Development of a Magnetically-Assisted SERS Biosensor for Rapid Bacterial Detection

Abstract

Introduction

Ultrasensitive bacterial detection methods are crucial to ensuring accurate diagnosis and effective clinical monitoring, given the significant threat bacterial infections pose to human health. The aim of this study is to develop a biosensor with capabilities for broad-spectrum bacterial detection, rapid processing, and cost-effectiveness.

Methods

A magnetically-assisted SERS biosensor was designed, employing wheat germ agglutinin (WGA) for broad-spectrum recognition and antibodies for specific capture. Gold nanostars (AuNSs) were sequentially modified with the Raman reporter molecules and WGA, creating a versatile SERS tag with high affinity for a diverse range of bacteria. Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) antibody-modified Fe₃O₄ magnetic gold nanoparticles (MGNPs) served as the capture probes. Target bacteria were captured by MGNPs and combined with SERS tags, forming a “sandwich” composite structure for bacterial detection.

Results

AuNSs, with a core size of 65 nm, exhibited excellent storage stability (RSD=5.6%) and demonstrated superior SERS enhancement compared to colloidal gold nanoparticles. Efficient binding of S. aureus and P. aeruginosa to MGNPs resulted in capture efficiencies of 89.13% and 85.31%, respectively. Under optimized conditions, the developed assay achieved a limit of detection (LOD) of 7 CFU/mL for S. aureus and 5 CFU/mL for P. aeruginosa. The bacterial concentration (10–10⁶ CFU/mL) showed a strong linear correlation with the SERS intensity at 1331 cm⁻¹. Additionally, high recoveries (84.8% - 118.0%) and low RSD (6.21% - 11.42%) were observed in spiked human urine samples.

Conclusion

This study introduces a simple and innovative magnetically-assisted SERS biosensor for the sensitive and quantitative detection of S. aureus or P. aeruginosa, utilizing WGA and antibodies. The developed biosensor enhances the capabilities of the “sandwich” type SERS biosensor, offering a novel and effective platform for accurate and timely clinical diagnosis of bacterial infections.

Graphical Abstract

Keywords:

• SERS
• WGA
• pathogenic bacteria
• bacterial detection
• dual-recognition

Abbreviations

S. aureus, Staphylococcus aureus; P. aeruginosa, Pseudomonas aeruginosa; WGA, Wheat germ agglutinin; Abs, Antibodies; AuNSs, Gold nanostars, DTNB, 5.5’-dithiobis(2-nitrobenzoic acid); magnetic gold nanoparticles (MGNPs); LOD, limit of detection; SERS, Surface-enhanced Raman scattering.

Acknowledgments

We would like to express our sincere gratitude to Ping Yang, Nanjing Drum Tower Hospital, for his significant contributions to this research. Although not listed as a corresponding author, Ping Yang played a crucial role in data analysis and experimental design. His expertise and dedication greatly enriched the quality and depth of this study.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This research was supported by the National Natural Science Foundation of China (82072380, 82272423), Key R & D Program of Jiangsu Province (BE2020646), Research foundation for advanced talents of Guandong Provincial People’s Hospital (KJ012021097), the Nanjing Drum Tower Hospital Clinical Research Special Fund project (2022-LCYJ-PY-36, 2022-LCYJ-MS-28).