Electrostatic Adsorption of Dense AuNPs onto Silica Core as High-Performance SERS Tag for Sensitive Immunochromatographic Detection of Streptococcus pneumoniae

Streptococcus pneumoniae (S. pneumoniae) is a prominent pathogen of bacterial pneumonia and its rapid and sensitive detection in complex biological samples remains a challenge. Here, we developed a simple but effective immunochromatographic assay (ICA) based on silica-Au core-satellite (SiO(2)@20Au) SERS tags to sensitively and quantitatively detect S. pneumoniae. The high-performance SiO(2)@20Au tags with superior stability and SERS activity were prepared by one-step electrostatic adsorption of dense 20 nm AuNPs onto 180 nm SiO(2) core and introduced into the ICA method to ensure the high sensitivity and accuracy of the assay. The detection limit of the proposed SERS-ICA reached 46 cells/mL for S. pneumoniae and was 100-fold more sensitive than the traditional AuNPs-based colorimetric ICA method. Further, considering its good stability, specificity, reproducibility, and easy operation, the SiO(2)@20Au-SERS-ICA developed here has great potential to meet the demands of on-site and accurate detection of respiratory pathogens.