Self-Strengthened Oxidation-Responsive Bioactivating Prodrug Nanosystem with Sequential and Synergistically Facilitated Drug Release for Treatment of Breast Cancer

Tumor-Specific Nano-Herb Delivery System with High L-Arginine Loading for Synergistic Chemo and Gas Therapy against Cervical Cancer

Cancer metastasis poses significant challenges in current clinical therapy. Osthole (OST) has demonstrated efficacy in treating cervical cancer and inhibiting metastasis. Despite these positive results, its limited solubility, poor oral absorption, low bioavailability, and photosensitivity hinder its clinical application. To address this limitation, a glutathione (GSH)-responded nano-herb delivery system (HA/MOS@OST&L-Arg nanoparticles, HMOA NPs) is devised for the targeted delivery of OST with cascade-activatable nitric oxide (NO) release. The HMOA NPs system is engineered utilizing enhanced permeability and retention (EPR) effects and active targeting mediated by hyaluronic acid (HA) binding to glycoprotein CD44. The cargoes, including OST and L-Arginine (L-Arg), are released rapidly due to the degradation of GSH-responsive mesoporous organic silica (MOS). Then abundant reactive oxygen species (ROS) are produced from OST in the presence of high concentrations of NAD(P)H quinone oxidoreductase 1 (NQO1), resulting in the generation of NO and subsequently highly toxic peroxynitrite (ONOO-) by catalyzing guanidine groups of L-Arg. These ROS, NO, and ONOO- molecules have a direct impact on mitochondrial function by reducing mitochondrial membrane potential and inhibiting adenosine triphosphate (ATP) production, thereby promoting increased apoptosis and inhibiting metastasis. Overall, the results indicated that HMOA NPs has great potential as a promising alternative for the clinical treatment of cervical cancer.

NQO-1 activatable NIR photosensitizer for visualization and selective killing of breast cancer cells

The diagnosis and treatment of breast cancer is of immense importance in improving patient outcomes. The biological marker NAD(P)H:quinone oxidoreductase 1 was utilized to design BrCyS-Q, a near-infrared activatable photosensitizer for breast cancer. BrCyS-Q was successfully employed to diagnose breast cancer cells using fluorescence and photodynamic inhibition. The findings of this research may offer novel insights for the diagnosis and treatment of clinical breast cancer via photodynamic therapy.

Red-Light-Responsive Polypeptoid Nanoassemblies Containing a Ruthenium(II) Polypyridyl Complex with Synergistically Enhanced Drug Release and ROS Generation for Anticancer Phototherapy

Polymer micelles/vesicles made of a red-light-responsive Ru(II)-containing block copolymer (PolyRu) are elaborated as a model system for anticancer phototherapy. PolyRu is composed of PEG and a hydrophobic polypeptoid bearing thioether side chains, 40% of which are coordinated with [Ru(2,2':6',2″-terpyridine)(2,2'-biquinoline)](PF6)2 via the Ru-S bond, resulting in a 67 wt % Ru complex loading capacity. Red-light illumination induces the photocleavage of the Ru-S bond and produces [Ru(2,2':6',2″-terpyridine)(2,2'-biquinoline)(H2O)](PF6)2. Meanwhile, ROS are generated under the photosensitization of the Ru complex and oxidize hydrophobic thioether to hydrophilic sulfoxide, causing the disruption of micelles/vesicles. During the disruption, ROS generation and Ru complex release are synergistically enhanced. PolyRu micelles/vesicles are taken up by cancer cells while they exhibit very low cytotoxicity in the dark. In contrast, they show much higher cytotoxicity under red-light irradiation. PolyRu micelles/vesicles are promising nanoassembly prototypes that protect metallodrugs in the dark but exhibit light-activated anticancer effects with spatiotemporal control for photoactivated chemotherapy and photodynamic therapy.

"Dual sensitive supramolecular curcumin nanoparticles" in "advanced yeast particles" mediate macrophage reprogramming, ROS scavenging and inflammation resolution for ulcerative colitis treatment

Ulcerative colitis (UC) faces some barriers in oral therapy, such as how to safely deliver drugs to the colon and accumulate in the colon lesions. Hence, we report an advanced yeast particles system loaded with supramolecular nanoparticles with ROS scavenger (curcumin) to treat UC by reducing oxidative stress state and inflammatory response and accelerating the reprogramming of macrophages. In this study, the dual-sensitive materials are bonded on β-cyclodextrin (β-CD), the D-mannose (Man) is modified to adamantane (ADA), and then loaded with curcumin (CUR), to form a functional supramolecular nano-delivery system (Man-CUR NPs) through the host-guest interaction. To improve gastrointestinal stability and colonic accumulation of Man-CUR NPs, yeast cell wall microparticles (YPs) encapsulated Man-CUR NPs to form Man-CUR NYPs via electrostatic adsorption and vacuum extrusion technologies. As expected, the YPs showed the strong stability in complex gastrointestinal environment. In addition, the Man modified supramolecular nanoparticles demonstrated excellent targeting ability to macrophages in the in vitro cellular uptake study and the pH/ROS sensitive effect of Man-CUR NPs was confirmed by the pH/ROS-dual stimulation evaluation. They also enhanced lipopolysaccharide (LPS)-induced inflammatory model in macrophages through downregulation of pro-inflammatory factors, upregulation of anti-inflammatory factors, M2 macrophage polarization, and scavenging the excess ROS. Notably, in DSS-induced mice colitis model, Man-CUR NYPs can reduce the inflammatory responses by modulating TLR4/NF-κB signaling pathways, alleviate oxidative stress by Nrf2/HO-1 signaling pathway, promote macrophages reprogramming and improve the favorable recovery of the damaged colonic tissue. Taken together, this study not only provides strategy for "supramolecular curcumin nanoparticles with pH/ROS sensitive and multistage therapeutic effects" in "advanced yeast particles", but also provided strong theoretical support multi-effect therapy for UC.

