Precise engineering of disulfide bond-bridged prodrug nanoassemblies to balance antitumor efficacy and safety

Updated pharmaceutical progress on plant antibiotic rhein and its analogs: Bioactivities, structure-activity relationships and future perspectives

Rhein, as a plant antibiotic, demonstrates a broad spectrum of pharmacological effects. Nevertheless, its limited water solubility, low bioavailability, and potential hepatotoxicity and nephrotoxicity making it difficult to directly become a medicine, thereby imposing significant constraints on its clinical application. In recent decades, extensive researches have been proceeded on the multifaceted structural modifications of rhein, resulting in notable improvements on pharmacological activities and druggabilities. This review offers a comprehensive overview and advanced update on the biological potential and structural-activity relationships (SARs) of various rhein derivatives, delineating the sites of structural modification and corresponding activity trends of rhein derivatives for future.

Cholesterol sulfate-mediated ion-pairing facilitates the self-nanoassembly of hydrophilic cationic mitoxantrone

HYPOTHESIS

Hydrophilic cationic drugs such as mitoxantrone hydrochloride (MTO) pose a significant delivery challenge to the development of nanodrug systems. Herein, we report the use of a hydrophobic ion-pairing strategy to enhance the nano-assembly of MTO.

EXPERIMENTS

We employed biocompatible sodium cholesteryl sulfate (SCS) as a modification module to form stable ion pairs with MTO, which balanced the intermolecular forces and facilitated nano-assembly. PEGylated MTO-SCS nanoassemblies (pMS NAs) were prepared via nanoprecipitation. We systematically evaluated the effect of the ratio of the drug module (MTO) to the modification module (SCS) on the nanoassemblies.

FINDINGS

The increased lipophilicity of MTO-SCS ion pair could significantly improve the encapsulation efficiency (∼97 %) and cellular uptake efficiency of MTO. The pMS NAs showed prolonged blood circulation, maintained the same level of tumor antiproliferative activity, and exhibited reduced toxicity compared with the free MTO solution. It is noteworthy that the stability, cellular uptake, cytotoxicity, and in vivo pharmacokinetic behavior of the pMS NAs increased in proportion to the molar ratio of SCS to MTO. This study presents a self-assembly strategy mediated by ion pairing to overcome the challenges commonly associated with the poor assembly ability of hydrophilic cationic drugs.

Carbon-Spaced Tandem-Disulfide Bond Bridge Design Addresses Limitations of Homodimer Prodrug Nanoassemblies: Enhancing Both Stability and Activatability

Redox-responsive homodimer prodrug nanoassemblies (RHPNs) have emerged as a significant technology for overcoming chemotherapeutical limitations due to their high drug-loading capacity, low excipient-associated toxicity, and straightforward preparation method. Previous studies indicated that α-position disulfide bond bridged RHPNs exhibited rapid drug release rates but unsatisfactory assembly stability. In contrast, γ-disulfide bond bridged RHPNs showed better assembly stability but low drug release rates. Therefore, designing chemical linkages that ensure both stable assembly and rapid drug release remains challenging. To address this paradox of stable assembly and rapid drug release in RHPNs, we developed carbon-spaced double-disulfide bond (CSDD)-bridged RHPNs (CSDD-RHPNs) with two carbon-spaces. Pilot studies showed that CSDD-RHPNs with two carbon-spaces exhibited enhanced assembly stability, reduction-responsive drug release, and improved selective toxicity compared to α-/γ-position single disulfide bond bridged RHPNs. Based on these findings, CSDD-RHPNs with four and six carbon-spaces were designed to further investigate the properties of CSDD-RHPNs. These CSDD-RHPNs exhibited excellent assembly ability, safety, and prolonged circulation. Particularly, CSDD-RHPNs with two carbon-spaces displayed the best antitumor efficacy on 4T1 and B16-F10 tumor-bearing mice. CSDD chemical linkages offer novel perspectives on the rational design of RHPNs, potentially overcoming the design limitations regarding contradictory assembly ability and drug release rate.

Research Progress of Disulfide Bond Based Tumor Microenvironment Targeted Drug Delivery System

Cancer poses a significant threat to human life and health. Chemotherapy is currently one of the effective cancer treatments, but many chemotherapy drugs have cell toxicity, low solubility, poor stability, a narrow therapeutic window, and unfavorable pharmacokinetic properties. To solve the above problems, target drug delivery to tumor cells, and reduce the side effects of drugs, an anti-tumor drug delivery system based on tumor microenvironment has become a focus of research in recent years. The construction of a reduction-sensitive nanomedicine delivery system based on disulfide bonds has attracted much attention. Disulfide bonds have good reductive responsiveness and can effectively target the high glutathione (GSH) levels in the tumor environment, enabling precise drug delivery. To further enhance targeting and accelerate drug release, disulfide bonds are often combined with pH-responsive nanocarriers and highly expressed ligands in tumor cells to construct drug delivery systems. Disulfide bonds can connect drug molecules and polymer molecules in the drug delivery system, as well as between different drug molecules and carrier molecules. This article summarized the drug delivery systems (DDS) that researchers have constructed in recent years based on disulfide bond drug delivery systems targeting the tumor microenvironment, disulfide bond cleavage-triggering conditions, various drug loading strategies, and carrier design. In this review, we also discuss the controlled release mechanisms and effects of these DDS and further discuss the clinical applicability of delivery systems based on disulfide bonds and the challenges faced in clinical translation.

