Development of Organic/Inorganic Hybrid Materials for Fully Degradable Reactive Oxygen Species-Releasing Stents for Antirestenosis.

Despite innovative advances in stent technology, restenosis remains a crucial issue for the clinical implantation of stents. Reactive oxygen species (ROS) are known to potentially accelerate re-endothelialization and lower the risk of restenosis by selectively controlling endothelial cells and smooth muscle cells. Recently, several studies have been conducted to develop biodegradable polymeric stents. As biodegradable polymers are not electrically conductive, double metallic layers are required to constitute a galvanic couple for ROS generation. Here, we report a new biodegradable hybrid material composed of a biodegradable polymer substrate and double anodic/cathodic metallic layers for enhancing re-endothelialization and suppressing restenosis. Pure Zn and Mg films (3 µm thick) were deposited onto poly-l-lactic acid (PLLA) substrates by DC magnetron sputtering, and a long-term immersion test using biodegradable hybrid materials was performed in phosphate-buffered solution (PBS) for 2 weeks. The concentrations of superoxide anions and hydrogen peroxide generated by the corrosion of biodegradable metallic films were monitored every 1 or 2 days. Both superoxide anions and hydrogen peroxide were seamlessly generated even after the complete consumption of the anodic Mg layer. It was confirmed that the superoxide anions and hydrogen peroxide were formed not only by the galvanic corrosion between the anode and cathode layers but also by the corrosion of a single Mg or Zn layer. The corrosion products of the Mg and Zn films in PBS were phosphate, oxide, or chloride of the biodegradable metals. Thus, it is concluded that ROS generation by the corrosion of PLLA-based hybrid materials can be sustained until the exhaustion of the cathode metal layer.

Suppression of T24 human bladder cancer cells by ROS from locally delivered hematoporphyrin-containing polyurethane films.

Systemic injection of a photosensitizer is a general method in photodynamic therapy, but it has complications due to the unintended systemic distribution and remnants of photosensitizers. This study focused on the possibility of suppressing luminal proliferative cells by excessive reactive oxygen species from locally delivered photosensitizer with biocompatible polyurethane, instead of the systemic injection method. We used human bladder cancer cells, hematoporphyrin as the photosensitizer, and polyurethane film as the photosensitizer-delivering container. The light source was a self-made LED (510 nm, 5 mW cm-2) system. The cancer cells were cultured on different doses of hematoporphyrin-containing polyurethane film and irradiated with LED for 15 minutes and 30 minutes each. After irradiating with LED and incubating for 24 hours, cell viability analysis, cell cycle analysis, apoptosis assay, intracellular and extracellular ROS generation study and western blot were performed. The cancer cell suppression effects of different concentrations of the locally delivered hematoporphyrin with PDT were compared. Apoptosis dominant cancer cell suppressions were shown to be hematoporphyrin dose-dependent. However, after irradiation, intracellular ROS amounts were similar in all the groups having different doses of hematoporphyrin, but these values were definitely higher than those in the control group. Excessive extracellular ROS from the intended, locally delivered photosensitizer for photodynamic treatment application had an inhibitory effect on luminal proliferative cancer cells. This method can be another possibility for PDT application on contactable or attachable lesions.

Influence of Biomimetic Materials on Cell Migration.

In recent tissue engineering applications, the advance of biomaterials has focused on the devising of biomimetic materials that are directing new tissue formation and capable of causing specific cellular responses. These advances can be controlled by modifying the devising parameters of the materials. The biomimetic materials potentially mimic many roles of ECM in tissues. For the homogeneous distribution and biocompatibility of scaffolds by cell migration with biomimetic materials, cell migration is studied because it has a important role in physiological phenomenon and in pathologies; cancer metastasis, immune response or embryonic development. This review discusses the migration of cells with biomimetic materials for tissue engineering. It is also summarized that the recent advances of cell migration with biomimetic materials in 2-D and 3-D for tissue engineering.

Sterilization of sealed PVDF pouches containing decellularized scaffold by electrical stimulation.

A terminal sterilization process for tissue engineering products, such as allografts and biomaterials is necessary to ensure complete removal of pathogenic microorganisms such as the bacteria, fungi, and viruses. However, it can be difficult to sterilize allografts and artificial tissue models packaged in wet conditions without deformation. In this study, we investigated the sterilization effects of electrical stimulation (ES) and assessed its suitability by evaluating sterility assurance levels in pouches at a constant current. Stability of polyvinylidene fluoride pouches was determined by a sterility test performed after exposure to five microorganisms (Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans) for 5 days; the sterility test was also performed with decellularized human dermal tissues inoculated with the five microorganisms. Sterilization using ES inactivated microorganisms both inside and outside of sealed pouches and caused no damage to the packaged tissue. Our results support the development of a novel system that involves ES sterilization for packaging of implantable biomaterials and human derived materials.

Gene transfer using liposome-complexed adenovirus seems to overcome limitations due to coxsackievirus and adenovirus receptor-deficiency of cancer cells, both in vitro and in vivo.

Use of adenoviruses as vehicle for gene therapy requires that target cells express appropriate receptors such as coxsakievirus and adenovirus receptor (CAR). We show here that CAR-deficiency in cancer cells, that limits adenoviral gene delivery, can be overcome by using adenovirus complexed with the liposome, Ad-PEGPE [1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly-ethylene glycol)-2000]. We first confirmed that CT-26 mouse colon cancer cells are deficient in CAR by RT-PCR, and then showed that CT-26 cells infected with Ad-GFP/PEGPE exhibited highly enhanced expression of green fluorescent protein (GFP), compared with those infected with Ad-GFP. GFP expression depends on the dose of liposome and adenovirus. Luciferase expression in livers treated with Ad-luc/PEGPE was about 1,000-fold less than those infected with Ad-luc. In a liver metastasis mouse tumor model developed by intrasplenic injection of CT-26 cells, luciferase expression following i.v. injection of Ad-luc/PEGPE was significantly higher in tumors than in adjacent non-neoplastic liver. Following systemic administration of Ad-GFP/PEGPE, GFP expression increased in tumors more than in adjacent liver while the reverse was true following administration of Ad-GFP. In the latter case, GFP expression was higher in liver than in tumors. This study demonstrates that systemic delivery of PEGPE-adenovirus complex is an effective tool of adenoviral delivery as it overcomes limitation due to CAR deficiency of target cells while reducing hepatic uptake and enhancing adenoviral gene expression in tumors.