Unexplored Green Solvent Systems for The Preparation of electrospun PLA and PCL functional Membranes: Overcoming Technological Lock-In.

Complications arising from tendon injury include tendon sheath infection and peritendinous adhesion, in which tendon adhesion often leads to serious motor dysfunction. In this work, the electrospun membranes of poly(L-lactide) (PLA) and poly(e-caprolactone) (PCL) with different degradation kinetics were used to investigate their efficacy for anti-adhesion toward Achilles tendon repair. Compared with the PCL membrane, the PLA sample showed a faster rate of degradation in 42 d, and all the degradation media (i.e., phosphate-buffered saline) maintained at a constant pH of around 7.4. Meanwhile, the superior biocompatibility of both the PLA and PCL membranes were proved by the in vitro cellular adhesion tests and in vivo histopathological assays. Simultaneously, the PLA membrane was more effective than the PCL sample in decreasing adhesion and promoting functional recovery. Furthermore, the experiment result was further confirmed by hematoxylin-eosin and Masson’s trichrome staining, and type I collagen immunohistochemical analysis. All results revealed that the model treated with the electrospun PLA membrane was obviously better with regard to both anti-adhesion and tendon repair than that in the PCL membrane group. Considering the results of degradation and adhesion prevention efficacy, the electrospun polyester membranes, especially the PLA one, would be applied with fascinating potential in clinical prevention of postoperative tendon adhesion.

For the first time, ultrafiltration (UF) green membranes were prepared through a sustainable route by using PLA as a biopolymer and dihydrolevoclucosenone, whose trade name is Cyrene™ (Cyr), dimethyl isosorbide (DMI), and ethyl lactate (EL) as biobased solvents. The influence of physical-chemical properties of the solvent on the final membrane morphology and performance was evaluated. The variation of polymer concentration in the casting solution, as well as the presence of Pluronic® (Plu) as a pore former agent, were assessed as well. The obtained results highlighted that the final morphology of a membrane was strictly connected with the interplaying of thermodynamic factors as well as kinetic ones, primarily dope solution viscosity. The pore size of the resulting PLA membranes ranged from 0.02 to 0.09 μm. Membrane thickness and porosity varied in the range of 0.090-0.133 mm of 75-87%, respectively, and DMI led to the most porous membranes. The addition of Plu to the casting solution showed a beneficial effect on the membrane contact angle, allowing the formation of hydrophilic membranes (contact angle < 90°), and promoted the increase of pore size as well as the reduction of membrane crystallinity. PLA membranes were tested for pure water permeability (10-390 L/m2 h bar).

Novel bio-polymer based membranes for CO2/CH4 separation

Green approaches to polysulfone based membrane preparation via dimethyl sulfoxide and eco-friendly natural additive gum Arabic

New green solvent system alkali (such as NaOH and LiOH)/urea which could rapidly dissolve cellulose could be potentially used to prepare high-performance regenerated cellulose materials with low cost. Pure regenerated cellulose materials have relatively low strength inherent effects. In this work, we choose TEMPO-oxide cellulose nanofiber (CNF) and graphene oxide (GO) as fillers to prepare isotropic regenerated cellulose membrane (RCM) with significantly enhanced mechanical properties. Dynamic mechanical analyzer (DMA) test shows that RCM with content of 5 wt% CNF has the maximum enhancement value of 32.5% improvement comparing with pure RCM. And RCM with 0.4 wt% GO has the maximum improvement of 17.9%. Mechanical properties decrease with further increasing filler contents. We employ transmission electron microscopy to confirm the structure of fillers in solution and scanning electron microscopy to observe the microstructures of these RCMs. The results are consistent with DMA tests. In addition, XRD results confirm that the crystal structure of RCMs is the same with RCMs without filler. Thermogravimetric analyses results indicate that RCMs keep great thermal stability below 300 °C. Transmittance (Tr) property is carried out by UV–Vis spectroscopy. Pure RCMs and CNF/RCMs keep high transparency at the wavelength of 800 nm. Transparency of RCMs with GO decrease quickly when the content of GO increases. In conclusion, the enhancement mechanism is proposed as the addition of fillers makes up the defects in RCMs. Furthermore, CNF illustrates large aspect ratio which is beneficial for stress transfer. As for GO, polar groups on surface provide strong interaction with the matrix. This is the first time that the enhancement effects of different fillers are systematically analyzed and compared for RCMs system. Our work could benefit the selection of appropriate fillers for such green solvent system and expand its range of applications.

