A novel injectable BRET-based in vivo imaging probe for detecting the activity of hypoxia-inducible factor regulated by the ubiquitin-proteasome system

The ubiquitin-proteasome system (UPS) is a selective protein degradation system that plays a critical role in many essential biological processes by regulating the existence of various cellular proteins. The target proteins of UPS are recognized and tagged with polyubiquitin chains by E3 ubiquitin ligases, which have high substrate-specific activities. Here we present a novel injectable imaging probe POL-N that can detect the UPS-regulated hypoxia-inducible factor (HIF) activity in vivo. Because the luciferase is fused to the E3 ligase-recognition domain of the HIF-1α, POL-N is intact only in the HIFα-overexpressing cells, that is, HIF-active cells, generating signals via an intramolecular bioluminescence resonance energy transfer (BRET) between luciferase and a near-infrared (NIR) fluorescent dye at the C-terminal end of the probe. Off-target signals of the NIR-BRET were so low that we could achieve highly sensitive and fast detection of intratumoral HIF-activity. Notably, we successfully detected hypoxic liver metastasis, which is extremely difficult to detect by injectable imaging probes due to strong off-target signals, as early as 1 h after systemic injection of POL-N. Our probe design can be widely adapted to UPS-target proteins and may contribute to the exploration of their roles in animal disease models.

Comparison of replacement prostheses for segmental defects of bone. Different porous coatings for extracortical fixation

The extent of extracortical bone-bridging and ingrowth into porous-coated prostheses for the stabilization of segmental defects was studied in a canine model. Initial fixation of the implant was achieved using bone cement. Autogenous bone grafts were applied over the porous-coated segmental portion of the prosthesis to stimulate the ingrowth and formation of bone. At twelve weeks, bone-bridging and ingrowth occurred uniformly in both the titanium fibermesh and the cobalt-chromium-molybdenum beaded prostheses. Maximum formation of osseous tissue over the implants occurred at two to four weeks. More bone formed in the posterior aspect of the prosthesis. At twelve weeks, 26 per cent of the porous space of the titanium fibermesh prosthesis and 47 per cent of the porous space of the cobalt-chromium-molybdenum beaded prosthesis were filled with bone. The torsional strength and stiffness of the prosthetic midsection that contained a conical coupling joint were increased significantly due to bone-bridging and ingrowth. The cortical bone that was apposed to the segmental prosthesis showed an increase in porosity. The use of bone cement did not appear to impede new-bone formation extracortically. The initial stability of the implant and the application of sufficient autogenous bone grafts are two important factors that contribute to the ultimate stable fixation of an implant by extracortical bone formation.

[Experimental study on biomaterials coated with titanium-nitride ceramic for orthopedics]

Ceramic has excellent properties. However, the brittleness of ceramic is one of the major problems. Coating ceramic on stronger substance materials may be one of the ways to overcome this problem. In this study, stainless steel (316L) coated with titanium nitride ceramic (TiN), produced by using a physical vapor deposition method, was investigated. The results indicated that although the yielding strength was decreased by exposing the material to 550 degrees C, the grain structure did not change. Stainless steel with 3.0 micron TiN coating demonstrated high resistance to bending stress and friction. In addition, this material displayed sufficient fatigue strength for an orthopaedic implant after 10(7) loading repetitions. Based on organ cultures and animal experiments, the biocompatibility of TiN coated stainless steel appeared to be superior to uncoated stainless steel. The TiN coating dissolved in H2O2 although it was stable to HNO3. In conclusion, titanium nitride ceramic coated stainless steel appears to be a promising material for implantation. However, further investigation is necessary for a long term results as an implant material.

Clinical experience of Al2O3 ceramics as a surgical implant

The authors have treated 75 patients with various orthopaedic disorders including trauma, degenerative joint disease and tumours with ceramic surgical implants. A short account of the experience gained, together with some illustrative clinical cases is presented. Supplementary laboratory experiments have shown that Al2O3 ceramic material produces minimal changes of boundary reaction with the bone and the material produced no adverse effect upon organ cultures of developing chick femora and tibiae.