The potential use of colorimetric pH sensor from Clitoria ternatea flower for indicating bacterial infection in wound dressing application

Treatment of chronic wounds requires good monitoring for the wound infection. One of the indicators for the infected wound is the change of pH values around the wound area. In this study, the visual pH sensor from Clitoria ternatea (CT) flower was used to indicate the pH value and evaluate the wound status. The CT extract contains anthocyanins which are pigments that appear in different colors depending on the pH values. The color of CT extract at pH values ranges from 2.0 to 12.0 was investigated by the UV–vis spectrophotometer and the naked eye. The antioxidant activity, antibacterial activity, and cytotoxicity of CT extract were evaluated for their biological activities. The concentration of CT extract that can scavenge 50% of DPPH free radicals was 0.80 mg/mL. Besides, the CT extract showed non-toxic to NCTC clone 929 cells. However, the CT extract demonstrated low inhibition of S. aureus, E. coli, P. aeruginosa, and S. epidermidis bacteria. Also, the CT extract was loaded on the paper to observe the color changes in bacterial solutions. The color changed from blue-purple to blue-green color in bacterial solutions indicating the wound infection. Therefore, the natural dyes extracted from the CT flower had the potential to apply for colorimetric pH sensor in wound dressing application.