L-lysine Ethyl Ester Diisocyanate Research Articles

Synthesis and Biodegradation Test of a New Polyether Polyurethane Foam Produced from PEG 400, L-Lysine Ethyl Ester Diisocyanate (L-LDI) and Bis-hydroxymethyl Furan (BHMF).

In this paper we produced a bio-based polyether-polyurethane foam PU1 through the prepolymer method. The prepolymer was obtained by the reaction of PEG 400 with L-Lysine ethyl ester diisocyanate (L-LDI). The freshly prepared prepolymer was extended with 2,5-bis(hydroxymethyl)furan (BHMF) to produce the final polyurethane. The renewable chemical BHMF was produced through the chemical reduction of HMF by sodium borohydride. HMF was produced by a previously reported procedure from fructose using choline chloride and ytterbium triflate. To evaluate the degradation rate of the foam PU1, we tested the chemical stability by soaking it in a 10% sodium hydroxide solution. The weight loss was only 12% after 30 days. After that, we proved that enzymatic hydrolysis after 30 days using cholesterol esterase was more favoured than hydrolysis with NaOH, with a weight loss of 24%, probably due to the hydrophobic character of the PU1 and a better adhesion of the enzyme on the surface with respect to water. BHMF was proved to be of crucial importance for the enzymatic degradation assay at 37 °C in phosphate buffer solution, because it represents the breaking point inside the polyurethane chain. Soil burial degradation test was monitored for three months to evaluate whether the joint activity of sunlight, climate changes and microorganisms, including bacteria and fungi, could further increase the biodegradation. The unexpected weight loss after soil burial degradation test was 45% after three months. This paper highlights the potential of using sustainable resources to produce new biodegradable materials.

Renewable adhesives based on oleo-chemistry: From green synthesis to biomedical applications

Polyurethanes (PUs) are known as performing biomedical tissue adhesive materials. Adhesive applications can be based on synthesized PU-based prepolymers with highly reactive isocyanate (NCO) end-chains, which covalently react with surrounding living tissues. In this study, original sustainable macromolecular architectures were designed and tested. Different fully biobased polyfunctional NCO terminated prepolymers were synthesized from cotton oil (CO)-based polyols and different sustainable diisocyanates (l-Lysine ethyl ester diisocyanate (LDI), pentane diisocyanate (PDI) and dimeryl diisocyanate (DDI)). Then, two-component adhesive systems were prepared using the prepolymers and two chain extenders: 1,4-butanediol and 2-hydroxyethyl disulfide, to obtain in this latter case potential stimuli-responsive materials based on the disulfide bonds. Prepolymers' properties such as in-vitro biocompatibility, as well as two-components systems' adhesive behavior on muscle tissue were assessed. From these two-component systems, fully biobased PUs were obtained. The influence of the selected CO-based polyol, the diisocyanate and the chain extender on the physicochemical, thermal and mechanical properties of the corresponding PUs were studied. Moreover, their influence on biocompatibility and properties related to biomedical applications were discussed. The series of PUs exhibited a large range of properties such as Young's moduli at 25 and 37 °C, ranging from 0.4 to 22 MPa, and adequate hydrolytic and enzymatic degradations after nine weeks of incubation. LDI and PDI-based samples showed great interest in the preparation of such biomedical adhesives due to their good biocompatibilities.

Fully Bio-Based Thermosetting Polyurethanes from Bio-Based Polyols and Isocyanates.

The trend towards the utilization of bioresources for the manufacturing of polymers has led industry players to bring to the market new monomers. In this work, we studied 3 polyisocyanates and 2 polyols with high renewable carbon contents, namely L-lysine ethyl ester diisocyanate (LDI), pentamethylene-diisocyanate (PDI) isocyanurate trimer, and hexamethylene-diisocyanate (HDI) allophanate as the isocyanates, as well as castor oil and polypropanediol as the polyols. These monomers are commercially available at a large scale and were used in direct formulations or used as prepolymers. Thermosetting polymers with Tg values ranging from −41 to +21 °C and thermal stabilities of up to 300 °C were obtained, and the polymerization was studied using NMR, DSC, and rheology. Cured materials were also characterized using FTIR, DMA, gel content, and swelling index determinations. These high bio-based content materials can successfully be obtained and could be used as alternatives to petro-based materials.

