Biodegradable Polyurethane Elastomers Research Articles

Dynamic healing-assembly for biocompatible, biodegradable, stretchable and self-healing triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have great potential as power sources for on-skin and implantable electronics. However, most existing TENGs are not suitable for the above applications due to limited material choices, often characterized by rigidity, susceptibility to damage, biological incompatibility, and non-biodegradability. Herein, we developed a simple self-healing assembly strategy based on introducing dynamic Cu(II)-dimethylglyoxime-urethane groups into a biocompatible and biodegradable polyurethane elastomer, to simultaneously address the above obstacles. The coordination of Cu2+ with dynamic bonds significantly enhanced the mechanical properties of elastomer, resulting in a modulus of 9.4 MPa and toughness of 40.2 MJ/m3. These bonds also gave the elastomer skin-like self-healing capabilities, achieving a healing efficiency of 77.5 % at 80 °C. Subsequently, a highly stretchable and integrated triboelectric nanogenerator (Cu-POU TENG) with self-healing capabilities was developed. The Cu-POU TENG with an effective area of 1.5 × 1.5 cm2 produced an open-circuit voltage of 38 V in single-electrode mode. The Cu-POU TENG could restore its original electrical properties through self-healing after mechanical damage. Furthermore, the Cu-POU TENG exhibited biocompatibility and biodegradability, making it suitable for on-skin and implantable electronics. Notably, the Cu-POU TENG maintained a stable voltage output throughout the degradation process. The integration of self-healing feature enabled a sophisticated structure, allowing the Cu-POU TENG to function effectively as a motion sensor for tracking body movement. This Cu-POU TENG holds great potential for applications in on-skin and implantable electronics.

Gelatin/heparin coated bio-inspired polyurethane composite fibers to construct small-caliber artificial blood vessel grafts

Long-term patency and ability for revascularization remain challenges for small-caliber blood vessel grafts to treat cardiovascular diseases clinically. Here, a gelatin/heparin coated bio-inspired polyurethane composite fibers-based artificial blood vessel with continuous release of NO and biopeptides to regulate vascular tissue repair and maintain long-term patency is fabricated. A biodegradable polyurethane elastomer that can catalyze S-nitrosothiols in the blood to release NO is synthesized (NPU). Then, the NPU core-shell structured nanofiber grafts with requisite mechanical properties and biopeptide release for inflammation manipulation are fabricated by electrospinning and lyophilization. Finally, the surface of tubular NPU nanofiber grafts is coated with heparin/gelatin and crosslinked with glutaraldehyde to obtain small-caliber artificial blood vessels (ABVs) with the ability of vascular revascularization. We demonstrate that artificial blood vessel grafts promote the growth of endothelial cells but inhibit the growth of smooth muscle cells by the continuous release of NO; vascular grafts can regulate inflammatory balance for vascular tissue remodel without excessive collagen deposition through the release of biological peptides. Vascular grafts prevent thrombus and vascular stenosis to obtain long-term patency. Hence, our work paves a new way to develop small-caliber artificial blood vessel grafts that can maintain long-term patency in vivo and remodel vascular tissue successfully.

A facile preparation strategy of polycaprolactone (PCL)-based biodegradable polyurethane elastomer with a highly efficient shape memory effect

A polycaprolactone (PCL)-based biodegradable polyurethane elastomer with a highly efficient shape memory effect.

Low-Initial-Modulus Biodegradable Polyurethane Elastomers for Soft Tissue Regeneration.

The mechanical match between synthetic scaffold and host tissue remains challenging in tissue regeneration. The elastic soft tissues exhibit low initial moduli with a J-shaped tensile curve. Suitable synthetic polymer scaffolds require low initial modulus and elasticity. To achieve these requirements, random copolymers poly(δ-valerolactone-co-ε-caprolactone) (PVCL) and hydrophilic poly(ethylene glycol) (PEG) were combined into a triblock copolymer, PVCL-PEG-PVCL, which was used as a soft segment to synthesize a family of biodegradable elastomeric polyurethanes (PU) with low initial moduli. The triblock copolymers were varied in chemical components, molecular weights, and hydrophilicities. The mechanical properties of polyurethanes in dry and wet states can be tuned by altering the molecular weights and hydrophilicities of the soft segments. Increasing the length of either PVCL or PEG in the soft segments reduced initial moduli of the polyurethane films and scaffolds in dry and wet states. The polymer films are found to have good cell compatibility and to support fibroblast growth in vitro. Selected polyurethanes were processed into porous scaffolds by a thermally induced phase-separation technique. The scaffold from PU-PEG1K-PVCL6K had an initial modulus of 0.60 ± 0.14 MPa, which is comparable with the initial modulus of human myocardium (0.02-0.50 MPa). In vivo mouse subcutaneous implantation of the porous scaffolds showed minimal chronic inflammatory response and intensive cell infiltration, which indicated good tissue compatibility of the scaffolds. Biodegradable polyurethane elastomers with low initial modulus and good biocompatibility and processability would be an attractive alternative scaffold material for soft tissue regeneration, especially for heart muscle.