Docetaxel-loaded pH/ROS dual-responsive nanoparticles with self-supplied ROS for inhibiting metastasis and enhancing immunotherapy of breast cancer

BACKGROUND

Although stimuli-responsive nanoplatforms were developed to deliver immunogenic cell death (ICD) inducers to enhance cancer immunotherapy, the complete release of ICD inducers into the tumor microenvironment (TME) was limited by the inadequate supplementation of endogenous stimulus (e.g., reactive oxygen species (ROS)). To address this issue, we synthesized a self-responsive nanomaterial with self-supplied ROS, which mainly consists of a ROS responsive moiety HPAP and cinnamaldehyde (CA) as the ROS-generating agent. The endogenous ROS can accelerate the degradation of HPAP in materials to release docetaxel (DTX, an ICD inducer). In intracellular acidic environment, the pH-sensitive acetal was cleaved to release CA. The released CA in turn induces the generation of more ROS through mitochondrial damage, resulting in amplified DTX release. Using this self-cycling and self-responsive nanomaterial as a carrier, DTX-loaded pH/ROS dual-responsive nanoparticles (DTX/FA-CA-Oxi-αCD NPs) were fabricated and evaluated in vitro and in vivo.

RESULTS

In vitro experiments validated that the NPs could be effectively internalized by FA-overexpressed cells and completely release DTX in acidic and ROS microenvironments to induce ICD effect. These NPs significantly blocked 4T1 cell migration and decreased cell invasion. In vivo experiments demonstrated that the tumor-targeted NPs significantly inhibited tumor growth and blocked tumor metastasis. More importantly, these NPs significantly improved immunotherapy through triggering effector T-cell activation and relieving the immunosuppressive state of the TME.

CONCLUSIONS

Our results demonstrated that DTX/FA-CA-Oxi-αCD NPs displayed great potential in preventing tumor metastasis, inhibiting tumor growth, and improving the efficacy of anti-PD-1antibody.

Tailored Beta-Lapachone Nanomedicines for Cancer-Specific Therapy

Nanotechnology shows the power to improve efficacy and reduce the adverse effects of anticancer agents. As a quinone-containing compound, beta-lapachone (LAP) is widely employed for targeted anticancer therapy under hypoxia. The principal mechanism of LAP-mediated cytotoxicity is believed due to the continuous generation of reactive oxygen species with the aid of NAD(P)H: quinone oxidoreductase 1 (NQO1). The cancer selectivity of LAP relies on the difference between NQO1 expression in tumors and that in healthy organs. Despite this, the clinical translation of LAP faces the problem of narrow therapeutic window that is challenging for dose regimen design. Herein, the multifaceted anticancer mechanism of LAP is briefly introduced, the advance of nanocarriers for LAP delivery is reviewed, and the combinational delivery approaches to enhance LAP potency in recent years are summarized. The mechanisms by which nanosystems boost LAP efficacy, including tumor targeting, cellular uptake enhancement, controlled cargo release, enhanced Fenton or Fenton-like reaction, and multidrug synergism, are also presented. The problems of LAP anticancer nanomedicines and the prospective solutions are discussed. The current review may help to unlock the potential of cancer-specific LAP therapy and speed up its clinical translation.

Self-assembled nanoformulations of paclitaxel for enhanced cancer theranostics

Chemotherapy has occupied the critical position in cancer therapy, especially towards the post-operative, advanced, recurrent, and metastatic tumors. Paclitaxel (PTX)-based formulations have been widely used in clinical practice, while the therapeutic effect is far from satisfied due to off-target toxicity and drug resistance. The caseless multi-components make the preparation technology complicated and aggravate the concerns with the excipients-associated toxicity. The self-assembled PTX nanoparticles possess a high drug content and could incorporate various functional molecules for enhancing the therapeutic index. In this work, we summarize the self-assembly strategy for diverse nanodrugs of PTX. Then, the advancement of nanodrugs for tumor therapy, especially emphasis on mono-chemotherapy, combinational therapy, and theranostics, have been outlined. Finally, the challenges and potential improvements have been briefly spotlighted.

