Coordinating External and Built-In Triggers for Tunable Degradation of Polymeric Nanoparticles via Cycle Amplification

Efficient Encapsulation of β-Lapachone into Self-Immolative Polymer Nanoparticles for Cyclic Amplification of Intracellular Reactive Oxygen Species Stress

The selective upregulation of intracellular oxidative stress in cancer cells presents a promising approach for effective cancer treatment. In this study, we report the integration of enzyme catalytic amplification and chemical amplification reactions in β-lapachone (Lap)-loaded micellar nanoparticles (NPs), which are self-assembled from reactive oxygen species (ROS)-responsive self-immolative polymers (SIPs). This integration enables cyclic amplification of intracellular oxidative stress in cancer cells. Specifically, we have developed ROS-responsive SIPs with phenylboronic ester triggering motifs and hexafluoroisopropanol moieties in the side chains, significantly enhancing Lap loading efficiency (98%) and loading capacity (33%) through multiple noncovalent interactions. Upon ROS activation in tumor cells, the Lap-loaded micellar NPs disassemble, releasing Lap and generating additional ROS via enzyme catalytic amplification. This process elevates intracellular oxidative stress and triggers polymer depolymerization in a positive feedback loop. Furthermore, the degradation of SIPs via chemical amplification produces azaquinone methide intermediates, which consume intracellular thiol-related substrates, disrupt intracellular redox hemostasis, further intensify oxidative stress, and promote cancer cell apoptosis. This work introduces a strategy to enhance intracellular oxidative stress by combining enzymatic and chemical amplification reactions, providing a potential pathway for the development of highly efficient anticancer agents.

Self-immolative poly(thiocarbamate) with localized H2S signal amplification for precise cancer imaging and therapy

Hydrogen sulfide is essential in numerous physiological and pathological processes and has emerged as a promising cancer imaging and signaling molecule and a potentially versatile therapeutic agent. However, the endogenous levels of hydrogen sulfide remain insufficient to perform its biological functions, and thus, developing novel strategies that amplify hydrogen sulfide signals at lesion sites is of increasing interest. In this work, a nanoplatform (SNP) based on hydrogen sulfide-responsive self-immolative poly(thiocarbamate) with localized hydrogen sulfide signal amplification capability is developed to encapsulate a hydrogen sulfide-responsive fluorescent probe (e.g., hemicyanine dye; p-Cy) or an anticancer prodrug (e.g., doxorubicin; p-DOX) to form a nanoprobe (SNPp-Cy) or nanomedicine (SNPp-DOX) for cancer imaging and therapy, respectively. SNPp-Cy exhibits a low detection limit for hydrogen sulfide, enabling ultrasensitive detection of small (<2 mm) tumors in female mice. In addition, SNPp-DOX can effectively inhibit the growth of DOX-resistant human breast cancer xenograft, lung metastasis, and patient-derived xenograft tumors in female mice.

ROS-responsive hydrogels: from design and additive manufacturing to biomedical applications

Hydrogels with intricate 3D networks and high hydrophilicity have qualities resembling those of biological tissues, making them ideal candidates for use as smart biomedical materials. Reactive oxygen species (ROS) responsive hydrogels are an innovative class of smart hydrogels, and are cross-linked by ROS-responsive modules through covalent interactions, coordination interactions, or supramolecular interactions. Due to the introduction of ROS response modules, this class of hydrogels exhibits a sensitive response to the oxidative stress microenvironment existing in organisms. Simultaneously, due to the modularity of the ROS-responsive structure, ROS-responsive hydrogels can be manufactured on a large scale through additive manufacturing. This review will delve into the design, fabrication, and applications of ROS-responsive hydrogels. The main goal is to clarify the chemical principles that govern the response mechanism of these hydrogels, further providing new perspectives and methods for designing responsive hydrogel materials.

