Size and Shell Effects on the Photoacoustic and Luminescence Properties of Dual Modal Rare-Earth-Doped Nanoparticles for Infrared Photoacoustic Imaging

Abstract

Infrared-emitting rare-earth (ytterbium and erbium) doped nanoparticles (REDNPs) have recently emerged as an excellent probe for both deep tissue luminescence and photoacoustic (PA) imaging with high resolutions and contrast. Here we report on the first study of the size and surface effects of the infrared PA imaging of dual modal REDNPs. We show that the PA signal amplitude generated by REDNPs is increased by increasing the size and coating the inorganic shell (undoped NaYF4 or silica). We have also discovered that the choice of the coating material is critical as undoped NaYF4 shell was able to enhance PA signal amplitude (by up to ∼30%) and infrared emission (19 times) simultaneously. The simultaneous enhancement of PA signal amplitude and infrared emission was due to increased phonon modes and reduced surface effects. The in vivo PA images obtained demonstrated that in addition to being excellent luminescent probes, the REDNPs also performed as successful PA contrast agents to visualize rodent cortical blood vessels.

Surface-Modified Shortwave-Infrared-Emitting Nanophotonic Reporters for Gene-Therapy Applications

“…21,31 The OA- and OM-coated RENPs (denoted as RENPs@OA/OM) were typically hydrophobic due to the long hydrophobic carbon chains of OA and OM, leading to poor colloidal stability in aqueous systems. Therefore, a surface-modification method for the coating of these as-synthesized nanoparticles with a cationic branched PEI coating (RENPs@PEI) was developed for the improved stable dispersion of RENPs in aqueous media.…”

“…The higher infrared absorption could potentially be harnessed to enhance the photoacoustic response or photothermal behavior of these particles for applications as dual-modal imaging probes or photothermic agents. 31,32 …”

“…21,31 In brief, 2 mL of Ln-(CF 3 COO) 3 OM solution (0.5 M) and 0.204 g of CF 3 COONa were dissolved in 3.2 mL of ODE and 2.5 mL of OA at 120 °C for 30 min until a clear solution was formed. Under vigorous mixing, the mixture was next heated to ~330–340 °C at a ramp rate of ~20 °C/min for ~1 h in an Ar environment.…”

Fluorescent Polystyrene Latex Nanoparticles for NIR-II <i>in vivo</i> Imaging

“…These fluorescent probes showed excellent fluorescence properties, and could be used for successful imaging of deep tissues (10 -20 mm). To date, many researchers have also reported on NIR-II and NIR-III fluorescent probes, including quantum dots, [14][15][16][17][18] RED-CNPs [19][20][21][22][23][24], SWCNTs [25,26], and organic dyes [27][28][29][30][31][32][33][34][35][36][37][38][39][40].…”

Near-Infrared to Visible Upconversion Emission Induced Photopolymerization: Polystyrene Shell Coated NaYF₄ Nanoparticles for Fluorescence Bioimaging and Nanothermometry

“…The temperature-dependent emission intensity changes of RED-CNPs are also strongly affected by the external environment of the dispersion solution [19]. To solve these problems, many researchers have reported the synthesis of core-shell structures of REDCNPs [22][23][24]. In these studies, rare-earth-ion non-doped ceramic shells were synthesized on the surfaces of core RED-CNPs, which improved the optical properties.…”