Cyclic RGD-Functionalized pH/ROS Dual-Responsive Nanoparticle for Targeted Breast Cancer Therapy

Breast cancer is the most common malignant tumor in women and is a big challenge to clinical treatment due to the high morbidity and mortality. The pH/ROS dual-responsive nanoplatforms may be an effective way to significantly improve the therapeutic efficacy of breast cancer. Herein, we report a docetaxel (DTX)-loaded pH/ROS-responsive NP that could achieve active targeting of cancer cells and selective and complete drug release for effective drug delivery. The pH/ROS-responsive NPs were fabricated using nanocarriers that consist of an ROS-responsive moiety (4-hydroxymethylphenylboronic acid pinacol ester, HPAP), cinnamaldehyde (CA, an aldehyde organic compound with anticancer activities) and cyclodextrin (α-CD). The NPs were loaded with DTX, modified with a tumor-penetration peptide (circular RGD, cRGD) and named DTX/RGD NPs. The cRGD could promote DTX/RGD NPs penetration into deep tumor tissue and specifically target cancer cells. After internalization by cancer cells through receptor-mediated endocytosis, the pH-responsive acetal was cleaved to release CA in the lysosomal acidic environment. Meanwhile, the high ROS in tumor cells induced the disassembly of NPs with complete release of DTX. In vitro cellular assays verified that DTX/RGD NPs could be effectively internalized by 4T1 cells, obviously inducing apoptosis, blocking the cell cycle of 4T1 cells and consequently, killing tumor cells. In vivo animal experiments demonstrated that the NPs could target to the tumor sites and significantly inhibit the tumor growth in 4T1 breast cancer mice. Both in vitro and in vivo investigations demonstrated that DTX/RGD NPs could significantly improve the antitumor effect compared to free DTX. Thus, the DTX/RGD NPs provide a promising strategy for enhancing drug delivery and cancer therapy.

Tumor-targeted AIE polymeric micelles mediated immunogenic sonodynamic therapy inhibits cancer growth and metastasis

Aggregation-induced emission luminogens (AIEgens) exhibit potent sonosensitivity in nanocarriers compared with conventional organic sonosensitizers owing to the strong fluorescence emission in the aggregated state. However, the premature drug leakage and ineffective tumor targeting of current AIE nanosonosensitizers critically restrict their clinical applications. Here, an AIEgen-based sonosensitizer (AIE/Biotin-M) with excellent sonosensitivity was developed by assembling salicylaldazine-based amphiphilic polymers (AIE-1) and 4T1 tumor-targeting amphiphilic polymers (DSPE-PEG-Biotin) for the effective delivery of salicylaldazine to 4T1 tumor tissues, aiming to mediate immunogenic SDT. In vitro, AIE/Biotin-M were highly stable and generated plentiful singlet oxygen (¹O₂) under ultrasound (US) irradiation. After AIE/Biotin-M targeted accumulation in the tumor, upon US irradiation, the generation of ¹O₂ not only led to cancer cell death, but also elicited a systemically immune response by causing the immunogenic cell death (ICD) of cancer cells. In addition to mediating SDT, AIE/Biotin-M could chelate and reduce Fe³⁺, Cu²⁺ and Zn²⁺ by salicylaldazine for inhibiting neovascularization in tumor tissues. Ultimately, AIE/Biotin-M systemically inhibited tumor growth and metastasis upon US irradiation. This study presents a facile approach to the development of AIE nanosonosensitizers for cancer SDT.

A co-delivery system based on chlorin e6-loaded ROS-sensitive polymeric prodrug with self-amplified drug release to enhance the efficacy of combination therapy for breast tumor cells

Background: Recently, various combination therapies for tumors have garnered popularity because of their synergistic effects in improving therapeutic efficacy and reducing side effects. However, incomplete intracellular drug release and a single method of combining drugs are inadequate to achieve the desired therapeutic effect.

Methods: A reactive oxygen species (ROS)-sensitive co-delivery micelle (Ce6@PTP/DP). It was a photosensitizer and a ROS-sensitive paclitaxel (PTX) prodrug for synergistic chemo-photodynamic therapy. Micelles size and surface potential were measured. In vitro drug release, cytotoxicity and apoptosis were investigated.

Results: Ce6@PTP/DP prodrug micelles exhibited good colloidal stability and biocompatibility, high PTX and Ce6 loading contents of 21.7% and 7.38%, respectively. Upon light irradiation, Ce6@PTP/DP micelles endocytosed by tumor cells can generate sufficient ROS, not only leading to photodynamic therapy and the inhibition of tumor cell proliferation, but also triggering locoregional PTX release by cleaving the thioketal (TK) bridged bond between PTX and methoxyl poly (ethylene glycol). Furthermore, compared with single drug-loaded micelles, the light-triggered Ce6@PTP/DP micelles exhibited self-amplified drug release and significantly greater inhibition of HeLa cell growth.

Conclusion: The results support that PTX and Ce6 in Ce6@PTP/DP micelles exhibited synergistic effects on cell-growth inhibition. Thus, Ce6@PTP/DP micelles represent an alternative for realizing synergistic chemo-photodynamic therapy.

