Md. Tipu Sultan

Protective effects of a dimeric derivative of ferulic acid in animal models of Alzheimer's disease

Ferulic acid is a compound with potent anti-oxidant and anti-inflammatory activities. We previously reported the protective effects of ferulic acid administration against two animal models of Alzheimers disease (AD): intracerebroventricular (i.c.v.) injection of Aß1-42 in mice and APP/PS1 mutant transgenic mice. In this study using the same AD animal models, we examined the effect of KMS4001, one of dimeric derivatives of ferulic acid. Intragastric pretreatment of mice with KMS4001 (30mg/kg/day) for 5 days significantly attenuated the Aß1-42 (i.c.v.)-induced memory impairment both in passive avoidance test and in Y-maze test. APP/PS1 mutant transgenic mice at KMS4001 doses of 3 and 30mg/kg/day via drinking water showed the significantly enhanced novel-object recognition memory at both 1.5 and 3 months after the start of KMS4001 treatment. Treatment of APP/PS1 mutant transgenic mice with KMS4001 for 3 months at the doses of 3 and 30mg/kg/day markedly decreased Aβ1-40 and Aβ1-42 levels in the frontal cortex. The KMS4001 dose-response relationships for Aβ decrease and for improvement in novel-object recognition test corresponded to each other. Taken together, these results suggest that KMS4001 could be an effective drug candidate against AD.

Novel fabrication method of the peritoneal dialysis filter using silk fibroin with urease fixation system

During the last decade, there has been a great advance in the kidney dialysis system by wearable artificial kidney (WAK) system for end-stage renal disease patients. Uremic solute removal and water regeneration system are the most prerequisite for WAK to work properly. In this study, we designed a filtering membrane system by using immobilized urease silk fibroin filter and evaluated its comparative effectiveness with a PVDF filtering system in peritoneal dialysate regeneration system by urea removal efficacy. We evaluated this membranes characteristic and performances by conducting SEM-EDX analyze, water-binding abilities and porosity test, removal abilities of urea, cytotoxicity assay and enzyme activity assay. Under the condition for optimization of urease, the percentage removal of urea was about 40% and 60% in 50 mg/dL urea solution by urease immobilized PVDF and silk fibroin scaffolds, respectively. The batch experimental result showed that immobilized filter removed more than 50% of urea in 50 mg/dL urea solution. In addition silk fibroin with urease filter removed 90 percent of urea in the peritoneal dialysate after 24 h filtration. We suggest that silk fibroin with urease fixation filter can be used more effectively for peritoneal dialysate regeneration system, which have hydrophilic property and prolonged enzyme activity.

Artificial Auricular Cartilage Using Silk Fibroin and Polyvinyl Alcohol Hydrogel

Several methods for auricular cartilage engineering use tissue engineering techniques. However, an ideal method for engineering auricular cartilage has not been reported. To address this issue, we developed a strategy to engineer auricular cartilage using silk fibroin (SF) and polyvinyl alcohol (PVA) hydrogel. We constructed different hydrogels with various ratios of SF and PVA by using salt leaching, silicone mold casting, and freeze-thawing methods. We characterized each of the hydrogels in terms of the swelling ratio, tensile strength, pore size, thermal properties, morphologies, and chemical properties. Based on the cell viability results, we found a blended hydrogel composed of 50% PVA and 50% SF (P50/S50) to be the best hydrogel among the fabricated hydrogels. An intact 3D ear-shaped auricular cartilage formed six weeks after the subcutaneous implantation of a chondrocyte-seeded 3D ear-shaped P50/S50 hydrogel in rats. We observed mature cartilage with a typical lacunar structure both in vitro and in vivo via histological analysis. This study may have potential applications in auricular tissue engineering with a human ear-shaped hydrogel.

