Poly Ethylene Glycol Dimethacrylate Research Articles

Effect of an additive on the permanent memory effect of polymer dispersed liquid crystal films

BACKGROUND Polymer dispersed liquid crystal (PDLC) films have a range of applications varying from switchable windows to new optical memory devices. They switch from an opaque state, when liquid crystal molecules are randomly dispersed, to a transparent state, when liquid crystal molecules are aligned, simply by applying a small voltage. On some PDLC films, the transparent state is retained even when the voltage is switched off; this is called permanent memory effect (PME). This process is totally reversible, returning to the initial opaque state either through heating or applying a higher frequency electric field when using a two frequency liquid crystal. RESULTS In this work, the impact on the electro-optical response of PDLC films as a result of adding an additive was studied. This performance is affected by several factors, the most important being the anchorage force. This anchorage force is modified with the addition of an additive such as TX-100. As a result, it was verified that the addition of TX-100, increased the PME up to 98.7% and decreased the voltage required to achieve 90% of maximum transmittance to 2 V µm−1. CONCLUSIONS The addition of a surfactant, as TX-100 in this case, was shown to be a valuable method to control the PME in PDLC systems in particular those prepared by PIPS from the oligomer polyethylene glycol dimethacrylate and the monomer triethylene glycol dimethacrylate in mixture with the nematic LC E7. This new advance on liquid crystal field also allows development of a new memory device based on a write–read–erase cycle. © 2015 Society of Chemical Industry

Enhancement of endothelial differentiation of adipose derived mesenchymal stem cells by a three-dimensional culture system of microwell

Adipose derived mesenchymal stem cells (AdMSCs) have been demonstrated to have ability to differentiate into several cell lineages, including endothelial cells. The low endothelial differentiation efficiency, however, limits further clinical application of AdMSCs for therapeutic angiogenesis. This study was designed to investigate the feasibility to promote endothelial differentiation efficacy of AdMSCs using microwell array as a 3-D culture system. AdMSCs aggregates were prepared using photocrosslinkable polyethylene glycol dimethacrylate (PEGDM) derived microwell. AdMSCs aggregated and formed well defined 3-D aggregates following seeding. The microwell was effective in regulating the size of AdMSCs aggregates with low variation. AdMSCs within the 3-D aggregates maintained the cell surface epitopes of AdMSCs with high viability. Endothelial growth medium was used to induce the in vitro endothelial differentiation of AdMSCs. Both gene expression results from real time PCR and protein expression data from immunofluorescent staining revealed that 3-D cultured aggregates significantly promote the endothelial differentiation efficacy of AdMSCs. AdMSCs or AdMSCs aggregates were injected into the subcutaneous space of nu/nu mice to investigate the endothelial differentiation in vivo. The immunofluorescent staining data indicated promoted endothelial differentiation of 3-D aggregates compared with 2-D AdMSCs. Aggregates dissociated cells were obtained by transferring 3-D aggregates onto the adherent surfaces. Cells dissociated from induced aggregates were still positive for endothelial specific markers and were able to form endothelial-like tube structures on matrigel, indicating the endothelial properties. We conclude that microwell is an ideal 3-D culture system for promoting endothelial differentiation efficacy of AdMSCs.

Gelation and crosslinking characteristics of photopolymerized poly(ethylene glycol) hydrogels

ABSTRACTThe gelation and crosslinking features of poly(ethylene glycol) (PEG) hydrogels were scrutinized through the UV polymerization processes of poly(ethylene glycol) methacrylate (PEGMA) and poly(ethylene glycol) dimethacrylate (PEGDMA) mixtures. The real‐time evolutions of the elastic moduli of the prepolymerized mixtures with different crosslinking ratios of PEGMA and PEGDMA and the photoinitiator concentrations were measured during photopolymerization. The rheological properties were compared with other properties of the PEG hydrogels, including the relative changes in the CC amounts in the mixtures before and after UV irradiation, water swelling ratio, gel fraction, mesh size, and mechanical hardness. As the portion of PEGDMA as a crosslinker increased, the final elastic modulus and gel fraction increased, whereas the swelling ratio and scratch penetration depth at the hydrogel film surface decreased because of the formation of compact networks inside the hydrogels. These results indicate that there was a good correlation between the rheological analysis for predicting the crosslinking transition during photopolymerization and the macroscopic properties of the crosslinked hydrogels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41939.

