Acidity-responsive shell-sheddable camptothecin-based nanofibers for carrier-free cancer drug delivery

Supramolecular self-assembled peptide-engineered nanofibers: A propitious proposition for cancer therapy

Cancer is a devastating disease that causes a substantial number of deaths worldwide. Current therapeutic interventions for cancer include chemotherapy, radiation therapy, or surgery. These conventional therapeutic approaches are associated with disadvantages such as multidrug resistance, destruction of healthy tissues, and tissue toxicity. Therefore, there is a paradigm shift in cancer management wherein nanomedicine-based novel therapeutic interventions are being explored to overcome the aforementioned disadvantages. Supramolecular self-assembled peptide nanofibers are emerging drug delivery vehicles that have gained much attention in cancer management owing to their biocompatibility, biodegradability, biomimetic property, stimuli-responsiveness, transformability, and inherent therapeutic property. Supramolecules form well-organized structures via non-covalent linkages, the intricate molecular arrangement helps to improve tissue permeation, pharmacokinetic profile and chemical stability of therapeutic agents while enabling targeted delivery and allowing efficient tumor imaging. In this review, we present fundamental aspects of peptide-based self-assembled nanofiber fabrication their applications in monotherapy/combinatorial chemo- and/or immuno-therapy to overcome multi-drug resistance. The role of self-assembled structures in targeted/stimuli-responsive (pH, enzyme and photo-responsive) drug delivery has been discussed along with the case studies. Further, recent advancements in peptide nanofibers in cancer diagnosis, imaging, gene therapy, and immune therapy along with regulatory obstacles towards clinical translation have been deliberated.

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.

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.

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.

Carrier-free nanoplatforms from natural plants for enhanced bioactivity

BACKGROUND

Natural plants as well as traditional Chinese medicine have made outstanding contributions to the health and reproduction of human beings and remain the basis and major resource for drug innovation. Carrier-free nanoplatforms completely self-assembled by pure molecules or therapeutic components have attracted increasing attention due to their advantages of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug loading. In recent years, carrier-free nanoplatforms produced by self-assembly from natural plants have contributed to progress in a variety of therapeutic modalities. Notably, these nanoplatforms based on the interactions of components from different natural plants improve efficiency and depress toxicity.

AIM OF REVIEW

In this review, different types of self-assembled nanoplatforms are first summarized, mainly including nanoassemblies of pure small molecules isolated from different plants, extracellular vesicles separated from fresh plants, charcoal nanocomponents obtained from charred plants, and nanoaggregates from plants formulae decoctions. Key Scientific Concepts of Review: We mainly focus on composition, self-assembly mechanisms, biological activity and modes of action. Finally, a future perspective of existing challenges with respect to the clinical application of plant-based carrier-free nanoplatforms is discussed, which may be instructive to further develop effective carrier-free nanoplatforms from natural plants in the future.

The role of imaging in targeted delivery of nanomedicine for cancer therapy

Nanomedicines overcome the pharmacokinetic limitations of traditional drug formulations and have promising prospect in cancer treatment. However, nanomedicine delivery in vivo is still facing challenges from the complex physiological environment. For the purpose of effective tumor therapy, they should be designed to guarantee the five features principle, including long blood circulation, efficient tumor accumulation, deep matrix penetration, enhanced cell internalization and accurate drug release. To ensure the excellent performance of the designed nanomedicine, it would be better to monitor the drug delivery process as well as the therapeutic effects by real-time imaging. In this review, we summarize strategies in developing nanomedicines for efficiently meeting the five features of drug delivery, and the role of several imaging modalities (fluorescent imaging (FL), magnetic resonance imaging (MRI), computed tomography (CT), photoacoustic imaging (PAI), positron emission tomography (PET), and electron microscopy) in tracing drug delivery and therapeutic effect in vivo based on five features principle.

