Sensitive surface plasmon resonance sensor for differentiation of porcine and bovine gelatin using a green-synthesized Ag/rGO-glutaraldehyde nanoplasmonic sensing layer

An LSPR sensor incorporating silver/reduced graphene oxide-glutaraldehyde nanocomposites (Ag/rGO-GA NCs) as an active sensing interface successfully distinguishes porcine and bovine gelatin over a concentration range of 1–5 mg/mL, highlighting its potential for rapid gelatin authentication and halal verification. Ag/rGO-GA nanocomposites were synthesized via a green route using Amaranthus viridis extract and integrated into a Kretschmann configuration with a prism/Au film/(Ag/rGO-GA)/gelatin/air layer structure. The resulting sensor exhibits pronounced localized surface plasmon resonance (LSPR) responses that are highly sensitive to gelatin adsorption. Adding the Ag/rGO-GA layer to the sensor surface produces an SPR angle shift of 0.24°, together with a 0.16 increase in the minimum reflectance and a 0.49° change in the FWHM. Subsequent gelatin binding on the sensor surface produces significant SPR angle shifts and increases in the minimum reflectance with increasing gelatin concentration. These enhanced responses are more pronounced for porcine gelatin than for bovine gelatin, indicating a greater effective refractive-index change at the sensing interface, which may be associated with differences in amino acid composition, molecular weight distribution, and adsorption behavior between the two gelatin sources. The sensor exhibits limits of detection of 0.049–0.116 mg mL⁻¹ , demonstrating that Ag/rGO-GA functionalization significantly enhances the SPR signal through improved plasmonic response, enabling sensitive and discriminative detection of gelatin origin. This green-engineered nanoplasmonic platform further opens pathways toward sustainable, portable, and scalable sensing technologies for future halal verification and transparent food supply chains.