Polycaprolactone Fibers Research Articles

Ascorbyl palmitate–PCL fiber mats loaded with strontium polyphosphate nanoparticles for guided bone regeneration

Multifunctional fiber mats are explored as potential bioactive matrices for the development of the next generation of guided bone regeneration membranes with tunable microstructure, strength and therapeutic activity. In the present study, polycaprolactone (PCL) nanofibers with different concentrations of ascorbic acid derivatives (ascorbyl palmitate) and strontium polyphosphate nanoparticles (Sr-polyP NPs) were fabricated. The obtained PCL mats scaffolds were assessed not only for microstructure structure features, including morphological observation, hydrophilicity and tensile strength, but also in vitro water uptake, biodegradation (under enzymatic and hydrolytic conditions), bioactivity using SBF, as well as ascorbic acid release study. The observed results showed that the mean fiber diameter of the PCL fibers (388 ± 340 nm) increased with the increase in the concentration of the ASP and Sr-polyP NPs. The addition of ascorbyl palmitate caused an increase in viscosity from 40.6 ± 2.5 to 66.6 ± 2.0 cP in the case of 20% AsP/PCL; however, it caused a decrease in conductivity from 7.3 ± 0.4 to 6.38 µs, while there was an obvious increase in the viscosity and conductivity by Sr-polyP Nps addition from 40.6 ± 2.5 cP in the case of PCL only to 88.3 ± 2.5 cP in the case of PA1/SP15. The contact angle decreases from 125.9 ± 2.5° in the case of PCL only to 112 ± 4 and 102 ± 2.4° in the case of 20% loaded ascorbyl palmitate-PCL mats and 15% Sr/PCL, respectively. Moreover, the assessment of the antioxidant activity of PCL fiber mats containing 10% and 20% ascorbyl palmitate demonstrated that the 20% ascorbyl palmitate-PCL fiber mats have a higher antioxidant effectiveness compared to the 10% mats. This could be attributed to the controlled release of ascorbic acid from PCL, which occurs after 7 days. However, the highest tensile strength was observed for 5% Sr-polyP NPs-loaded PCL/AsP mats at 1.52 ± 0.51 MPa. Further increase of Sr-polyP NPs content resulted in a clear decrease of tensile strength to 1.13 ± 0.13and 0.93 ± 0.71 for 10% and 20% ascorbyl palmitate-PCL mats, respectively. Importantly, the fabricated AsP and Sr-polyP NPs-loaded PCL fiber mats showed induction of calcium phosphate deposition in SBF and the ability to sustain release of ascorbic acid over a time period of 28 d, in addition to the enhancement in cell proliferation compared to PCL only suggesting their application as a favorable synthetic matrix to amplify guided bone regeneration process.Graphical abstract

Effects of electrospun fibers containing ascorbic acid on oxidative stress reduction for cardiac tissue engineering.

Tissue engineering provides promise for regeneration of cardiac tissue following myocardial infarction. However, the harsh microenvironment of the infarct hampers the efficacy of regenerative therapies. Ischemia-reperfusion injury dramatically increases the levels of reactive oxygen species (ROS) within the infarcted area, causing a cascade of further cellular injury. Implantable tissue engineered grafts can target this oxidative stress by delivering pharmaceutical compounds directly into the diseased tissue. Herein, we successfully fabricated electrospun polycaprolactone (PCL) fibers containing varying concentrations of ascorbic acid, a potent antioxidant well known for its ROS-scavenging capabilities. The antioxidant scaffolds displayed significantly improved scavenging of DPPH radicals, superoxide anions and hydroxyl radicals, in a dose dependent manner. Mechanical properties testing indicated that incorporation of ascorbic acid enhanced the strength and Young's modulus of the material, correlating with a moderate but non-significant increase in the crystallinity. Moreover, the scaffolds supported adhesion and maintained survival of human umbilical vein endothelial cells in vitro, indicating good cytocompatibility. These results provide motivation for the use of ascorbic acid-containing fibrous scaffolds to regulate the highly oxidative microenvironment following myocardial infarction.