Remarkable diastereomeric effect on thermoresponsive behavior of polyurethane based on lysine and tartrate ester derivatives.

This study describes the long-distance diastereomeric effect on thermoresponsive properties in water-soluble diastereomeric polyurethanes (PUs) composed of an l-lysine ethyl ester diisocyanate and a trimethylene glycol l-/d-tartrate ester, which have differences in spatial arrangements of the ethyl esters in the mirror image. The PUs based on l-lysine and l-/d-tartrate ester, named l-PU and d-PU, were synthesized with various number average molecular weights from 4700 to 13 100. In turbidimetry, l-PU showed a steep phase transition from 100%T to 0%T within about 10 °C at 4 g L−1, whereas d-PU did not change completely to 0%T transmittance even at 80 °C at 4 g L−1. In addition, the thermoresponsive properties of l-PU were less affected by concentration than those of d-PU. This long-distance diastereomeric effect on thermoresponsive behavior between l-PU and d-PU appeared in common among 6 samples with 4700 to 13 100 number average molecular weight. In the dynamic light scattering experiments at each transmittance, the hydrodynamic diameter (Dh) of l-PU increased up to 1000 nm, while the Dh of d-PU remained almost at 200–300 nm. The C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O stretching vibration of FT-IR spectra showed that d-PU has more hydrogen-bonded ester groups than L-PU. Thus, we speculated that the difference in the retention of polymer chains in the micelle to promote intermicellar bridging generates the long-distance diastereomeric effect.

Alkynyl-functionalized chain-extended PCL for coupling to biological molecules

Chemical functionalization of poly(ε-caprolactone) (PCL) enables a molecular integration of additional function. Here, we report an approach to incorporate reactive alkynyl side-groups by synthesizing a chain-extended PCL, where the reactive site is introduced through the covalently functionalizable chain extender 3-(prop-2-yn-1-yloxy)propane-1,2-diol (YPD). Chain-extended PCL with Mw of 101 to 385 kg·mol−1 were successfully synthesized in a one-pot reaction from PCL-diols with various molar masses, L-lysine ethyl ester diisocyanate (LDI) or trimethyl(hexamethylene)diisocyanate (TMDI), and YPD, in which the density of functionalizable groups and spacing between them can be controlled by the composition of the polymer. The employed diisocyanate compounds and YPD possess an asymmetric structure and form a non-crystallizable segment leaving the PCL crystallites to dominate the material’s mechanical properties. The mixed glass transition temperature Tg = −60 to −46 °C of the PCL/polyurethane amorphous phase maintains the synthesized materials in a highly elastic state at ambient and physiological conditions. Reaction conditions for covalent attachment in copper(I)-catalyzed azide-alkyne-cycloaddition reactions (CuAAC) in solution were optimized in a series of model reactions between the alkyne moieties of the chain-extended PCL and benzyl azide, reaching conversions over 95% of the alkyne moieties and with yields of up to 94% for the purified functionalized PCL. This methodology was applied for reaction with the azide-functionalized cell adhesion peptide GRGDS. The required modification of the peptide provides selectivity in the coupling reactions. The obtained results suggest that YPD could potentially be employed as versatile molecular unit for the creation of a variety of functionalizable polyesters as well as polyurethanes and polycarbonates offering efficient and selective click-reactions.

