Activated silver nanoparticle-based platform for specific capture of Porphyromonas gingivalis in human saliva

Porphyromonas gingivalis (P. gingivalis) is the leading causative pathogen for periodontitis and gingivitis. Specific and direct detection of P. gingivalis based on surface-enhanced Raman spectroscopy (SERS) is a challenge, especially in clinical samples. In this paper, we have developed a novel label-free SERS platform to successfully obtain Raman fingerprints of P. gingivalis in simulated and clinical patients. The activated silver nanoparticles was used as the substrate with the addition of reducing agent (sodium borohydride) twice and aggregating agent (Na+) to establish the "hot spot", that accumulated on the surface like the "mask" to capture bacteria. The method broke the bottleneck of poor quantification and low specificity of SERS, and achieved rapid, sensitive, quantifiable and specific determination of bacteria with lower limit, excellent repeatability and stability. Further mechanical learning was combined with effective classification of four different oral bacteria, including P. gingivalis, Enterococcus faecalis (E. faecalis), Staphylococcus aureus (S. aureus) and Streptococcus mutans (S. mutans). The technique could identify P. gingivalis not only in artificial serum, artificial saliva and mixed bacterial samples, but most importantly, enabled non-destructive detection in the saliva of patients with periodontal disease. In addition, antimicrobial experiments have confirmed environmental friendliness that no secondary infections will occur. Therefore, the unlabelled, convenient and green SERS detection tool for oral bacteria holds great potential applications in clinical early diagnosis and prediction disease progression in periodontal disease.