Joshua Lee

Bimodal fibrous structures for tissue engineering: Fabrication, characterization and in vitro biocompatibility.

We report for the first time a polycaprolactone-human serum albumin (PCL-HSA) membrane with bimodal structures comprised of spider-web-like nano-nets and conventional fibers via facile electro-spinning/netting (ESN) technique. Such unique controllable morphology was developed by electrospinning the blend solution of PCL (8wt% in HFIP 1,1,1,3,3,3,-Hexafluoro-2-propanol) and HSA (10wt% deionized water). The phase separation during electrospinning caused the formation of bimodal structure. Various processing factors such as applied voltage, feeding rate, and distance between nozzle tip and collector were found responsible for the formation and distribution of the nano-nets throughout the nanofibrous mesh. Field emission electron microscopy (FE-SEM) confirmed that the nano-nets were composed of interlinked nanowires with an ultrathin diameter (10-30nm). When compared with a pure PCL membrane, the membrane containing nano-nets was shown to have better support for cellular activities as determined by cell viability and attachment assays. These results revealed that the blending of albumin, a hydrophilic biomolecule, with PCL, a hydrophobic polymer, proves to be an outstanding approach to developing membranes with controlled spider-web-like nano-nets for tissue engineering.

Synthesis, characterization, organic compound degradation activity and antimicrobial performance of g-C3N4 sheets customized with metal nanoparticles-decorated TiO2 nanofibers

In this article, we discuss for the first time a simple and direct approach to fabricate multifunctional silver nanoparticles (NPs) decorated porous TiO2 nanofibers (NFs) interpolated on a thin and large g-C3N4 sheet by using a simple and efficient electrospinning–calcination process. An angled two-nozzle electrospinning process was used here, and the composite material that was produced has the large specific surface area of the NPs, the anisotropic properties of the NFs and distinctive optical and electronic properties of sheet-like structures, which is desirable for various applications. Different characterizations were examined using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and UV-visible diffused reflectance spectroscopy. The prepared composite showed excellent photocatalytic activity with visible light when compared with pristine TiO2 and g-C3N4 and single-component modified Ag/TiO2 and TiO2/g-C3N4 composites, as measured by the degradation of different organic dyes. Here, the large surface area g-C3N4 sheets provide the formation of ternary hetero-structures among the NPs, NFs and sheets, and encouraged electron transfer between them. Moreover, such a hybrid composite showed improved antibacterial properties against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria.

Polydopamine-assisted immobilization of hierarchical zinc oxide nanostructures on electrospun nanofibrous membrane for photocatalysis and antimicrobial activity

Depositing of hierarchical ZnO nanostructures on electrospun nanofibers and their proper attachment has gained significant interest for myriad applications. However, the weak attachment of such nanostructures to the nanofiber surface limits their practical applications. In this study, a simple and efficient method has been developed for preparing hierarchical ZnO nanorod deposited polyurethane (PU) nanofiber by combining electrospinning, surface functionalization and hydrothermal treatment. Electrospun PU nanofibers were coated with polydopamine (Pdopa) via dip coating method. The resulting Pdopa coated PU nanofibrous mat was soaked in aqueous ZnO nanoparticles (ZnONPs) solution in order to seed the metal-oxide particles on its surface. Later, ZnO nanorods (ZNRs) were grown on the ZnO-seeded electrospun PU nanofiber via a hydrothermal process. X-ray photoelectron spectroscopy (XPS), Field-Emission Scanning electron microscopy (FE-SEM), X-ray diffraction pattern (XRD) and infra-red (IR) spectra indicated that ZnO nanorods firmly adhered to the functionalized PU nanofiber surface and had high photocatalytic/antimicrobial activity at the low-intensity UV-LED device with good reusability. The catechol group of Pdopa not only causes adhesion of ZnO nanostructures, but also act as an electron trap, preventing the recombination of e-h pairs and thereby improving the photocatalytic efficiency. We believe that the fabricated composite membrane with antifouling effect and photocatalytic activity is a potential candidate for organic pollutant degdration and wastewater purification.