The effect of organoclay addition on the properties of an acrylate based, thermally activated shape memory polymer

Shape Memory Polymers (SMPs) exhibit the intriguing ability to change back from an intermediate, deformed shape back to their original, permanent shape. In this contribution a systematic series of t-butylacrylate-co-poly(ethyleneglycol) dimethacrylate (tBA-co-PEGDMA) polymers have been synthesised and characterised prior to incorporation of organoclay. Increasing the poly(ethyleneglycol) dimethacrylate (PEGDMA) content in increments of 10% increased the storage modulus from 2005 to 2250MPa, reduced the glass transition temperature from +41 to −26°C and reduced the intensity of the associated tan δ peak. The tBA-co-PEGDMA crosslinked networks displayed useful shape memory properties up to PEGDMA contents of 40%. Above this PEGDMA percentage the materials were prone to fracture and too brittle for a realistic assessment of their shape memory capability. The system containing 90% t-butylacrylate (tBA) and 10% PEGDMA was selected as the host matrix to investigate how the incorporation of 1 to 5mass% of a benzyl tallow dimethylammonium-exchanged bentonite (BTDB) influenced the shape memory properties. X-ray diffraction data confirmed that BTDB formed a microcomposite in the selected matrix and exerted no influence on the storage modulus, rubbery modulus, glass transition temperature, Tg, or the shape or intensity of the tan δ peak of the host matrix. Therefore, it was anticipated that the presence of BTDB would have no effect, positive or negative, nor on the shape memory properties of the host matrix. However, it was found that the incorporation of clay, especially at the 1mass% level, significantly accelerated the speed, compared with the clay-free SMP, at which the microcomposite returned to the original, permanent shape. This accelerated return to the permanent shape was also observed when the microcomposite was coated onto a 100μm PET film.

New application of scanning electrochemical microscopy incharac-terization of hydrogel microwell arrays

Hydrogel microwell arrays are new soft substrates for cell cultivation. The microwell morphology has direct influence on the behavior of cells cultured within microwells. But the conventional morphology characterization techniques of hydrogel microwell arrays can not in situ characterize hydrogel microwell arrays in aqueous solution and also not in a reversible way. Using the oxygen dissolved in water as the redox mediator, scanning electrochemical microscopy (SECM) was applied to in situ characterize the morphology of microwell array made of polyethylene glycol dimethacrylate (PEGDMA) hydrogel in aqueous solution. Both the two-dimensional and three-dimensional surface morphology images of PEGDMA microwell arrays were obtained. This work demonstrates that SECM is a new method of in situ characterization of hydrogel microwell arrays in a non-destructive and reversible way with providing three-dimensional surface morphology information.

Polymer length scale on modification of a reverse microemulsion

We study water-in-oil microemulsions, in certain the diffusion of water droplets covered with a monolayer of the anionic surfactant docusate sodium in a phase of n-decane mixed with the polyethylene glycol dimethacrylate (PEGD). At constant droplet size we vary the polymer concentration and from structural investigations with small-angle X-ray scattering there was clear evidence for penetration in the droplets. We apply this technique to monitor the size and morphology of the mixture system (docusate sodium microemulsion/PEGD). The structural study of our samples shows spherical-to-cylindrical change in nanodroplets with increase in polymer concentration. The dynamics of system consists of the translation diffusion of the nanodroplets was studied with dynamic light scattering.