Toward Fully Bio-based and Supertough PLA Blends via in Situ Formation of Cross-Linked Biopolyamide Continuity Network

Dynamic vulcanization has been demonstrated to be a versatile and efficient way of improving impact toughness of PLA. However, the existing vulcanization routes usually suffer from complicated presynthetic procedures and use of nonrenewable modifiers as well as markedly enhanced melt-viscosity. Herein, using both biomass-derived hydrogenated dimer acid (HDA) and an excess molar amount of l-lysine ethyl ester diisocyanate (LDI) as toughening monomers, we have developed a facile yet highly effective diisocyanate method for the design of fully bio-based PLA blends with excellent impact toughness and melt-flowability. The in situ formation and self-cross-linking of flexible biopolyamide (HDAPA) toughener, as well as its reactive compatibilization with PLA, were accomplished in a single melt-blending step. When incorporating the amount of HDAPA from 15 to 20 wt % or higher, the resulting blends evolved from the network-like morphology to the bi-continuous one with the cross-linked HDAPA network. At HDAPA content higher than 10 wt %, a sharp and persistent brittle–ductile transition occurred with an equilibrium impact strength of over 1200 J/m, and elongation-at-break was over 400%. Moreover, such a tremendous toughening effect was accompanied by low melt-viscosity and enhanced PLA crystallization. The matrix yielding triggered by internal cavitation of percolated HDAPA domains, together with the pull-out of many in situ formed block copolymers located at the interfaces, was found to be the major impact-toughening mechanism. This work offers a novel and facile strategy for fabricating high-performance and fully bio-based polymeric materials.

Synthesis and Properties of a New Thermo-sensitive Random Polyurethane with Tunable LCSTs

In this paper, a new class of thermo-sensitive random polyurethanes (PGLDs) have been prepared by polymerization of L-lysineethyl ester diisocyanate with five homologous derivatives of ethylene glycols. The structure and properties of polyurethanes were characterized by various techniques. The molecular weight Mn and structure of polyurethanes are found to be particularly significant factors to their thermo-sensitivity. Four polyurethanes except poly(L-lysine ethyl ester diisocyanate-co-ethylene glycol) show a reversible phase transition at the lower critical solution temperature, which can be easily tuned in the range of 4–35°C by combination of the monomers. Unexpectedly, the increasing number of –CH2CH2O–units in the main-chain of polyurethanes apparently acts as the hydrophobicity in the solution. The catalyst-free-synthesized polyurethanes with Mn of about (1–2) × 104 g/mol responses to the external temperature. Stannous octoate-catalysted polyurethanes with Mn of (3–6) × 104 g/mol exhibit no thermo-sensitivity because of their strong intra/intermolecular interactions. In addition, the viability of HeLa cells in 0.01–100 μg/mL solution reached to 80% after 24 and 48 h of incubation, indicating no cytotoxicity for polyurethanes.

Pluronic-based dual-stimuli sensitive polymers capable of thermal gelation and pH-dependent degradation for in situ biomedical application.

Thermo-sensitive hydrogels are considered ideal for applications in the biomedical fields for their biocompatibility, flexibility, tissue-like water content, and reversible gelation property. By adjusting sufficient hydrophilic-hydrophobic balance in block copolymer structure, thermogel's critical gelation temperature can be modified to be near the physiological temperature, which makes it an appealing candidate for in situ gel depot. In this study, we report successful syntheses of novel multiple block copolymer compounds, denoted as dual-stimuli sensitive polymers (DSSPs), by copolymerizing Pluronic® P104 (7,100 Da) and 2,2-bis(aminoethoxy)propane (BAP) using diisocyanate linkers, L-lysine ethyl ester diisocyanate (DSSP-1) and 1,6-hexamethylene diisocyanate (DSSP-2). Through effective elongation of polymer chain lengths (DSSP-1: 41,760 Da, DSSP-2: 41,230 Da), Pluronic® P104's reversible thermal gelation properties were enhanced, as demonstrated by lowered critical gelation temperatures (DSSP-1: 36°C, DSSP-2: 38.7°C; 15 wt.%) that is near the physiological temperature. Furthermore, integration of acid-labile BAP allowed rapid pH-dependent degradation of the polymer, which was displayed by gel permeation chromatography (GPC) and release profiles of nile red and irinotecan from polymeric micelles and gels, respectively.

