Silver-dendrites modified laser induced graphene electrodes as a handheld electrochemical non-enzymatic sensor device for onsite salivary urea detection

Salivary urea quantification offers a noninvasive alternative to the commonly used blood urea nitrogen estimation for CKD diagnosis. Furthermore, this confers ease of detection to non-skilled personnel and is pertinent to public screening. However, such screening programs require point-of-care diagnostic platforms to facilitate rapid and user-friendly diagnosis. To this end, we report the fabrication and development of silver dendrite-modified LIG (Ag-LIG) sensors for electrochemical, non-enzymatic urea sensing from minimally processed human saliva. The developed Ag-LIG sensor demonstrated appreciable reproducibility (RSD <7%), low limit of detection of 26 μM, high selectivity, confirmed by excellent recovery traits of more than 91% in urea spiked in simply diluted saliva samples, appreciable stability for 31 days, and exhibited linear range encompassing clinically relevant (healthy/diseased) concentrations of salivary urea. Furthermore, the sensor facilitates rapid detection in ∼2 min, is readily integrable with smartphones, and is easily operable without any prior training. Additionally, the real-time applicability of the Ag-LIG sensors was comprehensively validated by comparing their performance with that of the gold standard method, wherein the salivary urea measurements using the sensors exhibited an excellent degree of agreement with the former (CI 95%). Furthermore, user surveys and testing by untrained volunteers provided results with high accuracy and precision, like those obtained by trained chemists, thus demonstrating its ease of use. Finally, the cost per sensor was calculated to be a meagre 0.08 $, which is 40-80 times cheaper than existing commercial products, thereby emphasizing its immense economic benefits and lab-to-market translatability.