Iodine containing porous organosilica nanoparticles trigger tumor spheroids destruction upon monochromatic X-ray irradiation: DNA breaks and K-edge energy X-ray

X-ray-Induced Photodegradation of Hydrogels by the Incorporation of X-ray-Activated Long Persistent Luminescent Nanoparticles

The development of on-demand degradable hydrogels remains an important challenge. Even though photodegradable hydrogels offer spatiotemporal control over degradation, it is difficult to use ultraviolet, visible, or near-infrared light as a tool for noninvasive triggering in vivo due to the poor tissue-penetration capacity. In contrast, X-ray irradiation can penetrate deep tissue and has virtually no penetration limitations for biological soft tissues. In this study, we propose an X-ray-photodegradation cascade system for hydrogel degradation by incorporating X-ray-activated persistent luminescence nanoparticles (X-PLNPs) into photodegradable hydrogels. A photodegradable 9,10-dialkoxyanthracene-based cross-linker was synthesized and used to prepare photodegradable hydrogels, of which the degradation behavior can be triggered by visible green light. Next, Tb3+-doped β-NaLuF4 was introduced as an X-PLNP that can convert X-rays into visible light centered at 544 nm. The afterglow can even be detected for 4 × 103 s after switching off the X-ray irradiation. The X-ray-induced green light emission was demonstrated to trigger photodegradation of the hydrogel. This proof-of-concept system for X-ray irradiation-induced on-demand hydrogel degradation was used to demonstrate X-ray-sensitive drug delivery inside a chicken breast as the in vitro tissue model. As this X-ray-induced cascade degradation of hydrogels can penetrate deep tissues, it is a promising platform for future in vivo applications requiring on-demand triggered hydrogel degradation, such as drug delivery or removal of hydrogel patches, hydrogel adhesives, or hydrogel tissue engineering scaffolds. It should, however, be noted that the hydrogel's X-ray and photoresponsiveness should be further improved to enable future in vivo use.

Radiosensitization of Rare-Earth Nanoparticles Based on the Consistency Between Its K-Edge and the X-Ray Bremsstrahlung Peak

Nanoparticle-based X-ray radiosensitization strategies have garnered significant attention in recent years. However, the underlying mechanisms of radiosensitization remain incompletely understood. In this work, we explore the influence of the K-edge effect in the X-ray absorption of nanomaterials on sensitization. Due to the alignment of the K-edge of thulium (Tm) with the Bremsstrahlung peak in the energy spectrum of medical X-ray accelerators, the following four different rare-earth nanomaterials with varying Tm percentages were designed: NaTmF4, NaTm0.6Lu0.4F4, NaTm0.4Lu0.6F4, and NaLuF4. We evaluated the X-ray absorption and the ability to generate secondary electrons and reactive oxygen species (ROS) of these nanoparticles. The radiosensitizing effect was evaluated through clonogenic assays. Our results showed that the K-edge effect affected secondary electron generation but did not significantly change ROS production. Nonetheless, NaTmF4 induced marginally more DNA damage in the U87 cells than the other cell types. NaTmF4 also exhibited superior radiosensitization efficacy against the U87 tumor cells. This shows that secondary electrons and ROS play pivotal roles in radiosensitization, which might be crucial to improving cancer treatment efficacy through enhanced radiation therapy outcomes.

Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions

Biomolecular radiation damage is largely mediated by radicals and low-energy electrons formed by water ionization rather than by direct ionization of biomolecules. It was speculated that such an extensive, localized water ionization can be caused by ultrafast processes following excitation by core-level ionization of hydrated metal ions. In this model, ions relax via a cascade of local Auger-Meitner and, importantly, non-local charge- and energy-transfer processes involving the water environment. Here, we experimentally and theoretically show that, for solvated paradigmatic intermediate-mass Al3+ ions, electronic relaxation involves two sequential solute-solvent electron transfer-mediated decay processes. The electron transfer-mediated decay steps correspond to sequential relaxation from Al5+ to Al3+ accompanied by formation of four ionized water molecules and two low-energy electrons. Such charge multiplication and the generated highly reactive species are expected to initiate cascades of radical reactions.