Precisely printable and biocompatible silk fibroin bioink for digital light processing 3D printing

Although three-dimensional (3D) bioprinting technology has gained much attention in the field of tissue engineering, there are still several significant engineering challenges to overcome, including lack of bioink with biocompatibility and printability. Here, we show a bioink created from silk fibroin (SF) for digital light processing (DLP) 3D bioprinting in tissue engineering applications. The SF-based bioink (Sil-MA) was produced by a methacrylation process using glycidyl methacrylate (GMA) during the fabrication of SF solution. The mechanical and rheological properties of Sil-MA hydrogel proved to be outstanding in experimental testing and can be modulated by varying the Sil-MA contents. This Sil-MA bioink allowed us to build highly complex organ structures, including the heart, vessel, brain, trachea and ear with excellent structural stability and reliable biocompatibility. Sil-MA bioink is well-suited for use in DLP printing process and could be applied to tissue and organ engineering depending on the specific biological requirements.Although 3D bioprinting technology has gained much attention in the field of tissue engineering, there are still several significant challenges that need to be overcome. Here, the authors present silk fibroin bioink with printability and biocompatibility suited for digital light processing 3D printing.

Fabrication and characterization of the porous duck’s feet collagen sponge for wound healing applications

Abstract There are several artificial dermis commonly use to cover the wound and promote healing. The major goal of wound management is fast and scarless healing. However, there is no ideal skin substitute, that is effective to accelerate wound healing without scar formation. Artificial dermis substitute also has some drawbacks, such as high cost, insufficient available period and donor pathogen infection. To overcome these problems, we developed duck’s feet collagen (DFC) sponge as artificial dermal substitutes for the treatment of full-thickness skin defects. We measured these DFC sponge’s comparative characteristics and performances with an artificial dermis Colladerm by carried out SEM-EDX analyze, water-binding abilities and porosity test. Biocompatibility test was also performed using CCK-8 cytotoxicity assay. We also evaluated its wound healing effects for a full-thickness skin wound and compared with Colladerm in a rat model. Histological studies were carried via hematoxylin and eosin and Masson’s Trichrome staining. Although the wound healing effect of the DFC sponge was almost similar to that of Colladerm, the DFC sponge did not induce scar formation and wound contracture like Colladerm. We suggest that DFC sponge can be used as an ideal dermal substitute to the treatment of full-thickness skin wound.

NF-κB signaling is key in the wound healing processes of silk fibroin

Silk fibroin (SF) is a well-studied biomaterial for tissue engineering applications including wound healing. However, the signaling mechanisms underlying the impact of SF on this phenomenon have not been determined. In this study, through microarray analysis, regulatory genes of NF-ĸB signaling were activated in SF-treated NIH3T3 cells along with other genes. Immunoblot analysis confirmed the activation of the NF-ĸB signaling pathway as SF induced protein expression levels of IKKα, IKKβ, p65, and the degradation of IκBα. The treatment of NIH3T3 cells with SF also increased the expression of cyclin D1, vimentin, fibronectin, and vascular endothelial growth factor (VEGF). The expression of these factors by SF treatment was abrogated when NF-ĸB was inhibited by a pharmacological inhibitor Bay 11-7082. Knockdown of NF-ĸB using siRNA of IKKα and IKKβ also inhibited the SF-induced wound healing response of the NIH3T3 cells in a wound scratch assay. Collectively, these results indicated that SF-induced wound healing through the canonical NF-κB signaling pathway via regulation of the expression of cyclin D1, vimentin, fibronectin, and VEGF by NIH3T3 cells. Using an in vivo study with a partial-thickness excision wound in rats we demonstrated that SF-induced wound healing via NF-κB regulated proteins including cyclin D1, fibronectin, and VEGF. The in vitro and in vivo data suggested that SF induced wound healing via modulation of NF-ĸB signaling regulated proteins. STATEMENT OF SIGNIFICANCE Silk fibroin has been effectively used as a dressing for wound treatment for more than a century. However, mechanistic insight into the basis for wound healing via silk fibroin has not been elucidated. Here we report a key mechanism involved in silk fibroin induced wound healing both in vitro and in vivo. Using genetic- and protein-level analyses, NF-κB signaling was found to regulate silk fibroin-induced wound healing by modulating target proteins. Thus, the NF-κB signaling pathway may be utilized as a therapeutic target during the formulation of silk fibroin-based biomaterials for wound healing and tissue engineering.

