic vascular grafts have been used to improve both the hemocompatibility and long-term patency of artificial vascular grafts. Surface modification using hydrophilic molecules can enhance hemocompatibility, but this may limit the initial vascular endothelial cell adhesion. Therefore, the improvement of endothelialization on these grafts with specific peptides and biomolecules is now an exciting field of research. In this review, several techniques to improve surface modification and endothelialization on vascular grafts, mainly polyurethane (PU) grafts, are summarized, together with the recent development and evolution of the different strategies: from the use of PEG, zwitterions, and polysaccharides to peptides and other biomolecules and genes; from in vitro endothelialization to in vivo endothelialization; and from bio-inert and bio-active to bio-mimetic approaches.

Surface, thermal and hemocompatible properties of novel single stage electrospun nanocomposites comprising polyurethane blended with bio oilTM

In this work, the physicochemical and blood compatibility properties of prepared PU/Bio oil nanocomposites were investigated. Scanning electron microscope (SEM) studies revealed the reduction of mean fiber diameter (709 ± 211 nm) compared to the pristine PU (969 nm ± 217 nm). Fourier transform infrared spectroscopy (FTIR) analysis exposed the characteristic peaks of pristine PU. Composite peak intensities were decreased insinuating the interaction of the bio oilTM with the PU. Contact angle analysis portrayed the hydrophobic nature of the fabricated patch compared to pristine PU. Thermal gravimetric analysis (TGA) depicted the better thermal stability of the novel nanocomposite patch and its different thermal behavior in contrast with the pristine PU. Atomic force microscopy (AFM) analysis revealed the increase in the surface roughness of the composite patch. Activated partial thromboplastin time (APTT) and prothrombin time (PT) signified the novel nanocomposite patch ability in reducing the thrombogenicity and promoting the anticoagulant nature. Finally the hemolytic percentage of the fabricated composite was in the acceptable range revealing its safety and compatibility with the red blood cells. To reinstate, the fabricated patch renders promising physicochemical and blood compatible nature making it a new putative candidate for wound healing application.

Manufacture and property research of heparin grafted electrospinning PCU artificial vascular scaffolds

PCU (polycarbonate polyurethane) is supposed to be an ideal elastomer for manufacturing artificial vessel scaffold with perfect mechanical strength and biocompatibility. Surface grafting by heparin sodium can increase its anticoagulant hemorrhagic, achieving a better application in artificial vessels. Artificial vessels were preliminarily prepared by electrostatic spinning, treated by NH₃ plasma and cross-linked with the anticoagulant heparin sodium chemically. Performances of the PCU-Hep (heparin sodium grafted purethane artificial vessels) artificial vessel were calculated through the physical and chemical property tests, evaluation of blood and biocompatibility. Results manifested that heparin sodium was successfully grafted to the vascular surface, porosity, pore diameter and water permeability of the vascular prosthesis fitted the requirements of artificial vessels, the blood test results demonstrated that the vascular material had a low hemolysis, in vitro cytotoxicity experiment and animal experiments proved an excellent biocompatibility. Thus the heparin sodium grafted electrospinning vessels could reduce intravascular thrombus and had potential clinical application.

Bioreducible, hydrolytically degradable and targeting polymers for gene delivery

Recently, synthetic gene carriers have been intensively developed owing to their promising application in gene therapy and considered as a suitable alternative to viral vectors because of several benefits. But cationic polymers still face some problems like low transfection efficiency, cytotoxicity, and poor cell recognition and internalization. The emerging engineered and smart polymers can respond to some changes in the biological environment like pH change, ionic strength change and redox potential, which is beneficial for cellular uptake. Redox-sensitive disulfide based and hydrolytically degradable cationic polymers serve as gene carriers with excellent transfection efficiency and good biocompatibility owing to degradation in the cytoplasm. Additionally, biodegradable polymeric micelles with cell-targeting function are recently emerging gene carriers, especially for the transfection of endothelial cells. In this review, some strategies for gene carriers based on these bioreducible and hydrolytically degradable polymers will be illustrated.

