Elizabeth M. Christenson

Biomaterial adherent macrophage apoptosis is increased by hydrophilic and anionic substrates in vivo

An in vivo rat cage implant system was used to identify potential surface chemistries that prevent failure of implanted biomedical devices and prostheses by limiting monocyte adhesion and macrophage fusion into foreign-body giant cells while inducing adherent-macrophage apoptosis. Hydrophobic, hydrophilic, anionic, and cationic surfaces were used for implantation. Analysis of the exudate surrounding the materials revealed no differences between surfaces in the types or levels of cells present. Conversely, the proportion of adherent cells undergoing apoptosis was increased significantly on anionic and hydrophilic surfaces (46 ± 3.7 and 57 ± 5.0%, respectively) when compared with the polyethylene terephthalate base surface. Additionally, hydrophilic and anionic substrates provided decreased rates of monocyte/macrophage adhesion and fusion. These studies demonstrate that biomaterial-adherent cells undergo material-dependent apoptosis in vivo, rendering potentially harmful macrophages nonfunctional while the surrounding environment of the implant remains unaffected.

Reusable Laryngeal Mask Airways can be used more than 40 times

STUDY OBJECTIVE To compare the mechanical properties of classic, reusable Laryngeal Mask Airways (LMAs) that have been used more than 100 times with one unused LMA. DESIGN Laboratory testing of devices used clinically. SETTING Metropolitan university hospital. MEASUREMENTS Cuff and tube specimens from LMAs that had been used at least 100 times were tested for elongation, tensile strength, stiffness, and tear strength using standard American Society of Testing and Materials protocols. Samples from an unused LMA were analyzed in the same manner for comparison. MAIN RESULTS Tensile strength of the cuff samples was found to increase by approximately 25%. There was an increase in cuff stiffness and decreased tear strength similar to the manufacturer-reported trends. Cuff elongation decreased by 30%. Results for the LMA tube differed depending on whether the samples were taken in the machine direction or transverse direction. Tensile strength decreased by 30% in machine direction and, on average, very little in transverse direction. CONCLUSIONS The material in reusable classic LMAs does not lose its strength after 100 uses to the extent that its manufacturer claims. At least 100 uses may be considered safe for these devices.