Synthesis and characterization of a conductive, biodegradable polyurethane elastomer

Event Abstract Back to Event Synthesis and characterization of a conductive, biodegradable polyurethane elastomer Cancan Xu1, 2, Fuqiang Liu3, Alejandro Bugarin4 and Yi Hong1, 2 1 University of Texas at Arlington, Department of Bioengineering, United States 2 University of Texas Southwestern Medical Center at Dallas, Joint Biomedical Engineering Program, United States 3 University of Texas at Arlington, Department of Material Science and Engineering, United States 4 University of Texas at Arlington, Department of Chemistry and Biochemistry, United States Introduction: Biodegradable conductive materials have promises to be applied for myocardium, nerve, muscle and bone tissue repair. The conductive hydrogel promoted growth and maturation of cardiac cells, and enhanced the electrical and mechanical coupling and contractile properties[1]. The conductive material also improved neurite outgrowths from the nerve cells by integrating biochemical and electrical stimulations[2]. However, biodegradable conductive elastomer was rarely reported. To address this limitation, we will utilize polyurethane chemistry to design a biodegradable polymer with elasticity and conductivity. Here, we combined polycaprolactone diol (PCL) as a soft segment, 1, 6-hexamethylene diisocyante (HDI) as a hard segment and aniline trimer as a chain extender to achieve a biodegradable polyurethane with electrical and electrochemical properties. The electrical and electrochemical properties, morphologies, mechanical properties, degradation behavior, electrical stability and cytocompatibility of the conductive polyurethane were evaluated. Materials and Methods: The conductive polyurethane (CPU) was synthesized by a two-step process (Fig. 1) and then fabricated into films doped with (1S)-(+)-10-camphorsulfonic acid (CSA) by solvent casting. The chemical structures of oxidized aniline trimer and CPU films were confirmed by 1H NMR, 13C NMR and FTIR, respectively. The morphologies of CPU films were observed on a scanning electron microscope (SEM). The electrical conductivities of CPU films at dry and wet states were measured by four-probe technique. The electroactivities of CPU films were characterized by UV-vis and cyclic voltammogram measurements. Mechanical properties of CPU films were measured on a MTS workstation with a head crossing rate of 10 mm/min. Cyclic stretching of CPU films at a maximum strain of 30% was tested at a constant rate of 10 mm/min for 10 cycles. The electrical stability of doped CPU films was carried out in cell culture medium under a constant DC voltage of 100±2 mV for 150 h. In vitro degradation of CPU films was detected in phosphate buffer solution (PBS) and lipase/PBS solutions. The electrical conductivity changes of CPU films were measured after degradation in 100 U/mL lipase/PBS solution for 3 and 7 d at 37 oC. The cytocompatibility of CPU films was evaluated using 3T3 fibroblasts. Results and Discussion: All CPU films showed good elasticity within 30% strain range, and their initial moduli increased with increasing CSA content. The roughness of CPU films increased with increasing CSA amount. The electrical conductivity of CPU films also enhanced with increasing CSA dopant amount, ranging from 2.7±0.9×10-10 to 4.4±0.6×10-7 S/cm at dry state and 4.2±0.5×10-8 to 7.3±1.5×10-5 S/cm at wet state. These values (wet) were in the semiconductive region. The redox peaks (0.17 V and 0.82 V) of CPU1.5 film (molar ratio of CSA:aniline trimer was 1.5:1) in cyclic voltammogram indicated its good electroactivity. The doped CPU film exhibited excellent electrical stability (91% of initial conductivity after 150 h charge) in cell culture medium. The degradation of CPU films became faster with increasing CSA dopant amount in either PBS or lipase/PBS solutions. After 7 d of enzymatic degradation, all CSA doped CPU films lost their conductivity. Their conductivities were similar to that of the undoped CPU film, which may attribute to the dopant leaching during degradation. The 3T3 fibroblasts proliferated and spread on all CPU films. There was no significantly difference on cell proliferation between CPU films and the tissue culture polystyrene, except for the CPU1.5 film. The CPU1.5 film having the highest dopant content showed less cell viability within 5 d incubation, which may be resulted from the rough surface and leached dopant. Conclusions: A biodegradable conductive polyurethane containing aniline trimer was synthesized. They had good elasticity conductive stability and biocompatibility, which are closely relevant with dopant amount. This biodegradable conductive polyurethane would find opportunities to be applied as tissue engineered scaffolds and smart drug release carriers. Research Enhancement Program from UT Arlington; Beginning-in-Aid award (#14BGIA20510066) from the American Heart Association