Compared to the amniotic membrane, Wharton's jelly may be a more suitable source of mesenchymal stem cells for cardiovascular tissue engineering and clinical regeneration

BACKGROUND

The success of developing cardiovascular tissue engineering (CTE) grafts greatly needs a readily available cell substitute for endothelial and interstitial cells. Perinatal annexes have been proposed as a valuable source of mesenchymal stem cells (MSCs) for tissue engineering and regenerative medicine. The objective of the present study is to evaluate the potential of human Wharton's jelly MSCs (WJ-MSCs) and amniotic membrane MSCs (AM-MSCs) as a seeding cell in CTE and cardiovascular regenerative medicine.

METHODS

WJ-MSCs/AM-MSCs were isolated and characterized in vitro according to their morphology, proliferation, self-renewal, phenotype, and multipotency. More importantly, the characteristics of hemocompatibility, extracellular matrix deposition, and gene expression and viability of both MSCs were investigated.

RESULTS

Fibroblast-like human WJ-MSCs and AM-MSCs were successfully isolated and positively expressed the characteristic markers CD73, CD90, and CD105 but were negative for CD34, CD45, and HLA-DR. Both MSCs shared trilineage differentiation toward the adipogenic, osteogenic, and chondrogenic lineages. The proliferative and self-renewal capacity of WJ-MSCs was significantly higher than that of AM-MSCs (P < 0.001). WJ-MSCs provided comparable properties of antiplatelet adhesion and did not activate the coagulation cascade to endothelial cells. However, aggregated platelets were visualized on the surface of AM-MSCs-derived cell sheets and the intrinsic pathway was activated. Furthermore, WJ-MSCs have superior properties of collagen deposition and higher viability than AM-MSCs during cell sheet formation.

CONCLUSIONS

This study highlights that WJ-MSCs could act as a functional substitute of endothelial and interstitial cells, which could serve as an appealing and practical single-cell source for CTE and regenerative therapy.

Differential Adhesive and Bioactive Properties of the Polymeric Surface Coated with Graphene Oxide Thin Film

Surface engineering of implantable devices involving polymeric biomaterials has become an essential aspect for medical implants. A surface enhancement technique can provide an array of unique surface properties that improve its biocompatibility and functionality as an implant. Polyurethane-based implants that have found extensively acclaimed usage as an implant in biomedical applications, especially in the area of cardiovascular devices, still lack any mechanism to ward off bacterial or platelet adhesion. To bring out such a defense mechanism we are proposing a surface modification technique. Graphene oxide (GO) in very thin film form was wrapped onto the electrospun fibroporous polycarbonate urethane (PCU) membrane (GOPCU) by a simple method of electrospraying. In the present study, we have developed a simple single-step method for coating a polymeric substrate with a thin GO film and evaluated the novel antiadhesive activity of these films. SEM micrographs after coating showed the presence of very thin GO films over the PCU membrane. On the GOPCU surface, the contact angle was shifted by ∼30°, making the hydrophobic PCU surface slightly hydrophilic, while Raman spectral characterization and mapping showed the presence and distribution of GO over 75% of the membrane. A reduced platelet adhesion on the GOPCU surface was observed; meanwhile, bacterial adhesion also got reduced by 85% for Staphylococcus aureus (Gram positive, cocci) and 64% for Pseudomonas aeruginosa (Gram negative, bacilli). A cell adhesion study conducted using mammalian fibroblast cells projected its proliferation percentage in a MTT assay, with 82% cell survival on PCU and 86% on GOPCU after 24 h culture, while a study for an extended period of 72 h showed 87% of survival on PCU and 88% on GOPCU. This plethora of functionalities by a simple modification technique makes thin GO films a self-sufficient surface engineering material for future biomedical applications.

