Composite Polymeric Membranes with Directionally Embedded Fibers for Controlled Dual Actuation.

In this paper, preparation method and actuation properties of an innovative composite membrane composed of thermo- and pH-responsive poly(N-isopropylacrylamide-co-acrylic acid) fibers (average diameter ≈ 905 nm) embedded within a passive thermoplastic polyurethane (TPU) matrix at different angles with degree of alignment as high as 98% are presented. The composite membrane has a gradient of TPU along the thickness. It has the capability of temperature- and pH-dependent direction-, and size-controlled actuation in few minutes. The stresses generated at the responsive fiber and nonresponsive matrix provide actuation, whereas the angle at which fibers are embedded in the matrix controls the actuation direction and size. The temperature has no effect on actuation and actuated forms at pH 7 and above, whereas the size of the actuated forms can be controlled by the temperature at lower pH. The membranes are strong enough to reversibly lift and release ≈426 times weight of their own mass (2.47 g metal ring is lifted by a 5.8 mg membrane). Soft actuators are of interest as smart scaffolds, robotics, catalysis, drug release, energy storage, electrodes, and metamaterials.

Poly(sodium methacrylate)/eggshell particles hydrogel composites as dye sorbent.

Eggshell (ES) particles as an available and low-cost waste material were utilized to prepare novel hydrogel composites for dye adsorbing application. For this purpose, solution polymerization of sodium methacrylate was carried out in the presence of ES particles with various size ranges. Results showed that incorporation of ES particles resulted in heterogeneous pores and cavities in the structure of the poly(sodium methacrylate) (PNaMA) matrix. Hydrogel composites with lower content (20 wt%) and smaller size (<75 µm) of ES particles presented higher water absorption capacity. The equilibrium water absorption values in distilled water were higher than phosphate buffered saline medium. ES particles showed low methylene blue (MB) and crystal violet (CV) adsorption capacities due to electrostatic repulsion of the positively charged species on the surface of ES particles and dye molecules. In contrast, hydrogel composites depicted fast and considerable dye adsorbability. The combination of 60 wt% ES particles within PNaMA provided a cost-effective adsorbent with similar CV adsorption capacity compared with the unfilled matrix, while MB removal was slightly decreased. The dye adsorption by either ES particles or hydrogel composites followed the pseudo-second-order kinetics, indicating that chemical sorption is the rate-limiting step for both of them.

Influence of the hard segments content on the properties of electrospun aliphatic poly(carbonate-urethane-urea)s.

The study investigated the impact of hard segments (HS) content on the morphology and thermomechanical properties of electrospun aliphatic poly(carbonate-urea-urethane)s (PCUUs). The obtained nonwovens exhibited surface porosity ranging from 50% to 57%, and fiber diameters between 0.59 and 0.71 µm. Notably, the PCUUs nonwovens with the highest HS content (18%) displayed superior mechanical properties compared to those with lower HS contents. This study highlights the ability to customize the properties of polymeric nonwovens based on their chemical compositions, offering tailored solutions for specific application needs.

Chemical Immobilization of Carboxymethyl Chitosan on Polycaprolactone Nanofibers as Osteochondral Scaffolds.

Carboxymethyl chitosan (CMC) as a bio-based osteochondral inductive material was chemically immobilized on the surface of polycaprolactone (PCL) nanofibers to fabricate scaffolds for osteochondral tissue engineering applications. The chemical immobilization process included the aminolysis of ester bonds and bonding of the primary amines with glutaraldehyde as a coupling agent. The SEM and FTIR results confirmed the successfulness of the CMC immobilization. The fabricated scaffolds presented cell viabilities of > 82% and supported the attachment and proliferation of the human bone marrow mesenchymal stem cells (hBM-MSCs). The CMC-immobilized scaffolds concentration dependently induced the diverse osteochondral differentiation pathways for the hBM-MSCs without using any external differential agents. According to the Alcian Blue and Alizarin Red staining and immunocytochemistry results, scaffolds with a higher content of CMC presented more chondro-inductivity and less osteoinductivity. Thus, the CMC-immobilized scaffolds can be employed as great potential candidates for osteochondral tissue engineering applications.

Carboxymethyl Chitosan-Functionalized Polyaniline/Polyacrylonitrile Nano-Fibers for Neural Differentiation of Mesenchymal Stem Cells.

