Inorganic phosphate-triggered release of anti-cancer arsenic trioxide from a self-delivery system: an in vitro and in vivo study

Drug self-delivery systems: A comprehensive review on small molecule nanodrugs

Drug self-delivery systems are nanostructures composed of a drug as the main structural unit, having the ability of intracellular trafficking with no additional carrier. In these systems, the drug itself undertakes the functional and structural roles; thereby, the ancillary role of excipients and carrier-related limitations are circumvented and therapeutic effect is achieved at a much lower dose. Such advantages -which are mainly but not exclusively beneficial in cancer treatment- have recently led to an upsurge of research on these systems. Subsequently, various terminologies were utilized to describe them, referring to the same concept with different words. However, not all the systems developed based on the self-delivery approach are introduced using one of these keywords. Using a scoping strategy, this review aims to encompass the systems that have been developed as yet -inspired by the concept of self-delivery- and classify them in a coherent taxonomy. Two main groups are introduced based on the type of building blocks: small molecule-based nanomedicines and self-assembling hybrid prodrugs. Due to the diversity, covering the whole gamut of topics is beyond the scope of a single article, and, inevitably, the latter is just briefly introduced here, whereas the features of the former group are meticulously presented. Depending on whether the drug is merely a carrier for itself or carries a second drug as cargo, two classes of small molecule-based nanomedicines are defined (i.e., pure nanodrugs and carrier-mimicking systems, respectively), each having sub-branches. After introducing each branch and giving some examples, possible strategies for designing each particular system are visually displayed. The resultant mind map can create a macro view of the taken path and its prospects, give a profound insight into opportunities, spark new ideas, and facilitate overcoming obstacles. Taken together, one can foresee a brilliant future for self-delivery systems as a pioneering candidate for the next generation of drug delivery systems.

Maximizing arsenic trioxide's anticancer potential: Targeted nanocarriers for solid tumor therapy

Arsenic trioxide (ATO) has gained significant attention due to its promising therapeutic effects in treating different diseases, particularly acute promyelocytic leukemia (APL). Its potent anticancer mechanisms have been extensively studied. Despite the great efficacy ATO shows in fighting cancers, drawbacks in the clinical use are obvious, especially for solid tumors, which include rapid renal clearance and short half-life, severe adverse effects, and high toxicity to normal cells. Recently, the emergence of nanomedicine offers a potential solution to these limitations. The enhanced biocompatibility, excellent targeting capability, and desirable effectiveness have attracted much interest. Therefore, we summarized various nanocarriers for targeted delivery of ATO to solid tumors. We also provided detailed anticancer mechanisms of ATO in treating cancers, its clinical trials and shortcomings as well as the combination therapy of ATO and other chemotherapeutic agents for reduced drug resistance and synergistic effects. Finally, the future study direction and prospects were also presented.

Nanocarrier-based delivery of arsenic trioxide for hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC) poses a severe threat to human health and economic development. Despite many attempts at HCC treatment, most are inevitably affected by the genetic instability and variability of tumor cells. Arsenic trioxide (ATO) has shown to be effective in HCC. However, time-consuming challenges, especially the optimal concentration in tumor tissue and bioavailability of ATO, remain to be overcome for its transition from the bench to the bedside. To bypass these issues, nanotechnology-based delivery systems have been developed for prevention, diagnosis, monitoring and treatment in recent years. This article is a systematic overview of the latest contributions and detailed insights into ATO-loaded nanocarriers, with particular attention paid to strategies for improving the efficacy of nanocarriers of ATO.

MMP2-responsive dual-targeting drug delivery system for valence-controlled arsenic trioxide prodrug delivery against hepatic carcinoma

