pH/ROS Dual-Responsive Supramolecular Vesicles Fabricated by Carboxylated Pillar[6]arene-Based Host-Guest Recognition and Phenylboronic Acid Pinacol Ester Derivative

Supramolecular Polymers for Drug Delivery

Supramolecular polymers are constructed through highly reversible and directionally specific non-covalent interactions between monomer units. This unique feature enables supramolecular polymers to undergo controlled structural reconfiguration and functional transformation in response to external stimuli, imparting them with high environmental responsiveness and self-healing properties. In particular, supramolecular polymers exhibit several specific advantages compared to conventional polymers, such as inherent degradability, the ease of preparation and the incorporation of functional units, and smart responsiveness to various biological stimuli. These characters make supramolecular polymers promising candidates for intelligent drug delivery systems in complex biological environments. In this review, we comprehensively summarize the latest developments and representative achievements of supramolecular polymers in drug delivery fields, focusing primarily on the design and synthesis, the properties and functionalities, and the practical applications of supramolecular polymers in small molecule drug delivery, gene therapy, and protein delivery. Finally, we highlight future research directions, focusing on multifunctionality, adaptability, and personalized therapy. We focus on recent studies that address key challenges in the field, providing rational polymer design, important properties, functionality, and understanding delivery strategies. These developments are expected to advance supramolecular polymers as new platforms of intelligent drug delivery systems, offering innovative solutions for the treatment of complex diseases.

ROS-responsive phenylboronic ester-based nanovesicles as multifunctional drug delivery systems for the treatment of inflammatory and thrombotic complications

Inflammatory and thrombotic complications and a low loading of dual drugs with different hydrophilicities remain challenges to treat thrombosis with drug delivery systems (DDSs). Here, the reactive oxygen species (ROS)-responsive amphiphilic block polymer poly(ethylene glycol)-b-2-((((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)carbonyl)oxy)-ethyl methacrylate (PEG-b-PTBEM) was synthesized and nanovesicles (PPTV) were prepared successfully for the drug delivery platform by controlling the hydrophilic/hydrophobic ratio of molecular chains and molecular self-assembly. The anti-inflammatory drug indomethacin (IDM) was loaded in the wall of nanovesicles and the thrombolytic enzyme nattokinase (NK) was encapsulated in the aqueous cavity of nanovesicles. Both drugs could be rapidly released at the site of thrombosis and/or inflammation with an excessive ROS concentration. The dual drug-loaded nanovesicles not only eliminated ROS, but also alleviated inflammation and dissolved the generated thrombus, showing significant therapeutic efficacy in the in vivo mouse model of carrageenan tail thrombosis. Therefore, drug-delivery nanovesicles play multiple roles in the treatment of inflammation-induced thrombotic disorders, which offer a promising treatment for inflammatory and thrombotic complications.

Stabilization of Antitumor Agent Busulfan through the Encapsulation within a Water-Soluble Pillar[5]arene

The complexation of antitumor agent busulfan by negatively charged carboxylatopillar[5]arenein water is reported. The encapsulation within carboxylatopillar[5]arenein reduces the hydrolytic degradation of busulfan from 90.7 % to 25.2 % after 24 days and accordingly enhances its stability by providing a hydrophobic shelter for busulfan in water. Moreover, the complexation result in 12 times improvement of water solubility for busulfan. Our result provides a supramolecular approach for stabilizing the anticancer agent busulfan.

Detection of aliphatic aldehydes by a pillar[5]arene-based fluorescent supramolecular polymer with vaporchromic behavior

The detection of volatile aliphatic aldehydes is of significance because of their chemical toxicity, physical volatility and widespread applications in chemical industrial processes. In this work, the direct detection of aliphatic aldehydes is tackled using a fluorescent supramolecular polymer with vaporchromic behavior which is contructed by pillar[5]arene-based host-guest intereactions. Thin films with strong orange-yellow fluorescence are prepared by coating the linear supramolecular polymer on glass sheets. When the thin films are exposed to aliphatic aldehydes with different carbon chain lengths, they can selectivly sensing  n -butyraldehyde ( C 4 ) and caprylicaldehyde ( C 8 ), accompanied by fluorescence quenching, indicating that the supramolecular polymer is a highly selective vapochromic response material for aliphatic aldehydes with long alkyl chains.

Glutathione sensitive vesicles prepared from supramolecular amphiphiles

Glutathione (GSH) sensitive vesicles were prepared by the self-assembly of amphiphilic inclusion complexes. These novel chemically sensitive supramolecular amphiphiles are anticipated to have applications in drug delivery; the nanocarriers can protect the encapsulated cargo and release it via triggered degradation in high concentrations of GSH. Additionally, the sensitivity of the vesicles to GSH indicates that the dynamic covalent disulfide bond at the vesicle surface can be used for post-modification of the nanocarrier via a thiol-disulfide exchange, a strategy that can be exploited to introduce targeting moieties to increase treatment specificity. Supramolecular amphiphiles containing a dynamic covalent disulfide bond were prepared via the host-guest inclusion complexes between alkylated β-cyclodextrin (β-CD) hosts and adamantane terminated polyethylene glycol derivatives. The significant difference between the critical micelle concentrations of the supramolecular amphiphiles and the individual host and guest components confirmed that a unique supramolecular amphiphile was formed. Fluorescence experiments and dynamic light scattering (DLS) revealed that the supramolecular amphiphiles self-assembled into vesicles of 130 nm diameter which were stable for 8 months. Degradation of the vesicles after incubation with GSH was monitored using DLS and by the release of encapsulated 5,6-carboxyfluorescein (CF), observed by an increase in fluorescence intensity. Degradation of the nanocarrier was faster at intracellular GSH concentrations than at extracellular GSH concentrations.

