Sonochemical synthesis of PVA/PVP blend nanocomposite containing modified CuO nanoparticles with vitamin B1 and their antibacterial activity against Staphylococcus aureus and Escherichia coli

The aim of this paper was to blend the polymers, poly(N-vinyl-2-pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) to produce a novel composite materials possessing the benefits of both. CuO nanoparticles (NPs) were used as a suitable filler to fabricate the blend nanocomposites (NCs) with desired properties. First, the surface of NPs, was modified with vitamin B₁ (VB₁) as a bio-safe coupling agent. Then, the blend NCs with various ratios of modified CuO (3, 5, and 7 wt%) were fabricated under ultrasonic irradiations followed by casting/solvent evaporation method. These processes are fast and green way to disperse the NPs sufficiently. Several techniques were applied for the characterization of the obtained NCs. morphology examination demonstrated the morphology of NCs and compatibility of NPs with the blend polymer. EDX results indicated the weight and atomic percentage of the achieved materials. TGA analysis verified that the NCs show higher thermal properties than the neat blend polymer. Also embedding the modified NPs into the blend polymer had effected on optical absorbance of the obtained NCs. The contact angle measurements confirmed that the hydrophilicity decreased for different proportions of the modified NPs loaded in the blend polymer. Finally, NCs show better bactericidal effects against gram-positive than gram-negative bacteria.

An epigenetic bioactive composite scaffold with well-aligned nanofibers for functional tendon tissue engineering

Poor tendon repair is often a clinical challenge due to the lack of ideal biomaterials. Electrospun aligned fibers, resembling the ultrastructure of tendon, have been previously reported to promote tenogenesis. However, the underlying mechanism is unclear and the aligned fibers alone are not capable enough to commit teno-differentiation of stem cells. Here, based on our observation of reduced expression of histone deacetylases (HDACs) in tendon stem/progenitor cells (TSPCs) cultured on aligned fibers, we proposed a strategy to enhance the tenogenesis effect of aligned fibers by using a small molecule Trichostatin A (TSA), an HDAC inhibitor. Such a TSA-laden poly (l-lactic acid) (PLLA) aligned fiber (A-TSA) scaffold was successfully fabricated by a stable jet electrospinning method, and demonstrated its sustained capability in releasing TSA. We found that TSA incorporated aligned fibers of PLLA had an additive effect in directing tenogenic differentiation. Moreover, the in situ implantation study in rat model further confirmed that A-TSA scaffold promoted the structural and mechanical properties of the regenerated Achilles tendon. This study demonstrated that HDAC was involved in the teno-differentiation with aligned fiber topography, and the combination of HDAC with aligned topography might be a more efficient strategy to promote tenogenesis of stem cells.

STATEMENT OF SIGNIFICANCE

Electrospun aligned fibers, resembling the ultrastructure of tendon, have been previously reported to promote tenogenesis. However, the underlying mechanism is unclear and the aligned fibers alone are not capable enough to commit teno-differentiation of stem cells. The uniqueness of our studies are as follows, based on our observation of reduced expression of histone deacetylases (HDACs) in tendon stem/progenitor cells (TSPCs) cultured on aligned fibers, we proposed a strategy to enhance the tenogenesis effect of aligned fibers by using a small molecule Trichostatin A (TSA), a HDAC inhibitor. Such a TSA-laden poly (l-lactic acid) (PLLA) aligned fiber (A-TSA) scaffold was successfully fabricated by a stable jet electrospinning method, and demonstrated its sustained capability in releasing TSA. The incorporation and subsequent release of bioactive small molecule TSA into electrospun aligned fibers allows a controllable manner for both biochemical and physical regulation of tenogenesis of stem cells both in vitro and in vivo. Collectively, the present study provides a model of "translating the biological knowledge learned from cell-material interaction into optimizing biomaterials (from Biomat-to-Biomat)".

Alkali-Mediated Miscibility of Gelatin/Polycaprolactone for Electrospinning Homogeneous Composite Nanofibers for Tissue Scaffolding

Electrospun natural-synthetic composite nanofibers, which possess favorable biological and mechanical properties, have gained widespread attention in tissue engineering. However, the development of biomimetic nanofibers of hybrids remains a huge challenge due to phase separation of the polymer blends. Here, aqueous sodium hydroxide (NaOH) solution is proposed to modulate the miscibility of a representative natural-synthetic hybrid of gelatin (GT) and polycaprolactone (PCL) for electrospinning homogeneous composite nanofibers. Alkali-doped GT/PCL solutions and nanofibers examined at macroscopic, microscopic, and internal molecular levels demonstrate appropriate miscibility of GT and PCL after introducing the alkali dopant. Particularly, homogeneous GT/PCL nanofibers with smooth surface and uniform diameter are obtained when aqueous NaOH solution with a concentration of 10 m is used. The fibers become more hydrophilic and possess improved mechanical properties both in dry and wet conditions. Moreover, biocompatibility experiments show that stem cells adhere to and proliferate better on the alkali-modified nanofibers than the untreated one. This study provides a facile and effective approach to solve the phase separation issue of the synthetic-natural hybrid GT/PCL and establishes a correlation of compositionally and morphologically homogeneous composite nanofibers with respect to cell responses.

