Thiol-Responsive Polypeptide Sulfur Dioxide Prodrug Nanoparticles for Effective Tumor Inhibition

Multicomponent Polymerization toward Poly(BODIPY-sulfonamide)s as Unique SO2 Generators for Sonodynamic and Gas Combination Therapy

In this work, a multicomponent polymerization (MCP) approach involving bipyrroles, sulfonyl azides, and diynes was developed to afford a library of poly(bipyrrole-sulfonylimide)s (PPSIs) in high yields and molecular weights, which were further modified to form unique sulfur dioxide (SO2) generators. Bipyrroles served as carbon-based nucleophiles to undergo Cu-catalyzed C-C coupling during the MCP. Upon post-MCP modification by transforming the bipyrrole unit to boron dipyrromethene (BODIPY) and the sulfonylimide moiety to sulfonamide, poly(BODIPY-sulfonamide)s (PBSAs) were obtained as potent anticancer therapeutic agents. This study disclosed the decomposition and SO2-releasing ability of PBSAs under ultrasound (US) irradiation. Furthermore, one of these polymers having a reactive oxygen species-cleavable thioketal linker was modified with triethylene glycol chains to give PBSA-EG, which was further studied for in vitro and in vivo US-induced anti-cancer therapy. Upon tail veil administration of PBSA-EG nanoparticles into tumor-bearing mice followed by US irradiation, remarkable tumor suppression was observed. This study demonstrates that the innovative and efficient MCP method can construct polymers bearing the BODIPY-sulfonamide moieties, which show a great potential as safe and potent materials for combined gas and sonodynamic therapy against cancer.

Activatable Sulfur Dioxide Nanosonosensitizer Enables Precisely Controllable Sono-Gaseous Checkpoint Trimodal Therapy for Orthotopic Hepatocellular Carcinoma

Immune checkpoint blockade (ICB) is combined with sonodynamic therapy (SDT) to increase response rates and enhance anticancer efficacy. However, the "always on" property of most sonosensitizers in reducing tumor microenvironment (TME) compromises the therapeutic outcome of sonoimmunotherapy and exacerbates adverse side effects. Precisely controllable strategies combining sulfur dioxide (SO2) gas therapy with cancer immunotherapy can address these issues but remain lacking. Herein an "activatable SO2 nanosonosensitizer" for precise sono-gaseous checkpoint trimodal therapy of orthotopic hepatocellular carcinoma (HCC) is reported, whose full activity is initiated by ultrasound (US) irradiation in the reducing TME. This "activatable SO2 nanosonosensitizer," Aza-DNBS nanoparticles (NPs), are established by self-assembling Aza-boron-dipyrromethene based sonosensitizer molecules and 2,4-dinitrobenzenesulfonate (DNBS)-caged SO2 prodrug. The activity of Aza-DNBS NPs is initially silenced, and the sonodynamic, gaseous, and immunosuppressive TME reprogramming activities are precisely awakened under US irradiation. Due to the glutathione-responsiveness of Aza-DNBS NPs, Aza-DNBS NPs can generate large amounts of SO2 for gas therapy-enhanced SDT, which triggers robust immunogenic cell death activation and reprogramming of the immunosuppressive TME, thereby significantly suppressing orthotopic tumor growth and delaying lung metastasis. Thus, this study represents a strategy for designing a generic nanoplatform for precisely combined immunotherapy of orthotopic HCC.

Polymeric Nanoarchitectures: Advanced Cargo Systems for Biological Applications

Polymeric nanoarchitectures are crafted from amphiphilic block copolymers through a meticulous self-assembly process. The composition of these block copolymers is finely adjustable, bestowing precise control over the characteristics and properties of the resultant polymeric assemblies. These nanoparticles have garnered significant attention, particularly in the realm of biological sciences, owing to their biocompatibility, favorable pharmacokinetics, and facile chemically modifiable nature. Among the myriad of polymeric nanoarchitectures, micelles and polymersomes stand out as frontrunners, exhibiting much potential as cargo carrier systems for diverse bio-applications. This review elucidates the design strategies employed for amphiphilic block copolymers and their resultant assemblies, specifically focusing on micelles and polymersomes. Subsequently, it discusses their wide-ranging bio-applications, spanning from drug delivery and diagnostics to bioimaging and artificial cell applications. Finally, a reflective analysis will be provided, highlighting the current landscape of polymeric cargo carriers, and discussing the opportunities and challenges that lie ahead. With this review, it is aimed to summarize the recent advances in polymeric assemblies and their applications in the biomedical field.