New concept of 3D printed bone clip (polylactic acid/hydroxyapatite/silk composite) for internal fixation of bone fractures

Abstract Open reduction with internal fixation is commonly used for the treatment of bone fractures. However, postoperative infection associated with internal fixation devices (intramedullary nails, plates, and screws) remains a significant complication, and it is technically difficult to fix multiple fragmented bony fractures using internal fixation devices. In addition, drilling in the bone to install devices can lead to secondary fracture, bone necrosis associated with postoperative infection. In this study, we developed bone clip type internal fixation device using three- dimensional (3D) printing technology. Standard 3D model of the bone clip was generated based on computed tomography (CT) scan of the femur in the rat. Polylacticacid (PLA), hydroxyapatite (HA), and silk were used for bone clip material. The purpose of this study was to characterize 3D printed PLA, PLA/HA, and PLA/HA/Silk composite bone clip and evaluate the feasibility of these bone clips as an internal fixation device. Based on the results, PLA/HA/Silk composite bone clip showed similar mechanical property, and superior biocompatibility compared to other types of the bone clip. PLA/HA/Silk composite bone clip demonstrated excellent alignment of the bony segments across the femur fracture site with well-positioned bone clip in an animal study. Our 3D printed bone clips have several advantages: (1) relatively noninvasive (drilling in the bone is not necessary), (2) patient-specific design (3) mechanically stable device, and (4) it provides high biocompatibility. Therefore, we suggest that our 3D printed PLA/HA/Silk composite bone clip is a possible internal fixation device.

In vitro and in vivo evaluation of the duck's feet collagen sponge for hemostatic applications

Recently different hemostatic agents have been developed, but most of them are ineffective in severe bleeding and expensive or cause safety concerns. In this study, we fabricated ducks feet collagen-based porous sponges and investigated its use as a hemostatic agent. We determined the sponges physical and biological characteristics and compared with Avitene via scanning electron microscope analysis, water-uptake abilities and porosity test, and cytotoxicity assay. The ducks feet collagen/silk sponge showed a larger interconnected porous structure compared to others sponges. The ducks feet collagen/silk sponge also exhibited significantly higher porosity than Avitene. Hemostatic properties of the sponges were evaluated by whole blood clotting and rat femoral artery hemorrhage experiment. The addition of silk to ducks feet collagen showed better blood clotting ability than Avitene in vitro. However, rat femoral artery hemorrhage test showed a similar hemostatic property between the ducks feet collagen-based sponges and Avitene. We suggest that ducks feet collagen-based sponge can be effectively used for hemostatic applications.

Scant Extracellular NAD Cleaving Activity of Human Neutrophils is Down-Regulated by fMLP via FPRL1

Extracellular nicotinamide adenine dinucleotide (NAD) cleaving activity of a particular cell type determines the rate of the degradation of extracellular NAD with formation of metabolites in the vicinity of the plasma membrane, which has important physiological consequences. It is yet to be elucidated whether intact human neutrophils have any extracellular NAD cleaving activity. In this study, with a simple fluorometric assay utilizing 1,N6-ethenoadenine dinucleotide (etheno-NAD) as the substrate, we have shown that intact peripheral human neutrophils have scant extracellular etheno-NAD cleaving activity, which is much less than that of mouse bone marrow neutrophils, mouse peripheral neutrophils, human monocytes and lymphocytes. With high performance liquid chromatography (HPLC), we have identified that ADP-ribose (ADPR) is the major extracellular metabolite of NAD degradation by intact human neutrophils. The scant extracellular etheno-NAD cleaving activity is decreased further by N-formyl-methionine-leucine-phenylalanine (fMLP), a chemoattractant for neutrophils. The fMLP-mediated decrease in the extracellular etheno-NAD cleaving activity is reversed by WRW4, a potent FPRL1 antagonist. These findings show that a much less extracellular etheno-NAD cleaving activity of intact human neutrophils compared to other immune cell types is down-regulated by fMLP via a low affinity fMLP receptor FPRL1.

Silk Fibroin in Wound Healing Process

Silk fibroin (SF), a natural bioproduct, has been extensively used in biological and biomedical fields including wound healing due to its robust biocompatibility, less immunogenic, non-toxic, non-carcinogenic, and biodegradable properties. SF in different morphologic forms, such as hydrogels, sponges, films, electrospun nanofiber mats, and hydrocolloid dressings, have been successfully used for therapeutic use as wound dressings to induce the healing process. SF has also been known to promote wound healing by increasing the cell growth, proliferation, and migration of different cells types involved in the different phase of wound healing process. In this review, we summarize the different morphologic forms of SF that have been used in the treatment of various wound healing process. We also discuss the effect of SF on various cells types during the SF-induced healing process. Furthermore, we highlight molecular signaling aspects of the SF-induced healing process.