Electrospun Poly(γ–glutamic acid)/β–Tricalcium Phosphate Composite Fibrous Mats for Bone Regeneration

[[abstract]]A poly(γ–glutamic acid)/β–tricalcium phosphate (γ–PGA/β–TCP) composite fibrous mat was fabricated using the electrospinning technique as a novel bone substitute. The mat was then cross-linked with cystamine in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide to improve its water-resistant ability. Scanning electron micrographs revealed that the γ–PGA/β–TCP fibers had a uniform morphology with diameters ranging from 0.64 ± 0.07 µm to 1.65 ± 0.16 µm. The average diameter of the fibers increased with increasing cross-linking time. Moreover, increasing the cross-linking time and decreasing the γ–PGA/β–TCP weight ratio decreased the swelling ratio and in vitro degradation rate of the composite fibrous mat. In vitro experiments with osteoblast-like MG-63 cells demonstrated that the mat with a γ–PGA/β–TCP weight ratio of 20 and cross-linked time of 24 h had a higher alkaline phosphatase activity and better cell adhesion. Furthermore, the rat cranial bone defect was created and treated with the γ–PGA/β–TCP composite fibrous mat to evaluate its potential in bone regeneration. After 8 weeks of implantation, micro computed tomography showed that the γ–PGA/β–TCP composite fibrous mat promoted new bone growth. These observations suggest that the γ–PGA/β–TCP composite fibrous mat has a potential application in bone tissue engineering

Three-dimensional dose comparison of flattening filter (FF) and flattening filter-free (FFF) radiation therapy by using NIPAM gel dosimetry

[[abstract]]Intensity-modulated radiotherapy and volumetric modulated arc therapy are modern radiation therapy technologies that can create the desired dose distribution by multileaf collimator movement and dose-rate control. However, the homogeneous dose delivery of small-field irradiation techniques shows disagreement with that of treatment planning system. The removal of the flattening filter by flattening filter free (FFF) beam irradiation increases dose conformity and further reduces treatment delivery time in radiosurgery. This study aims to investigate the dose distribution of FFF and flattened beams for small-field irradiation by using the 3D gel dosimeter. The N-isopropylacrylamide (NIPAM) polymer gel dosimeter was employed to record the 3D dose distribution. In addition, flattened and FFF beams were compared using the gamma evaluation technique. The use of an FFF accelerator resulted in excellent radiation treatments with short delivery times and low doses to normal tissues and organs. Results also showed that the passing rate increased with the decrease of field size (30 × 30, 20 × 20, and 10 × 10 mm2) at post-irradiation times of 24, 48, 72, and 96 h. The passing rates for each field size were retained at the same level when gamma criteria, namely, distance-to-agreement (DTA) = 3 mm/dose difference (DD) = 3%, were used. Nevertheless, the passing rates for each field size decreased slowly after 48 h when DTA = 2 mm/DD = 2%. The Wilcoxon signed-rank test was used to determine statistical difference with a significant level of p < 0.05. The passing rates of flattened and FFF beams showed no significant difference. The edge enhancement effect in the flattened beam was more evident than in the FFF beam. The 3D NIPAM gel dosimeter can be used for dose verification of small field for radiation therapy with high dose rate

Lithospermi radix Extract-Containing Bilayer Nanofiber Scaffold for Promoting Wound Healing in a Rat Model

[[abstract]]This study examined the in vitro characteristics and in vivo wound healing effect of novel Lithospermi radix (LR) extract-containing bilayer scaffolds in a rat model. LR extract, which has been used as a traditional herbal medicine for treating skin wounds, was added to a biocompatible gelatin solution. After glutaraldehyde vapor was used to modify the surface of chitosan scaffolds, various ratios of mammalian gelatin and fish collagen (GF100, GF91 and GF82) were electrospun onto the chitosan scaffolds to manufacture bilayer scaffolds. The porous chitosan scaffolds with a high swelling ratio showed efficient exudate absorption ability. GF91 gelatin nanofibers electrospun at a constant flow rate at 0.1 mL/h and a voltage of 20 kV displayed the optimal characteristics required for cell attachment and skin tissue regeneration. Moreover, the LR extract was successfully released slowly from the GF91 nanofibers. The investigation of the wound-healing activity of the chitosan/gelatin (CGF) bilayer scaffolds revealed that CGF91L provided the highest wound recovery rate in vivo in Sprague-Dawley (SD) rats. Based on its wound-healing effect and beneficial characteristics, the novel LR extract-containing CGF91 bilayer scaffold demonstrates potential as a material for treating skin wounds

