ROS‐Responsive Camptothecin Prodrug Nanoparticles for On‐Demand Drug Release and Combination of Chemotherapy and Photodynamic Therapy

Glutathione-depleting polyprodrug nanoparticle for enhanced photodynamic therapy and cascaded locoregional chemotherapy

Nanomedicines that combine reactive oxygen species (ROS)-responsive polyprodrug and photodynamic therapy have shown great potential for improving treatment efficacy. However, the consumption of ROS by overexpressed glutathione in tumor cells is a major obstacle for achieving effective ROS amplification and prodrug activation. Herein, we report a polyprodrug-based nanoparticle that can realize ROS amplification and cascaded drug release. The nanoparticle can respond to the high level of hydrogen peroxide in tumor microenvironment, achieving self-destruction and release of quinone methide. The quinone methide depletes intracellular glutathione and thus decreases the antioxidant capacity of cancer cells. Under laser irradiation, a large amount of ROS will be generated to induce cell damage and prodrug activation. Therefore, the glutathione-depleting polyprodrug nanoparticles can efficiently inhibit tumor growth by enhanced photodynamic therapy and cascaded locoregional chemotherapy.

Thermoresponsive and Substrate Self-Cycling Nanoenzyme System for Efficient Tumor Therapy

Cerium oxide (CeO2-x) performs well in photothermal and catalytic properties due to its abundance of oxygen vacancies. Based on this, we designed a thermosensitive therapeutic nanoplatform to achieve continuous circular drug release in tumor. It can solve the limitation caused by insufficient substrate in the process of tumor treatment. Briefly, CeO2-x and camptothecin (CPT) were wrapped in an agarose hydrogel, which could be melted by the photothermal effect of CeO2-x. At the same time, the local temperature increase provided photothermal treatment, which could induce the apoptosis of tumor cell. After that, CPT was released to damage the DNA in tumor cells to realize chemical treatment. In addition, CPT could active nicotinamide adenine dinucleotide oxidase to react with O2 to increase the intracellular H2O2. After that, the exposed CeO2-x could catalyze H2O2 to generate cytotoxic reactive oxygen species for chemodynamic therapy. More importantly, CeO2-x could catalyze H2O2 to produce O2, which could combine with the catalytic action of CPT to construct a substrate self-cycling nanoenzyme system. Overall, this self-cycling nanoplatform released hypoxia in the tumor microenvironment and built a multimode tumor treatment, which achieved an ideal antitumor affect.

Hierarchical self-recognition and response in CSC and non-CSC micro-niches for cancer therapy

Cancer stem cells (CSCs) characterized by self-renewal, invasiveness, tumorigenicity and resistance to treatment are regarded as the thorniest issues in refractory tumors. We develop a targeted and hierarchical controlled release nano-therapeutic platform (SEED-NPs) that self-identifies and responds to CSC and non-CSC micro-niches of tumors. In non-CSC micro-niche, reactive oxygen species (ROS) trigger the burst release of the chemotherapeutic drug and photosensitizer to kill tumor cells and reduce tumor volume by combining chemotherapy and photodynamic therapy (PDT). In CSC micro-niche, the preferentially released differentiation drug induces CSC differentiation and transforms CSCs into chemotherapy-sensitive cells. SEED-NPs exhibit an extraordinary capacity for downregulating the stemness of CD44+/CD24- SP (side population) cell population both in vitro and in vivo, and reveal a 4-fold increase of tumor-targeted accumulation. Also, PDT-generated ROS promote the formation of tunneling nanotubes and facilitate the divergent network transport of drugs in deep tumors. Moreover, ROS in turn promotes CSC differentiation and drug release. This positive-feedback-loop strategy enhances the elimination of refractory CSCs. As a result, SEED-NPs achieve excellent therapeutic effects in both 4T1 SP tumor-bearing mice and regular 4T1 tumor-bearing mice without obvious toxicities and eradicate half of mice tumors. SEED-NPs integrate differentiation, chemotherapy and PDT, which proved feasible and valuable, indicating that active targeting and hierarchical release are necessary to enhance antitumor efficacy. These findings provide promising prospects for overcoming barriers in the treatment of CSCs.

Recent Progress in Implantable Drug Delivery Systems

In recent years, tremendous effort is devoted to developing platforms, such as implantable drug delivery systems (IDDSs), with temporally and spatially controlled drug release capabilities and improved adherence. IDDSs have multiple advantages: i) the timing and location of drug delivery can be controlled by patients using specific stimuli (light, sound, electricity, magnetism, etc.). Some intelligent "closed-loop" IDDS can even realize self-management without human participation. ii) IDDSs enable continuous and stable delivery of drugs over a long period (months to years) and iii) to administer drugs directly to the lesion, thereby helping reduce dosage and side effects. iv) IDDSs enable personalized drug delivery according to patient needs. The high demand for such systems has prompted scientists to make efforts to develop intelligent IDDS. In this review, several common stimulus-responsive mechanisms including endogenous (e.g., pH, reactive oxygen species, proteins, etc.) and exogenous stimuli (e.g., light, sound, electricity, magnetism, etc.), are given in detail. Besides, several types of IDDS reported in recent years are reviewed, including various stimulus-responsive systems based on the above mechanisms, radio frequency-controlled IDDS, "closed-loop" IDDS, self-powered IDDS, etc. Finally, the advantages and disadvantages of various IDDS, bottleneck problems, and possible solutions are analyzed to provide directions for subsequent research.

ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.

Engineering H2O2 Self-Supplying Platform for Xdynamic Therapies via Ru-Cu Peroxide Nanocarrier: Tumor Microenvironment-Mediated Synergistic Therapy

Of the most common, hypoxia, overexpressed glutathione (GSH), and insufficient H2O2 concentration in the tumor microenvironment (TME) are the main barriers to the advancment of reactive oxygen species (ROS) mediated Xdynamic therapies (X = photo, chemodynamic, chemo). Maximizing Fenton catalytic efficiency is crucial in chemodynamic therapy (CDT), yet endogenous H2O2 levels are not sufficient to attain better anticancer efficacy. Specifically, there is a need to amplify Fenton reactivity within tumors, leveraging the unique attributes of the TME. Herein, for the first time, we design RuxCu1-xO2-Ce6/CPT (RCpCCPT) anticancer nanoagent for TME-mediated synergistic therapy based on heterogeneous Ru-Cu peroxide nanodots (RuxCu1-xO2 NDs) and chlorine e6 (Ce6), loaded with ROS-responsive thioketal (TK) linked-camptothecin (CPT). The Ru-Cu peroxide NDs (RCp NDs, x = 0.50) possess the highest oxygen vacancy (OV) density, which grants them the potential to form massive Lewis's acid sites for peroxide adsorption, while the dispersibility and targetability of the NDs were improved via surface modification using hyaluronic acid (HA). In TME, RCpCCPT degrades, releasing H2O2, Ru2+/3+, and Cu+/2+ ions, which cooperatively facilitate hydroxyl radical (•OH) formation and deactivate antioxidant GSH enzymes through a cocatalytic loop, resulting in excellent tumor therapeutic efficacy. Furthermore, when combined with laser treatment, RCpCCPT produces singlet oxygen (1O2) for PDT, which induces cell apoptosis at tumor sites. Following ROS generation, the TK linkage is disrupted, releasing up to 92% of the CPT within 48 h. In vitro investigations showed that laser-treated RCpCCPT caused 81.5% cell death from PDT/CDT and chemotherapy (CT). RCpCCPT in cancer cells produces red-blue emission in images of cells taking them in, which allows for fluorescence image-guided Xdynamic treatment. The overall results show that RCp NDs and RCpCCPT are more biocompatible and have excellent Xdynamic therapeutic effectiveness in vitro and in vivo.

Highly Effective Pyroelectric Catalysis for Simultaneous Tumor-Targeted Dynamic Therapy and Gentle Photothermal Therapy by Oxygen-Vacancy-Rich CeO2-BaTiO3 Nanorods

Pyroelectric nanostructures can effectively generate temperature-mediated reactive oxygen species (ROS) through the pyroelectric effect, providing promise for treating hypoxic tumors; and therefore, the synergistic application of photothermal therapy (PTT) and pyroelectric dynamic therapy (PEDT) presents an intriguing approach for cancer therapy. However, this method still faces challenges in improving pyroelectric catalysis and achieving precise tumor localization. In this study, a nano-heterojunction based on CeO2-BaTiO3 nanorods (IR1061@PCBNR) is reported, which exhibits highly effective pyroelectric catalysis for simultaneous tumor-targeted dynamic therapy and gentle photothermal therapy through the utilization of the rich oxygen vacancies. The oxygen vacancies create active sites that facilitate the migration of pyroelectrically-induced charge carriers, improving charge separation and ROS generation. IR1061@PCBNR also demonstrates high tumor penetration; while, minimizing damage to normal cells. This precise nanomedicine strategy holds great potential for advancing dynamic cancer therapies by overcoming the limitations of conventional approaches.

