Conjugated‐Polyelectrolyte‐Based Polyprodrug: Targeted and Image‐Guided Photodynamic and Chemotherapy with On‐Demand Drug Release upon Irradiation with a Single Light Source

Monomer and Excimer Emission in a Conformational and Stacking-Adaptable Molecular System

A design strategy that combines molecular conformation, alkyl chain length, and charge-transfer effects has been developed to obtain conformational and stacking-adaptable donor-acceptor-π type molecules for precisely regulating the monomer and excimer emission in a single luminous platform under different environments. These fluorophores can exhibit bright monomer emissions when they are in the dispersed state based on their planar conformation. However, when the luminous molecules with short alkyl side chains are in the crystalline state, their molecular conformation can become distorted, further inducing strong intermolecular interactions and staggered π-π stacking for bright excimer emission. More importantly, their dispersed and aggregated states can be reversibly regulated in a phase-change fatty acid matrix, to achieve temperature-responsive fluorescence for temperature monitoring and advanced information encryption.

Programmable therapeutic nanoscale covalent organic framework for photodynamic therapy and hypoxia-activated cascade chemotherapy

Clinical photodynamic therapy (PDT) only has a limited cancer therapeutic effect and typically leads to a more hypoxic milieu owing to the hypoxic conditions of the solid tumor microenvironment that limit the singlet oxygen (¹O₂), generation. To address this issue, the PDT, in combination with hypoxia-activated prodrugs, has recently been investigated as a possible clinical treatment modality for cancer therapy. By cross-linking the photosensitizer tetra(4-hydroxyphenyl)porphine (THPP) and a ¹O₂-cleavable thioketal (TK) linker, a multifunctional nanoscale covalent organic framework (COF) platform with a high porphyrin loading capacity was synthesized, which significantly improve the reactive oxygen species (ROS) generation efficiency and contributes to PDT. As-synthesized THPP_TK-PEG nanoparticles (NPs) possess a high THPP photosensitizer content and mesoporous structure for further loading of the hypoxia-responsive prodrug banoxantrone (AQ4N) into the COF with a high-loading content. The nano-carriers surfaces are coated with a thick PEG coating to promote their dispersibility in physiological surroundings and therapeutic performance. When exposed to 660 nm radiation, such a nanoplatform can efficiently create cytotoxic ¹O₂ for PDT. Similarly, oxygen intake may exacerbate the hypoxic environment of the tumor, inducing the activation of AQ4N to achieve hypoxia-activated cascade chemotherapy and increased treatment efficacy. This study provides a new nanoplatform for photodynamic-chemical synergistic therapy and offers critical new insights for designing and developing a multifunctional supramolecular drug delivery system. STATEMENT OF SIGNIFICANCE: Here, we designed a laser-activated hypoxia-responsive nanoscale COF nanoplatform for hypoxia-activated cascade chemotherapy and PDT. When exposed to laser light, thus this nanoplatform can efficiently create cytotoxic ¹O₂ for PDT while consuming oxygen at the tumor location. However, increased oxygen consumption can exacerbate the tumor's hypoxic environment, causing AQ4N to become active, allowing for programmed hypoxia-triggered cascade chemotherapy and improved therapeutic efficacy. In addition, this innovative nanoscale COF nanoplatform allows for laser-controlled drug delivery in specific areas, which dramatically improves tumor inhibition. This research suggests a method for attaining ultrasensitive drug release and effective cascade therapy for cancer treatments.

A biotin-modified and H2O2-activatable theranostic nanoplatform for enhanced photothermal and chemical combination cancer therapy