Injectable and photocross-linkable gels based on gellan gum methacrylate: A new tool for biomedical application

In this work, a natural polysaccharide gellan gum (GG) has been modified with methacrylic groups (GG-MA) and combined with polyethylene glycol dimethacrylate (PEG-DMA) in order to create novel injectable hydrogels that can be easily delivered through a needle and photocross-linked in the injection site. A novel synthetic procedure for methacrylation of GG has been proposed to better control its derivatization. Different degrees of functionalization have been achieved and their effects on the solubility and mechanical properties of GG-MA were investigated. A good balance in terms of hydrophilicity and elasticity of the corresponding hydrogels was identified, although not suitable enough as injectable material for the treatment of damaged soft tissues. For this reason, several concentrations and different molecular weights of PEG-DMA were investigated to modulate the composition of GG-MA hydrogels and overcome their extreme fragility. Swelling abilities of the hydrogels in different media were studied as a key parameter able to affect the release profile of loaded therapeutic agents. Model molecules having different spherical hindrance (sulindac and vitamin B12) were then chosen to study how the hydrogels were able to modulate their diffusion profiles over time. Finally, the hydrogel's safety was evaluated trough an MTT cytotoxicity test on human fibroblasts.

Novel bio‐based IPNs obtained by simultaneous thermal polymerization of flexible methacrylate network based on a vegetable oil and a rigid epoxy

A series of novel vegetable oil‐based interpenetrating polymer networks (IPNs) have been successfully prepared: on one hand, methacrylated camelina oil (MCO) and a polyethyleneglycol dimethacrylate (PEG, MW 750 g/mol) and on the other hand, diglycidylether of bisphenol A (DER), in various blend ratios (75/25, 50/50, and 25/75 wt). Hence the appealing innovative direction of the current work was to build oil‐based poly(methacrylate) network using PEG macromonomer which is able to modulate adequately the crosslinking degree of the oil‐based network.These innovative combinations of cross‐linkable resins in terms of flexible methacrylate network based on camelina oil (CO) and PEG and a rigid epoxy (DER) were simultaneously polymerized using two independent non‐interfering curing reactions: free‐radical process for MCO and anionic polymerization of epoxy resin in the presence of a tertiary amine. The effect of the IPNs composition compositional characteristics on the reactivity of methacrylate or epoxy groups was studied using differential scanning calorimetry. The influence of the MCO‐PEG bio‐based polymer on the system properties was evaluated after curing by dynamic mechanical and thermogravimetric analyses. In addition mechanical and morphological studies were also carried out. The results suggested that blending of MCO and DER gave synergistic effects on the overall properties of the developed oil‐based IPNs and a dependence on the methacrylate/epoxy ratio was clearly noticed. Copyright © 2014 John Wiley & Sons, Ltd.

Polyelectrolytes exceeding ITO flexibility in electrochromic devices

Utilizing the in situ method, we report the fabrication of flexible electrochromic (EC) devices in a one-step lamination procedure. In this study, electrochromic device performance was enhanced via the use of new gel polymer electrolyte (GPE) materials based on poly(ethylene glycol) (PEG) derivatives. PEG serves as the polymer matrix in electrochromic devices (ECDs) that provides not only mechanical stability, but also a wide potential window and compatibility with a variety of salts. Poly(ethylene glycol) dimethacrylate (PEGDMA) in conjunction with poly(ethylene glycol) methyl ether acrylate (PEGMA), containing lithium trifluoromethanesulfonate (LiTRIF) as the salt and propylene carbonate (PC) as a plasticizer; we investigated various electrolyte parameters, including salt loading, the mono/di-functional PEG ratio, and the plasticizer to PEG ratio. Optimized gel systems exceed the mechanical flexibility of indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates in their sustainable minimum bending radius of curvature, exhibit an ionic conductivity up to 1.36 × 10−3 S cm−1, and yield electrochromic devices (ECDs) with photopic contrasts as high as 53% (without background correction) using poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) as the standard electrochromic material. In addition to ionic conductivity, the crosslink density of the GPEs was found to have an important effect on the photopic contrast of the resultant ECDs. Using these results, 110 cm2 flexible patterned EC displays were assembled as a demonstration of their potential in real world applications.