A concept of dual-responsive prodrugs based on oligomerization-controlled reactivity of ester groups: an improvement of cancer cells versus neutrophils selectivity of camptothecin

Many known chemotherapeutic anticancer agents exhibit neutropenia as a dose-limiting side effect. In this paper we suggest a prodrug concept solving this problem for camptothecin (HO-cpt). The prodrug is programmed according to Boolean "AND" logic. In the absence of H2O2 (trigger T1), e.g. in the majority of normal cells, it exists as an inactive oligomer. In cancer cells and in primed neutrophils (high H2O2), the oligomer is disrupted forming intermediate (inactive) lipophilic cationic species. These are accumulated in mitochondria (Mit) of cancer cells, where they are activated by hydrolysis at mitochondrial pH 8 (trigger T2) with formation of camptothecin. In contrast, the intermediates remain stable in neutrophils lacking Mit and therefore a source of T2. In this paper we demonstrated a proof-of-concept. Our prodrug exhibits antitumor activity both in vitro and in vivo, but is not toxic to normal cell and neutrophils in contrast to known single trigger prodrugs and the parent drug HO-cpt.

Nanocarriers address intracellular barriers for efficient drug delivery, overcoming drug resistance, subcellular targeting and controlled release

The cellular barriers are major bottlenecks for bioactive compounds entering into cells to accomplish their biological functions, which limits their biomedical applications. Nanocarriers have demonstrated high potential and benefits for encapsulating bioactive compounds and efficiently delivering them into target cells by overcoming a cascade of intracellular barriers to achieve desirable therapeutic and diagnostic effects. In this review, we introduce the cellular barriers ahead of drug delivery and nanocarriers, as well as summarize recent advances and strategies of nanocarriers for increasing internalization with cells, promoting intracellular trafficking, overcoming drug resistance, targeting subcellular locations and controlled drug release. Lastly, the future perspectives of nanocarriers for intracellular drug delivery are discussed, which mainly focus on potential challenges and future directions. Our review presents an overview of intracellular drug delivery by nanocarriers, which may encourage the future development of nanocarriers for efficient and precision drug delivery into a wide range of cells and subcellular targets.

Emerging non-antibody‒drug conjugates (non-ADCs) therapeutics of toxins for cancer treatment

The non-selective cytotoxicity of toxins limits the clinical relevance of the toxins. In recent years, toxins have been widely used as warheads for antibody‒drug conjugates (ADCs) due to their efficient killing activity against various cancer cells. Although ADCs confer certain targeting properties to the toxins, low drug loading capacity, possible immunogenicity, and other drawbacks also limit the potential application of ADCs. Recently, non-ADC delivery strategies for toxins have been extensively investigated. To further understand the application of toxins in anti-tumor, this paper provided an overview of prodrugs, nanodrug delivery systems, and biomimetic drug delivery systems. In addition, toxins and their combination strategies with other therapies were discussed. Finally, the prospect and challenge of toxins in cancer treatment were also summarized.

Optimized silicate nanozymes with atomically incorporated iron and manganese for intratumoral coordination-enhanced once-for-all catalytic therapy

Although plant-derived cancer therapeutic products possess great promise in clinical translations, they still suffer from quick degradation and low targeting rates. Herein, based on the oxygen vacancy (OV)-immobilization strategy, an OV-enriched biodegradable silicate nanoplatform with atomically dispersed Fe/Mn active species and polyethylene glycol modification was innovated for loading gallic acid (GA) (noted as FMMPG) for intratumoral coordination-enhanced multicatalytic cancer therapy. The OV-enriched FMMPG nanozymes with a narrow band gap (1.74 eV) can be excited by a 650 nm laser to generate reactive oxygen species. Benefiting from the Mn-O bond in response to the tumor microenvironment (TME), the silicate skeleton in FMMPG collapses and completely degrades after 24 h. The degraded metal M (M = Fe, Mn) ions and released GA can in situ produce a stable M-GA nanocomplex at tumor sites. Importantly, the formed M-GA with strong reductive ability can transform H2O2 into the fatal hydroxyl radical, causing serious oxidative damage to the tumor. The released Fe3+ and Mn2+ can serve as enhanced contrast agents for magnetic resonance imaging, which can track the chemodynamic and photodynamic therapy processes. The work offers a reasonable strategy for a TME-responsive degradation and intratumoral coordination-enhanced multicatalytic therapy founded on bimetallic silicate nanozymes to achieve desirable tumor theranostic outcomes.

Hypoxia-Responsive Tetrameric Supramolecular Polypeptide Nanoprodrugs for Combination Therapy

Despite the intense progress of photodynamic and chemotherapy, however, they cannot prevent solid tumor invasion, metastasis, and relapse, along with inferior efficacy and severe side effects. The hypoxia-responsive nanoprodrugs integrating photodynamic functions are highly sought to address the above-mentioned problems and overcome the tumor hypoxia-reduced efficacy. Herein, a hypoxia-responsive tetrameric supramolecular polypeptide nanoprodrug (SPN-TAPP-PCB4) is constructed from the self-assembly of tetrameric porphyrin-central poly(l-lysine-azobenzene-chlorambucil) (TAPP-(PLL-Azo-CB)4) and an anionic water-soluble [2]biphenyl-extended-pillar[6]arene (AWBpP6) via the synergy of hydrophobic, π-π stacking, and host-guest interactions. Upon laser irradiation, the central TAPP can convert oxygen to generate single oxygen (1 O2 ) to kill tumor cells. Furthermore, under the acidic and PDT-aggravated hypoxia tumor cell microenvironment, SPN-TAPP-PCB4 is rapidly disassembled, and then efficiently releases activated CB through the hypoxic-responsive cleavage of azobenzene linkages. Both in vitro and in vivo biological studies showcase synergistic cancer-killing actions between photodynamic therapy (PDT) and chemotherapy (CT) with negligible toxicity. Consequently, this supramolecular polypeptide nanoprodrug offers an effective strategy to design a hypoxia-responsive nanoprodrug for a potential combo PDT-CT transition.

Combining photodynamic therapy and cascade chemotherapy for enhanced tumor cytotoxicity: the role of CTT2P@B nanoparticles

The mitochondria act as the main producers of reactive oxygen species (ROS) within cells. Elevated levels of ROS can activate the mitochondrial apoptotic pathway, leading to cell apoptosis. In this study, we devised a molecular prodrug named CTT2P, demonstrating notable efficacy in facilitating mitochondrial apoptosis. To develop nanomedicine, we enveloped CTT2P within bovine serum albumin (BSA), resulting in the formulation known as CTT2P@B. The molecular prodrug CTT2P is achieved by covalently conjugating mitochondrial targeting triphenylphosphine (PPh3), photosensitizer TPPOH2, ROS-sensitive thioketal (TK), and chemotherapeutic drug camptothecin (CPT). The prodrug, which is chemically bonded, prevents the escape of drugs while they circulate throughout the body, guaranteeing the coordinated dispersion of both medications inside the organism. Additionally, the concurrent integration of targeted photodynamic therapy and cascade chemotherapy synergistically enhances the therapeutic efficacy of pharmaceutical agents. Experimental results indicated that the covalently attached prodrug significantly mitigated CPT cytotoxicity under dark conditions. In contrast, TPPOH2, CTT2, CTT2P, and CTT2P@B nanoparticles exhibited increasing tumor cell-killing effects and suppressed tumor growth when exposed to light at 660 nm with an intensity of 280 mW cm-2. Consequently, this laser-triggered, mitochondria-targeted, combined photodynamic therapy and chemotherapy nano drug delivery system, adept at efficiently promoting mitochondrial apoptosis, presents a promising and innovative approach to cancer treatment.