Electroconductive scaffolds based on polyaniline (PANi)/polyacrylonitrile (PAN) were fabricated and surface-functionalized by carboxymethyl chitosan (CMC) as efficient scaffolds for nerve tissue regeneration. The results of scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and water contact angle measurement approved the successful fabrication of CMC-functionalized PANi/PAN-based scaffolds. Human adipose-derived mesenchymal stem cells (hADMSCs) were cultured on the scaffolds for 10 d in the presence or absence of ß-carotene (ßC, 20 µM) as a natural neural differentiation agent. The MTT and SEM results confirmed the attachment and proliferation of hADMSCs on the scaffolds. The expression of MAP2 at the mRNA and protein levels showed the synergic neurogenic induction effect of CMC-functionalization and ßC for hADMSCs on the scaffolds. The CMC-functionalized nanofibrous PANi/PAN-based scaffolds are potential candidates for nerve tissue engineering.

Electrospun Poly(carbonate-urea-urethane)s Nonwovens with Shape-Memory Properties as a Potential Biomaterial.

Poly(carbonate-urea-urethane) (PCUU)-based scaffolds exhibit various desirable properties for tissue engineering applications. This study thus aimed to investigate the suitability of PCUU as polymers for the manufacturing of nonwoven mats by electrospinning, able to closely mimic the fibrous structure of the extracellular matrix. PCUU nonwovens of fiber diameters ranging from 0.28 ± 0.07 to 0.82 ± 0.12 µm were obtained with an average surface porosity of around 50-60%. Depending on the collector type and solution concentration, a broad range of tensile strengths (in the range of 0.3-9.6 MPa), elongation at break (90-290%), and Young's modulus (5.7-26.7 MPa) at room temperature of the nonwovens could be obtained. Furthermore, samples collected on the plate collector showed a shape-memory effect with a shape-recovery ratio (Rr) of around 99% and a shape-fixity ratio (Rf) of around 96%. Biological evaluation validated the inertness, stability, and lack of cytotoxicity of PCUU nonwovens obtained on the plate collector. The ability of mesenchymal stem cells (MSCs) and endothelial cells (HUVECs) to attach, elongate, and grow on the surface of the nonwovens suggests that the manufactured nonwovens are suitable scaffolds for tissue engineering applications.

Synthesis and evaluation of novel absorptive and antibacterial polyurethane membranes as wound dressing.

Preparation and evaluation of new polyurethane membranes for wound dressing application was considered in this work. The membranes were prepared through amine curing reaction of epoxy-terminated polyurethane prepolymers and an antibacterial epoxy-functional quaternary ammonium compound (glycidyltriehtylammonium chloride, GTEACl. To render the prepared membranes to be highly absorptive of wound exudates, poly (ethylene glycol) polyols were introduced into the polyurethane networks. Evaluation of biocompatibity via both MTT assay and direct contact with two different cell lines (fibroblast and epidermal keratinocytes) reveled that membranes with appropriate loading of GTEACl showed proper biocompatibility. Promising antibacterial activity of the prepared membranes against Staphylococcus aureus and Escherichia coli bacteria was confirmed by both agar diffusion and shaking flask methods. The membranes with balanced crosslink density and ionic groups' concentration possessed appropriate hydrophilicity and water vapor transmission rate; therefore, they could prevent the accumulation of exudates and decrease the surface inflammation in the wounded area.

Laponite/amoxicillin-functionalized PLA nanofibrous as osteoinductive and antibacterial scaffolds.

In this study, Amoxicillin (AMX) was loaded on laponite (LAP) nanoplates and then immobilized on the surface of electrospun polylactic acid (PLA) nanofibers to fabricate scaffolds with osteoinductive and antibacterial activities. The highest loading efficiency (49%) was obtained when the concentrations of AMX and LAP were 3 mg/mL and 1 mg/mL, respectively. FTIR and XRD spectroscopies and zeta potentiometry confirmed the successful encapsulating of AMX within LAP nanoplates. The immobilization of AMX-loaded LAPs on the surface of PLA nanofibers was verified by SEM and FTIR spectroscopy. In vitro release study showed a two-phase AMX release profile for the scaffolds; an initial burst release within the first 48 h and a later sustained release up to 21 days. In vitro antibacterial tests against Staphylococcus aureus and Escherichia coli presented the ability of scaffolds to inhibit the growth of both bacteria. The biocompatibility assays revealed the attachment and viability of human bone marrow mesenchymal stem cells (hBMSCs) cultured on the surface of scaffolds (p ≤ 0.05). The increased ALKALINE PHOSPHATASE (ALP) activity (p ≤ 0.001), calcium deposition, and expression of ALP and OSTEONECTIN genes indicated the osteoinductivity of functionalized scaffolds for hBMSCs. These LAP/AMX-functionalized scaffolds might be desirable candida for the treatment of bone defects.