Optimization of whole-cell bacterial bioreporter immobilization on electrospun cellulose acetate (CA) and polycaprolactone (PCL) fibers for arsenic detection.

Arsenic contamination is a critical global problem, and its widespread environmental detection is becoming a prominent issue. Herein, electrospun fibers of cellulose acetate (CA) and polycaprolactone (PCL) were successfully fabricated and used as the support material for immobilization of arsenic-sensing bacterial bioreporter for the first time. To date, no attempt has been made to immobilize fluorescent whole-cell bioreporter cells on electrospun fibers for arsenic detection. CA and PCL electrospun fibers were fabricated via traditional electrospinning technique and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and contact angle meter. Following immobilization of the bacterial bioreporter cells, the immobilized bacteria were also characterized by viability assay using AlamarBlue. The effects of growth phase and cell concentration on the fluorescence response of fiber-immobilized arsenic bioreporters to arsenic were also investigated. After immobilization of arsenic bioreporters on 10 wt% PCL fiber, 91% of bacterial cells remained viable, while this value was 55.4% for cells immobilized on 12.5 wt% CA fiber. Bioreporter cells in the exponential growth phase were shown to be more sensitive to arsenic compared to aged cells. While both the electropsun PCL- and CA-immobilized bioreporters successfully detected 50 and 100µg/L of arsenite (As (III)) concentrations, the PCL-immobilized bioreporter showed better fluorescence performance which should be investigated in future studies. This study helps to fill some gaps in the literature and demonstrates the potential for using electrospun fiber-immobilized arsenic whole-cell bioreporter for arsenic detection in water.

A Versatile Method to Create Perfusable, Capillary‐Scale Channels in Cell‐Laden Hydrogels Using Melt Electrowriting

AbstractA major obstacle toward creating human‐scale artificial tissue models is supplying encapsulated cells with oxygen and other nutrients throughout the construct. In particular, creating channels in hydrogels that match the resolution and density of the smallest blood capillaries (≤10 µm) remains highly challenging. Here, a novel method is demonstrated where polycaprolactone fibers printed using melt‐electrowriting are encapsulated in cell‐laden hydrogels and then physically removed to produce hollow, perfusable channels. This technique produces a range of channel diameters (10–41 µm) with circular cross‐sections and in hydrogels representing various crosslinking mechanisms. The channels can be formed as interconnected grids, hierarchically branched patterns, or stacked in layers with ≈200 µm channel spacing, thus matching average capillary density in the human body. Alternatively, selective removal of fibers from a melt electrowriting grid can generate perfusable channels within a reinforcing fiber network. This method can be performed in the presence of cells, with human fibroblasts exhibiting encapsulated in gelatin methacryloyl showing no detectable cytotoxic effects. This technique is a promising approach for creating perfusable channels with very small diameters within cell‐laden hydrogel matrices, with potential applications including in vitro tissue models and hydrogel microfluidics.

Aligned core–shell fibrous nerve wrap containing Bletilla striata polysaccharide improves functional outcomes of peripheral nerve repair

Peripheral nerve injuries are commonly encountered in extremity traumas. Their motor and sensory recovery following microsurgical repair is limited by slow regeneration speed (<1 mm/d) and subsequent muscle atrophy, which are consequently correlated with the activity of local Schwann cells and efficacy of axon outgrowth. To promote post-surgical nerve regeneration, we synthesized a nerve wrap consisting of an aligned polycaprolactone (PCL) fiber shell with a Bletilla striata polysaccharide (BSP) core (APB). Cell experiments demonstrated that the APB nerve wrap markedly promoted neurite outgrowth and Schwann cell migration and proliferation. Animal experiments applying a rat sciatic nerve repair model indicated that the APB nerve wrap restored conduction efficacy of the repaired nerve and the compound action potential as well as contraction force of the related leg muscles. Histology of the downstream nerves disclosed significantly higher fascicle diameter and myelin thickness with the APB nerve wrap compared to those without BSP. Thus, the BSP-loaded nerve wrap is potentially beneficial for the functional recovery after peripheral nerve repair and offers sustained targeted release of a natural polysaccharide with good bioactivity.

