of patients in need of such surgery, which can significantly improve one's quality of life. [1] Unfortunately, orthopedic implants are highly susceptible to peri-implant sterile inflammation or microbial infections (prosthetic joint infections, PJI). These complications, which manifest as pain, erythema, swelling and discharge from the wound site, require long hospitalizations and can lead to osteomyelitis, implant failure, sepsis, multiorgan dysfunction, amputation or even death. [2,3] PJI occur in 1-2% of primary arthroplasty surgeries and up to 4% of revision arthroplasty surgeries. [4] Traditionally, PJI are classified as early (<3 months after surgery), delayed (3-24 months after surgery), or late (>2 years after surgery). [5] The sources of bacterial infection might be the operating room and surgical equipment, bacteria from the patient's skin, and bacteria that already reside in the patient's body. Early and acute infections are usually preceded by a systemic infection such as sepsis or soft-tissue infection. [6] The origins of chronic infections are either exogenous or hematogenous. [7] Implant-associated infections are the result of bacterial adhesion to an implant surface and subsequent formation of biofilm at the implantation site. [8][9][10] According to the surveillance European Centre for Disease Prevention and Control report from 2017, the The local peri-implant pH changes caused by sterile inflammation and bacterial and fungal infections are studied herein. Then, a sensing electrode based on polyaniline and poly(2-methyl-2-oxazoline) on a titanium alloy support is developed for potentiometric detection of peri-implant pH changes to enable early detection of the aforementioned pathologies. The infected endoprosthesis area is shown to have an average pH of 0.79 units lower than the aseptic sample. The pH measurements of the individual pathogenic bacteria or pathogenic yeast reveal that Escherichia coli decreased the pH by 1.24 units, Staphylococcus aureus decreased the pH by 1.33 units and the methicillin-resistant Staphylococcus aureus bacteria decreased the pH from 7.2 to 5.6 during 10 h, followed by a subsequent increase to 6.4. The results are statistically significant (α = 0.01). Pseudomonas aeruginosa is not shown to change pH levels. On the other hand, the pathogenic yeast has the lowest recorded pH, which decreases from 5.8 to 4.8. This difference in pH can be used to identify the nature of the infection. The developed electrodes have a pH response between pH 5 and 8, with a Nernstian slope of −59.6/pH. The developed electrode can contribute to the next generation of biosensors.