Photo-Curing Kinetics of 3D-Printing Photo-Inks Based on Urethane-Acrylates.

In this study, photo-curing kinetics for urethane-acrylate-based photo-inks for 3D printing were evaluated using a photo-differential scanning calorimetry analysis. Initially, the photopolymerization kinetics of di- and monofunctional monomers were separately studied at different temperatures (5-85 °C). Later, the photo-curing kinetics and mechanical properties of photo-inks based on different monomer mixtures (40/60-20/80) were evaluated. The results showed that urethane-dimethacrylate (UrDMA) and urethane-acrylate (UrA) had no light absorption in the region of 280-700 nm, making them a proper crosslinker and a reactive diluent, respectively, for the formulation of 3D-printing photo-inks. The kinetics investigations showed a temperature dependency for the photo-curing of UrDMA, where a higher photopolymerization rate (Rp,max: from 5.25 × 10-2 to 8.42 × 10-2 1/s) and double-bound conversion (DBCtotal: from 63.8% to 92.2%) were observed at elevated temperatures (5-85 °C), while the photo-curing of UrA was independent of the temperature (25-85 °C). Enhancing the UrA content from 60% to 80% in the UrDMA/UrA mixtures initially increased and later decreased the photopolymerization rate and conversion, where the mixtures of 30/70 and 25/75 presented the highest values. Meanwhile, increasing the UrA content led to lower glass transition temperatures (Tg) and mechanical strength for the photo-cured samples, where the mixture of 30/70 presented the highest maximum elongation (εmax: 73%).

Innovative application of magnetically modified bovine horn as a natural keratin resource in the role of value-added organocatalyst.

This study presents the conversion of bovine horn powder (BHP) as an available and low-cost waste material to a value-added highly recyclable catalyst. This green catalyst was prepared through the immobilization of BHP, as a natural keratin resource, on the magnetic Fe3O4 nanoparticles. The successful preparation of the catalyst was fully investigated using Fourier transform infrared, X-ray diffraction, and energy-dispersive X-ray spectroscopies as well as field emission scanning electron microscopy, vibrating sample magnetometry, and thermogravimetry. The catalytic efficiency of the prepared magnetic organocatalyst was evaluated in the synthesis of a large series of amide derivatives through the solvent-free transamidation reaction of different amides and amines with yields of 75-96%.

Green Chemistry for Biomimetic Materials: Synthesis and Electrospinning of High-Molecular-Weight Polycarbonate-Based Nonisocyanate Polyurethanes.

Conventional synthesis routes for thermoplastic polyurethanes (TPUs) still require the use of isocyanates and tin-based catalysts, which pose considerable safety and environmental hazards. To reduce both the ecological footprint and human health dangers for nonwoven TPU scaffolds, it is key to establish a green synthesis route, which eliminates the use of these toxic compounds and results in biocompatible TPUs with facile processability. In this study, we developed high-molecular-weight nonisocyanate polyurethanes (NIPUs) through transurethanization of 1,6-hexanedicarbamate with polycarbonate diols (PCDLs). Various molecular weights of PCDL were employed to maximize the molecular weight of NIPUs and consequently facilitate their electrospinnability. The synthesized NIPUs were characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The highest achieved molecular weight (M w) was 58,600 g/mol. The NIPUs were consecutively electrospun into fibrous scaffolds with fiber diameters in the submicron range, as shown by scanning electron microscopy (SEM). To assess the suitability of electrospun NIPU mats as a possible biomimetic load-bearing pericardial substitute in cardiac tissue engineering, their cytotoxicity was investigated in vitro using primary human fibroblasts and a human epithelial cell line. The bare NIPU mats did not need further biofunctionalization to enhance cell adhesion, as it was not outperformed by collagen-functionalized NIPU mats and hence showed that the NIPU mats possess a great potential for use in biomimetic scaffolds.

Developing non-isocyanate urethane-methacrylate photo-monomers for 3D printing application.