Rational Design of Self-Reporting Polymersomes for the Controlled Release of Sulfur Dioxide

As a new member of the gaseous regulators, sulfur dioxide (SO2) plays a crucial role in many biological activities. Recent studies have shown that SO2 is capable of inducing cancer cell apoptosis by regulating intracellular reactive oxygen species (ROS), allowing SO2 to serve as an efficient therapeutic agent. Although various polymer-based platforms have presented great potential for the controlled release of SO2, most of the systems are incapable of monitoring the intracellular generation of SO2. In this work we present the rational design of SO2-releasing biodegradable polymersomes, accompanied by a self-reporting property. The polymersome consists of a hydrophilic block of poly(ethylene glycol) (PEG) and a hydrophobic segment of poly(trimethylene carbonate) (PTMC)-based SO2 donors. The polymersomes not only exhibit good SO2-releasing performance upon treatment with glutathione (GSH), but can also regulate the fluorescence change of the system, offering a good platform for real-time monitoring of the intracellular production of SO2. Significantly, the in vitro and in vivo studies indicate the potential for exploitation of these polymersomes as antitumor agents. We expect that incorporating both the SO2-releasing capacity and self-reporting feature within a polymersome system will provide a unique opportunity for the development of intelligent gas nanovehicles.

Gas immnuo-nanomedicines fight cancers

Certain gas molecules, including hydrogen (H2), nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S), oxygen (O2) and sulfur dioxide (SO2) exhibit significant biological functionalities that can modulate the immune response. Strategies pertaining to gas-based immune therapy have garnered considerable attention in recent years. Nevertheless, delivering various gas molecules precisely into tumors, which leads to enhanced anti-tumor immunotherapeutic effect, is still a main challenge. The advent of gas treatment modality with desirable immunotherapeutic efficiency has been made possible by the rapid development of nanotechnology, which even derives the concept of the gas immnuo-nanomedicines (GINMs). In light of the fact, we herein aim to furnish a cutting-edge review on the latest progress of GINMs. The underlying mechanisms of action for several gases utilized in cancer immunotherapy are initially outlined. Additionally, it provides a succinct overview of the current clinical landscape of gas therapy, and introduces GINMs specifically designed for cancer treatment based on immunotherapeutic principles across multiple strategies. Last but not least, we address the challenges and opportunities associated with GINMs, exploring the potential future developments and clinical applications of this innovative approach.

A chemically engineered water-soluble block copolymer for redox responsive SO2 release in antibacterial therapy

Sulfur dioxide (SO2) has emerged as a promising gasotransmitter for various therapeutic applications, including antibacterial activities. However, the potential of polymeric SO2 donors for antimicrobial activities remains largely unexplored. Herein, we report a water-soluble, redox-responsive, SO2-releasing amphiphilic block copolymer poly(polyethylene glycol methyl ether methacrylate) (PPEGMA)-b-poly(2-((2,4-dinitrophenyl)sulfonamido)ethyl methacrylate (PM)) (BCPx) to investigate their antibacterial properties. BCPx contains hydrophilic polyethylene glycol (PEG) pendants and a hydrophobic SO2-releasing PM block, facilitating the formation of self-assembled nanoparticles (BCPxNp) in an aqueous medium, studied by critical aggregation concentration (CAC) measurements, dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). BCPxNp exhibits sustained SO2 release up to 12 h in the presence of glutathione (GSH), with a yield of 30-80% of theoretical SO2 release. In vitro antibacterial studies unveil the outstanding antibacterial activity of BCP3Np against Gram-positive bacteria Bacillus subtilis, as evidenced by FESEM and live/dead cell fluorescence assay. We further elucidate the antibacterial mechanism through reactive oxygen species (ROS) generation studies. Overall, the polymer exhibits excellent biocompatibility at effective antimicrobial concentrations and provides insights into the design of a new class of SO2-releasing polymeric antibacterial agents.

A Novel Polyamino Acid Sulfur Dioxide Prodrug Synergistically Elevates ROS with β-Lapachone in Cancer Treatment

Due to the distorted redox balance, cancer cells are considered more vulnerable to excessive reactive oxygen species (ROS). In a variety of oxidative stress-related therapies, gas therapy has emerged as a new therapeutic strategy owing to its efficacy and biosafety. Herein, a newly-discovered gasotransmitter sulfur dioxide (SO2) and a tumor specific ROS generation agent β-lapachone (Lapa) were firstly combined for anticancer therapy. Firstly, amphiphilic glutathione (GSH) responsive polypeptide SO2 prodrug PEG-b-poly(Lys-DNs) was synthesized by ring opening polymerization of SO2-containing N-carboxyanhydride. Then, Lapa was encapsulated into the polymeric micelles with loading content of 8.6 % and loading efficiency of 51.6 %. The obtained drug-loaded nanoparticles (NPs(Lapa)) exhibited a fast release of Lapa and SO2 in the stimuli of 10 mM GSH in PBS. Subsequently, in vitro experiment showed that NPs(Lapa) exhibited obvious cytotoxicity towards 4 T1 cancer cells at a concentration of 2.0 μg/mL, which may be attributed to the depletion of intracellular GSH and upregulation of ROS level both by SO2 release and by the ROS generation from lapachone transformation. In vivo fluorescence imaging showed that the NPs were gradually enriched in tumor tissues in 24 h, probably due to the enhanced permeability and retention effect of NPs. Finally, NPs(Lapa) showed the best anticancer effect in 4 T1 tumor bearing mice with a tumor inhibiting rate (IRT) of 61 %, whereas IRT for free Lapa group was only 23.6 %. This work may be a new attempt to combine SO2 gas therapy with ROS inducer for anticancer therapy through oxidative stress.