Electrospun Regenerated Cellulose Nanofiber Membranes Surface-Grafted with Water-Insoluble Poly(HEMA) or Water-Soluble Poly(AAS) Chains via the ATRP Method for Ultrafiltration of Water

Electrospun nanofiber membranes (ENMs) have demonstrated promising applications for water purification primarily due to high water flux and low degree of fouling. However, the equivalent/apparent pore sizes of as-electrospun ENMs are in microns/submicrons; therefore, the ENMs can only be directly utilized for microfiltration applications. To make regenerated cellulose (RC) ENMs for ultrafiltration applications, atom transfer radical polymerization (ATRP) was studied to graft polymer chains onto the surface of RC nanofibers; specifically, monomers of 2-hydroxyethyl methacrylate (HEMA) and sodium acrylate (AAS) were selected for surface-grafting water-insoluble and water-soluble polymer chains onto RC nanofibers, respectively. With prolonging of the ATRP reaction time, the resulting surface-modified RC ENMs had reduced pore sizes. The water-insoluble poly(HEMA) chains coated the surface of RC nanofibers to make the fibers thicker, thus decreasing the membrane pore size and reducing permeability. On the other hand, the water-soluble poly(AAS) chains did not coat the surface of RC nanofibers; instead, they partially filled the pores to form gel-like structures, which served to decrease the effective pore size, while still providing elevated permeability. The surface-modified RC ENMs were subsequently explored for ultrafiltration of ∼40 nm nanoparticles and ∼10 nm bovine serum albumin (BSA) molecules from water. The results indicated that the HEMA-modified RC membranes could reject/remove more than 95% of the nanoparticles while they could not reject any BSA molecules; in comparison, the AAS-modified RC membranes had complete rejection of the nanoparticles and could even reject ∼58% of the BSA molecules.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Design and development of polysaccharide hemostatic materials and their hemostatic mechanism

The formation of stable blood clots or hemostasis is essential to prevent major blood loss and death from excessive bleeding.

Co-self-assembly of cationic microparticles to deliver pEGFP-ZNF580 for promoting the transfection and migration of endothelial cells

The gene transfection efficiency of polyethylenimine (PEI) varies with its molecular weight. Usually, high molecular weight of PEI means high gene transfection, as well as high cytotoxicity in gene delivery in vivo. In order to enhance the transfection efficiency and reduce the cytotoxicity of PEI-based gene carriers, a novel cationic gene carrier was developed by co-self-assembly of cationic copolymers. First, a star-shaped copolymer poly(3(S)-methyl-morpholine-2,5-dione-co-lactide) (P(MMD-co-LA)) was synthesized using D-sorbitol as an initiator, and the cationic copolymer (P(MMD-co-LA)-g-PEI) was obtained after grafting low-molecular weight PEI. Then, by co-self-assembly of this cationic copolymer and a diblock copolymer methoxy-poly(ethylene glycol) (mPEG)-b-P(MMD-co-LA), microparticles (MPs) were formed. The core of MPs consisted of a biodegradable block of P(MMD-co-LA), and the shell was formed by mPEG and PEI blocks. Finally, after condensation of pEGFP-ZNF580 by these MPs, the plasmids were protected from enzymatic hydrolysis effectively. The result indicated that pEGFP-ZNF580-loaded MP complexes were suitable for cellular uptake and gene transfection. When the mass ratio of mPEG-b-P(MMD-co-LA) to P(MMD-co-LA)-g-PEI reached 3/1, the cytotoxicity of the complexes was very low at low concentration (20 μg mL-1). Additionally, pEGFP-ZNF580 could be transported into endothelial cells (ECs) effectively via the complexes of MPs/pEGFP-ZNF580. Wound-healing assay showed that the transfected ECs recovered in 24 h. Cationic MPs designed in the present study could be used as an applicable gene carrier for the endothelialization of artificial blood vessels.