Biodegradable Polycaprolactone Fibers with Silica Aerogel and Nanosilver Particles Produce a Coagulation Effect.

Poly-ε-caprolactone (PCL) is a biodegradable aliphatic polyester that can be used in the field of biomaterials. Electrospinning is the name given to the process of producing micro and nanoscale fibers using electrostatically charged polymeric solutions under certain conditions. Almost all synthetic and naturally occurring polymers can undergo electrospinning using suitable solvents or mixtures prepared in certain proportions. In this study, silica aerogels were obtained by the sol-gel method. PCL-silica aerogel fibers were synthesized by adding 0.5, 1, 2, and 4% ratios in the PCL solution. Blood contact analysis was performed on the produced fibers with UV-VIS. According to the results obtained, 0.5, 1, 2, and 4% nano-silver were added to the fiber-containing 4% aerogel. Then, SEM-EDS and FTIR analyses were performed on all fibers produced. Antimicrobial tests were performed on fibers containing nano-silver. As a result, high-performance blood coagulation fibers were developed using PCL with aerogel, and an antimicrobial effect was achieved with nano-silver particles. It is thought that the designed surface will be preferred in wound dressing and biomaterial in tissue engineering, as it provides a high amount of cell adhesion with a small amount of blood and contains antimicrobial properties.

Surface-Embedding of Mo Microparticles for Robust and Conductive Biodegradable Fiber Electrodes: Toward 1D Flexible Transient Electronics.

Fiber-based implantable electronics are one of promising candidates for in vivo biomedical applications thanks to their unique structural advantages. However, development of fiber-based implantable electronic devices with biodegradable capability remains a challenge due to the lack of biodegradable fiber electrodes with high electrical and mechanical properties. Here, a biocompatible and biodegradable fiber electrode which simultaneously exhibits high electrical conductivity and mechanical robustness is presented. The fiber electrode is fabricated through a facile approach that incorporates a large amount of Mo microparticles into outermost volume of a biodegradable polycaprolactone (PCL) fiber scaffold in a concentrated manner. The biodegradable fiber electrode simultaneously exhibits a remarkable electrical performance (≈43.5 Ω cm-1 ), mechanical robustness, bending stability, and durability for more than 4000 bending cycles based on the Mo/PCL conductive layer and intact PCL core in the fiber electrode. The electrical behavior of the biodegradable fiber electrode under the bending deformation is analyzed by an analytical prediction and a numerical simulation. In addition, the biocompatible properties and degradation behavior of the fiber electrode are systematically investigated. The potential of biodegradable fiber electrode is demonstrated in various applications such as an interconnect, a suturable temperature sensor, and an in vivo electrical stimulator.

The effect of molecular weight and fiber diameter on the mechanical properties of single, electrospun PCL nanofibers

Biomaterials based on electrospun nanofibers are increasingly used in biomedical applications. Polycaprolactone (PCL) is a biocompatible, biodegradable, FDA-approved, synthetic polymer suitable for such applications. In this study, we used a nanomanipulation technique based on a combined atomic force/optical microscope to investigate key mechanical properties of electrospun PCL nanofibers as a function of PCL molecular weight (150 kDa, 114 kDa, and 74 kDa) and fiber diameter (20–250 nm). Mechanical properties extracted from different types of stress-strain curves included maximum stress and strain, elasticity, Young’s modulus, strain-dependent energy loss/storage, and stress relaxation time. We found that PCL molecular weight had a marginal effect on mechanical properties. In contrast, fiber diameter had a strong effect on fiber modulus. Specifically, extensibility, elastic limit, and stress relaxation time ranged from 123% to 133%, 16–44%, and 21–14 s, respectively. Energy loss/cycle was 35% for low strains (strain, 10–20%) and 65% for high strains (strain > 80%). The Young’s modulus decreased from 3000 MPa to 500 MPa as the diameter increased from 40 nm to 100 nm; above 100 nm, the diameter-dependence waned, and the fiber modulus approached the PCL bulk modulus of about 300 MPa. The diameter-dependence of the modulus opens the intriguing possibility of producing electrospun PCL nanofibers with very different stiffnesses simply by adjusting the fiber diameter.

