“Magnet” Based on Activated Silver Nanoparticles Adsorbed Bacteria to Predict Refractory Apical Periodontitis Via Surface-Enhanced Raman Scattering

Refractory apical periodontitis (RAP) is an endodontic apical inflammatory disease caused by Enterococcus faecalis (E. faecalis). Bacterial detection using surface-enhanced Raman scattering (SERS) technology is a hot research topic, but the specific and direct detection of oral bacteria is a challenge, especially in real clinical samples. In this paper, we develop a novel SERS-based green platform for label-free detection of oral bacteria. The platform was built on silver nanoparticles with a two-step enhancement way using NaBH4 and sodium (Na+) to form “hot spots,” which resulted in an enhanced SERS fingerprint of E. faecalis with fast, quantitative, lower-limit, reproducibility, and stability. In combination with machine learning, four different oral bacteria (E. faecalis, Porphyromonas gingivalis, Streptococcus mutans, and Escherichia coli) could be intelligently distinguished. The unlabeled detection method emphasized the specificity of E. faecalis in simulated saliva, serum, and even real samples from patients with clinical root periapical disease. In addition, the assay has been shown to be environmentally friendly and without secondary contamination through antimicrobial assays. The proposed label-free, rapid, safe, and green SERS detection strategy for oral bacteria provided an innovative solution for the early diagnosis and prevention of RAP and other perioral diseases

The primers of <i>P</i>. <i>gingivalis</i> and <i>fimA</i>.

<p>The primers of <i>P</i>. <i>gingivalis</i> and <i>fimA</i>.</p

The primers of <i>P</i>. <i>gingivalis</i> and <i>fimA</i>.

<p>The primers of <i>P</i>. <i>gingivalis</i> and <i>fimA</i>.</p

Gene expression profiles of HUVECs.

<p>Cells grew in culture medium, on surfaces of 316L SS and HNNF SS for 7 days determined using qRT-PCR method.</p

Nucleotide sequences of primers used for qRT-PCR.

<p>Nucleotide sequences of primers used for qRT-PCR.</p

Measurement of HUVEC proliferation.

<p>(A) Relative growth rates of HUVECs on 316L SS and HNNF SS after 1-, 3-, 5- and 7-day growth with respect to the control of HUVECs (100%). (B) Growth curve of HUVECs on surfaces of 316L SS and HNNF SS, and in culture medium in a 7-day period.</p

Target bacteria and their species-specific primers used in the present study.

<p>Target bacteria and their species-specific primers used in the present study.</p

Schematic diagram of pathways proposed in 316L SS and HNNF SS induced cell apoptosis.

<p>The proposed model shows that 316L SS and HNNF SS cause cell apoptosis through extrinsic apoptosis pathway by the ligation of Fas ligand to Fas receptor activating caspase-8 and caspase-3, whereas HNNF SS reduces the activation of caspase-8 and caspase-3 compared with 316L SS.</p

Prevalence of subgingival microorganisms in case and control group.

<p>The Fisher exact test was used for pairwise comparisons of the frequencies of periodontopathogens (* <i>P< 0</i>.<i>05</i>, **<i>P<0</i>.<i>0</i>).</p

The prevalence of <i>P</i>. <i>gingivalis</i> and <i>fimA</i> genotypes in two groups.

<p>The prevalence of <i>P</i>. <i>gingivalis</i> and <i>fimA</i> genotypes in two groups.</p