Novel sodium alginate/polyethyleneimine polyion complex membranes for pervaporation dehydration at the azeotropic composition of various alcohols

Dense polyion complex membranes of anionic sodium alginate (NaAlg) and cationic polyethyleneimine (PEI) were prepareand crosslinked with glutaraldehyde for dehydration of alcohol–water mixtures by pervaporation (PV). The membranes were characterized by ion‐exchange capacity measurement, Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy to investigate the extent of cross‐linking, intermolecular interactions, thermal stability, and surface and cross‐sectional morphologies, respectively. Wide‐angle X‐ray diffraction was used to investigate the crystallinity of the membranes. PV dehydration characteristics of the membranes were determined as a function of PEI content, crosslinking time as well as feed water composition. Transport parameters such as sorption, diffusion and permeability of water and alcohols through the membranes were determined. Among the four different membrane compositions, the polyion complex containing 40% PEI was found to yield optimum separation data in terms of membrane stability, selectivity and permeability. On the other hand, 10% PEI‐containing membrane gave the highest selectivity with the lowest flux at ambient temperature, but the membranes were not sufficiently stable. Copyright © 2007 Society of Chemical Industry     

Polymeric hollow fiber membranes for bioartificial organs and tissue engineering applications

Polymeric hollow fiber (HF) membranes are commercially available, i.e. microfiltration and ultrafiltration cartridges or reverse osmosis and gas separation modules, to be applied for separation purposes in industry, for instance to recover valuable raw materials or products, or for the treatment of end‐of‐pipe wastes to avoid environmental impacts, to regenerate or treat waters for reuse and for the separation of key components or clarification in food and beverage industries. They have also shown important benefits as hemodialyzers, hemodiafiltration or plasma purification devices in patients with liver or kidney damage. The good mass transport properties characterizing the polymeric HFs have opened new research areas of application in the biomedical field, such as the tissue engineering (TE) and the construction of bioartificial organs (BAO). In TE, the HFs act as scaffolds or supports and/or allow high permeance of nutrients and waste removal for cell proliferation and differentiation. In BAO, HFs are used for the fabrication of bio‐hybrid constructs that replace the damaged organs of the patient or can be used as in vitro models for therapeutic studies. This review presents the state‐of‐the‐art concerning preparation and application of HFs for TE and BAO and discusses the challenges and future perspectives of the HFs in both fields. © 2014 Society of Chemical Industry     

Characterization and preparation of polyion complex composite membranes for the separation of methyl tert‐butyl ether/methanol mixtures

A series of polyion complex (PIC) composite membranes composed of sodium alginate (SA) polyanion and chitosan polycation were prepared by varying the ratio of concentration. The interaction between SA and chitosan was investigated by FTIR, SEM, and X‐ray analysis and was related to mechanical properties and the swelling phenomenon. The overall PIC composite membranes showed the following results: the total thickness of the coating layer was thicker than that of pure SA composite, and increased with increasing the concentration of chitosan solution during PIC formation. This result was attributed to the diffusion of chitosan molecules from the liquid solution into the SA matrix, and the incorporation with SA molecules. For the PIC membranes prepared with different concentrations of polymer solution, their structural differences could not be detected from IR spectra but their morphological differences could be noticeably found from SEM. Furthermore, the amorphousness of PIC membranes and their elongation properties at break increased significantly as a function of polymer contents, whereas the tensile modulus decreased because of the physical transition effect. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 714–725, 2002     

Dynamically tunable cell culture platforms for tissue engineering and mechanobiology

Human tissues are sophisticated ensembles of many distinct cell types embedded in the complex, but well-defined, structures of the extracellular matrix (ECM). Dynamic biochemical, physicochemical, and mechano-structural changes in the ECM define and regulate tissue-specific cell behaviors. To recapitulate this complex environment in vitro, dynamic polymer-based biomaterials have emerged as powerful tools to probe and direct active changes in cell function. The rapid evolution of polymerization chemistries, structural modulation, and processing technologies, as well as the incorporation of stimuli-responsiveness, now permit synthetic microenvironments to capture much of the dynamic complexity of native tissue. These platforms are comprised not only of natural polymers chemically and molecularly similar to ECM, but those fully synthetic in origin. Here, we review recent in vitro efforts to mimic the dynamic microenvironment comprising native tissue ECM from the viewpoint of material design. We also discuss how these dynamic polymer-based biomaterials are being used in fundamental cell mechanobiology studies, as well as toward efforts in tissue engineering and regenerative medicine.     