Fabrication and hemocompatibility assessment of novel polyurethane-based bio-nanofibrous dressing loaded with honey and Carica papaya extract for the management of burn injuries

Management of burn injury is an onerous clinical task since it requires continuous monitoring and extensive usage of specialized facilities. Despite rapid improvizations and investments in burn management, >30% of victims hospitalized each year face severe morbidity and mortality. Excessive loss of body fluids, accumulation of exudate, and the development of septic shock are reported to be the main reasons for morbidity in burn victims. To assist burn wound management, a novel polyurethane (PU)-based bio-nanofibrous dressing loaded with honey (HN) and Carica papaya (PA) fruit extract was fabricated using a one-step electrospinning technique. The developed dressing material had a mean fiber diameter of 190±19.93 nm with pore sizes of 4–50 µm to support effective infiltration of nutrients and gas exchange. The successful blending of HN- and PA-based active biomolecules in PU was inferred through changes in surface chemistry. The blend subsequently increased the wettability (14%) and surface energy (24%) of the novel dressing. Ultimately, the presence of hydrophilic biomolecules and high porosity enhanced the water absorption ability of the PU-HN-PA nanofiber samples to 761.67% from 285.13% in PU. Furthermore, the ability of the bio-nanofibrous dressing to support specific protein adsorption (45%), delay thrombus formation, and reduce hemolysis demonstrated its nontoxic and compatible nature with the host tissues. In summary, the excellent physicochemical and hemocompatible properties of the developed PU-HN-PA dressing exhibit its potential in reducing the clinical complications associated with the treatment of burn injuries.

Tailoring in vitro biological and mechanical properties of polyvinyl alcohol reinforced with threshold carbon nanotube concentration for improved cellular response

The development of living bone tissue constructs with structural, mechanical and functional similarities to natural bone are the major challenges in bone tissue engineering.

REDV–polyethyleneimine complexes for selectively enhancing gene delivery in endothelial cells

Gene therapy provides a new strategy for promoting endothelialization, and rapid endothelialization has attracted increasing attention for inhibiting thrombosis and restenosis in artificial vascular implants.

REDV Peptide Conjugated Nanoparticles/pZNF580 Complexes for Actively Targeting Human Vascular Endothelial Cells

Herein, we demonstrate that the REDV peptide modified nanoparticles (NPs) can serve as a kind of active targeting gene carrier to condensate pZNF580 for specific promotion of the proliferation of endothelial cells (ECs). First, we synthesized a series of biodegradable amphiphilic copolymers by ring-opening polymerization reaction and graft modification with REDV peptide. Second, we prepared active targeting NPs via self-assembly of the amphiphilic copolymers using nanoprecipitation technology. After condensation with negatively charged pZNF580, the REDV peptide modified NPs/pZNF580 complexes were formed finally. Due to the binding affinity toward ECs of the specific peptide, these REDV peptide modified NPs/pZNF580 complexes could be recognized and adhered specifically by ECs in the coculture system of ECs and human artery smooth muscle cells (SMCs) in vitro. After expression of ZNF580, as the key protein to promote the proliferation of ECs, the relative ZNF580 protein level increased from 15.7% to 34.8%. The specificity in actively targeting ECs of the REDV peptide conjugated NPs/pZNF580 complexes was still retained in the coculture system. These findings in the present study could facilitate the development of actively targeting gene carriers for the endothelialization of artificial blood vessels.

Modular and Versatile Spatial Functionalization of Tissue Engineering Scaffolds through Fiber-Initiated Controlled Radical Polymerization

Native tissues are typically heterogeneous and hierarchically organized, and generating scaffolds that can mimic these properties is critical for tissue engineering applications. By uniquely combining controlled radical polymerization (CRP), end-functionalization of polymers, and advanced electrospinning techniques, a modular and versatile approach is introduced to generate scaffolds with spatially organized functionality. Poly-ε-caprolactone is end functionalized with either a polymerization-initiating group or a cell-binding peptide motif cyclic Arg-Gly-Asp-Ser (cRGDS), and are each sequentially electrospun to produce zonally discrete bilayers within a continuous fiber scaffold. The polymerization-initiating group is then used to graft an antifouling polymer bottlebrush based on poly(ethylene glycol) from the fiber surface using CRP exclusively within one bilayer of the scaffold. The ability to include additional multifunctionality during CRP is showcased by integrating a biotinylated monomer unit into the polymerization step allowing postmodification of the scaffold with streptavidin-coupled moieties. These combined processing techniques result in an effective bilayered and dual-functionality scaffold with a cell-adhesive surface and an opposing antifouling non-cell-adhesive surface in zonally specific regions across the thickness of the scaffold, demonstrated through fluorescent labelling and cell adhesion studies. This modular and versatile approach combines strategies to produce scaffolds with tailorable properties for many applications in tissue engineering and regenerative medicine.

