Multisignal Amplification On–Off–On Strategy via Integrating the Pore Release of Polymetallic MOFs with Perovskite QDs to Induce Dual Photocurrent Polarity Reversals for an Ultrasensitive and Wide-Range Photoelectrochemical Precise Assay

A multisignal amplification on–off–on strategy was designed to facilitate a swift and accurate photoelectrochemical (PEC) assay of cardiac troponin I (cTnI), a biomarker universally acknowledged as the "gold standard" for diagnosing acute myocardial infarction (AMI). This approach combined the pore-channel release of polymetallic MOFs with the exceptional PEC properties of perovskite QDs. Hemin was encapsulated within pores of CuRu MOFs, while aptamers were immobilized on the CuRu MOF surface via electrostatic forces, effectively blocking pore channels. Upon the introduction of cTnI, the aptamers specifically bound to it and dissociated from the CuRu MOF surface, thereby enabling the efficient release of Hemin from the pore channels of CuRu MOFs even at low cTnI concentrations. Consequently, an amplified reversal response of stable cathodic photocurrent was generated, leading to a significantly reduced detection limit. The attachment of biofunctionalized Cs3Bi2Br9 QDs triggered a secondary cooperative signal inversion to produce an anodic photocurrent, further amplifying the PEC response. Through these novel design elements, a multisignal amplification on–off–on assay platform was successfully constructed by inducing dual photocurrent polarity reversals. This unique signal amplification not only significantly enhanced the sensitivity (a low detection limit of 4.3 pg/mL) but also remarkably extended the linear range (5 pg/mL to 10 μg/mL) across 6.5 orders of magnitude. Such performance proved to be highly suitable for the direct and accurate quantification of cTnI in serum samples from AMI patients without the need for dilution. As a result, the proposed method enabled a clear differentiation between positive and negative clinical samples, thereby substantially expanding the application potential of analytical chemistry in clinical diagnosis.