A technical note on emerging combination approach involved in the onconanotherapeutics

Cancer is the second cause of mortality worldwide, and the currently available conventional treatment approach is associated with serious side effects and poor clinical outcomes. Based on the outcome of the exploratory preclinical and clinical studies, it was found that therapeutic response increases multiple folds when anticancer drugs are used in combination. However, the conventional combination of anticancer drugs was associated with various limitations such as increased cost of treatment, systemic toxicity, drug resistance, and reduced pharmacokinetic attributes. Hence, attempts were made to formulate nanocarrier fabricated combinatorial drugs (NFCDs) to effectively manage and treat cancer. This approach offers several advantages, such as improved stability, lower drug exposure, targeted drug delivery, low side effects, and improved clinical outcome. Hence, in this review, first time, we have discussed the recent advancement and various types of nano carrier-based combinatorial drug delivery systems in a different type of cancer and highlighted the personalized combinatorial theranostic medicine as a futuristic anticancer treatment approach.

Emerging Strategies in Stimuli-Responsive Prodrug Nanosystems for Cancer Therapy

Prodrugs are chemically modified drug molecules that are inactive before administration. After administration, they are converted in situ to parent drugs and induce the mechanism of action. The development of prodrugs has upgraded conventional drug treatments in terms of bioavailability, targeting, and reduced side effects. Especially in cancer therapy, the application of prodrugs has achieved substantial therapeutic effects. From serendipitous discovery in the early stage to functional design with pertinence nowadays, the importance of prodrugs in drug design is self-evident. At present, studying stimuli-responsive activation mechanisms, regulating the stimuli intensity in vivo, and designing nanoscale prodrug formulations are the major strategies to promote the development of prodrugs. In this review, we provide an outlook of recent cutting-edge studies on stimuli-responsive prodrug nanosystems from these three aspects. We also discuss prospects and challenges in the future development of such prodrugs.

Allyl phenyl selenides as H2O2 acceptors to develop ROS-responsive theranostic prodrugs

Reactive oxygen species (ROS)-responsive prodrugs have received significant attention due to their capacity to target tumors to relieve the side effects caused by chemotherapy. Herein, a series of novel H₂O₂-activated theranostic prodrugs (CPTSe1-CPTSe7) were developed containing allyl phenyl selenide moieties as H₂O₂ acceptors. Compared with conventional boronate ester-based prodrug CPT-B, CPTSe1 was more stable in human plasma and showed a more complete release of camptothecin (CPT) in H₂O₂ inducing experiment. The selectively activated fluorescence signals of CPTSe1 in tumor cells make it useful for real-time monitoring of CPT release and H₂O₂ detection. Furthermore, excellent selectivity of CPTSe1 was achieved for tumor cells over normal cells. Our results provide a new platform for the development of H₂O₂-responsive theranostic prodrugs.

Taxanes prodrug-based nanomedicines for cancer therapy

Malignant tumor remains a huge threat to human health and chemotherapy still occupies an important place in clinical tumor treatment. As a kind of potent antimitotic agent, taxanes act as the first-line broad-spectrum cancer drug in clinical use. However, disadvantages such as prominent hydrophobicity, severe off-target toxicity or multidrug resistance lead to unsatisfactory therapeutic effects, which restricts its wider usage. The efficient delivery of taxanes is still quite a challenge despite the rapid developments in biomaterials and nanotechnology. Great progress has been made in prodrug-based nanomedicines (PNS) for cancer therapy due to their outstanding advantages such as high drug loading efficiency, low carrier induced immunogenicity, tumor stimuli-responsive drug release, combinational therapy and so on. Based on the numerous developments in this filed, this review summarized latest updates of taxanes prodrugs-based nanomedicines (TPNS), focusing on polymer-drug conjugate-based nanoformulations, small molecular prodrug-based self-assembled nanoparticles and prodrug-encapsulated nanosystems. In addition, the new trends of tumor stimuli-responsive TPNS were also discussed. Moreover, the future challenges of TPNS for clinical translation were highlighted. We here expect this review will inspire researchers to explore more practical taxanes prodrug-based nano-delivery systems for clinical use.

Recent Advances in Stimuli-Sensitive Amphiphilic Polymer-Paclitaxel Prodrugs

Paclitaxel (PTX) is a broad-spectrum chemotherapy drug employed in the treatment of a variety of tumors. However, the clinical applications of PTX are limited by its poor water solubility. Adjuvants are widely used to overcome this issue. However, these adjuvants often have side effects and poor biodistribution. The smart drug delivery system is a promising strategy for the improvement of solubility, permeability, and stability of drugs, and can promote sustained controlled release, increasing therapeutic efficacy and reducing side effects. Polymeric prodrugs show great advantages for drug delivery due to their high drug loading and stability. There has been some groundbreaking work in the development of PTX-based stimulus-sensitive polymeric prodrug micelles, which is summarized in this study. We consider these in terms of the four main types of stimulus (pH, reduction, enzyme, and reactive oxygen species (ROS)). The design, synthesis, and biomedical applications of stimulus-responsive polymeric prodrugs of PTX are reviewed, and the current research results and future directions of the field are summarized.