Non-toxic polyester urethanes based on poly(lactic acid), poly(ethylene glycol) and lysine diisocyanate

Poly(lactic acid)-based polymers are highly suitable for temporary biomedical applications, such as tissue support or drug delivery systems. Copolymers of different molecular weight based on poly(lactic acid) and poly(ethylene glycol) were prepared by polycondensation, catalysed by hydrochloric acid. A chain-extension reaction with l-lysine ethyl ester diisocyanate was employed afterwards to obtain polyester urethanes with enhanced properties. The GPC results showed that the molecular weights of the products reached about 50,000 g·mol−1 and the hydrolytic progress was rapid in the first 2 weeks; the drop in Mn equalled approximately 70%. Additionally, elemental analysis of the buffer medium proved that hydrolytic degradation was more rapid in the first stage. Tensile-strength testing revealed that ductility increased alongside reduced molecular weight of poly(ethylene glycol), also suggesting that polymer branching occurred due to side reactions of isocyanate. Based on the envisaged biomedical applications for these polymers, cytotoxicity tests were carried out and the cytotoxic effect was only moderate in the case of 100% polymer extract prepared according to ISO standard 10993-12. In their research, the authors focused on preparing metal-free, catalysed synthesis of polyester urethanes, which could prove useful to numerous biomedical applications.

Development of bioresorbable bilayered systems for application as affordable wound dressings

The objective of this work was the preparation and evaluation of a bioresorbable bilayered system for application in the treatment of dermal lesions. The system was based on a polyesterurethane as the external layer and a gelatin membrane as the internal layer. The polyesterurethane was synthesized from poly(ε-caprolactone), polyethylene glycol of 1 or 10 kDa as a hydrophilic component or Pluronic F127 as an amphiphilic component and l-lysine ethyl ester diisocyanate as an urethane precursor. Gelatin membrane was obtained by crosslinking with the naturally occurring crosslinker genipin. Three important points were addressed in this study: the physicochemical characterization of the system, the in vitro behaviour and the in vivo performance on a full-thickness wound defect of rat. The polyesterurethane containing polyethylene glycol of 10 kDa presented the optimum properties for the designed application as to be tested in animal experiments. The in vivo results showed good healing of the lesion with the formation of epidermis similar to normal rat skin. These promising results suggest the potential of this system to be used as an affordable wound dressing in the treatment of different dermal lesions.

Electrospun Poly(ester-Urethane)- and Poly(ester-Urethane-Urea) Fleeces as Promising Tissue Engineering Scaffolds for Adipose-Derived Stem Cells

An irreversible loss of subcutaneous adipose tissue in patients after tumor removal or deep dermal burns makes soft tissue engineering one of the most important challenges in biomedical research. The ideal scaffold for adipose tissue engineering has yet not been identified though biodegradable polymers gained an increasing interest during the last years. In the present study we synthesized two novel biodegradable polymers, poly(ε-caprolactone-co-urethane-co-urea) (PEUU) and poly[(L-lactide-co-ε-caprolactone)-co-(L-lysine ethyl ester diisocyanate)-block-oligo(ethylene glycol)-urethane] (PEU), containing different types of hydrolytically cleavable bondings. Solutions of the polymers at appropriate concentrations were used to fabricate fleeces by electrospinning. Ultrastructure, tensile properties, and degradation of the produced fleeces were evaluated. Adipose-derived stem cells (ASCs) were seeded on fleeces and morphology, viability, proliferation and differentiation were assessed. The biomaterials show fine micro- and nanostructures composed of fibers with diameters of about 0.5 to 1.3 µm. PEUU fleeces were more elastic, which might be favourable in soft tissue engineering, and degraded significantly slower compared to PEU. ASCs were able to adhere, proliferate and differentiate on both scaffolds. Morphology of the cells was slightly better on PEUU than on PEU showing a more physiological appearance. ASCs differentiated into the adipogenic lineage. Gene analysis of differentiated ASCs showed typical expression of adipogenetic markers such as PPARgamma and FABP4. Based on these results, PEUU and PEU meshes show a promising potential as scaffold materials in adipose tissue engineering.