Sucrose-Powered Liposome Nanosensors for Urinary Glucometer-Based Monitoring of Cancer

Timely detection of early-stage cancer holds immense potential in enhancing prognostic outcomes. There is an increasing desire for versatile tools to enable simple, sensitive, and cost-effective cancer detection. By exploiting the extraintestinal metabolic inertness and efficiency renal clearance of sucrose, we designed a liposome nanosensor using sucrose as a messenger to convert tumor-specific esterase activity into glucose meter readout, enabling economical and sensitive urinalysis for cancer detection in point-of-care testing (POCT). Our results demonstrate that the nanosensors exhibited significant signal differences between tumor-bearing and healthy mice in both orthotopic and metastatic tumor models. Additionally, efficient elimination of the nanosensors through the hepatobiliary pathway was observed with no significant toxicity. Such a non-invasive diagnostic modality significantly assists in personalized pharmacological treatment and follow-up efficacy assessment. We envision that this modular liposome nanosensor platform might be applied for economically detecting diverse diseases via a simple urinary test.

Efficacy tumor therapeutic applications of stimuli-responsive block copolymer-based nano-assemblies

Block copolymers are composed of two or more blocks or segments with different chemical properties via various chemical bonds, which can assemble into nanoparticles with a "core-shell" structure. Due to the benefits of simple functionalization, superior drug-loading capacity, and good biocompatibility, various nano-assemblies based on block copolymers have become widely applied in the treatment of cancers in recent years. These nano-assemblies serve as carriers for anti-tumor bioactive, enhancing drug stability and prolonging their circulation time in vivo, which can reduce the toxic side effects of drugs and improve the therapeutic effect. However, the complex and heterogeneous tumor microenvironment poses challenges to the therapeutic efficacy of these nano-assemblies, having the result in the occurrence of drug resistance and the recurrence of tumors. Consequently, a diverse array of stimuli-responsive nano-assemblies has been devised in order to surmount these obstacles. This article provides a comprehensive overview of the utilization of stimuli-responsive nano-assemblies derived from block copolymers in the context of tumor treatment. The review summarizes block polymers responsive to internal stimuli (like ROS, redox, pH, and enzymes) and external stimuli (like light, and temperature), and discusses current challenges and prospects in this field, aiming to provide novel insights for clinical applications.

Introducing urea into tirapazamine derivatives to enhance anticancer therapy

Tirapazamine (TPZ) has been approved for multiple clinical trials relying on its excellent anticancer potential. However, as a typical hypoxia-activated prodrug (HAP), TPZ did not exhibit survival advantages in Phase III clinical trials when used in combination therapy due to the insufficient hypoxia levels in patients' tumors. In this study, to improve the therapeutic effects of TPZ, we first introduced urea to synthesize a series of urea-containing derivatives of TPZ. All urea-containing TPZ derivatives showed increased hypoxic cytotoxicity (9.51-30.85-fold) compared with TPZ, while maintaining hypoxic selectivity. TPZP, one of these derivatives, showed 20-fold higher cytotoxicity than TPZ while maintaining a similar hypoxic cytotoxicity ratio. To highly efficiently deliver TPZP to the tumors and reduce its side effects on healthy tissues, we further prepared TPZP into a nanodrug with fibrin-targeting ability: FT11-TPZP-NPs. CA4-NPs, a vascular disrupting agent, was used to increase the fibrin level within tumors and exacerbate tumor hypoxia. By being combined with CA4-NPs, FT11-TPZP-NPs can accumulate in the hypoxia-aggravated tumors and activate sufficiently to kill tumor cells. After a single-dose treatment, FT11-TPZP-NPs + CA4-NPs showed a high inhibition rate of 98.1% against CT26 tumor models with an initial volume of ∼480 mm3 and four out of six tumors were completely eliminated; it thereby exerted a significant antitumor effect. This study provides a new strategy for improving the therapeutic effect of TPZ and other HAPs in anticancer therapy.

Self-Assembly of Epitope-Tagged Proteins and Antibodies for Delivering Biologics to Antigen Presenting Cells

Inspired by the immune system's own strategy for macrophage activation, we describe here a simple self-assembly strategy for generating artificial immune complexes. The built-in recognition domains in the antibody, viz. the Fab and Fc domains, are judiciously leveraged for cargo conjugation to generate the nanoassembly and macrophage targeting, respectively. A responsive linker is engineered into the nanoassembly for releasing the protein cargo inside the macrophages, while ensuring stability during delivery. The design principles are simple and versatile to be applicable to a range of biologics, from small protein toxins to large enzymes, with high loading capacity. This self-assembly platform has the potential for delivering biologics to immune cells with implications in immunotherapy.

