Influence of aorta extracellular matrix in electrospun polycaprolactone scaffolds

Cardiovascular disease is the leading cause of mortality worldwide. Therefore, new research strategies for the treatment of cardiovascular disease are required. Previously, extracellular matrices (ECMs) have been used alongside polymers to generate hybrid bioscaffolds. Herein, we propose combining aortic ECMs with a polycaprolactone electrospun scaffold and biomechanically evaluating the scaffolds. We electrospun three scaffolds with varying ECM concentrations and found that increasing the ECM concentration leads to decreased stiffness at low strains, increased elasticity at high strain, reduction in failure strain, and an increase in yield strength. We also noted a decrease in water droplet contact angle with the increasing ECM concentration. Furthermore, we found that all three scaffolds were capable of maintaining human umbilical vein endothelial cell attachment and survival. These findings show the wide spectrum of mechanical properties that can be achieved through the addition of different concentrations of ECM into the fibers. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48181.     

Electrospun poly(L‐lactic acid)/hydroxyapatite composite fibrous scaffolds for bone tissue engineering

Poly(L ‐lactic acid) (PLLA) is one of the most studied synthetic biodegradable polymeric materials as a bone graft substitute. Taking into account the osteoconductive property of hydroxyapatite (HAp), we prepared fibrous matrices of PLLA without and with HAp particles in amounts of 0.25 or 0.50% (w/v, based on the volume of the base 15% w/v PLLA solution in 70:30 v/v dichloromethane/tetrahydrofuran). These fibrous matrices were assessed for their potential as substrates for bone cell culture. The presence of HAp in the composite fibre mats was confirmed using energy dispersive X‐ray spectroscopy mapping. The average diameters of both neat PLLA and PLLA/HAp fibres, as determined using scanning electron microscopy, ranged between 2.3 and 3.5 µm, with the average spacing between adjacent fibres ranging between 5.7 and 8.5 µm. The porosity of these fibrous membranes was high (ca 97–98%). A direct cytotoxicity evaluation with L929 mouse fibroblasts indicated that the neat PLLA fibre mats released no substance at a level that was toxic to the cells. The presence of HAp particles at 0.50% w/v in the PLLA fibrous scaffolds not only promoted the attachment and the proliferation of MC3T3‐E1 mouse pre‐osteoblastic cells, but also increased the expression of osteocalcin mRNA and the extent of mineralization after the cells had been cultured on the scaffolds for 14 and 21 days, respectively. The results obtained suggested that the PLLA/HAp fibre mats could be materials of choice for bone tissue engineering. Copyright © 2009 Society of Chemical Industry     

Functionalization of multiwalled carbon nanotubes with amphiphilic poly(aspartic acid)

A new method to functionalize multiwalled carbon nanotubes (MWNTs) with amphiphilic poly(aspartic acid) was investigated. The amphiphilic polymer (PASP‐C16) was synthesized by thermal condensation and aminolysis by hexadecylamine, followed by hydrolysis of the remaining succinimide units in the polymer backbone. The functionalization of MWNTs was achieved by physical adsorption of the biopolymer onto the surfaces of MWNTs. Ultraviolet‐visible ( UV‐vis) spectra showed that the functionalized MWNTs had a good aqueous dispersity and solubility. The interaction of PASP‐C16 with MWNTs was investigated by analyzing X‐ray diffraction (XRD) patterns, circular dichroism (CD), spectra and high‐resolution transmission electron microscopy ( HRTEM ). From the XRD patterns, it can be known that the aggregate of PASP‐C16 due to intermolecular interaction between hexadecyl chains has been reduced when the polymer interacting with MWNTs. CD spectra indicated that the interaction of hexadecyl chains of PASP‐C16 with the wall of MWNTs is the major interaction between PASP‐C16 and MWNTs, and MWNTs were covered by the poly(aspatic acid) backbone. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Preparation and physical properties of N‐defunctionalized derivatives of poly(aspartic acid)

