Target-Specific Magnetic Resonance Imaging of Human Prostate Adenocarcinoma Using NaDyF4-NaGdF4 Core-Shell Nanoparticles

Sodium lanthanide tungstate-based nanoparticles as bimodal contrast agents for in vivo high-field MRI and CT imaging

Research on high-field magnetic resonance imaging (HF-MRI) has been increased in recent years, aiming to improve diagnosis accuracy by increasing the signal-to-noise ratio and hence image quality. Conventional contrast agents (CAs) have important limitations for HF-MRI, with the consequent need for the development of new CAs. Among them, the most promising alternatives are those based on Dy3+ or Ho3+ compounds. Notably, the high atomic number of lanthanide cations would bestow a high capability for X-ray attenuation to such Dy or Ho-based compounds, which would also allow them to be employed as CAs for X-ray computed tomography (CT). In this work, we have prepared uniform NaDy(WO4)2 and NaHo(WO4)2 nanoparticles (NPs), which were dispersible under conditions that mimic the physiological media and were nontoxic for cells, meeting the main requirements for their use in vivo. Both NPs exhibited satisfactory magnetic relaxivities at 9.4 T, thus making them a promising alternative to clinical CAs for HF-MRI. Furthermore, after their intravenous administration in tumor-bearing mice, both NPs exhibited significant accumulation inside the tumor at 24 h, attributable to passive targeting by the enhanced permeability and retention (EPR) effect. Therefore, our NPs are suitable for the detection of tumors through HF-MRI. Finally, NaDy(WO4)2 NPs showed a superior X-ray attenuation capability than iohexol (commercial CT CA), which, along with their high r2 value, makes them suitable as the dual-probe for both HF-MRI and CT imaging, as demonstrated by in vivo experiments conducted using healthy mice.

Application of H2N-Fe3O4 Nanoparticles for Prostate Cancer Magnetic Resonance Imaging in an Animal Model

This paper presents the efficacy of a contrast agent based on H2N-Fe3O4 nanoparticles for the detection of prostate cancer in an animal model using a preclinical 9.4 T MRI system. The relaxivities r1 and r2 of the nanoparticles were 6.31 mM-1s-1 and 8.33 mM-1s-1, respectively. Nanoparticles injected in a concentration of 2 mg Fe/mL decreased the tumor-relative T1 relaxation across all animals from 100 to 76 ± 26, 85 ± 27, 89 ± 20, and 97 ± 16 12 min 1 h, 2 h, and 24 h post injection, respectively. The corresponding T1 decrease in muscle tissues was 90 ± 20, 94 ± 23, 99 ± 12, and 99 ± 14. The relative T2 changes in the tumor were 82 ± 17, 89 ± 19, 97 ± 14, and 99 ± 8 12 min, 1 h, 2 h, and 24 h post injection, respectively, while, for muscle tissues, these values were 95 ± 11, 95 ± 8, 97 ± 6, and 95 ± 10 at the corresponding time points. The differences in the relative T1 and T2 were only significant 12 min after injection (p < 0.05), although a decrease was visible at each time point, but it was statistically insignificant (p > 0.05). The results showed the potential application of H2N-Fe3O4 nanoparticles as contrast agents for enhanced prostate cancer MRI.

Biomimetic Theranostic Agents with Superior NIR-II Photoacoustic and Magnetic Resonance Imaging Performance for Targeted Photothermal Therapy of Prostate Cancer

The accurate diagnosis and treatment of prostate cancer at an early stage is crucial to reduce mortality rates. However, the limited availability of theranostic agents with active tumor-targeting abilities hinders imaging sensitivity and therapeutic efficiency. To address this challenge, we have developed biomimetic cell membrane-modified Fe₂O₃ nanoclusters implanted in polypyrrole (CM-LFPP), achieving photoacoustic/magnetic resonance dual-modal imaging-guided photothermal therapy of prostate cancer. The CM-LFPP exhibits strong absorption in the second near-infrared window (NIR-II, 1000-1700 nm), showing high photothermal conversion efficiency of up to 78.7% under 1064 nm laser irradiation, excellent photoacoustic imaging capabilities, and good magnetic resonance imaging ability with a T2 relaxivity of up to 48.7 s^-1 mM^-1. Furthermore, the lipid encapsulation and biomimetic cell membrane modification enable CM-LFPP to actively target tumors, leading to a high signal-to-background ratio of ~30.2 for NIR-II photoacoustic imaging. Moreover, the biocompatible CM-LFPP enables low-dose (0.6 W cm^-2) photothermal therapy of tumors under 1064 nm laser irradiation. This technology offers a promising theranostic agent with remarkable photothermal conversion efficiency in the NIR-II window, providing highly sensitive photoacoustic/magnetic resonance imaging-guided prostate cancer therapy.

Contrast Enhancement in MRI Using Combined Double Action Contrast Agents and Image Post-Processing in the Breast Cancer Model

Gd- and Fe-based contrast agents reduce T₁ and T₂ relaxation times, respectively, are frequently used in MRI, providing improved cancer detection. Recently, contrast agents changing both T₁/T₂ times, based on core/shell nanoparticles, have been introduced. Although advantages of the T₁/T₂ agents were shown, MR image contrast of cancerous versus normal adjacent tissue induced by these agents has not yet been analyzed in detail as authors considered changes in cancer MR signal or signal-to-noise ratio after contrast injection rather than changes in signal differences between cancer and normal adjacent tissue. Furthermore, the potential advantages of T₁/T₂ contrast agents using image manipulation such as subtraction or addition have not been yet discussed in detail. Therefore, we performed theoretical calculations of MR signal in a tumor model using T₁-weighted, T₂-weighted, and combined images for T₁-, T₂-, and T₁/T₂-targeted contrast agents. The results from the tumor model are followed by in vivo experiments using core/shell NaDyF₄/NaGdF₄ nanoparticles as T₁/T₂ non-targeted contrast agent in the animal model of triple negative breast cancer. The results show that subtraction of T₂-weighted from T₁-weighted MR images provides additional increase in the tumor contrast: over two-fold in the tumor model and 12% in the in vivo experiment.