Structural Determinants of Stimuli-Responsiveness in Amphiphilic Macromolecular Nano-assemblies

Stimuli-responsive nano-assemblies from amphiphilic macromolecules could undergo controlled structural transformations and generate diverse macroscopic phenomenon under stimuli. Due to the controllable responsiveness, they have been applied for broad material and biomedical applications, such as biologics delivery, sensing, imaging, and catalysis. Understanding the mechanisms of the assembly-disassembly processes and structural determinants behind the responsive properties is fundamentally important for designing the next generation of nano-assemblies with programmable responsiveness. In this review, we focus on structural determinants of assemblies from amphiphilic macromolecules and their macromolecular level alterations under stimuli, such as the disruption of hydrophilic-lipophilic balance (HLB), depolymerization, decrosslinking, and changes of molecular packing in assemblies, which eventually lead to a series of macroscopic phenomenon for practical purposes. Applications of stimuli-responsive nano-assemblies in delivery, sensing and imaging were also summarized based on their structural features. We expect this review could provide readers an overview of the structural considerations in the design and applications of nanoassemblies and incentivize more explorations in stimuli-responsive soft matters.

Knowledge-Based Design of Multifunctional Polymeric Nanoparticles

Conventional drug delivery systems (DDS) today still face several drawbacks and obstacles. High total doses of active pharmaceutical ingredients (API) are often difficult or impossible to deliver due to poor solubility of the API or undesired clearance from the body caused by strong interactions with plasma proteins. In addition, high doses lead to a high overall body burden, in particular if they cannot be delivered specifically to the target site. Therefore, modern DDS must not only be able to deliver a dose into the body, but should also overcome the hurdles mentioned above as examples. One of these promising devices are polymeric nanoparticles, which can encapsulate a wide range of APIs despite having different physicochemical properties. Most importantly, polymeric nanoparticles are tunable to obtain tailored systems for each application. This can already be achieved via the starting material, the polymer, by incorporating, e.g., functional groups. This enables the particle properties to be influenced not only specifically in terms of their interactions with APIs, but also in terms of their general properties such as size, degradability, and surface properties. In particular, the combination of size, shape, and surface modification allows polymeric nanoparticles to be used not only as a simple drug delivery device, but also to achieve targeting. This chapter discusses to what extent polymers can be designed to form defined nanoparticles and how their properties affect their performance.

Visualizing Chain Growth of Polytelluoxane via Polymerization Induced Emission

Visualizing polymer chain growth is always a hot topic for tailoring structure-function properties in polymer chemistry. However, current characterization methods are limited in their ability to differentiate the degree of polymerization in real-time without isolating the samples from the reaction vessel, let alone to detect insoluble polymers. Herein, a reliable relationship is established between polymer chain growth and fluorescence properties through polymerization induced emission. (TPE-C2)2 -Te is used to realize in situ oxidative polymerization, leading to the aggregation of fluorophores. The relationship between polymerization degree of growing polytelluoxane (PTeO) and fluorescence intensity is constructed, enabling real-time monitoring of the polymerization reaction. More importantly, this novel method can be further applied to the observation of the polymerization process for growing insoluble polymer via surface polymerization. Therefore, the development of visualization technology will open a new avenue for visualizing polymer chain growth in real-time, regardless of polymer solubility.