Thermally flexible epoxy/cellulose blends mediated by an ionic liquid

Blends between the widely used thermoset resin, epoxy, and the most abundant organic material, natural cellulose are demonstrated for the first time.

Preparation and characterization of a transparent amorphous cellulose film

Amorphous cellulose film (ACF) was prepared from cellulose solution in lithium chloride (8 wt%)/N,N-dimethylacetamide by regeneration with acetone.

Miscibility Studies of Hydroxypropyl Cellulose/Poly(Ethylene Glycol) in Dilute Solutions and Solid State

The miscibility of Hydroxypropyl cellulose (HPC)/poly(ethylene glycol) (PEG) blends over an extended range of concentrations in water. The viscosity, ultrasonic velocity, and refractive index of the above blend solutions have been measured at 30°C. The interaction parameters such as and μ proposed by Chee and α proposed by Sun have been obtained using the viscosity data to probe the miscibility of the polymer blends. The values indicated that the blends were miscible when HPC content is more than 40% in the blend. The obtained results have been confirmed by the ultrasonic velocity and refractive index studies. The films of the blends were prepared by solution casting method using water as a solvent. The prepared films have been characterized by analytical techniques such as FTIR, DSC, X-RD, and SEM to probe the miscibility of HPC/PEG blends. The compatibility in the above compositions may be due to the formation of H-bonding between hydroxyl groups of HPC and etheric oxygen atom of PEG molecules.

Cellulose/polycaprolactone blends regenerated from ionic liquid 1-butyl-3-methylimidazolium chloride

Ionic liquid solvent, 1-butyl-3-methylimidazolium chloride (BMIM[Cl]) was used to prepare cellulose/polycaprolactone (PCL) blend films. This solvent was recycled with high yield and purity after blend precipitation. The inter- and intra-molecular hydrogen bonding interactions in these blends were investigated by Fourier transform infrared (FTIR) spectroscopy and it was found that a new peak in the carbonyl region, assigned to hydrogen bonding between carbonyl groups of PCL and hydroxyl groups of cellulose in blends with PCL composition less than 40 wt%. Differential scanning calorimetry (DSC) results implied a partial miscibility of the two components by melting point depression. Moreover, the tensile properties of the blends can be adjusted by incorporating various amounts of PCL into cellulose. The blends show significant enhancement of thermal stability compared to the regenerated cellulose when the content of PCL is higher than 40 wt%. This work demonstrates an effective approach for the processing biodegradable blends from natural and synthetic polymers.

Thermoresponsive semicrystalline poly(ε-caprolactone) networks: exploiting cross-linking with cinnamoyl moieties to design polymers with tunable shape memory

The overall goal of this study was to synthesize semicrystalline poly(ε-caprolactone) (PCL) copolymer networks with stimuli-responsive shape memory behavior. Herein, we investigate the influence of a cinnamoyl moiety to design shape memory polymer networks with tunable transition temperatures. The effect of various copolymer architectures (random or ABA triblock), the molecular weight of the crystalline domains, PCL diol, (M(w) 1250 or 2000 g mol(-1)) and its composition in the triblock (50 or 80 mol %) were also investigated. The polymer microstructures were confirmed by NMR, DSC, WAXS and UV-vis spectroscopic techniques. The thermal and mechanical properties and the cross-linking density of the networks were characterized by DSC, tensile testing and solvent swelling, respectively. Detailed thermomechanical investigations conducted using DMA showed that shape memory behavior was obtained only in the ABA triblock copolymers. The best shape memory fixity, R(f) of ~99% and shape recovery, R(r) of ~99% was obtained when PCL diol with M(w) 2000 g mol(-1) was incorporated in the triblock copolymer at a concentration of 50 mol %. The series of triblock copolymers with PCL at 50 mol % also showed mechanical properties with tunable shape memory transition temperatures, ranging from 54 °C to close to body temperature. Our work establishes a general design concept for inducing a shape memory effect into any semicrystalline polyester network. More specifically, it can be applied to systems which have the highest transition temperature closest to the application temperature. An advantage of our novel copolymers is their ability to be cross-linked with UV radiation without any initiator or chemical cross-linker. Possible applications are envisioned in the area of endovascular treatment of ischemic stroke and cerebrovascular aneurysms, and for femoral stents.