Although synergistic effects of photothermal therapy (PTT) and chemotherapy for cancer have been extensively investigated in previous studies, more potential strategies need to be exploited to alleviate severe adverse effects. In this study, a biotin-modified and activatable nanotheranostic system is developed. This system (BPSP/DOX-CyBA) composed of H₂O₂-sensitive thioketal (TK) linker, hydrophilic biotin-decorated polyethylene glycol (PEG) segment, hydrophobic polycaprolactone (PCL) segment, could self-assemble into (99±1.3) nm nanoparticles and co-deliver H₂O₂-triggered photosensitizer CyBA and cytotoxic drugs DOX to tumor site. In vitro, DOX and CyBA could release rapidly from nanoparticles, CyBA accumulation in the mitochondria causes mitochondrial damage, leading to mitochondrial dysfunctions,while rising the level of ROS in B16F10 cells, and further to promote the micells to trigger release. CyBA could be activated into CyOH and the photothermal therapy was turn "off" into "on". In BPSP/DOX-CyBA group, the local temperature within tumor reached 50℃ and cell apoptosis rate reached 68.6% under Laser irradiation(650 nm, 1W/cm2). Fluorescence microscopy and flow cytometry analysis further demonstrated the better uptake efficiency on B16F10 cells with biotin decoration. In a mice B16F10 tumor model, the group with co-delivery CyBA and DOX had the best tumor retention effect, the maximal local temperature increasement and the minimum tumor growth with negligible side effects, suggesting the potential of BPSP/DOX-CyBA nanopalteform that synergistic photothermal therapy and chemotherapy and mitochondria damage as an effective melanoma treatment strategy.

A multifunctional platinum(IV) and cyanine dye-based polyprodrug for trimodal imaging-guided chemo-phototherapy

Imaging-guided chemo-phototherapy based on a single nanoplatform has a great significance to improve the efficiency of cancer therapy and diagnosis. However, high drug content, no burst release and real-time tracking of nanodrugs are the three main challenges for this kind of multifunctional nanotheranostics. In this work, we developed an innovative theranostic nanoplatform based on a Pt(IV) prodrug and a near-infrared (NIR) photosensitizer. A Pt(IV) prodrug and a cyanine dye (HOCyOH, Cy) were copolymerized and incorporated into the main chain of a polyprodrug (PCPP), which self-assembled into nanoparticles (NPs) with ∼27.61% Cy loading and ∼9.37% Pt loading, respectively. PCPP NPs enabled reduction-triggered backbone cleavage of polyprodrugs and bioactive Pt(II) release; Cy could be activated under 808 nm laser irradiation to produce local hyperthermia and reactive oxygen species (ROS) for phototherapy. Moreover, PCPP NPs with extremely high Cy and Pt heavy metal contents in the backbone of the polyprodrug could directly track the nanodrugs themselves via near-infrared fluorescence (NIRF) imaging, photothermal imaging, and computed tomography (CT) imaging in vitro and in vivo. As revealed by trimodal imaging, PCPP NPs were found to exhibit excellent tumor accumulation and antitumor efficiency after intravenous injection into H22-tumor-bearing mice. The dual-drug backboned polyprodrug nanoplatform exhibited great potential for bioimaging and combined chemo-phototherapy.

PEGylated Poly-HDACi: A Designer Polyprodrug from Optimized Drug Units

We designed, synthesized, and characterized a tri-block copolymer. Its hydrophobic part, a chain of histone deacetylase inhibitor (HDACi) prodrug, was symmetrically flanked by two identical PEG blocks, whereas the built-in HDACi was a linear molecule, terminated with a thiol at one end, and a hydroxyl group at the other. Such a feature facilitated end-to-end linkage of prodrugs through alternatively aligned disulfides and carbonates. The disulfides served dual roles: redox sensors of smart nanomedicine, and warheads of masked HDACi drugs. This approach, carefully designed to benefit both control-release and efficacy, is conceptually novel for optimizing drug units in nanomedicine. Micelles from this designer polyprodrug released only PEG, CO₂ and HDACi, and synergized with DOX against HCT116 cells, demonstrating its widespread potential in combination therapy. Our work highlights, for the first time, the unique advantage of thiol-based drug molecules in nanomedicine design.

Recent Advances in ROS-Sensitive Nano-Formulations for Atherosclerosis Applications

Over the past decade, ROS-sensitive formulations have been widely used in atherosclerosis applications such as ROS scavenging, drug delivery, gene delivery, and imaging. The intensified interest in ROS-sensitive formulations is attributed to their unique self-adaptive properties, involving the main molecular mechanisms of solubility switch and degradation under the pathological ROS differences in atherosclerosis. This review outlines the advances in the use of ROS-sensitive formulations in atherosclerosis applications during the past decade, especially highlighting the general design requirements in relation to biomedical functional performance.

