Influence of well-defined hard segment length on the properties of medical segmented polyesterurethanes based on poly(ε-caprolactone-co-L-lactide) and aliphatic urethane diisocyanates

A Facile and Cost-Effective Method to Prepare Biodegradable Poly(ester urethane)s with Ordered Aliphatic Hard-Segments for Promising Medical Application as Long-Term Implants

The article below describes a simple methodology to prepare cost-effective biodegradable poly(ester urethane)s (PEUs) with ordered hard segments (OHS) for medical application as long-term implants. A low-cost diurethane diol (1,4-butanediol-hexanediisocyanate-1,4-butanediol, BHB) was first designed and synthesized. Consequently, the BHB was employed as a chain extender to react with NCO-terminated poly(ε-caprolactone) to obtain PEUs. The molecular structural formats for BHB and PEUs were defined through NMR, FT-IR, and MS together with GPC, while the influence of OHS content on physical/chemical features for casted PEU films was investigated. The introduction of OHS could contribute to forming denser hydrogen-bonds, and consequently produce a compact network structure, resulting in great tensile capacity, low water absorption, and slow hydrolytic degradation rate by PEU films. PEU-2.0 films, which possessed the highest OHS content within PEUs, exhibited 40.6 MPa tensile strength together with 477% elongation at break, 4.3 wt % equilibrium water absorption and only 29.5% weight loss post-12 months' degradation. In addition, cytotoxicity analysis of film extracts indicated that the cell viability of all PEUs containing OHS exceeded 75%, indicating good cytocompatibility. Due to outstanding tensile features, high biostability, nontoxic and absorbable degradation products and acceptable cytocompatibility, the cost-effective materials exhibited promising applications in the field of long-term implants.

Facile Method for Surface-Grafted Chitooligosaccharide on Medical Segmented Poly(ester-urethane) Film to Improve Surface Biocompatibility

In the paper, the chitooligosaccharide (CHO) was surface-grafted on the medical segmented poly(ester-urethane) (SPU) film by a facile two-step procedure to improve the surface biocompatibility. By chemical treatment of SPU film with hexamethylene diisocyanate under mild reaction condition, free -NCO groups were first introduced on the surface with high grafting density, which were then coupled with -NH₂ groups of CHO to immobilize CHO on the SPU surface (SPU-CHO). The CHO-covered surface was characterized by FT-IR and water contact angle test. Due to the hydrophilicity of CHO, the SPU-CHO possessed higher surface hydrophilicity and faster hydrolytic degradation rate than blank SPU. The almost overlapping stress-strain curves of SPU and SPU-CHO films demonstrated that the chemical treatments had little destruction on the intrinsic properties of the substrate. In addition, the significant inhibition of platelet adhesion and protein adsorption on CHO-covered surface endowed SPU-CHO an outstanding surface biocompatibility (especially blood compatibility). These results indicated that the CHO-grafted SPU was a promising candidate as blood-contacting biomaterial for biomedical applications.

Synthesis and characterization of ester-diol based polyurethane: a potentiality check for hypopharyngeal tissue engineering application

Abstract

Hypopharyngeal tissue engineering is increasing rapidly in this developing world. Tissue damage or loss needs the replacement by another biological or synthesized membrane using tissue engineering. Tissue engineering research is emerging to provide an effective solution for damaged tissue replacement. Polyurethane in tissue engineering has successfully been used to repair and restore the function of damaged tissues. In this context, Can polyurethane be a useful material to deal with hypopharyngeal tissue defects? To explore this, here ester diol based polyurethane (PU) was synthesized in two steps: firstly, polyethylene glycol 400 (PEG 400) was reacted with lactic acid to prepare ester diol, and then it was polymerized with hexamethylene diisocyanate. The physical, mechanical, and biological testing was done to testify the characterization of the membrane. The morphology of the synthesized membrane was investigated by using field emission scanning electron microscopy. Functional groups of the obtained membrane were characterized by fourier transform infrared spectroscopy spectroscopy. Several tests were performed to check the in vitro and in vivo biocompatibility of the membrane. A highly connected homogeneous network was obtained due to the appropriate orientation of a hard segment and soft segment in the synthesized membrane. Mechanical property analysis indicates the membrane has a strength of 5.15 MPa and strain 124%. The membrane showed high hemocompatibility, no cytotoxicity on peripheral blood mononuclear cell, and susceptible to degradation in simulated body fluid solution. Antimicrobial activity assessment has shown promising results against clinically significant bacteria. Primary hypopharyngeal cell growth on the PU membrane revealed the cytocompatibility and subcutaneous implantation on the back of Wistar rats were given in vivo biocompatibility of the membrane. Therefore, the synthesized material can be considered as a potential candidate for a hypopharyngeal tissue engineering application.