Trend in biodegradable porous nanomaterials for anticancer drug delivery

In recent years, biodegradable nanomaterials have exhibited remarkable promise for drug administration to tumors due to their high drug-loading capacity, biocompatibility, biodegradability, and clearance. This review will discuss and summarize the trends in utilizing biodegradable nanomaterials for anticancer drug delivery, including biodegradable periodic mesoporous organosilicas (BPMOs) and metal-organic frameworks (MOFs). The distinct structure and features of BPMOs and MOFs will be initially evaluated, as well as their use as delivery vehicles for anticancer drug delivery applications. Then, the themes for the development of each material will be utilized to illustrate their drug delivery performance. Finally, the current obstacles and potential for future development as efficient drug delivery systems will be thoroughly reviewed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Inhibition of DNA synthesis and cancer therapies

Cancer is a worldwide problem afflicting 19 million people. Inhibition of DNA synthesis has been a cornerstone of anticancer therapy. A variety of chemotherapy drugs have been developed and many of these are aimed at inhibiting DNA synthesis, as they damage DNA, form DNA adduct and interfere with DNA synthesis. Another type of chemotherapy interferes with the synthesis of nucleotide pools. There are also other types of drugs that inhibit topoisomerases resulting in the interference with DNA replication and transcription. Significant progress has been made regarding radiation therapy that includes X-ray (and γ-ray), proton therapy and heavy ion therapy. The Auger therapy is a type of radiation therapy that differs from X-ray, proton or heavy ion therapy. The method relies on the use of high Z elements such as gadolinium, iodine, gold or silver. Irradiation of these elements results in the release of electrons including the Auger electrons that have strong DNA damaging effect. Tamanoi et al. developed novel nanoparticles containing gadolinium or iodine to place high Z elements at the periphery of the nucleus thus localizing them close to DNA. Irradiation with monochromatic X-ray resulted in the formation of double-strand DNA breaks leading to the destruction of tumor mass. Comparison of conventional X-ray therapy and the Auger therapy is discussed.

Auger electrons and DNA double-strand breaks studied by using iodine-containing chemicals

Irradiation of high Z elements such as iodine, gold, gadolinium with monochromatic X-rays causes photoelectric effects that include the release of Auger electrons. Decay of radioactive iodine such as I-123 and I-125 also results in multiple events and some involve the generation of Auger electrons. These electrons have low energy and travel only a short distance but have a strong effect on DNA damage including the generation of double-strand breaks. In this chapter, we focus on iodine and discuss various studies that used iodine-containing chemicals to generate Auger electrons and cause DNA double-strand breaks. First, DNA synthesis precursors containing iodine were used to place iodine on DNA. DNA binding dyes such as iodine Hoechst were investigated for Auger electron generation and DNA breaks. More recently, iodine containing nanoparticles were developed. We describe our study using tumor spheroids loaded with iodine nanoparticles and synchrotron-generated monochromatic X-rays. This study led to the demonstration that an optimum effect on DNA double-strand break formation is observed with a 33.2keV X-ray which is just above the K-edge energy of iodine.

Fiber-Optic Based Laser Wakefield Accelerated Electron Beams and Potential Applications in Radiotherapy Cancer Treatments

Ultra-compact electron beam technology based on laser wakefield acceleration (LWFA) could have a significant impact on radiotherapy treatments. Recent developments in LWFA high-density regime (HD-LWFA) and low-intensity fiber optically transmitted laser beams could allow for cancer treatments with electron beams from a miniature electronic source. Moreover, an electron beam emitted from a tip of a fiber optic channel could lead to new endoscopy-based radiotherapy, which is not currently available. Low-energy (10 keV–1 MeV) LWFA electron beams can be produced by irradiating high-density nano-materials with a low-intensity laser in the range of ~1014 W/cm2. This energy range could be useful in radiotherapy and, specifically, brachytherapy for treating superficial, interstitial, intravascular, and intracavitary tumors. Furthermore, it could unveil the next generation of high-dose-rate brachytherapy systems that are not dependent on radioactive sources, do not require specially designed radiation-shielded rooms for treatment, could be portable, could provide a selection of treatment energies, and would significantly reduce operating costs to a radiation oncology clinic.

Multifunctional high-Z nanoradiosensitizers for multimodal synergistic cancer therapy

Radiotherapy (RT) is one of the most common and effective clinical therapies for malignant tumors. However, there are several limitations that undermine the clinical efficacy of cancer RT, including the low X-ray attenuation coefficient of organs, serious damage to normal tissues, and radioresistance in hypoxic tumors. With the rapid development of nanotechnology and nanomedicine, high-Z nanoradiosensitizers provide novel opportunities to overcome radioresistance and improve the efficacy of RT by deposition of radiation energy through photoelectric effects. To date, several types of nanoradiosensitizers have entered clinical trials. Nevertheless, the limitation of the single treatment mode and the unclear mechanism of nanoparticle radiosensitization have hindered the further development of nanoradiosensitizers. In this review, we systematically describe the interaction mechanisms between X-rays and nanomaterials and summarize recent advances in multifunctional high-Z nanomaterials for radiotherapeutic-based multimodal synergistic cancer therapy. Finally, the challenges and prospects are discussed to stimulate the development of nanomedicine-based cancer RT.