Photodynamic-Chemodynamic Cascade Reactions for Efficient Drug Delivery and Enhanced Combination Therapy

Nanomedicines with photodynamic therapy and reactive oxygen species (ROS)-triggered drug release capabilities are promising for cancer therapy. However, most of the nanomedicines based on ROS-responsive nanocarriers still suffer from serious ROS consumption during the triggered drug release process. Herein, a photodynamic-chemodynamic cascade strategy for the design of drug delivery nanosystem is proposed. A doxorubicin hydrochloride-loaded ROS-responsive polymersome (DOX-RPS) is prepared via the self-assembly of amphiphilic poly(ethylene glycol)-poly(linoleic acid) and poly(ethylene glycol)-(2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-α)-iron chelate (PEG-HPPH-Fe). The RPS can effectively deliver a drug to tumor site through passive targeting effect. Upon laser irradiation, the photosensitizer HPPH can efficiently generate ROS, which further causes in situ oxidation of linoleic acid chain and subsequent RPS structural destruction, permitting triggered drug release. Intriguingly, catalyzed by HPPH-Fe, ROS will be regenerated from linoleic acid peroxide through a chemodynamic process. Therefore, ROS-triggered drug release can be achieved without ROS over-consumption. The in vitro and in vivo results confirmed ROS generation, triggered drug release behavior, and potent antitumor effect of the DOX-RPS. This photodynamic-chemodynamic cascade strategy provides a promising approach for enhanced combination therapy.

Organic Nanoparticles with Persistent Luminescence for In Vivo Afterglow Imaging-Guided Photodynamic Therapy

Optical imaging-guided photodynamic therapy (PDT), with precise localization and non-invasive treatment of tumors, is an emerging technique with great potential for cancer therapy. However, impaired by tissue auto-fluorescence that causes low signal-to-background ratio (SBR), most fluorescence imaging systems show poor sensitivity to tumors in vivo. In this study, we synthesized organic nanoparticles (ONPs) with persistent luminescence and good biocompatibility for afterglow imaging-guided PDT. The ONPs displayed near-infrared light emission with half-life time at minute level, which offered high SBR and good tissue penetration for in vivo afterglow tumor imaging. Taking advantage of their abundant singlet oxygen generation by NIR laser irradiation guided to the tumor sites, the ONPs also enabled imaging-guided PDT for efficient suppression of tumor growth in mice with minimal damage to major organs.

Photoacoustic Cavitation-Ignited Reactive Oxygen Species to Amplify Peroxynitrite Burst by Photosensitization-Free Polymeric Nanocapsules

Photoacoustic (PA) technology can transform light energy into acoustic wave, which can be used for either imaging or therapy that depends on the power density of pulsed laser. Here, we report photosensitizer-free polymeric nanocapsules loaded with nitric oxide (NO) donors, namely NO-NCPs, formulated from NIR light-absorbable amphiphilic polymers and a NO-releasing donor, DETA NONOate. Controlled NO release and nanocapsule dissociation are achieved in acidic lysosomes of cancer cells. More importantly, upon pulsed laser irradiation, the PA cavitation can excite water to generate significant reactive oxygen species (ROS) such as superoxide radical (O₂ ^.- ), which further spontaneously reacts with the in situ released NO to burst highly cytotoxic peroxynitrite (ONOO^- ) in cancer cells. The resultant ONOO^- generation greatly promotes mitochondrial damage and DNA fragmentation to initiate programmed cancer cell death. Apart from PA imaging, PA cavitation can intrinsically amplify reactive species via photosensitization-free materials for promising disease theranostics.

Enhanced Antitumor Efficacy by a Cascade of Reactive Oxygen Species Generation and Drug Release

Reactive oxygen species (ROS) can be used not only as a therapeutic agent for chemodynamic therapy (CDT), but also as a stimulus to activate release of antitumor drugs, achieving enhanced efficacy through the combination of CDT and chemotherapy. Here we report a pH/ROS dual-responsive nanomedicine consisting of β-lapachone (Lap), a pH-responsive polymer, and a ROS-responsive polyprodrug. In the intracellular acidic environment, the nanomedicine can realize pH-triggered disassembly. The released Lap can efficiently generate hydrogen peroxide, which will be further converted into highly toxic hydroxyl radicals via the Fenton reaction. Subsequently, through ROS-induced cleavage of thioketal linker, doxorubicin is released from the polyprodrug. In vivo results indicate that the cascade of ROS generation and antitumor-drug release can effectively inhibit tumor growth. This design of nanomedicine with cascade reactions offers a promising strategy to enhance antitumor efficacy.