Minor Changes in Response Modules Leading to a "U-Shaped" Conversion Rate of Docetaxel Prodrug Nanoassemblies

The prodrug-based nanoassemblies offer an alternative to settle the deficiencies of traditional chemotherapy drugs. In this nanosystem, prodrugs typically comprise drug modules, modification modules, and response modules. The response modules are crucial for facilitating the accurate conversion of prodrugs at specific sites. In this work, we opted for differentiated disulfide bonds as response modules to construct docetaxel (DTX) prodrug nanoassemblies. Interestingly, a subtle change in response modules leads to a "U-shaped" conversion rate of DTX-prodrug nanoassemblies. Prodrug nanoassemblies with the least carbon numbers between the disulfide bond and ester bond (PDONα) offered the fastest conversion rate, resulting in powerful treatment outcomes with some unavoidable toxic effects. PDONβ, with more carbon numbers, possessed a slow conversion rate and poor antitumor efficacy but good tolerance. With most carbon numbers in PDONγ, it demonstrated a moderate conversion rate and antitumor effect but induced a risk of lethality. Our study explored the function of response modules and highlighted their importance in prodrug development.

Nanosized Assemblies from Amphiphilic Solanesol Derivatives for Anticancer Drug Delivery

Unexpected functionalities of pharmaceutical excipients have been found in some cases. Preplanned introduction of excipients with therapeutic effects might not only reduce the risks of metabolism-related toxicity but also provide synergistic therapeutic effects. Herein, natural original solanesol (SOL), one of the isoprene compounds with some pharmacological activities, was selected to prepare a series of amphiphilic derivatives by chemical modification, and drug delivery systems for oncotherapy were established. Three derivatives, including solanesyl bromide (SOL-Br), monosolanesolsolanesyl succinate (MSS), and solanesylthiosalicylate (STS), were synthesized and formulated into nanosized self-assemblies for doxorubicin (DOX) encapsulation. Meanwhile, polyethylene glycol (PEG) derivatives were synthesized as the stabilizer of solanesol-based self-assemblies, among which hydrazine-poly(ethylene glycol)-hydrazine (PEG6000-DiHZ) was found to be more reliable. The optimized molar ratio between PEG6000-DiHZ and solanesol derivatives was found to be 2:1, considering the drug-loading capacity of self-assemblies. Consistent release profiles were found for the DOX-loaded self-assemblies, in which about 75-80% DOX was cumulatively released within 60 h at pH 5.0. The three DOX-loaded self-assemblies were found to be homogeneous spheres with average particle sizes in the range of 100-200 nm by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Blank self-assemblies were found to have an inhibiting ability toward MCF-7 and HepG-2 cancer cells, which might originate from the inherent nature of solanesol derivatives. In vivo pharmacodynamic experiments demonstrated that blank self-assemblies had certain inhibitory effect on tumor growth compared with the controls. Further enhanced effects were also found for the drug-loaded self-assemblies due to the synergistic anti-tumor effect existing between the drug and the carriers. This work has presented a simple and effective strategy to prepare a therapeutic carrier by direct assembling of the therapeutic compound without PEGylation steps, by which the therapeutic carrier materials could take their effect directly and synergistically along with the loaded drugs.

Cleavable-Branched Polymer-Modified Liposomes Reduce Accelerated Blood Clearance and Enhance Photothermal Therapy

In recent years, cationic liposomes have been successfully used as delivery platforms for mRNA vaccines. Poly(ethylene glycol) (PEG)-lipid derivatives are widely used to enhance the stability and reduce the toxicity of cationic liposomes. However, these derivatives are often immunogenic, triggering the rise of anti-PEG antibodies. Understanding the role and impact of PEG-lipid derivatives on PEGylated cationic liposomes is key to solving the PEG dilemma. In this study, we designed linear, branched, and cleavable-branched cationic liposomes modified with PEG-lipid derivatives and investigated the effect of the liposome-induced accelerated blood clearance (ABC) phenomenon on photothermal therapy. Our study indicated that the linear PEG-lipid derivatives mediated the effect of photothermal therapy by stimulating splenic marginal zone (MZ) B cells to secrete anti-PEG antibodies and increasing the level of IgM expression in the follicular region of the spleen. However, the cleavable-branched and branched PEG-lipid derivatives did not activate the complement system and avoided the ABC phenomenon by inducing noticeably lower levels of anti-PEG antibodies. The cleavable-branched PEGylated cationic liposomes improved the effect of photothermal therapy by reversing the charge on the liposome surface. This detailed study of PEG-lipid derivatives contributes to the further development and clinical application of PEGylated cationic liposomes.