Polycaprolactone Solution Research Articles

Preparation and evaluation mechanical, chemical and thermal properties of hybrid jute and coir fibers reinforced bio-composites using poly-lactic acid and poly-caprolactone blends

Green composites using thermoplastics and thermosets got immense popularity long back when it newly introduced to the industry due to diminishing reliance on oil-based or gasoline materials, which causes numerous environmental problems. In this paper, bio-composites mechanical, chemical, thermal, and degradation properties of hybrid jute and coir fibers reinforced polylactic acid (PLA) investigated. Throughout the fabrication procedure of biocomposites, jute, and coir fibers characterized into three different categories raw, alkali-peroxide, and alkali-silane combined chemical treatments followed a design containing in a total of ten optimized samples. Jute and coir fibers were mixed with a solution of polycaprolactone (PCL) for better fiber-matrix adhesion prior to fabrication. The mechanical properties of alkali-silane treated reinforced fibers biocomposites improved compared to untreated fibers, which exhibited for fiber contents 40% an increase of respectively 32.8% by tensile strength 25.95% by tensile modulus, 24.58% by flexural strength, 23.64% by flexural modulus, and 26.08% by impact strength. Besides, moisture absorption, thickness swelling, thermal stability (TG), and surface chemistry analysis (FTIR) properties investigated, according to fiber-matrix contents ratio, hot-pressing time, temperature, and pressure to identify the effect of biocomposites due to chemical treatments. Moreover, the fiber surface effect of chemical treatments and interfacial adhesion morphologies observed using SEM. Eventually, alkali-silane combined optimized samples demonstrated the most desirable result in every aspect. In addition, a 90 days burial degradation performed to see the degradation flow of the biocomposites.

Tuning surface texture of electrospun polycaprolactone fibers: Effects of solvent systems and relative humidity

Abstract

Synthesis of electrospun nanofibrous structures with controlled optical and electrical properties

In this study, the optical and electrical influences of 2D graphene flakes in electrospun polycaprolactone (PCL) fibers were observed. Graphene nanoplatelets were added in different concentrations into the PCL solution, and then, using the electrospinning technique, fibers were built from that solution. Three samples were prepared with different graphene concentrations of 0% w/w, 0.5% w/w, and 2.0% w/w. From all three samples, fibers were prepared and tests were conducted for the identification of the properties of fibers. An optical spectroscopy test was performed to identify the optical behavior of the fibers. Scanning electron microscopy tests were conducted for the morphological characterization of the fibers. For the comparison of the electrical conductivity of the three samples, electrical tests were also conducted. In addition, Raman spectroscopy was conducted to characterize the graphene and PCL. This study shows that using graphene can change the properties of fibers, for example, as the graphene content increases, the fiber diameter also increases. Also, by varying the 2D graphene concentration, both electrical and optical properties can be tuned; this can be utilized in the synthesis of nanosensing surfaces and structures.

The Effects of Intrinsic Parameters on the Formation of Electrospun Polycaprolactone Fibre

Electrospinning process involved strong deformations of polymer fluid at rapid fibrous structure formation within mili seconds by several influence from the distinctive spinning parameters. This study has been conducted to achieve a desirable flow rate and optimum tip-to-collector needle distance for the electrospinning of polycaprolactone (PCL). For this aim, the morphological structure of fibre spun from 10 wt% PCL solution dissolved in dichloromethane (DCM) at 0.05 – 0.20 ml/min flow rate and 10 – 15 cm tip-to-collector needle range were characterized by FESEM. The results obtained show that average diameter of electrospun PCL fibres decreases with increasing flow rate at any needle to collector distance. In addition, the tip-to-collector needle range at 15 cm produced more beads-on-string fibres compared to 10 cm distance. The fibre thickness is reduced as both of the flow and the distance of needle tip-to-collector increased. All of the obtained electrospun PCL fibres are in non-uniform, long, porous beaded fibrous structure for all flow rate and needle distance tip-to-collector values.