Light-activatable dual prodrug polymer nanoparticle for precise synergistic chemotherapy guided by drug-mediated computed tomography imaging

The synergistic efficacy and clinical application of light-responsive polymeric co-delivery systems are severely restricted by uncontrollable/imprecise drug loading, release, and adverse effects caused by the introduction of additional light-responsive molecules or contrast agents when diagnostic imaging is applied to guide therapy. Here, we report the design of a light-activatable dual prodrug polymer nanoparticle (DPP NP) for precise synergistic chemotherapy guided by drug-mediated computed tomography (DMCT) imaging without the introduction of any additional diagnostic imaging agent. DPP NP enables visible light-triggered prodrug polymer backbone cleavage and bioactive Pt(II) release in cancer cell/tumor site; the light-cleaved polymer fragments are further hydrolyzed to produce demethyl cantharidin (DMC). Notably, the drug loading ratio of Pt(IV) and DMC in DPP NP was fixed at an optimal value to achieve maximum synergistic cancer cell killing, which was kept even after cellular uptake, thereby resulting in enhanced synergistic antitumor efficacy both in vitro and in vivo. Because of the high content of the heavy metal Pt in the polymer chain, the spatial/temporal dynamic biodistribution as well as metabolism of DPP NP in vivo can be monitored by Pt DMCT imaging to guide the light irradiation parameters for optimized light-activatable synergistic chemotherapy. Guided by Pt DMCT imaging, DPP NP was able to achieve an improved light-activatable antitumor efficacy, with 75% tumors fully cured and low toxicity. The light-activatable DDP NP system exhibits tremendous potential as precise theranostic nanomedicine. STATEMENT OF SIGNIFICANCE: The synergistic efficacy and clinical application of light-responsive polymeric co-delivery systems are severely restricted by uncontrollable/imprecise drug loading, delivery, and release, as well as adverse effects caused by the introduction of additional light-responsive molecules or contrast agents when diagnostic imaging is applied to guide therapy. Herein, we report the design of a light-activatable dual prodrug polymer nanoparticle (DPP NP) for precise synergistic chemotherapy guided by drug-mediated computed tomography imaging without the introduction of any additional diagnostic imaging agents. Notably, the drug loading ratio of Pt(II) and DMC in DPP NP was fixed at an optimal value to achieve maximum synergistic cancer cell killing, which was kept even after cellular uptake, thereby resulting in enhanced synergistic antitumor efficacy both in vitro and in vivo. The light-activatable DDP NP system exhibits tremendous potential as precise theranostic nanomedicine.

Light-Activatable Prodrug and AIEgen Copolymer Nanoparticle for Dual-Drug Monitoring and Combination Therapy

Polyprodrug nanoparticles have been employed recently for safer and more effective cancer treatment. However, it remains a challenge to elucidate how and when the polyprodrug nanoparticles are dissociated and activated to release active drugs in cancer cells. Herein, a visible light-activatable Pt(IV) prodrug and an aggregation-induced emission luminogen (AIEgen) were copolymerized and embedded in the main chain of PtAIECP, and the chemotherapeutic doxorubicin (DOX) was subsequently encapsulated in the nanoparticles self-assembled by PtAIECP (PtAIECP@DOX NP). PtAIECP@DOX NP enabled the monitoring of both the light-activation of Pt(IV) prodrug to active Pt(II) and release of encapsulated DOX intracellularly through the fluorescence "turn-on" in the course of visible-light-induced polymer-main-chain cleavage and self-assembled structure dissociation in vitro and ex vivo. The synergistic anticancer efficacy of the activated Pt(II) drug and DOX in PtAIECP@DOX NP was also investigated in vitro and in vivo. The implementation of polyprodrug and AIE combination strategy empowered dual drug release and monitoring, which could be further used to guide the temporal and spatial control of light irradiation to maximize therapeutic efficiency, and will inspire other combinational bioimaging and therapy strategies.