Poly(ethylene glycol) dicarboxylate/poly(ethylene oxide) hydrogel film co-crosslinked by electron beam irradiation as an anti-adhesion barrier.

The cross-linked poly(ethylene glycol) dicarboxylate (PEGDC)/poly(ethylene oxide) (PEO) and poly(ethylene glycol) dimethacrylate (PEGDMA)/(PEO) hydrogels were developed for possible biomedical applications such as an anti-adhesion barrier. Various contents of PEGDC/PEO film were irradiated using an electron beam with various beam intensities in order to obtain various degrees of crosslinked hydrogels. The optimum dose (300 kGy) and total crosslinker content of 10% were used to prepare crosslinked hydrogel films with three different compositions (10% PEGDC, 10% PEGDMA, 5% PEGDC-5% PEGDMA). Among them, 10% PEGDC hydrogel film exhibited the highest elongation at break (69.33±6.87%) with high mechanical strength. 10% PEGDC hydrogel film showed the lowest hemolysis activity (6.03±0.01%) and the highest tissue adherence (75.67±1.15 cN). The result also indicated that the carboxyl groups in PEGDC affect the tissue adherence of hydrogel films via H-bonding interactions. In animal studies, 10% PEGDC anti-adhesion hydrogel film degraded within 3 weeks and demonstrated better anti-adhesive effect compared to Guardix-SG®.

Synthesis and Characterization of Polyethylene Glycol Dimethacrylate Hydrogels for Biomedical Application

Photo-polymerized polyethylene glycol dimethacrylate (PEGDMA) scaffolds were synthesized using two macromolecular monomers of 750 and 550 number average molecular weight. Variation in chain length of macromolecular monomers visibly influenced viscoelastic properties of the compositions, exhibiting an increase in shear storage and loss modulus in PEGDMA 750 hydrogels. Furthermore, water content in the pre-polymerization mixture was a main factor determining physical appearance of the samples, where increase in water content resulted in polymerization induced phase separation, demonstrated by opaqueness of preparations containing 60 and 75% (w/w) of H2O. In addition to this, swelling, gel fraction, compression and rheological measurements are found to be influenced by the amount of water incorporated in the hydrogels, resulting in the increased distance between polymer chains within the network. Furthermore this resulted in an apparent decrease in viscoelastic and mechanical properties of compositions, as well as in lowering their crosslinking density and compressive strength. Preliminary cytotoxicity results show no toxicity of the samples with approximately 80% cell viability after 24 h exposure of MC3T3-E1 Subclone 4 cells to the hydrogels, thus indicating that these materials could be potentially applied in the biomedical arena.

Bioactive nanoparticles stimulate bone tissue formation in bioprinted three‐dimensional scaffold and human mesenchymal stem cells

Bioprinting based on thermal inkjet printing is a promising but unexplored approach in bone tissue engineering. Appropriate cell types and suitable biomaterial scaffolds are two critical factors to generate successful bioprinted tissue. This study was undertaken in order to evaluate bioactive ceramic nanoparticles in stimulating osteogenesis of printed bone marrow-derived human mesenchymal stem cells (hMSCs) in poly(ethylene glycol)dimethacrylate (PEGDMA) scaffold. hMSCs suspended in PEGDMA were co-printed with nanoparticles of bioactive glass (BG) and hydroxyapatite (HA) under simultaneous polymerization so the printed substrates were delivered with highly accurate placement in three-dimensional (3D) locations. hMSCs interacted with HA showed the highest cell viability (86.62 ± 6.02%) and increased compressive modulus (358.91 ± 48.05 kPa) after 21 days in culture among all groups. Biochemical analysis showed the most collagen production and highest alkaline phosphatase activity in PEG-HA group, which is consistent with gene expression determined by quantitative PCR. Masson's trichrome staining also showed the most collagen deposition in PEG-HA scaffold. Therefore, HA is more effective comparing to BG for hMSCs osteogenesis in bioprinted bone constructs. Combining with our previous experience in vasculature, cartilage, and muscle bioprinting, this technology demonstrates the capacity for both soft and hard tissue engineering with biomimetic structures.

