Polycaprolactone Films Research Articles

Analysis of early cellular responses of anterior cruciate ligament fibroblasts seeded on different molecular weight polycaprolactone films functionalized by a bioactive poly(sodium styrene sulfonate) polymer.

With the growing number of anterior cruciate ligament (ACL) ruptures and the increased interest for regenerative medicine procedures, many studies are now concentrated on developing bioactive and biodegradable synthetic ligaments. For this application, the choice of raw materials with appropriate physicochemical characteristics and long-term degradation features is essential. Polycaprolactone (PCL) has the advantage of slow degradation that depends on its molecular weight. This study evaluates two PCL materials: a technical grade (PC60: 60 kDa) versus a medical grade (PC12: 80 kDa), both before and after functionalization with poly(sodium styrene sulfonate) (pNaSS). After determining the grafting process had little to no effect on the PCL physicochemical properties, sheep ACL fibroblast responses were investigated. The PC12 films induced a significantly lower expression of the tumor necrosis factor alpha inflammatory gene compared to the PC60 films. Both film types induced an overproduction of fibroblast growth factor-2 and transforming growth factor beta compared to the controls on day 5 and demonstrated collagen gene expression profiles similar to the controls on day 7. Upon protein adsorption, pNaSS grafting caused a rapid cell adhesion in the first 30 min and an increased adhesion strength (1.5-fold higher). Moreover, after 7 days, an increase in cell density and actin network development were noted on the grafted films.

Dependence of mechanofluorochromic property at room temperature on alkyl chain structure for β-diketone boron complex and its polymer blend film

A series of β-diketonate boron complexes (BF2-TPEn, n = 1, 2, 3, 4 and 5) with different alkyl chain lengths and tetraphenylethylene (TPE) group, were synthesized to investigate the effect of alkyl chain structure on their fluorescence properties. The results showed that all the as-prepared BF2-TPEn complexes emit fluorescence, but only the emission wavelength of BF2-TPEn (n = 1, 3 and 5) is changed from yellow to orange after grinding, which revealed that the mechanofluorochromic (MFC) property of complexes relies on the parity of the carbon atoms at the end of the molecules. Notably, it is also found that the fluorescence emission of the ground samples of BF2-TPE1 and BF2-TPE5 could recover spontaneously at room temperature without the need for solvent fumigation or other stimulates. This reversible MFC property at room temperature is distinctly different from the other MFC materials reported in previous literature. Additionally, the blend films of polycaprolactone (PCL) and complexes were prepared to investigate the effect of different alkyl chain length on fluorescence emission of BF2-TPEn existing in polymer. It is found that only the PCL film containing BF2-TPE5 showed MFC property at room temperature, which is expected to receive widespread applications in the field of optical devices and mechanical sensors. This work demonstrates that alkyl chain structure can tune the MFC properties of β-diketonate boron complexes, which provides good design ideas for the development of novel MFC materials.

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.

Temporary Wettability Tuning of PCL/PDMS Micro Pattern Using the Plasma Treatments.

Surface wettability plays an important role in determining the function of a wound dressing. Dressings with hydrophobic surfaces are suitable for bacterial adsorption, however, a hydrophilic surface is needed to improve cell attachment for most anchorage-dependent cell types. Furthermore, the hydrophobicity/hydrophilicity of the surface can be used to direct cellular processes such as cell initial attachment, adhesion, and migration during wound healing. Thus, a surface with an ability to switch their surface wettability improves the practicality of the dressing. In this study, we propose a temporary surface wettability tuning for surface patterning utilizing plasma treatment. Polycaprolactone (PCL) and polydimethylsiloxane (PDMS) surfaces were treated with tetrafluoromethane (CF4), sulphur hexafluoride (SF6), and oxygen (O2) plasma, and the effects on the surface wettability, roughness, and chemical composition were investigated. Based on the contact angle measurement, CF4 plasma altered surface wettability of PCL and PDMS films to hydrophobic and hydrophilic, respectively. After CF4 treatment, better attachment of primary mouse embryonic fibroblast cell (3T3) was observed on the treated PDMS surface. Embedding PCL into PDMS generated a hydrophobic-hydrophilic pattern mixture surface, which offers great potential in the tissue engineering field such as cell patterning and guidance.

