Effect of metal surface characteristics on the adhesion performance of the integrated low-level energies method of adhesion.

We have previously proposed a new method of adhesion using the integrated low-level energy sources heat, vibration, and pressure. This adhesion method can be used to attach biological tissue to a metal object. Effects of surface roughness and energy of the metal subject on adhesion performance were studied by using commercially pure titanium (cpTi) and stainless steel (SUS304). Surface roughness and energy were changed by sandblast treatment and heat treatment, respectively. A porcine aorta was adhered to sandblast-treated SUS304 by use of an adhesion temperature of 80 °C, a vibration amplitude of 15 µm, a pressure of 2.5 MPa, an adhesion time of 120 s, and a surface roughness of an Ra 0.25 µm. The shear tensile strength of the adhesion was 0.45 MPa. The adhesion performance was improved by roughening the surface of the metal specimen. Surface energy has an insignificant effect on adhesive strength. The adhesion performance varied depending on metal material for the same surface roughness, Ra, and energy. Results from analysis of the surface roughness profile suggested that the size of surface asperity has an effect on adhesion performance.

Synthetic polymer-tissue adhesion using an ultrasonic scalpel.

BACKGROUND: Interface phenomena such as encapsulation and formation of dead space around implanted biomaterials lower biomaterial performance. To advance tissue adhesive technology, understanding the interactions between tissue (collagen) and polymer is indispensable. Adhesion between tissue and polymer was studied using an ultrasonically activated scalpel (UAS). METHODS: The Harmonic Scalpel was used as an ultrasonically activated scalpel for polymer and tissue adhesion. A piece of porcine aorta and a polymeric film were layered and placed between the blades of the Harmonic Scalpel. Then the samples were gripped with 20 kgf of force for 1-10 s to adhere the porcine aorta and polymeric films. The adhesion was characterized by macro- and microscopic observation, thermographic analysis, and measurement of bonding strength, static contact angle (SCA), and surface properties. RESULTS: Cellulose, vinylon, polyethylene terephthalate, nylon, and Pellethane could be bonded to the aorta. Bonding was not observed for the polyethylene, polypropylene, polyvinyl chloride, or polytetrafluoroethylene. This suggests that the existence of functional groups such as hydroxyl, carbonyl, carboxyl, and amide groups in the polymer structure are key factors in adhesion. Harmonic Scalpel modification of the polyethylene surface during corona discharge treatment further indicated that the functional groups of the polymers are one of the essential factors for tissue adhesion. The temperatures of adhesion were 90-150 °C for the polymers, and the melting temperatures (Tm) were 193-306 °C. This suggests that adhesion was formed by the interaction between the melted polymer surface and the tissue collagen. CONCLUSION: Both polar functional groups and adequate thermal characteristics are necessary for polymers to bond with tissues. These findings should be useful for the development of novel polymers that can be bonded to living tissues with UAS treatment, which can be applied for endoscopic surgery.

Decellularized porcine aortic intima-media as a potential cardiovascular biomaterial.

OBJECTIVES: The aim of this research is to investigate the histological and mechanical properties of decellularized aortic intima-media, a promising cardiovascular biomaterial. METHODS: Porcine aortic intima-media was decellularized using two methods: high hydrostatic pressurization (HHP) and sodium dodecyl sulphate (SDS). The histological properties were characterized using haematoxylin and eosin staining and Elastica van Gieson staining. The mechanical properties were evaluated using a tensile strength test. RESULTS: The structure of the HHP-treated samples was unchanged histologically, whereas that of the SDS-treated samples appeared structurally loose. Consequently, with regard to the mechanical properties of SDS-decellularized intima-media, elastic modulus and tensile strength were significantly decreased. CONCLUSIONS: The decellularization method affected the structure and the mechanical properties of the biomaterial. The HHP-treated sample was structurally and mechanically similar to the untreated control. Its mechanical properties were similar to those of human heart valves and the iliac artery and vein. Our results imply that porcine aortic intima-media that is decellularized with HHP is a potential cardiovascular biomaterial.

Fabrication of a heparin-PVA complex hydrogel for application as a vascular access.

A high hydrostatic pressure method, which can apply over 600 MPa pressure was employed for preparing a hydrogel of poly(vinyl alcohol) (PVA) loaded with heparin. The aim of this study was to fabricate a heparin-PVA hydrogel conduit and evaluate its potential for vascular access. Heparin-PVA complex hydrogel showed suppressed heparin release and prevented clot formation, depending on the molecular weight of the PVA. Strength of the hydrogel conduit was increased by embedding a Dacron mesh between two PVA layers. The tubular heparin-PVA complex hydrogel displayed a burst pressure of 750 mmHg. The tubular heparin-PVA complex hydrogel did not show any occlusion or burst for 2 weeks after implantation, implying that this heparin-PVA complex hydrogel shows high potential for use as a vascular access. This is the first report on the preparation of a multilayered PVA hydrogel with heparin embedded on one side only. The proposed approach could be expanded to the fabrication of various biomaterials for specific purposes.

Successful treatment by fibrin glue sealant for pneumothorax with chronic GVHD resistant to autologous blood patch pleurodesis.

Pneumothorax associated with chronic graft-versus-host disease (cGVHD) after stem cell transplantation is a rare complication. Autologous blood has been used successfully for pleurodesis, which was less toxic than chemical agents. However, when pneumothorax is resistant to pleurodesis, no other procedure is more effective and conservative. Here, we describe a case of myelodysplastic syndromes complicated with cGVHD-related pneumothorax. His pneumothorax has been resistant to pleurodesis using autologous blood and was treated successfully with fibrin glue sealant. In our limited experience, we believe the best success could be achieved when this method is used to treat persistent pneumothorax with cGVHD.