Tumor-specific nitric oxide generator to amplify peroxynitrite based on highly penetrable nanoparticles for metastasis inhibition and enhanced cancer therapy

Multiple biological barriers and tumor metastasis severely impede the tumor therapy. To address these adversities, an acid-activated poly (ethylene glycol)-poly-l-lysine-2,3-dimethylmaleic anhydride/poly (ε-caprolactone)-poly(l-arginine)/β-lapachone nanoparticles (mPEG-PLL-DMA/PCL-P(L-arg)/β-Lap, PLM/PPA/β-Lap NPs) were constructed with charge-reversal and size-reduction for β-Lap delivery with a cascade reaction of reactive oxygen species (ROS) and nitric oxide (NO) production. The nanosystem exhibited highly penetrable, superior cellular uptake and desirable endo-lysosomal escape thanks to size-reduction, charge-reversal and proton sponge, respectively. The vast bulk of ROS, which rapidly generated from β-Lap under high concentration quinone oxidoreductase 1 (NQO1), catalyzed guanidine groups to produce NO and generated highly toxic peroxynitrite (ONOO^-). ONOO^- would activate pro-matrix metalloproteinases (pro-MMPs) to generate MMPs, degrade the dense extracellular matrix (ECM) to augment the penetration capability, and aggravate DNA damage. NO and ONOO^- influenced mitochondrial function by decreasing mitochondrial membrane potential and prevented the production of adenosine triphosphate (ATP), which inhibited the ATP-dependent tumor-derived microvesicles (TMVs) and restrained tumor metastasis. NO was defined as an epithelial mesenchymal transition (EMT) inhibitor to restrain tumor metastasis. All consequences demonstrated that PLM/PPA/β-lap NPs exhibited efficient penetration capability, outstanding anti-metastasis activity and favorable antitumor efficacy. Those novel acid-activated NPs are intended to provide further inspiration for multifunctional NO gas therapy.

Elaborately Engineering a Self-Indicating Dual-Drug Nanoassembly for Site-Specific Photothermal-Potentiated Thrombus Penetration and Thrombolysis

Thrombotic cardio-cerebrovascular diseases seriously threaten human health. Currently, conventional thrombolytic treatments are challenged by the low utilization, inferior thrombus penetration, and high off-target bleeding risks of most thrombolytic drugs, resulting in unsatisfactory treatment outcomes. Herein, it is proposed that these challenges can be overcome by precisely integrating the conventional thrombolytic strategy with photothermal therapy. After co-assembly engineering optimization, a fibrin-targeting peptide-decorated nanoassembly of DiR (a photothermal probe) and ticagrelor (TGL, an antiplatelet drug) is prepared for thrombus-homing delivery, abbreviated as FT-DT NPs. The elaborately engineered nanoassembly shows multiple advantages, including simple preparation with high drug co-loading capacity, synchronous delivery of two drugs with long systemic circulation, thrombus-targeted accumulation with self-indicating function, as well as photothermal-potentiated thrombus penetration and thrombolysis with high therapeutic efficacy. As expected, FT-DT NPs not only show bright fluorescence signals in the embolized vessels, but also perform photothermal/antiplatelet synergistic thrombolysis in vivo. This study offers a simple and versatile co-delivery nanoplatform for imaging-guided photothermal/antiplatelet dual-modality thrombolysis.

Small-Molecule Prodrug Nanoassemblies: An Emerging Nanoplatform for Anticancer Drug Delivery

The antitumor efficiency and clinical translation of traditional nanomedicines is mainly restricted by low drug loading, complex preparation technology, and potential toxicity caused by the overused carrier materials. In recent decades, small-molecule prodrug nanoassemblies (SMP-NAs), which are formed by the self-assembly of prodrugs themselves, have been widely investigated with distinct advantages of ultrahigh drug-loading and negligible excipients-trigged adverse reaction. Benefited from the simple preparation process, SMP-NAs are widely used for chemotherapy, phototherapy, immunotherapy, and tumor diagnosis. In addition, combination therapy based on the accurate co-delivery behavior of SMP-NAs can effectively address the challenges of tumor heterogeneity and multidrug resistance. Recent trends in SMP-NAs are outlined, and the corresponding self-assembly mechanisms are discussed in detail. Besides, the smart stimuli-responsive SMP-NAs and the combination therapy based on SMP-NAs are summarized, with special emphasis on the structure-function relationships. Finally, the outlooks and potential challenges of SMP-NAs in cancer therapy are highlighted.

Investigating the crucial roles of aliphatic tails in disulfide bond-linked docetaxel prodrug nanoassemblies

Disulfide bond-bridging strategy has been extensively utilized to construct tumor specificity-responsive aliphatic prodrug nanoparticles (PNPs) for precise cancer therapy. Yet, there is no research shedding light on the impacts of the saturation and cis-trans configuration of aliphatic tails on the self-assembly capacity of disulfide bond-linked prodrugs and the in vivo delivery fate of PNPs. Herein, five disulfide bond-linked docetaxel-fatty acid prodrugs are designed and synthesized by using stearic acid, elaidic acid, oleic acid, linoleic acid and linolenic acid as the aliphatic tails, respectively. Interestingly, the cis-trans configuration of aliphatic tails significantly influences the self-assembly features of prodrugs, and elaidic acid-linked prodrug with a trans double bond show poor self-assembly capacity. Although the aliphatic tails have almost no effect on the redox-sensitive drug release and cytotoxicity, different aliphatic tails significantly influence the chemical stability of prodrugs and the colloidal stability of PNPs, thus affecting the in vivo pharmacokinetics, biodistribution and antitumor efficacy of PNPs. Our findings illustrate how aliphatic tails affect the assembly characteristic of disulfide bond-linked aliphatic prodrugs and the in vivo delivery fate of PNPs, and thus provide theoretical basis for future development of disulfide bond-bridged aliphatic prodrugs.