Ferroptosis boosted oral cancer photodynamic therapy by carrier-free Sorafenib-Ce6 self-assembly nanoparticles

Oral cancer is a disease with high morbidity and mortality worldwide and greatly impacts the quality of life, especially in patients with advanced stages. Photodynamic therapy (PDT) is one of the most effective clinical treatments for oral cancers. However, most clinically applied photosensitizers have several deficiencies, including oxygen dependence, poor aqueous solubility, and a lack of tumor-targeting ability. Herein, the carrier-free multifunctional Sorafenib (Sor), chlorin e6 (Ce6), and Fe3+ self-assembly co-delivery nanoparticles (Sor-Ce6 NPs) were constructed via combining a ferroptosis inducer Sor and a photosensitizer Ce6 for synergetic therapy. The as-synthesized Sor-Ce6 NPs presented excellent colloidal stability and water dispersity with good in vivo tumor-targeting ability. More significantly, the low dose of Sor-Ce6 NPs had little dark toxicity but produced significantly enhanced ROS and supplied O2 sustainably to increase phototoxicity through ferroptosis pathway. Notably, the Sor-Ce6 NPs showed significantly higher in vitro and in vivo anti-tumor efficacy than the Sor/Ce6 mixture due to the improvement of cellular uptake and the incorporation of foreign Fe ions in the system, which also confer the T1 magnetic resonance-guided imaging ability to the formed Sor-Ce6 NPs. Our study demonstrates a promising self-assembled strategy for overcoming hypoxia-related PDT resistance for oral cancer treatment.

Novel GSH-responsive prodrugs derived from indole-chalcone and camptothecin trigger apoptosis and autophagy in colon cancer

Antineoplastic agents that target tubulin have shown efficacy as chemotherapeutic drugs, yet they are often constrained by multidrug resistance (MDR) and unwanted side effects. A multi-targeted strategy demonstrates great potency in reducing toxicity and enhancing efficacy and provides an alternative way for attenuating MDR. In this study, a series of dual-targeted anti-cancer agents based on indole-chalcone derivatives and the camptothecin (CPT) scaffold were synthesized. Among them, 14-1 demonstrated superior anti-proliferative activity than its precursor 13-1, CPT or their physical mixtures against tested cancer cells, including multidrug-resistant variants, while exhibited moderate cytotoxicity toward human normal cells. Mechanistic studies revealed that 14-1 acted as a glutathione-responsive prodrug, inducing apoptosis by substantially enhancing intracellular uptake of CPT, inhibiting tubulin polymerization, increasing the accumulation of intracellular reactive oxygen species, and initiating a mitochondrion-dependent apoptotic pathway. Moreover, 14-1 notably induced autophagy and suppressed topoisomerase I activity to further promote apoptosis. Importantly, 14-1 displayed potent inhibitory effect on tumor growth in paclitaxel (PTX)-resistant colorectal cancer (HCT-116/PTX) xenograft models without inducing obvious toxicity compared with CPT- or combo-treated group. These results suggest that 14-1 holds promise as a novel candidate for anti-cancer therapy, particularly in PTX-resistant cancers.

A dual action coumarin-camptothecin polymer for light responsive drug release and photodynamic therapy

A light-responsive polymer allowing the controlled release of camptothecin and the generation of reactive oxygen species (ROS) is reported. The polymer was prepared by controlled copolymerisation of water-soluble N,N-dimethyl acrylamide with a bromocoumarin methacrylate monomer. The lipophilic chemotherapy agent camptothecin was caged onto the coumarin unit via a photo-cleavable carbonate ester enabling light-triggered cargo release. The polymer showed good biocompatibility in the dark, and high cancer cell killing activity mediated both by the photo-release of camptothecin and ROS generation.

Multimodal Nanoplatform with ROS Amplification to Overcome Multidrug Resistance in Prostate Cancer via Targeting P-Glycoprotein and Ferroptosis

Chemotherapy remains the most essential treatment for prostate cancer, but multidrug resistance (MDR) contributes to chemotherapy failure and tumor-related deaths. The overexpression of P-glycoprotein (P-gp) is one of the main mechanisms behind MDR. Here, this work reports a multimodal nanoplatform with a reactive oxygen species (ROS) cascade for gas therapy/ferroptosis/chemotherapy in reversing MDR. The nanoplatform disassembles when responding to intracellular ROS and exerts three main functions: First, nitric oxide (NO) targeted delivery can reverse MDR by downregulating P-gp expression and inhibiting mitochondrial function. Second, ferrocene-induced ferroptosis breaks the redox balance in the tumor intracellular microenvironment and synergistically acts against the tumor. Third, the release of paclitaxel (PTX) is precisely controlled in situ in the tumor for chemotherapy that avoids damage to normal tissues. Excitingly, this multimodal nanoplatform is a promising weapon for reversing MDR and may provide a pioneering paradigm for synergetic cancer therapy.

Preclinical Assessment of Enhanced Chemodynamic Therapy by an FeMnOx-Based Nanocarrier: Tumor-Microenvironment-Mediated Fenton Reaction and ROS-Induced Chemotherapeutic for Boosted Antitumor Activity

In recent studies, iron-containing Fenton nanocatalysts have demonstrated significant promise for clinical use due to their effective antitumor activity and low cytotoxicity. A new approach was reported in this work utilizing cation exchange synthesis to fabricate FeMnOx nanoparticles (NPs) that boost Fenton reactions and responses to the tumor microenvironment (TME) for chemodynamic therapy (CDT) and chemotherapy (CT). Within the TME, the redox metal pair of Fe2+/Mn2+ helps break down endogenous hydrogen peroxide (H2O2) into very harmful hydroxyl radicals (•OH) while simultaneously deactivating glutathione (GSH) to boost CDT performance. To further enhance the therapeutic potential, FeMnOx NPs were encapsulated with thioketal-linked camptothecin (CPT-TK-COOH), a reactive oxygen species (ROS)-responsive prodrug, achieving a high CPT-loading capacity of up to 51.1%. Upon ROS generation through the Fenton reaction, the prodrug TK linkage was disrupted, releasing 80% of the CPT payload within 48 h. Notably, FeMnOx@CPT exhibited excellent dual-modal imaging capabilities, enabling magnetic resonance and fluorescence imaging for image-guided therapy. In vitro studies showed the cytocompatibility of FeMnOx NPs using MDA-Mb-231 and 4T1 cells, but in the presence of H2O2, they induced significant cytotoxicity, resulting in 80% cell death through CDT and CT effects. Upon intravenous administration, FeMnOx@CPT displayed remarkable tumor accumulation, which enhanced tumor suppression in xenografts through improved CDT and CT effects. Moreover, no significant adverse effects were observed in the FeMnOx NP-treated animals. In the current study, the FeMnOx@CPT anticancer platform, with its boosted •OH-producing capability and ROS-cleavable drug release, has been validated utilizing in vitro and animal studies, suggesting its capacity as a viable strategy for clinical trials.

From Nanovesicles to Nanobubbles Based on Repeated Compression Method

Nanobubbles have been increasingly applied in biomedicine, which is attributed to their ability to work as ultrasound imaging contrast agents and powerful gene/drug carriers. Different production techniques or approaches have been developed to generate uniform and stable shelled nanobubbles. However, these shelled nanobubbles are usually prepared based on disordered shell materials, such as free phospholipids and polymers. In recent years, the continuous repeated compression method for a gas-liquid mixture has been developed to produce free and lipid-shelled nanobubbles. In this study, to explore the response of well-organized nanostructures to this method, the repeated compression method was used to treat preprepared liposomes and polymeric nanovesicles. Size distribution, morphologies, and ultrasound image contrast enhancement of these nanovesicles were determined before and after repeated compression. Results demonstrate that the presence of a phospholipid bilayer is vital to form liposome-based nanobubbles. And the low elastic modulus of the polymeric membrane is key to encapsulate gases into polymeric nanovesicles. Overall, it demonstrated the advantages of well-organized nanostructures to produce nanobubble structures, giving new insights into the preparation and understanding of nanobubbles.

Camptothecin-based prodrug nanomedicines for cancer therapy

Camptothecin (CPT) is a cytotoxic alkaloid that attenuates the replication of cancer cells via blocking DNA topoisomerase 1. Despite its encouraging and wide-spectrum antitumour activity, its application is significantly restricted owing to its instability, low solubility, significant toxicity, and acquired tumour cell resistance. This has resulted in the development of many CPT-based therapeutic agents, especially CPT-based nanomedicines, with improved pharmacokinetic and pharmacodynamic profiles. Specifically, smart CPT-based prodrug nanomedicines with stimuli-responsive release capacity have been extensively explored owing to the advantages such as high drug loading, improved stability, and decreased potential toxicity caused by the carrier materials in comparison with normal nanodrugs and traditional delivery systems. In this review, the potential strategies and applications of CPT-based nanoprodrugs for enhanced CPT delivery toward cancer cells are summarized. We appraise in detail the chemical structures and release mechanisms of these nanoprodrugs and guide materials chemists to develop more powerful nanomedicines that have real clinical therapeutic capacities.

