3D Printed, Stand-alone, Colourimetric Indicator Strip (3DCIS) for Non-Invasive, On-demand Chronic Wound Monitoring

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Chronic wounds have been referred to as the 'silent epidemic' that affects a significant proportion, 1-2 %, of the population during their lifetime. The main causes of chronic wounds are: diabetes, burns and pressure ulcers and, as the term 'chronic' suggests, they are not readily cured. Thus, in a recent study almost 42% of leg/foot ulcers had not healed in the previous 6 months and 28% had remained unhealed for a year or longer. In all countries, chronic woundcare places a considerable burden upon the local and national health services. For example, in the UK, some 650,000 patients suffer from some form of chronic wound, resulting in an annual cost of ca. £3 Bn, and in the USA there are about 6.5 M suffers, whose treatment costs ca. £25 Bn pa. Venous ulcers, which usually occur in the legs, account for 70-90% of chronic wounds and mostly affect the elderly. It follows that since the global average life expectancy continues to rise then so too will the number of incidences, and cost, of treatment of chronic wounds. The combined cost to the NHS for their treatment reaches approximately £3 billion per year. There is a clear need for an inexpensive, disposable wound monitoring method that can be: (i) readily incorporated into a wound dressing, thereby rendering it smart and, (ii) able to provide clinicians, nurses and patients with a continuous, or semi-continuous, stream of information about key biomarkers, i.e. biochemical cues, which would help identify the condition/status of the wound and so flag up wounds that are not healing properly and that require medical intervention. The proposed technology involves the 3D printing of a multi-analyte strip, comprised of four different colour-based indicators which are selective in response to four different gaseous bio-markers, namely: CO2, volatile amines (RNH2), humidity (H2O) and O2. This strip will provide a semi-continuous, on-demand, stream of information concerning the composition of the headspace above the wound and contained by the dressing. The proposed multi-analyte, in situ, volatile analysis, afforded by this simple, stand-alone, colour strip, has a number of advantages compared to existing wound monitoring methods, which include: (1) complete strip production using 3D printing technology, (2) simple colour changes that can be read by eye or digital camera, (3) simple to incorporate into an existing wound dressing (i.e. stand-alone), (4) easy to interpret, (5) logged data trends and automatic real-time alerts (6) inexpensive, (7) non-contact/non-invasive, (8) applicable in a wide number of healthcare environments (including: point of care, outpatients, hospital wards and home care), (9) scope for application in other areas, both medical, such as in acute wound dressings, and non-medical, such as food and electronic goods packaging, (10) amenable to microfabrication and (11) scope for other analytes to be added, such as temperature and volatile sulfides.