Folic acid-modified ROS-responsive nanoparticles encapsulating luteolin for targeted breast cancer treatment

Luteolin (Lut) is a natural flavonoid polyphenolic compound with multiple pharmacological activities, such as anti-oxidant, anti-inflammatory, and anti-tumor effects. However, the poor aqueous solubility and low bioactivity of Lut restrict its clinical translation. Herein, we developed a reactive oxygen species (ROS)-responsive nanoplatforms to improve the bioactivity of Lut. Folic acid (FA) was employed to decorate the nanoparticles (NPs) to enhance its targeting ability. The size of Lut-loaded ROS-responsive nanoparticles (Lut/Oxi-αCD NPs) and FA-modified Lut/Oxi-αCD NPs (Lut/FA-Oxi-αCD NPs) is 210.5 ± 6.1 and 196.7 ± 1.8 nm, respectively. Both Lut/Oxi-αCD NPs and Lut/FA-Oxi-αCD NPs have high drug loading (14.83 ± 3.50 and 16.37 ± 1.47%, respectively). In vitro cellular assays verified that these NPs could be efficiently internalized by 4T1 cells and the released Lut from NPs could inhibit tumor cells proliferation significantly. Animal experiments demonstrated that Lut/Oxi-αCD NPs, especially Lut/FA-Oxi-αCD NPs obviously accumulated at tumor sites, and inhibited tumor growth ∼3 times compared to the Lut group. In conclusion, the antitumor efficacy of Lut was dramatically improved by targeting delivery with the ROS-responsive nanoplatforms.

Prodrug-based nano-delivery strategy to improve the antitumor ability of carboplatin in vivo and in vitro

Chemotherapy plays a major role in the treatment of cancer, but it still has great limitations in anti-tumor effect. Carboplatin (CAR) is the first-line drug in the treatment of non-small cell lung cancer, but the therapeutic effect is demonstrated weak. Therefore, we modified CAR with hexadecyl chain and polyethylene glycol, so as to realize its liposolubility and PEGylation. The synthesized amphiphilic CAR prodrugs could self-assemble into polymer micelles in water with an average particle size about 11.8 nm and low critical micelles concentration (0.0538 mg·mL^-1). In vivo pharmacodynamics and cytotoxicity experiment evidenced that the polymer micelles were equipped with preferable anti-tumor effect, finally attained the aim of elevating anti-tumor effect and prolonging retention time in vivo. The self-assembled micelles skillfully solve the shortcomings of weak efficacy of CAR, which provides a powerful platform for the application of chemical drug in oncology.

A pH/ROS cascade-responsive and self-accelerating drug release nanosystem for the targeted treatment of multi-drug-resistant colon cancer

The efficacy of chemotherapeutic agents for colon cancer treatment is limited by multidrug resistance (MDR) and insufficient intracellular release of the administered nanomedicine. To overcome these limitations, we constructed a pH/ROS cascade-responsive and self-accelerating drug release nanoparticle system (PLP-NPs) for the treatment of multidrug-resistant colon cancer. The PLP-NPs comprised a reactive oxygen species (ROS)-sensitive polymeric paclitaxel (PTX) prodrug (DEX-TK-PTX), a pH-sensitive poly(l-histidine) (PHis), and beta-lapachone (Lapa), a ROS-generating agent. We found that PLP-NPs could accumulate in tumor tissue through enhancement of the permeability and retention (EPR) effect, and were subsequently internalized by cancer cells via the endocytic pathway. Within the acidic endo-lysosomal environment, PHis protonation facilitated the escape of the PLP-NPs from the lysosome and release of Lapa. The released Lapa generated a large amount of ROS, consumed ATP, and downregulated P-glycoprotein (P-gp) production through the activity of NQO1, an enzyme that is specifically overexpressed in tumor cells. In addition, the generated ROS promoted the release of PTX from DEX-TK-PTX to kill cancer cells, while ATP depletion inhibited P-gp-mediated MDR. In vitro and in vivo experiments subsequently confirmed that PLP-NPs induced tumor-specific cytotoxicity and overcame the MDR of colon cancer. Our findings indicate that the use of the PLP-NPs system represents a promising strategy to counter MDR in the treatment of colon cancer.

pH and ROS sequentially responsive podophyllotoxin prodrug micelles with surface charge-switchable and self-amplification drug release for combating multidrug resistance cancer