Novel polyion complex with interpenetrating polymer network of poly(acrylic acid) and partially protected poly(vinylamine) using N-vinylacetamide and N-vinylformamide

Poly(vinylamine), the simplest polycation with primary amines, was applied to interpenetrating polymer networks (IPN) with poly(acrylic acid). N-Vinylformamide (NVF) was employed for amino-protected monomers to control electrostatic balance. pH-responsivities of IPNs varied, depending on the hydrolysis conditions and acrylic acid (AAc) concentration of the second network. Poly(N-vinylacetamide)-co-poly(N-vinylformamide) (4/6, mol/mol) was employed for the first network, subsequently hydrolyzed with 50% amide groups, and the second network was polymerized with 0.25 mol L⁻¹ AAc, extremely shrunken hydrogels with polyion complex were formed at pH 7, showing that the controlled amount of highly active primary amines are available in IPN.     

A novel method for the determination of cell infiltration into nanofiber scaffolds using image analysis for tissue engineering applications

One of the major themes in tissue engineering is scaffold fabrication. The porosity and pore size of scaffolds play a critical role in tissue engineering. Different methods are used to measure the porosity and pore size of scaffolds, although none can predict the cell infiltration for various cell sizes, shapes, and configurations. The aim of this study was to predict the cell infiltration of various cells with different sizes, shapes, and configurations through the use of image analysis. In this study, cell models were used to predict cell infiltration into nanofiber scaffolds. The results of this study showed that with increases in the cell size and the number of layers of nanofibers, the number of cells that could infiltrate the scaffolds decreased. In addition, the cell configuration had some effect on cell infiltration into the nanofiber scaffolds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel 3D scaffolds of chitosan-PLLA blends for tissue engineering applications: Preparation and characterization

This work addresses the preparation of 3D porous scaffolds of blends of chitosan and poly(l-lactic acid), CHT and PLLA, using supercritical fluid technology. Supercritical assisted phase-inversion was used to prepare scaffolds for tissue engineering purposes. The physicochemical and biological properties of chitosan make it an excellent material for the preparation of drug delivery systems and for the development of new biomedical applications in many fields from skin to bone or cartilage regeneration. On the other hand, PLLA is a synthetic biodegradable polymer widely used for biomedical applications. Supercritical assisted phase-inversion experiments were carried out in samples with different polymer ratios and different polymer solution concentrations. The effect of CHT:PLLA ratio and polymer concentration and on the morphology and topography of the scaffolds was assessed by SEM and Micro-CT. Infra-red spectroscopic imaging analysis of the scaffolds allowed a better understanding on the distribution of the two polymers within the matrix. This work demonstrates that supercritical fluid technology constitutes a new processing technology, clean and environmentally friendly for the preparation of scaffolds for tissue engineering using these materials.     

An in vitro evaluation of Genipin-crosslinked and Hypericum perforatum incorporated novel membranes for skin tissue engineering applications

Incorporating medicinal plant extracts in membranes have a great potential as scaffolds for tissue engineering applications or vehicles for delivering therapeutic agents. Herein, Hypericum perforatum oil (0.25, 0.50, % vol/vol) loaded membranes were developed with Polyvinyl alcohol and chitosan polymer, where Genipin works as a chemical crosslinker to obtain a wound dressing material with acceptable characterization properties. Chemical groups, surface morphology, water uptake capacity, water vapor permeability rate, hydrophilicity, and mechanical properties of membranes were thoroughly investigated. Increasing oil concentration had a significant effect on the water uptake, surface morphology. and water vapor permeability rate of the membranes. Cytocompatibility of the membrane was also investigated with mouse embryonic fibroblasts (MEF) by 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for direct and indirect cell culture studies. SEM was used to investigate the cell morphology on the membranes. The MTT assay findings prove that Genipin crosslinked H. perforatum oil loaded scaffolds are highly biocompatible and enhance the adhesion and proliferation of MEF cells. In addition to this, the genotoxicity test was performed to show DNA fragmentation. Results showed that the H. perforatum oil loaded polyvinyl alcohol-chitosan membrane presents suitable properties for potential skin tissue engineering applications.     

