Ching-Wen Li

Synthesis of antibacterial TiO2/PLGA composite biofilms

UNLABELLED This study developed a TiO2/PLGA [poly(lactic-co-glycolic acid)] composite biomaterial, which possesses antibacterial properties but is biocompatible, for artificial dressing applications. A sol-gel method was used for the preparation of the nano TiO2 powder with anatase phase. Several concentration ratios of TiO2 versus PLGA were analyzed to optimize the disinfection efficiency of the composite biomaterial. The antibacterial activity of the fabricated TiO2/PLGA composite was measured against Staphylococcus aureus and Escherichia coli. To evaluate the feasibility of the biomaterial on wound healing in vitro, human keratinocytes (HaCaTs), fibroblasts (L929s), and bovine carotid artery endothelial cells (BECs) were seeded on the TiO2/PLGA composite biofilms. To investigate the histological effect of the biocompatible biofilm in vivo, a rat subcutaneous implantation was performed. Our results show that TiO2/PLGA composite biofilms containing 10% TiO2 nanoparticles have an effective antibacterial property, a good survival rate on HaCaTs and L929s, and relative safe stability in tissue implantation. FROM THE CLINICAL EDITOR This study reports the development of titanium dioxide-polylactic-co-glycolic acid composite biofilms, which possess antibacterial properties and are biocompatible for dressing applications, as demonstrated in a model system.

Fabrication of pillared PLGA microvessel scaffold using femtosecond laser ablation.

One of the persistent challenges confronting tissue engineering is the lack of intrinsic microvessels for the transportation of nutrients and metabolites. An artificial microvascular system could be a feasible solution to this problem. In this study, the femtosecond laser ablation technique was implemented for the fabrication of pillared microvessel scaffolds of polylactic-co-glycolic acid (PLGA). This novel scaffold facilitates implementation of the conventional cell seeding process. The progress of cell growth can be observed in vitro by optical microscopy. The problems of becoming milky or completely opaque with the conventional PLGA scaffold after cell seeding can be resolved. In this study, PLGA microvessel scaffolds consisting of 47 μm × 80 μm pillared branches were produced. Results of cell culturing of bovine endothelial cells demonstrate that the cells adhere well and grow to surround each branch of the proposed pillared microvessel networks.

Nerve guidance conduit with a hybrid structure of a PLGA microfibrous bundle wrapped in a micro/nanostructured membrane

Nerve repair in tissue engineering involves the precise construction of a scaffold to guide nerve cell regeneration in the desired direction. However, improvements are needed to facilitate the cell migration/growth rate of nerves in the center of a nerve conduit. In this paper, we propose a nerve guidance conduit with a hybrid structure comprising a microfibrous poly(lactic-co-glycolic acid) (PLGA) bundle wrapped in a micro/nanostructured PLGA membrane. We applied sequential fabrication processes, including photolithography, nano-electroforming, and polydimethylsiloxane casting to manufacture master molds for the repeated production of the PLGA subelements. After demolding it from the master molds, we rolled the microfibrous membrane into a bundle and then wrapped it in the micro/nanostructured membrane to form a nerve-guiding conduit. We used KT98/F1B-GFP cells to estimate the migration rate and guidance ability of the fabricated nerve conduit and found that both elements increased the migration rate 1.6-fold compared with a flat PLGA membrane. We also found that 90% of the cells in the hybrid nano/microstructured membrane grew in the direction of the designed patterns. After 3 days of culturing, the interior of the nerve conduit was filled with cells, and the microfiber bundle was also surrounded by cells. Our conduit cell culture results also demonstrate that the proposed micro/nanohybrid and microfibrous structures can retain their shapes. The proposed hybrid-structured conduit demonstrates a high capability for guiding nerve cells and promoting cell migration, and, as such, is feasible for use in clinical applications.

