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A pH sensor for non-invasive in vivo detection and imaging of implant associated
infection
Unaiza Uzaira, Donald Benzaa,c, Fenglin Wanga, Yash Ravalb, Tzuen-Rong J.Tzengb and Jeffrey
N.Anker a
a
Department of Chemistry, Center for Optical Materials Science and Engineering (COMSET)
and Environmental Toxicology Program, bDepartment of Biological Sciences, cDepartment of
Electrical and Computer Engineering, Clemson University, SC, United States
Background and Objective: We develop a pH sensor based on the use of X-ray Excited
Luminescence Chemical Imaging (XELCI) to non-invasively diagnose and monitor implantassociated infection in situ. Early diagnosis of implant-associated infection and noninvasive
continuous monitoring of infection is a challenge and treatment is highly dependent on the
detection of infection at its onset.
Methods: Our pH sensor uses a combination of X-ray excited optical luminescence and pHdependent optical absorption to detect pH changes through tissue. Bacteria and inflammatory
responses cause a pH drop in affected area and pH shifts to acidic from physiological pH which
can indicate infection.
Results: The pH sensor is characterized for reversibility, sensitivity and resolution. We studied pH
changes during formation of biofilm on the pH sensor in vitro. We also tested the pH sensor in
animal model and cadaver studies.
Discussion and Conclusions: XELCI provides high spatial resolution images mainly limited by Xray beam width with minimum increase from X-ray scattering in tissue. It allows point by point
mapping of the surface with minimum background. In summary, our sensor provides a novel
approach to non-invasively image surface pH to diagnose implant infection and assess treatment.
Acknowledgements: This research was supported in part by National Science Foundation (NSF)
CAREER award CHE1255535, a Fulbright Scholarship award to Unaiza Uzair, and animal studies
funded through the South Carolina Bioengineering Center of Regeneration and Formation of
Tissues (SCBioCRAFT) funded under NIH grant R15EB014560-01A1.