Fabrication of well-controlled porous foams of graphene oxide modified poly(propylene-carbonate) using supercritical carbon dioxide and its potential tissue engineering applications

Poly(propylene carbonate) is a new amorphous, biodegradable and biocompatible aliphatic polyester. It has a potentially wide range of applications, such as packing materials and biomedical materials. However, the low glass transition temperatures (T_g) and poor mechanical property have limited its applications. In this paper, poly(propylene-carbonate)/graphene oxide nanocomposites with a 10 °C increase in T_g and a 50 times increase in storage modulus at 30 °C were firstly fabricated, then the nanocomposites were foamed using supercritical CO₂ to widen their applications, particularly in the area of tissue engineering. It was demonstrated that the nanocomposite foams had good dimension stability and the final pore features were depended on supercritical CO₂ saturation conditions. In addition, cytotoxicity and in vitro cell culturing tests of selected foams showed that the fabricated porous materials were non-cytotoxic and able to support cellular adhesion within the 3D structure, suggesting that these are promising materials for tissue engineering applications.     

Modelling oxygen diffusion and cell growth in a porous, vascularising scaffold for soft tissue engineering applications

Soft tissue engineering presents significant challenges compared to other tissue engineering disciplines such as bone, cartilage or skin engineering. The very high cell density in most soft tissues, often combined with large implant dimensions, means that the supply of oxygen is a critical factor in the success or failure of a soft tissue scaffold. A model is presented for oxygen diffusion in a 15-60 mm diameter dome-shaped scaffold fed by a blood vessel loop at its base. This model incorporates simple models for vascular growth, cell migration and the effect of cell density on the effective oxygen diffusivity. The model shows that the dynamic, homogeneous cell seeding method often employed in small-scale applications is not applicable in the case of larger scale scaffolds such as these. Instead, we propose the implantation of a small biopsy of tissue close to a blood supply within the scaffold as a technique more likely to be successful.     

Development of polyion complex membranes for the separation of water–alcohol mixtures. I. Synthesis and physical properties of the polycations based on 1,3-di (4-pyridyl) propane

To prepare good polymeric materials for the preparation of the polyion complex membranes useful for water–alcohol separation, polycations were synthesized by the quaternization polymerization of 1,3-di(4-pyridyl)propane with dibromoalkanes or with 1,8-bis (p-toluenesulfonyl)octane. The polycations were characterized by FTIR spectroscopy, viscometry, DSC, and X-ray diffractometry. The polycations were in molecular weight ranges good enough to be used as membrane materials. The polycations were very hygroscopic and easily soluble in highly polar solvents such as water and these properties might be good for the membrane materials. The thermal properties and X-ray diffraction patterns of these polycations suggested that the polycations were semicrystalline and difficult to form crystals by melt crystallization. © 1994 John Wiley & Sons, Inc.     

Melt spun microporous fibers using poly(lactic acid) and sulfonated copolyester blends for tissue engineering applications

