Tumor‐Targeting Fluorescent Probe Based on 1,8‐Naphthalimide and Porphyrin Groups

Carbonic Anhydrase IX Targeted Polyaspartamide fluorescent Probes for Tumor imaging

Background

Precise intraoperative tumor delineation is essential for successful surgical outcomes. However, conventional methods are often incompetent to provide intraoperative guidance due to lack specificity and sensitivity. Recently fluorescence-guided surgery for tumors to delineate between cancerous and healthy tissues has attracted widespread attention. The contrast-enhanced fluorescent imaging has been applied for non-invasive diagnosis of cancers using tumor-targeting fluorescent probes.

Methods

The carbonic anhydrase IX targeted polyaspartamide fluorescent compounds (SD-PHEA-NI) were synthesized by incorporating a tumor-targeting group of sulfadiazine (SD) and N-butyl-4-ethyldiamino-1,8-naphthalimide (NI) into water-soluble carriersof poly-α,β-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA). These derivatives were also characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, ultraviolet-visible spectroscopy, nuclear magnetic resonance spectroscopy and fluorescence assays. The cellular uptake, cytotoxicity, and fluorescence imaging ability were evaluated.

Results

Experiment results indicated that SD-PHEA-NI has low cytotoxic to Henrietta Lacks (HeLa) cells. Moreover, B16F10 melanoma cells can take up SD-PHEA-NI and show good green fluorescent images. However, SD-PHEA-NI displayed a low-intensity green fluorescence signal in healthy human embryonic kidney (293T) cells.

Conclusion

SD-PHEA-NI can be considered a potential fluorescent probe for the detection of tumors. This study has the potential to enhance tumor diagnosis and image-guided surgical interventions by providing real-time information and robust decision support, thereby reducing recurrence and complication rates and ultimately improving patient outcomes.

Synthesis and Characterization of Sulfonamide-Containing Naphthalimides as Fluorescent Probes

A tumor-targeting fluorescent probe has attracted increasing interest in fluorescent imaging for the noninvasive detection of cancers in recent years. Sulfonamide-containing naphthalimide derivatives (SN-2NI, SD-NI) were synthesized by the incorporation of N-butyl-4-ethyldiamino-1,8-naphthalene imide (NI) into sulfonamide (SN) and sulfadiazine (SD) as the tumor-targeting groups, respectively. These derivatives were further characterized by mass spectrometry (MS), nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV), and a fluorescence assay. In vitro properties, including cell cytotoxicity and the cell uptake of tumor cells, were also evaluated. Sulfonamide-containing naphthalimide derivatives possessed low cell cytotoxicity to B16F10 melanoma cells. Moreover, SN-2NI and SD-NI can be taken up highly by B16F10 cells and then achieve good green fluorescent images in B16F10 cells. Therefore, sulfonamide-containing naphthalimide derivatives can be considered to be the potential probes used to target fluorescent imaging in tumors.

Dextran Fluorescent Probes Containing Sulfadiazine and Rhodamine B Groups

Fluorescent imaging has been expanded, as a non-invasive diagnostic modality for cancers, in recent years. Fluorescent probes in the near-infrared window can provide high sensitivity, resolution, and signal-to-noise ratio, without the use of ionizing radiation. Some fluorescent compounds with low molecular weight, such as rhodamine B (RhB) and indocyanine green (ICG), have been used in fluorescent imaging to improve imaging contrast and sensitivity; however, since these probes are excreted from the body quickly, they possess significant restrictions for imaging. To find a potential solution to this, this work investigated the synthesis and properties of novel macromolecular fluorescent compounds. Herein, water-soluble dextran fluorescent compounds (SD-Dextran-RhB) were prepared by the attachment of RhB and sulfadiazine (SD) derivatives to dextran carrier. These fluorescent compounds were then characterized through IR, ¹H NMR, ¹³C NMR, UV, GPC, and other methods. Assays of their cellular uptake and cell cytotoxicity and fluorescent imaging were also performed. Through this study, it was found that SD-Dextran-RhB is sensitive to acidic conditions and possesses low cell cytotoxicities compared to normal 293 cells and HepG2 and HeLa tumor cells. Moreover, SD-Dextran-RhB demonstrated good fluorescent imaging in HepG2 and HeLa cells. Therefore, SD-Dextran-RhB is suitable to be potentially applied as a probe in the fluorescent imaging of tumors.

