Nd³⁺-Sensitized Upconversion Nanostructure as a Dual-Channel Emitting Optical Probe for Near Infrared-to-Near Infrared Fingerprint Imaging

Lanthanide upconversion nanophosphors (Ln-UCNPs) have attracted great attention in a variety of fields, benefiting from low background fluorescence interference and a high signal-to-noise ratio of upconversion luminescence. However, the establishment of Ln-UCNPs with dual near-infrared (NIR) emission channels still remains challenging. Herein, we report the design and synthesis of Nd³⁺-sensitized NaYbF₄:Tm@NaYF₄:Yb@NaNdF₄:Yb hierarchical-structured nanoparticles that emit NIR luminescence at 696 and 980 nm under excitation at 808 nm. The sensitizer-rich NaYbF₄ core promotes efficient energy transfer to Tm³⁺. The interlayer of NaYF₄:Yb effectively prevents the cross-relaxation process from Tm³⁺ to Nd³⁺ and thus enhances the luminescence emission. The introduction of Nd³⁺ ion as the sensitizer transforms the excitation wavelength from 980 to 808 nm, which subtly averts the laser-induced thermal effect and offers a new pathway for the NIR emission channel at 980 nm. The as-prepared nanoparticles were further applied in developing latent and blood fingerprint images, which exhibited high signal-to-noise ratio and distinguishable details under 808 nm excitation with negligible thermal damage to the sample. Our work provides a promising strategy to realize NIR-to-NIR dual-channel emissions in Ln-UCNPs. With further functionalization, such nanoparticles are expected to have great potential in forensic and biological sciences

Supplementary document for High-throughput sorting of nanoparticles with light-patterned dielectrophoresis force - 6610993.pdf

This supplemental document contains 2 figures, Fig.S1 and Fig.S2

17β-Estradiol-Loaded PEGlyated Upconversion Nanoparticles as a Bone-Targeted Drug Nanocarrier

Hormone replacement therapy (HRT) plays an important role in the treatment and prevention of osteoporosis. Here, 17β-estradiol (E2)-loaded PEGlyated upconversion nanoparticles (E2-UCNP@pPEG) were synthesized that retained E2 bioactivity and improved delivery efficiency over a relatively long time-period. E2-UCNP@pPEG was synthesized and characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), among other methods. The loading efficiency of E2 was determined to be 14.5 wt %, and the nanocarrier effectively facilitated sustained release. Confocal upconversion luminescence (UCL) imaging using the CW 980 nm laser as excitation resource revealed significant interactions of E2-UCNP@pPEG with preosteoblasts. E2-UCNP@pPEG treatment of preosteoblasts induced positive effects on differentiation, matrix maturation, and mineralization. Moreover, in situ and ex vivo UCL imaging studies disclosed that E2 encapsulated in the nanocomposite was passively delivered to bone. Our results collectively suggest that this nanoreservoir provides an effective drug-loading system for hormonelike drug delivery and support its considerable potential as a therapeutic agent for osteoporosis

Ultrasensitive Near-Infrared Fluorescence-Enhanced Probe for <i>in Vivo</i> Nitroreductase Imaging

Nitroreductase (NTR) can be overexpressed in hypoxic tumors, thus the selective and efficient detection of NTR is of great importance. To date, although a few optical methods have been reported for the detection of NTR in solution, an effective optical probe for NTR monitoring <i>in vivo</i> is still lacking. Therefore, it is necessary to develop a near-infrared (NIR) fluorescent detection probe for NTR. In this study, five NIR cyanine dyes with fluorescence reporting structure decorated with different nitro aromatic groups, Cy7-1–5, have been designed and explored for possible rapid detection of NTR. Our experimental results presented that only a <i>para</i>-nitro benzoate group modified cyanine probe (Cy7-1) could serve as a rapid NIR fluorescence-enhanced probe for monitoring and bioimaging of NTR. The structure–function relationship has been revealed by theoretical study. The linker connecting the detecting and fluorescence reporting groups and the nitro group position is a key factor for the formation of hydrogen bonds and spatial structure match, inducing the NTR catalytic ability enhancement. The <i>in vitro</i> response and mechanism of the enzyme-catalyzed reduction of Cy7-1 have been investigated through kinetic optical studies and other methods. The results have indicated that an electro-withdrawing group induced electron-transfer process becomes blocked when Cy7-1 is catalytically reduced to Cy7-NH₂ by NTR, which is manifested in enhanced fluorescence intensity during the detection process. Confocal fluorescence imaging of hypoxic A549 cells has confirmed the NTR detection ability of Cy7-1 at the cellular level. Importantly, Cy7-1 can detect tumor hypoxia in a murine hypoxic tumor model, showing a rapid and significant enhancement of its NIR fluorescence characteristics suitable for fluorescence bioimaging. This method may potentially be used for tumor hypoxia diagnosis