Authors’ contributions MMR, LFM, and JFB designed the experiment and analyzed and discussed the results. MMR fabricated the NAA-based DBR and performed the optical characterization. All authors redacted and revised the manuscript. All authors read and approved the final manuscript.”
“Background There is a need to develop

rapid and biocompatible pH sensors to monitor changes in the wound-healing trajectory that are, for example, caused by bacterial infection or biofilm formation. Chronic wounds do not heal within 3 months, and are considered an important and costly medical issue in Dinaciclib ic50 the world’s aging societies, imposing considerable pain, reduced mobility and decreased quality of life on the sufferers [1]. During the lengthy healing process, the wound is invariably exposed to bacteria that can colonize the wound bed and form biofilms. This alters the wound metabolism and brings about Ilomastat mw a change of pH [2]. Several recent studies have demonstrated an oscillation of the pH between 5.4 and 9, during a bacteria infection in the wounds [2, 3].

Recently, significant DNA Damage inhibitor research efforts have been devoted to pH sensors for the detection of pH variation in wound fluid [1]. These are typically based on dyes [4, 5] or on inductive transducers [6] incorporated into wound dressings. For example, Trupp et al. have synthesized a series of hydroxyl-substituted azobenzene derivatives as indicator dyes for optically monitoring pH between 6 and 10 [4]. However, there are concerns over the biocompatibility of these dyes. Sridhar and Takahata have O-methylated flavonoid developed a micro-fabricated wireless pH monitor involving a pH-sensitive hydrogel intended to be imbedded

into a wound dressing to track pH wirelessly. The authors observed changes in moisture level in a wound dressing in the pH range 2 to 7 [6]. The cost of this device may be a limiting factor for reduction to practice. Simultaneously, materials with optical features such as the porous silicon (pSi) have been associated with pH-responsive polymers in order to detect variation of pH [7–9]. PSi is an attractive candidate to use as a sensor in contact with wound fluid because the material is highly biocompatible and well tolerated in vivo, even when implanted into the eye [10]. The material displays strong thin-film interference effects, which result in the appearance of Fabry-Pérot interference fringes [11]. In turn, multilayers of pSi of alternating high and low refractive indices result in a sharp photonic resonances [11]. Changes in the effective refractive index of pSi films cause a shift in the interference pattern or the position of the photonic resonance peak in multilayered pSi resonators, respectively [12–15]. Perelman et al. developed a pH sensor based on pSi modified with thermo- and pH-responsive hydrogel poly(N-isopropylacrylamide-co-acrylic acid).