Surface tailoring for selective endothelialization and platelet inhibition via a combination of SI-ATRP and click chemistry using Cys-Ala-Gly-peptide

Surface tailoring is an attractive approach to enhancing selective endothelialization, which is a prerequisite for current vascular prosthesis applications. Here, we modified polycarbonate urethane (PCU) surface with both poly(ethylene glycol) and Cys-Ala-Gly-peptide (CAG) for the purpose of creating a hydrophilic surface with targeting adhesion of endothelial cells (ECs). In the first step, PCU-film surface was grafted with poly(ethylene glycol) methacrylate (PEGMA) to covalently tether hydrophilic polymer brushes via surface initiated atom transfer radical polymerization (SI-ATRP), followed by grafting of an active monomer pentafluorophenyl methacrylate (PFMA) by a second ATRP. The postpolymerization modification of the terminal reactive groups with allyl amine molecules created pendant allyl groups, which were subsequently functionalized with cysteine terminated CAG-peptide via photo-initiated thiol-ene click chemistry. The functionalized surfaces were characterized by water contact angle and XPS analysis. The growth and proliferation of human ECs or human umbilical arterial smooth muscle cells on the functionalized surfaces were investigated for 1, 3 and 7 day/s. The results indicated that these peptide functionalized surfaces exhibited enhanced EC adhesion, growth and proliferation. Furthermore, they suppressed platelet adhesion in contact with platelet-rich plasma for 2h. Therefore, these surfaces with EC targeting ligand could be an effective anti-thrombogenic platform for vascular tissue engineering application.

CREDVW-Linked Polymeric Micelles As a Targeting Gene Transfer Vector for Selective Transfection and Proliferation of Endothelial Cells

Nowadays, gene transfer technology has been widely used to promote endothelialization of artificial vascular grafts. However, the lack of gene vectors with low cytotoxicity and targeting function still remains a pressing challenge. Herein, polyethylenimine (PEI, 1.8 kDa or 10 kDa) was conjugated to an amphiphilic and biodegradable diblock copolymer poly(ethylene glycol)-b-poly(lactide-co-glycolide) (mPEG-b-PLGA) to prepare mPEG-b-PLGA-g-PEI copolymers with the aim to develop gene vectors with low cytotoxicity while high transfection efficiency. The micelles were prepared from mPEG-b-PLGA-g-PEI copolymers by self-assembly method. Furthermore, Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide was linked to micelle surface to enable the micelles with special recognition for endothelial cells (ECs). In addition, pEGFP-ZNF580 plasmids were condensed into these CREDVW-linked micelles to enhance the proliferation of ECs. These CREDVW-linked micelle/pEGFP-ZNF580 complexes exhibited low cytotoxicity by MTT assay. The cell transfection results demonstrated that pEGFP-ZNF580 could be transferred into ECs efficiently by these micelles. The results of Western blot analysis showed that the relative ZNF580 protein level in transfected ECs increased to 76.9%. The rapid migration of transfected ECs can be verified by wound healing assay. These results indicated that CREDVW-linked micelles could be a suitable gene transfer vector with low cytotoxicity and high transfection efficiency, which has great potential for rapid endothelialization of artificial blood vessels.

Nanoparticles complexed with gene vectors to promote proliferation of human vascular endothelial cells

Amphiphilic block copolymers containing biodegradable hydrophobic segments of depsipeptide based copolymers have been synthesized and explored as gene carriers for enhancing proliferation of endothelial cells in vitro. These polymers form nanoparticles (NPs) with positive charges on their surface, which could condense recombinant plasmids of enhanced green fluorescent protein plasmid and ZNF580 gene (pEGFP-ZNF580) and protect them against DNase I. ZNF580 gene is efficiently transported into EA.hy926 cells to promote their proliferation, whereby the transfection efficiency of NPs/pEGFP-ZNF580 is approximately similar to that of Lipofectamine 2000. These results indicate that the NPs might have potential as a carrier for pEGFP-ZNF580, which could support endothelialization of cardiovascular implants.