Fabrication of Solvent-Free PCL/β-TCP Composite Fiber for 3D Printing: Physiochemical and Biological Investigation

Manufacturing three-dimensional (3D) objects with polymers/bioceramic composite materials has been investigated in recent years. In this study, we manufactured and evaluated solvent-free polycaprolactone (PCL) and beta-tricalcium phosphate (β-TCP) composite fiber as a scaffold material for 3D printing. To investigate the optimal ratio of feedstock material for 3D printing, the physical and biological characteristics of four different ratios of β-TCP compounds mixed with PCL were investigated. PCL/β-TCP ratios of 0 wt.%, 10 wt.%, 20 wt.%, and 30 wt.% were fabricated, with PCL melted at 65 °C and blended with β-TCP with no solvent added during the fabrication process. Electron microscopy revealed an even distribution of β-TCP in the PCL fibers, while Fourier transform infrared spectroscopy demonstrated that the biomaterial compounds remained intact after the heating and manufacturing process. In addition, adding 20% β-TCP into the PCL/β-TCP mixture significantly increased hardness and Young's Modulus by 10% and 26.5%, respectively, suggesting that PCL-20 has better resistance to deformation under load. Cell viability, alkaline phosphatase (ALPase) activity, osteogenic gene expression, and mineralization were also observed to increase according to the amount of β-TCP added. Cell viability and ALPase activity were 20% higher with PCL-30, while upregulation for osteoblast-related gene expression was better with PCL-20. In conclusion, PCL-20 and PCL-30 fibers fabricated without solvent exhibited excellent mechanical properties, high biocompatibility, and high osteogenic ability, making them promising materials for 3D printing customized bone scaffolds promptly, sustainably, and cost-effectively.

3D Electrospun Polycaprolactone Scaffolds to Assess Human Periodontal Ligament Cells Mechanobiological Behaviour.

While periodontal ligament cells are sensitive to their 3D biomechanical environment, only a few 3D in vitro models have been used to investigate the periodontal cells mechanobiological behavior. The objective of the current study was to assess the capability of a 3D fibrous scaffold to transmit a mechanical loading to the periodontal ligament cells. Three-dimensional fibrous polycaprolactone (PCL) scaffolds were synthetized through electrospinning. Scaffolds seeded with human periodontal cells (103 mL-1) were subjected to static (n = 9) or to a sinusoidal axial compressive loading in an in-house bioreactor (n = 9). At the end of the culture, the dynamic loading seemed to have an influence on the cells' morphology, with a lower number of visible cells on the scaffolds surface and a lower expression of actin filament. Furthermore, the dynamic loading presented a tendency to decrease the Alkaline Phosphatase activity and the production of Interleukin-6 while these two biomolecular markers were increased after 21 days of static culture. Together, these results showed that load transmission is occurring in the 3D electrospun PCL fibrous scaffolds, suggesting that it can be used to better understand the periodontal ligament cells mechanobiology. The current study shows a relevant way to investigate periodontal mechanobiology using 3D fibrous scaffolds.

Composite grafts made of polycaprolactone fiber mats and oil-based calcium phosphate cement pastes for the reconstruction of cranial and maxillofacial defects