Multidrug resistance (MDR) is one of the main reasons for tumor chemotherapy failure. Podophyllotoxin (PPT) has been reported that can suppress MDR cancer cell growth; however, effective delivery of PPT to MDR cancer cells is challenged by cascaded bio-barriers. To effectively deliver PPT to MDR cancer cells, a PPT polymeric prodrug micelle (PCDMA) with the charge-conversion capability and self-acceleration drug release function are fabricated, which is composed of a pH and reactive oxygen species (ROS) sequentially responsive PPT-polymeric prodrug and an ROS generation agent, cucurbitacin B (CuB). After reach to tumor tissue, the surface charge of PCDMA could rapidly reverse to positive in the tumor extracellular environment to promote cellular uptake. Subsequently, the PCDMA could be degraded to release PPT and CuB in response to an intracellular high ROS condition. The released CuB is competent for generating ROS, which in turn accelerates the release of PPT and CuB. Eventually, the released PPT could kill MDR cancer cells. The in vitro and in vivo studies demonstrated that PCDMA was effectively internalized by cancer cells and produces massive ROS intracellular, rapid release drug, and effectively overcame MDR compared with the control cells, due to the tumor-specific weakly acidic and ROS-rich environment. Our results suggest that the pH/ROS dual-responsive PCDMA micelles with surface charge-reversal and self-amplifying ROS-response drug release provide an excellent platform for potential MDR cancer treatment.

Emerging nanotaxanes for cancer therapy

The clinical application of taxane (including paclitaxel, docetaxel, and cabazitaxel)-based formulations is significantly impeded by their off-target distribution, unsatisfactory release, and acquired resistance/metastasis. Recent decades have witnessed a dramatic progress in the development of high-efficiency, low-toxicity nanotaxanes via the use of novel biomaterials and nanoparticulate drug delivery systems (nano-DDSs). Thus, in this review, the achievements of nanotaxanes-targeted delivery and stimuli-responsive nano-DDSs-in preclinical or clinical trials have been outlined. Then, emerging nanotherapeutics against tumor resistance and metastasis have been overviewed, with a particular emphasis on synergistic therapy strategies (e.g., combination with surgery, chemotherapy, radiotherapy, biotherapy, immunotherapy, gas therapy, phototherapy, and multitherapy). Finally, the latest oral nanotaxanes have been briefly discussed.

Erythrocyte membrane-camouflaged carrier-free nanoassembly of FRET photosensitizer pairs with high therapeutic efficiency and high security for programmed cancer synergistic phototherapy

Phototherapy has been intensively investigated as a non-invasive cancer treatment option. However, its clinical translation is still impeded by unsatisfactory therapeutic efficacy and severe phototoxicity. To achieve high therapeutic efficiency and high security, a nanoassembly of Forster Resonance Energy Transfer (FRET) photosensitizer pairs is developed on basis of dual-mode photosensitizer co-loading and photocaging strategy. For proof-of-concept, an erythrocyte-camouflaged FRET pair co-assembly of chlorine e6 (Ce6, FRET donor) and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide (DiR, FRET acceptor) is investigated for breast cancer treatment. Notably, Ce6 in the nanoassemby is quenched by DiR and could be unlocked for photodynamic therapy (PDT) only when DiR is photobleached by 808-nm laser. As a result, Ce6-caused phototoxicity could be well controlled. Under cascaded laser irradiation (808–660 nm), tumor-localizing temperature rise following laser irradiation on DiR not only induces tumor cell apoptosis but also facilitates the tumor penetration of NPs, relieves tumor hypoxia, and promotes the PDT efficacy of Ce6. Such FRET pair-based nanoassembly provides a new strategy for developing multimodal phototherapy nanomedicines with high efficiency and good security.

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Biomimetic carrier-free nanoassembly developed by FRET photosensitizer pairs.

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Dual-mode co-loading and photocaging strategy for programmed cancer synergistic phototherapy.

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Avoiding the ROS-induced off-target phototoxicity by the intelligently controlled ROS activation.

Reactive Oxygen Species (ROS)-Responsive Prodrugs, Probes, and Theranostic Prodrugs: Applications in the ROS-Related Diseases

Elevated levels of reactive oxygen species (ROS) have commonly been implicated in a variety of diseases, including cancer, inflammation, and neurodegenerative diseases. In light of significant differences in ROS levels between the nonpathogenic and pathological tissues, an increasing number of ROS-responsive prodrugs, probes, and theranostic prodrugs have been developed for the targeted treatment and precise diagnosis of ROS-related diseases. This review will summarize and provide insight into recent advances in ROS-responsive prodrugs, fluorescent probes, and theranostic prodrugs, with applications to different ROS-related diseases and various subcellular organelle-targetable and disease-targetable features. The ROS-responsive moieties, the self-immolative linkers, and the typical activation mechanism for the ROS-responsive release are also summarized and discussed.

Recent Advances and Challenges in Controlling the Spatiotemporal Release of Combinatorial Anticancer Drugs from Nanoparticles

To overcome cancer, various chemotherapeutic studies are in progress; among these, studies on nano-formulated combinatorial drugs (NFCDs) are being actively pursued. NFCDs function via a fusion technology that includes a drug delivery system using nanoparticles as a carrier and a combinatorial drug therapy using two or more drugs. It not only includes the advantages of these two technologies, such as ensuring stability of drugs, selectively transporting drugs to cancer cells, and synergistic effects of two or more drugs, but also has the additional benefit of enabling the spatiotemporal and controlled release of drugs. This spatial and temporal drug release from NFCDs depends on the application of nanotechnology and the composition of the combination drug. In this review, recent advances and challenges in the control of spatiotemporal drug release from NFCDs are provided. To this end, the types of combinatorial drug release for various NFCDs are classified in terms of time and space, and the detailed programming techniques used for this are described. In addition, the advantages of the time and space differences in drug release in terms of anticancer efficacy are introduced in depth.

