An electrochemical-photothermal platform driven by DNAzyme walker and HCR on MoS2@ZIF-67 heterojunction substrate for ultrasensitive phytopathogen detection.

BACKGROUND: The early and accurate identification of Sporisorium scitamineum, the etiological agent responsible for sugarcane smut, is significantly impeded by the constrained detection limits and inadequate analytical sensitivity of prevailing diagnostic methods. The imperative for precise early-stage pathogen detection is paramount to circumventing epidemic propagation and averting extensive agronomic losses in both cane tonnage and saccharose yield. These exigencies highlight the necessity for a shift in detection strategy. This compels the development of innovative biosensing platforms that transcend the performance ceilings of conventional assays to achieve effective disease management and sustainable sugarcane cultivation.

RESULTS: This work presents a novel dual-mode biosensing platform that integrates a programmable cascaded DNA reaction network with a functional molybdenum disulfide (MoS2)@ZIF-67 heterojunction to achieve ultrasensitive and self-validating detection of plant pathogen biomarkers. The sensing mechanism is built upon a sophisticated biomolecular programming strategy where target pathogen DNA initiates a series of events. A strand displacement reaction triggers rolling circle amplification (RCA) to generate Mg2+-dependent DNAzyme Walker. This dynamic DNA nanomachinery cleaves electrode-bound substrate hairpin DNA (H1), thereby precisely controlling the initiation of hybridization chain reaction (HCR). Without target, HCR proceeds unimpeded, assembling long double-helix chains loaded with a high density of glucose oxidase (GOD) on the electrode. The MoS2@ZIF-67 heterojunction electrode enhances biomolecular loading and electron transfer efficiency via its high surface area and excellent conductivity. This design enables dual-signal output that the GOD-catalyzed oxidation of glucose generates measurable open-circuit voltage, while the subsequent enzymatic product, oxidized TMB (oxTMB), serves as a robust photothermal agent under 808 nm laser irradiation. The bioplatform demonstrates exceptional performance, achieving a detection limit of 27.91 aM for electrochemical mode and 32.14 fM for photothermal mode within a broad linear range.

SIGNIFICANCE: The built-in cross-referencing between the two distinct signal modalities effectively minimizes false positives, ensuring high reliability. Furthermore, coupling the system with a capacitor amplifies the output, boosting sensitivity by 17.4-fold. This research not only provides a powerful tool for plant disease diagnostics but also establishes a versatile and programmable strategy for constructing intelligent biosensing interfaces, highlighting significant potential in sustainable agriculture and advanced bioanalysis.