Cheol Sang Kim

Electrospun antibacterial polyurethane-cellulose acetate-zein composite mats for wound dressing.

In this study, an antibacterial electrospun nanofibrous scaffolds with diameters around 400-700 nm were prepared by physically blending polyurethane (PU) with two biopolymers such as cellulose acetate (CA) and zein. Here, PU was used as the foundation polymer, was blended with CA and zein to achieve desirable properties such as better hydrophilicity, excellent cell attachment, proliferation and blood clotting ability. To prevent common clinical infections, an antimicrobial agent, streptomycin sulfate was incorporated into the electrospun fibers and its antimicrobial ability against the gram negative and gram positive bacteria were examined. The interaction between fibroblasts and the PU-CA and PU-CA-zein-drug scaffolds such as viability, proliferation, and attachment were characterized. PU-CA-zein-drug composite nanoscaffold showed enhanced blood clotting ability in comparison with pristine PU nanofibers. The presence of CA and zein in the nanofiber membrane improved its hydrophilicity, bioactivity and created a moist environment for the wound, which can accelerate wound recovery.

In Situ Synthesis of Antimicrobial Silver Nanoparticles within Antifouling Zwitterionic Hydrogels by Catecholic Redox Chemistry for Wound Healing Application

A multifunctional hydrogel that combines the dual functionality of both antifouling and antimicrobial capacities holds great potential for many bioapplications. Many approaches and different materials have been employed to synthesize such a material. However, a systematic study, including in vitro and in vivo evaluation, on such a material as wound dressings is highly scarce at present. Herein, we report on a new strategy that uses catecholic chemistry to synthesize antimicrobial silver nanoparticles impregnated into antifouling zwitterionic hydrogels. For this purpose, hydrophobic dopamine methacrylamide monomer (DMA) was mixed in an aqueous solution of sodium tetraborate decahydrate and DMA monomer became soluble after increasing pH to 9 due to the complexation between catechol groups and boron. Then, cross-linking polymerization of zwitterionic monomer was carried out with the solution of the protected dopamine monomer to produce a new hydrogel. When this new hydrogel comes in contact with a silver nitrate solution, silver nanoparticles (AgNPs) are formed in its structure as a result of the redox property of the catechol groups and in the absence of any other external reducing agent. The results obtained from TEM and XRD measurements indicate that AgNPs with diameters of around 20 nm had formed within the networks. FESEM images confirmed that the silver nanoparticles were homogeneously incorporated throughout the hydrogel network, and FTIR spectroscopy demonstrated that the catechol moiety in the polymeric backbone of the hydrogel is responsible for the reduction of silver ions into the AgNPs. Finally, the in vitro and in vivo experiments suggest that these mussel-inspired, antifouling, antibacterial hydrogels have great potential for use in wound healing applications.

Mussel-Inspired Electrospun Nanofibers Functionalized with Size-Controlled Silver Nanoparticles for Wound Dressing Application

Electrospun nanofibers that contain silver nanoparticles (AgNPs) have a strong antibacterial activity that is beneficial to wound healing. However, most of the literature available on the bactericidal effects of this material is based on the use of AgNPs with uncontrolled size, shape, surface properties, and degree of aggregation. In this study, we report the first versatile synthesis of novel catechol moieties presenting electrospun nanofibers functionalized with AgNPs through catechol redox chemistry. The synthetic strategy allows control of the size and amount of AgNPs on the surface of nanofibers with the minimum degree of aggregation. We also evaluated the rate of release of the AgNPs, the biocompatibility of the nanofibers, the antibacterial activity in vitro, and the wound healing capacity in vivo. Our results suggest that these silver-releasing nanofibers have great potential for use in wound healing applications.