A Novel Cu(II) Loaded Polypeptide SO2 Prodrug Nanoformulation Combining Chemodynamic and Gas Anticancer Therapies

Sulfur dioxide (SO2)-based gas therapy and chemodynamic therapyare both reactive oxygen species (ROS)-mediated anticancer strategies, but there are few reports of their combined application. To this end, a novel graft-type copolymeric SO2 prodrug, PLG-g-mPEG-DNs, is designed and synthesized in this work. The amphiphilic polypeptides can self-assemble into nanoparticles (NPs) and encapsulated Cu(II) ions by metal-carboxyl coordination. In vitro release results showed that the obtained NPs-Cu can respond to the acidic pH and high glutathione levels typical of a tumor microenvironment to release Cu(II) and SO2 simultaneously. Both a Cu(II)-triggered Fenton-like reaction and the SO2 gas would promote ROS production and upregulate the oxidative stress in tumor cells, leading to an enhanced killing effect towards 4T1 cancer cells compared to either Cu(II) or the NPs alone. Furthermore, the in vitro hemolysis of NPs-Cu is less than 1.0% at a high concentration of 8 mg/mL, indicating good blood compatibility and the potential for in vivo tumor inhibition application.

Recent advances in sulfur dioxide releasing nanoplatforms for cancer therapy

Sulfur dioxide (SO2), long considered to be a harmful atmospheric pollutant, has recently been posited as the fourth gasotransmitter, as it is produced endogenously in mammals and has important pathophysiological effects. The field of tumor therapy has witnessed a paradigm shift with the emergence of SO2-based gas therapy. This has been possible because SO2 is a potent glutathione consumer that can promote the production of reactive oxygen species, eventually leading to oxidative-stress-induced cancer cell death. Nevertheless, this therapeutic gas cannot be directly administrated in gaseous form. Thus, various nano formulations incorporating SO2 donors or prodrugs capable of storing and releasing SO2 have been developed in an attempt to achieve active/passive intratumoral accumulation and SO2 release in the tumor microenvironment. In this review article, the advances over the past decade in nanoplatforms incorporating sulfur SO2 prodrugs to provide controlled release of SO2 for cancer therapy are summarized. We first describe the synthesis of polypeptide SO2 prodrugs to overcome multiple drug resistance that was pioneered by our group, followed by other macromolecular SO2 prodrug structures that self-assemble into nanoparticles for tumor therapy. Second, we describe nanoplatforms composed of various small-molecule SO2 donors with endogenous or exogenous stimuli responsiveness, including thiol activated, acid-sensitive, and ultraviolet or near-infrared light-responsive SO2 donors, which have been used for tumor inhibition. Combinations of SO2 gas therapy with photodynamic therapy, chemotherapy, photothermal therapy, sonodynamic therapy, and nanocatalytic tumor therapy are also presented. Finally, we discuss the current limitations and challenges and the future outlook for SO2-based gas therapy. STATEMENT OF SIGNIFICANCE: Gas therapy is attracting increasing attention in the scientific community because it is a highly promising strategy against cancer owing to its inherent biosafety and avoidance of drug resistance. Sulfur dioxide (SO2) is recently found to be produced endogenously in mammals with important pathophysiological effects. This review summarizes recent advances in SO2 releasing nanosystems for cancer therapy, including polymeric prodrugs, endogenous or exogenous stimulus-activated SO2 donors delivered by nanoplatform and combination therapy strategies.

Sulfur signaling pathway in cardiovascular disease

Hydrogen sulfide (H2S) and sulfur dioxide (SO2), recognized as endogenous sulfur-containing gas signaling molecules, were the third and fourth molecules to be identified subsequent to nitric oxide and carbon monoxide (CO), and exerted diverse biological effects on the cardiovascular system. However, the exact mechanisms underlying the actions of H2S and SO2 have remained elusive until now. Recently, novel post-translational modifications known as S-sulfhydration and S-sulfenylation, induced by H2S and SO2 respectively, have been proposed. These modifications involve the chemical alteration of specific cysteine residues in target proteins through S-sulfhydration and S-sulfenylation, respectively. H2S induced S-sulfhydrylation can have a significant impact on various cellular processes such as cell survival, apoptosis, cell proliferation, metabolism, mitochondrial function, endoplasmic reticulum stress, vasodilation, anti-inflammatory response and oxidative stress in the cardiovascular system. Alternatively, S-sulfenylation caused by SO2 serves primarily to maintain vascular homeostasis. Additional research is warranted to explore the physiological function of proteins with specific cysteine sites, despite the considerable advancements in comprehending the role of H2S-induced S-sulfhydration and SO2-induced S-sulfenylation in the cardiovascular system. The primary objective of this review is to present a comprehensive examination of the function and potential mechanism of S-sulfhydration and S-sulfenylation in the cardiovascular system. Proteins that undergo S-sulfhydration and S-sulfenylation may serve as promising targets for therapeutic intervention and drug development in the cardiovascular system. This could potentially expedite the future development and utilization of drugs related to H2S and SO2.