Effect of genipin crossliked chitosan scaffolds containing SDF-1 on wound healing in a rat model

[[abstract]]Prolonged healing is a severe problem for elderly and diabetic patients. Impaired angiogenesis, stem cell differentiation, and migration have been shown to delay wound healing. The chemokine stromal cell-derived factor-1 (SDF-1) plays an essential role in recruiting cells to wound sites and is suggested to be a candidate for tissue engineering. In this study, chitosan (CHI) scaffolds were crosslinked with nontoxic genipin (Gp) and further heparinized for SDF-1 immobilization. Then, the structures were evaluated for their physicochemical properties (porosity, swelling ratio, and water vapor transmission rate (WVTR)). The interaction between SDF-1 and heparin could sustain SDF-1 release, which has been shown to enhance human umbilical vein endothelial cell (HUVEC) 2D/3D migration. The investigation of the wound-healing activity of the SDF-1-loaded CHI scaffolds revealed a better wound recovery rate in vivo in healthy and streptozotocin-induced diabetic Sprague-Dawley (SD) rats. The histological analysis illustrated that the local of SDF-1 treatment scaffold at the wound site enhanced neovascularization. The wounds treated with SDF-1 scaffolds also exhibited higher vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-β) expression in Western blot assays. Based on the wound-healing activity and beneficial characteristics, the SDF-1-loaded CHI scaffold demonstrates potential as a material for treating skin wounds

A study of dose verification and comparison for complex irradiation field with high dose rate radiation by using a 3D N-isopropylacrylamide gel dosimeter

[[abstract]]This study aimed to investigate dosimeter characteristics by using a photon beam with and without the flattening filter of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) by using a 3D N-isopropylacrylamide (NIPAM) polymer gel. A self-developed optical computed tomography scheme was used to measure the dose distribution. Gamma evaluation was performed between the dose distribution calculated by a treatment planning system and the measured dose distribution by using the criteria of 3% dose difference and 3 mm distance to agreement. Under these criteria, the passing rates showed no significant difference between IMRT and VMAT irradiation with and without the flattening filter. All these results revealed that the NIPAM gel dosimeter was for high-dose-rate radiation and clinical-pretreatment verifications

Novel bilayer wound dressing based on electrospun gelatin/keratin nanofibrous mats for skin wound repair

[[abstract]]A bilayer membrane (GKU) with a commercial polyurethane wound dressing as an outer layer and electrospun gelatin/keratin nanofibrous mat as an inner layer was fabricated as a novel wound dressing. Scanning electron micrographs showed that gelatin/keratin nanofibers had a uniform morphology and bead-free structure with average fiber diameter of 160.4 nm. 3-(4,5-Dimethylthiazolyl)-2,5-diphenyltetrazolium bromide assay using L929 fibroblast cells indicated that the residues released from the gelatin/keratin composite nanofibrous mat accelerated cell proliferation. Cell attachment experiments revealed that adhered cells spread better and migrated deeper into the gelatin/keratin nanofibrous mat than that into the gelatin nanofibrous mat. In animal studies, compared with the bilayer membrane without keratin, gauze and commercial wound dressing, Comfeel®, GKU membrane gave much more number of blood vessels and a greater reduction in wound area at 4 days, and better wound repair at 14 days with a thicker epidermis and larger number of newly formed hair follicles. GKU membrane, thus, could be a good candidate for wound dressing applications