Local application of MDL28170-loaded PCL film improves functional recovery by preserving survival of motor neurons after traumatic spinal cord injury

Neuronal death and organization degeneration can happen inordinately after spinal cord injury (SCI), which lead to nerve dysfunction. We aimed to determine whether local application of a cell permeable calpain I inhibitor (MDL28170) can promote SCI recovery by increasing neuronal cell viability. MDL28170-loaded polycaprolactone (PCL) film was fabricated. Scanning electron microscopy showed the surface of PCL film was smooth with holes (diameter at μM level). The PCL film was non-toxic, biological compatibility, and had good neuron adhension and slow release characteristic. MDL28170 increased VSC4.1 motor neurons’ viability under tunicamycin (an endoplasmic reticulum stress) induced injury. In a traumatic SCI rat model, MDL28170-loaded PCL film reduced the area of lesion cavity, and promoted recovery of locomotor behavior. Moreover, the expression of GAP-43 was upregulated after MDL28170-loaded PCL film treatment. Thus, our findings demonstrated that localized delivery of MDL28170 could promote SCI recovery by inhibiting endoplasmic reticulum stress, preserving survival of the motor neurons, which may point out a promising therapeutic target for treating SCI patient.

Nanoroughness, Surface Chemistry, and Drug Delivery Control by Atmospheric Plasma Jet on Implantable Devices.

Implantable devices need specific tailored surface morphologies and chemistries to interact with the living systems or to actively induce a biological response also by the release of drugs or proteins. These customized requirements foster technologies that can be implemented in additive manufacturing systems. Here, we present a novel approach based on spraying processes that allow to control separately topographic features in the submicron range (∼60 nm to 2 μm), ammine or carboxylic chemistry, and fluorophore release even on temperature-sensitive biodegradable polymers such as polycaprolactone (PCL). We developed a two-steps process with a first deposition of 220 nm silica and poly(lactic- co-glycolide) (PLGA) fluorescent nanoparticles by aerosol followed by the deposition of a fixing layer by an atmospheric pressure plasma jet (APPJ). The nanoparticles can be used to create the nanoroughness and to include active molecule release, while the capping layer ensures stability and the chemical functionalities. The process is enabled by a novel APPJ which allows deposition rates of 10-20 nm·s-1 at temperatures lower than 50 °C using argon as the process gas. This approach was assessed on titanium alloys for dental implants and on PCL films. The surfaces were characterized by Fourier transform infrared, atomic force microscopy, and scanning electron microscopy (SEM). Titanium alloys were tested with the preosteoblast murine cells line, while the PCL film was tested with fibroblasts. Cell behavior was evaluated by viability and adhesion assays, protein adsorption, cell proliferation, focal adhesion formation, and SEM. The release of a fluorophore molecule was assessed in the cell growing media, simulating a drug release. Osteoblast adhesion on the plasma-treated materials increased by 20% with respect to commercial titanium alloy implants. Fibroblast adhesion increased by a 100% compared to smooth PCL substrates. The release of the fluorophore by the dissolution of the PLGA nanoparticles was verified, and the integrity of the encapsulated drug model was confirmed.

Evaluation and characterization of waterborne biodegradable polyurethane films for the prevention of tendon postoperative adhesion.

BackgroundTendon adhesion is a serious problem and it affects tendon gliding and joint motion. Although recent studies have yielded promising results in developing anti-adhesion materials, there are still many problems. Polycaprolactone (PCL)-based polyurethane (PU) has good mechanical properties and biocompatibility, and it has a potential in anti-adhesion applications.Materials and methodsIn this study, a series of waterborne biodegradable polyurethane (WBPU) films with different ratios of ionic groups were synthesized. In order to select an effective anti-adhesion film, the WBPU films were cast and characterized for physicochemical properties and biocompatibility.ResultsAll WBPU films were non-cytotoxic in the cell viability test and had suitable physicochemical and mechanical properties based on the measurement of zeta potential, water contact angle, mechanical properties, water absorption, thickness change, and gelatin test. To evaluate the anti-adhesion effect, severely injured tendons of rabbits were sutured with the modified Kessler core suture technique and WBPU films were then wrapped around the tendon. Implantation in rabbits showed that the WBPU film had better anti-adhesion effect than PCL films and the untreated control, and demonstrated no significant difference in the anti-adhesion performance from the commercial product Seprafilm based on gross evaluation, histological analysis, and biomechanical assessment.ConclusionCompared to Seprafilm and PCL applied in the tendon anti-adhesion, WBPU had better mechanical properties, low inflammatory reaction, and a proper degradation interval.

