title: Permeability of subcutaneous tissues surrounding long-term implants to oxygen.
abstract: Certain types of implanted medical devices depend on oxygen supplied from surrounding tissues for their function. However, there is a concern that the tissue associated with the foreign body response to implants may become impermeable to oxygen over the long term and render the implant nonfunctional. We report oxygen flux recordings from electrochemical oxygen sensor devices with wireless telemetry implanted in subcutaneous porcine tissues. The devices remained implanted for up to 13 weeks and were removed with adjacent tissues at specified times for histologic examination. There are four main observations: (1) In the first few weeks after implantation, the oxygen flux to the sensors, or current density, declined to a sustained mean value, having unsynchronized cyclic variations around the mean; (2) The oxygen mass transfer resistance of the sensor membrane was negligible compared to that of the tissue, allowing for a sensitive estimate of the tissue permeability; (3) The effective diffusion coefficient of oxygen in tissues was found to be approximately one order of magnitude lower than in water; and (4) Quantitative histologic analysis of the tissues showed a mild foreign body response to the PDMS sensor membrane material, with capillaries positioned close to the implant surface. Continuous recordings of oxygen flux indicate that the tissue permeability changes predictably with time, and suggest that oxygen delivery can be sustained over the long term.
authors.affiliation: Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA.
authors.forename: Lucas S
authors.initials: LS
authors.lastname: Kumosa
authors.affiliation: GlySens Incorporated, 6450 Lusk Blvd., Suite E-109, San Diego, CA 92121, USA.
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Routh
authors.affiliation: GlySens Incorporated, 6450 Lusk Blvd., Suite E-109, San Diego, CA 92121, USA.
authors.forename: Joe T
authors.initials: JT
authors.lastname: Lin
authors.affiliation: GlySens Incorporated, 6450 Lusk Blvd., Suite E-109, San Diego, CA 92121, USA.
authors.forename: Joseph Y
authors.initials: JY
authors.lastname: Lucisano
authors.affiliation: Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA. Electronic address: dgough@ucsd.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Gough
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation*; D004058:Diffusion; D004129:Dimethylpolysiloxanes / Q000009:adverse effects*; D055664:Electrochemical Techniques / Q000295:instrumentation; D004567:Electrodes, Implanted / Q000009:adverse effects*; D004867:Equipment Design; D005260:Female; D005549:Foreign-Body Reaction / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D008567:Membranes, Artificial; D010100:Oxygen / Q000378:metabolism*; D010539:Permeability; D040521:Subcutaneous Tissue / Q000378:metabolism* / Q000473:pathology; D013552:Swine; D013556:Swine, Miniature; D059015:Wireless Technology / Q000295:instrumentation
chemical_list: D004129:Dimethylpolysiloxanes; D008567:Membranes, Artificial; C013830:baysilon; D010100:Oxygen
keywords: Foreign body response; Long-term implants; Oxygen mass transfer; Tissue permeability