Amorphous apatite thin film formation on a biodegradable Mg alloy for bone regeneration: strategy, characterization, biodegradation, and in vitro cell study

Bioactive films with a nanoplate structure were prepared on the surface of a biodegradable AZ31B magnesium (Mg) alloy via anodization in simulated body fluid (SBF) as an electrolyte to control Mg biodegradability and improve surface bioactivity. The effect of the electrolyte temperature and pH values on the formation of the biomimetic film were studied. The electrolyte was set at three different temperatures of 37, 50, and 80 °C, with pH values ranging from 7.4 to 8 for the lower electrolyte temperature and 11.5–12 for the two higher levels of temperature. The apatite films on the different samples were characterized using X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FE-SEM), EDS element mapping, X-ray photon spectroscopy (XPS), and FTIR spectroscopy. The water contact angles of the different surfaces were evaluated, moreover, the corrosion behaviors of the different samples were studied using electrochemical potentiodynamic DC, electrochemical impedance spectroscopy (EIS), and immersion tests. The human fetal-osteoblast cell line hFOB 1.19 was used in a cell culture test, and the biological response and cell function were evaluated in vitro using DNA and PCR. The decomposition of the apatite film was affected by the anodization electrolyte temperature, resulting in an amorphous structure. It is observed that the apatite structure has nanoplates at electrolyte temperature (37 to 50) °C and these have a tendency to disappear at 80 °C.

Composite PCL/HA/simvastatin electrospun nanofiber coating on biodegradable Mg alloy for orthopedic implant application

Recently, magnesium (Mg) and its alloys have attracted more attention because of their biodegradability and fascinating mechanical properties in the medical field. However, their low corrosion resistance and high degradability in the body have a great effect on mechanical stability and cytocompatibility, which hinders its clinical applications. Therefore, here we introduce a bifunctional composite coating composed of polycaprolactone and synthesized hydroxyapatite nanoparticles (HA-NPs) loaded with simvastatin deposited on the AZ31 alloy via electrospinning technique. The synthesized HA-NPs and composite nanofibers layer were characterized using TEM, FE-SEM, FTIR, and XRD to understand the physiochemical properties of the composite nanofibers compared to pristine polymer and bare alloy. Corrosion resistance was evaluated electrochemically using potentiodynamic polarization and EIS measurements, and biodegradability was evaluated in terms of pH and Mg ions release in SBF solution. The as-prepared coating was found to retard the corrosion and increased the osteocompatibility as resulted in cell culture test, a higher cell attachment and proliferation on the implant biointerface, in addition to releasing simvastatin in a controlled platform.

Investigation of Composite Nano Air Filter for Improving Antimicrobial Activity and Reducing VOCs Using a High Speed Upward Electrospinning System

A new nano air filter for fine dust filtration with antibacterial and volatile organic compounds (VOCs) adsorption properties was fabricated using a bottom-up, high-speed electrospinning system. To optimize production, polyurethane fibers were electrospun at various voltages on polypropylene nonwoven fabrics, and results show that fiber diameter decreased as voltage increased. Silver nanoparticles (AgNPs) and Activated Carbon (AC) were used as antimicrobials and VOC-reducing agents. FTIR, SEM, and EDS were performed to analyze the resulting filter fabricated by electrospinning. FTIR and EDS results show that the AgNPs and activated carbon added to the PU fibers were successfully integrated into the PP nonwoven fabric.

Preliminary Study for Measurement of Shear Stress and Hemocompatibility Using Commercialized Lab on a Chip

We have investigated the effect of flow rate on shear stress and in turn thrombus formation on a lab-on-a-chip with a microchannel that is suitable for cell culture and growth. Using a combination of Arduino UNO, Arduino Motor Shield, and a SERVO stepper motor, we created a pump system that closely mimics the in vivo conditions of the human body. With this system, we achieved continuous flow of blood and observed attached platelets at the bottom of the collagen coated microslide, confirming that with shear stress, thrombus formation increases.

Electrospun Nanofibrous Nerve Conduits

An injury to the human nervous system, which plays a major role in our daily lives by being involved in our thought and action processes, has been one of the greatest issues in the medical field. Social costs are considerably high because of these injuries and the many ongoing studies searching for cures to nervous system injuries. As a result of these efforts, electrospinning technology has been found to a suitable alternative to fabricating scaffolds for nerve regeneration. The electrospun nanofibrous scaffold can provide the regenerating nervous system with cell-friendly environments that have sufficient porosity, mechanical strength, guidance cues, etc. First, the anatomies of the central and peripheral nervous systems and their regeneration mechanisms are introduced and compared to each other. Second, the mechanisms, requirements, and favored properties are discussed. Finally, various fabrication methods and the current evolving concept of electrospun nerve conduits with functionalization strategies such as cell loading, neurotrophic biomolecule or nanoparticle immobilization, and conductive polymer use are discussed.