Prolonging Treatment Window of Photodynamic Therapy with Self-Amplified H2 O2 -Activated Photodynamic/Chemo Combination Therapeutic Nanomedicines

Photodynamic therapy (PDT) is a promising approach to cancer therapy. However, the relatively short tumor retention time of photosensitizers (PSs) makes it difficult to catch the optimal treatment time and restricts multiple PDT within a single injection. In this study, a tumor-specific phototheranostic nanomedicine (DPPa NP) is developed for photodynamic/chemo combination therapy with a prolonged PDT treatment window. DPPa NP is prepared via encapsulating a hydrophobic oxidized bovine serum albumin (BSA-SOH)-conjugatable PS DPPa with amphiphilic H2 O2 -activatable chlorambucil (CL) prodrug mPEG-TK-CL. The released CL under H2 O2 treatment can not only kill tumor cells but also upregulate reactive oxygen species levels within tumor cells, leading to the almost full release of cargoes. The released DPPa may conjugate with overexpressed BSA-SOH, which results in the recovery of the fluorescence signal and photodynamic effect. More importantly, such conjugation transfers DPPa from a small molecule PS into a macromolecular PS with a long tumor retention time and treatment window of PDT, which enables multiple PDT. This study thus provides an effective strategy to prolong the treatment window of PDT and enables tumor-specific fluorescence imaging-guided combination therapy.

Development of a novel sialic acid-conjugated camptothecin prodrug for enhanced cancer chemotherapy

Camptothecin (CPT) is an attractive natural drug for cancer chemotherapy. However, the poor water solubility, non-targeting feature, and adverse side effects of CPT are significant obstacles to developing an effective anticancer drug. Here, for the first time, 9-thiol-sialic acid (9-SH-Sia) is coupled to CPT by forming a disulfide releasable carbonate linkage, resulting in a novel CPT prodrug (CPT-ss-Sia) that self-assembles into nanostructures in an aqueous solution. Strikingly, CPT-ss-Sia exhibited excellent in vitro properties, including enhanced water solubility, glutathione (GSH)-triggered CPT release, and increased E-lactone ring stability. Furthermore, CPT-ss-Sia had good cancer cell-killing ability comparable to CPT. Intravenous administration of CPT-ss-Sia significantly inhibited the growth of multiple types of tumors. Histological analysis showed that CPT-ss-Sia treatment significantly reduced lesions in tumor-bearing mice compared to CPT treatment. Notably, CPT-ss-Sia treatment did not adversely affect the body weight of the mice. This is the first report of the 9-SH-Sia conjugate-based prodrug. Overall, CPT-ss-Sia has broad clinical application prospects.

Reversibly "double locked" hydroxycamptothecin prodrug nanoparticles for targeted chemotherapy of lung cancer

Prodrug assembled nanoparticles integrate the merits of both prodrug and nanoparticle, which significantly improve pharmacokinetic parameters, enhance tumorous accumulation and decrease adverse effects, while they are challenged by disassembly upon dilution in blood, masking the superiority of nanoparticles (NPs). Herein, a reversibly "double locked" hydroxycamptothecin (HCPT) prodrug nanoparticle decorated with cyclic RGD peptide (cRGD) is developed for safe and efficient chemotherapy of orthotopic lung cancer in mice. HCPT prodrug is constructed from acetal (ace)-linked cRGD-PEG-ace-HCPT-ace-acrylate polymer, which is self-assembled into the nanoparticles with "the first lock" of HCPT. Then the nanoparticles undergo the in situ UV-crosslinking of the acrylate residues for constructing "the second lock" of HCPT. The obtained "double locked" nanoparticles (T-DLHN) with simple and well-defined construction are demonstrated to possess extremely high stability against 100-fold dilution and acid-triggered "unlock" including de-crosslinking and liberation of the pristine HCPT. In an orthotopic lung tumor of mouse model, T-DLHN reveals a prolonged circulation time of about 5.0 h, superb lung tumor-homing capacity with tumorous drug uptake of about 7.15%ID/g, resulting in significantly boosted anti-tumor activity and reduced adverse effects. Hence, these nanoparticles utilizing "double lock" and acid-triggered "unlock" strategies represent a unique and promising nanoplatform for safe and efficient drug delivery. STATEMENT OF SIGNIFICANCE: Prodrug assembled nanoparticles have the unique properties of the well-defined structure, systemic stability, improved pharmacokinetics, passive targeting and decreased adverse effects. However, prodrug assembled NPs would disassemble against extensive dilution in the blood circulation when intravenously injected into the body. Herein, we have designed a cRGD-directed reversibly "double-locked" HCPT prodrug nanoparticle (T-DLHN) for safe and efficient chemotherapy of orthotopic A549 human lung tumor xenografts. Upon intravenous injection, T-DLHN can overcome the shortcoming of disassembly against extensive dilution, prolong the circulation time due to the "double locked" configuration and then mediate targeted drug delivery into the tumors. After uptaken into the cells, T-DLHN undergoes concurrent de-crosslinking and liberation of HCPT under acidic condition for enhanced chemotherapeutic efficacy with negligible adverse effects.

Clearance of intracellular bacterial infections by hyaluronic acid-based ROS responsive drug delivery micelles

Pathogenic bacteria residing inside cells could cause disruption of cellular metabolic balance. Therefore, basing on high oxidative stress response of the intracellular bacteria infected micro-environment, a novel amphipathic micelle (HATAD-TCS) was developed consisting of hyaluronic acid-derivative and reactive oxygen species (ROS) - responsive group and antibacterial agent triclosan (TCS). ROS-generating cinnamaldehyde (CA) was incorporated into ROS-cleavable linkages which are future linked to the 1-decylamine to form hydrophobicity. The cinnamaldehyde released did not just killed bacteria however, also maintained intracellular ROS levels. In this study, the HATAD-TCS micelles have been characterized by scanning electron microscopy (SEM) and dynamic light scattering (DLS). The HATAD-TCS micelles could release drug gradually upon exposure to endogenous ROS being caused by infected intracellular bacteria. Furthermore, the more promising therapeutic effect of the HATAD-TCS micelles was observed in a mouse pneumonia model. These results might highlight a ROS-responsive hyaluronic acid-based nanoparticle, which could effectively treat intracellular bacterial infections.

Challenges and opportunities for improving the druggability of natural product: Why need drug delivery system?

Bioactive natural products (BNPs) are the marrow of medicinal plants, which are the secondary metabolites of organisms and have been the most famous drug discovery database. Bioactive natural products are famous for their enormous number and great safety in medical applications. However, BNPs are troubled by their poor druggability compared with synthesis drugs and are challenged as medicine (only a few BNPs are applied in clinical settings). In order to find a reasonable solution to improving the druggability of BNPs, this review summarizes their bioactive nature based on the enormous pharmacological research and tries to explain the reasons for the poor druggability of BNPs. And then focused on the boosting research on BNPs loaded drug delivery systems, this review further concludes the advantages of drug delivery systems on the druggability improvement of BNPs from the perspective of their bioactive nature, discusses why BNPs need drug delivery systems, and predicts the next direction.

