Temperature-responsive fluorescent polygalacturonic acid: a step towards wound monitoring with smartphone imaging

Abstract

An increase in the temperature at the wound site is an early indication of a disturbance in the healing process and a sign of an infection. Different polymeric materials have been employed in wound dressing, including polygalacturonic acid (PGA). In this study, we complexed PGA to poly(phenylene ethynylene) (PPE-CO₂-108) to develop a fluorescence-based thermal sensor for solution and dry polymer film applications. The thermal sensor sensitivity and reversibility were tuned by changing the concentration of PGA and the solution ionic strength. As a result, we were able to create a highly reversible thermal sensor and by simply altering the ionic strength, we developed a sensor with long-lasting temperature memory. In solution, the macromolecule complexes had an absolute sensitivity of 0.013 °C⁻¹ (20–40 °C) and 0.029 °C⁻¹ (45–90 °C) when prepared in 150 mM NaCl. In the absence of NaCl, the sensor had a wider range, and its absolute sensitivity increased to 0.044 °C⁻¹ (20–90 °C). The sensor was also prepared into dried thin materials to mimic a wound suture with good thermal sensitivity over physiologically relevant temperatures. The calculated absolute sensitivity was equal to 0.011 °C⁻¹ between 25 and 55 °C. Using a home-developed app, we were able to accurately measure the temperature of these films. As such, our formulated PGA materials have the potential to be developed into smart sutures to monitor early signs of wound infection.