An electrochemical biosensor based on glyco-conjugated Cu-BTC MOFs for voltammetric detection of bacteria

Abstract

Foodborne illnesses pose a significant public health challenge globally. According to WHO estimates, unsafe food causes approximately 600 million cases of foodborne diseases annually. Bacterial pathogens, including E. coli and P. aeruginosa, are significant contributors, causing illnesses ranging from mild gastrointestinal issues to severe, life-threatening conditions. E. coli can lead to severe gastrointestinal diseases, while P. aeruginosa poses risks in high-moisture foods due to its biofilm formation and antimicrobial resistance. Effective detection of these pathogens is vital for ensuring food safety and preventing outbreaks. This study reports the synthesis of a monosaccharide sugar-conjugated Cu-BTC bioprobe for the electrochemical detection of lectin and bacteria via classical carbohydrate-lectin interactions. Cu-BTC was drop casted onto a screen-printed carbon electrode (SPCE) and covalently linked with sugar via carbodiimide chemistry. In this easy-to-synthesize bioprobe, the Cu-BTC metal–organic framework acted as a redox mediator, while the monosaccharide sugar molecules served as bioreceptor elements. The developed 4APM@Cu-BTC/SPCE and 4APG@Cu-BTC/SPCE bioprobes exhibited significant voltammetric responses, achieving detection limits of 2461 CFU per mL and 84.68 CFU per mL towards E. coli and P. aeruginosa, respectively, with a quick response time of <15 min. At the same time, the synthesized bioprobes also proved to be effective in the detection of lectins such as concanavalin A and PA-1. Besides, the covalently bound monosaccharide sugars facilitated the selective interaction of bioprobes with the corresponding analytes while eliciting negligible responses towards common biological interferents. Moreover, the fabricated bioprobes were applied for the detection of bacterial species in spiked milk and juice samples and showed satisfactory recovery percentages of ca. 80–91% and 78–93% for E. coli and P. aeruginosa, respectively. This work provides a new approach for the advancement of a carbohydrate-based electrochemical sensing platform. By eliminating the need for an external redox mediator and utilizing a cost-effective, sensitive, and readily accessible bioreceptor, the sugar-modified Cu-BTC framework offers a promising sensing strategy. Additionally, owing to their in-built non-genetic information and involvement in host–pathogen interaction, carbohydrates can enhance their utility in sensing applications.