Glucose-lightened upconversion nanoprobes for accurate cellular-discrimination based on Warburg effect

Accurate cellular-recognition based disease therapy is of significance for precision medicine. However, except of specific antibody-coupling strategy, very few probes have been reported to efficiently discriminate normal cells and lesion cells through cellular microenvironment. Herein, we proposed a glucose selectively-lightened upconversion nanoprobe to recognize cancer cells from a pile of normal cells based on Warburg effect, that indicated a heightened demand for glucose intake for cancer cells. The nanoprobes were constructed by mesoporous silica-coated upconversion nanoparticles (UCNP@mSiO2) with the crucial incorporation of a glucose-responsive modality, benzoboric acid (BA)-modified fluorescein molecules (FITC-BA). In cancer cells, the presence of elevated glucose concentrations triggered the transformation of FITC-BA to FITC-Glucose to recover nanoprobes' luminescence, however, the nanoprobes exhibited a shielded luminescent effect in healthy cells. To validate the hypothesis of accurate cellular-discrimination, a photodynamic therapy modality, riboflavin, with a specific ratio were also loaded into above UCNP@mSiO2 nanoprobes for effective production of reactive oxygen species to kill cells. It was found that 97.8% of cancer cells were cleaned up, but normal cells retained a nearly 100% viability after 10 min laser illumination. By leveraging the metabolic disparity from Warburg effect, the nanoprobes offer a highly accurate cellular discrimination, and significantly mitigate "off-target" damage commonly associated with conventional therapies.

Upconversion nanoparticle-based optogenetic nanosystem for photodynamic therapy and cascade gene therapy

Most photosensitizer molecules used for the photodynamic therapy (PDT) are chemically-synthesized organic photosensitizer dyes which show several limitations such as unsatisfactory cell uptake, weak selectivity and off-target phototoxicity. Recently, genetically-encoded photosensitizers have attracted increasing attentions which provide the targeted cell elimination with single-cell precision. However, their applications are mainly limited by the shallow tissue penetration depth of the excitation light and the low cell apoptosis ratio. Herein, we developed a feasible upconversion nanoparticle (UCNP)-based optogenetic nanosystem with three-in-one functional integration: bio-imaging, NIR-triggered PDT and cascade gene therapy. Firstly, the mitochondria-targeted genetically-encoded photosensitizer was constructed and transfected into cancer cells. Then, the functional upconversion nanoprobe was constructed with the mitochondria targetability and then the siRNA was loaded on the surface of UCNPs via the reactive oxygen species (ROSs) sensitive chemical bond. After the transfection and incubation, both of the upconversion nanoprobe and the genetically-encoded photosensitizer were accumulated in the mitochondria of cancer cells. Under the NIR irradiation, the emission of UCNPs could excite the expressed protein photosensitizer to generate ROSs which then stimulated the release of siRNAs in a controllable manner, achieving PDT and cascade gene therapy. Since the generation of ROSs and the release of siRNA occurred in the mitochondria in-situ, the mitochondria-mediated cell apoptosis signal pathway would be activated to induce cell apoptosis and subsequently inhibit tumor growth. To the best of our knowledge, this is the first report about NIR laser-activated, organelle-localized genetically-encoded photosensitizers developed for cascade therapy, which will widen the application of optogenetic tools in the tumor therapy. STATEMENT OF SIGNIFICANCE: The application of genetically-encoded photosensitizers in photodynamic therapy (PDT) is mainly limited by the shallow tissue penetration depth of the excitation light and unsatisfactory therapeutic performance. In this experiment, we developed an upconversion nanoparticles-based optogenetic nanosystem to enhance the PDT and cascade gene therapy for malignant tumors. The expressed genetically-encoded photosensitizers were accumulated in the mitochondria, which were activated in situ by the upconversion nanoprobe. Besides, the photogenerated reactive oxygen species (ROSs) stimulated the release of siRNAs in a controllable manner. To the best of our knowledge, this is the first report about NIR laser-activated, genetically-encoded photosensitizers developed for organelle-localized controllable cascade therapy. We hope this work can accelerate the application of genetically-encoded photosensitizers in the tumor therapy.

Dual-modality Imaging of Angiogenesis in Unstable Atherosclerotic Plaques with VEGFR2-Targeted Upconversion Nanoprobes in vivo

AIM

Angiogenesis plays a major role in atherosclerotic plaque development and instability. Our study aims to develop a novel optical and magnetic resonance (MR) dual-modality molecular imaging probe to early detect unstable plaques in vivo by targeting biomarkers of angiogenesis in murine models of atherosclerosis (AS).

METHODS

Immunofluorescence and western blot were used to detect the expression of Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) in activated Human Umbilical Vein Endothelial Cells (HUVECs). After synthesis and identification of novel short peptide VRBP1-targeted VEGFR2, HUVECs were co-cultured with FITC-VRBP1 to test specific affinity of VRBP1. Then VRBP1-UCNPstargeting VEGFR2 were constructed by conjugating VRBP1 to the surface of NaGdF₄:Yb,Er@NaGdF₄ nanoparticles. The characterization of the nanoparticles was performed by transmission electron microscopy (TEM), distribution of size, hydrodynamic size, zeta potential, absorption spectra, emission spectra, imaging intensity of different concentrations, binding affinity and cytotoxicity of nanoprobes in vitro. The upconversion luminescence (UCL) and MR imaging were performed to identify unstable atherosclerotic plaque in ApoE^-/- mice in vivo and ex vivo. Morphological staining was used to verify AS model and angiogenesis, and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) was used to confirm accumulation of the nanoparticles after imaging.

RESULTS

After induced by hypoxia and ox-LDL, the expression of VEGFR2 in activated HUVECs was enhanced. FITC-VRBP1 can specifically bind to the HUVECs. Characterization of the nanoparticles showed that particles size is uniform with a stable structure, specific optical and MR signal, good binding affinity to VEGFR2 and low cytotoxicity. In vivo and ex vivo UCL imaging and quantitative analysis revealed that distinctive optical signal was observed in the regions of left carotid common arteries (LCCAs) of AS group after injection of VRBP1-UCNPs. Higher signal intensity on T1-weighted MR imaging appeared in the LCCA wall of AS group after injection. The results of morphological staining demonstrated angiogenesis in the atherosclerotic plaques, Gd ions in LCCAs, aortic arch and renal arteries bifurcations detected by ICP-AES confirmed accumulation of the nanoparticles in plaque.

CONCLUSIONS

We successfully design and synthesize a novel UCNPs using peptide VRBP1 targeting to VEGFR2. In vivo imaging demonstrates that VRBP1-UCNPs can be used to perform optical/MR dual-modality imaging targeting angiogenesis in plaques, which is a promising technique to early detect unstable atherosclerosis.

Upconversion Fluorescent Nanoprobe for Highly Sensitive In Vivo Cell Tracking

Near-infrared (NIR)-to-visible upconversion nanomaterials (UCNPs) used as biomedical nanoprobes have considerable advantages over the traditional used "downconversion" fluorescent dyes. Functionalized upconversion nanoparticles (UCNPs) represent high sensitivity and great biocompatibility. Cells labeled with these UCNPs can be tracked for long term in vivo. Here we describe UCNP-PEG-ARG for highly sensitive in vivo cell tracking.