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Issue 9, 2019
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An implanted pH sensor read using radiography

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A biomedical sensor was developed to measure local pH near orthopedic implants to detect and study implant-associated infection. The sensor is read using plain radiography, a technique which is noninvasive, inexpensive, ubiquitously available in medical facilities, and routinely used in diagnosis and follow-up. The sensor comprises a radiopaque tungsten indicator pin embedded within a chemically responsive hydrogel that exhibits a pH-dependent swelling. A stainless steel well holds this hydrogel and attaches to an orthopedic plate. The local pH may be determined from the extent of hydrogel swelling by radiographically measuring the indicator position relative to the well. We calibrated the sensor in a series of standard pH buffers and tested it during bacterial growth in culture. The sensor was robust: its response was negligibly affected by changes in temperature, ionic strength within the normal physiological range, or long-term incubation with reactive oxygen species generated from hydrogen peroxide and copper. Pooled data from several sensors fabricated at different times and tested in different conditions had a root-mean-square deviation from a pH electrode reading of 0.24 pH units. Radiographic measurements were also performed in cadaveric tissue with the sensor attached to an orthopedic plate fixed to a tibia. Pin position readings varied by 100 μm between observers surveying the same radiographs, corresponding to 0.065 pH units precision in the range pH 4–8. The sensor was designed to augment standard radiographs of tissue, bony anatomy, and hardware by also indicating local chemical concentrations.

Graphical abstract: An implanted pH sensor read using radiography

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The article was received on 02 Dec 2018, accepted on 27 Feb 2019 and first published on 19 Mar 2019

Article type: Paper
DOI: 10.1039/C8AN02337A
Citation: Analyst, 2019,144, 2984-2993

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    An implanted pH sensor read using radiography

    Md. Arifuzzaman, P. W. Millhouse, Y. Raval, T. B. Pace, C. J. Behrend, S. Beladi Behbahani, J. D. DesJardins, T. J. Tzeng and J. N. Anker, Analyst, 2019, 144, 2984
    DOI: 10.1039/C8AN02337A

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