1：Experimental Design and Method Selection:

The overall design involves a sandwich-type aptamer sensing interface where a chitosan-modified CdS:Mn/TiO2/ITO electrode immobilizes capture DNA (S1). In the presence of target protein (thrombin), AuNPs-labeled DNA (AuNPs-S2) binds to form a sandwich structure, inducing energy transfer (ET) and steric hindrance effects that quench photocurrent. Theoretical models include ET between CdS:Mn and AuNPs, and photoelectrochemical principles.

2：1). In the presence of target protein (thrombin), AuNPs-labeled DNA (AuNPs-S2) binds to form a sandwich structure, inducing energy transfer (ET) and steric hindrance effects that quench photocurrent. Theoretical models include ET between CdS:

2. Sample Selection and Data Sources: Thrombin is used as the target protein. Oligonucleotides (S1 and S2) are synthesized with specific sequences. Real samples include human serum from The First Affiliated Hospital of Zhengzhou University, diluted 100-fold.

3：Sample Selection and Data Sources:

3. List of Experimental Equipment and Materials: ITO slices (type JH52), TiO2 powder (P25), Cd(NO3)2?4H2O, Na2S?9H2O, Mn(Ac)2?4H2O, chitosan, glutaraldehyde, BSA, ascorbic acid, AuNPs synthesized from HAuCl4 and sodium citrate, oligonucleotides from Sangon Biotechnology. Equipment: PEAC200A photochemical reaction apparatus, RST5210F electrochemical workstation, SEM (JEOL JSM-6700), EDS (Oxford Inca Energy 400), UV-Vis spectrometer (Lambda 35), three-electrode system (ITO working electrode, Pt counter electrode, Ag/AgCl reference electrode).

4：List of Experimental Equipment and Materials:

4. Experimental Procedures and Operational Workflow: (a) Prepare AuNPs-S2 by synthesizing AuNPs and conjugating with S2 DNA. (b) Prepare modified electrode: clean ITO, coat with TiO2 suspension, sinter, deposit CdS:Mn via SILAR method. (c) Fabricate PEC aptasensor: treat electrode with chitosan and glutaraldehyde, immobilize S1, block with BSA. (d) Measurement: incubate with thrombin and AuNPs-S2, measure photocurrent in PBS with AA using white light illumination (400-700 nm) at 0.0 V potential with 10 s on/off intervals.

5：Experimental Procedures and Operational Workflow:

5. Data Analysis Methods: Photocurrent responses are recorded and analyzed to determine the relationship with thrombin concentration. Linear regression is applied to the decrement of photocurrent vs. logarithm of concentration. EIS and SEM/EDS are used for characterization. Statistical analysis includes recovery and RSD for real sample validation.