ObjectivesSynthetic bone substitutes which can be adapted preoperatively and patient specific may be helpful in various bony defects in the field of oral- and maxillofacial surgery. For this purpose, composite grafts made of self-setting and oil-based calcium phosphate cement (CPC) pastes, which were reinforced with 3D-printed polycaprolactone (PCL) fiber mats were manufactured.Materials and methodsBone defect models were acquired using patient data from real defect situations of patients from our clinic. Using a mirror imaging technique, templates of the defect situation were fabricated via a commercially available 3D-printing system. The composite grafts were assembled layer by layer, aligned on top of these templates and fitted into the defect situation. Besides, PCL-reinforced CPC samples were evaluated regarding their structural and mechanical properties via X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM), and 3-point-bending testing.ResultsThe process sequence including data acquisition, template fabrication, and manufacturing of patient specific implants proved to be accurate and uncomplicated. The individual implants consisting mainly of hydroxyapatite and tetracalcium phosphate displayed good processability and a high precision of fit. The mechanical properties of the CPC cements in terms of maximum force and stress load to material fatigue were not negatively affected by the PCL fiber reinforcement, whereas clinical handling properties increased remarkably.ConclusionPCL fiber reinforcement of CPC cements enables the production of very freely modelable three-dimensional implants with adequate chemical and mechanical properties for bone replacement applications.Clinical relevanceThe complex bone morphology in the region of the facial skull often poses a great challenge for a sufficient reconstruction of bony defects. A full-fledged bone replacement here often requires the replication of filigree three-dimensional structures partly without support from the surrounding tissue. With regard to this problem, the combination of smooth 3D-printed fiber mats and oil-based CPC pastes represents a promising method for fabricating patient specific degradable implants for the treatment of various craniofacial bone defects.

Low-dose celecoxib-loaded PCL fibers reverse intervertebral disc degeneration by up-regulating CHSY3 expression

Intervertebral disc degeneration (IDD) has been identified as one of the predominant factors leading to persistent low back pain and disability in middle-aged and elderly people. Dysregulation of Prostaglandin E2 (PGE2) can cause IDD, while low-dose celecoxib can maintain PGE2 at the physiological level and activate the skeletal interoception. Here, as nano fibers have been extensively used in the treatment of IDD, novel polycaprolactone (PCL) nano fibers loaded with low-dose celecoxib were fabricated for IDD treatment. In vitro studies demonstrated that the nano fibers had the ability of releasing low-dose celecoxib slowly and sustainably and maintain PGE2. Meanwhile, in a puncture-induced rabbit IDD model, the nano fibers reversed IDD. Furthermore, low-dose celecoxib released from the nano fibers was firstly proved to promote CHSY3 expression. In a lumbar spine instability-induced mouse IDD model, low-dose celecoxib inhibited IDD in CHSY3wt mice rather than CHSY3−/− mice. This model indicated that CHSY3 was indispensable for low-dose celecoxib to alleviate IDD. In conclusion, this study developed a novel low-dose celecoxib-loaded PCL nano fibers to reverse IDD by maintaining PGE2 at the physiological level and promoting CHSY3 expression.

Polycaprolactone nanofiber-alginate hydrogel interpenetrated skin substitute for regulation of wound-substitute interface

The management of the interface between the wound microenvironment and the skin substitute (SSS) is fundamental to wound repair and is an important factor in the regeneration of damaged tissue. Current biomaterials result in unideal repair effect of defective tissue due to limited management of early wound exudate and inability to respond positively to endogenous growth factors. Based on a refined electrospinning process, polycaprolactone fiber - alginate hydrogel interpenetrated network scaffold and subsequent multifunctional modifications serving as SSS was developed. The SSS exhibits excellent water absorption, water vapor permeability rate > 6000 g/m2/day and stretching properties. The amino-terminated hyperbranched polyamide enables the scaffold with both rapid antibacterial and reactive oxygen scavenging properties. Furthermore, fibroblast cells can be proliferated in the scaffold by 3D infiltration (>100 μm). Thus, the scaffolds are expected to be ideal candidates for the repair of different defective skin, especially those with excessive exudate.

Fiber diameters and parallel patterns: proliferation and osteogenesis of stem cells.

