Lysozyme detection in body biofluids by dual-decorated graphene oxide-gold nanoparticles-based biomimetic plasmonic sensor.

Accurate measurement of lysozyme in human biofluids is essential for early disease diagnosis and treatment monitoring. This work presents a plasmonic sensing platform utilizing AuNPs-GO/MIP, which integrates gold nanoparticles (AuNPs) and graphene oxide (GO) through molecular imprinting for the detection of lysozyme in urine, serum, and saliva. The enhancement in sensor sensitivity resulting from the addition of AuNPs and GO was verified by comparing it with a sensor lacking these components. We fabricated a AuNPs-GO/MIP surface plasmon resonance (SPR) chip using N-methacryloyl-L-cysteine and N-methacryloyl-L-tryptophan as functional monomers; the platform enables sensitive, low-cost, label-free lysozyme detection in buffer and synthetic biofluids, with no additional coupling chemistry. The imprinting efficiency was evaluated with a non-imprinted AuNPs-GO/NIP SPR sensor, yielding a remarkable imprinting factor (IF: 4.98). The sensor showed a linear detection response (R = 0.9794) for lysozyme in buffer (pH 7.4 PBS) within 0.01-0.5 nM, with a detection limit of 0.0015 nM. The sensor exhibited 4.27 times higher selectivity for lysozyme compared with myoglobin and 2.36 times compared with cytochrome c. The sensor exhibited high repeatability (RSD < 1.5%, n = 6), with no measurable decline in signal after six cycles. The low RSD for the AuNPs-GO/MIP SPR sensor implies it is reusable with high accuracy. Finally, detection experiments were conducted using the sensor on artificial urine, serum, and saliva samples to assess the matrix effect.