Arsenic trioxide (ATO) is the active ingredient in traditional Chinese medicine, i.e., Arsenic, which has shown excellent therapeutic effects on hepatocellular carcinoma. However, due to its poor tumor distribution and high toxicity, the mass adoption of ATO in clinical applications has been severely impeded. In this study, matrix metalloproteinase 2 (MMP2)-responsive cleaved cell-penetrating peptide (PF) and folate (FA) co-modified liposome coated calcium arsenate nanoparticles (FA/PF-LP-CaAs) were fabricated based on these two considerations: (1) The tumor microenvironment characterized by overexpressed MMP2 in extracellular matrix and folate receptor on the cell membrane can enhance drug accumulation and accelerate endocytosis; (2) leveraging different toxicity of arsenic in different valence states, i.e., AsV can be reduced to more toxic AsIII by glutathione in tumor cells. Furthermore, FA/PF-LP-CaAs could be responsively degraded by the mild acidic tumor environment, and the degraded product could escape from lysosomes after endocytosis. More importantly, in light of the in vivo biodistribution and pharmacodynamic studies, the vehicle was able to accumulate in the tumor efficiently. Also, it was able to exhibit excellent anti-tumor efficacy with minimized side effects when compared to single-modified counterparts. Thus, the novel strategy based on the tumor microenvironment proposed in this work can enhance the tumor-targeting efficiency and intratumor toxicity.

A practical strategy to subcutaneous administered in-situ gelling co-delivery system of arsenic and retinoic acid for the treatment of acute promyelocytic leukemia

Arsenic trioxide (ATO) combined with all trans retinoic acid (ATRA) is the first choice for the treatment of low and medium risk acute promyelocytic leukemia (APL). Clinical studies reported that the combination of ATO and ATRA could achieve a significant curative effect. However, the retinoic acid syndrome, serious drug resistance and the short half-life in vivo which lead to frequent and large dose administration limit the application of ATRA. In addition, the preparations of arsenic are conventional injections and tablets in clinic, which has poor patients' compliance caused by frequent long-term administration and serious side effects. In order to overcome the above limitations, a phospholipid phase separation gel (PPSG) loaded with ATO and ATRA was developed. ATO+ATRA-PPSG (AAP), as a biodegradable sustained-release delivery system, was the first achievement of co-delivery of hydrophilic ATO and lipophilic ATRA with high drug loading which is the main problem in the application of nano preparation. The prepared PPSG displayed high safety and biocompatibility. The drug in PPSG was released slowly and continuously in vivo and in vitro for up to 10 d, which could reduce the side effects caused by the fluctuation of blood drug concentration and solve the problem of the long treatment cycle and frequent administration. In vivo pharmacokinetics depicted that PPSG could improve the bioavailability, decrease the peak concentration, and prolong the t1/2 of ATO and ATRA. Particularly, AAP significantly inhibited the tumor volume, extended the survival period of tumor-bearing mice, and promoted the differentiation of APL cells into normal cells. Therefore, ATO+ATRA-PPSG not only could co-load hydrophilic ATO and lipophilic ATRA according to the clinical dosage, but also possessed the sustained-release and long-acting treatment effect which was expected to reduce administration time and ameliorate compliance of patients. Thus, it had great potential for clinical transformation and application.

Current status and future prospects of nanomedicine for arsenic trioxide delivery to solid tumors

Despite having a rich history as a poison, arsenic and its compounds have also gained a great reputation as promising anticancer drugs. As a pioneer, arsenic trioxide has been approved for the treatment of acute promyelocytic leukemia. Many in vitro studies suggested that arsenic trioxide could also be used in the treatment of solid tumors. However, the transition from bench to bedside turned out to be challenging, especially in terms of the drug bioavailability and concentration reaching tumor tissues. To address these issues, nanomedicine tools have been proposed. As nanocarriers of arsenic trioxide, various materials have been examined including liposomes, polymer, and inorganic nanoparticles, and many other materials. This review gives an overview of the existing strategies of delivery of arsenic trioxide in cancer treatment with a focus on the drug encapsulation approaches and medicinal impact in the treatment of solid tumors. It focuses on the progress in the last years and gives an outlook and suggestions for further improvements including theragnostic approaches and targeted delivery.