Self-Amplified Cascade Degradation and Oxidative Stress Via Rational pH Regulation of Oxidation-Responsive Poly(ferrocene) Aggregates

Precise activation of polymer nanoparticles at lesion sites is crucial to achieve favorable therapeutic efficacy. However, conventional endogenous stimuli-responsive polymer nanoparticles probably suffer from few triggers to stimulate the polymer degradation and subsequent functions. Here, we describe oxidation-responsive poly(ferrocene) amphiphiles containing phenylboronic acid ester and ferrocene as the repeating backbone units. Upon triggering by hydrogen peroxide inside the tumor cells, the phenylboronic acid ester bonds are broken and poly(ferrocene) units are degraded to afford free ferrocene and noticeable hydroxide ions. The released hydroxide ions can immediately improve the pH value within the poly(ferrocene) aggregates, and the degradation rate of the phenylboronic acid ester backbone is further promoted by the upregulated pH; thereupon, the accelerated degradation can release much more additional hydroxide ions to improve the pH, thus achieving a positive self-amplified cascade degradation of poly(ferrocene) aggregates accompanied by oxidative stress boosting and efficient cargo release. Specifically, the poly(ferrocene) aggregates can be degraded up to ∼90% within 12 h when triggered by H2O2, while ferrocene-free control nanoparticles are degraded by only 30% within 12 days. In addition, the maleimide moieties tethered in the hydrophilic corona can capture blood albumin to form an albumin-rich protein corona and significantly improve favorable tumor accumulation. The current oxidation-responsive poly(ferrocene) amphiphiles can efficiently inhibit tumors in vitro and in vivo. This work provides a proof-of-concept paradigm for self-amplified polymer degradation and concurrent oxidative stress, which is promising in actively regulated precision medicine.

An endoplasmic reticulum-specific ratiometric fluorescent probe for imaging esterase in living cells

Esterase is primarily distributed in the endoplasmic reticulum (ER) and often overexpressed in cancer cells. Therefore, the detection of esterase in ER is significant for monitoring the metabolic process of various esters and evaluating the efficacy of chemotherapeutic prodrugs. However, only few fluorescent probes can detect esterase in the ER due to the lack of ER-specificity. More seriously, these probes are often limited by low pearson's colocalization coefficient and one single wavelength emission. To solve those problems, an ER-specific ratiometric fluorescent probe (ER-EST) is designed for detecting esterase in living cells. The ER-EST shows a ratiometric and red-shifted emission (125 nm) from 435 to 560 nm after hydrolysis by esterase. The fluorescence intensity ratio of ER-EST displays quantitative response to the esterase activity (0-0.5 U/mL) with low detection limit of 1.8 × 10^-4 U/mL. Importantly, the ER-EST with good biocompatibility and excellent ER-targeted ability was successfully employed to ratiometric image the endogenous endoplasmic reticulum esterase in living cells.

In situ albumin-binding and esterase-specifically cleaved BRD4-degrading PROTAC for targeted cancer therapy

Proteolysis-targeting chimeras (PROTACs) have recently been of great interest in cancer therapy. However, the bioavailability of PROTACs is considerably restricted due to their high hydrophobicity, poor cell permeability, and thereby low tumor targeting ability. Herein, esterase-cleavable maleimide linker (ECMal)-conjugated bromodomain 4 (BRD4)-degrading PROTAC (ECMal-PROTAC) is newly synthesized to exploit plasma albumin as an 'innate drug carrier' that can be accumulated in targeted tumor tissues. The BRD4-degrading ECMal-PROTAC is spontaneously bound to albumins via the thiol-maleimide click chemistry and its esterase-specific cleavage of ECMal-PROTAC is characterized in physiological conditions. The albumin-bound ECMal-PROTACs (Alb-ECMal-PROTACs) have an average size of 6.99 ± 1.38 nm, which is similar to that of free albumins without denaturation or aggregation. When Alb-ECMal-PROTACs are treated to 4T1 tumor cells, they are actively endocytosed and reach their highest intracellular level within 12 h. Furthermore, the maleimide linkers of Alb-ECMal-PROTACs are cleaved by the esterase to release free BRD-4 degrading PROTACs and the cell-internalized PROTACs successfully catalyze the selective degradation of BRD4 proteins, resulting in BRD4 deficiency-related apoptosis. When ECMal-PROTACs are intravenously injected into tumor-bearing mice, they exhibit a 16.3-fold higher tumor accumulation than free BRD4-PROTAC, due to the shuttling effect of albumin for tumor targeting. Finally, ECMal-PROTACs show 5.3-fold enhanced antitumor efficacy compared to free BRD4-PROTAC, without provoking any severe systemic toxicity. The expression of Bcl-2 and c-Myc, the downstream oncogenic proteins of BRD4, are also effectively suppressed. In summary, the in situ albumin binding of ECMal-PROTAC is proven as a promising strategy that effectively modulates its pharmacokinetics and therapeutic performance with high applicability to other types of PROTACs.