Evaluation of polycaprolactone matrices for sustained intravaginal delivery of a natural macromolecular microbicide, lactoferrin

Polycaprolactone (PCL) matrices incorporating lactoferrin as a natural macromolecular microbicide, were prepared by rapidly cooling a suspension of lactoferrin particulates in PCL solution to induce crystallisation and hardening of the polymer. Thermal analysis revealed a 7% decrease in crystallinity of the PCL phase for 10% lactoferrin-loaded matrices compared with lactoferrin-free matrices and a 41% decrease in hardness of lactoferrin -loaded matrices, indicating a major influence of lactoferrin through inhibition of PCL crystal nucleation and growth. Exposure of the matrices to simulated vaginal fluid (SVF) at 37 °C resulted in rapid release of 13–14% of the lactoferrin content on day 1 and sustained delivery of the glycoprotein with high efficiency (90–95% of the content) over 14 days. SDS-PAGE analysis confirmed molecular weight preservation of the lactoferrin released from PCL matrices into SVF, indicating that it was not degraded during formulation and release. These findings recommend further investigations of PCL matrices as vaginal delivery systems for controlled release of macromolecular microbicides in the treatment and prevention of sexually transmitted infections.

Effect of pore architecture on the mesenchymal stem cell responses to graphene/polycaprolactone scaffolds prepared by solvent casting and robocasting

In the study graphene-containing porous, three dimensional polycaprolactone (PCL) scaffolds were prepared by solvent casting-salt leaching and robocasting methods for tissue engineering applications. Graphene nanopowders in the form of nanoflakes were incorporated into the polymer matrix at different concentrations namely 1, 3, 5 and 10 wt%. The dichloromethane was used as the solvent and sodium chloride crystals were utilized as the water-soluble porogen for the formation of an interconnected porous network (with non-oriented pores) inside the composite scaffolds in solvent casting-salt leaching method. On the other hand, acetone was utilized as solvent and PCL solutions were prepared at 20 wt% in robocasting method to construct scaffolds (with oriented pores) having a grid-like structure. The biological response of bone marrow mesenchymal stem cells seeded on these composite constructs having different architecture were tested using MTT method, live-dead cell viability assay and Alcian blue stanining. Cytotoxicity experiments revealed that mesenchymal stem cells did not show toxic response to composite robocast scaffolds. Cells proliferate and differentiate well on the surface of the robocast scaffolds compared to solvent-cast scaffolds under the same conditions. Results showed that scaffolds prepared in the study have potential to be used in cartilage tissue engineering in the presence of electric stimulation.

Preparation of electrospun nanofibrous polycaprolactone scaffolds using nontoxic ethylene carbonate and glacial acetic acid solvent system

ABSTRACTIn recent years, solution electrospinning has attracted the interest of researchers due to the possibility to design nanofibrous scaffolds with large surface area to volume ratios. Polycaprolactone (PCL), because of its biocompatibility and easy processability, has been widely used to develop electrospun structures for tissue engineering. However, the use of organic solvents and the poor PCL solution stability still hinder the development of the solution electrospinning process. The relatively benign glacial acetic acid (GAC) as a solvent of PCL was used to fabricate microfibrous fibers or beaded fibers. Thus, ethylene carbonate (EC) as a nontoxic assistant solvent was added to the PCL/GAC solution to successfully fabricate electrospun nanofibrous PCL scaffolds. The stability of the PCL/GAC/EC solution system was demonstrated as the viscosity, which showed no significant change during 48 h. The ultrafine PCL fiber diameter decreased as EC concentration was increased from 0 to 9 vol% and started to slightly increase when EC concentration increased beyond 9 vol%. MTT assay evidenced that MC3T3‐E1 cells on the nanofibrous PCL scaffolds exhibited a better enhancement on cell proliferation. In summary, EC was added in PCL/GAC to establish a stable and low toxic solution electrospinning system, which provides promising strategy in tissue engineering field. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48387.

