Microdiamond-embedded Silk: A Hybrid Platform for Temperature Monitoring in Wounds

Timely determination of infection within wounds is crucial for avoiding spread of infectious bacteria, which can lead to further complications including sepsis. Current clinical methods of determining infection, while accurate, are intrusive and painful. Alternative visual identification methods, though less invasive, may lack precision. Both methods require the removal of the wound dressing, which is painful for the patient and time consuming for the clinician. However, early indications of infection can be inferred through monitoring of local area temperatures within a wound, which may show an increase of 3 to 5 deg C when an infection is present. This study proposes a novel approach that integrates temperature sensors within a biocompatible scaffold, creating a hybrid wound dressing for non-contact thermometry of a wound site, providing a method of infection inference without the need for dressing removal. Unlike reported wound dressing sensing methods in the literature, the method for temperature inference does not require complex electronics, and maintains characteristics of a modern wound dressing to ensure ideal healing conditions. This differentiates it from other reported wound dressing sensing methods in the literature which frequently utilise flexible PCB methods with onboard communication systems to interface with, and do not provide fluid absorption or permeability capabilities that promotes an ideal wound healing environment. The reported hybrid dressings consist of two main components; optical sensors which are embedded within a biocompatible and transparent silk fibroin scaffold. The utilised optical sensors are micron-sized fluorescent diamond which have been irradiated and processed to contain highly photostable and temperature sensitive nitrogen-vacancy centres. Local temperature is measured through the fluorescence-based method of Optically Detected Magnetic Resonance (ODMR), enabling rapid measurement of temperature through the transparent silk dressing to infer infection without the need for dressing removal. These sensors are embedded within a biocompatible and biodegradable silk scaffold, that is surface conformable, low cost to manufacture, and can be modified to match the surface properties of commercial wound dressings. The mechanical and surface properties of the fabricated dressings were compared with commercial dressings,indicating suitability for low-exudate environments akin to clinical ‘second-skin’ products. The temperature sensing capabilities of the wound dressing were studied in an artificially heated environment as well as an in-vivo context to determine the feasibility of such a sensing platform. These studies determined that temperature sensing utilising this method on a biological system can be completed, however methods for optimising the measurement system for inaccuracies due to inherent optical heating are required. Methods to mitigate this were explored and implemented. In summary, this work has presented a wound dressing that is capable of non-invasive temperature monitoring while maintaining ideal healing conditions. This protocol for fabricating such a dressing has been developed, and its sensing capability benchmarked in an in-vivo context. However, improvements of the optical measurement system to record temperature measurements spatially are still to be completed. Future work on the sensing platform will focus on improving the optical measurement system for spacial measurement of temperature, and integrate a pH sensitive material into the dressing for multimodal sensing.