ABSTRACT
Electron paramagnetic resonance (EPR) oximetry is a powerful technology that allows the monitoring of oxygenation in tissues. The measurement of tissue oxygenation can be achieved using lithium phthalocyanine (LiPc) crystals as oxygen reporters. In order to have biocompatibility for the sensing system and to assure long-term stability in the responsiveness of the system, we developed films of Teflon AF 2400 with embedded LiPc crystals. These systems can be used as retrievable inserts or parts of an implantable resonator or catheter. Atomic force microscopy studies revealed that the surface of the films was regular and planar. The response to oxygen of the sensor (EPR linewidth as a function of pO(2)) remained unchanged after implantation in mice, and was not affected by sterilization or irradiation. The use of resonators, holding LiPc embedded in Teflon AF 2400, implanted in the gastrocnemius muscle of rabbits allowed the monitoring of oxygen during several weeks. Several assays also demonstrated the biocompatibility of the system: (1) no hemolytic effect was noted; (2) no toxicity was found using the systemic injection test of extracts; (3) histological analysis in rabbit muscle in which the films were implanted for 1 week or 3 months was similar to standard polyethylene biocompatible devices. These advanced oxygen sensors are promising tools for future pre-clinical and clinical developments of EPR oximetry. These developments can be applied for other applications of biosensors where there is a need for oxygen permeable membranes.
Subject(s)
Biosensing Techniques/instrumentation , Electron Spin Resonance Spectroscopy/methods , Indoles/chemistry , Muscle, Skeletal/blood supply , Muscle, Skeletal/metabolism , Organometallic Compounds/chemistry , Oxygen/blood , Polytetrafluoroethylene/chemistry , Absorption , Animals , Biocompatible Materials/analysis , Biocompatible Materials/chemistry , Biosensing Techniques/methods , Crystallization/methods , Equipment Design , Equipment Failure Analysis , Indoles/analysis , Membranes, Artificial , Mice , Organometallic Compounds/analysis , Polytetrafluoroethylene/analysis , Prostheses and Implants , Rabbits , Surface PropertiesABSTRACT
This article describes an EPR spectrometer specifically designed and constructed for EPR spectroscopy in humans. The spectrometer is based on a permanent magnet, suitable for measurements at 1200 MHz. The magnet has a full 50 cm gap between the poles, which facilitates accurate and comfortable placement of the subject for the EPR measurement at any location on the human body. The bridge includes features to facilitate clinical operations, including an indicator for phasing of the reference arm and a 2 level RF amplifier. Resonators with holders for each type and site of measurement have been developed that comfortably position the resonator and the patient and prevent artifacts due to motion. The initial applications for which the spectrometer has been designed are for oximetry using loops on the surface, oximetry using implanted resonators for measuring deep sites, and measurements in the teeth for determination of exposures to clinically significant doses of ionizing radiation.
Subject(s)
Electron Spin Resonance Spectroscopy/instrumentation , Oximetry/instrumentation , Radiometry/instrumentation , Electron Spin Resonance Spectroscopy/methods , Equipment Design , Equipment Failure Analysis , Humans , Oximetry/methods , Radiation Dosage , Radiometry/methodsABSTRACT
A 48-year-old woman and a 61-year-old man were treated for pathologic fractures of the cervical vertebral bodies that caused neurologic defect. In both patients an anterior decompression was performed with the removal of the diseased vertebrae. Immediate stability was obtained with a bone bolt imbedded in methylmethyacrylate. Both patients are functioning satisfactorily without any external support of the cervical spine four years and one and one-half years after their respective operations. This method is applicable only in carefully selected cases.