Bioactive Tape With BMP-2 Binding Peptides Captures Endogenous Growth Factors and Accelerates Healing After Anterior Cruciate Ligament Reconstruction

Background: The anterior cruciate ligament (ACL) has poor regenerative capacity, and an injury leads to loss of function, limiting quality of life and increasing the incidence of osteoarthritis. Surgical interventions can stabilize the joint and improve functional recovery. The delivery of growth factors (GFs) enhances the healing process; however, this is complex in its regulation, is high in costs, has side effects, and can only be accomplished with supraphysiological concentrations and thus is currently not clinically feasible. However, the immobilization of a patient’s endogenous GFs in biomaterials can overcome these problems. Purpose: To develop a method to capture endogenous bone morphogenetic protein–2 (BMP-2) and ultimately show enhanced ACL healing in vivo using this novel methodology. Study Design: Controlled laboratory study. Methods: BMP-2 binding peptides were synthetized, purified, and immobilized on polycaprolactone (PCL) films. The affinity between the peptide and human BMP-2 (hBMP-2) was confirmed with immunofluorescence and enzyme-linked immunosorbent assay. The C2C12 Luc reporter cell line was used to confirm the bioactivity of immobilized BMP-2. For in vivo experiments, the same functionalization technology was applied to the commercially available Polytape, and the functionalized tape was sutured together with the graft used for ACL reconstruction in rats. Each animal underwent reconstruction with either native Polytape (n = 3) or Polytape with BMP-2 binding peptides (n = 3). At 2 and 6 weeks after surgery, the graft was assessed by histology and micro–computed tomography. Results: The covalent immobilization of the peptide in PCL was successful, allowing the peptide to capture hBMP-2, which remained bioactive and led to the osteogenic differentiation of C2C12. In vivo experiments confirmed the potential of the Polytape functionalized with the BMP-2 binding peptide to capture endogenous BMP-2, leading to enhanced bone formation inside the femoral and tibial tunnels and ultimately improving the graft’s quality. Conclusion: The incorporation of BMP-2 binding peptides into materials used for ACL reconstruction can capture endogenous hBMP-2, which enhances the healing process inside the bone tunnels. Clinical Relevance: These results demonstrate the potential of using synthetic peptides to endow biomaterials with novel biological functions, namely to capture and immobilize endogenous GFs.

ANÁLISIS DE LAS PROPIEDADES FÍSICAS Y ESTRUCTURALES DE LAS PELÍCULAS DE QUITOSANO-POLICAPROLACTONA ADICIONADAS CON EXTRACTO DE HOJA DE Moringa oleifera

Physico-structural properties of biodegradable films of chitosan and polycaprolactone (PCL) added with Moringa oleifera leaf extract were determined. The films were analyzed for thickness, transparency, solubility, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The transparency was increased as the PCL concentration increased and there was no difference in solubility for any of the formulations evaluated. On the other hand, FTIR spectra revealed an increase in hydroxyl groups, amides and carbonyls bands as the concentration of PCL and M. oleifera extract increased. XRD diffractograms showed a good miscibility between chitosan and PCL using concentrated acetic acid as the solvent. The properties of PCL to modify the physico-structural characteristics of chitosan are maintained.

Biodegradation of PCL and PVC: Chaetomium globosum (ATCC 16021) activity.

The increasing use of plastics in human activities has resulted in an enormous amount of residues which became a matter of great environmental concern. Scientific studies on the microbial degradation of natural and synthetic molecules show the potential of fungal application on cleaning technologies. The biodegradation of PCL (polycaprolactone) and PVC (polyvinyl chloride) films by Aspergillus brasiliensis (ATCC 9642), Penicillium funiculosum (ATCC 11797), Chaetomium globosum (ATCC 16021), Trichoderma virens (ATCC 9645), and Paecilomyces variotii (ATCC 16023) was studied. According to ISO 846-1978-"Testing of Plastics - Influence of fungi and bacteria", samples of the studied polymers were inoculated with a mix suspension of 106 fungal inoculum and maintained in moisture glass chambers in a bacteriological incubator at 28°C for 28days. The samples were analyzed by means of morphological and color changes, mass loss, optical microscopy (OM), and scanning electron microscopy (SEM) after 28days of culturing. After the incubation period, visual observations of the PCL films showed many micropores and cracks, pigmentation, surface erosion and hyphal adhesion on the sample surfaces, and a mass loss of up to 75%. On the contrary, there was no evidence of PVC biodegradation, such as changes in color and significant mass loss. Chaetomium globosum ATCC 16021 was a pioneer in the colonization and attack of PCL, resulting in significant mass losses. Although PVC was less attacked by the ascomycete, the polymer supported the adhesion and growth of its fertile structures (perithecia), suggesting the fungal potential to degrade both plastics.

