Biological Metal–Organic Framework-Embedded MXene Nanocomposite as a Wearable Transducer Patch for Real-Time Monitoring of the Sleep Hormone

Sleep is an inherent property of human beings, and it is mainly associated with the sleep hormone melatonin (MEL). Abnormal levels of MEL can lead to disorders like hypertension, stress, dementia, Alzheimer's disease, etc. Therefore, continuous monitoring of this hormone is of great concern. In this study, we have developed a sensing platform by combining Nb2CTx MXene nanosheets with a zinc-based metal–organic framework (Zn-MOF). The MOF was synthesized using a zinc ion as the metal part and l-glutamic acid as the organic linker. Because the linker itself is a biological molecule, the synthesized MOF can be denoted as bio-MOF as a whole. This novel composite (Zn-MOF-Nb2CTx MXene) offers enhanced electrocatalytic properties, improved electrical conductivity, and increased active sites, making it well-suitable for the electrochemical detection of MEL. Notably, the inlay of MOF nanoflakes onto the MXene nanosheets created a synergistic effect that greatly enhanced the electrochemical performance for MEL detection. The sensor made of a Zn-MOF-Nb2CTx MXene nanocomposite coated on carbon yarn (CY) exhibited a wide linear detection range for MEL, spanning from 1 to 100 μM, with a detection limit of 215 nM. Importantly, it displayed high selectivity against interfering compounds commonly encountered in body fluids. Also, to check the practical applicability of the sensor, we tried the detection of MEL in biological fluids like sweat, blood serum, and cerebrospinal fluid (CSF) to prove its practicability in real-time medical scenarios. Notably, the use of CY as the electrode material opens the door for its potential integration into a band-aid to make a wearable and point-of-care device for current health sector applications.