Graphic abstract

Degradable Poly(ether-ester-urethane)s Based on Well-Defined Aliphatic Diurethane Diisocyanate with Excellent Shape Recovery Properties at Body Temperature for Biomedical Application

The aim of this study is to offer a new class of degradable shape-memory poly(ether-ester-urethane)s (SMPEEUs) based on poly(ether-ester) (PECL) and well-defined aliphatic diurethane diisocyanate (HBH) for further biomedical application. The prepolymers of PECLs were synthesized through bulk ring-opening polymerization using ε-caprolactone as the monomer and poly(ethylene glycol) as the initiator. By chain extension of PECL with HBH, SMPEEUs with varying PEG content were prepared. The chemical structures of the prepolymers and products were characterized by GPC, 1H NMR, and FT-IR, and the effect of PEG content on the physicochemical properties (especially the shape recovery properties) of SMPEEUs was studied. The microsphase-separated structures of the SMPEEUs were demonstrated by DSC and XRD. The SMPEEU films exhibited good tensile properties with the strain at a break of 483%-956% and an ultimate stress of 23.1-9.0 MPa. Hydrolytic degradation in vitro studies indicated that the time of the SMPEEU films becoming fragments was 4-12 weeks and the introduction of PEG facilitates the degradation rate of the films. The shape memory properties studies found that SMPEEU films with a PEG content of 23.4 wt % displayed excellent recovery properties with a recovery ratio of 99.8% and a recovery time of 3.9 s at body temperature. In addition, the relative growth rates of the SMPEEU films were greater than 75% after incubation for 72 h, indicating good cytocompatibility in vitro. The SMPEEUs, which possess not only satisfactory tensile properties, degradability, nontoxic degradation products, and cytocompatibility, but also excellent shape recovery properties at body temperature, promised to be an excellent candidate for medical device applications.

Preparation, Physicochemical Properties, and Hemocompatibility of the Composites Based on Biodegradable Poly(Ether-Ester-Urethane) and Phosphorylcholine-Containing Copolymer

To improve the hemocompatibility of the biodegradable medical poly(ether-ester-urethane) (PEEU), containing uniform-size aliphatic hard segments that was prepared in our lab, a copolymer containing phosphorylcholine (PC) groups was blended with the PEEU. The PC-copolymer of poly(MPC-co-EHMA) (PMEH) was first obtained by copolymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-ethylhexyl methacrylate (EHMA), and then dissolved in mixed solvent of ethanol/chloroform to obtain a homogeneous solution. The composite films (PMPU) with varying PMEH content were prepared by solvent evaporation method. The physicochemical properties of the composite films with varying PMEH content were researched. The PMPU films exhibited higher thermal stability than that of the pure PEEU film. With the PMEH content increasing from 5 to 20 wt%, the PMPU films also possessed satisfied tensile properties with ultimate stress of 22.9-15.8 MPa and strain at break of 925-820%. The surface and bulk hydrophilicity of the films were improved after incorporation of PMEH. In vitro degradation studies indicated that the degradation rate increased with PMEH content, and it took 12-24 days for composite films to become fragments. The protein adsorption and platelet-rich plasma contact tests were adapted to evaluate the surface hemocompatibility of the composite films. It was found that the amount of adsorbed protein and adherent platelet on the surface decreased significantly, and almost no activated platelets were observed when PMEH content was above 5 wt%, which manifested good surface hemocompatibility. Due to the biodegradability, acceptable tensile properties and good surface hemocompatibility, the composites can be expected to be applied in blood-contacting implant materials.