Microporous fibers can potentially increase diffusional properties of three‐dimensional nonwoven scaffolds used for tissue engineering applications. We have investigated the use of a water‐dispersible copolyester, sulfonated copolyester (SP), to create micropores in composite fibers containing a blend of SP and poly(lactic acid) (PLA) at 1, 3, 5, and 10% SP content. PLA and SP were blended at 175°C in a microcompounder followed by extrusion of composite fibers and removal of SP from composite fibers by using hydrodispersion to form micropores in the composite fibers. Differential scanning calorimetric studies on unhydrolysed composite fibers showed that SP was partially miscible in PLA. Fourier transform infrared mapping of composite fiber cross sections revealed that SP was randomly dispersed throughout the cross section where the degree of dispersion depended on the SP content. As revealed by the scanning electron micrographs, the size of the micropores was dependent on the SP content. Micropores on fiber cross sections were observed in fibers above 3% SP indicating that at least 3% SP content is needed to produce droplet morphology of SP in these fibers. These results show that SP can be successfully used in a blend with PLA to produce microporous fibers to fabricate three‐dimensional nonwoven scaffolds for tissue engineering applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of di‐butyryl‐chitin scaffolds by using salt leaching method for tissue engineering and their characteristics

Scaffolds are used as support material in treatment of damaged tissues such as cartilage and bone. With the help of scaffolds, damaged tissues can be cured in shorter period with less pain. Chitin is one of the most important scaffold materials curing the damaged tissues while providing a support for related part of the body during healing period. It is biocompatible and biodegradable; however it can not be solved by common solvents leading to the major drawback for this kind of applications. Therefore di‐butyril‐chitin (DBC), which is a chitin derivative and can be solved easily in solvents like acetone, ethanol, and methanol, is preferred for scaffold production instead of chitin. In this study, DBC scaffolds were produced for orthopedic applications and their structural and mechanical properties such as porosity, elasticity, compressibility, and strength were tested to confirm their suitability for such end‐uses. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Strategies for non‐invasive imaging of polymeric biomaterial in vascular tissue engineering and regenerative medicine using ultrasound and photoacoustic techniques

The ability of new polymeric materials to provide excellent biomechanical properties expanded their potential for biomedical applications enormously. The use of non‐invasive imaging modalities could provide crucial information to monitor the efficacy/effectiveness/efficiency of the new materials employed in ‘regenerative’ approaches, including scaffolds, hydrogels, self‐assembling materials and nanosized structures. The assessment of the morpho‐functional and metabolic changes of treated or implanted tissues, the visualization of sites of drug delivery and the real‐time check of the in vivo efficacy of therapeutics could be achieved by non‐invasive micro‐ and macro‐imaging techniques. The macro‐ and nano‐requirements of these new materials and their behaviour in vivo can be investigated using standard approaches such as computed tomography, MRI and ultrasound techniques and the emerging photoacoustic imaging. This paper presents recent advancements of ultrasonography and the novel photoacoustic technique to monitor the morpho‐functional parameters of synthetic polymeric scaffolds and conduits in experimental models. © 2016 Society of Chemical Industry     

Fabrication and characterisation of nanofibrous polyurethane scaffold incorporated with corn and neem oil using single stage electrospinning technique for bone tissue engineering applications

In bone tissue engineering, the design of scaffolds with ECM is still challenging now-a-days. The objective of the study to develop an electrospun scaffold based on polyurethane (PU) blended with corn oil and neem oil. The electrospun nanocomposites were characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), contact angle measurement, atomic force microscopy (AFM) and tensile strength. The assays activated prothrombin time (APTT), partial thromboplastin time (PT) and hemolysis assay were performed to determine the blood compatibility parameters of the electrospun PU and their blends of corn oil and neem oil. Further, the cytocompatibility studies were performed using HDF cells to evaluate their proliferation rates in the electrospun PU and their blends. The morphology of the electrospun PU blends showed that the addition of corn oil and corn/neem oil resulted in reduced fiber diameter of about 845?±?117.86?nm and 735?±?126.49 nm compared to control (890?±?116.911?nm). The FTIR confirmed the presence of corn oil and neem oil in PU matrix through hydrogen bond formation. The PU blended with corn oil showed hydrophobic (112°?±?1) while the PU together with corn/neem oil was observed to hydrophilic (64°?±?1.732) as indicated in the measurements of contact angle. The thermal behavior of prepared PU/corn oil and PU/corn/neem oil nanocomposites were enhanced and their surface roughness were decreased compared to control as revealed in the AFM analysis. The mechanical analysis indicated the enhanced tensile strength of the developed nanocomposites (PU/corn oil - 11.88 MPa and PU/corn/neem oil - 12. 96 MPa) than the pristine PU (7.12 MPa). Further, the blood compatibility assessments revealed that the developed nanocomposites possess enhanced anticoagulant nature compared to the polyurethane. Moreover, the developed nanocomposites was non-toxic to red blood cells (RBC) and human fibroblast cells (HDF) cells as shown in the hemolytic assay and cytocompatibility studies. Finally, this study concluded that the newly developed nanocomposites with better physio-chemical characteristics and biological properties enabled them as potential candidate for bone tissue engineering.     