Strategies to improve the EPR effect: A mechanistic perspective and clinical translation

Many efforts have been made to achieve targeted delivery of anticancer drugs to enhance their efficacy and to reduce their adverse effects. These efforts include the development of nanomedicines as they can selectively penetrate through tumor blood vessels through the enhanced permeability and retention (EPR) effect. The EPR effect was first proposed by Maeda and co-workers in 1986, and since then various types of nanoparticles have been developed to take advantage of the phenomenon with regards to drug delivery. However, the EPR effect has been found to be highly variable and thus unreliable due to the complex tumor microenvironment. Various physical and pharmacological strategies have been explored to overcome this challenge. Here, we review key advances and emerging concepts of such EPR-enhancing strategies. Furthermore, we analyze 723 clinical trials of nanoparticles with EPR enhancers and discuss their clinical translation.

Carrier-free nanodrugs with efficient drug delivery and release for cancer therapy: From intrinsic physicochemical properties to external modification

The considerable development of carrier-free nanodrugs has been achieved due to their high drug-loading capability, simple preparation method, and offering "all-in-one" functional platform features. However, the native defects of carrier-free nanodrugs limit their delivery and release behavior throughout the in vivo journey, which significantly compromise the therapeutic efficacy and hinder their further development in cancer treatment. In this review, we summarized and discussed the recent strategies to enhance drug delivery and release of carrier-free nanodrugs for improved cancer therapy, including optimizing the intrinsic physicochemical properties and external modification. Finally, the corresponding challenges that carrier-free nanodrugs faced are discussed and the future perspectives for its application are presented. We hope this review will provide constructive information for the rational design of more effective carrier-free nanodrugs to advance therapeutic treatment.

Delivering more for less: nanosized, minimal-carrier and pharmacoactive drug delivery systems

Traditional nanoparticle carriers such as liposomes, micelles, and polymeric vehicles improve drug delivery by protecting, stabilizing, and increasing the circulatory half-life of the encapsulated drugs. However, traditional drug delivery systems frequently suffer from poor drug loading and require an excess of carrier materials. This carrier material excess poses an additional systemic burden through accumulation, if not degradable the need for metabolism, and potential toxicity. To address these shortcomings, minimal-carrier nanoparticle systems and pharmacoactive carrier materials have been developed. Both solutions provide drug delivery systems in which the majority of the nanoparticle is pharmacologically active. While minimal-carrier and pharmacoactive drug delivery systems can improve drug loading, they can also suffer from poor stability. Here, we review minimal-carrier and pharmacoactive delivery systems, discuss ongoing challenges and outline opportunities to translate minimal-carrier and pharmacoactive drug delivery systems into the clinic.

A review on allopathic and herbal nanofibrous drug delivery vehicles for cancer treatments

Drug delivery empowered with nanotechnology manifests to be a superior therapy to cancer. Electrospun nanofibers cocooning anti-cancerous drugs have shown tremendous cytotoxicity towards various tumor cells, including breast, brain, liver, and lung cancer cells. This pristine drug delivery system, according to literature, desists showing any undesirable effects on other parts of the body and bestows several other benefits. From nature-derived Curcumin to laboratory-made Doxorubicin, literature proclaims many such drugs used in nanofibrous drug delivery. Also, multi-drug delivery has been reported to exhibit enhanced properties. The present review exhibits the unrealized potential of nanofibrous drug delivery in chemotherapy.

Self-delivery oxidative stress amplifier for chemotherapy sensitized immunotherapy