A Cascade BIME-Triggered Near-IR Cyanine Nanoplatform for Enhanced Antibacterial Photodynamic Therapy

The long-standing misuse of antibiotics has accelerated the emergence of drug-resistant bacteria, which gives rise to an urgent public health threat. Antibacterial photodynamic therapy (aPDT), as a burgeoning and promising antibacterial strategy, plays an essential role in avoiding the evolution of drug-resistant microbes. However, it is hard for conventional photosensitizers to achieve satisfactory antibacterial efficacy because of the complex bacterial infectious microenvironment (BIME). Herein, a cascade BIME-triggered near-infrared cyanine (HA-CY) nanoplatform has been developed via conjugating cyanine units to biocompatible hyaluronic acid (HA) for enhanced aPDT efficacy. The HA-CY nanoparticles can be dissociated under the overexpressed hyaluronidase in BIME to release a cyanine photosensitizer. Meanwhile, cyanine can be protonated under acidic BIME, where protonated cyanine can efficiently adhere to the surface of a negatively charged bacterial membrane and increase singlet oxygen production due to intramolecular charge transfer (ICT). Experiments in the cellular level and animal model proved that the BIME-triggered activation of aPDT could remarkably boost aPDT efficacy. Overall, this BIME-triggered HA-CY nanoplatform presents great promise for overcoming the dilemma of drug-resistant microbes.

A bio-orthogonally functionalized chitosan scaffold with esterase-activatable release for nerve regeneration

Developing nerve conduits with biological cues is a promising approach for repairing peripheral nerve injuries. Although most biological cues incorporated into conduits generally exert their biological functions at the surface, they could not be released into the on-demand regeneration sites under physiological conditions. Herein, we firstly report a bio-orthogonally functionalized chitosan scaffold with esterase-activatable release for peripheral nerve regeneration. In this study, biological cues are not only selectively conjugated into nerve conduits by bio-orthogonal reaction, but also precisely released in on-demand regeneration sites via esterase-activatable cleavage for peripheral nerve repair. Moreover, this nerve scaffold with esterase-activatable release could promote Schwann cells proliferation. In a rat sciatic nerve defect model, the bio-orthogonally functionalized scaffold with esterase-activatable release significantly increased sciatic nerve function recovery and improved target muscles weight. This strategy of incorporating esterase-activatable bioactive cues into peripheral nerve conduits offers great potential in preclinical studies.

Self-amplified chain-shattering cinnamaldehyde-based poly(thioacetal) boosts cancer chemo-immunotherapy

The selective activation of stimuli-responsive polymers in the tumor microenvironment is a great concern to achieve intelligent cancer therapy, but most of them show inadequate response due to insufficient endogenous triggering agents. Herein, we rationally designed a reactive oxygen species (ROS)-responsive cinnamaldehyde (CA)-based poly(thioacetal), consisting of ROS-responsive thioacetal (TA) and ROS-generating agent CA, with self-amplified chain-shattering polymer degradation. The mechanism of self-amplified chain-shattering is that endogenous ROS as a triggering agent facilitates chain cleavage of TA with the release of CA, which in turn produces more ROS through mitochondrial dysfunction, resulting in an exponential polymer degradation cascade. The polymer can be further modified with anticancer drug doxorubicin (DOX) for cooperative amplification of oxidative stress and immunogenic cell death (ICD) of tumor cells, thereby boosting the effect of chemo-immunotherapy. The self-amplified chain-shattering polymer designed in this work holds great promise in developing stimuli-responsive polymers for efficient drug delivery. STATEMENT OF SIGNIFICANCE: This study presented an approach to utilize self-amplified chain-shattering cinnamaldehyde-based poly (thioacetal) as a drug delivery system to restrain tumor growth and boost chemo-immunotherapy. The endogenous ROS as a triggering agent initiates the chain cleavage with the release of CA, which in turn produces ROS through mitochondria dysfunction, resulting in an exponential polymer degradation cascade and rapid drug release.

