The protonated polymer at pH 3 allows water to soak into the porous layer, giving rise to a shift in the photonic resonance. Conclusions We have developed an optical pH sensor based on a photonic pSi film where a pH-responsive polymeric layer on top of the porous layer modulates ingress of water into the layer. The pH-responsive polymer pDEAEA was chosen, synthesized
by RAFT polymerization, and spin-coated on pSi rugate filters. FTIR spectroscopy, interferometry reflectance spectroscopy, and water contact angle measurements were used to confirm the exclusive presence of the polymer at the external surface of the rugate filter. After exposing the pSi-pDEAEA to water droplets of different pH, the role of the polymer as a barrier was demonstrated in contrast to a control sample lacking the polymer. Penetration of water into the porous layer, associated to a change of color of the sample, only occurred at low pH. Our study therefore GPCR Compound Library cell assay provides proof-of-principle that photonic pSi can be used to detect pH changes in aqueous medium. This sensor can potentially be incorporated into wound dressings and used to report on acidification of chronic wound fluid as a result of bacterial infection through a color change that is visible to the unaided eye. Such a device would provide fast wound diagnostics to practitioners and nurses. Authors’ click here information SPa is research associate at the Mawson Institute from the University of South
Australia. RV is a PhD student at the Mawson Institute from the University of South Australia. WZ is a PhD student at the Key Centre for Polymer Colloids in the School of Chemistry from University of Sydney. SPe is a full professor in the Department of Chemistry from the University of Warwick in UK. NV is a full professor from the Mawson Institute from the University of South Australia. Acknowledgements The authors would
like to thank the Wound Management Innovation CRC (Australia) for providing funding for this work. The authors thank the Australian Nanotechnology Network for providing a travel fellowship. Electronic supplementary material Additional file 1: Porous silicon photonic films. Porous silicon photonic films modified with the pH-responsive polymer poly(2-diethylaminoethyl acrylate) are employed to detect a change in pH, through a color change visible by the unaided eye. (DOCX 203 KB) References 1. Dargaville TR, Farrugia Aspartate BL, Broadbent JA, Pace S, Upton Z, Voelcker NH: Sensors and imaging for wound healing: a review. Biosens Bioelectron 2012, 41:30–42.CrossRef 2. Schneider LA, Korber A, Grabbe S, Dissemond J: Influence of pH on wound-healing: a new perspective for wound-therapy? Arch Dermatol Res 2007, 298:413–420.CrossRef 3. Shi L, Ramsay S, Ermis R, Carson D: pH in the Bacteria-contaminated wound and its impact on clostridium histolyticum collagenase activity: implications for the use of collagenase wound debridement agents. J Wound Ostomy Continence Nurs 2011, 38:514–521. 510.1097/WON.