Remote loading paclitaxel-doxorubicin prodrug into liposomes for cancer combination therapy

The combination of paclitaxel (PTX) and doxorubicin (DOX) has been widely used in the clinic. However, it remains unsatisfied due to the generation of severe toxicity. Previously, we have successfully synthesized a prodrug PTX-S-DOX (PSD). The prodrug displayed comparable in vitro cytotoxicity compared with the mixture of free PTX and DOX. Thus, we speculated that it could be promising to improve the anti-cancer effect and reduce adverse effects by improving the pharmacokinetics behavior of PSD and enhancing tumor accumulation. Due to the fact that copper ions (Cu²⁺) could coordinate with the anthracene nucleus of DOX, we speculate that the prodrug PSD could be actively loaded into liposomes by Cu²⁺ gradient. Hence, we designed a remote loading liposomal formulation of PSD (PSD LPs) for combination chemotherapy. The prepared PSD LPs displayed extended blood circulation, improved tumor accumulation, and more significant anti-tumor efficacy compared with PSD NPs. Furthermore, PSD LPs exhibited reduced cardiotoxicity and kidney damage compared with the physical mixture of Taxol and Doxil, indicating better safety. Therefore, this novel nano-platform provides a strategy to deliver doxorubicin with other poorly soluble antineoplastic drugs for combination therapy with high efficacy and low toxicity.

An exosome-like programmable-bioactivating paclitaxel prodrug nanoplatform for enhanced breast cancer metastasis inhibition

Metastasis is closely associated with high breast cancer mortality. Although nanotechnology-based anti-metastatic treatments have developed rapidly, the anti-metastasis efficiency is still far from satisfactory, mainly due to the poor recognition of circulating tumor cells (CTCs) in blood. Herein, we developed an exosome-like sequential-bioactivating prodrug nanoplatform (EMPCs) to overcome the obstacle. Specifically, the reactive oxygen species (ROS)-responsive thioether-linked paclitaxel-linoleic acid conjugates (PTX-S-LA) and cucurbitacin B (CuB) are co-encapsulated into polymeric micelles, and the nanoparticles are further decorated with exosome membrane (EM). The resulting EMPCs could specifically capture and neutralize CTCs during blood circulation through the high-affinity interaction between cancer cell membrane and homotypic EM. Following cellular uptake, EMPCs first release CuB, remarkably blocking tumor metastasis via downregulation of the FAK/MMP signaling pathway. Moreover, CuB obviously elevates the intracellular oxidative level to induce a sequential bioactivation of ROS-responsive PTX-S-LA. In vitro and in vivo results demonstrate that EMPCs not only exhibit amplified prodrug bioactivation, prolonged blood circulation, selective targeting of homotypic tumor cells, and enhanced tumor penetration, but also suppress tumor metastasis through CTCs clearance and FAK/MMP signaling pathway regulation. This study proposes an integrated approach for mechanism-based inhibition of tumor metastasis and manifests a promising potential of programmable-bioactivating prodrug nanoplatform for cancer metastasis inhibition.

Dual Receptor-Targeted and Redox-Sensitive Polymeric Micelles Self-Assembled from a Folic Acid-Hyaluronic Acid-SS-Vitamin E Succinate Polymer for Precise Cancer Therapy

Purpose

Poor site-specific delivery and insufficient intracellular drug release in tumors are inherent disadvantages to successful chemotherapy. In this study, an extraordinary polymeric micelle nanoplatform was designed for the efficient delivery of paclitaxel (PTX) by combining dual receptor-mediated active targeting and stimuli response to intracellular reduction potential.

Methods

The dual-targeted redox-sensitive polymer, folic acid-hyaluronic acid-SS-vitamin E succinate (FHSV), was synthesized via an amidation reaction and characterized by ¹H-NMR. Then, PTX-loaded FHSV micelles (PTX/FHSV) were prepared by a dialysis method. The physiochemical properties of the micelles were explored. Moreover, in vitro cytological experiments and in vivo animal studies were carried out to evaluate the antitumor efficacy of polymeric micelles.

Results

The PTX/FHSV micelles exhibited a uniform, near-spherical morphology (148.8 ± 1.4 nm) and a high drug loading capacity (11.28% ± 0.25). Triggered by the high concentration of glutathione, PTX/FHSV micelles could quickly release their loaded drug into the release medium. The in vitro cytological evaluations showed that, compared with Taxol or single receptor-targeted micelles, FHSV micelles yielded higher cellular uptake by the dual receptor-mediated endocytosis pathway, thus leading to significantly superior cytotoxicity and apoptosis in tumor cells but less cytotoxicity in normal cells. More importantly, in the in vivo antitumor experiments, PTX/FHSV micelles exhibited enhanced tumor accumulation and produced remarkable tumor growth inhibition with minimal systemic toxicity.

Conclusion

Our results suggest that this well-designed FHSV polymer has promising potential for use as a vehicle of chemotherapeutic drugs for precise cancer therapy.