UV-A activated TiO2 embedded biodegradable polymer film for antimicrobial food packaging application

TiO2 nanoparticles embedded polymer films were fabricated by solution casting method using three biodegradable polymers (cellulose acetate (CA), polycaprolactone (PCL) and polylactic acid (PLA)). Optical and physical properties of the films were assessed by measuring the thickness, color, UV–vis absorption spectra and UV-A transmission. Photodegradation of methylene blue was used to evaluate photocatalytic activity of different TiO2 embedded polymer films. Photocatalytic bactericidal property of the films was evaluated by inactivation of Escherichia. coli O157:H7 under UV-A light illumination at a light intensity of 1.30 ± 0.15 mW/cm2 for 2 h. CA film incorporated with 5 wt% TiO2 NPs had highest bactericidal activity and achieved 1.69 log CFU/ml reduction. Whereas, TiO2 embedded PCL and PLA composite films did not show significant bactericidal property. TiO2 embedded CA film has the potential to be used as antimicrobial food packaging.

Crystallization kinetics of PCL and PCL–glass composites for additive manufacturing

The non-isothermal crystallization kinetics of polycaprolactone (PCL) and PCL–glass composites, used in fused filament fabrication (FFF), was investigated. Films of PCL and PCL reinforced with powders of a bioactive glass, from the CaO·P2O5·MgO·SiO2 system, were prepared by solvent casting process. Crystal structure of the samples was examined by X-ray diffraction (XRD), and thermal properties were assessed by differential scanning calorimetry (DSC), at different cooling rates (5, 10, 15 and 20 °C min−1). The DSC curves of non-isothermal crystallization showed a significant dependence of crystallinity (Xc) on the cooling rate. The relevant crystallization kinetic parameters were determined from DSC traces applying a combination of Avrami and Ozawa methods (Mo’s method), Jeziorny method and Friedman method. It was observed that the presence of inorganic particles within the polymeric matrix clearly influenced the composite crystallization. The addition of glass particles allowed a decrease in Xc and accelerated the PCL crystallization rate. The slower cooling rates tested proved to be suitable for the biofabrication of PCL–glass composites by FFF techniques.

Development and properties of duplex MgF2/PCL coatings on biodegradable magnesium alloy for biomedical applications.

The present work addresses the performance of polycaprolactone (PCL) coating on fluoride treated (MgF2) biodegradable ZK60 magnesium alloy (Mg) for biomedical application. MgF2 conversion layer was first produced by immersing Mg alloy substrate in hydrofluoric acid solution. The outer PCL coating was then prepared using dip coating technique. Morphology, elements profile, phase structure, roughness, mechanical properties, invitro corrosion, and biocompatibility of duplex MgF2/PCL coating were then characterized and compared to those of fluoride coated and uncoated Mg samples. The invivo degradation behavior and biocompatibility of duplex MgF2/PCL coating with respect to ZK60 Mg alloy were also studied using rabbit model for 2 weeks. SEM and TEM analysis showed that the duplex coating was uniform and comprised of porous PCL film (~3.3 μm) as upper layer with compact MgF2 (~2.2 μm) as inner layer. No significant change in microhardness was found on duplex coating compared with uncoated ZK60 Mg alloy. The duplex coating showed improved invitro corrosion resistance than single layered MgF2 or uncoated alloy samples. The duplex coating also resulted in better cell viability, cell adhesion, and cell proliferation compared to fluoride coated or uncoated alloy. Preliminary invivo studies indicated that duplex MgF2/PCL coating reduced the degradation rate of ZK60 Mg alloy and exhibited good biocompatibility. These results suggested that duplex MgF2/PCL coating on magnesium alloy might have great potential for orthopedic applications.