Construction of Targeting-Clickable and Tumor-Cleavable Polyurethane Nanomicelles for Multifunctional Intracellular Drug Delivery

New strategies for the construction of versatile nanovehicles to overcome the multiple challenges of targeted delivery are urgently needed for cancer therapy. To address these needs, we developed a novel targeting-clickable and tumor-cleavable polyurethane nanomicelle for multifunctional delivery of antitumor drugs. The polyurethane was synthesized from biodegradable poly(ε-caprolactone) (PCL) and L-lysine ethyl ester diisocyanate (LDI), further extended by a new designed L-cystine-derivatized chain extender bearing a redox-responsive disulfide bond and clickable alkynyl groups (Cys-PA), and finally terminated by a detachable methoxyl-poly(ethylene glycol) with a highly pH-sensitive benzoic-imine linkage (BPEG). The obtained polymers show attractive self-assembly characteristics and stimuli-responsiveness, good cytocompatibility, and high loading capacity for doxorubicin (DOX). Furthermore, folic acid (FA) as a model targeting ligand was conjugated to the polyurethane micelles via an efficient click reaction. The decoration of FA results in an enhanced cellular uptake and improved drug efficacy toward FA-receptor positive HeLa cancer cells in vitro. As a proof-of-concept, this work provides a facile approach to the design of extracellularly activatable nanocarriers for tumor-targeted and programmed intracellular drug delivery.

Self-healing biodegradable poly(urea-urethane) elastomers based on hydrogen bonding interactions

Self-healing poly(urea-urethane)s (PUUs) showing a tolerance to mechanical damage are particularly desirable for high-performance elastomeric biomaterials. In this study a kind of biodegradable PUUs was synthesized from poly(ɛ-caprolactone) diol with L-lysine ethyl ester diisocyanate (LDI) extended with L-lysine ethyl ester dihydrochloride (LEED) in DMF and characterized by using 1H-NMR, FTIR, DSC, XRD, SEM and tensile tests. Interestingly, they exhibited a self-healing characteristic upon exposure to 37°C for as short as 30 min with the tensile strength keeping at 4.23 MPa and the elongation at break reaching to 627%. It is revealed that increasing the hard segment content in PUUs benefits the self-healing performance, and on the opposite increasing the soft segment content contributes to the biodegradability.

Layer-by-layer assembly of type I collagen and chondroitin sulfate on aminolyzed PU for potential cartilage tissue engineering application

In this paper, a two-step method was used to synthesize a biodegradable polyurethane (PU) composed of l-lysine ethyl ester diisocyanate (LDI), poly(ɛ-caprolactone) diols (PCL-diol) and 1,4:3,6-dianhydro-d-sorbitol (isosorbide). Amino groups were introduced onto the surface of the PU membrane by an amination reacting with 1,3-propanediamine to produce polycationic substratum. And then, type I collagen (Col) and chondroitin sulfate (CS) were deposited alternately on the polycationic substratum through layer-by-layer (LBL) assembly technology. The FTIR and 1H NMR results showed that the polyurethane was successfully synthesized. Rhodamine B isothiocyanate (RBITC) fluorescence spectrum indicated that amino groups were successfully introduced onto the PU surface. The results of quartz-crystal microbalance (QCM) and RBITC-Col fluorescence spectroscopy monitoring the LBL assemble process presented that the Col/CS deposited alternately on the PU surface. X-ray photoelectron spectroscopy (XPS) results displayed that the CS deposited on the PU surface as well. The surface of the assembled PU became even smoother observed from the surface morphology by atomic force microscopy (AFM) imaging. The hydrophilicity of the PU membrane was greatly enhanced though the modification of LBL assembly. The PU modified with the adsorption of Col/CS may be a potential application for cartilage tissue engineering due to its created mimicking chondrogenic environment.

