NaGdF₄:Nd@NaGdF₄ Core-Shell Down-Conversion Nanoparticles as NIR-II Fluorescent Probes for Targeted Imaging of Bacteria

Abstract

Bacterial infections are a serious ongoing threat to human health. As such, within the context of modern technology, there is an urgent need to develop fluorescent probes suitable for diagnosing bacterial infections in vivo. Herein, we synthesize NaGdF 4 :Nd@NaGdF 4 core-shell down-conversion nanoparticles (DCNPs) demonstrating excellent emission intensity in the second nearinfrared (NIR-II) window for use as fluorescent probes to enable high-quality imaging of pathogenic infections. The fluorescent probe is covalently linked with vancomycin (Van), which specifically binds to Gram-positive bacteria such as S. aureus. Both in vitro detection and in vivo imaging results show that the Vanmodified NIR-II fluorescent probe can distinguish Gram-positive from Gram-negative bacteria with a high degree of selectivity. Biocompatibility is verified by MTT assay and histological analyses.

An Ag2S@ZIF-Van nanosystem for NIR-II imaging of bacterial-induced inflammation and treatment of wound bacterial infection

“…Vancomycin (Van) is a Gram-positive antibiotic drug able to specifically bind with the D-Ala-D-Ala of bacterial cell walls, allowing it to guide nanomaterials for targeted drug delivery or imaging of bacterial inflammation in vivo. 28,29,51 The ability of Ag 2 S@ZIF-Van to target and detect bacteria was evaluated in vitro and in vivo. Incubation of S. aureus with Ag 2 S@ZIF-Van was followed by centrifugation and NIR-II fluorescence imaging.…”

“…26,27 Fortunately, it has been found that vancomycin (Van) can guide a contrast agent to achieve targeted NIR-II fluorescent imaging in vivo at bacterial infection sites. 28,29 Biocompatible semiconductor Ag 2 S quantum dots (QDs), with a tunable fluorescence emission band from 800 nm to 1400 nm, have been widely used for basic medical analysis, 30,31 sensing, 32,33 and in vivo imaging and therapy. [34][35][36][37] Further, Ag 2 S QDs possess excellent photothermal conversion properties enabling their use as an antibacterial photothermal agent.…”

“…26,27 Fortunately, it has been found that vancomycin (Van) can guide a contrast agent to achieve targeted NIR-II fluorescent imaging in vivo at bacterial infection sites. 28,29…”

Lanthanide/Cu2–xSe Nanoparticles for Bacteria-Activated NIR-II Fluorescence Imaging of Infection

“…The fluorescence reduction efficiency is estimated by (I 0 − I)/I 0 , where I 0 and I refer to 4f); the fluorescence response is found to be weaker for a small number of bacteria (<10 5 CFU). 40,41 For vancomycin-resistant Grampositive bacteria, vancomycin has a weak affinity to D-Ala-D- Ala residues on their surface, resulting in a relatively low fluorescence response. 42,43 Compared with PBS, Gramnegative bacteria can enhance the luminescence of DCNPs-Van/Cu 2−x Se by approximately a factor of 2, which is caused by the nonspecific binding of the positively charged DCNPs-Van moiety to the bacterial surface through electrostatic interaction.…”

“…Nanoparticles (>10 nm) are known to primarily accumulate in the liver region, and the liver region exhibits a strong fluorescence signal. 41,48,49 The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acssensors.2c00683.…”