Thermal, mechanical and biodegradation properties of pure, epoxidized and methoxylated castor oil based polyurethane

A series of biodegradable polyurethane (BIOU) elastomers were obtained by chain extension of polyurethane (PU) prepolymer with the addition of castor oil (CAO), epoxidized CAO (ECAO) or methoxylated CAO (MCAO). The BIOU elastomers obtained were characterised by Fourier transform infrared, scanning electron microscopy, differential scanning calorimetry and tensile tester. The melting peak of BIOU became undetectable with an increase in the content of the chain extender regardless of its type. Some BIOU films, including BIOU-CAO16wt%, BIOU-ECAO16wt% and BIOU-MAO16wt%, showed elastomeric properties with higher tensile strength than pure PU. However the elongation at break and hardness of samples decreased with CAO, ECAO and MCAO content. The biodegradation was also measured by the modified Sturm test method of the BIOU films in a cultured medium with Pseudomonas aeruginosa E7 and Lysobacter soli LW1-1 strains at 37°C. As the increasing three types of chain-extenders the degree and rate of biodegradation of BIOU increased as compared with pure PU. But even then the biodegradability of BIOU by both the strains did not exceed 26% during the modified Sturm test for 31 days.

Thiol click modification of cyclic disulfide containing biodegradable polyurethane urea elastomers.

Although the thiol click reaction is an attractive tool for postpolymerization modification of thiolmers, thiol groups are easily oxidized, limiting the potential for covalent immobilization of bioactive molecules. In this study, a series of biodegradable polyurethane elastomers incorporating stable cyclic disulfide groups was developed and characterized. These poly(ester urethane)urea (PEUU-SS) polymers were based on polycaprolactone diol (PCL), oxidized dl-dithiothreitol (O-DTT), lysine diisocyanate (LDI), or butyl diisocyanate (BDI), with chain extension by putrescine. The ratio of O-DTT:PCL was altered to investigate different levels of potential functionalization. PEG acrylate was employed to study the mechanism and availability of both bulk and surface click modification of PEUU-SS polymers. All synthesized PEUU-SS polymers were elastic with breaking strengths of 38-45 MPa, while the PEUU-SS(LDI) polymers were more amorphous, possessing lower moduli and relatively small permanent deformations versus PEUU-SS(BDI) polymers. Variable bulk click modification of PEUU-SS(LDI) polymers was achieved by controlling the amount of reduction reagent, and rapid reaction rates occurred using a one-pot, two-step process. Likewise, surface click reaction could be carried out quickly under mild, aqueous conditions. Furthermore, a maleimide-modified affinity peptide (TPS) was successfully clicked on the surface of an electrospun PEUU-SS(BDI) fibrous sheet, which improved endothelial progenitor cell adhesion versus corresponding unmodified films. The cyclic disulfide containing biodegradable polyurethanes described provide an option for cardiovascular and other soft tissue regenerative medicine applications where a temporary, elastic scaffold with designed biofunctionality from a relatively simple click chemistry approach is desired.