Synthesis and photopolymerisation of maleic polyvinyl alcohol based hydrogels for bone tissue engineering

The novel synthesis of photopolymerisable polyvinyl alcohol (PVA) was achieved by reacting maleic anhydride with the hydroxyl groups of PVA. The incorporation of photopolymerisable double bonds onto the PVA polymeric chain was confirmed by both 1H NMR and 13C NMR spectroscopy. Hydrogel blends were prepared by mixing maleic PVA and polyethylene glycol dimethacrylate (PEGDMA) precursors at different concentrations and molecular weights. It was observed that the increase in crosslinking with the introduction of maleic PVA crosslinks resulted in higher compressive properties and storage modulus values. These values fall below those reported for bone; however, if these scaffolds were used in conjunction with fixation devices and with the sustained release of dexamethasone it would allow for faster regeneration of bone defects. Drug release results showed that the release profile of the hydrogels was between 11 and 16 days. This was as a result of altering the swelling and pore sizes of the hydrogels by varying the precursor concentrations. Preliminary in vitro cytotoxicity evaluations were performed using the MTT assay as an end point, showing that these novel hydrogels are non-toxic to mouse embryonic fibroblast cell line.

Fabrication of microporous chitosan/silk fibroin as a scaffold material using electron beam

The aim of this study is to develop microporous material from silk fibroin (SF) and chitosan (CS) using electron beam-induced crosslinking technique. Poly(ethylene glycol) dimethacrylate (PEGDMA) was used as radiation crosslinking agent. Comparative studies were done using two different polymeric components, i.e., CS and CS/SF. An effect of irradiation dose on crosslinking density and swelling degree were investigated. The chemical structure and packing conformation of the obtained microporous materials were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. The morphology and microstructure were assessed using scanning electron microscope (SEM). The PEGDMA crosslinked in a CS/SF system (CS-PEGDMA-SF) possessed greater inter-connected porous network than that in a single CS component (CS-PEGDMA). The gel fraction was ranging from 90% to 100% when the irradiation doses of 10–80 kGy were carried out. The swelling degree increased by means of gel fraction and irradiation dose. The pore size CS-PEGDMA-SF and CS-PEGDMA varied in the range of 0.80–1.35 μm and 8.07–16.32 μm, respectively depending on the irradiation doses. The fabricated scaffolds showed the porosity ranging from 21% to 94%. Taken together, CS-PEGDMA-SF microporous material from electron-beam irradiation would serve as a good promising scaffold for tissue engineering. Open image in new window

Enhanced chondrogenic differentiation of dental pulp stem cells using nanopatterned PEG-GelMA-HA hydrogels.

We have examined the effects of surface nanotopography and hyaluronic acid (HA) on in vitro chondrogenesis of dental pulp stem cells (DPSCs). Ultraviolet-assisted capillary force lithography was employed to fabricate well-defined nanostructured scaffolds of composite PEG-GelMA-HA hydrogels that consist of poly(ethylene glycol) dimethacrylate (PEGDMA), methacrylated gelatin (GelMA), and HA. Using this microengineered platform, we first demonstrated that DPSCs formed three-dimensional spheroids, which provide an appropriate environment for in vitro chondrogenic differentiation. We also found that DPSCs cultured on nanopatterned PEG-GelMA-HA scaffolds showed a significant upregulation of the chondrogenic gene markers (Sox9, Alkaline phosphatase, Aggrecan, Procollagen type II, and Procollagen type X), while downregulating the pluripotent stem cell gene, Nanog, and epithelial-mesenchymal genes (Twist, Snail, Slug) compared with tissue culture polystyrene-cultured DPSCs. Immunocytochemistry showed more extensive deposition of collagen type II in DPSCs cultured on the nanopatterned PEG-GelMA-HA scaffolds. These findings suggest that nanotopography and HA provide important cues for promoting chondrogenic differentiation of DPSCs.