Due to the innate extracellular matrix mimicking features, fibrous materials exhibited great application potential in biomedicine. In developing excellent fibrous biomaterial, it is essential to reveal the corresponding inherent fiber features' effects on cell behaviors. Due to the inevitable 'interference' cell adhesions to the background or between adjacent fibers, it is difficult to precisely reveal the inherent fiber diameter effect on cell behaviors by using a traditional fiber mat. A single-layer and parallel-arranged polycaprolactone fiber pattern platform with an excellent non-fouling background is designed and constructed herein. In this unique material platform, the 'interference' cell adhesions through interspace between fibers to the environment could be effectively ruled out by the non-fouling background. The 'interference' cell adhesions between adjacent fibers could also be excluded from the sparsely arranged (SA) fiber patterns. The influence of fiber diameter on stem cell behaviors is precisely and comprehensively investigated based on eliminating the undesired 'interference' cell adhesions in a controllable way. On the SA fiber patterns, small diameter fiber (SA-D1, D1 means 1 μm in diameter) may seriously restrict cell proliferation and osteogenesis when compared to the middle (SA-D8) and large (SA-D56) ones and SA-D8 shows the optimal osteogenesis enhancement effect. At the same time, the cells present similar proliferation ability and even the highest osteogenic ability on the densely arranged (DA) fiber patterns with small diameter fiber (DA-D1) when compared to the middle (DA-D8) and large (DA-D56) ones. The 'interference' cell adhesion between adjacent fibers under dense fiber arrangement may be the main reason for inducing these different cell behavior trends along with fiber diameters. Related results and comparisons have illustrated the effects of fiber diameter on stem cell behaviors more precisely and objectively, thus providing valuable reference and guidance for developing effective fibrous biomaterials.

Piezoelectric conductive electrospun nanocomposite PCL/Polyaniline/Barium Titanate scaffold for tissue engineering applications

Recent trends in tissue engineering technology have switched to electrical potentials generated through bioactive scaffolds regarding their appropriate effects on cell behaviors. Preparing a piezo-electrical stimuli scaffold with high electrical conductivity for bone and cartilage tissue regeneration is the ultimate goal of the present study. Here, Barium Titanate nanoparticles (BaTiO3 NPs) were used as piezoelectric material and highly conductive binary doped Polyaniline nanoparticles (PANI NPs) were synthesized by oxidative polymerization. Polycaprolactone (PCL) was applied as carrier substrate polymer and conductive spun nanofibrous scaffolds of PCL/PANI composites were prepared in two different amounts of PANI (3 and 5 wt.%). The conductivity of PCL/PANI nanofibers has been analyzed by standard four probes test. Based on the obtained results, the PCL/PANI5 (with 5 wt.% PANI) was selected due to the superior electrical conductivity of 8.06 × 10–4 s cm - 1. Moreover, the piezoelectric nanofibrous scaffolds of PCL/BT composite were electrospun in three different amounts of BT (20, 30, and 40 wt.%). To investigate the synergic effect of conductive PANI and piezoelectric BT, ternary nanocomposite scaffolds of PCL/PANI/BT were prepared using the dual jet electrospinning technique. The piezoelectric properties have been analyzed by determining the produced voltage. The morphological assessment, contact angle, mechanical test, and MTT assay have been conducted to evaluate other properties including biocompatibility of nanofibrous scaffolds. The PCL/PANI5/BT40 composite resulted in an unprecedented voltage of 1.9 Volt. SEM results confirm that BT NPs have been distributed and embedded inside PCL fibers quite appropriately. Also, the chosen scaffolds were homogeneously intertwined and possessed an average fiber diameter of 288 ± 180 nm, and a contact angle of 92 ± 7°, making it a desirable surface for cell attachment and protein interactions. Moreover, Young’s modulus, ultimate tensile stress, and elongation were obtained as 11 ± 1 MPa, 5 ± 0.6 MPa, and 109 ± 15% respectively. Obtained results assert the novel potential of piezo-electrical stimuli conductive nanocomposite scaffold for tissue engineering applications.

