Folic Acid-Conjugated Radioluminescent Calcium Tungstate Nanoparticles as Radio-Sensitizers for Cancer Radiotherapy

Current and future directions in interventional neuro-oncology-are we there yet?

Advancements in technology and technical expertise increasingly enable neurointerventionalists to deliver safer and more effective endovascular treatments to cancers of the brain, spine, head, and neck. In addition to established neuro-oncological interventions such as pre-surgical tumor embolization and percutaneous ablation, newer modalities focused on direct arterial infusion of chemotherapy, radioisotopes, and radiosensitizers continue to gain traction as complementary treatment options, while stem cell-mediated delivery of theranostic nanoparticles and oncolytic virus are being explored for even greater specificity in targeting cancers across the blood-brain barrier. This article aims to provide an overview of the current state of the art and future directions for the field of interventional neuro-oncology, as well as opportunities and challenges presented by this emerging treatment modality.

The Impact of Nanomedicine on Soft Tissue Sarcoma Treated by Radiotherapy and/or Hyperthermia: A Review

This article presents a comprehensive review of nanoparticle-assisted treatment approaches for soft tissue sarcoma (STS). STS, a heterogeneous group of mesenchymal-origin tumors with aggressive behavior and low overall survival rates, necessitates the exploration of innovative therapeutic interventions. In contrast to conventional treatments like surgery, radiotherapy (RT), hyperthermia (HT), and chemotherapy, nanomedicine offers promising advancements in STS management. This review focuses on recent research in nanoparticle applications, including their role in enhancing RT and HT efficacy through improved drug delivery systems, novel radiosensitizers, and imaging agents. Reviewing the current state of nanoparticle-assisted therapies, this paper sheds light on their potential to revolutionize soft tissue sarcoma treatment and improve patient therapy outcomes.

Radiation-induced photodynamic therapy using calcium tungstate nanoparticles and 5-aminolevulinic acid prodrug

Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) prodrug is a clinically tried and proven treatment modality for surface-level lesions. However, its use for deep-seated tumors has been limited due to the poor penetration depth of visible light needed to activate the photosensitizer protoporphyrin IX (PPIX), which is produced from ALA metabolism. Herein, we report the usage of poly(ethylene glycol-b-lactic acid) (PEG-PLA)-encapsulated calcium tungstate (CaWO4, CWO for short) nanoparticles (PEG-PLA/CWO NPs) as energy transducers for X-ray-activated PDT using ALA. Owing to the spectral overlap between radioluminescence afforded by the CWO core and the absorbance of PPIX, these NPs can serve as an in situ visible light activation source during radiotherapy (RT), thereby mitigating the limitation of penetration depth. We demonstrate that this effect is observed across different cell lines with varying radio-sensitivity. Importantly, both PPIX and PEG-PLA/CWO NPs exhibit no significant toxicities at therapeutic doses in the absence of radiation. To assess the efficacy of this approach, we conducted a study using a syngeneic mouse model subcutaneously implanted with inherently radio-resistant 4T1 tumors. The results show a significantly improved prognosis compared to conventional RT, even with as few as 2 fractions of 4 Gy X-rays. Taken together, these results suggest that PEG-PLA/CWO NPs are promising agents for application of ALA-PDT in deep-seated tumors, thereby significantly expanding the utility of the already established treatment strategy.

Combining Radiotherapy (RT) and Photodynamic Therapy (PDT): Clinical Studies on Conventional RT-PDT Approaches and Novel Nanoparticle-Based RT-PDT Approaches under Preclinical Evaluation

Radiotherapy (RT) is the primary standard of care for many locally advanced cancers. Often times, however, the efficacy of RT is limited due to radio-resistance that cancer cells develop. Photodynamic therapy (PDT) has gained importance as an alternative local therapy. Because its mechanism involves minimal acquired resistance, PDT is a useful adjunct to RT. This review discusses recent advances in combining RT with PDT for cancer treatment. In the first part of this review, we will discuss clinical trials on RT + PDT combination therapies. All these approaches suffer from the same inherent limitations as any current PDT methods; (i) visible light has a short penetration depth in human tissue (<∼10 mm), and (ii) it is difficult to illuminate the entire tumor homogeneously by external/interstitial laser irradiation. To address these limitations, scintillating nanoparticle-mediated RT-PDT approaches have been explored in which nanoparticles convert X-rays (RT) into visible light (PDT); high-energy X-rays can reach deep into the body to irradiate cancers uniformly and precisely. The second part of this review will discuss recent efforts in developing and applying nanoparticles for RT-PDT applications.

Effect of Paclitaxel Stereochemistry on X-ray-Triggered Release of Paclitaxel from CaWO4/Paclitaxel-Coloaded PEG-PLA Nanoparticles