A number of N‐substituted poly(aspartic acid)s was prepared under mild conditions using the silylation–alkylation technique. Their physical properties were studied. Free swelling capacity (FSC) tests were performed for polymers obtained by crosslinking the parent poly(aspartic acid) as well as its defunctionalized derivatives. The hypothesis that H‐bonding is critical in superabsorbency was demonstrated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 85–90, 2001     

Degradation behavior of hydrogel based on crosslinked poly(aspartic acid)

The degradation behavior of hydrogel based on poly(aspartic acid) (PASP) which crosslinked by 1, 6‐hexamethylene diamine (HD) was studied in α‐chymotrypsin solution. The degradation behaviors of PASP under different crosslinking levels were evaluated as a function of biodegradation time by monitoring the changes of crosslinking density, molecular weight, rheological behavior, interior morphology, mass loss, and swelling ratio. It was found that the degradation behaviors relied heavily on the crosslinking density which calculated from the Flory‐Rehner equation. A pseudo first‐kinetic equation was proposed to model the mass loss behavior and the degradation rate constant was calculated under different crosslinking levels. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison of poly(aspartic acid) hydrogel and poly(aspartic acid)/gelatin complex for entrapment and pH‐sensitive release of protein drugs

Biodegradable poly(aspartic acid) (PASP) hydrogel and PASP/gelatin complex were prepared to evaluate their potential application as pH‐sensitive matrices for controlled protein release. Entrapment of myoglobin (Mb) and its release were compared between the two types of carriers. It was found that incorporation of Mb into PASP hydrogel strongly depended on the medium pH and NaCl concentration, and was time‐consuming. However, complete entrapment of Mb into PASP/gelatin complex was found within pH ranged from 2.5 to 4.0, which was concomitant with the formation of PASP/gelatin complex. By adjusting Mb feed ratio, Mb entrapment in the complex can be up to 31.54% (by weight) with high loading efficiency (96.2%). Gradual release of Mb from PASP hydrogel was observed within pH 2.0–7.4, while Mb release from PASP/gelatin complex was negligible within pH 2.0–4.2 for 4 days. In addition, pulsatile Mb release can be achieved by combining polyanhydride with pH‐sensitive PASP/gelatin complex, while the device composed of polyanhydride and PASP hydrogel is mechanically unstable. PASP/gelatin complex formed by electrostatic interactions is superior to the single‐component PASP hydrogel synthesized by chemical cross‐linking as pH‐sensitive matrices for controlled protein release when entrapment of proteins and pH‐sensitivity of protein release are concerned. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

聚天冬氨酸与含磷阻垢剂复配产品的阻垢性能

聚天冬氨酸作为阻垢剂具有可完全生物降解的优越特性，但聚天冬氨酸本身的阻垢效果无法达到市售阻垢剂的水平。研究了聚天冬氨酸与市售的含磷阻垢剂复配产品的阻垢性能。结果表明，在相同阻垢剂用量的条件下，用质量分数为50％的聚天冬氨酸与50％的HEDP或ATMP，PBTCA复配产品的阻碳酸钙垢性能分别与100％的HEDP或ATMP，PBTCA的性能一致，说明用聚天冬氨酸可以取代这些含磷阻垢剂的50％。     

Innovative spectral investigations on the thermal-induced poly(aspartic acid)

Two-dimensional (2D) correlation FTIR spectroscopy was used to investigate the dynamic mechanism of poly(aspartic acid) during the heating process. According to the 2D asynchronous correlation spectra, the CO vibration band of Amide I was separated into three peaks at 1637, 1645 and 1677 cm⁻¹, assigned to α helical, random coil and β antiparallel conformation, respectively. And α helical structure would transform into the more ordered and stable conformation of β antiparallel in heating. In the region of 3700-2700 cm⁻¹, the H-contained groups were analyzed; the loosening of hydroxyl is found to change prior to the NH-related hydrogen bonds and the conformational reorganization of hydrocarbon chains.     