Molybdenum-oxo-sulfide quantum dot-based nanocarrier: Efficient generation of reactive oxygen species via photo/chemodynamic therapy and stimulus-induced drug release

The fabrication of multifunctional nano-therapies has increased gradually to strengthen the therapeutic performance and minimize adverse effects of traditional cancer treatment strategies. Currently, we have designed a facile preparation drug-loaded nanocarrier for multimodal cancer therapy upon external stimuli. First, defect-rich molybdenum oxo-sulfide (MoO_xS_2-x) quantum dots (QDs) was synthesized via rapid biomineralization techniques with superior optical quantum yield reaching upto 37.28%. The presence of the Fenton ion, Mo^+IV/+VI, enables MoO_xS_2-x QDs to efficiently catalyze peroxide solutions to produce •OH radicals for chemodynamic treatment (CDT) and also deactivate the intracellular glutathione (GSH) enzymes through redox reaction for boosted reactive oxygen species (ROS)-mediated therapies. In addition, upon laser combination, MoO_xS_2-x QDs generate ROS for photodynamic therapy (PDT). Also, due to a large amount of sulfide content, MoO_xS_2-x QDs showed excellent H₂S gas release in acidic pH for cancer gas therapy. Then, MoO_xS_2-x QDs was further conjugated with ROS-responsive thioketal linked Camptothecin (CPT-TK-COOH) drug, forming a multitargeted MoO_xS_2-xCPT anticancer agent with better drug-loading efficiency (38.8%). After triggering the ROS generation through the CDT and PDT mechanisms, the thioketal linkage was disrupted, releasing up to 79% of the CPT drug in 48 h. Besides, in vitro experiments verified that MoO_xS_2-x QDs possess higher biocompatibility with 4T1 and HeLa cells but also showed considerable toxicity in the presence of laser/H₂O₂, resulting in 84.45% cell death through PDT/CDT and chemotherapeutic effects. Therefore, the designed MoO_xS_2-xCPT exhibited outstanding therapeutic benefits for image-guided cancer therapy.

Electrochemical H2O2 sensor based on a Au nanoflower-graphene composite for anticancer drug evaluation

Reliable H₂O₂ sensors for in situ cellular monitoring under drug stimulation can be developed as a powerful and versatile tool for drug evaluation. Herein, a novel electrochemical biosensor capable of detecting and quantifying H₂O₂ was fabricated by graphene and shape-controlled gold nanostructures. With the help of polyelectrolytes, gold exhibited hierarchical flower-like nanostructures. This kind of nanozyme material exhibited a prominent electrochemical response for H₂O₂. Electrocatalytic activity for H₂O₂ reduction with high sensitivity (5.07◊10^-4 mA μmol L^-1 cm^-2) and good detection capability (the lowest detection limit is 4.5 μmol L^-1 (S/N = 3)) were achieved. This electrochemical biosensor was successfully used to measure the concentration of H₂O₂ released from HepG2 hepatoma cells. Ascorbic acid (AA) and Camellia nitidissima Chi saponins (CNCS) were selected as model drugs, and their anticancer activities were compared by in situ monitoring of H₂O₂. Interestingly, the electrochemical sensor showed remarkable sensitivity, accuracy, and rapidity compared with the traditional enzymatic detection kit. In brief, the as-synthesized nanostructured H₂O₂ sensors can be applied to assess the antitumor properties of candidate drugs and inspire developments for personalized health care monitoring and cancer treatment.

Combined chemo and photo therapy of programmable prodrug carriers to overcome delivery barriers against nasopharyngeal carcinoma

Indocyanine green (ICG) has been employed in medical diagnostics due to its superior photophysical characteristics. However, these advantages are offset by its quick body clearance and inferior photo-stability. In this work, programmable prodrug carriers for chemotherapy/PDT/PTT against nasopharyngeal carcinoma (NPC) were created in order to increase photo-stability and get around biochemical hurdles. The programmable prodrug carriers (PEG-PLA@DIT-PAMAM) that proactively penetrated deeply into NPC tumors and produced the deep phototherapy and selective drug release under laser irradiation was created by dendrimer-DOX/ICG/TPP (DIT-PAMAM) and PEGylated poly (α-lipoic acid) (PLA) copolymer. Long circulation times and minimal toxicity to mammalian cells are two benefits of PEG-coated carriers. The overexpressed GSH on the tumor cell or vascular endothelial cell of the NPC disintegrated the PEG-g-PLA chains and released the DIT-PAMAM nanoparticles after the carriers had reached the NPC tumor periphery. Small, positively charged DIT-PAMAM nanoparticles may penetrate tumors effectively and remain inside tumor for an extended period of time. In addition, the induced ROS cleaved the thioketal linkers for both DOX and nanoparticles and product hyperthermia (PTT) to kill cancer cells under laser irradiation, facilitating faster diffusion of nanoparticles and more effective tumor penetration with a programmable publication of DOX. The programmable prodrug carries showed high photo-stability high photo-stability, which enabled very effective PDT, PTT, and tumor-specific DOX release. With the goal of combining the effects of chemotherapy, PDT, and PTT against NPC, this research showed the great efficacy of programmable prodrug carriers.

Preparation and Cytotoxicity Evaluation of Folic Acid-Modified YF8-OA Self-Assembled Lipid Prodrug Nanoparticles

This study aimed to improve the use of YF8, a matrine derivative obtained through chemical transformation of matrine extracted from Sophora alopecuroides. YF8 has demonstrated improved cytotoxicity compared to matrine, but its hydrophobic nature hinders its application. To overcome this, the lipid prodrug YF8-OA was synthesized by linking oleic acid (OA) to YF8 through an ester bond. Although YF8-OA could self-assemble into unique nanostructures in water, it was not sufficiently stable. To enhance the stability of YF8-OA lipid prodrug nanoparticles (LPs), we employed the strategy of PEGylation using DSPE-mPEG₂₀₀₀ or DSPE-mPEG₂₀₀₀ conjugated with folic acid (FA). This resulted in the formation of uniform spherical nanoparticles with greatly improved stability and a maximum drug load capacity upto 58.63%. Cytotoxicity was evaluated in A549, HeLa, and HepG2 cell lines. The results showed that in HeLa cells, the IC₅₀ value of YF8-OA/LPs with FA-modified PEGylation was significantly lower than that of YF8-OA/LPs modified by PEGylation alone. However, no significant enhancement was observed in A549 and HepG2 cells. In conclusion, the lipid prodrug YF8-OA can form nanoparticles in aqueous solution to address its poor water solubility. Modification with FA resulted in further enhanced cytotoxicity, providing a potential avenue for exerting the antitumor activity of matrine analogs.

Stimuli-responsive heparin-drug conjugates co-assembled into stable nanomedicines for cancer therapy

The combination of chemotherapy and photodynamic therapy (PDT) has the potential to complement single-drug therapies, but chemotherapeutic agents and photosensitizers often have compromised therapeutic efficacies and strong toxic effects. In this study, we exploited nanotechnology to address this challenge by utilizing heparin as a carrier for co-delivery of chemotherapeutic drugs and photosensitizers for synergistic cancer therapy. Specifically, heparin-paclitaxel (HP-PTX) and heparin-pyropheophorbide-a (HP-Ppa) were synthesized by attaching paclitaxel (PTX), a small molecular chemotherapeutic drug, through a reactive oxygen species (ROS)-responsive linker and Ppa, a photosensitizer, to heparin, respectively. Two conjugates co-assembled into a nanomedicine, HP-PP nanoparticles (NPs), for controllable co-delivery of Ppa and PTX into tumor cells. HP-PP NPs significantly enhanced the in vitro stability of HP-Ppa and the photostability of Ppa, and the synergistic actions of chemotherapy and PDT were confirmed from both in vitro and in vivo antitumor studies. Notably, HP-PP NPs enhanced tumor accumulation of Ppa up to 11-fold and the treatment of 4T1 tumor-bearing mice with HP-PP NPs resulted in a tumor growth inhibition of 98.1% without systemic toxicity. The strategy of co-assembly of heparin conjugates may offer great potential in enhancing the efficacy of combination therapy. STATEMENT OF SIGNIFICANCE: : We proposed a nano-delivery system, HP-PP NPs, which was constructed by co-assembly of heparin-paclitaxel (HP-PTX) and heparin-pyropheophorbide-a (HP-Ppa), to co-deliver PTX and Ppa for synergistic cancer therapy. HP-PP NPs enhanced the photostability and the in vitro stability of Ppa and HP-Ppa, and induced greater cytotoxicity than HP-PTX NPs or HP-Ppa NPs. This co-delivery system displays enhanced tumor accumulation and has a remarkable synergistic antitumor effect with a tumor growth inhibition of 98.1%.