For many locally advanced tumors, the chemotherapy-radiotherapy (CT-RT) combination ("chemoradiation") is currently the standard of care. Intratumoral (IT) CT-based chemoradiation has the potential to overcome the limitations of conventional systemic CT-RT (side effects). For maximizing the benefits of IT CT-RT, our laboratory has previously developed a radiation-controlled drug release formulation, in which anticancer drug paclitaxel (PTX) and radioluminescent CaWO₄ (CWO) nanoparticles (NPs) are co-encapsulated with poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) block copolymers ("PEG-PLA/CWO/PTX NPs"). These PEG-PLA/CWO/PTX NPs enable radiation-controlled release of PTX and are capable of producing sustained therapeutic effects lasting for at least one month following a single IT injection. The present article focuses on discussing our recent finding about the effect of the stereochemical structure of PTX on the efficacy of this PEG-PLA/CWO/PTX NP formulation. Stereochemical differences in two different PTX compounds ("PTX-S" from Samyang Biopharmaceuticals and "PTX-B" from Biotang) were characterized by 2D heteronuclear/homonuclear NMR, Raman spectroscopy, and circular dichroism measurements. The difference in PTX stereochemistry was found to significantly influence their water solubility (WS); PTX-S (WS ≈ 4.69 μg/mL) is about 19 times more water soluble than PTX-B (WS ≈ 0.25 μg/mL). The two PTX compounds showed similar cancer cell-killing performances in vitro when used as free drugs. However, the subtle stereochemical difference significantly influenced their X-ray-triggered release kinetics from the PEG-PLA/CWO/PTX NPs; the more water-soluble PTX-S was released faster than the less water-soluble PTX-B. This difference was manifested in the IT pharmacokinetics and eventually in the survival percentages of test animals (mice) treated with PEG-PLA/CWO/PTX NPs + X-rays in an in vivo human tumor xenograft study; at short times (<1 month), concurrent PEG-PLA/CWO/PTX-S NPs produced a greater tumor-suppression effect, whereas PEG-PLA/CWO/PTX-B NPs had a longer-lasting radio-sensitizing effect. This study demonstrates the importance of the stereochemistry of a drug in a therapy based on a controlled release formulation.

A GdW10@PDA-CAT Sensitizer with High-Z Effect and Self-Supplied Oxygen for Hypoxic-Tumor Radiotherapy

Anticancer treatment is largely affected by the hypoxic tumor microenvironment (TME), which causes the resistance of the tumor to radiotherapy. Combining radiosensitizer compounds and O2 self-enriched moieties is an emerging strategy in hypoxic-tumor treatments. Herein, we engineered GdW10@PDA-CAT (K3Na4H2GdW10O36·2H2O, GdW10, polydopamine, PDA, catalase, CAT) composites as a radiosensitizer for the TME-manipulated enhancement of radiotherapy. In the composites, Gd (Z = 64) and W (Z = 74), as the high Z elements, make X-ray gather in tumor cells, thereby enhancing DNA damage induced by radiation. CAT can convert H2O2 to O2 and H2O to enhance the X-ray effect under hypoxic TME. CAT and PDA modification enhances the biocompatibility of the composites. Our results showed that GdW10@PDA-CAT composites increased the efficiency of radiotherapy in HT29 cells in culture. This polyoxometalates and O2 self-supplement composites provide a promising radiosensitizer for the radiotherapy field.

Identification and elimination of cancer cells by folate-conjugated CdTe/CdS Quantum Dots Chiral Nano-Sensors

The specific identification and elimination of cancer cells has been a great challenge in the past few decades. In this study, the circular dichroism (CD) of cells was measured by a self-designed special system through the folate-conjugated chiral nano-sensor. A novel method was established to recognize cancer cells from normal cells according to the chirality of cells based on their CD signals. After a period of interaction between the nano-sensor and cells, the sharp weakening of CD signals was induced in cancer cells but normal cells remained unchanged. The biocompatibility of the nano-sensor was evaluated and the result showed that it exhibited significant cytotoxic activity against cancer cells while no obvious damage on normal cells. Notably, the research indicated that the nano-sensor may selectively cause apoptosis in cancer cells, and thus, have the potential to act as an antitumor agent.

Investigating the reactive oxygen species production of Rose Bengal and Merocyanine 540-loaded radioluminescent nanoparticles

Radioluminescent nanomaterials have garnered significant attention in the past decade due to their potential to perform X-ray mediated photodynamic therapy (X-PDT). Many of these materials are assumed to produce singlet oxygen based on a single assay. Herein we demonstrate that multiple assays are required to confidently determine whether singlet oxygen or other reactive oxygen species are being produced through type I or type II PDT mechanisms. Rose Bengal and Merocyanine 540 photosensitizers were loaded into mesoporous silica-coated NaLuF4:Dy3+,Gd3+ nanoparticles and the combination of ABDA, DPBF, and NaN3 assays along with electron paramagnetic resonance were employed to determine that superoxide and hydroxyl radicals were exclusively produced from this system under X-ray excitation. Knowledge of the correct PDT mechanism is crucial for informing what types of disease may be best suited for treatment using PDT nanosystems.

pH-Sensitive Folic Acid Conjugated Alginate Nanoparticle for Induction of Cancer-Specific Fluorescence Imaging

In cancer nanomedicine, numerous studies have been conducted on the surface modification and transport capacity of nanoparticles (NPs); however, biological barriers, such as enzymatic degradation or non-specific delivery during circulation, remain to be cleared. Herein, we developed pH-sensitive NPs that degrade in an acidic environment and release 5-aminolevulinic acid (5ALA) to the target site. NPs were prepared by conjugating alginate with folic acid, followed by encapsulation of 5ALA through a water-in-oil (W/O) emulsion method. The alginate-conjugated folic acid nanoparticles (AF NPs) were homogeneous in size, stable for a long time in aqueous suspension without aggregation, and non-toxic. AF NPs were small enough to efficiently infiltrate tumors (<50 nm) and were specifically internalized by cancer cells through receptor-mediated endocytosis. After the intracellular absorption of NPs, alginate was deprotonated in the lysosomes and released 5ALA, which was converted to protoporphyrin IX (PpIX) through mitochondrial heme synthesis. Our study outcomes demonstrated that AF NPs were not degraded by enzymes or other external factors before reaching cancer cells, and fluorescent precursors were specifically and accurately delivered to cancer cells to generate fluorescence.