Targeting REDV peptide functionalized polycationic gene carrier for enhancing the transfection and migration capability of human endothelial cells

Targeting gene engineering should be considered as an effective method for promoting endothelialization of vascular grafts. Herein, we developed a targeting REDV peptide functionalized polycationic gene carrier for carrying the pEGFP-ZNF580 plasmid with the aim of enhancing the transfection and migration capability of human endothelial cells. This polycationic gene carrier with the REDV peptide (mPEG-P(LA-co-CL)-PEI-REDV) was prepared by the conjugation of the Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide with the amphiphilic block copolymer methoxy poly(ethylene glycol) ether-poly(l-lactide-co-ε-caprolactone)-poly(ethyleneimine) (mPEG-P(LA-co-CL)-PEI). mPEG-P(LA-co-CL)-PEI nanoparticles (NP) and mPEG-P(LA-co-CL)-PEI-REDV nanoparticles (REDV-NP) were formed by the self-assembly of the corresponding polycationic polymers, and then their pEGFP-ZNF580 complexes were prepared via the electrostatic interaction with pEGFP-ZNF580 plasmids, respectively. Gel electrophoresis results show that the targeted REDV-NPs could compress pEGFP-ZNF580 plasmids into stable complexes and protect the plasmids against desoxyribonuclease degradation. MTT assay indicates that these targeted REDV-NP/pEGFP-ZNF580 complexes exhibit better cyto-compatibility than the non-targeted NP/pEGFP-ZNF580 complexes and the control PEI 1800 Da/pEGFP-ZNF580 complexes. In vitro transfection experiments and western blot analysis of EA.hy926 endothelial cells show that the pEGFP-ZNF580 plasmid expression and the relative protein level transfected by targeted REDV-NP/pEGFP-ZNF580 complexes are roughly consistent with that transfected by PEI 25 kDa/pEGFP-ZNF580 complexes. More importantly, the scratch wound assay results demonstrate that the migration capability of EA.hy926 cells has been improved significantly by the expression of the pEGFP-ZNF580 plasmid. Our results indicate that the polycationic polymer with functional REDV peptides can be a potential candidate as a pEGFP-ZNF580 plasmid delivery carrier and may be used in the endothelialization of vascular grafts.

Antimicrobial surfaces grafted random copolymers with REDV peptide beneficial for endothelialization

Multifunctional surfaces have been created by surface modification and click reactions. These surfaces possess excellent hemocompatibility and endothelialization, as well as effective antimicrobial activity.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.

Electrospun scaffolds of silk fibroin and poly(lactide-co-glycolide) for endothelial cell growth

Electrospun scaffolds of silk fibroin (SF) and poly(lactide-co-glycolide) (PLGA) were prepared to mimic the morphology and chemistry of the extracellular matrix. The SF/PLGA scaffolds were treated with ethanol to improve their usability. After ethanol treatment the scaffolds exhibited a smooth surface and uniform fibers. SF transformed from random coil conformation to β-sheet structure after ethanol treatment, so that the SF/PLGA scaffolds showed low hydrophilicity and dissolving rate in water. The mechanical properties and the hydrophilicity of the blended fibrous scaffolds were affected by the weight ratio of SF and PLGA. During degradation of ethanol-treated SF/PLGA scaffolds in vitro, the fibers became thin along with the degradation time. Human umbilical vein endothelial cells (HUVECs) were seeded onto the ethanol-treated nanofibrous scaffolds for cell viability, attachment and morphogenesis studies. These SF/PLGA scaffolds could enhance the viability, spreading and attachment of HUVECs. Based on these results, these ethanol-treated scaffolds are proposed to be a good candidate for endothelial cell growth.