Amplifying oxidative stress to break intracellular redox homeostasis could accelerate tumor cell death. In this work, a self-delivery oxidative stress amplifier is developed for chemotherapy sensitized immunotherapy. By virtue of the π-π stacking and coordination effect, copper ions (Cu2+), doxorubicin (DOX) and NLG919 are able to self-assembly into the nanosized oxidative stress amplifier (designated as Cu-DON) with a favorable stability and a biocompatibility. Intravenously administrated Cu-DON could effectively accumulate and penetrate into tumor tissues for cellular uptake. Subsequently, the GSH-responsive DOX release will initiate the immunogenic chemotherapy (IC) for primary tumor inhibition. Moreover, Cu2+-mediated GSH consumption and DOX-triggered oxidative stress could cause the intracellular redox imbalance, contributing to immunogenic cell death (ICD) response. Further, the concomitant release of NLG919 would inhibit indoleamine 2,3-dioxygenase 1 (IDO-1) to reverse immunosuppressive tumor microenvironment (ITM) for enhanced immunotherapy. Consequently, this self-delivery oxidative stress amplifier greatly restrains the growth of primary, distant as well as rechallenged tumors by chemotherapy sensitized immunotherapy, which would shed light on the development of combination therapy to block tumor growth and metastasis in clinic.

Fabrication of versatile targeted lipopolymersomes for improved camptothecin efficacy against colon adenocarcinoma in vitro and in vivo

BACKGROUND

Hybrid vesicular systems (lipopolymersomes) are promising platforms for minimizing the liposomes and polymersomes disadvantages in terms of chemotherapeutic transportation. In this regard, lipopolymersome has been designed to integrate the advantage of both polymersomes and liposomes to enable better structural integrity of the bilayer after encapsulation of hydrophobic drugs while maintaining the soft nature of liposomes, superior serum stability, and high encapsulation efficiency of cargos in the bilayer segment.

RESEARCH DESIGN AND METHODS

In the present study, we reported preparation and characterization of five camptothecin (CPT)-loaded lipopolymersomal formulations composed of poly (ethylene glycol)-poly (lactic acid) (PEG-PLA) and dipalmitoylphosphatidylcholine (DPPC) at different molar ratios using film rehydration method. Afterward, the preferred formulation was tagged with AS1411 DNA aptamer in order to evaluate the therapeutic index using nucleolin-positive colon cancer cell lines (HT29 and C26).

RESULTS

The obtained data indicated that the prepared CPT-loaded lipopolymersome at a PEG-PLA: DPPC ratio of 75:25 exhibited superior stability and high loading capacity compared to other systems. Moreover, high cytotoxicity of the aptamer-targeted lipopolymersome and increased tumor accumulation were observed in comparison with non-targeted one.

CONCLUSIONS

The designed polymer-rich lipopolymersomal platform offers bright future for the development of potent nanomedicine against cancer.

Elongated self-assembled nanocarriers: From molecular organization to therapeutic applications

Self-assembled cylindrical aggregates made of amphiphilic molecules emerged almost 40 years ago. Due to their length up to micrometers, those particles display original physico-chemical properties such as important flexibility and, for concentrated samples, a high viscoelasticity making them suitable for a wide range of industrial applications. However, a quarter of century was needed to successfully take advantage of those improvements towards therapeutic purposes. Since then, a wide diversity of biocompatible materials such as polymers, lipids or peptides, have been developed to design self-assembling elongated drug nanocarriers, suitable for therapeutic or diagnostic applications. More recently, the investigation of the main forces driving the unidirectional growth of these nanodevices allowed a translation toward the formation of pure nanodrugs to avoid the use of unnecessary side materials and the possible toxicity concerns associated.

Photosensitizer-driven nanoassemblies of homodimeric prodrug for self-enhancing activation and synergistic chemo-photodynamic therapy

Carrier-free prodrug-nanoassemblies have emerged as promising nanomedicines. In particular, the self-assembled nanoparticles (NPs) composed of homodimeric prodrugs with ultrahigh drug loading have attracted broad attention. However, most homodimeric prodrugs show poor self-assembly ability due to their symmetric structures. Herein, we developed photosensitizer-driven nanoassemblies of homodimeric prodrug for self-enhancing activation and chemo-photodynamic synergistic therapy.