Construction of arsenic-metal complexes loaded nanodrugs for solid tumor therapy: A mini review

Arsenic trioxide (As₂O₃), a front-line therapeutic agent against acute promyelocytic leukemia, has a broad spectrum against malignancies. Unfortunately, the clinical application of As₂O₃ in treating hematological cancers has not been transformed to solid tumors, for its dose-limited toxicity and undesirable pharmacokinetics. The ordinary As₂O₃ loaded nanodrugs (such as liposomes, polymer micelles, albumin-based nanodrugs, and silica-based nanodrugs, etc.) still could not fuel up pharmaceuticals and eradicate toxicity for low delivery efficiency caused by the instability and severe drug leakage of formulations during circulation. Recently, the approach of forming and delivering arsenic-metal complexes which will dissociate in the tumoral environment caught our mind. This is the most effective strategy to reduce drug leakage in circulation and accumulate arsenite ions in tumor sites, therefore promote the anti-tumor effect and lighten the toxicity of the drug. This review aims to explain the formation mechanism of arsenic-metal nanocomposites and summarize the constructing strategies of the arsenic-metal nanocomplexes (arsenic-nickel, arsenic-manganese, arsenic-platinum, arsenic-gadolinium, arsenic-zinc, and arsenic-iron nanobins) loaded nanodrugs for solid tumor therapy. Furthermore, the expectations and challenges of arsenic-metal complexes containing nanodrugs for cancer therapy in the future were discussed.

Integrin αvβ3 Receptor Overexpressing on Tumor-Targeted Positive MRI-Guided Chemotherapy

Multifunctional nanomaterials with targeted imaging and chemotherapy have high demand with great challenge. Herein, we rationally aimed to design multifunctional drug delivery systems by RGD-modified chitosan (CH)-coated nanoneedles (NDs) of gadolinium arsenate (RGD-CH-Gd-AsNDs). These NDs have multifunctionality for imaging and targeted therapy. NDs on intravenous administration demonstrated significant accumulation of As ions/species in tumor tissues, which was monitored by the change in T₁-weighted magnetic resonance (MR) imaging. Moreover, NDs were well opsonized in cells with high specificity, subsequently inducing apoptosis to the HepG2 cells. Consequent to this, the in vivo results demonstrated biosafety, enhanced tumor targeting, and tumor regression in a subcutaneously transplanted xenograft model in nude mice. These RGD-CH-Gd-AsNDs have great potential, and we anticipate that they could serve as a novel platform for real-time T₁-weighted MR diagnosis and chemotherapy.

Nanosized drug-eluting bead for transcatheter arterial chemoembolization (ND-TACE)

Dextran-coated arsenite nanoparticles benefit interventional therapy by occluding tumor feeding vessels and sustainable release of arsenic trioxide.

Sustained release of arsenic trioxide benefits interventional therapy on rabbit VX2 liver tumor

The benefit of chemotherapy as a constituent of transcatheter arterial chemoembolization (TACE) is still in debate. Recently we have developed arsenic trioxide nanoparticle prodrug (ATONP) as a new anticancer drug, but its systemic toxicity is a big issue. In this preclinical TACE study, ATONP emulsified in lipiodol behaved as drug-eluting bead manner. Sustained release of arsenic from ATONP within occluded tumor caused very low arsenic level in plasma, avoiding the "rushing out" effect as ATO did. Correspondingly, intratumoral arsenic accumulation and inorganic phosphate deprivation were simultaneously observed, and arsenic concentration was much higher as ATONP was transarterially administered than ATO, or intravenously injected. Tumor necrosis and apoptosis were remarkably more severe in ATONP group than ATO, but no significant hepatic and renal toxicity was perceived. In brief, ATONP alleviated arsenic toxicity and boosted the therapeutic effect of TACE via Pi-activated drug sustainable release.

Targeted arsenite-loaded magnetic multifunctional nanoparticles for treatment of hepatocellular carcinoma