Preparation of antibacterial PCL/PVP-AgNP Janus nanofibers by uniaxial electrospinning

The preparation of Janus nanofibers by electrospinning using a side-by-side needle is a well-known method. In this study, a new method was developed that utilized the phase separation phenomenon in a mixed solution of polycaprolactone (PCL) and polyvinylpyrrolidone (PVP) to prepare Janus nanocomposites via electrospinning. The morphology, hydrophilicity, and pore size distribution of the PCL/PVP Janus nanofibers were investigated. The results showed that the best effect was obtained when the PCL to PVP mass ratio was 1:1. In order to further verify that the method could successfully prepare nanofibers with the Janus structure, Ag nanoparticles (AgNP) were loaded on the nanofibers, which gave them an antibacterial property. The distribution of the AgNP on the nanofibers could be observed using transmission electron microscopy.

Enhancing the Stability, Hydrophilicity, Mechanical and Biological Properties of Electrospun Polycaprolactone in Formic Acid/Acetic Acid Solvent System

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.

A comparative study on pre- and post-production plasma treatments of PCL films and nanofibers for improved cell-material interactions

In this work, an atmospheric pressure plasma jet (APPJ) has been used to modify a 5% polycaprolactone (PCL) solution, after which the PCL solution was spin coated or electrospun to generate PCL films and nanofibers respectively. The APPJ treatment was found to have no effects on the chemical and physical properties of the PCL films, however, a strong influence on the morphology of electrospun PCL nanofibers could be observed. PCL nanofibers generated from the pristine PCL solutions contained multiple beads, while the PCL nanofibrous material generated from the APPJ-treated solutions consisted of nicely elongated, beadless PCL nanofibers. This enhanced electrospinnability was attributed to the strongly increased solution conductivity induced by the APPJ exposure. The APPJ treatment was also found to have minor effects on the chemical composition and the wettability of the nanofibers, which could be linked to the different surface morphology. All investigated pristine and APPJ-treated films and nanofibers unfortunately possessed poor cell-material interactions as a result of their high hydrophobicity. To cope with this issue, after spin coating and electrospinning, a second surface modification treatment making use of a dielectric barrier discharge (DBD) sustained in argon was also conducted. These treatments were found to considerably increase the wettability of PCL films and nanofibers without affecting their surface morphology. The enhanced wettability was caused by the incorporation of CO functional surface groups by the performed DBD treatments. The treatments were also found to positively affect cell growth on PCL films and nanofibers, with the best cellular performance obtained for the APPJ/DBD-treated PCL nanofibers. A combination of plasma treatments can thus play a significant role in the preparation of ideal electrospun PCL scaffolds for tissue engineering applications.

Encapsulated melatonin in polycaprolactone (PCL) microparticles as a promising graft material

Electrospraying assures many advantages with taking less time and costing less relatively to the other conventional particle production methods. In this research, we investigated the encapsulation of melatonin (MEL) hormone in polycaprolactone (PCL) microparticles by using electrospraying method. Morphology analysis of the produced particles completed with Scanning Electron Microscopy (SEM). SEM images demonstrated that micro-particles of 3 wt% PCL solution has the most suitable particle diameter size (2.3 ± 0.64 μm) for melatonin encapsulation. According to the characterization of the particles, electrospraying parameters like optimal collecting distance, the flow rate of the solution and voltage of the system detected as 8 cm, 0.5 ml/h, and 10 kV respectively. For determining the chemical bonds of scaffold Fourier-Transform Infrared Spectroscopy (FTIR) were used and FTIR results showed that melatonin successfully loaded into PCL micro-particles. Drug release kinetics of the melatonin loaded particles indicated that melatonin released with a burst at the beginning and release behavior became sustainable over a period of 8 h with the encapsulation efficiency of about 73%. In addition, both in-vitro and in-vivo studies of the graft materials also completed. Primary human osteoblasts (HOB) cells and female Sprague Dawley rats were used in in-vitro and in-vivo studies. Test results demonstrate cell population, and bone volume of the rats grafted with composites has remarkably increased, this caused remodelling in bone structure. Overall, these findings indicate that encapsulation of melatonin in the PCL particles with electrospray method is optimum for new synthetic graft material.