Microcontact-BSA imprinted capacitive biosensor for real-time, sensitive and selective detection of BSA

An analytical method is presented, combining novel microcontact imprinting technique and capacitive biosensor technology for the detection of BSA. Glass cover slips were used for preparation of protein stamps. The microcontact-BSA imprinted gold electrodes were prepared in the presence of methacrylic acid (MAA) and poly-ethylene glycol dimethacrylate (PEGDMA) as the cross-linker by bringing the protein stamp and the gold electrode into contact under UV-polymerization. Real-time BSA detection studies were performed in the concentration range of 1.0×10−20–1.0×10−8M with a limit of detection (LOD) of 1.0×10−19M. Cross-reactivity towards HSA and IgG were 5 and 3%, respectively. The electrodes were used for >70 assays during 2 months and retained their binding properties during all that time. The NIP (non-imprinted) electrode was used as a reference. The microcontact imprinting technology combined with the biosensor applications is a promising technology for future applications.

Adsorption of Au(III) ions from aqueous solutions by thiol-ene photoclick hydrogels and its application to electronic waste and geothermal water

This work describes the preparation and characterization of a new thiol-ene hydrogel by photoinitiated polymerization of pentaerythritoltetrakis(3-mercaptopropionate) (Penta3MP4), acrylic acid (AAc) and poly(ethylene glycol) dimethacrylate (PEGDA) as monomers and photo initiator(2,2-dimethoxy-2-phenylacetophenon) for its use as adsorbent. The thiol-ene hydrogel was characterized by using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Real-Time Fourier Transform Infrared Spectroscopy (RT-FTIR), Scanning Electron Microscopy (SEM), Thermal Gravimetric Analyze (TGA) techniques; the swelling behavior and gelation ratio of hydrogel were also investigated. The adsorption capability of the hydrogel against Au(III) ions was investigated. The effects of pH, agitation time, initial metal ion concentration and different metal ions on adsorption capacity were examined. Equilibrium studies have been carried out to determine the capacity of the hydrogel for adsorption of Au(III) ions, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherms constants. Equilibrium data were found to fit very well with Langmuir model. The reusability of the hydrogel was also investigated and the preconcentration factor of the hydrogel was determined. The proposed method was applied to Dikili Geothermal Water and computer circuit board scrap. The analytical performance of the method was also determined.

Increasing the repeating units of ethylene glycol-based dimethacrylates directed toward reduced oxidative stress and co-stimulatory factors expression in human monocytic cells.

The ethylene glycol-based dimethacrylates are commonly used in biomaterials and dental restorative materials as a cross-linking agent. In this study, toxic effect of triethylene glycol dimethacrylate (TEGDMA) and poly(ethylene glycol) dimethacrylates (PEG-DMAs) with various ethylene glycol repeating units was investigated in terms of cytotoxicity, oxidative stress, and the expression of co-stimulatory factors in human leukemia cell line (THP-1 cells) to verify the effect of ethylene glycol repeating units. Note that the 1-octanol/water partition coefficient of PEG-based dimethacrylates decreased with increasing the ethylene glycol repeating units, indicating that the hydrophilicity of PEG-DMAs increased with ethylene glycol repeating units. The toxic effect of PEG-DMAs such as cytotoxicity, oxidative stress, and the expression of CD86 in treated THP-1 cells are reduced with increasing the ethylene glycol repeating units in PEG-DMAs. However, the expression of CD54 in treated THP-1 cells was not influenced with the ethylene glycol repeating units and the maximal expression level of CD54 was observed at the concentration range of 2-4 mM for all samples. Accordingly, hydrophilic character of PEG-DMAs with long ethylene glycol chains definitely alleviates the some toxic aspect of PEG-based DMAs. This finding would provide important insight into the design of new biomaterials and dental materials with superior biocompatibility.