Methods: In this work, a pyropheophorbide a (PPa)-driven nanoassemblies of an oxidation-responsive cabazitaxel homodimer (CTX-S-CTX) was fabricated (pCTX-S-CTX/PPa NPs). The assembly mechanisms, aggregation-caused quenching (ACQ) effect alleviation, singlet oxygen generation, self-enhancing prodrug activation, cellular uptake, intracellular reactive oxygen species (ROS) generation and synergistic cytotoxicity of pCTX-S-CTX/PPa NPs were investigated in vitro. Moreover, the pharmacokinetics, ex vivo biodistribution and in vivo therapeutic efficacy of pCTX-S-CTX/PPa NPs were studied in mice bearing 4T1 tumor.

Results: Interestingly, PPa was found to drive the assembly of CTX-S-CTX, which cannot self-assemble into stable NPs alone. Multiple intermolecular forces were found to be involved in the assembly process. Notably, the nanostructure was destroyed in the presence of endogenous ROS, significantly relieving the ACQ effect of PPa. In turn, ROS generated by PPa under laser irradiation together with the endogenous ROS synergistically promoted prodrug activation. As expected, the nanoassemblies demonstrated potent antitumor activity in a 4T1 breast cancer BALB/c mice xenograft model.

Conclusion: Our findings offer a simple strategy to facilitate the assembly of homodimeric prodrugs and provide an efficient nanoplatform for chemo-photodynamic therapy.

Adaptive Mechanisms of Tumor Therapy Resistance Driven by Tumor Microenvironment

Cancer is a disease which frequently has a poor prognosis. Although multiple therapeutic strategies have been developed for various cancers, including chemotherapy, radiotherapy, and immunotherapy, resistance to these treatments frequently impedes the clinical outcomes. Besides the active resistance driven by genetic and epigenetic alterations in tumor cells, the tumor microenvironment (TME) has also been reported to be a crucial regulator in tumorigenesis, progression, and resistance. Here, we propose that the adaptive mechanisms of tumor resistance are closely connected with the TME rather than depending on non-cell-autonomous changes in response to clinical treatment. Although the comprehensive understanding of adaptive mechanisms driven by the TME need further investigation to fully elucidate the mechanisms of tumor therapeutic resistance, many clinical treatments targeting the TME have been successful. In this review, we report on recent advances concerning the molecular events and important factors involved in the TME, particularly focusing on the contributions of the TME to adaptive resistance, and provide insights into potential therapeutic methods or translational medicine targeting the TME to overcome resistance to therapy in clinical treatment.

Self-Delivery Photo-Immune Stimulators for Photodynamic Sensitized Tumor Immunotherapy

Self-delivery of photosensitizer and immune modulator to tumor site is highly recommendable to improve the photodynamic immunotherapy yet remains challenging. Herein, self-delivery photoimmune stimulators (designated as iPSs) are developed for photodynamic sensitized tumor immunotherapy. Carrier-free iPSs are constructed by optimizing the noncovalent interactions between the pure drugs of chlorine e6 (Ce6) and NLG919, which avoid the excipients-raised toxicity and immunogenicity. Intravenously administrated iPSs prefer to passively accumulate on tumor tissues for a robust photodynamic therapy (PDT) with the induction of immunogenetic cell death (ICD) cascade to activate cytotoxic T lymphocytes (CTLs) and initiate antitumor immune response. Meanwhile, the concomitant delivery of NLG919 inhibits the activation of indoleamine 2,3-dioxygenase 1 (IDO-1) to reverse the immunosuppressive tumor microenvironment. Ultimately, the photodynamic sensitized immunotherapy with iPSs efficiently inhibit the primary and distant tumor growth with a low system toxicity, which would shed light on the development of self-delivery nanomedicine for clinical transformation in tumor precision therapy.

