Electrocatalytic Self-Sterilizing PEG@Mn-Ti3C2Tx MXene Biosensor with Dual Antifouling Capability for Ultrasensitive Detection of Cardiac Troponin I

Electrochemical sensing devices often suffer from biofouling due to nonspecific adsorption of biomolecules and microorganisms in complex biological matrices. To address this challenge, we developed an efficient antifouling and self-sterilizing sensing interface by grafting polyethylene glycol (PEG) onto two-dimensional Ti 3 C 2 T x MXene nanosheets for the accurate detection of cardiac troponin I (cTnI), a gold-standard biomarker for acute myocardial infarction (AMI). The Mn 2+ -intercalated Ti 3 C 2 T x (Mn-Ti 3 C 2 T x ) exhibited enhanced electrochemical activity in a three-electron oxygen reduction reaction (3e - ORR), enabling in situ self-sterilization by activating molecular oxygen to generate hydroxyl radicals (•OH), which demonstrated potent antibacterial effects against both Gram-negative and Gram-positive bacteria. Density functional theory calculations revealed that Mn doping in MXene significantly reduced the free energy barrier of *OOH intermediate, promoting H 2 O 2 formation and subsequent reduction to •OH. The PEGylated Mn-Ti 3 C 2 (PEG@Mn-Ti 3 C 2 T x ) composite combined the superior hydrophilicity of PEG for effective protein repulsion with the enhanced conductivity of Mn-Ti 3 C 2 T x , enabling sensitive biosensing. Critically, the fabricated biosensor demonstrated high specificity for cTnI against common interferents and achieved reliable detection in spiked serum samples. It exhibited a broad detection range from 0.1   pg   mL -1 to 500   ng   mL -1 with an ultralow limit of 0.03   pg   mL -1 . This work presents a novel strategy for combating biofouling and paves the way for designing robust biosensors capable of accurate and long-term operation in clinically relevant environments, holding great promise for point-of-care diagnostics.