Sustained delivery of MGF peptide from microrods attracts stem cells and reduces apoptosis of myocytes.

Local release of drugs may have many advantages for tissue repair but also presents major challenges. Bioengineering approaches allow microstructures to be fabricated that contain bioactive peptides for sustained local delivery. Heart tissue damage is associated with local increases in mechano growth factor (MGF), a member of the IGF-1 family. The E domain of MGF peptide is anti-apoptotic and a stem cell homing factor. The objectives of this study were to fabricate a microrod delivery device of poly (ethylene glycol) dimethacrylate (PEGDMA) hydrogel loaded with MGF peptide and to determine the elution profile and bioactivity of MGF. The injectable microrods are 30 kPa stiffness and 15μm widths by 100μm lengths, chosen to match heart stiffness and myocyte size. Successful encapsulation of native MGF peptide within microrods was achieved with delivery of MGF for 2weeks, as measured by HPLC. Migration of human mesenchymal stem cells (hMSCs) increased with MGF microrod treatment (1.72 ± 0.23, p < 0.05). Inhibition of the apoptotic pathway in neonatal rat ventricular myocytes was induced by 8h of hypoxia (1% O2). Protection from apoptosis by MGF microrod treatment was shown by the TUNEL assay and increased Bcl-2 expression (2 ± 0.19, p < 0.05). Microrods without MGF regulated the cytoskeleton, adhesion, and proliferation of hMSCs, and MGF had no effect on these properties. Therefore, the combination microdevice provided both the mechanical cues and 2-week MGF bioactivity to reduce apoptosis and recruit stem cells, suggesting potential use of MGF microrods for cardiac regeneration therapy in vivo.

Fabrication and characterization of anisotropic nanofiber scaffolds for advanced drug delivery systems.

Stimuli-responsive, polymer-based nanostructures with anisotropic compartments are of great interest as advanced materials because they are capable of switching their shape via environmentally-triggered conformational changes, while maintaining discrete compartments. In this study, a new class of stimuli-responsive, anisotropic nanofiber scaffolds with physically and chemically distinct compartments was prepared via electrohydrodynamic cojetting with side-by-side needle geometry. These nanofibers have a thermally responsive, physically-crosslinked compartment, and a chemically-crosslinked compartment at the nanoscale. The thermally responsive compartment is composed of physically crosslinkable poly(N-isopropylacrylamide) poly(NIPAM) copolymers, and poly(NIPAM-co-stearyl acrylate) poly(NIPAM-co-SA), while the thermally-unresponsive compartment is composed of polyethylene glycol dimethacrylates. The two distinct compartments were physically crosslinked by the hydrophobic interaction of the stearyl chains of poly(NIPAM-co-SA) or chemically stabilized via ultraviolet irradiation, and were swollen in physiologically relevant buffers due to their hydrophilic polymer networks. Bicompartmental nanofibers with the physically-crosslinked network of the poly(NIPAM-co-SA) compartment showed a thermally-triggered shape change due to thermally-induced aggregation of poly(NIPAM-co-SA). Furthermore, when bovine serum albumin and dexamethasone phosphate were separately loaded into each compartment, the bicompartmental nanofibers with anisotropic actuation exhibited decoupled, controlled release profiles of both drugs in response to a temperature. A new class of multicompartmental nanofibers could be useful for advanced nanofiber scaffolds with two or more drugs released with different kinetics in response to environmental stimuli.