Urethane-methacrylate photo-monomers were prepared via a non-isocyanate route for the 3D printing application. The monomers were synthesized through reacting aliphatic amines, i.e. 1,6-hexanediamine, 1,4-butanediol bis(3-aminopropyl) ether, or n-butylamine, with cyclic carbonates, i.e. ethylene carbonate or propylene carbonate, followed by the methacrylation of the generated hydroxylurethanes. The effects of the chemical structure of monomers on their photo-reactivity and physicomechanical properties of the cured samples were studied. Propylene carbonate generated side methyl groups within the urethane block, which significantly limited the crystallization of the monomers resulting in high photo-reactivity (R p,max = 6.59 × 10-2 s-1) and conversion (DBCtotal = 85%). The ether bonds of 1,4-butanediol bis(3-aminopropyl) ether decreased the intermolecular hydrogen bonding between urethane blocks, which not only improved the photo-reactivity (R p,max = 8.18 × 10-2 s-1) and conversion (DBCtotal = 86%) of the monomer but led to a high crosslinking density (ν c = 5140 mol m-3) and more flexibility for the cured sample. An ink was developed based on the monomers and successfully 3D printed on a digital light processing machine. In the absence of toxic isocyanates and tin compounds, the non-isocyanate route can be employed to develop urethane-methacrylates with desirable photo-reactivity and physicomechanical properties as good candidates to formulate inks for 3D printing of biomedical materials.

Enhanced Adipose Mesenchymal Stem Cells Proliferation by Carboxymethyl-Chitosan Functionalized Polycaprolactone Nanofiber.

Background: Through combining two synthetic and natural polymers, scaffolds can be developed for tissue engineering and regenerative medicine purposes. Methods: In this work, carboxymethyl chitosan (CMC; 20%) was grafted to Polycaprolactone (PCL) nanofibers using the cold atmospheric plasma of helium. The PCL scaffolds were exposed to CAP, and functional groups were developed on the PCL surface. Results: The results of Fourier Transform Infrared Spectroscopy confirmed CMC (20%) graft on PCL scaffold. The Thiazolyl blue tetrazolium bromide assay showed a significant enhancement (p < 0.05) in the cell affinity and proliferation of adipose-derived stem cells (ADSCs) to CMC20%-graft-PCL scaffolds. After 14 days, bone differentiation was affirmed through alizarin red and calcium depositions. Conclusion: Based on the results, the CMC20%-graft-PCL can support the proliferation of ADSCs and induce the differentiation into bone with longer culture time.

Osteoinductivity of polycaprolactone nanofibers grafted functionalized with carboxymethyl chitosan: Synergic effect of ß-carotene and electromagnetic field.

In this study, carboxymethyl chitosan (CMC) was grafted on polycaprolactone (PCL) nanofibers to fabricate scaffolds for bone tissue engineering. The electrospun PCL nanofibers were treated by cold atmospheric plasma (CAP) of helium to generate the reactive functions necessary for CMC grafting. ß-carotene (ßC) as a biochemical clue and electromagnetic field (EMF, 31.4 µT, 1 h per day) as a biophysical stimulator were used to promote the proliferation and osteodifferentiation of adipose mesenchymal stem cells (ADSCs). Alizarin red staining and calcium content results indicated the generation of nodal calcium on the CMC30%-g-PCL scaffold after 14 days of incubation in the presence or absence of external stimulation factors. Immunocytochemistry (ICC) results confirmed the expression of osteonectin protein for the stem cells seeded on CMC30%-g-PCL with or without using ßC or EMF. These results suggest that the fabricated CMC-grafted scaffolds have the ability to self-differentiate stem cells to osteoblasts due to the osteoinductive effects of the grafted CMC. Furthermore, the osteodifferentiation of ADSCs is promoted by using an external stimulation factor such as ßC or EMF.

Bone morphogenic protein-2 immobilization by cold atmospheric plasma to enhance the osteoinductivity of carboxymethyl chitosan-based nanofibers.

Electrospun polycaprolactone/carboxymethyl chitosan (PCL/CMC) nanofibers treated by helium cold atmospheric plasma (CAP) and grafted with bone morphogenic protein-2 (BMP-2) were used scaffolds for the osteodifferentiation of stem cells to. For in vitro study, human bone marrow-derived mesenchymal stem cells (hMSCs) were cultured on these scaffolds, and their behaviors were assessed via optical microscopy, MTT assay, and SEM. The osteogenic differentiation of the hMSCs was evaluated by calcium content and alkaline phosphatase assays, Alizarin red and immunofluorescence (ICC) staining, and RT-PCR. The results showed that scaffolds not only can support the proliferation of hMSCs but also can promote their differentiation to osteoblasts without using any external osteogenic differential agent. The RT-PCR and ICC data revealed that the CAP treatment and BMP-2-functionalization have synergic enhancement on the ossification of hMSCs. These fabricated scaffolds can be used as promising candidates for bone tissue engineering applications.

Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation.

