Abstract
<title>Abstract</title> <p>Growth-related assessment commonly involves insulin-like growth factor-1 (IGF-1), which is used to monitor bone and skeletal maturity and to support orthodontic treatment planning. Compared with conventional blood-based assays, saliva is a painless and easily accessible biological matrix that allows repeated assessment of IGF-1. Existing approaches for salivary IGF-1 analysis predominantly depend on centralized laboratory techniques such as enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and mass spectrometry (MS), which are time-consuming, operationally complex, and high-cost procedures. This study presents a rapid and straightforward multi-walled carbon nanotubes (MWCNTs)-based immunosensor for the quantitative measurement of IGF-1 in saliva. A label-free electrochemical immunosensor was constructed on a MWCNTs screen-printed carbon electrode (MWCNTs-SPCE). The modified MWCNTs-SPCE was immobilized with anti-IGF-1 monoclonal antibodies to detect the presence of IGF-1 in saliva. The stepwise fabrication process of the label-free electrochemical immunosensor was characterized morphologically and structurally by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. Electrochemical characterization of the MWCNTs-SPCE was carried out using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, the immunosensor displayed a linear response to IGF-1 from 1 to 100 µg/mL in 0.01 M phosphate-buffered saline (R² = 0.998), achieving a limit of detection(LOD) of 0.95 µg/mL and a limit of quantification(LOQ) of 3.19 µg/mL within 30 min. Importantly, the study also demonstrates that the immunosensor successfully detects a range of IGF-1 concentrations from 1 to 100 µg/mL in synthetic saliva with a LOD of 0.99 µg/mL and LOQ of 3.3 µg/mL, highlighting its sensitivity and analytical reliability in practical clinical settings.</p>