Simultaneous regeneration of calcium lactate and cellulose into PCL nanofiber for biomedical application

Synthetic polymers are easy to process and have excellent mechanical properties but low wettability and poor cell compatibility limit their applications in tissue scaffolding. In this study, a facile procedure was established to regenerate cellulose and calcium lactate (CaL) into a polycaprolactone (PCL) nanofibrous scaffold for tissue engineering applications. Briefly, varying amounts of lactic acid (LA) was mixed with the blend of PCL and cellulose acetate (CA) solutions and electrospun to fabricate an optimal composite PCL/CA/LA fibrous membrane. Later on, as-prepared membranes were treated with calcium hydroxide solution. This process simultaneously converted CA and LA contents into Cellulose and CaL, respectively. In situ regeneration of Cellulose and CaL into the composite fiber remarkably enhanced the biological and physicochemical properties of the composite fiber. This work provides a novel dual-channel strategy for simultaneous regeneration of biopolymer and bioactive molecule into the PCL nanofiber for regenerative medicine and tissue engineering applications.

Effects of GO and rGO incorporated nanofibrous scaffolds on the proliferation of Schwann cells

Graphene oxide (GO) and reduced graphene oxide (rGO) are two of the most representative graphene derivatives that can be employed to engineer bioactive and/or electroactive scaffolds for neural tissue engineering (NTE). However, a comparison with regard to their chemical structural impact on cytocompatibility has yet to be performed. In this study, GO was prepared using a modified Hummers’ method followed by thermal treatment to obtain the rGO. Thereafter, a stable jet electrospinning approach was used to electrospin a viscous mixed solution of polycaprolactone (PCL)/poly(ethylene oxide) (PEO) (mass ratio 4:1) containing a tiny amount of GO and rGO (1% w/w), for the generation of highly-aligned nanoscale fibers of PCL-PEO-GO and PCL-PEO-rGO, respectively. Structural characteristics and physicochemical properties of the GO and/or rGO incorporated PCL-PEO nanofibers were characterized by various analytical techniques including Raman, FTIR, SEM, water drop contact angle, cyclic voltammetry and tensile testing. Finally, biological study in vitro by culturing the fibrous scaffolds with murine Schwann cells for cytocompatibility evaluation demonstrated that comparatively PCL-PEO-GO scaffold could more favorably promote the proliferation of the Schwann cells. However, considering the noted higher electroconductivity, the fibrous PCL-PEO-rGO may be applied to induce stem cell differentiation towards neural lineage. This research could provide a guidance for judicious selection of the GO and rGO incorporated nanofibers to construct electroactive scaffolds for engineering functional neural tissues.

Facile fabrication of porous polymer fibers via cryogenic electrospinning system

Porous fibers had better performance in many application fields for their larger surface area or extra nano topography than smooth ones. However, high vapor pressure solvents or selective removal of one phase from fastidious blended fibers were mostly used to fabricate porous fibers in electrospinning process, which made the process unfriendly and inconveniently. Here, a facial process on fabrication of porous fibers was developed by integrating the principles of thermally induced phase separation with the self-made cryogenic electrospinning system (CES) which can provisional solidify the polymer jet on the freezing collector. For demonstration, the polymer solution of Polycaprolactone (PCL) with solvent of glacial acetic acid was chosen. The PCL porous fibers with diameter of 3.29 ± 0.42 μm were successfully prepared at the height of 90 mm and freezing temperature of −3.6 ± 0.3℃ on collector in room environment. Furthermore, the pores on the surface of fibers exhibited two types: pits and polygon concaves. The pits were induced by phase separation at freezing temperature and the polygon concaves were due to the interaction of residual solvent with ice crystals on surface of silicon wafer or metal collector recruited from the air moisture. Generally, this process was suitable to polymer solutions with solvents of low vapor pressure but high freezing point.