A novel approach to bio-mineralization of electrospun PCL scaffolds by protein and hydroxyapatite nanoparticles; molecular dynamics simulation and in-vitro evaluation

The nano-fibrous polycaprolactone (PCL) scaffolds are one of the promising materials for bone tissue engineering. However, the role of protein in the bio-mineralization of PCL fibers is not clear. This study aims to find how a protein (e.g. bovine serum albumin (BSA)) is attached to the hydroxyapatite (HA) nanoparticles (NPs) loaded on the PCL fiber, and it affected the bio-mineralization of a hybrid scaffold. The molecular dynamic (MD) simulation was utilized to explore the protein and HA attachment. The results of MD simulation indicated that the a(b)-planes of HA crystal and glutamic acid (Glu) from BSA molecule have critical roles in attachment together. In the following, the electrospinning method was applied to synthesize the pristine and hybrid PCL scaffolds to evaluate the MD results. The scanning electron microscopy (SEM) images showed that BSA could be successfully attached to the HA NPs, and coiled around the PCL-HA junction confirming the MD simulation. To evaluate the bio-mineralization, the in-vitro immersion test in the simulation body fluid (SBF) solution and the cytocompatibility of scaffolds by the MG63 osteosarcoma cells were studied. The results indicated better osteoconduction and bone regeneration for the hybrid PCL- BSA-HA scaffold because of the synergic effects of HA NPs and BSA protein.

Biocompatible and antimicrobial multilayer fibrous polymeric wound dressing with optimally embedded silver nanoparticles

The demand for advanced, biocompatible wound dressings with antibacterial properties is increasing in order to treat people with severe skin wounds, such as burn victims or those suffering from ulcers. We have developed an ultrafine three-layer polymer nanofiber mesh using electrospinning that is able to kill bacteria (Escherichia coli; E. coli and Staphylococcus aureus; S. aureus) but also has cytocompatibility properties. The first layer was generated with polystyrene (PS) for strength and functions as a carrier layer. The second layer consisted of polycaprolactone (PCL) with silver nanoparticles (Ag NPs) that were added to the spinning solution, which had antibacterial properties. Finally, the third layer comprised of polyethylene oxide (PEO) acting as a hydrophilic, barrier layer that was also non-adhesive, with the potential to further assist in wound healing. Systematic physicochemical and biological characterization was performed including dynamic light scattering (DLS), UV spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), water contact angles, evaluation of antibacterial properties, and cell attachment and proliferation assays. The cumulative Ag ion release was optimized for a period up to 84 days in physiologically similar media at physiological temperature. Chemical, mechanical, and biological analysis demonstrated that incorporation of Ag NPs at higher quantities into the PCL fibers layer providing excellent antimicrobial activity with minimal toxicity at low concentration. The findings highlight the importance of optimizing the properties of Ag based antibacterial meshes to find the balance between high antibacterial activity and low toxicity.

Electrospun-Reinforced Suturable Biodegradable Artificial Cornea.

Despite rigorous investigations, the hydrogels currently available to replace damaged tissues, such as the cornea, cannot fulfill mechanical and structural requirements and, more importantly, cannot be sutured into host tissues due to the lack of hierarchical structures to dissipate exerted stress. In this report, solution electrospinning of polycaprolactone (PCL), protein-based hydrogel perfusion, and layer-by-layer stacking are used to generate a hydrogel-microfiber composite with varying PCL fiber diameters and hydrogel concentrations. Integrating PCL microfibers into the hydrogel synergistically improves the mechanical properties and suturability of the construct up to 10-fold and 50-fold, respectively, compared to the hydrogel and microfiber scaffolds alone, approaching those of the corneal tissue. Human corneal cells cultured on composites are viable and can spread, proliferate, and retain phenotypic characteristics. Moreover, corneal stromal cells migrate into the scaffold, degrade it, and regenerate the extracellular matrix. The current hydrogel reinforcing system paves the way for producing suturable and, therefore, transplantable tissue constructs with desired mechanical properties.

Melt electrowriting of PLA, PCL, and composite PLA/PCL scaffolds for tissue engineering application