Novel poly(l‐lactide‐co‐caprolactone)/gelatin porous scaffolds for use in articular cartilage tissue engineering: Comparison of electrospinning and wet spinning processing methods

Some novel polymeric fibrous nonwoven meshes have been processed from solution blends of poly(l ‐lactide‐co‐caprolactone), P(LL‐CL), and gelatin for use as biodegradable porous scaffolds in articular cartilage tissue engineering. P(LL‐CL) copolymers with LL:CL compositions ranging from 50:50 to 80:20 mol% were synthesized via the bulk ring‐opening copolymerization of L‐lactide (LL) and ε‐caprolactone (CL) using tin(II) octoate, Sn(Oct)₂, as the initiator. To make the hydrophobic P(LL‐CL) more hydrophilic for cell culture, it was solution blended with gelatin using trifluoroethanol as a common solvent to give P(LL‐CL):gelatin contents in the final scaffolds ranging from 70:30 to 95:5 wt%. Two different processing methods were used: electrospinning and wet spinning. Although electrospinning gave a more uniform mesh of nanosized fibers, the nonwoven mesh from wet spinning with its much larger pores and greater pliability was found to be more suitable for water absorption, cell infiltration and shape‐forming. Scanning electron micrographs of the scaffolds from the two techniques are compared. From the results obtained, the wet‐spun P(LL‐CL)50:50/gelatin 95:5 scaffold gave the best combination of properties. In particular, the 5% gelatin content resulted in a fivefold increase in the scaffold's equilibrium water uptake from about 10% to over 50% by weight. POLYM. ENG. SCI., 57:875–882, 2017. © 2016 Society of Plastics Engineers     

Chitosan–polyelectrolyte complexation for the preparation of gel beads and controlled release of anticancer drug. II. Effect of pH‐dependent ionic crosslinking or interpolymer complex using tripolyphosphate or polyphosphate as reagent

Chitosangel beads were prepared using an in‐liquid curing method by ionotropic crosslinking or interpolymer linkage with tripolyphosphate (TPP) or polyphosphate (PP). The ionic interaction of chitosan with TPP or PP is pH‐dependent due to the transition of “ladder‐loop” complex structures. Chitosan gel beads cured in a pH value lower than 6 of a TPP solution was a controlled homogeneous ionic‐crosslinking reaction, whereas chitosan gel beads cured in a lower pH PP solution was a nonhomogeneous interpolymer complex reaction due to the mass‐transfer resistance for the diffusion of macromolecular PP. According to the results of FTIR and EDS studies, it was suggested that significantly increasing the ionic‐crosslinking density or interpolymer linkage of a chitosan–TPP or chitosan–PP complex could be achieved by transferring the pH value of curing agent, TPP or PP, from basic to acidic. The swelling behavior of various chitosan beads in acid medium appeared to depend on the ionic‐crosslinking density or interpolymer linkage of the chitosan–TPP or chitosan–PP complex, which were deeply affected by the in‐liquid curing mechanism of the chitosan gel beads. By the transition of the in‐liquid curing mechanism, the swelling degree of chitosan–TPP or chitosan–PP beads was depressed and the disintegration of chitosan–TPP or chitosan–PP beads did not occur in strong acid. The drug‐release patterns of the modified chitosan gel beads in simulated intestinal and gastric juices were sustained for 20 h. These results indicate that the sustained release of anticancer drugs could be achieved due to the variation of the reaction mechanism of a chitosan–polyelectrolyte pH‐dependent ionic interaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1093–1107, 1999