Platinum-Coordinated Engineered Nanoreactors with O2 Self-Amplificationand On-Demand Cascade Chemo-Drug Synthesis for Self-Reinforcing Hypoxic Oncotherapy

How to efficiently synthesize toxic chemo-drugs in the hypoxia tumor microenvironment still faces a huge challenge. Herein, we have tailored engineered vehicle-free nanoreactors by coordination-driven co-assembly of photosensitizer indocyanine green (ICG), transition metal platinum (Pt), and nontoxic 1,5-dihydroxynaphthalene (DHN) to self-amplify O₂ and cascade chemo-drug synthesis in tumor cells for self-reinforcing hypoxic oncotherapy. Once vehicle-free nanoreactors are internalized into tumor cells, they show a serious instability that results in rapid disassembly and on-demand drug release under the stimuli of acidic lysosome and laser radiation. Notably, the released Pt can efficiently decompose the endogenous hydrogen peroxide (H₂O₂) into O₂ to alleviate tumor hypoxia, which is conducive to enhancing the photodynamic therapy (PDT) efficiency of the released ICG. Complementarily, a large amount of the ¹O₂ generated by PDT can efficiently oxidize the released nontoxic DHN into the highly toxic chemo-drug juglone. Therefore, such vehicle-free nanoreactors can achieve intracellular on-demand cascade chemo-drug synthesis and self-reinforce photo-chemotherapeutic efficacy on the hypoxic tumor. On the whole, such a simple, flexible, efficient, and nontoxic therapeutic strategy will broaden the study of on-demand chemo-drug synthesis and hypoxic oncotherapy.

Bovine serum albumin-based and dual-responsive targeted hollow mesoporous silica nanoparticles for breast cancer therapy

Combination therapy is an effective way to alleviate the shortcoming of monotherapy and enhances therapeutic efficacy. Herein, a distinctive hollow mesoporous silica nanoparticle (HMSNs) encapsulated with folic acid-modified bovine serum albumin (BSA-FA), denoted as HBF, was engineered for tumor targeting and dual-responsive release of loaded-therapeutic agents MD (methylene blue (MB) and doxorubicin (DOX)). The BSA molecule as a ''gatekeeper'' prevents premature drug leakage and actively unloads the cargos through BSA detachment in response to intracellular glutathione (GSH). Folic acid (FA) promotes the specific intracellular delivery of the drug to folate receptor (FR)-expressing cancer cells to improve the efficacy of chemo-photodynamic therapy (PDT). In vitro drug release profiles showed that the drug carrier could achieve pH/redox-responsive drug release from MD@HBF owing to the cleavage of the imine bonds between HMSNs-CHO and BSA-FA and BSA intramolecular disulfide bond. Additionally, a series of biological evaluations, such as cell uptake experiments, toxicity experiments, and in vivo therapeutic assays indicated that MD@HBF possesses the features of accurately targeting FR-expressing 4T1 cells to induce cells apoptosis in vitro, exhibits outstanding tumor cell synergistic killing efficiency of chemo-photodynamic therapy (combination index CI = 0.325), and inhibits tumors growth. These results demonstrated that the strategy of combining HMSNs with stimuli-responsive biodegradable protein molecules could provide a new potential direction toward the ''on-demand'' drug release for precision chemo-photodynamic therapy in cancer treatment.

High performance carbon dots based prodrug Platform: Image-Guided photodynamic and chemotherapy with On-Demand drug release upon laser irradiation

The design of therapeutic nanoplatforms based on fluorescent carbon dots (CDs) has become a viable strategy because of their aqueous solubility, biocompatibility, and ease of further functionalization. By doping various heteroatoms into pristine CDs structures, we synthesized N-, Cl-, and S-doped CDs (NClS/CDs), as well as Se-, N-, and Cl-doped CDs (NClSe/CDs) with superior optoelectronic properties using rapid and straightforward microwave heating. The quantum efficiencies of these NClS/CDs and NClSe/CDs were enhanced to 30.7 % and 42.9 %, respectively, compared to those of undoped CDs (0.66 %). Owing to their better light absorption properties, NClS/CDs efficiently produced reactive oxygen species (ROS) under 532 nm laser irradiation for photodynamic therapy (PDT). Considering the ROS generation and surface carrier abilities of NClS/CDs, we designed the loading of camptothecin (CPT) drug via a thioketal linker (TL), resulting in h/CDs@CPT nanovesicles (NVs) with a drug-loading efficiency of 46.5 %. Under laser irradiation in an acidic environment, ROS-triggered CPT release was observed, with 50.2 % of CPT released following the breakdown of the ROS-sensitive TL. In vitro cellular studies revealed that h/CDs@CPT NVs possessed minimal cytotoxicity toward HeLa and 4 T1 cancer cells, despite the high clinical efficacy of PDT and ROS-induced chemotherapeutic response under laser treatment. Confocal microscopy of HeLa and 4 T1 cells revealed that h/CDs@CPT NVs produced red-emissive photographs for potential cancer cell detection. Therefore, our study presents an image-guided PDT and chemotherapeutic platform based on h/CDs@CPT NVs, which will be an attractive candidate for future cancer treatment.

Hyaluronic Acid-based Supramolecular Nanomedicine with Optimized Ratio of Oxaliplatin/Chlorin e6 for Combined Chemotherapy and O2-Economized Photodynamic Therapy

Dual- or multi-modality combination therapy has become one of the most effective strategies to overcome drug resistance in cancer therapy, and the optimized ratio of the therapeutic agents working on the tumor greatly affects the therapeutic outcomes. However, the absence of a facile method to optimize the ratio of therapeutic agents in nanomedicine has, at least in part, impaired the clinical potential of combination therapy. Herein, a new cucurbit[7]uril (CB[7])-conjugated hyaluronic acid (HA) based nanomedicine was developed, in which both chlorin e6 (Ce6) and oxaliplatin (OX) were co-loaded non-covalently at an optimized ratio via facile host-guest complexation, for optimal, combined photodynamic therapy (PDT)/chemotherapy. To maximize the therapeutic efficacy, a mitochondrial respiration inhibitor, atovaquone (Ato), was also loaded into the nanomedicine to limit consumption of oxygen by the solid tumor, sparing oxygen for more efficient PDT. Additionally, HA on the surface of nanomedicine allowed targeted delivery to cancer cells with over-expressed CD44 receptors (such as CT26 cell lines). Thus, this supramolecular nanomedicine platform with an optimal ratio of photosensitizer and chemotherapeutic agent not only provides an important new tool for enhanced PDT/chemotherapy of solid tumors, but also offers a CB[7]-based host-guest complexation strategy to facilely optimize the ratio of therapeutic agents for multi-modality nanomedicine. STATEMENT OF SIGNIFICANCE: Chemotherapy remains the most common modality for cancer treatment in clinical practice. Combination therapy by co-delivery of two or more therapeutic agents has been recognized as one of the most effective strategies to improve therapeutic outcome of cancer treatment. However, the ratio of loaded drugs could not be facilely optimized, which may greatly affect the combination efficiency and overall therapeutic outcome. Herein, we developed a hyaluronic acid based supramolecular nanomedicine with facile method to optimize the ratio of two therapeutic agents for improved therapeutic outcome. This supramolecular nanomedicine not only provides an important new tool for enhanced photodynamic therapy/chemotherapy of solid tumors, but also offers insights in using macrocyclic molecule-based host-guest complexation to facilely optimize the ratio of therapeutic agents in multi-modality nanomedicine.

H2O2-responsive polymer prodrug nanoparticles with glutathione scavenger for enhanced chemo-photodynamic synergistic cancer therapy

The combination of chemotherapy and photodynamic therapy (PDT) based on nanoparticles (NPs) has been extensively developed to improve the therapeutic effect and decrease the systemic toxicity of current treatments. However, overexpressed glutathione (GSH) in tumor cells efficiently scavenges singlet oxygens (¹O₂) generated from photosensitizers and results in the unsatisfactory efficacy of PDT. To address this obstacle, here we design H₂O₂-responsive polymer prodrug NPs with GSH-scavenger (Ce6@P(EG-a-CPBE) NPs) for chemo-photodynamic synergistic cancer therapy. They are constructed by the co-self-assembly of photosensitizer chlorin e6 (Ce6) and amphiphilic polymer prodrug P(EG-a-CPBE), which is synthesized from a hydrophilic alternating copolymer P(EG-a-PD) by conjugating hydrophobic anticancer drug chlorambucil (CB) via an H₂O₂-cleavable linker 4-(hydroxymethyl)phenylboronic acid (PBA). Ce6@P(EG-a-CPBE) NPs can efficiently prevent premature drug leakage in blood circulation because of the high stability of the PBA linker under the physiological environment and facilitate the delivery of Ce6 and CB to the tumor site after intravenous injection. Upon internalization of Ce6@P(EG-a-CPBE) NPs by tumor cells, PBA is cleaved rapidly triggered by endogenous H₂O₂ to release CB and Ce6. Ce6 can effectively generate abundant ¹O₂ under 660 nm light irradiation to synergistically kill cancer cells with CB. Concurrently, PBA can be transformed into a GSH-scavenger (quinine methide, QM) under intracellular H₂O₂ and prevent the depletion of ¹O₂, which induces the cooperatively strong oxidative stress and enhanced cancer cell apoptosis. Collectively, such H₂O₂-responsive polymer prodrug NPs loaded with photosensitizer provide a feasible approach to enhance chemo-photodynamic synergistic cancer treatment.