Fabrication of well-ordered and bio-mimetic scaffolds is one of the most important research lines in tissue engineering. Different techniques have been utilized to achieve this goal, however, each method has its own disadvantages. Recently, melt electrowriting (MEW) as a technique for fabrication of well-organized scaffolds has attracted the researchers’ attention due to simultaneous use of principles of additive manufacturing and electrohydrodynamic phenomena. In previous research studies, polycaprolactone (PCL) has been mostly used in MEW process. PCL is a biocompatible polymer with characteristics that make it easy to fabricate well-arranged structures using MEW device. However, the mechanical properties of PCL are not favorable for applications like bone tissue engineering. Furthermore, it is of vital importance to demonstrate the capability of MEW technique for processing a broad range of polymers. To address aforementioned problems, in this study, three ten-layered box-structured well-ordered scaffolds, including neat PLA, neat PCL, and PLA/PCL composite are fabricated using an MEW device. Printing of the composite PLA/PCL scaffold using the MEW device is conducted in this study for the first time. The MEW device used in this study is a commercial fused deposition modeling (FDM) 3D printer which with some changes in its setup and configuration becomes prepared for being used as an MEW device. Since in most of previous studies, a setup has been designed and built for MEW process, the use of the FDM device can be considered as one of the novelties of this research. The printing parameters are adjusted in a way that scaffolds with nearly equal pore sizes in the range of 140 µm to 150 µm are fabricated. However, PCL fibers are mostly narrower (diameters in the range of 5 µm to 15 µm) than PLA fibers with diameters between 15 and 25 µm. Unlike the MEW process of PCL, accurate positioning of PLA fibers is difficult which can be due to higher viscosity of PLA melt compared to PCL melt. The printed composite PLA/PCL scaffold possesses a well-ordered box structure with improved mechanical properties and cell-scaffold interactions compared to both neat PLA and PCL scaffolds. Besides, the composite scaffold exhibits a higher swelling ratio than the neat PCL scaffold which can be related to the presence of less hydrophobic PLA fibers. This scaffold demonstrates an anisotropic behavior during uniaxial tensile test in which its Young’s modulus, ultimate tensile stress, and strain to failure all depend on the direction of the applied tensile force. This anisotropy makes the composite PLA/PCL scaffold an exciting candidate for applications in heart tissue engineering. The results of in-vitro cell viability test using L929 mouse murine fibroblast and human umbilical vein endothelial (HUVEC) cells demonstrate that all of the printed scaffolds are biocompatible. In particular, the composite scaffold presents the highest cell viability value among the fabricated scaffolds. All in all, the composite PLA/PCL scaffold shows that it can be a promising substitution for neat PCL scaffold used in previous MEW studies.

Braided suture-reinforced fibrous yarn bundles as a scaffold for tendon tissue engineering in extensor digitorum tendon repair

In this study, we intend to develop an effective tendon tissue engineering scaffold that can provide mechanical stability and tendon regeneration ability. Using a novel electrospinning process, a biodegradable suture was continuously covered with aligned polycaprolactone fibers in core/sheath structure to produce a single yarn. The single yarn was braided together to fabricate a multi yarn (MY) scaffold, which can be surface modified with oxygen plasma and conjugated with heparin. The fibroblast growth factor 2 (FGF2) was bound to MY through bioaffinity between heparin and FGF2 to generate a functional scaffold (MY-FGF2) suitable for extensor digitorum tendon (EDT) repair. The physico-chemical properties of the scaffolds were characterized throughout the modification steps using microscopy, spectroscopy and mechanical testing. In vitro static culture using rabbit tendon-derived fibroblasts (rTFs) indicates combined effects of FGF2 and fiber alignment can enhance cell proliferation and extracellular matrix synthesis rates, as well as fasten tendon maturation. The cytoskeleton staining further endorses aligned morphology of fibers direct cell growth and collagen fiber deposition along the fiber axial direction, mimicking native tendon features. The dynamic culture in a bioreactor under uniaxial cyclic tensile loading authenticates 5 % mechanical stimulation can further increase cell proliferation and tenogenic differentiation rates compared to static culture. After mechanical stimulation for 7 days in vitro, the MY-FGF2/rTFs construct was used for repair of EDT defects in rabbits. The retrieved MY-FGF2/rTFs sample 6-week post-implantation shows superior mechanical properties and tendon regeneration abilities over acellular MY-FGF2. Taken together, we demonstrate a combinatory approach with MY-FGF2 where chemical and physical cues provided by FGF2, fiber alignment and dynamic stimulation contribute to tendon regeneration with a specific focus on EDT repair.