Salt-, pH- and temperature-responsive semi-interpenetrating polymer network hydrogel based on poly(aspartic acid) and poly(acrylic acid)

In this study, a novel salt-, pH- and temperature-responsive semi-interpenetrating network (semi-IPN) hydrogel, composed of poly(aspartic acid) (PAsp) and poly(acrylic acid) (PAAc), was prepared. PAsp/PAAc semi-IPN hydrogel being ionic in nature, the swelling behavior was significantly influenced by various swelling medium. The structure of the triply responsive hydrogel was studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and the salt-, temperature- and pH-sensitivities were investigated through measuring equilibrium swelling ratios in various environmental solutions. The results indicate that there is a structure of polyelectrolyte complex in the hydrogel, and that the responsive behaviors of this hydrogel to alternating changes in inorganic salt (different physiological bio-fluids), pH and temperature are improved because of the incorporation of PAsp. In addition, during the repeatable swelling and shrinkage period, the semi-IPN hydrogel shows suitable mechanical strength. The salt-, pH- and temperature-responsive hydrogel will have wider applications in biomedical areas.     

聚醚改性聚天冬氨酸减水剂的制备及其性能

摘要：以聚琥珀酰亚胺（PSI）和端氨基聚醚M2005（M2005）为原料,合成了聚醚改性聚天冬氨酸减水剂（PEMPASP）,采用FTIR对PEMPASP进行了表征,探讨了不同减水剂及其用量对水泥净浆流动度和胶砂强度的影响;通过对TOC、Zeta电位、XRD以及TG-DSC分析,研究了PEMPASP减水剂的作用机理。结果表明,当采用nPSI:nM2005为1:0.14所制备的PEMPASA,在掺量为水泥的0.35%时,水泥的净浆流动度比掺加聚天冬氨酸（PASP）的水泥净浆流动度提高了189%,在用量为0.25%时,水泥胶砂抗折强度比空白水泥增长了15.6%,比含有PASP的水泥胶砂增长了17%;由于在PASP分子上引入长侧链聚醚链,改变了减水剂分子上的电荷密度和侧链结构,影响了减水剂对水泥颗粒的静电作用和位阻作用,进而改善了吸附、分散以及水泥的水化作用,提高了减水剂的综合性能。     

Electrospun crosslinked poly(acrylic acid) fiber constructs: towards a synthetic model of the cortical layer of nerve

In an attempt to mimic properties of the polyanionic nanofibrous cortical layer (ectoplasm) of nerve, tube‐shaped poly(acrylic acid) (PAA) nanofiber constructs were prepared via electrospinning. The influence of processing parameters on the morphology of the electrospun PAA nanofibers was systematically investigated. Smooth and uniform PAA nanofibers with average fiber diameter of 820 nm were produced at a concentration of 4 wt% with a flow rate of 0.8 mL h^?1 when a high voltage of 15 kV was applied. Water‐stable PAA nanofibers were obtained by thermally crosslinking PAA with ethylene glycol. The resulting tubes were neutralized to the sodium polyacrylate form and were shown to undergo reversible and abrupt length changes upon titration with CaCl₂ followed by titration with sodium citrate. The sharpness of the length transition was found to be highly dependent upon the bathing NaCl concentration and the operation temperature. It is suggested that electrospun PAA may be a promising candidate as a key element of an abiotic macromolecular mimic of selected properties of axons. © 2014 Society of Chemical Industry     

13C n.m.r. relaxation study of poly(aspartic acid)