Electrospinning 3D Nanofiber Structure of Polycaprolactone Incorporated with Silver Nanoparticles

This study presents a one-station 3D fabrication technique of nanofibrous scaffold for tissue engineering. A divergence static electric field was introduced in an electrospinning system to induce a self-assembly of aligned polycaprolactone (PCL) nanofibers into a tunable 3D architecture with thickness ranging from 2 to 12 mm. Silver nanoparticles were incorporated into the PCL solution to alter the electrical conductivity. Human fibroblast cells were cultured on the pure PCL nanofiber scaffolds in vitro for 7 days. It was found that the occurrence of nanofiber bridging phenomenon depended on the solution viscosity. The minimum viscosity to form a 3D nanofiber structure was higher than that to form a 2D nanofiber mat. The homogeneity of nanofiber distribution within the 3D space was positively correlated with the electrical conductivity and the weight of the nanofibers. In the cell culture test, fibroblasts proliferated on the scaffold and organized as an aligned matrix which mimicked the microstructure of native musculoskeletal tissues.

Electrospun Produced 3D Matrices for Covering of Vascular Stents: Paclitaxel Release Depending on Fiber Structure and Composition of the External Environment.

Paclitaxel is a natural, highly lipophilic anti proliferative drug widely used in medicine. We have studied the release of tritium-labeled paclitaxel (3H-PTX) from matrices destined for the coating of vascular stents and produced by the electrospinning method from the solutions of polycaprolactone (PCL) with paclitaxel (PTX) in hexafluoisopropanol (HFIP) and/or solutions of PCL with PTX and human serum albumin (HSA) in HFIP or HIFP-dimethyl sulphoxide (DMSO) blend. The release of PTX has been shown to depend on the composition of electrospinning solution, as well as the surrounding medium, particularly the concentration of free PTX and PTX-binding biomolecules present in human serum. It was shown that 3D matrices can completely release PTX without weight loss. Two-phase PTX release from optimized 3D matrices was obtained: ~27% of PTX was released in the first day, another 8% were released over the next 26 days. Wherein ~2.8%, ~2.3%, and ~0.25% of PTX was released on day 3, 9, and 27, respectively. Considering PTX toxicity, the rate of its diffusion through the arterial wall, and the data obtained the minimum cytostatic dose of the drug in the arterial wall will be maintained for at least three months.

Fabrication of a thick three-dimensional scaffold with an open cellular-like structure using airbrushing and thermal cross-linking of molded short nanofibers

Nanoscale fibers mimicking the extracellular matrix of natural tissue can be produced by conventional electrospinning, but this approach results in two-dimensional thin dense fibrous mats which can hinder effective cell infiltration. The aim of the present study was to design a thick, three-dimensional (3D) cylindrical scaffold with an open pore structure assembled from short polycaprolactone (PCL) fibers using a facile airbrushing approach. In addition, magnesium particles were incorporated into the PCL solution to both enhance the mechanical properties of the scaffold and stimulate cellular activity following cell seeding. Separated short composite airbrushed fibers were assembled into a 3D cylindrical structure by cold-press molding and thermal cross-linking. The microstructure, chemical composition, porosity and thermal properties were subsequently investigated, along with changes in mechanical performance following immersion in PBS for 60 d. The results showed that the assembled 3D fibrous 10 mm thick cylindrical matrix had an interconnected fibrous network structure with 31.5%–60% porosity. Encapsulation of the Mg particles into the 3D assembled fibrous scaffold enhanced the mechanical properties of the plain PCL scaffolds. The results also demonstrated controlled release of Mg ions into the PBS media for up to 60 d, as evaluated by changes in Mg ion concentration and pH of the media. In addition, the 3D fibrous assembled matrix was shown to support human osteoblast-like cell adhesion, proliferation and penetration. The results suggest that this novel fabrication method of biodegradable thick 3D scaffolds with an open pore structure is promising for the production of a new generation of 3D scaffolds for tissue regeneration applications.