Cancer-specific chemotherapeutic strategy based on the vitamin K3 mediated ROS regenerative feedback and visualized drug release in vivo

A promising theranostic nanosystem VK3-CPT@Ru-CD is designed and fabricated by the host-guest driven self-assembly between the fluorescent adamantine-functionalized Ru(II) complexes and the ROS-labile-cyclodextrin modified thioketal linkers, in which anticancer drug camptothecin (CPT) and vitamin K3 (VK3) are effectively co-encapsulated. On account of the generative feedback between the intracellular redox cycling of VK3 and the high degree of ROS-triggered collapse of nanoparticles, VK3-CPT@Ru-CD can facilitate cancer-specific ROS amplification and drug release selectively in cancer cells, thus realizing the selective killing of tumor with minimal side-effects both in vitro and in vivo, the therapeutic effect of which is more prominent than the free anti-cancer drugs. More interestingly, the menadione structure of encapsulated VK3 can effectively quench the inherent fluorescence of Ru-CD, and a fluorescence lightening up phenomenon is observed accompanied with the ROS-triggered drug release, which can be utilized for real-time tracking of drug release in vitro and in vivo.

Anaerobe-Inspired Anticancer Nanovesicles

Anaerobic bacteria, such as Clostridium and Salmonella, can selectively invade and colonize in tumor hypoxic regions (THRs) and deliver therapeutic products to destroy cancer cells. Herein, we present an anaerobe nanovesicle mimic that can not only be activated in THRs but also induce hypoxia in tumors by themselves. Moreover, inspired by the oxygen metabolism of anaerobes, we construct a light-induced hypoxia-responsive modality to promote dissociation of vehicles and activation of bioreductive prodrugs simultaneously. In vitro and in vivo experiments indicate that this anaerobe-inspired nanovesicle can efficiently induce apoptotic cell death and significantly inhibit tumor growth. Our work provides a new strategy for engineering stimuli-responsive drug delivery systems in a bioinspired and synergistic fashion.

ROS-responsive drug delivery systems

Reactive oxygen species (ROS) play an important role in signal transduction and metabolism. Over-produced ROS in cells or tissues, however, often leads to oxidation stress that has implications in a series of diseases including cancer, aging, atherosclerosis and inflammation. Driven by the need for on-demand drug delivery and fuelled by recent development of ROS-responsive materials and nanomedicine, responsive drug delivery systems (DDSs) have gained increasing research interest. ROS-responsive DDS is designed to release therapeutic agents only in targets of interest that produce excessive ROS, which may lead to both enhanced therapeutic efficiency and reduced side effects. Multiple-stimuli responsive DDSs that are also sensitive to other stimuli can further enhance controlled drug release in sites where multiple stimuli coexist. Beyond drug delivery, multifunctional DDSs have great potential in achieving simultaneous imaging, combinatorial therapy and targeting ability by introducing multifunctional elements such as signal reporter, targeting elements and photosensitizer. This review will summarize the latest development of ROS-responsive DDSs and discuss their design principle and biomedical applications.

Nanocomposite-Based Photodynamic Therapy Strategies for Deep Tumor Treatment

Photodynamic therapy (PDT), as an emerging clinically approved modality, has been used for treatment of various cancer diseases. Conventional PDT strategies are mainly focused on superficial lesions because the wavelength of illumination light of most clinically approved photosensitizers (PSs) is located in the UV/VIS range that possesses limited tissue penetration ability, leading to ineffective therapeutic response for deep-seated tumors. The combination of PDT and nanotechnology is becoming a promising approach to fight against deep tumors. Here, the rapid development of new PDT modalities based on various smartly designed nanocomposites integrating with conventionally used PSs for deep tumor treatments is introduced. Until now many types of multifunctional nanoparticles have been studied, and according to the source of excitation energy they can be classified into three major groups: near infrared (NIR) light excited nanomaterials, X-ray excited scintillating/afterglow nanoparticles, and internal light emission excited nanocarriers. The in vitro and in vivo applications of these newly developed PDT modalities are further summarized here, which highlights their potential use as promising nano-agents for deep tumor therapy.

Tumor targeted gold nanoparticles for FRET-based tumor imaging and light responsive on-demand drug release

Multifunctional AuNPs for MMP-2 responsive tumor imaging and on-demand drug release were designed. A good chemotherapy and photodynamic therapy combination with minimized side effects was realized.

Reactive oxygen species (ROS) responsive PEG–PCL nanoparticles with pH-controlled negative-to-positive charge reversal for intracellular delivery of doxorubicin

The charge-conversional behavior and ROS-sensitivity of mPEG-ros-P(CL-co-DCL) NPs for active loading and triggered release of DOX.