New method for coupling collagen on biodegradable polyurethane for biomedical application

AbstractA two‐step method was used in this article to synthesize a novel biodegradable polyurethane (PU) composed by L‐lysine ethyl ester diisocyanate (LDI) hard segment, poly(ε‐caprolactone) diols (PCL‐diol) soft segment and 1,4:3,6‐dianhydro‐D‐sorbitol (isosorbide) chain extender. FTIR, 1H‐NMR results revealed the products had typical PU structures. GPC result showed that the number average molecular weight of the PU was 36,800 with the heterodisperse index of 2.18. DSC result displayed the PU melting temperature was 42°C. Surface aminolyzing of the PU membrane was performed by reacting it with 1,3‐propanediamine under alkaline condition. Then, type I collagen was grafted on the PU surface by EDC/NHS coupling method. Rhodamine B isothiocyanate (RBITC) fluorescence spectrum presented that both amino group (NH2) and type I collagen were successfully introduced on the PU surface. Furthermore, ninhydrin analysis showed that the maximum surface density of amino groups was 11.4 × 10−7 mol/cm2 after aminolyzing in 12% 1,3‐propanediamine aqueous solution for 1 h. Cell viability experiments indicated both PU‐NH2 and PU‐Col had low cytotoxicity and supported the ATDC5 cell's proliferation on them. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The degradation and biocompatibility of pH-sensitive biodegradable polyurethanes for intracellular multifunctional antitumor drug delivery

To obtain controllable stepwise biodegradable polymer for multifunctional antitumor drug carriers, pH-sensitive biodegradable polyurethanes were firstly synthesized using poly(ε-caprolactone) (PCL) and pH-sensitive poly(ε-caprolactone)–hydrazone–poly(ethylene glycol)–hydrazone–poly(ε-caprolactone) macrodiol (PCLH) as soft segment; l-lysine ethyl ester diisocyanate (LDI), l-lysine derivative tripeptide and 1,4-butandiol (BDO) as hard segment; and hydrazone-linked methoxyl-poly(ethylene glycol)(m-PEG-Hyd) as end-capper. Then, an extensive degradation process of the prepared pH-sensitive polyurethanes was investigated in vitro with proton nuclear magnetic resonance spectra (1H NMR), gel permeation chromatograph (GPC), scanning electron microscopy (SEM), and weight loss. It was found that the degradation of these polyurethanes occurred via the random hydrolytic ester cleavage along the PCL segments close to PEG segments in enzymatic solutions while the hydrazone bond in the polymer chain was more easily cleaved in acidic media, which was accelerated with decreasing pH value. Furthermore, the biocompatibility in vivo was evaluated in an intramuscular implantation model on Sprague–Dawley rats, using SEM and light microscopy. The result showed that the prepared polyurethanes can be easily degraded and the degradation products do not induce any adverse response from surrounding muscle tissues. Our work suggests that the prepared pH-sensitive polyurethanes could be promising materials as controllable biodegradable and non-cyctotoxic multifunctional carriers for active intracellular drug delivery.

Synthesis and micellization of new biodegradable phosphorylcholine‐capped polyurethane

AbstractTo obtain controllable and biocompatible drug carriers, a series of amphiphilic biodegradable multiblock polyurethanes end‐capped by phosphorylcholine were designed and synthesized using L‐lysine ethyl ester diisocyanate (LDI), poly(lactic acid)‐poly(ethylene glycol)‐poly(lactic acid) (PLA‐PEG‐PLA), 1,4‐butanediol (BDO), and 4‐hydroxy butyl phosphorylcholine (BPC) was used as end‐capper to improve their biocompatibility and provide them with tailored micellization characteristics. The resulting polyurethanes were fully characterized with proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT‐IR), gel permeation chromatograph (GPC), and differential scanning calorimetry (DSC). More importantly, these phosphorylcholine‐capped polyurethanes can self assemble into micelles that are smaller than 100 nm in diameter. Their particle sizes, size distributions, and zeta potentials can also be tailored by varying the phosphorylcholine content. The incorporation of phosphorylcholine into these polyurethanes has significantly affected their degree of microphase separation, bulk and micelle degradation rates. This work provides a new and facile approach to prepare amphiphilic block copolymer micelles with controllable performances, which could be useful for drug delivery and bioimaging applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis and characterization of novel biodegradable folate conjugated polyurethanes