¹³C n.m.r. relaxation parameters (T₁, line widths and NOE factors) and chemical shifts were measured in dependence on pH for several samples of poly(α-l-Asp) differing in molecular mass and polydispersity, and for samples of poly(α,β-d,l-Asp) differing in molecular mass. Poly(α-l-Asp) dissolved at pH 9 and acidified to pH 6-4 can appear in two different forms, A and B. In n.m.r. spectra these forms differ mainly by the width of the bands of side chain carbons which is larger in form A. Conditions for a reproducible generation of either of the two forms were not found although the effect of molecular mass (3–6 × 10⁴), polydispersity, sample concentration (2.0-0.2 mol l^?1), temperature of dissolution (4°C–37°C), concentration of NaCl (0–4 mol l^?1) or rate of acidification (1 pH unit s^?1 week^?1) and rate of mixing were investigated. The dynamics of poly(α,β-d,l-Asp) is almost unaffected by change of pH. The relaxation parameters of poly(α-l-Asp) at pH 9 and 4 differ more in form A than in form B. Analysis of relaxation data for the methine carbon of poly(α-l-Asp) in form A by means of the isotropic model with a log x² distribution of correlation times yields a correlation time of 1 ns at pH 4. This indicates that the dynamics of the backbone is dominated by rapid segmental motions even at pH 4. The dependence of chemical shifts on pH indicates that the chemical shift values are determined mainly by the ionization of the carboxyl group in the side chain rather than by a conformational transition. The evaluated relaxation parameters suggest, when compared with those of polypeptides with known conformational behaviour, that the two forms of poly(α-l-Asp) differ in conformation (α-helix, β-structure).     

不同分散剂对聚天冬氨酸吸水树脂性能的影响

在聚天冬氨酸(PAsp)吸水树脂制备过程中,分别以去离子水、甲醇、乙醇、正丁醇为分散剂加入到聚琥珀酰亚胺(PSI)溶液中使之成为均匀体系,在该体系中加入交联剂1,6-己二胺制备了具有三维网络结构的环保型高吸水树脂,并利用FTIR、SEM、TG等手段对其微观结构进行了测试。通过对比4种分散剂对PAsp吸水树脂吸液性能的影响,得出以下结论:不论是何种分散剂,适量的单独加入均可显著提高吸水树脂的吸液倍率,其中以去离子水为优,在蒸馏水和生理盐水中的吸液倍率分别达945 g/g和94 g/g;以正丁醇作分散剂可明显提高吸水树脂的吸液速率,吸液7 h即可达溶胀平衡;以m(去离子水)∶m(正丁醇)=7∶3的混合溶剂作为分散剂时,树脂的吸水性能较纯水与纯正丁醇要好,吸水6 h后即达吸液平衡,吸水倍率可达1 004 g/g;PAsp树脂的吸水性能随着干燥次数的增加而逐渐下降,干燥5次后树脂的吸水倍率仍能达到400 g/g,说明PAsp树脂具有较好的重复吸水性能。     

Tailorable polyelectrolyte protein complex based on poly(aspartic acid) and bovine serum albumin

Protein–polyelectrolyte complexes (PPC) are playing an important role in a variety of chemical and biological processes, such as protein separation, enzyme stabilization, and polymer drug delivery. The present investigation is focused on evaluation of the PPC formation between a synthetic polypeptide (poly(aspartic acid) – PAS) and a natural protein (bovine serum albumin – BSA). The PPC obtained from PAS and BSA in different ratio was investigated by corroboration of various techniques of characterization as: spectroscopy, microscopy, thermogravimetric analysis, dynamic light scattering (DLS), and zeta potential determination, measurements which were performed in static and/or dynamic conditions. The static contact angle of the sample films was also determined in order to evaluate the changes brought upon surface free energy of the prepared PPCs in interdependence with the complexes composition. The critical conditions for complex formation in BSA–polyelectrolyte systems were underlined. The phenomenon was better evidenced in case of a ratio of 1/1 wt between the two polymers, both in static and/or dynamic conditions.     

聚乳酸/聚乙烯醇纳米纤维的制备及结构

以二甲基亚砜为溶剂,制备不同配比的聚乳酸(PLLA)和聚乙烯醇(PVA)的混合溶液,静电纺丝制得PLLA/PVA纳米纤维。采用红外光谱仪、原子力显微镜等对PLLA/PVA纳米纤维结构与性能进行了表征。结果表明:PLLA/PVA纳米纤维中PVA上的羟基与PLLA上的羰基形成了氢键,PLLA与PVA之间存在一定的相互作用,但PLLA/PVA纳米纤维存在相分离现象;混合溶液的PLLA质量分数为11%,PVA质量分数为8%时可以得到较好的PLLA/PVA纳米纤维,但PVA质量分数为6%时出现液滴及珠丝,PVA质量分数为4%时,不能制得纳米纤维。     