The nano-composites Fe3O4@SiO2@(-O3Si[(CH2)3NH])P([double bond, length as m-dash]O)(NH-R(+)CH(CH3)(C6H5))2 (Fe3O4@SiO2@PTA(+)) and Fe3O4@SiO2@(-O3Si[(CH2)3NH])P([double bond, length as m-dash]O)(NH-S(-)CH(CH3)(C6H5))2 (Fe3O4@SiO2@PTA(-)) were prepared and used for the chiral separation of five racemic mixtures (PTA = phosphoric triamide). The separation results show chiral recognition ability of these materials with respect to racemates belonging to different families of compounds (amine, acid, and amino-acid), which show their feasibility to be potential adsorbents in chiral separation. The nano-composites were characterized by FTIR, TEM, SEM, EDX, XRD, and VSM. The VSM curves of nano-composites indicate their superparamagnetic property, which is stable after their use in the separation process. Fe3O4, Fe3O4@SiO2, Fe3O4@SiO2@PTA(+) and Fe3O4@SiO2@PTA(-) are regularly spherical with uniform shape and the average sizes of 17-20, 18-23, 36-47 and 43-52 nm, respectively.

Biodegradable bead-on-spring nanofibers releasing ß-carotene for bone tissue engineering.

Bead-on-string mats based on poly(lactide-co-glycolide) (PLGA) releasing ß-carotene (ßC) as a natural osteogen were fabricated and used for bone tissue engineering. Mesenchymal stem cells (MSCs) seeded on the scaffolds successfully differentiated to osteoblasts without using any a differential medium. The mats showed a small burst of ß-carotene (24-27%) during the first day and a sustained slow release up to 21 days. The MTT and SEM results indicated good attachment and proliferation of MSCs on the scaffolds. Calcination of scaffolds and expression of RUNX2, SOX9, and osteonectin genes approved the differentiation of seeded MSCs to osteoblasts without using any external osteogenic differential agent. The scaffold loaded with 4% ß-carotene not only induced the early phase of osteogenesis but also advanced the differentiation to the osteoblast maturation phase. Thus, these bead-on-string scaffolds can be used as a substrate for direct bone tissue engineering.

ß-Carotene: a natural osteogen to fabricate osteoinductive electrospun scaffolds.

ß-Carotene (ßC) as a natural osteogenic material was incorporated in PCL electrospun mats to fabricate scaffolds for bone tissue engineering. These scaffolds successfully supported the attachment and proliferation of mesenchymal stem cells (MSCs). Seeded scaffolds were calcinated during 21 days of cell culture in a non-differential medium, which showed the osteodifferentiation of MSCs. Expression of RUNX2, SOX9, and osteonectin proved the osteoinductive effect of incorporated ß-carotene on the differentiation of MSCs to osteoblasts without using any external osteogenic differential agent. However, the cells did not pass the early phase of osteogenesis and were still osteochondro-progenitor after 21 days of incubation. Thus, the fabricated fibrous scaffolds are potential candidates for direct bone tissue engineering.

Correction: ß-Carotene: a natural osteogen to fabricate osteoinductive electrospun scaffolds.

[This corrects the article DOI: 10.1039/C7RA13237A.].

Polycaprolactone/carboxymethyl chitosan nanofibrous scaffolds for bone tissue engineering application.

This research focused on the physical properties and cell compatibility of nanofibrous scaffolds based on polycaprolactone/chitosan (PCL/CTS) and PCL/carboxymethyl chitosan (PCL/CMC) blends for bone tissue engineering application. Scaffolds were fabricated by electrospinning technique. SEM images showed that the undesirable ultrafine and splitting fibers in PCL/CTS scaffolds are eliminated by replacing CTS with CMC. PCL/CMC scaffolds exposed significantly improved surface hydrophilicity improvement comparing to PCL/CTS ones. The water contact angle of PCL scaffold was reduced on the addition of 15% CMC from 123 ±â€¯1° to 51 ±â€¯3° in high concentration of CMC scaffold. The average diameter of fibers in PCL/CTS 15% and PCL/CMC 15% were 439 and 356 nm, respectively, which demonstrated higher concentrations of CMC resulted in decrease fibers diameter than other blended scaffolds. FTIR spectroscopy confirmed the composition of PCL/CTS and PCL/CMC scaffolds. The culturing of human osteoblast cells (MG63) on the scaffolds showed that all scaffolds are biocompatible. The PCL/CMC nanofibers exhibited promoting proliferation trend, compared to the PCL and PCL/CTS ones, especially at maximum concentrations of CMC. The results demonstrate that the PCL/CMC electrospun scaffolds can be an excellent candidate for bone tissue engineering application.