Structure, nanomechanics, and dynamics of dispersed surfactant‐free clay nanocomposite films

The current work presents a new approach to achieve high quality dispersion of surfactant‐free nanoclay tactoid particles in sub‐micron thin films despite the absence of organic modifier. Natural Montmorillonite particles, Cloisite, were dispersed in thin films of polycaprolactone (PCL) through a flow coating technique assisted by ultra‐sonication. Wide‐angle X‐ray scattering (WAXS), grazing‐incidence wide‐angle X‐ray scattering (GI‐WAXS), and transmission electron microscopy (TEM) were used to confirm the level of natural clay dispersion down to the level of tactoids (sub‐micron scale stacks of clay sheets). These characterization techniques were carried out in conjunction with an analysis of nanomechanical properties via strain‐induced buckling instability for modulus measurements (SIEBIMM), a high‐throughput technique to characterize thin film mechanical properties. The buckling patterns indicate that the natural clay tactoids separate buckling‐enhancing (high‐modulus) crystalline regions and interconnect buckling‐suppressing amorphous (low‐modulus) regions. Due to the tactoid length scale, the glass transition behavior of the composites as characterized by broadband dielectric relaxation spectroscopy was unmodified by the clay. Likewise, the glass transition temperature, Tg, and fragility (slope of relaxation time behavior approaching Tg), remain unaffected, indicating that these dispersed tactoids do not induce pronounced confinement effects on dynamics. POLYM. ENG. SCI., 58:1285–1295, 2018. © 2018 Society of Plastics Engineers

Research on the Preparation of Polycaprolactone Porous Films with Decoration of Protein Arrays via the Emulsion‐Based Breath Figure Method

AbstractA facile method to fabricate honeycomb‐patterned biocompatible polycaprolactone (PCL) films with cavities that are selectively decorated with protein by one‐step method is developed in this study. To carry out this method, proteins carried in water are dispersed into chloroform solution of PCL to form inverse emulsion with the assistance of the chitosan particles serving as emulsifier. The evaporation of the organic solvent in the inverse emulsion on substrate under a high‐humidity atmosphere leads to the formation of ordered porous arrays incorporated with proteins on the inner surface of the cavities. The method, based on the combination of breath figures and inverse emulsion template, provides a reliable route for the directed assembly of water‐soluble materials into patterned polymer matrix. It has the potential to be further established as a novel procedure to fabricate a multifunctional hybrid porous structure containing hydrophilic component based on the breath figure method.

Porogen Effect of Solvents on Pore Size Distribution of Solvent-Casted Polycaprolactone Thin Films

In this study, the effect of porogenic solvents on pore size distribution of the polycaprolactone (PCL) thin films was investigated. Five thin PCL films were prepared using the solvent-casting method. Chloroform, Methylene Chloride (MC) and three different compositions of MC/ Dimethylformamide (DMF) (80/20, 50/50 and 20/80) were used as solvents. Scanning Electron Microscopy (SEM) investigations were employed to study morphology and consequently the pore size distribution of the prepared films. The PCL films made by chloroform and MC as a solvent were completely non-porous. Whereas the other films (made by a combination of MC and DMF) showed both uni-modal and bi-modal pore size distributions.

Electrospun titania fiber mats spin coated with thin polymer films as nanofibrous scaffolds for enhanced cell proliferation.

The incorporation of inorganic materials into electrospun nanofibres has recently gained considerable attention for the development of extracellular matrix-like scaffolds with improved mechanical properties and enhanced biological functions for tissue engineering applications. In this study, polymer-inorganic composite fibres consisting of poly(2-ethyl-2-oxazoline) (PEOXA) and tetrabutyl titanate as the titanium precursor were successfully fabricated through a combined sol-gel/electrospinning approach. PEOXA/Ti(OR)n composite fibres were obtained with varying amounts of polymer and titanium precursors. Calcinations of the composite fibres were performed at varying temperatures to produce TiO2 fibres (TiO2 -T-60) with anatase, anatase/rutile mixed phase, and rutile crystal structures. Thin polymer films (i.e., poly(2-ethyl-2-oxazoline) (PEOXA), polycaprolactone (PCL), and poly(methyl methacrylate) (PMMA)) were subsequently deposited onto TiO2 -T-60 fibre mats by spin coating to facilitate handling of the electrospun substrates after calcination, which are rather brittle and disintegrate easily, and to probe cell-materials interactions. The cellular behaviour of mouse L929 fibroblasts after culture periods of 1-5days was compared on the following fibre scaffolds: PEOXA/Ti(OR)n , TiO2 -T-60 (T=600, 650, and 700°C), TiO2 -T-60 spin-coated with thin PCL film (PCL/TiO2 -T-60), and pure PCL. The results obtained from in vitro cell culture studies for the lactate dehydrogenase release assay and confocal microscopic visualization pointed out the synergistic interplay between the TiO2 crystal structure and spin-coated PCL film in facilitating cell interactions with the scaffold surface. The L929 cells were observed to adhere and proliferate better on the surface of TiO2 -700-60 having the rutile structure than on the surfaces of TiO2 -600-60 and TiO2 -650-60 fibre scaffolds with anatase and anatase/rutile mixed phase structures, respectively.