Synthesis of a novel biomedical poly(ester urethane) based on aliphatic uniform-size diisocyanate and the blood compatibility of PEG-grafted surfaces

The purpose of this study is to offer a novel kind of polyurethane with improved surface blood compatibility for long-term implant biomaterials. In this work, the aliphatic poly(ester-urethane) (PEU) with uniform-size hard segments was prepared and the PEU surface was grafted with hydrophilic poly(ethylene glycol) (PEG). The PEU was obtained by chain-extension of poly(ɛ-caprolactone) (PCL) with isocyanate-terminated urethane triblock. Free amino groups were introduced onto the surface of PEU film via aminolysis with hexamethylenediamine, and then the NH₂-grafted PEU surfaces (PEU-NH₂) were reacted with isocyanate-terminated monomethoxyl PEG (MPEG-NCO) to obtain the PEG-grafted PEU surfaces (PEU-PEG). Analysis by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were performed to confirm the chemical structures of the chain extender, PCL, PEU, and PEU-PEG. Additionally, the influence of aminolysis on the physical-mechanical properties of PEU films was investigated. Two glass transition temperatures and a broad endothermic peak were observed in the differential scanning calorimetry curves of PEU, which demonstrated a microphase-separated and semicrystalline structure, respectively. The PEU-PEG film exhibited excellent mechanical properties with an ultimate stress of ∼39 MPa and an elongation at break of ∼1190%, which was slightly lower than that of PEU, indicating that the aminolysis has little influence on the tensile properties. Evaluation of the blood compatibility of the films by bovine serum albumin adsorption and the platelet adhesion test revealed that the PEG-grafted surface had improved resistance to protein adsorption and excellent resistance to platelet adhesion. In vitro degradation tests showed that the PEU-PEG film could maintain its mechanical properties for more than six months and only lost ∼25% weight after 18 months. Due to the excellent mechanical properties, good blood compatibility and slow degradability, this novel kind of polyurethane hold significant promise for long-term implant biomaterials, especially soft tissue augmentation and regeneration.

Photo-cross-linked biodegradable hydrogels based on n-arm-poly(ethylene glycol), poly(ε-caprolactone) and/or methacrylic acid for controlled drug release

In this paper, a novel kind of photo-cross-linked biodegradable hydrogels based on n-arm-poly(ethylene glycol) ( n = 2, 3, and 4) and poly(ɛ-caprolactone) was prepared by ultraviolet-initiated free radical polymerization. The resulting n-arm-poly(ethylene glycol)-poly(ɛ-caprolactone) and n-arm-poly(ethylene glycol)-poly(ɛ-caprolactone) acrylate (n-arm-PEG-PCL-AC, macromer) were characterized by proton nuclear magnetic resonance and fourier transform infrared spectra. The influences of arm numbers and concentration of macromer on the properties of hydrogel were researched systematically, and the results showed that the gelation time, equilibrium swelling ratio, in vitro degradation, and drug release rate decreased with the increase of arm numbers and concentration of macromer. The degradation and drug release rate could be controlled by varying the cross-linking density of hydrogel, indicating a potential application as controlled drug delivery system. Cytotoxicity test of hydrogel extracts was conducted using L929 mouse fibroblasts, and the relative growth rate exceeded 75% (cytotoxicity type: class 1) after incubation for 24 h, showing excellent cytocompatibility. In addition, the paper presented a pH-sensitive hydrogel (G4_pH) based on 4-arm-PEG-PCL-AC and acrylic acid, and the influences of pH value on swelling behaviors and in vitro drug release of the pH-sensitive hydrogel were examined. The hydrogels shrank under acidic condition and would swell in neutral or basic medium. The pH-dependent drug release behaviors indicated a promising application of the materials as oral drug delivery vehicles.