Enhancing SPR biosensor performance for creatinine detection via plasma polymerized heptylamine coatings

Surface wettability, measured via water contact angle (WCA) measurements, is an essential parameter in evaluating the characteristics of sensor surfaces in plasmonic biosensing, particularly in Kretschmann-based surface plasmon resonance (K-SPR). This study investigates plasma polymerized heptylamine (ppHA) coatings for enhancing Au K-SPR biosensors. The WCA results, ranging from 58° to 82°, confirm that a hydrophilic surface promotes biomolecule immobilization. The red shift of the SPR curve at 785 nm wavelength yields a refractive index sensitivity of 60°/RIU, with a good correlation coefficient (R² = 0.7584) between plasma power and WCA. The findings demonstrate that Au-ppHA coatings successfully optimize wettability and sensitivity, thereby improving SPR biosensor performance. Furthermore, the developed biosensor was successfully functionalized for creatinine detection, a key biomarker for kidney waste. The sensor demonstrated a high sensitivity of 1.1918 °/mM, confirming that ppHA coatings are an effective platform for developing high-performance K-SPR biosensors for medical diagnostics.