Core-satellite nanoreactors based on cationic photosensitizer modified hollow CuS nanocage for ROS diffusion enhanced phototherapy of hypoxic tumor

Photodynamic therapy (PDT) efficiency is directly affected by the reactive oxygen species (ROS) generated by photosensitizers. However, ROSs' ultrashort life span and limited diffusion distance restrict the PDT efficiency. Therefore, it is important to control the delivery strategy of photosensitizers for PDT treatment. Herein, the core-satellite nanoreactors were fabricated with oxygen generation and ROS diffusion properties. The hollow CuS encapsulating horseradish peroxidase (HRP) was combined with the cationic photosensitizers (PEI-Ce6). The unique photosensitizers delivery strategy makes the nanoreactors achieve ROS diffusion-enhanced PDT effect. First, HRP in "core" (HRP@CuS) can decompose hydrogen peroxide (H₂O₂) to O₂, increasing O₂ levels on the surface of the nanoreactor. Second, the Ce6 molecules covalent-linked with PEI are uniformly dispersed on the surface of CuS as a "satellite", avoiding Ce6 aggregation and causing more Ce6 molecules be activated to produce more ¹O₂. Due to the Ce6 was on the surface of the CuS nanocages, the generated ROS may ensure a larger diffusion range. Meanwhile, the inherently CuS nanocages exhibit photothermal and photoacoustic (PA) effect. The photothermal effect further enhances the ROS diffusion. Under the guidance of PA imaging, nanoreactors exhibit highly efficient hypoxic tumor ablation via photodynamic and photothermal effect. Overall, the core-satellite nanoreactors provide an effective strategy for tumor therapy, further promoting the research of photosensitizers delivery.

A pH-Responsive Drug Delivery System Based on Conjugated Polymer for Effective Synergistic Chemo-/Photodynamic Therapy

Stimuli-responsive drug release and photodynamic therapy (PDT) have aroused extensive attention for their enormous potential in antitumor treatment. pH-responsive drug delivery systems (PFE-DOX-1 and PFE-DOX-2) based on water-soluble conjugated polymers were constructed in this work for high-performance synergistic chemo-/PDT therapy, in which the anticancer drug doxorubicin (DOX) is covalently attached to the side chains of the conjugated polymers via acid-labile imine and acylhydrazone bonds. Concurrently, the intense fluorescence of poly(fluorene-co-ethynylene) (PFE) is effectively quenched due to the energy/electron transfer (ET) between the PFE-conjugated backbone and DOX. Effective pH-responsive drug release from PFE-DOX-2 is achieved by the cleavage of acylhydrazone linkages in the acidic tumor intracellular microenvironment. Additionally, the drug release process can be monitored by the recovered fluorescence of conjugated polymers. Furthermore, the conjugated polymers can produce reactive oxygen species (ROS) under light irradiation after drug release in an acidic environment, which prevents possible phototoxicity to normal tissues. It is noted that PFE-DOX-2 demonstrates remarkable antitumor cell performance, which is attributed to its efficient cell uptake and powerful synergistic chemo-/PDT therapeutic effectiveness. This report thus provides a promising strategy for in vivo anticancer treatment with the construction of a stimuli-responsive multifunctional drug delivery system.

Synergistically Enhancing Tumor Chemotherapy Using an Aggregation-Induced Emission Photosensitizer on Covalently Conjugated Molecularly Imprinted Polymer Nanoparticles

Due to the polygenic and heterogeneous nature of the tumorigenesis process, traditional chemotherapy is far from desirable. Fabricating multifunctional nanoplatforms integrating photodynamic effect can synergistically enhance chemotherapy because they can make the cancer cells much sensitive to chemotherapeutics. However, how to assemble different units in nanoplatforms and minimize side effects caused by chemodrugs and photosensitizers (PSs) still needs to be explored. Herein, a nanoplatform CPP/PS-MIP@DOX is developed using a simultaneously covalently conjugated new aggregation-induced emission (AIE) PS and a cell-penetrating peptide (CPP) on the surface of silica-based molecularly imprinted polymer (MIP) nanoparticles, prepared with doxorubicin (DOX) as the template in the water system via a sol-gel technique. CPP/PS-MIP@DOX has good biocompatibility, high DOX-loading ability, promoted cellular uptake, and sustained and pH-sensitive drug release capability. Furthermore, it can efficiently penetrate into tumor tissue, accurately home to, and accumulate at the tumor site. As a result, a better efficacy with lower cytotoxicity is achieved with a smaller dosage of DOX by utilizing either the photodynamic effect or unique characteristics of the MIP. It is the first nanoplatform fabricated by chemically conjugating AIE PSs directly on the surface of the scaffold via the surface-decorated strategy and successfully applied in cancer therapy. This work provides an effective strategy by constructing AIE PS-based cancer nanomedicines with MIPs as scaffolds.

Biomimetic dual-responsive bioengineered nanotheranostics for intracellular cascade-synthesizing chemo-drugs and efficient oncotherapy

Intracellular-synthesized chemo-drugs based on the inherent characteristics of the tumor microenvironment (TME) have been extensively applied in oncotherapy. However, combining other therapeutic strategies to convert nontoxic small molecules into toxic small-molecule chemo-drugs in the TME is still a huge challenge. To address this issue, herein we have developed a biomimetic dual-responsive bioengineered nanotheranostics system via the supramolecular co-assembly of the nontoxic small-molecule 1,5-dihydroxynaphthalene (DHN) and small-molecule photosensitizer indocyanine green (ICG) followed by surface cloaking through red blood cell membranes (RBCs) for intracellular cascade-synthesizing chemo-drugs and efficient oncotherapy. Such nanotheranostics with a suitable diameter, core-shell structure, ultrahigh dual-drug payload rate, and excellent stability can efficiently accumulate in tumor regions and then internalize into tumor cells. Under the dual stimulations of near-infrared laser irradiation and acidic lysosomes, the nanotheranostics system exhibited exceptional instability under heat-primed membrane rupture and pH decrease, thereby achieving rapid disassembly and on-demand drug release. Furthermore, the released ICG can efficiently convert ³O₂ into ¹O₂. After that, the generated ¹O₂ can efficiently oxidize the released nontoxic DHN into the highly toxic chemo-drug juglone, thereby realizing intracellular cascade-synthesizing chemo-drugs and synergistic photodynamic-chemotherapy while reducing detrimental side effects on normal cells or tissues. Overall, it is envisioned that RBC-cloaked nanotheranostics with intracellular cascade-synthesizing chemo-drugs can provide a promising strategy for intracellular chemo-drug synthesis-based oncotherapy.

ROS- and pH-Responsive Polydopamine Functionalized Ti3C2Tx MXene-Based Nanoparticles as Drug Delivery Nanocarriers with High Antibacterial Activity

Premature drug release and poor controllability is a challenge in the practical application of tumor therapy, which may lead to poor chemotherapy efficacy and severe adverse effects. In this study, a reactive oxygen species (ROS)-cleavable nanoparticle system (MXene-TK-DOX@PDA) was designed for effective chemotherapy drug delivery and antibacterial applications. Doxorubicin (DOX) was conjugated to the surface of (3-aminopropyl)triethoxysilane (APTES)-functionalized MXene via an ROS-cleavable diacetoxyl thioketal (TK) linkage. Subsequently, the surfaces of the MXene nanosheets were coated with pH-responsive polydopamine (PDA) as a gatekeeper. PDA endowed the MXene-TK-DOX@PDA nanoparticles with superior biocompatibility and stability. The MXene-TK-DOX@PDA nanoparticles had an ultrathin planar structure and a small lateral size of approximately 180 nm. The as-synthesized nanoparticles demonstrated outstanding photothermal conversion efficiency, superior photothermal stability, and a remarkable extinction coefficient (23.3 L g^-1 cm^-1 at 808 nm). DOX exhibited both efficient ROS-responsive and pH-responsive release performance from MXene-TK-DOX@PDA nanoparticles due to the cleavage of the thioketal linker. In addition, MXene-TK-DOX@PDA nanoparticles displayed high antibacterial activity against both Gram-negative Escherichia coli (E. coli) and Gram-positive Bacillus subtilis (B. subtilis) within 5 h. Taken together, we hope that MXene-TK-DOX@PDA nanoparticles will enrich the drug delivery system and significantly expand their applications in the biomedical field.