Synthesis and 3D Printing of Biodegradable Polyurethane Elastomer by a Water‐Based Process for Cartilage Tissue Engineering Applications

Biodegradable materials that can undergo degradation in vivo are commonly employed to manufacture tissue engineering scaffolds, by techniques including the customized 3D printing. Traditional 3D printing methods involve the use of heat, toxic organic solvents, or toxic photoinitiators for fabrication of synthetic scaffolds. So far, there is no investigation on water-based 3D printing for synthetic materials. In this study, the water dispersion of elastic and biodegradable polyurethane (PU) nanoparticles is synthesized, which is further employed to fabricate scaffolds by 3D printing using polyethylene oxide (PEO) as a viscosity enhancer. The surface morphology, degradation rate, and mechanical properties of the water-based 3D-printed PU scaffolds are evaluated and compared with those of polylactic-co-glycolic acid (PLGA) scaffolds made from the solution in organic solvent. These scaffolds are seeded with chondrocytes for evaluation of their potential as cartilage scaffolds. Chondrocytes in 3D-printed PU scaffolds have excellent seeding efficiency, proliferation, and matrix production. Since PU is a category of versatile materials, the aqueous 3D printing process developed in this study is a platform technology that can be used to fabricate devices for biomedical applications.

Tailoring the degradation kinetics of poly(ester carbonate urethane)urea thermoplastic elastomers for tissue engineering scaffolds

Biodegradable elastomeric scaffolds are of increasing interest for applications in soft tissue repair and regeneration, particularly in mechanically active settings. The rate at which such a scaffold should degrade for optimal outcomes, however, is not generally known and the ability to select from similar scaffolds that vary in degradation behavior to allow such optimization is limited. Our objective was to synthesize a family of biodegradable polyurethane elastomers where partial substitution of polyester segments with polycarbonate segments in the polymer backbone would lead to slower degradation behavior. Specifically, we synthesized poly(ester carbonate)urethane ureas (PECUUs) using a blended soft segment of poly(caprolactone) (PCL) and poly(1,6-hexamethylene carbonate) (PHC), a 1,4-diisocyanatobutane hard segment and chain extension with putrescine. Soft segment PCL/PHC molar ratios of 100/0, 75/25, 50/50, 25/75, and 0/100 were investigated. Polymer tensile strengths varied from 14 to 34 MPa with breaking strains of 660–875%, initial moduli of 8–24 MPa and 100% recovery after 10% strain. Increased PHC content was associated with softer, more distensible films. Scaffolds produced by salt leaching supported smooth muscle cell adhesion and growth in vitro. PECUU in aqueous buffer in vitro and subcutaneous implants in rats of PECUU scaffolds showed degradation slower than comparable poly(ester urethane)urea and faster than poly(carbonate urethane)urea. These slower degrading thermoplastic polyurethanes provide opportunities to investigate the role of relative degradation rates for mechanically supportive scaffolds in a variety of soft tissue repair and reconstructive procedures.

Morphological and mechanical characteristics of the reconstructed rat abdominal wall following use of a wet electrospun biodegradable polyurethane elastomer scaffold

Although a variety of materials are currently used for abdominal wall repair, general complications encountered include herniation, infection, and mechanical mismatch with native tissue. An approach wherein a degradable synthetic material is ultimately replaced by tissue mechanically approximating the native state could obviate these complications. We report here on the generation of biodegradable scaffolds for abdominal wall replacement using a wet electrospinning technique in which fibers of a biodegradable elastomer, poly(ester urethane)urea (PEUU), were concurrently deposited with electrosprayed serum-based culture medium. Wet electrospun PEUU (wet ePEUU) was found to exhibit markedly different mechanical behavior and to possess an altered microstructure relative to dry processed ePEUU. In a rat model for abdominal wall replacement, wet ePEUU scaffolds (1 × 2.5 cm) provided a healing result that developed toward approximating physiologic mechanical behavior at 8 weeks. An extensive cellular infiltrate possessing contractile smooth muscle markers was observed together with extensive extracellular matrix (collagens, elastin) elaboration. Control implants of dry ePEUU and expanded polytetrafluoroethylene did not experience substantial cellular infiltration and did not take on the native mechanical anisotropy of the rat abdominal wall. These results illustrate the markedly different in vivo behavior observed with this newly reported wet electrospinning process, offering a potentially useful refinement of an increasingly common biomaterial processing technique.