Effects of serum albumin on the photophysical characteristics of synthetic and endogenous protoporphyrin IX

The study of the interaction of synthetic protoporphyrin IX (PpIXs) and protoporphyrin IX extracted from Harderian glands of ssp Rattus novergicus albinus rats (PpIXe) with bovine serum albumin (BSA) was conducted in water at pH 7.3 and pH 4.5 by optical absorption and fluorescence spectroscopies. PpIXs is present as H- and J-aggregates in equilibrium with themselves and with monomers. The PpIXs charge is 2- at pH 7.3 and 1- at pH 4.5. This increases its aggregation at pH 4.5 and shifts the equilibrium in favor of J-aggregates. In spite of electrostatic attraction at pH 4.5, where BSA is positive, the binding constant (Kb) of PpIXs to BSA is 20% less than that at pH 7.3, where BSA is negative. This occurs because higher aggregation of PpIXs at pH 4.5 reduces the observed Kb value. At both pHs, water-soluble PpIXe exists in the monomeric form with the charge of 1- and its Kb exceeds that of PpIXs. At pH 4.5, its Kb is 12 times higher than that at pH 7.3 due to electrostatic attraction between the positively charged BSA and the negatively charged PpIXe. The higher probability of PpIXe binding to BSA makes PpIXe more promising as a fluorescence probe for fluorescence diagnostics and as a photosensitizer for photodynamic therapy. The existence of PpIXe in the monomeric form can explain its faster cell internalization. Aggregation reduces quantum yields and lifetimes of the PpIXs excited states, which explains higher phototoxicity of PpIXe toward malignant cells compared with PpIXs.

Dual-modal polypeptide-containing contrast agents for magnetic resonance/fluorescence imaging

Dual-modal magnetic resonance/fluorescent imaging (MRI/FI) attracts moreandmoreattentions in diagnosis of tumors. A corresponding dual-modal imaging agent with sufficient tumor sensitivity and specificity should be matched to improve imaging quality. Tripeptide (RGD) and pentapeptide (YIGSR) were selected as the tumor-targeting groups and attached to gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) and rhodamine B (RhB), and then make two novel polypeptide-based derivatives (RGD-Gd-DTPA-RhB and YIGSR-Gd-DTPA-RhB), respectively. These derivatives were further characterized and their properties, such as cell uptake, cell cytotoxicity, MRI and FI assay, were measured. YIGSR-Gd-DTPA-RhB and RGD-Gd-DTPA-RhB had high relaxivity, good tumor-targeting property, low cell cytotoxicity and good red FI in B16F10 melanoma cells. Moreover, YIGSR-Gd-DTPA-RhB and RGD-Gd-DTPA-RhB possessed high uptake to B16F10 melanoma, and then achieve highly enhanced FI and MRI of tumors in mice for a prolonged time. Therefore, YIGSR-Gd-DTPA-RhB and RGD-Gd-DTPA-RhB can be applied as the potential agents for tumor targeted MRI/FI in vivo.

Comprehensive Picture of the Excited State Dynamics of Cu(I)- and Ru(II)-Based Photosensitizers with Long-Lived Triplet States

Ru(II)- and Cu(I)-based photosensitizers featuring the recently developed biipo ligand (16H-benzo-[4',5']-isoquinolino-[2',1',:1,2]-imidazo-[4,5-f]-[1,10]-phenanthrolin-16-one) were comprehensively investigated by X-ray crystallography, electrochemistry, and especially several time-resolved spectroscopic methods covering all time scales from femto- to milliseconds. The analysis of the experimental results is supported by density functional theory (DFT) calculations. The biipo ligand consists of a coordinating 1,10-phenanthroline moiety fused with a 1,8-naphthalimide unit, which results in an extended π-system with an incorporated electron acceptor moiety. In a previous study, it was shown that this ligand enabled a Ru(II) complex that is an efficient singlet oxygen producer and of potential use for other light-driven applications due to its long emission lifetime. The goal of our here presented research is to provide a full spectroscopic picture of the processes that follow optical excitation. Interestingly, the Ru(II) and Cu(I) complexes differ in their characteristics even though the lowest electronically excited states involve in both cases the biipo ligand. The combined spectroscopic results indicate that an emissive ³MLCT state and a rather dark ³LC state are populated, each to some extent. For the Cu(I) complex, most of the excited population ends up in the ³LC state with an extraordinary lifetime of 439 μs in the solid state at 20 K, while a significant population of the ³MLCT state causes luminescence for the Ru(II) complex. Hence, there is a balance between these two states, which can be tuned by altering the metal center or even by thermal energy, as suggested by the temperature-dependent experiments.