ISSN:
0021-9304
Keywords:
tissue response
;
implants
;
sensors
;
vascularity
;
foreign-body response
;
subcutaneous implants
;
PVA
;
PTFE
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
,
Technology
Notes:
The results of two previous studies have shown that implant porosity can be used to increase both the measured diffusion coefficients and the vascularity within the tissue encapsulating long-term subcutaneous implants. This study investigates the hypothesis that the analyte concentrations within the tissue surrounding porous implants will respond more quickly to changes in plasma levels than does the densely packed, avascular fibrous capsule surrounding nonporous implants. The average concentration of lissamine-rhodamine was measured in tissue within 100 μm of the following implants at four different times following injection of the tracer: PVA-skin, PVA-5, PVA-60, PVA-700 (polyvinyl alcohol nonporous, 5 μm, 60 μm, and 700 μm mean pore sizes, respectively) and PTFE-0.5 and PTFE-5 (polytetrafluoroethylene 0.5 μm and 5 μm mean pore sizes, respectively). The results were compared to those of unimplanted subcutaneous tissue (SQ). In addition, the data were analyzed with a simple two-compartment model in which a tissue response time constant (τp) was extracted. As in the case of vascular density, the cellular dimension of the PVA-60 pore sizes produced surrounding tissue with the optimum response times to changes in plasma concentrations. The concentrations of rhodamine within the tissue surrounding the PVA-60 implant were the highest at all time points and responded to the change in plasma rhodamine concentration approximately three times more quickly (τp = 764 s) than the fibrous tissue encapsulating the nonporous PVA-skin (τp = 2058 s) and more than twice as quickly as SQ (τp = 1627 s). The overall mass transfer rate between plasma and the tissue surrounding the different implants calculated from the permeability and density of vessels from the previous study correlated very well (r2 = 0.7, p 〈 .02, slope of 0.98) with the reciprocal of the tissue response time constant (τp). © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 598-605, 1998.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