A promising strategy for synergistic cancer therapy by integrating a photosensitizer into a hypoxia-activated prodrug

Herein, we fabricate a multifunctional molecular prodrug BAC where the chemotherapeutical agent camptothecin (CPT) is linked with a boron dipyrromethene (BODIPY)-based photosensitizer by an azobenzene chain which is sensitive to over-expressed azoreductase in hypoxic tumor cells. This prodrug was further loaded into biodegradable monomethoxy poly(ethylene glycol)-b-poly(caprolactone) (mPEG-b-PCL) to improve its solubility and tumor accumulation. The formed BAC nanoparticles (BAC NPs) can destroy aerobic tumor cells with relatively short distance from blood vessels by photodynamic therapy (PDT) under illumination. The PDT action inevitably leads to consumption of O2, and subsequently acute hypoxia which can induce cleavage of azobenzene linkage to boost release of CPT killing the other hypoxic interior tumor cells survived from PDT. Both in vitro and in vivo studies have verified that BAC NPs possess remarkable antitumor activity by a synergistic action of PDT and chemotherapy.

Current perspectives and trend of nanomedicine in cancer: A review and bibliometric analysis

The limitations of traditional cancer treatments are driving the creation and development of new nanomedicines. At present, with the rapid increase of research on nanomedicine in the field of cancer, there is a lack of intuitive analysis of the development trend, main authors and research hotspots of nanomedicine in the field of cancer, as well as detailed elaboration of possible research hotspots. In this review, data collected from the Web of Science Core Collection database between January 1st, 2000, and December 31st, 2021, were subjected to a bibliometric analysis. The co-authorship, co-citation, and co-occurrence of countries, institutions, authors, literature, and keywords in this subject were examined using VOSviewer, Citespace, and a well-known online bibliometrics platform. We collected 19,654 published papers, China produced the most publications (36.654%, 7204), followed by the United States (29.594%, 5777), and India (7.780%, 1529). An interesting fact is that, despite China having more publications than the United States, the United States still dominates this field, having the highest H-index and the most citations. Acs Nano, Nano Letters, and Biomaterials are the top three academic publications that publish articles on nanomedicine for cancer out of a total of 7580 academic journals. The most significant increases were shown for the keywords "cancer nanomedicine", "tumor microenvironment", "nanoparticles", "prodrug", "targeted nanomedicine", "combination", and "cancer immunotherapy" indicating the promising area of research. Meanwhile, the development prospects and challenges of nanomedicine in cancer are also discussed and provided some solutions to the major obstacles.

Dual (pH- and ROS-) Responsive Antibacterial MXene-Based Nanocarrier for Drug Delivery

In this study, a novel MXene (Ti₃C₂T_x)-based nanocarrier was developed for drug delivery. MXene nanosheets were functionalized with 3, 3'-diselanediyldipropionic acid (DSeDPA), followed by grafting doxorubicin (DOX) as a model drug to the surface of functionalized MXene nanosheets (MXene-Se-DOX). The nanosheets were characterized using scanning electron microscopy, atomic force microscopy (AFM), transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and zeta potential techniques. The drug-loading capacity (17.95%) and encapsulation efficiency (41.66%) were determined using ultraviolet-visible spectroscopy. The lateral size and thickness of the MXene nanosheets measured using AFM were 200 nm and 1.5 nm, respectively. The drug release behavior of the MXene-Se-DOX nanosheets was evaluated under different medium conditions, and the nanosheets demonstrated outstanding dual (reactive oxygen species (ROS)- and pH-) responsive properties. Furthermore, the MXene-Se-DOX nanosheets exhibited excellent antibacterial activity against both Gram-negative E. coli and Gram-positive B. subtilis.

Prodrug and Glucose Oxidase Coloaded Photodynamic Hydrogels for Combinational Therapy of Melanoma

With the advantages of high safety and selectivity, photodynamic therapy (PDT) has been widely used for cancer treatments, while the anticancer efficacy is often limited because of its relying on oxygen concentrations. Therefore, sole PDT fails to achieve the desired therapeutic effect for hypoxic tumors. To address this issue, we herein report the construction of prodrug and glucose oxidase (GOx) coloaded alginate (ALG) hydrogels for PDT-combined chemotherapy of melanoma. The hydrogels are in situ formed in tumor sites after injection of ALG solution containing semiconducting polymer nanoparticles, hypoxia-responsive prodrug tirapazamine (TPZ), and GOx, which is based on chelation of ALG by endogenous Ca²⁺. Due to the presence of semiconducting polymer nanoparticles acting as photosensitizers, the hydrogels mediate PDT to produce singlet oxygen (¹O₂) for directly killing tumor cells, in which oxygen is consumed to create a more hypoxic tumor microenvironment. Moreover, the loaded GOx within hydrogels can deplete oxygen to further aggravate tumor hypoxia. As such, TPZ is effectively activated by hypoxia to cause cancer cell death via chemotherapy. Thus, the hydrogels with laser irradiation achieve a combinational action of PDT with chemotherapy to almost completely eradicate tumors, leading to a much higher therapeutic efficacy relative to sole PDT. This study will provide a promising injectable hydrogel platform for effective treatments of cancer.

Overview of Nanoparticle-Based Approaches for the Combination of Photodynamic Therapy (PDT) and Chemotherapy at the Preclinical Stage

Simple Summary

The present review represents the outstanding and promising recent literature reports (2017–2022) on nanoparticle-based formulations developed for anticancer therapy with photodynamic therapy (PDT), photosensitizers, and chemotherapeutics. Besides brief descriptions of chemotherapeutics’ classification and of PDT mechanisms and limitations, several examples of nanosystems endowed with different responsiveness (e.g., acidic pH and reactive oxygen species) and peculiarity (e.g., tumor oxygenation capacity, active tumor targeting, and biomimetic features) are described, and for each drug combination, in vitro and in vivo results on preclinical cancer models are reported.

Abstract

The widespread diffusion of photodynamic therapy (PDT) as a clinical treatment for solid tumors is mainly limited by the patient’s adverse reaction (skin photosensivity), insufficient light penetration in deeply seated neoplastic lesions, unfavorable photosensitizers (PSs) biodistribution, and photokilling efficiency due to PS aggregation in biological environments. Despite this, recent preclinical studies reported on successful combinatorial regimes of PSs with chemotherapeutics obtained through the drugs encapsulation in multifunctional nanometric delivery systems. The aim of the present review deals with the punctual description of several nanosystems designed not only with the objective of co-transporting a PS and a chemodrug for combination therapy, but also with the goal of improving the therapeutic efficacy by facing the main critical issues of both therapies (side effects, scarce tumor oxygenation and light penetration, premature drug clearance, unspecific biodistribution, etc.). Therefore, particular attention is paid to the description of bio-responsive drugs and nanoparticles (NPs), targeted nanosystems, biomimetic approaches, and upconverting NPs, including analyzing the therapeutic efficacy of the proposed photo-chemotherapeutic regimens in in vitro and in vivo cancer models.

Recent advances in redox-responsive nanoparticles for combined cancer therapy

The combination of multiple therapeutic modalities has attracted increasing attention as it can achieve better therapeutic effects through different treatment mechanisms. However, traditional small molecule agents are non-specific to the tumor tissue, which leads to off-target toxic effects for healthy tissues. To solve this problem, a number of stimuli-responsive nanoscale drug-delivery systems have been developed. Among these stimuli, a high concentration of reactive oxygen species (ROS) and glutathione (GSH) are characteristic of the tumor microenvironment (TME), which can distinguish it from normal tissue. In this review, we summarize the redox-responsive nanoparticles (NPs) reported in the past three years classified by different functional groups, including GSH-responsive disulfide, ditelluride, and multivalent metal ions, ROS-responsive thioketal, arylboronic ester, aminoacrylate, and bilirubin as well as GSH/ROS dual-responsive diselenide and dicarbonyl thioethers. The prospects and challenges of redox-responsive NPs are also discussed.