In order to obtain targeting polyurethane micelle drug carriers, a series of biodegradable folate conjugated polyurethanes (FPUs) were synthesized using poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) as soft segments, l-lysine ethyl ester diisocyanate (LDI) and 1,3-propanediol (PDO) as hard segments, and folic acid–ethylenediamine conjugate (FA–EDA) as an end-capping reagent. The resultant FPUs were fully characterized by 1H NMR, Fourier-transform infrared (FTIR) spectroscopy, ultraviolet spectrophotometry (UV), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). These polymers can self-assemble into micelles in aqueous solutions confirmed by dynamic light scattering (DLS), pyrene fluorescence probe techniques, and transmission electron microscopy (TEM). The results indicated that the bulk structures and micellar properties of the prepared polyurethanes could be controlled by varying the PEG content in the soft segments. The present work provides a facile approach to prepare amphiphilic multiblock copolymers with tumor targeting moiety, which is a good candidate as biodegradable carriers for active intracellular drug delivery.

Electrospinning and biocompatibility evaluation of biodegradable polyurethanes based on L‐lysine diisocyanate and L‐lysine chain extender

A series of biodegradable polyurethanes (PUs) were synthesized using poly(ε-caprolactone) diol (PCL) to react with L-lysine ethyl ester diisocyanate (LDI) chain extend with L-lysine ethyl ester (LEE) in solution of DMF. The structure was characterized by gel permeation chromatography, ¹H-NMR, Fourier transform infrared, and DSC analyses. Mechanical property testing showed that their tensile strength rose with increasing the hard segment content with a maximum tensile strength of 34.43 ± 1.73 MPa. The average mass loss for the hydrolytic degradation was only about 13 % in 56 days while this value for the enzymatic degradation was around 95 % in 30 days. The morphological and biomechanical characters of the tubular scaffolds electrospun from the as-prepared PUs were also examined. As the solution concentration was varied from 10 to 18% (w/v), the fiber diameter was progressively increased, and the scaffold tensile strength was enhanced from 2.82 ± 0.16 MPa to 7.07 ± 0.44 MPa, the suture retention strength from 2.48 ± 0.33 to 8.38 ± 0.35 N, and the burst pressure strength from 72 ± 2 to 172 ± 2 kPa, all higher than those of native blood vessels. At the same time, the L-929 mouse fibroblasts (L-929) and human umbilical vein endothelial cells were used in cytotoxicity and cell-adhesion evaluations toward the electrospun scaffolds. The level of toxicity is less than level 1, and cells were found to attach well to and remain viable on the scaffolds.

Synthesis and Characterization of pH-Sensitive Biodegradable Polyurethane for Potential Drug Delivery Applications

To obtain a pH-sensitive multifunctional polyurethane micelle drug carrier, a novel pH-sensitive macrodiol containing acid-cleavable hydrazone linkers, poly(e-caprolactone)−hydrazone−poly(ethylene glycol)−hydrazone−poly(e-caprolactone) diol (PCL−Hyd−PEG−Hyd−PCL), was synthesized and characterized with proton nuclear magnetic resonance spectra (1H NMR). A series of pH-sensitive biodegradable polyurethanes (pHPUs) were designed and synthesized using pH-sensitive macrodiol, l-lysine ethyl ester diisocyanate (LDI) and l-lysine derivative tripeptide as chain extender, which can provide an active reaction site for the development of positive target polyurethane micelles for drug delivery. The bulk structures of the prepared polyurethanes were carefully characterized with 1H NMR, gel permeation chromatograph (GPC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The polyurethanes could be cleaved in acidic media (pH ∼ 4−6) as well as degraded in PBS and enzymatic solu...