Reactive oxygen species-sensitive polymeric nanocarriers for synergistic cancer therapy

Reactive oxygen species (ROS)-responsive nanocarriers have aroused widespread interest in recent years. On the one hand, a high ROS level has been detected in many types of tumor cells. On the other hand, ROS generation is also induced during photodynamic, sonodynamic, or chemodynamic therapy. In addition, multiple types of polymers are sensitive to ROS. Therefore, numerous ROS-responsive polymeric nanocarriers with unique ROS-responsive characteristics have been developed. This review discusses ROS-sensitive polymeric nanocarriers to improve drug delivery efficacy. In particular, ROS-responsive nanocarriers for synergistic cancer therapy are highlighted. The development of novel ROS-sensitive nanocarriers holds great potential for combining ROS-mediated therapy, such as photodynamic therapy, and other therapies to achieve synergistic anticancer efficacy. STATEMENT OF SIGNIFICANCE: Reactive oxygen species (ROS)-responsive nanocarriers aroused widespread interest in recent years. On the one hand, a high level of ROS has been found in many types of tumor cells. On the other hand, the ROS generation can also be induced during the photodynamic, sonodynamic, or chemodynamic therapy. Besides, multiple types of polymers were sensitive to the ROS. Therefore, numerous ROS-responsive polymeric nanocarriers with unique ROS responsive characteristics have been developed. This review focuses on the ROS-sensitive polymeric nanocarriers to improve drug delivery efficacy for synergistic cancer therapy.

Enzyme-Responsive Molecular Assemblies Based on Host-Guest Chemistry

Recent years have witnessed a growing interest in the design of enzyme-responsive molecular assemblies that hold appealing applications in the fields of disease-related sensing, imaging, and drug delivery. Cyclodextrins (CDs) are amylase-cleavable host molecules that can associate with surfactants, alkanes, alkyl amines, fatty alcohols, and aromatic compounds to form diverse supramolecular structures. In this work, we report a versatile supramolecular platform to construct enzyme-responsive nanosystems via host-guest interactions, in which complexation between CDs and surfactants eventually leads to the formation of a variety of nanostructures such as vesicles and microtubes. These supramolecular structures are capable of loading water-soluble molecules or functional nanoparticles, which can be actively released on-demand in the presence of α-amylase. This universal strategy to fabricate enzyme-responsive supramolecular systems was further demonstrated with a range of surfactants with anionic, cationic, and nonionic headgroups. Our results highlight a versatile platform for the exploration of biologically responsive self-assembly with potential applications as controlled-release systems and microrobots.

Enhanced Antitumor Efficacy through an "AND gate" Reactive Oxygen-Species-Dependent pH-Responsive Nanomedicine Approach

Anticancer drug delivery strategies are designed to take advantage of the differential chemical environment in solid tumors independently, or to high levels of reactive oxygen species (ROS) or to low pH, compared to healthy tissue. Here, the design and thorough characterization of two functionalizable "AND gate" multiresponsive (MR) block amphiphilic copolymers are reported, aimed to take full advantage of the coexistence of two chemical cues-ROS and low pH-present in the tumor microenvironment. The hydrophobic blocks contain masked pH-responsive side chains, which are exposed exclusively in response to ROS. Hence, the hydrophobic polymer side chains will undergo a charge shift in a very relevant pH window present in the extracellular milieu in most solid tumors (pH 5.6-7.2) after demasking by ROS. Doxorubicin (DOX)-loaded nanosized "AND gate" MR polymersomes (MRPs) are fabricated via microfluidic self-assembly. Chemical characterization reveals ROS-dependent pH sensitivity and accelerated DOX release under influence of both ROS and low pH. Treatment of tumor-bearing mice with DOX-loaded nonresponsive and "AND gate" MRPs dramatically decreases cardiac toxicity. The most optimal "AND gate" MRPs outperform free DOX in terms of tumor growth inhibition and survival, shedding light on chemical requirements for successful cancer nanomedicine.

Copper-coordination induced fabrication of stimuli-responsive polymersomes from amphiphilic block copolymer containing pendant thioethers

Cu²⁺-Containing hybrid polymersomes were fabricated via a co-assembly approach. The polymersomes exhibited stimuli-responsiveness to the competitive ligand and H₂O₂/GSH and mediated a Fenton-like reaction to produce ˙OH.

Design Strategies and Applications of ROS-Responsive Phenylborate Ester-Based Nanomedicine

Reactive oxygen species (ROS)-responsive nanomedicine has been extensively developed to improve the therapeutic effects while reducing the systemic toxicity. ROS, as important biological metabolites and signaling molecules, are known to overexpress in most of tumors and inflammations. Among various ROS-sensitive moieties, phenylborate ester (PBAE) with easy modifiable structure and excellent biocompatibility, represents one of the most ROS-sensitive structures. To harness it as a switch, the past several years had witnessed a booming of ROS-sensitive PBAE-based nanomedicine for various medical purposes. Much of the efforts were devoted to exploiting the potential in the management of antitumor and anti-inflammation. This review first summarizes the design strategies of PBAE in the construction of nanomedicine, with PBAE acting as not only the ROS-responsive unit, but also the roles of hydrophobic backbone or bridging segment in the macromolecular structures. The ROS-responsive mechanisms are then briefly discussed. Afterward, we focus on the introduction of the state-of-the-art research on ROS-responsive PBAE-based nanomedicine for antitumor and anti-inflammation applications. The conclusion and future perspectives of ROS-responsive nanomedicine are also provided.