Drug release and biodegradability of electrospun cellulose nanocrystal reinforced polycaprolactone

In this paper, high molecular weight cellulose was used as the starting material for the synthesis of cellulose nanocrystal (CNC). Different analysis techniques such as FTIR, XRD, TGA, DLS, and AFM were used to characterize CNC synthesis. The synthesized CNC was incorporated in polycaprolactone solution and nanofibers were prepared under different conditions. Production conditions were optimized based on the diameter of nanofibers using response surface methodology (RSM). Based on our results, the optimal condition is electrospinning of 16% PCL polymer solution at 17 kV and a 0.9 ml/h feed rate, which yields nanofibers with a diameter of 233 nm. The effects of CNC content on morphological, mechanical and thermal properties were investigated. Results also showed that CNC incorporation in PCL nanofibers enhances biodegradability. SEM, DSC, tensile, and biodegradability results showed that the nanofibers prepared from PCL solution containing 1% CNC have optimal mechanical and degradation behaviors. We also studied and modeled release of tetracycline from nanofiber mats, based on the assumption of rate limiting diffusion from the nanofibers, with a fraction of release delayed by drug sequestration. Results showed that the final drug release is decreased in CNC-incorporated nanofibers.

Biodegradable Anisotropic Microparticles for Stepwise Cell Adhesion and Preparation of Janus Cell Microparticles.

The biomimetic anisotropic particles have different physicochemical properties on the opposite two sides, enabling diverse applications in emulsion, photonic display, and diagnosis. However, the traditional anisotropic particles have a very small size, ranging from submicrons to a few microns. The design and fabrication of anisotropic macron-sized particles with new structures and properties is still challenging. In this study, anisotropic polycaprolactone (PCL) microparticles well separated with each other were prepared by crystallization from the dilute PCL solution in a porous 3D gelatin template. They had fuzzy and smooth surfaces on each side, and a size as large as 70 μm. The fuzzy surface of the particle adsorbed significantly larger amount of proteins, and was more cell-attractive regardless of the cell types. The particles showed stronger affinity toward fibroblasts over hepatocytes, which paved a new way for cell isolation merely based on the surface morphology. After a successive seeding process, Janus cell microparticles with fibroblasts and endothelial cells (ECs) on each side were designed and obtained by making use of the anisotropic surface morphology, which showed significant difference in EC functions in terms of prostacyclin (PGl2) secretion, demonstrating the unique and appealing functions of this type of anisotropic microspheres.

Electrospun poly(ε-caprolactone) nanofiber shish kebabs mimic mineralized bony surface features.

Electrospinning of nanofiber is of growing interest especially in bone tissue engineering because of its similar fibrous properties to the extracellular matrix. To this end, we have fabricated polycaprolactone (PCL) nanofiber shish kebab (NFSK) templates. The novelty of this work is the ability to control the mineral orientation and spatial location on the nanofiber, mimicking natural collagen fibers. However, NFSK templates have properties that need to be investigated in terms of cellular response including fiber alignment and crystallization. In this study, MC3T3 E1 preosteoblast cells were seeded onto the templates to determine the effect of both fiber orientation and kebab size on the cell metabolic activity. PCL was electrospun to form aligned and randomly oriented nanofibers, which were then crystallized in a PCL solution in pentyl acetate for 15 and 60 min, resulting in the formation of homopolymer PCL NFSK templates. We evaluated the cell proliferation and alkaline phosphatase activity of MC3T3 E1 cells after 3, 7, and 14 days in coculture. Aligned nanofiber and polymer crystallization both significantly increased the cell proliferation and alkaline phosphatase activity at each time point. The aligned nanofibers and polymer crystallization resulted in the highest metabolic activities of the cells compared to the randomly oriented fibers and noncrystallized controls. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1141-1149, 2019.