Self-immolative Amphiphilic Diblock Copolymers with Individually Triggerable Blocks

Self-immolative polymers are a growing class of degradable polymers that undergo end-to-end depolymerization after the stimuli-responsive cleavage of an end-cap or backbone unit. Their incorporation into amphiphilic block copolymers can lead to functions such as the disintegration of copolymer nanoassemblies when depolymerization is triggered. However, diblock copolymers have not yet been developed where both blocks are self-immolative. Described here is the synthesis, self-assembly, and triggered depolymerization of self-immolative block copolymers with individually triggerable hydrophilic and hydrophobic blocks. Neutral and cationic hydrophilic polyglyxoylamides (PGAm) with acid-responsive end caps were synthesized and coupled to an ultraviolet (UV) light-triggerable poly(ethyl glyoxylate) (PEtG) hydrophobic block. The resulting block copolymers self-assembled to form nanoparticles in aqueous solution, and their depolymerization in response to acid and UV light was studied by techniques including light scattering, NMR spectroscopy, and electron microscopy. Acid led to selective depolymerization of the PGAm blocks, leading to aggregation, while UV light led to selective depolymerization of the PEtG block, leading to disassembly. This self-immolative block copolymer system provides an enhanced level of control over smart copolymer assemblies and their degradation.

Cinnamaldehyde-based poly(thioacetal): A ROS-awakened self-amplifying degradable polymer for enhanced cancer immunotherapy

Although stimuli-responsive polymers have emerged as promising strategies for intelligent cancer therapy, limited polymer degradation and insufficient drug release remain a challenge. Here, we report a novel reactive oxygen species (ROS)-awakened self-amplifying degradable cinnamaldehyde (CA)-based poly(thioacetal) polymer. The polymer consists of ROS responsive thioacetal (TA) group and CA as the ROS generation agent. The self-amplified polymer degradation process is triggered by endogenous ROS-induced cleavage of the TA group to release CA. The CA released then promotes the generation of more ROS through mitochondrial dysfunction, resulting in amplified polymer degradation. More importantly, poly(thioacetal) itself can trigger immunogenic cell death (ICD) of the tumor cells and its side chains can be conjugated with indoleamine 2,3-dioxygenase 1 (IDO-1) inhibitor to reverse the immunosuppressive tumor microenvironment for synergistic cancer immunotherapy. The self-amplified degradable poly(thioacetal) developed in this work provides insights into the development of novel stimulus-responsive polymers for enhanced cancer immunotherapy.

Bioresponsive Polymers for Nanomedicine-Expectations and Reality!

Bioresponsive polymers in nanomedicine have been widely perceived to selectively activate the therapeutic function of nanomedicine at diseased or pathological sites, while sparing their healthy counterparts. This idea can be described as an advanced version of Paul Ehrlich's magic bullet concept. From that perspective, the inherent anomalies or malfunction of the pathological sites are generally targeted to allow the selective activation or sensory function of nanomedicine. Nonetheless, while the primary goals and expectations in developing bioresponsive polymers are to elicit exclusive selectivity of therapeutic action at diseased sites, this remains difficult to achieve in practice. Numerous research efforts have been undertaken, and are ongoing, to tackle this fine-tuning. This review provides a brief introduction to key stimuli with biological relevance commonly featured in the design of bioresponsive polymers, which serves as a platform for critical discussion, and identifies the gap between expectations and current reality.

Self-boosting stimulus activation of a polyprodrug with cascade amplification for enhanced antitumor efficacy

The use of polyprodrugs, which bind drugs to polymer chains through responsive linkers, is a potential technique for cancer therapy; however, a lack of endogenous triggering factors limits drug activation in tumor tissue. Herein, we rationally created a reactive oxygen species (ROS)-sensitive polyprodrug (TS_CA/DOX) with cascade amplification of triggering agents and drug activation by incorporating both an ROS signal amplifier (TA_CA) and a drug activation amplifier (SIP_DOX) into a delivery system. Endogenous ROS as a triggering mechanism kicked off the initial circulation phase to increase intracellular ROS signals. Subsequently, the enhanced ROS initiated the second degradation step, allowing the polyprodrug SIP_DOX to fracture spontaneously in a domino-like fashion, resulting in self-accelerated drug activation in tumor tissue. Therefore, the polyprodrug created in this study with cascade amplification of drug activation holds great promise for effective cancer treatment.