Tunable Drug Loading and Reinforcement of Polycaprolactone Films by Means of Electrospun Nanofibers of Glycolide Segmented Copolymers

AbstractElectrospinning of a segmented copolymer having polyglycolide hard segments is successfully performed from 1,1,1,3,3,3‐hexafluoroisopropanol solutions. During the process, a bactericidal agent, i.e., chlorhexidine (CHX), is effectively loaded, which results in nanofibers with a smaller diameter because of the change in solution conductivity. New fabrics based on molding of alternate layers of poly(ε‐caprolactone) (PCL) films and the electrospun scaffolds of the segmented copolymer are prepared and characterized. The thermal molding process renders a PCL matrix homogeneously reinforced with nanofibers that compensate for the loss of mechanical properties caused by incorporation of CHX. Release of CHX is evaluated in different media. Results vary depending on the layer where the drug is incorporated. Thus, systems with an immediate bacteriostatic effect, as well as systems with a potential long term antimicrobial effect, are obtained. Growth inhibition and adhesion assays demonstrate the fast bactericidal effect of samples with CHX loaded in its outer layers.

Surface and Protein Adsorption Properties of 316L Stainless Steel Modified with Polycaprolactone Film.

The surface and protein adsorption properties of 316L stainless steel (316L SS) modified with polycaprolactone (PCL) films are systematically investigated. The wettability of the PCL films was comparable to that of bare 316L SS because the rough surface morphology of the PCL films counteracts their hydrophobicity. Surface modification with PCL film significantly improves the corrosion resistance of the 316L SS because PCL is insulating in nature. A coating of PCL film effectively reduces the amount of adhered bovine serum albumin (BSA) on the surface of 316L SS in a bicinchoninic acid protein assay. PCL is both biodegradable and biocompatible, suggesting the potential for the surface modification of implants used in human bodies; in these applications, excellent corrosion resistance and anticoagulant properties are necessary.

Microfibrous Scaffolds Enhance Endothelial Differentiation and Organization of Induced Pluripotent Stem Cells.

Human induced pluripotent stem cells (iPSCs) are a promising source of endothelial cells (iPSC-ECs) for engineering three-dimensional (3D) vascularized cardiac tissues. To mimic cardiac microvasculature, in which capillaries are oriented in parallel, we hypothesized that endothelial differentiation of iPSCs within topographically aligned 3D scaffolds would be a facile one-step approach to generate iPSC-ECs as well as induce aligned vascular organization. Human iPSCs underwent endothelial differentiation within electrospun 3D polycaprolactone (PCL) scaffolds having either randomly oriented or parallel-aligned microfibers. Using transcriptional, protein, and endothelial functional assays, endothelial differentiation was compared between conventional two-dimensional (2D) films and 3D scaffolds having either randomly oriented or aligned microfibers. Furthermore, the role of parallel-aligned microfiber patterning on the organization of vessel-like networks was assessed. The cells in both the randomly oriented and aligned 3D scaffolds demonstrated an 11-fold upregulation in gene expression of the endothelial phenotypic marker, CD31, compared to cells on 2D films. This upregulation corresponded to >3-fold increase in CD31 protein expression in 3D scaffolds, compared to 2D films. Concomitantly, other endothelial phenotypic markers including CD144 and endothelial nitric oxide synthase also showed significant transcriptional upregulation in 3D scaffolds by >7-fold, compared to 2D films. Nitric oxide production, which is characteristic of endothelial function, was produced 4-fold more abundantly in 3D scaffolds, compared to on 2D PCL films. Within aligned scaffolds, the iPSC-ECs displayed parallel-aligned vascular-like networks with 70% longer branch length, compared to cells in randomly oriented scaffolds, suggesting that fiber topography modulates vascular network-like formation and patterning. Together, these results demonstrate that 3D scaffold structure promotes endothelial differentiation, compared to 2D substrates, and that aligned topographical patterning induces anisotropic vascular network organization.