Fabrication of biocompatible high aspect ratio Au–Ni coaxial nanorod arrays using the electroless galvanic displacement reaction method

In this study, a novel method of fabrication of high aspect ratio magnetic Au–Ni coaxial nanorod arrays is proposed. The fabrication procedure involves anodic aluminum oxide (AAO) template preparation, barrier-layer surface photolithography, barrier layer etching, working electrode coating, nickel electroforming, alumina etching, and gold-plating by the electroless galvanic displacement reaction (EGDR) process. Experimental results have demonstrated that it is possible to synthesize high aspect ratio magnetic Au–Ni coaxial nanorod arrays using the method proposed in this study. The aspect ratio of the synthesized Au–Ni coaxial nanorod arrays was estimated to be 100–140. A two-dimensional electromagnetic force actuating system was set up to manipulate the 2-D movement of a patterned Au–Ni coaxial nanorod array. Biocompatibility of the proposed Au–Ni coaxial nanorod array was confirmed through the culture of endothelial cells (ECs) on the array surface. The influences of the stiffness of the nanorod array in terms of its height on cell morphology and differentiation were investigated. The results of the cell culture indicate that our Au–Ni coaxial nanorod array can be used to manipulate the differentiation of cells cultured on it by adjusting the array height.

Nanoporous anodic aluminum oxide tube encapsulating a microporous chitosan/collagen composite for long-acting drug release

The objective of this study is to develop a long-acting and implantable drug-release device that can effectively control the release rate and concentration of the loaded drug. The proposed device consists of a tubular nanoporous anodic aluminum oxide (AAO) encapsulating a microporous chitosan/collagen composite. The nanopore size of the AAO tube can be modified by adjusting the anodization parameters, which in turn adjust the release rate and concentration, while the microporous chitosan/collagen composite provides the long-acting release feature. Fabrication results indicate that the AAO tube has a uniform pore arrangement with a pore size around 50 nm. The synthesized microporous chitosan/collagen composite containing 90% chitosan yielded the highest moisture content and was therefore used as the drug carrier. Release experiments demonstrate that the proposed long-acting drug release device had released less than 65% of the loading drug on the 17th release day. We then applied the proposed long-acting drug-release scheme as a recombinant human bone morphogenetic-protein 2 (rh-BMP2) release device to induce differentiation of pre-osteoblast MC3T3-E1 cells into osteoblasts. Results from alkaline phosphate and alizarin red S assays demonstrate that the total amount of rh-BMP2 consumed by the proposed AAO tube is much less than that consumed using the conventional culture approach. Furthermore, our approach has the advantage of requiring only one-time dosing, whereas the conventional approach requires the periodic renewal of rh-BMP2. AAOs one-time dosing feature combined with its biocompatibility and biodegradability can be beneficial in real implant applications.

Control of cell proliferation by a porous chitosan scaffold with multiple releasing capabilities

Abstract The aim of this study was to develop a porous chitosan scaffold with long-acting drug release as an artificial dressing to promote skin wound healing. The dressing was fabricated by pre-freezing at different temperatures (−20 and −80 °C) for different periods of time, followed by freeze-drying to form porous chitosan scaffolds with different pore sizes. The chitosan scaffolds were then used to investigate the effect of the controlled release of fibroblast growth factor-basic (bFGF) and transforming growth factor-β1 (TGFβ1) on mouse fibroblast cells (L929) and bovine carotid endothelial cells (BEC). The biocompatibility of the prepared chitosan scaffold was confirmed with WST-1 proliferation and viability assay, which demonstrated that the material is suitable for cell growth. The results of this study show that the pore sizes of the porous scaffolds prepared by freeze-drying can change depending on the pre-freezing temperature and time via the formation of ice crystals. In this study, the scaffolds with the largest pore size were found to be 153 ± 32 μm and scaffolds with the smallest pores to be 34 ± 9 μm. Through cell culture analysis, it was found that the concentration that increased proliferation of L929 cells for bFGF was 0.005 to 0.1 ng/mL, and the concentration for TGFβ1 was 0.005 to 1 ng/mL. The cell culture of the chitosan scaffold and growth factors shows that 3.75 ng of bFGF in scaffolds with pore sizes of 153 ± 32 μm can promote L929 cell proliferation, while 400 pg of TGFβ1 in scaffolds with pore size of 34 ± 9 μm can enhance the proliferation of L929 cells, but also inhibit BEC proliferation. It is proposed that the prepared chitosan scaffolds can form a multi-drug (bFGF and TGFβ1) release dressing that has the ability to control wound healing via regulating the proliferation of different cell types.