One-step fabrication of multifunctional composite polyurethane spider-web-like nanofibrous membrane for water purification

A stable silver-doped fly ash/polyurathene (Ag-FA/PU) nanocomposite multifunctional membrane is prepared by a facile one-step electrospinning process using fly ash particles (FAPs). Colloidal solution of PU with FAPs and Ag metal precursor was subjected to fabricate nanocomposite spider-web-like membrane using electrospinning process. Presence of N,N-dimethylformamide (solvent of PU) led to reduce silver nitrate into Ag NPs. Incorporation of Ag NPs and FAPs through electrospun PU fibers is proven through electron microscopy and spectroscopic techniques. Presence of these NPs on PU nanofibers introduces several potential physicochemical properties such as spider-web-like nano-neeting for NPs separation, enhanced absorption capacity to remove carcinogenic arsenic (As) and toxic organic dyes, and antibacterial properties with reduce bio-fouling for membrane filter application. Preliminary observations used for above-mentioned applications for water treatment showed that it will be an economically and environmentally friendly nonwoven matrix for water purification. This simple approach highlights new avenues about the utilization of one pollutant material to control other pollutants in scalable and inexpensive ways.

In Situ Generation of Cellulose Nanocrystals in Polycaprolactone Nanofibers: Effects on Crystallinity, Mechanical Strength, Biocompatibility, and Biomimetic Mineralization

Post-electrospinning treatment is a facile process to improve the properties of electrospun nanofibers for various applications. This technique is commonly used when direct electrospinning is not a suitable option to fabricate a nonwoven membrane of the desired polymer in a preferred morphology. In this study, a representative natural-synthetic hybrid of cellulose acetate (CA) and polycaprolactone (PCL) in different ratios was fabricated using an electrospinning process, and CA in the hybrid fiber was transformed into cellulose (CL) by post-electrospinning treatment via alkaline saponification. Scanning electron microscopy was employed to study the effects of polymer composition and subsequent saponification on the morphology of the nanofibers. Increasing the PCL content in the PCL/CA blend solution caused a gradual decrease in viscosity, resulting in smoother and more uniform fibers. The saponification of fibers lead to pronounced changes in the physicochemical properties. The crystallinity of the PCL in the composite fiber was varied according to the composition of the component polymers. The water contact angle was considerably decreased (from 124° to less than 20°), and the mechanical properties were greatly enhanced (Youngs Modulus was improved by ≈20-30 fold, tensile strength by 3-4 fold, and tensile stress by ≈2-4 fold) compared to those of PCL and PCL/CA membranes. Regeneration of cellulose chains in the nanofibers increased the number of hydroxyl groups, which increased the hydrogen bonding, thereby improving the mechanical properties and wettability of the composite nanofibers. The improved wettability and presence of surface functional groups enhanced the ability to nucleate bioactive calcium phosphate crystals throughout the matrix when exposed to a simulated body fluid solution. Experimental results of cell viability assay, confocal microscopy, and scanning electron microscopy imaging showed that the fabricated nanofibrous membranes have excellent ability for MC3T3-E1 cell proliferation and growth. Given the versatility and widespread use of cellulose-synthetic hybrid systems in the construction of tissue-engineered scaffolds, this work provides a novel strategy to fabricate the biopolymer-based materials for applications in tissue engineering and regenerative medicine.

Synthesis, characterization, and mineralization of polyamide-6/calcium lactate composite nanofibers for bone tissue engineering

Polyamide-6 nanofibers containing calcium lactate (CL) on their surface were prepared by neutralization of lactic acid (LA) in core-shell structured polyamide-6/LA electrospun fibers. First, simple blending of LA with polyamide-6 solution was used for electrospinning which interestingly formed a thin LA layer around polyamide-6 nanofibers (core-shell structure) and then subsequent conversion of this LA into calcium lactate via neutralization using calcium base. FE-SEM and TEM images revealed that plasticizer capacity of LA led the formation of point-bonded structure due to the formation of shell layer of LA and core of polyamide-6. The bone formation ability of polyamide-6/calcium lactate composite fibers was evaluated by incubating in biomimetic simulated body fluid (SBF). The SBF incubation test confirmed the faster deposition of large amount of calcium phosphate around the composite polyamide-6/calcium lactate fibers compared to pristine polyamide-6. This study demonstrated a simple post electrospinning calcium compound coating technique of polymeric nanofibers for enhancing the bone biocompatibility of polyamide-6 fibers.

