The authors report a novel electrochemical immunosensor assembled on a commercial graphene-paper electrode coated with a four-armed star poly(glycidyl methacrylate) polymer (FASPGMA). FASPGMA provides multiple linear polymer chains terminated with epoxy side groups that extend from a single branching point. This architecture was used to create a biofunctional layer on the graphene-paper surface intended to present reactive epoxy moieties for covalent antibody attachment.
Different chemical, electrochemical, and morphological tests were performed to follow production of the biosensing layer and to confirm successful modification of the electrode surface. The functionalized electrode platform served as the base for antibody immobilization and subsequent immunosensing of the lung cancer–associated biomarker GM2-activator protein.
The FASPGMA polymer was chosen because its multiple epoxy side groups permit covalent coupling of antibodies directly to the polymer chains. The GM2AP-specific antibodies were attached to epoxy-functional side groups by covalent reaction, eliminating the need for additional coupling reagents or activation steps. This direct immobilization strategy simplifies sensor preparation and aims to produce a stable, oriented bioactive surface for antigen capture.
Surface characterization and chemical analyses (reported broadly as chemical, electrochemical, and morphological tests) were used to validate each step of layer formation and to ensure the antibody-bearing polymer coating was present and active on the graphene-paper electrode.
Analytical detection was achieved by forming an antibody–antigen immunocomplex at the functionalized electrode, followed by electrochemical readout. The study used differential pulse voltammetry (DPV) to quantify GM2AP binding events. The DPV method provided current responses correlated with antigen concentration, enabling quantitative measurement of GM2AP.
The reported sensitivity and detection limit were determined under the sensor's optimized operational conditions. The authors cite a sensitivity value and a very low limit of detection consistent with the electrochemical DPV readout of the antibody–antigen complex on the modified graphene-paper surface.
Under optimized conditions the immunosensor achieved a reported sensitivity of 7.56 µA pg⁻¹ mL cm⁻². The limit of detection (LOD) is reported as 5.24 fg mL⁻¹, indicating a very low measurable concentration of GM2AP with this platform.
Precision testing included repeatability and reproducibility assessments. Relative standard deviations (RSDs) were reported to be less than 5.03% (n = 10), indicating low variability across repeated measurements. The authors further evaluated repeatability and reproducibility with T and F statistical tests and reported a low pooled standard deviation of 0.61% (n = 20), supporting the consistency of the assay performance.
The immunosensor was evaluated for selectivity and anti-interference characteristics when challenged with different biomarker solutions; the authors report remarkable sensitivity and strong anti-interference properties. These results suggest the antibody-based recognition element and surface chemistry confer a high degree of selectivity for GM2-activator protein.
Application to human samples was demonstrated using commercially purchased pooled human serum. High recovery rates were reported for quantification of GM2AP in these serum samples, indicating that the sensor can detect the biomarker in a complex biological matrix with acceptable analytical accuracy. The use of pooled commercial serum obviated the need for individual donor consent or institutional ethics approval in this study.
The study highlights that the designed immunosensor showed good stability and was reusable. Low RSDs in repeatability and reproducibility testing, together with the authors' reported pooled standard deviation, are presented as evidence for robust analytical behavior. The direct covalent immobilization of antibodies to the epoxy-functional polymer is a practical feature intended to simplify fabrication and improve the durability of the sensing surface by avoiding additional reagent-dependent coupling steps.
These practical attributes — high sensitivity, low LOD, anti-interference behavior, and demonstrated serum recoveries — are cited by the authors as supportive of the platform's potential for immunosensing of GM2AP in serum-based diagnostic workflows.
Ethical approval and informed consent were not required for this study because the authors used commercially purchased pooled human serum samples and did not access or collect identifiable donor information. The authors declared no competing interests.
Grant support for the work included NKUBAP.00.GA.21.328 from the Scientific and Technological Research Council of Tekirdağ Namık Kemal University, as noted in the source record.
Note: All performance figures, experimental approaches, and claims summarized above are drawn directly from the source abstract and accompanying PubMed record. The source reports chemical, electrochemical, and morphological characterization steps without listing detailed experimental protocols in the abstract; such specific methods and raw data were not provided in the source abstract and therefore are not detailed here.