A novel green solvent alternative for polymeric membrane preparation via nonsolvent-induced phase separation (NIPS)

This study investigated the process feasibility and stability of core/shell structured bicomponent ultrafine fibers of poly(vinyl pyrrolidone) (PVP) and poly(D,L‐lactide) (PLA) by coaxial electrospinning. The morphological structure of the core/shell ultrafine fibers was studied by means of scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Results suggested that PVP/PLA core/shell ultrafine fibers with drawbacks could be produced from 6 or 8% PVP solutions (inner) in the mixture of N,N‐dimethlformamide (DMF) and ethanol and a 22% PLA solution (outer) in DMF and acetone when the flow rates of inner and outer fluids were 0.05 and 0.1 mL/h, respectively. The tensile modulus and tensile strength of the core/shell PVP/PLA membrane were dramatically lower than those of the electrospun PLA membrane, and its water uptake was twice more than that of the PLA membrane. Membranes made from the biodegradable core/shell ultrafine fibers could be potentially used in loading bioactive molecules for tissue regeneration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 39–45, 2006

Electrospun nanofibrous membranes have gained considerable attention in bone tissue engineering due to their ability to mimic the extracellular matrix and provide a suitable environment for cell attachment and proliferation. This study investigates the fabrication, characterization, and biocompatibility of poly(L-lactic acid) (PLA)-based membranes enhanced with periclase (MgO) and gold nanoparticles (AuNPs). The membranes were fabricated using an optimized electrospinning process and subsequently characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), and contact angle measurements. Additionally, in vitro biodegradation studies in simulated body fluid (SBF) and cytocompatibility tests with osteoblast-like cells were conducted. The results demonstrated that the incorporation of MgO and AuNPs significantly influenced the structural and chemical properties of the membranes, improving their wettability and bioactivity. SEM imaging confirmed uniform fiber morphology with well-distributed nanoparticles. FT-IR spectroscopy indicated successful integration of bioactive components into the PLA matrix. Cytocompatibility assays showed that modified membranes promoted higher osteoblast adhesion and proliferation compared to pristine PLA membranes. Furthermore, biodegradation studies revealed a controlled degradation rate suitable for guided bone regeneration applications. These findings suggest that electrospun PLA membranes enriched with MgO and AuNPs present a promising biomaterial for GBR applications, offering improved bioactivity, mechanical stability, and biocompatibility.

&lt;p&gt;Membrane processes are employed in a wide variety of industrial applications such as separation of complex mixtures, hydrogen isolation, CO2 removal, wastewater treatment, etc. Their use allows energy savings on the production cost compared to other traditional separation technologies. Nevertheless, the preparation of membranes not always fulfills sustainability obligations, especially when considering the commonly employed solvents, i.e., N-methyl-2-pyrrolidone and N,N-dimethylformamide, to mention just a few. Dialkyl carbonates (DACs) are well-known green solvents and reagents that have been extensively investigated as safe alternatives to chlorine-based compounds and media such as alkyl halides, phosgene, and chlorinated solvents. Following our recent study on a scale-up procedure to non-commercially available or expensive DACs, herein we report for the first time the application of organic carbonates as green media for membrane preparation. Theoretical thermodynamic studies were first carried out to predict the solubilities in DACs of different polymers commonly employed for membranes preparation. As a result, the use of selected organic carbonates as media for polyvinylidene difluoride membrane preparation was investigated by nonsolvent-induced phase separation (NIPS) and a combination of vapor-induced phase separation (VIPS)-NIPS techniques. Membranes obtained with custom-made DACs displayed greater structural resistances and smaller pore sizes compared to the ones achieved using commercially available cyclic organic carbonates. Data collected showed that it was possible to achieve a wide variety of dense and porous membranes by using a single family of compounds, highlighting once again the great versatility of DACs as green solvents.&lt;/p&gt;

Electrospun polycaprolactone is widely used in the medical field. Formic acid/acetic acid (FA/AA) solvent system is one of the safest solvents used for the production of nano-range polycaprolactone (PCL) fibers, although it has a very low stability. In the present study, the stability of PCL in FA/AA system was enhanced by sodium hydrogen carbonate (NaHCO3) addition with three different concentrations (1, 5 and 10 wt%). The resultant electrospun fiber properties were compared to that treated by alkaline hydrolysis. The viscosity and conductivity of PCL solutions were measured before the electrospinning process. Moreover, the obtained electrospun PCL mats were characterized by SEM, FT-IR, XRD, contact angle measurements, degradability, swelling, and mechanical properties, as well as their ability to enhance the proliferation and adhesion of mesenchymal stem cells (MSCs). It was found that NaHCO not only enhanced the fiber properties, such as hydrophilicity, degradability and mechanical properties but also had a significant effect on the stability of polycaprolactone in FA/AA solvent system, as well as an enhanced MSCs proliferation and adhesion. Although hydrolyzed PCL showed high cell viability and adhesion, it showed much lower mechanical properties (0.7 MPa) compared to neat PCL (1.3 MPa) and PCL-NaHCO3 (5.1 MPa). In conclusion, the addition of NaHCO3 to PCL solution prior to the electrospinning process represents a novel and an effective approach to improve the physicochemical properties and biological behavior of electrospun PCL mats for tissue engineering application.