聚天冬氨酸的合成与表征

以L-天冬氨酸为原料,热缩合成聚天冬氨酸酐,水解得到聚天冬氨酸。采用凝胶色谱法(GPC)测定了聚天冬氨酸的分子量,并用核磁共振(NMR)对其进行了表征。     

Controlling degradation and physical properties of chemical sand fixing agent‐poly(aspartic acid) by crosslinking density and composites

Poly(aspartic acid) (PASP) hydrogel crosslinked with 1,6‐ hexamethylene diamine was applied as sand fixing agent. The effect of crosslinking density of sand fixing agent on sand fixing property was studied. The relations between the degradation time and crosslinking density, sand fixing property, molecular weight, and mass loss were measured. It was found that the sand fixing property relied on the PASP crosslinking density and degradation time. The crust attained the maximal mechanical strength when the PASP crosslinking agent concentration was 0.0325 mol/L and the PASP hydrogel mass loss was 97.9% after 18 days. The composites added into PASP could increase mechanical property and prolong the degradation time when compared with the control. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

水体系中制备聚天冬氨酸高吸水性树脂的研究

以聚琥珀酰亚胺(PSI)为原料,采用无毒的γ-氨丙基三乙氧基硅烷(KH550)代替有毒的二胺类化合物作为交联剂,在水体系中合成了聚天冬氨酸高吸水性树脂,并探讨了交联剂用量、水解反应的pH值、交联温度和交联时间对高吸水性树脂吸水倍率的影响。采用红外光谱(FTIR)和扫描电镜(SEM)对高吸水性树脂进行表征。结果表明,KH550可以作为聚天冬氨酸高吸水性树脂的交联剂,且采用KH550为交联剂可以实现在水溶液中合成聚天冬氨酸。当KH550的摩尔分数是1.2%、水解反应的pH=10、交联温度为75℃、交联时间为2 h,所得产物在蒸馏水和生理盐水中的吸水倍率分别为455、115 g/g。FTIR分析表明,KH550已接枝到PSI链上,并且形成Si—O—Si结构。SEM结果显示树脂形成一种多孔的结构。     

Electrospun poly(D,L)‐lactide nonwoven mats for biomedical application: Surface area shrinkage and surface entrapment

Nanofibrous poly(D,L )‐lactide mats prepared by electrospinning are useful for numerous biomedical applications. However, it was observed that these mats tend to shrink under physiological conditions. In this research, a physical entrapment method to modify the polymer surface with poly(ethylene glycol) was developed to ensure dimensional stability and to increase the hydrophilicity of the surface of the mats. Nanofiber morphology was characterized by scanning electron microscopy. Surface element analysis was performed by high resolution X‐ray photoelectron spectroscopy. Water contact angles were determined to identify surface properties before and after surface entrapment. Canine fibroblasts were prepared and seeded onto the poly(D,L)‐lactide mats, followed by cell morphology study by SEM and cell viability tests by MTT assay, which confirmed the improvement of biocompatibility by surface modification. Taking the results into account, hydrophilic and area‐stable nanofibrous nonwoven mats were successfully produced, with potential applications as in vivo biomedical material. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reactive electrospinning of poly(vinyl alcohol) nanofibers

We aim to couple the electrospinning in‐line with solution chemistry to fabricate novel crosslinked polymer nanofibers. Poly(vinyl alcohol) (PVA) was used as a model polymer due to its high amount of hydroxyl groups. To obtain ideal parameters for electrospinning, pure PVA was explored primarily. To gain crosslinked fibers, PVA was first crosslinked partially with glutaraldehyde (GA) followed by transferring this precursor to a long hot tube which was used as reactor and then electrospun right before gelation. The preheating time and tube‐passing time were determined with viscometer and rheometer. The reactive as‐spun fibers could maintain their original morphology after water immersion due to their high crosslinking degree. The thermal stability and mechanical property of reactive as‐spun fibers were improved drastically compared with pure and GA vapor crosslinked PVA fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012