Electrospun polyurethane-dextran nanofiber mats loaded with Estradiol for post-menopausal wound dressing

Post-menopausal wound care management is a substantial burden on health services, since there are an increased number of elderly populations linked with age-related delayed wound healing. The controlled estrogen replacement can accelerate healing of acute cutaneous wounds, linked to its potent anti-inflammatory activity. The electrospinning technique can be used to introduce the desired therapeutic agents to the nanofiber matrix. So here we introduce a new material for wound tissue dressing, in which a polyurethane-dextran composite nanofibrous wound dressing material loaded with β-estradiol was obtained through electrospinning. Dextran can promote neovascularization and skin regeneration in chronic wounds. This study involves the characterization of these nanofibers and analysis of cell growth and proliferation to determine the efficiency of tissue regeneration on these biocomposite polymer nanofibrous scaffolds and to study the possibility of using it as a potential wound dressing material in the in vivo models.

Fabrication and characterization of electrospun zein/Ag nanocomposite mats for wound dressing applications

Wound dressing is a very important factor in the process of wound healing as proper wound care can accelerate the recovery of the wound. In this study, zein nanofibrous mats with fiber diameters around 350-500 nm were prepared by electrospinning and silver (Ag) nanoparticles around 20 nm were concurrently synthesized in situ into the mats. The electrospun nanofibers were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Cell viability and activity of fibroblasts cells in zein/Ag mats were also evaluated and results demonstrated good cytocompatibility and attachment of cells on the composite nanofibers. Also, the bactericidal activity of the fabricated mats against gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) was investigated via zone of inhibition test and results showed high anti-bacterial performance.

Electrospun propolis/polyurethane composite nanofibers for biomedical applications

Tissue engineering requires functional polymeric membrane for adequate space for cell migration and attachment within the nanostructure. Therefore, biocompatible propolis loaded polyurethane (propolis/PU) nanofibers were successfully prepared using electrospinning of propolis/PU blend solution. Here, composite nanofibers were subjected to detailed analysis using electron microscopy, FT-IR spectroscopy, thermal gravimetric analysis (TGA), and mechanical properties and water contact angle measurement. FE-SEM images revealed that the composite nanofibers became point-bonded with increasing amounts of propolis in the blend due to its adhesive properties. Incorporation of small amount of propolis through PU matrix could improve the hydrophilicity and mechanical strength of the fibrous membrane. In order to assay the cytocompatibility and cell behavior on the composite scaffolds, fibroblast cells were seeded on the matrix. Results suggest that the incorporation of propolis into PU fibers could increase its cell compatibility. Moreover, composite nanofibers have effective antibacterial activity. Therefore, as-synthesized nanocomposite fibrous mat has great potentiality in wound dressing and skin tissue engineering.

Multifunctional Nanocarpets for Cancer Theranostics: Remotely Controlled Graphene Nanoheaters for Thermo-Chemosensitisation and Magnetic Resonance Imaging

A new paradigm in cancer theranostics is enabled by safe multifunctional nanoplatform that can be applied for therapeutic functions together with imaging capabilities. Herein, we develop a multifunctional nanocomposite consisting of Graphene Oxide–Iron Oxide -Doxorubicin (GO-IO-DOX) as a theranostic cancer platform. The smart magnetic nanoplatform acts both as a hyperthermic agent that delivers heat when an alternating magnetic field is applied and a chemotherapeutic agent in a cancer environment by providing a pH-dependent drug release to administer a synergistic anticancer treatment with an enhanced T2 contrast for MRI. The novel GO-IO-DOX nanocomposites were tested in vitro and were observed to exhibit an enhanced tumoricidal effect through both hyperthermia and cancer cell-specific DOX release along with an excellent MRI performance, enabling a versatile theranostic platform for cancer. Moreover the localized antitumor effects of GO-IO-DOX increased substantially as a result of the drug sensitization through repeated application of hyperthermia.