Black seed (Nigella sativa [NS]) is used in traditional medicine as an antibacterial agent. In this study, novel hybrid scaffolds were manufactured from poly(ɛ‐caprolactone[PCL])/ Poly(lactic acid [PLA]) with NS extract by double‐nozzle electrospinning for wound healing application. Optimal conditions were found using response surface methodology including feed rate 0.8 ml/hr, voltage 20 kV and PLA 8% /PCL 10% concentrations. The effect of NS extract on the properties of the scaffold was evaluated by scanning electron microscopy, contact angle, and mechanical test. The PLA‐PCL/NS 20% beadles, and smooth nanofibrous web was obtained as the optimum scaffold with an average diameter of 638 ± 69 nm and the contact angle of 44°. In addition, the biological properties of the scaffolds such as antibacterial against Staphylococcus aureus (gram‐positive) and Escherichia coli (gram‐negative) bacteria, MTT assay, extract release, and cell growth (human mesenchymal stem cells) were examined. Incorporation of NS extract into the nanofibers caused to enhance the biological properties, cell viability and cell proliferation without toxicity.

In the present study, PCL (polycaprolactone) nanofibres were produced by the electrospinning method. The use of PCL electrospun biopolymer in biomedical applications has attracted considerable interest due to its chemical resistance, biodegradability, biocompatibility, and non-toxic characteristics. However, the hydrophobic nature of PCL polymer restricts the useage of PCL nanofibres for the cell adhesion and absorption. A hydrophilic and biocompatible PCL electrospun mat with a low water contact angle is an attractive strategy for development in tissue engineering and wound dressing. In this study, we demonstrate a feasible and simple method to produce hydrophilic PCL nanofibres for possible application in wound dressing. Chloroform/ethanol (EtOH) and chloroform/dimethylformamide (DMF) mixtures were used as two different solvent systems. The impact of the polymeric solution concentration, applied voltage, and solvent mixtures on the fibre surface morphology and water contact angle was investigated. Consequently, bead structures were observed at low concentrations but disappeared with increases in the concentration. It was observed that the size of beads decreased and the diameter of fibres increased with increasing voltage. The wettability of the webs changed from hydrophobic to hydrophilic with changes of the polymer concentration. The contact angle of the nanofibre mats decreased in both solvent systems as the concentration increased. The results showed that the lowest contact angle was obtained in 24% wt. PCL+chloroform/EtOH solution and was 68°. The highest contact angle was obtained in 4% wt. PCL+chloroform/EtOH solution and was 112°. Using this method, the surface hydrophilicity of the PCL nanofibres improved easily without any surface treatment.

The possibility of replacing traditional toxic solvents normally employed during the preparation of polymeric membranes with greener alternatives represents a great challenge for safeguarding the human health and protecting the environment. In this work, an improved and pleasant-smelling version of dimethylsulfoxide (DMSO), i.e., DMSO EVOL™, was used as "greener solvent" for the preparation of polyethersulfone (PES) microfiltration (MF) membranes using a combination of non-solvent and vapor-induced (NIPS and VIPS, respectively) phase separation technique for the first time. The effect of two different additives polyvinylpyrrolidone (PVP) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronic®) together with polyethylene glycol (PEG) on membrane properties and performances has been also evaluated. The membranes were characterized in terms of morphology, mechanical resistance, pore size, and water permeability. The obtained results show that DMSO EVOL™ is able to replace 1-methyl-2-pyrrolidone (NMP), which is a more toxic solvent normally used for the preparation of PES membranes. Furthermore, it was possible to tune the produced membranes in the range of MF (0.1-0.6μm).

In the current study, a mixture of formic acid (FA), acetic acid (AA), and acetone was used, for the first time, as a ternary solvent system to dissolve poly(ɛ-caprolactone) (PCL). In addition, as a biomaterial reinforcement, various amounts of cellulose microfibrils (CMF) (1.5, 3, and 5 wt.%), extracted from rice husk, were added to PCL solution, and subsequently the prepared suspensions were individually electrospun. Adding acetone to FA/AA solvent system led to fabrication of uniform electrospun nanofibers with the average diameter of 178 ± 38 nm. Upon CMF incorporation, the mean electrospun fiber diameter was increased to 320 ± 132 nm at 5 wt.% CMF mostly due to the solution viscosity rise. In addition, scanning electron microscopy (SEM) confirmed wider diameter distribution in the presence of CMF. The electrospun fibers were also analyzed via wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) to study the supermolecular structure and thermal behavior of fibrous bionanocomposites, respectively. Both the characterizations positively affect the PCL crystallinity as a result of CMF incorporation. The DSC measurements showed the highest crystallinity (70.11%) at 1.5 wt.% CMF incorporation. The effect of CMF addition on the hydrophilicity of PCL was also investigated by contact angle measurement, where a decreasing trend in contact angle was observed upon CMF loading. Moreover, in vitro degradability of the bionanocomposite nonwoven mats was studied in PBS solution. The rate of degradation was enhanced in the presence of CMF. Moreover, tensile mechanical analysis was carried out and CMF inclusion had a reinforcing impact on electrospun PCL. The highest modulus (19.17 ± 0.8 MPa) and ultimate tensile strength (UTS) (4.45 ± 0.32 MPa) were achieved at 1.5 wt.% CMF addition to PCL.

AC electrospinning: impact of high voltage and solvent on the electrospinnability and productivity of polycaprolactone electrospun nanofibrous scaffolds