Ja Young Cheon

Antimicrobial Silver Chloride Nanoparticles Stabilized with Chitosan Oligomer for the Healing of Burns

Recently, numerous compounds have been studied in order to develop antibacterial agents, which can prevent colonized wounds from infection, and assist the wound healing. For this purpose, novel silver chloride nanoparticles stabilized with chitosan oligomer (CHI-AgCl NPs) were synthesized to investigate the influence of antibacterial chitosan oligomer (CHI) exerted by the silver chloride nanoparticles (AgCl NPs) on burn wound healing in a rat model. The CHI-AgCl NPs had a spherical morphology with a mean diameter of 42 ± 15 nm. The burn wound healing of CHI-AgCl NPs ointment was compared with untreated group, Vaseline ointment, and chitosan ointment group. The burn wound treated with CHI-AgCl NPs ointment was completely healed by 14 treatment days, and was similar to normal skin. Particularly, the regenerated collagen density became the highest in the CHI-AgCl NPs ointment group. The CHI-AgCl NPs ointment is considered a suitable healing agent for burn wounds, due to dual antibacterial activity of the AgCl NPs and CHI.

Formation of Ag Nanoparticles in PVA Solution and Catalytic Activity of Their Electrospun PVA Nanofibers

Ag nanoparticles (NPs) were prepared by chemical reduction based on green synthesis in an aqueous poly(vinyl alcohol) (PVA) solution with different temperatures and pHs. The PVA and maltose were used as stabilizing and reducing agents, respectively. Silver nitrate (AgNO3) precursor for Ag NPs was also used by 1 wt% on the base of the weight of PVA. The formation of Ag NPs was examined by UV-Vis spectrophotometer, and their size was measured by transmission electron microscopy (TEM), and nanoparticle size analyzer (NPSA). The formation rate of Ag NPs in the PVA solution increased with increasing temperature and pH, whereas the size of Ag NPs stabilized with PVA increased with increasing temperature, or with decreasing pH. Subsequently, the PVA nanofibrous matrix containing Ag NPs was prepared, by electrospinning PVA solution with Ag NPs, and followed by heat treatment. The morphology and crystalline structure of PVA nanofibers with Ag NPs was observed with field emission scanning electron microscopy (FE-SEM), and X-ray diffractometer (XRD), respectively. From the degradation reaction of methylene blue (MB) using PVA nanofibers web and film, it was found that the catalytic activity of PVA matrices with Ag NPs was strongly dependent on the surface area of the PVA matrices.

Fabrication and characterization of cellulose acetate/montmorillonite composite nanofibers by electrospinning

Nanofibers composed of cellulose acetate (CA) and montmorillonite (MMT) were prepared by electrospinning method. MMT was first dispersed in water and mixed with an acetic acid solution of CA. The viscosity and conductivity of the CA/MMT solutions with different MMT contents were measured to compare with those of the CA solution. The CA/MMT solutions were electrospun to fabricate the CA/MMT composite nanofibers. The morphology, thermal stability, and crystalline and mechanical properties of the composite nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and tensile test. The average diameters of the CA/MMT composite nanofibers obtained by electrospinning 18 wt% CA/MMT solutions in a mixed acetic acid/water (75/25, w/w) solvent ranged from 150∼350 nm. The nanofiber diameter decreased with increasing MMT content. TEM indicated the coexistence of CA nanofibers. The CA/MMT composite nanofibers showed improved tensile strength compared to the CA nanofiber due to the physical protective barriers of the silicate clay layers. MMT could be incorporated into the CA nanofibers resulting in about 400% improvement in tensile strength for the CA sample containing 5 wt% MMT.

Small diameter vascular graft with fibroblast cells and electrospun poly (L-lactide-co-ε-caprolactone) scaffolds: Cell Matrix Engineering

Abstract Electrospun scaffolds have been widely used in tissue engineering due to their similar structure to native extracellular matrices (ECM). However, one of the obstacles limiting the application of electrospun scaffolds for tissue engineering is the nano-sized pores, which inhibit cell infiltration into the scaffolds. To overcome this limitation, we approached to make layers which are consisted of cells onto the electrospun sheet and then tubular structure was constructed by rolling. We called this as ‘Cell Matrix Engineering’ because the electrospun sheets were combined with the cells to form one matrix. They maintained 3-D tubular structures well and their diameters were 4.1 mm (±0.1 mm). We compared the mechanical and biological properties of various vascular grafts with the electrospun PLCL sheets of different thickness. In these experiments, the vascular graft made with thin sheets showed a better cell proliferation and attachment than the grafts made with thick sheets because the thin layer allowed for more efficient mass transfer and better permeability than the thick layer. Culturing under physiological pulsatile flow condition was demonstrated in this work. These dynamic conditions provided the improved mass transport and aerobic cell metabolism. Therefore, the Cell Matrix Engineered vascular graft holds a great promise for clinical applications by overcoming the limitations associated with conventional scaffolds.

Formation of Silver Nanoparticles Using Fluorescence Properties of Chitosan Oligomers

In this study, silver chloride nanoparticles (AgCl NPs) were prepared using chitosan oligomer (CHI) and chitosan oligomer derivatives (CHI-FITC). The CHI and CHI-FITC were used as markers to confirm the formation of AgCl NPs using their fluorescence properties as well as stabilizers. The fluorescence properties of CHI and CHI-FITC were monitored by a luminescence spectrophotometer, and the morphology of the AgCl NPs was further confirmed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The fluorescence of CHI and CHI-FITC was quenched by the formation of AgCl NPs, and the Stern–Volmer equation was used to compare the two types of stabilizer. The CHI and CHI-FITC stabilizer were linear and nonlinear, respectively, with respect to the Stern–Volmer equation, and considered to be usable as fluorescence indicators to confirm the formation behavior of AgCl NPs through fluorescence quenching.

Effect of solution pH on the self-polymerization behavior of 3,4-Dihydroxyphenylalanine

Abstract