Progress in Natural Compounds/siRNA Co-delivery Employing Nanovehicles for Cancer Therapy

Chemotherapy using natural compounds, such as resveratrol, curcumin, paclitaxel, docetaxel, etoposide, doxorubicin, and camptothecin, is of importance in cancer therapy because of the outstanding therapeutic activity and multitargeting capability of these compounds. However, poor solubility and bioavailability of natural compounds have limited their efficacy in cancer therapy. To circumvent this hurdle, nanocarriers have been designed to improve the antitumor activity of the aforementioned compounds. Nevertheless, cancer treatment is still a challenge, demanding novel strategies. It is well-known that a combination of natural products and gene therapy is advantageous over monotherapy. Delivery of multiple therapeutic agents/small interfering RNA (siRNA) as a potent gene-editing tool in cancer therapy can maximize the synergistic effects against tumor cells. In the present review, co-delivery of natural compounds/siRNA using nanovehicles are highlighted to provide a backdrop for future research.

Micro/nanoscale magnetic robots for biomedical applications

Magnetic small-scale robots are devices of great potential for the biomedical field because of the several benefits of this method of actuation. Recent work on the development of these devices has seen tremendous innovation and refinement toward ​improved performance for potential clinical applications. This review briefly details recent advancements in small-scale robots used for biomedical applications, covering their design, fabrication, applications, and demonstration of ability, and identifies the gap in studies and the difficulties that have persisted in the optimization of the use of these devices. In addition, alternative biomedical applications are also suggested for some of the technologies that show potential for other functions. This study concludes that although the field of small-scale robot research is highly innovative ​there is need for more concerted efforts to improve functionality and reliability of these devices particularly in clinical applications. Finally, further suggestions are made toward ​the achievement of commercialization for these devices.

Nuclear delivery of dual anticancer drug-based nanomedicine constructed by cisplatinum-induced peptide self-assembly

Nuclear delivery of anticancer drugs, particularly dual complementary anticancer drugs, can significantly improve chemotherapy efficacy. However, successful examples are rare. We reported a novel dual anticancer drug-based nanomedicine with nuclear accumulation properties. The nanomedicine was formed by chelation between a drug peptide amphiphile Rh-GFFYERGD (Rh represents Rhein, 1,8-dihydroxy-3-carboxy anthraquinonea) and cisplatinum (Pt). A single molecule of the drug peptide amphiphile could chelate up to 8 equiv. of cisplatinum in the resulting nanofibers. The nanofibers with a 1 : 4 ratio of Rh-GFFYERGD to cisplatinum demonstrated remarkable cellular uptake, and more significantly, superior nuclear accumulation properties. Additionally, the nanofibers could also bind to the DNA molecule more efficiently than those formed by the drug peptide amphiphile. Thus the nanofibers exhibited excellent anticancer properties both in vitro and in vivo. We envision a significant therapeutic potential of the dual anticancer drug-based nanomedicine with cisplatinum in cancer.

Lactosylated IR820/DOX Co-Assembled Nanodrug for Synergetic Antitumour Therapy

Introduction

Synergistic treatment integrating photothermal therapy (PTT) and chemotherapy is a promising strategy for hepatocellular carcinoma (HCC). However, the most commonly used photothermal agent, IR820, and chemotherapeutic drug, doxorubicin hydrochloride (DOX), are both hydrophilic molecules that suffer from the drawbacks of a short circulation time, rapid elimination and off-target effects.

Methods and Results

Herein, a novel nanodrug that combined HCC-targeted IR820 and DOX was developed based on excipient-free co-assembly. First, lactosylated IR820 (LA-IR820) was designed to target HCC. Then, the LA-IR820/DOX nanodrug (LA-IR820/DOX ND) was purely self-assembled without excipient assistance. The physicochemical properties and the chemo-photothermal antitumour activity of the excipient-free LA-IR820/DOX ND were evaluated. More importantly, the obtained LA-IR820/DOX ND exhibited 100% drug loading, remarkable HCC targeting and excellent antitumour efficacy.

Conclusion

This excipient-free LA-IR820/DOX ND may be a promising candidate for the synchronous delivery and synergistic targeting of IR820 and DOX as a combined chemo-photothermal therapy.