Synthesis of antibacterial TiO 2 /PLGA composite biofilms

The main purpose of this study was to develop a TiO2/PLGA composite biomaterial for artificial dressing applications. E. coli and S. aureus were used as biological indicators for the disinfection efficiency of the proposed TiO2/PLGA composite. Various concentration ratios of TiO2 verse PLGA were implemented to optimize the disinfection efficiency of the composite biomaterial. Cell seedings of BECs and L929s on the TiO2/PLGA composite biomaterial are further conducted to evaluate the feasibility of the TiO2/PLGA composite biomaterial on wound healing applications. Experimental results illustrated that TiO2/PLGA composite biofilms containing 10% of TiO2 nanoparticles revealed an effective antibacterial property but kept a comparatively low suppression on cell growth.

The influence of different nanostructured scaffolds on fibroblast growth.

Abstract Skin serves as a protective barrier, modulating body temperature and waste discharge. It is therefore desirable to be able to repair any damage that occurs to the skin as soon as possible. In this study, we demonstrate a relatively easy and cost-effective method for the fabrication of nanostructured scaffolds, to shorten the time taken for a wound to heal. Various scaffolds consisting of nanohemisphere arrays of poly(lactic-co-glycolic acid) (PLGA), polylactide and chitosan were fabricated by casting using a nickel (Ni) replica mold. The Ni replica mold is electroformed using the highly ordered nanohemisphere array of the barrier-layer surface of an anodic aluminum oxide membrane as the template. Mouse fibroblast cells (L929s) were cultured on the nanostructured polymer scaffolds to investigate the effect of these different nanohemisphere arrays on cell proliferation. The concentration of collagen type I on each scaffold was then measured through enzyme-linked immunosorbent assay to find the most effective scaffold for shortening the wound-healing process. The experimental data indicate that the proliferation of L929 is superior when a nanostructured PLGA scaffold with a feature size of 118 nm is utilized.

Flexible Photonic Crystal Material for Multiple Anticounterfeiting Applications

In this study, a nanoimprinting method was introduced to fabricate polycarbonate films with transparent and flexible photonic crystal (FPC) structures. The fabricated flexible polymer films display a full-color grating because of the nanohemispherical structures on the surface. Through the Bragg diffraction formula, it was confirmed that the FPC polymer films transfer a part of the light energy to the second-order diffraction spectrum. Furthermore, the full-color grating properties can be modulated through geometric deformation because of the films elasticity. Additionally, anticounterfeiting features were also successfully achieved when the polymer films were either engraved with drawings and bent or patterned with fluorophores, which can be revealed under ultraviolet light. The most important aspect of this research is that the preparation of this FPC-structured polymer film is inexpensive and convenient, enabling the mass production of a new generation of smart materials.

Fabrication of Pillared PLGA Microvessel Scaffold Using Femtosecond Laser Ablation

One of the continuing, persistent challenges confronting tissue engineering is the lack of intrinsic microvessels for the transportation of nutrients and metabolites. An artificial microvascular system can be a feasible solution to this problem. In this study, the femtosecond laser ablation technique was implemented for the fabrication of pillared microvessel scaffolds in PLGA. This novel scaffold enable the conventional cell seeding process to be implemented and the progress of cell growth to be observed in vitro by an optical microscopy. Hence, the milky and completely opaque problems of the conventional PLGA scaffold after cell seeding can be resolved. Currently, PLGA microvessel scaffolds consisting of 30μm×200μm pillared branches have been produced. Cell cultural results of BECs demonstrate that cells can well adhere and grow surrounding each branch of the proposed pillared microvessel networks. The promising results reveal that an artificial microvessel networks for tissue engineering can be completely realized.Copyright