Self-catalyzed tumor ferroptosis based on ferrocene conjugated reactive oxygen species generation and a responsive polymer

In this work, we developed a ferroptosis self-catalyst, PTAF, exhibiting self-catalyzed ferroptosis for enhanced cancer therapy. Briefly, synergistic actions of self-catalyzed ˙OH accumulation and GPX4 indirect inactivation based on the establishment of the ROS self-catalytic loop effectively induced tumor ferroptosis, which provided a novel approach for enhanced tumor therapy.

Enzyme-responsive strategy as a prospective cue to construct intelligent biomaterials for disease diagnosis and therapy

Stimuli-responsive materials have been widely studied and applied in biomedical field. Under the stimulation of enzymes, the enzyme-responsive materials (ERMs) can be triggered to change their structures, properties and functions....

Recent advances in self-immolative linkers and their applications in polymeric reporting systems

Interest in self-immolative chemistry has grown over the past decade with more research groups harnessing the versatility to control the release of a compound from a larger chemical entity, given...

Self-Assembled Polymeric Materials: Design, Morphology, and Functional-Oriented Applications

This Review focuses on the current research advances of the synthesis of various amphiphilic block copolymers (ABCs), such as conventional ABCs and newly-presented polyprodrug amphiphiles (PPAs), and the development of corresponding self-assemblies in selective solvents driven by the intermolecular interactions, like noncovalent hydrophobic interactions, π-π interactions, and hydrogen bonds, between ABCs or preformed small polymeric nanoparticles. The design of these assemblies is systematically introduced, and the diverse examples concerning the unique assembly structures along with the fast development of their exclusive properties and various applications in different fields were discussed. Possible perspectives on the existential challenges and glorious future were elucidated finally. We hope this review will provide a convenient way for readers to motivate more evolutional innovative concepts and methods to design next generation of novel polymeric nanoassemblies, and fill the gap between material design and practical applications. This article is protected by copyright. All rights reserved.

Hydrogen Sulfide-Responsive Bicontinuous Nanospheres

Block copolymers (BCPs) that can self-assemble into particles and be triggered by disease-specific molecules such as hydrogen sulfide (H₂S) have the potential to impact on drug delivery, decreasing off-target toxicities while increasing drug efficacy. However, the incorporation of H₂S-responsive aryl azides into BCPs for self-assembly has been limited by heat, light, and radical sensitivities. In this study, a robust activator regenerated by the electron-transfer atom-transfer radical polymerization reaction was used to synthesize aryl-azide-containing BCPs under ambient conditions. Conditions controlling self-assembly of the BCPs into 150-200 nm particles and the physicochemical properties of the particles were investigated. The use of nanoprecipitation with tetrahydrofuran to promote self-assembly of the BCPs resulted in vesicle structures, while dimethylformamide or dimethylsulfoxide resulted in polymeric bicontinuous nanospheres (BCNs). Triggering of the BCPs and particles (vesicles or BCNs) via exposure to H₂S revealed that unsubstituted aryl azides were readily reduced (by HS^-), resulting in particle disruption or cross-linking. The relative polar nature of the particle bilayers containing unsubstituted aryl azides and the open structure of the BCNs did however limit encapsulation of small hydrophilic and hydrophobic payloads. Incorporation of a benzylamide substituent onto the aryl azide group increased the hydrophobicity of the particles and encapsulation of hydrophilic cargo but reduced sensitivity to H₂S, likely due to the reduced penetration of HS^- into the bilayer.

Designing self-propagating polymers with ultrasensitivity through feedback signal amplification

Stimuli-responsive polymers with self-propagating degradation capacity being sensitive to acids, bases, fluoride ions, and hydrogen peroxide are reviewed, exhibiting self-accelerated degradation behavior.