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A "Double-Locked" and Enzyme/pH-Activated Theranostic Agent for Accurate Tumor Imaging and Therapy.

ABSTRACT: Theranostic agents for concurrent cancer therapy and diagnosis have begun attracting attention as a promising modality. However, accurate imaging and identification remains a great challenge for theranostic agents. Here, we designed and synthesized a novel theranostic agent H6M based on the "double-locked" strategy by introducing an electron-withdrawing nitro group into 1-position of a pH-responsive 3-amino-β-carboline and further covalently linking the hydroxamic acid group, a zinc-binding group (ZBG), to the 3-position of β-carboline to obtain histone deacetylase (HDAC) inhibitory effect for combined HDAC-targeted therapy. We found that H6M can be specifically reduced under overexpressed nitroreductase (NTR) to produce H6AQ, which emits bright fluorescence at low pH. Notably, H6M demonstrated a selective fluorescence imaging via successive reactions with NTR (first "key") and pH (second "key"), and precisely identified tumor margins with a high S/N ratio to guide tumor resection. Finally, H6M exerted robust HDAC1/cancer cell inhibitory activities compared with a known HDAC inhibitor SAHA. Therefore, the NTR/pH-activated theranostic agent provided a novel tool for precise diagnosis and efficient tumor therapy.

SUBMITTER: Luo J

PROVIDER: S-EPMC8779152 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The optical imaging guided tumor vessels and vascular malformation visualization by using the second near infrared emission beyond 1500 nm (NIR-II) is emerged as the next generation fluorescence imaging technique for early tumor diagnosis and identification of tumor-associated vascular features. On the other hand, developing theranostic probes for NIR-II imaging guided photothermal therapy (PTT) is of great significance, which is rarely explored. Herein, a high performance theranostic nanoplatform based on the core-shell structured NaLuF4 nanorods@polydopamine (denoted as NRs@PDA) by integrating the new advanced NIR-II imaging beyond 1500 nm with PTT function was developed for tumor-associated vascular malformation visualization and imaging-guided PTT. Methods: In this work, the hydrophilic NaLuF4 NRs@PDA therapeutic probe was synthesized by using a reverse microemulsion method. The crystal phase, morphology, emission spectra and photothermal performance of the synthesized samples were systematically characterized. The NIR-II optical imaging and photothermal properties were investigated by in vitro and in vivo experiments. Results: The NaLuF4 NRs@PDA therapeutic probe possessed efficient NIR-II emission centered at 1525 nm with high quantum yield (QY), good photo-stability and high biocompatibility. In vivo NIR-IIb imaging based on the designed probe can clearly visualize the whole-body vessel and brain vessel with high spatial resolution, especially tumor-associated vessels. In addition, in vitro and in vivo experiments also demonstrated that the designed NaLuF4 NRs@PDA probe possessed efficient photothermal conversion efficiency (40.18%) for PTT ablation of tumor. Conclusion: With the excellent NIR-II imaging ability and PTT of tumor, the designed theranostic nanoplatform successfully realize the simultaneous tumor vessel diagnosis and tumor therapy, which may provide the opportunity of designing new theranostic bioprobes with combination of the NIR-II optical imaging technique and PTT function for tumor diagnosis and therapy.

Project description:The low tissue penetration depth of external excitation light severely hinders the sensitivity of fluorescence imaging (FL) and the efficacy of photodynamic therapy (PDT) in vivo; thus, rational theranostic platforms that overcome the light penetration depth limit are urgently needed. To overcome this crucial problem, we designed a self-luminescing nanosystem (denoted POCL) with near-infrared (NIR) light emission and singlet oxygen (1O2) generation abilities utilizing an intraparticle relayed resonance energy transfer strategy. Methods: Bis[3,4,6-trichloro-2-(pentyloxycarbonyl) phenyl] oxalate (CPPO) as a chemical energy source with high reactivity toward H2O2, poly[(9,9'-dioctyl-2,7-divinylene-fluorenylene)-alt-2-methoxy- 5-(2-ethyl-hexyloxy)-1,4-phenylene] (PFPV) as a highly efficient chemiluminescence converter, and tetraphenylporphyrin (TPP) as a photosensitizer with NIR emission and 1O2 generation abilities were coencapsulated by self-assembly with poly(ethyleneglycol)-co-poly(caprolactone) (PEG-PCL) and folate-PEG-cholesterol to form the POCL nanoreactor, with folate as the targeting group. A series of in vitro and in vivo analyses, including physical and chemical characterizations, tumor targeting ability, tumor microenvironment activated imaging and photodynamic therapy, as well as biosafety, were systematically investigated to characterize the POCL. Results: The POCL displayed excellent NIR luminescence and 1O2 generation abilities in response to H2O2. Therefore, it could serve as a specific H2O2 probe to identify tumors through chemiluminescence imaging and as a chemiluminescence-driven PDT agent for inducing tumor cell apoptosis to inhibit tumor growth due to the abnormal overproduction of H2O2 in the tumor microenvironment. Moreover, the folate ligand on the POCL surface can further improve the accumulation at the tumor site via a receptor-mediated mechanism, thus enhancing tumor imaging and the therapeutic effects both in vitro and in vivo but without any observable systemic toxicity. Conclusion: The nanosystem reported here might serve as a targeted, smart, precise, and noninvasive strategy triggered by the tumor microenvironment rather than by an outside light source for cancer NIR imaging and PDT treatment without limitations on penetration depth.

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A "Double-Locked" and Enzyme/pH-Activated Theranostic Agent for Accurate Tumor Imaging and Therapy.

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