Biodegradable polyurethane elastomers prepared from isocyanate‐terminated poly(ethylene adipate), castor oil, and glycerol

AbstractThe curing reaction of tolylene‐2,4‐diisocyanate‐terminated poly(ethylene adipate) (PEA‐TDI) with a mixture of castor oil (CO) and glycerol (GO) with a NCO/OH ratio of 1.0 at 150°C gave crosslinked polyurethane (CO/GO‐PU). All the polyurethanes were elastomeric materials at room temperature. The glass‐transition temperature of the CO/GO‐PU increased with decreasing CO/GO ratio. All the cured polyurethanes had a higher 5% weight loss temperature than PEA‐TDI. The tensile strength and modulus of the polyurethanes increased with decreasing CO/GO ratio, and tensile residual strain after 300% elongation for all the CO/GO‐PUs was almost 0. All the polyurethanes had biodegradability, when measured by a biochemical oxygen demand method in an aqueous medium using activated sludge. The rate of the biodegradation of the polyurethanes increased with an increase of CO/GO ratio. The crosslinked CO‐PU showed much higher biodegradability than the linear PEA‐TDI. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Surface characteristics of polyurethane elastomers based on chitin/1,4-butane diol blends

Biodegradable polyurethane elastomers with tunable hydrophobicity were synthesized by step-growth polymerization techniques using poly(ɛ-caprolactone) (PCL) and 4,4′-diphenylmethane diisocyanate (MDI). The prepolymer was extended with different mass ratios of chitin and 1,4-butane diol (BDO). The effect of chitin contents in chain extenders (CE) proportion on surface properties was studied and investigated. Incorporation of chitin contents into the final PU showed decrease in surface free energy and its polar component. Simultaneously, the work of water adhesion to polymer decreases significantly by increasing the chitin contents in the synthesized polymer. Contact angle measurement, water absorption and swelling behavior of the synthesized polyurethane samples were affected by varying the chitin contents in the chemical composition of the final PU. The interactions of the final PU films with solvents on the surface were displayed clear dependent on the contents of chitin in to the final polyurethane formulation. The results of different tests demonstrated that the synthesized products are a potential candidate as non-absorbable suture as previously investigated into their in vitro biocompatibility and non-toxicity [K.M. Zia, M. Zuber, I.A. Bhatti, M. Barikani, M.A. Sheikh, Int. J. Biol. Macromol. 44 (2009) 18–22].

Molecular engineering of chitin based polyurethane elastomers

Biodegradable polyurethane elastomers with potential for biomedical application as non-absorbable sutures with improved hydrophobic properties were synthesized by the reaction of poly(ε-caprolactone) (PCL) and 4,4′-diphenylmethane diisocyanate (MDI), extended with different mass ratio of chitin and 1,4-butane diol (BDO). Their molecular engineering and structural transition due to the changes of hydrogen bonding was confirmed by using FT-IR, 1H NMR and 13C NMR. Involvement of chitin was evidenced by the appearance of new signals in both 1H NMR and 13C NMR spectra, and very strong peak at 1724 cm −1 in FT-IR spectra. From the results, it was concluded that the reaction of the urethane group occurred mainly at C6 OH group of chitin in which strong intermolecular and intersheet hydrogen bonds are involved. Contact angle and surface tension measurement of the synthesized polyurethane as a function of chitin contents were investigated. Optimum hydrophobicity was obtained from elastomer extended with chitin in comparison to elastomers extended with BDO. The surface free energy was also affected by chemical composition of the final PU. Structure–property relationship for prepared elastomers showed that the main determining factors were hydrogen bonding, hydrophobicity and content of chitin in polyurethane backbone.

Synthesis and properties of biodegradable elastomeric epoxy modified polyurethanes based on poly( ε-caprolactone) and poly(ethylene glycol)

Biodegradable polyurethane elastomers with potential for applications in medical implants with tunable degradation rate and physical properties were synthesized from reaction of epoxy terminated polyurethanes (EUP) with 1,6-hexamethylene diamine (HMDA) as curing agent. Poly( ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as well as 1,6-hexamethylene diisocyanate (HDI) were used for preparation of isocyanate terminated polyurethanes which were subsequently blocked with glycidol to prepare EUPs. All materials were characterized by conventional methods, and their properties were studied fully. Results showed that elastomers based on PEG exhibit superior degradation rate and inferior mechanical properties in comparison to elastomers based on PCL. Optimum degradation rate and mechanical properties were obtained from elastomers made from mixture of PCL and PEG base EUPs.