Arsenic trioxide (ATO), an FDA-approved drug for acute promyelocytic leukemia, also has great potential for treatment of solid tumors. Drug delivery powered by recent advances in nanotechnology has boosted the efficacy of many drugs, which is enlightening for applications of ATO in treating solid tumors. Herein, we reported arsenite-loaded multifunctional nanoparticles that are capable of pH-responsive ATO release for treating hepatocellular carcinoma (HCC) and real-time monitoring via magnetic resonance imaging. We fabricated these nanoparticles (designated as magnetic large-pore mesoporous silica nanoparticle (M-LPMSN)-NiAsO _x ) by loading nanoparticulate ATO prodrugs (NiAsO _x ) into the pores of large-pore mesoporous silica nanoparticles (LPMSNs) that contain magnetic iron oxide nanoparticles in the center. The surface of these nanodrugs was modified with a targeting ligand folic acid (FA) to further enhance the drug efficacy. Releasing profiles manifest the responsive discharging of arsenite in acidic environment. In vitro experiments with SMMC-7721 cells reveal that M-LPMSN-NiAsO _x -FA nanodrugs have significantly higher cytotoxicity than traditional free ATO and induce more cell apoptosis. In vivo experiments with mice bearing H22 tumors further confirm the superior antitumor efficacy of M-LPMSN-NiAsO _x -FA over traditional free ATO and demonstrate the outstanding imaging ability of M-LPMSN-NiAsO _x -FA for real-time tumor monitoring. These targeted arsenite-loaded magnetic mesoporous silica nanoparticles integrating imaging and therapy hold great promise for treatment of HCC, indicating the auspicious potential of LPMSN-based nanoplatforms.

Development of colloidal rare-earth arsenites as arsenic trioxide nanoparticle prodrugs (ATONP) for chemotherapy on a patient-derived xenograft model of colorectal cancer

Rare earth arsenite colloids, acting as arsenic trioxide nanoparticle prodrugs, effectively arrested cancer growth in a patient-derived colorectal xenograft model.

An arsenic trioxide nanoparticle prodrug (ATONP) potentiates a therapeutic effect on an aggressive hepatocellular carcinoma model via enhancement of intratumoral arsenic accumulation and disturbance of the tumor microenvironment

An arsenic trioxide nanoparticle prodrug has a therapeutic effect on a transgenic liver cancer model by disturbing the tumor micro-environment and increasing the delivery efficiency.

Photodynamic therapy-mediated remote control of chemotherapy toward synergistic anticancer treatment

Stimuli-responsive nanomedicine (NM) with an on-demand drug release property has demonstrated promising utility toward cancer therapy. However, sensitivity and cancer selectivity still remain critical challenges for intelligent NM, which will compromise its therapeutic efficacy and lead to undesired toxicity to normal tissues. Herein, we report a convenient and universal approach to spatiotemporally control the chemodrug release via the photodynamic therapy (PDT)-mediated alteration of the tumor microenvironment. An arylboronic ester (BE)-modified amphiphilic copolymer (mPEG-PBAM) was designed to form micelles and encapsulate doxorubicin (Dox) and hematoporphyrin (Hp). The Dox/Hp co-encapsulated micelles (PB-DH) were stable under normal physiological environment with a uniform size distribution (∼100 nm). In contrast, under tumor-specific light irradiation, extensive reactive oxygen species (ROS) will be generated from Hp in the tumor sites, thus quickly dissociating the micelles and selectively releasing the chemodrug Dox as a consequence of the ROS-mediated cleavage of the hydrophobic BE moieties on the polymers. As such, synergistic anti-cancer efficacy was achieved between the Dox-mediated chemotherapy and the Hp-mediated PDT. This study therefore provides a useful approach to realize the precise and selective control over chemodrug delivery, and it renders promising utilities for the programmable combination of PDT and chemotherapy.

Arsenite-loaded nanoparticles inhibit the invasion and metastasis of a hepatocellular carcinoma: in vitro and in vivo study

Postoperative recurrence and metastasis are the major problems for the current treatment of hepatocellular carcinomas (HCC) in the clinic, including hepatectomy and liver transplantation. Here, we report that arsentic-loaded nanoparticles (ALNPs) are able to reduce the invasion of HCC cells in vitro, and, more importantly, can strongly suppress the invasion and metastasis of HCC in vivo without adverse side effects. Compared to free drug arsenic trioxide , ALNPs can deliver the drug into cancer cells more efficiently, destroy the structure of microtubules and reduce the aggregation of microfilaments in cell membranes more significantly. Furthermore, our results also reveal that tumor cells in murine blood were reduced remarkably after intravenous injection of ALNPs, indicating that this nano-drug may efficiently kill circulating tumor cells in vivo. In conclusion, our nano-drug ALNPs have great potential for the suppression of metastasis of HCC, which may open up a new avenue for the effective treatment of HCC without metastasis and recurrence.