Biomimetic RNA‐Silencing Nanocomplexes: Overcoming Multidrug Resistance in Cancer Cells

RNA interference (RNAi) is an RNA‐dependent gene silencing approach controlled by an RNA‐induced silencing complex (RISC). Herein, we present a synthetic RISC‐mimic nanocomplex, which can actively cleave its target RNA in a sequence‐specific manner. With high enzymatic stability and efficient self‐delivery to target cells, the designed nanocomplex can selectively and potently induce gene silencing without cytokine activation. These nanocomplexes, which target multidrug resistance, are not only able to bypass the P‐glycoprotein (Pgp) transporter, due to their nano‐size effect, but also effectively suppress Pgp expression, thus resulting in successful restoration of drug sensitivity of OVCAR8/ADR cells to Pgp‐transportable cytotoxic agents. This nanocomplex approach has the potential for both functional genomics and cancer therapy.     

Engineering Multifunctional RNAi Nanomedicine To Concurrently Target Cancer Hallmarks for Combinatorial Therapy

Cancer hallmarks allow the complexity and heterogeneity of tumor biology to be better understood, leading to the discovery of various promising targets for cancer therapy. An amorphous iron oxide nanoparticle (NP)‐based RNAi strategy is developed to co‐target two cancer hallmarks. The NP technology can modulate the glycolysis pathway by silencing MCT4 to induce tumor cell acidosis, and concurrently exacerbate oxidative stress in tumor cells via the Fenton‐like reaction. This strategy has the following features for systemic siRNA delivery: 1) siRNA encapsulation within NPs for improving systemic stability; 2) effective endosomal escape through osmotic pressure and/or endosomal membrane oxidation; 3) small size for enhancing tumor tissue penetration; and 4) triple functions (RNAi, Fenton‐like reaction, and MRI) for combinatorial therapy and in vivo tracking.     

Tumor‐Microenvironment‐Induced Degradation of Ultrathin Gadolinium Oxide Nanoscrolls for Magnetic‐Resonance‐Imaging‐Monitored,Activatable Cancer Chemotherapy

The development of biodegradable inorganic nanoparticles with a tumor microenvironment‐activated therapeutic mode of action is urgently needed for precision cancer medicine. Herein, the synthesis of ultrathin lanthanide nanoscrolls (Gd₂O₃ NSs) is reported, which biodegrade upon encountering the tumor microenvironment. The Gd₂O₃ NSs showed highly controlled magnetic properties, which enabled their high‐resolution magnetic resonance imaging (MRI). Importantly, Gd₂O₃ NSs degrade in a pH‐responsive manner and selectively penetrate tumor tissue, enabling the targeted release of anti‐cancer drugs. Gd₂O₃ NSs can be efficiently loaded with an anti‐cancer drug (DOX, 80 %) and significantly inhibit tumor growth with negligible cellular and tissue toxicity both in vitro and in vivo. This study may provide a novel strategy to design tumor microenvironment‐responsive inorganic nanomaterials for biocompatible bioimaging and biodegradation‐enhanced cancer therapy.     

Hydrophobic Cysteine Poly(disulfide)‐based Redox‐Hypersensitive Nanoparticle Platform for Cancer Theranostics

Selective tumor targeting and drug delivery are critical for cancer treatment. Stimulus‐sensitive nanoparticle (NP) systems have been designed to specifically respond to significant abnormalities in the tumor microenvironment, which could dramatically improve therapeutic performance in terms of enhanced efficiency, targetability, and reduced side‐effects. We report the development of a novel L ‐cysteine‐based poly (disulfide amide) (Cys‐PDSA) family for fabricating redox‐triggered NPs, with high hydrophobic drug loading capacity (up to 25 wt % docetaxel) and tunable properties. The polymers are synthesized through one‐step rapid polycondensation of two nontoxic building blocks: L ‐cystine ester and versatile fatty diacids, which make the polymer redox responsive and give it a tunable polymer structure, respectively. Alterations to the diacid structure could rationally tune the physicochemical properties of the polymers and the corresponding NPs, leading to the control of NP size, hydrophobicity, degradation rate, redox response, and secondary self‐assembly after NP reductive dissociation. In vitro and in vivo results demonstrate these NPs’ excellent biocompatibility, high selectivity of redox‐triggered drug release, and significant anticancer performance. This system provides a promising strategy for advanced anticancer theranostic applications.     

Tumor‐Microenvironment‐Induced Degradation of Ultrathin Gadolinium Oxide Nanoscrolls for Magnetic‐Resonance‐Imaging‐Monitored,Activatable Cancer Chemotherapy

The development of biodegradable inorganic nanoparticles with a tumor microenvironment‐activated therapeutic mode of action is urgently needed for precision cancer medicine. Herein, the synthesis of ultrathin lanthanide nanoscrolls (Gd₂O₃ NSs) is reported, which biodegrade upon encountering the tumor microenvironment. The Gd₂O₃ NSs showed highly controlled magnetic properties, which enabled their high‐resolution magnetic resonance imaging (MRI). Importantly, Gd₂O₃ NSs degrade in a pH‐responsive manner and selectively penetrate tumor tissue, enabling the targeted release of anti‐cancer drugs. Gd₂O₃ NSs can be efficiently loaded with an anti‐cancer drug (DOX, 80 %) and significantly inhibit tumor growth with negligible cellular and tissue toxicity both in vitro and in vivo. This study may provide a novel strategy to design tumor microenvironment‐responsive inorganic nanomaterials for biocompatible bioimaging and biodegradation‐enhanced cancer therapy.     

Mussel‐Inspired Protein Nanoparticles Containing Iron(III)–DOPA Complexes for pH‐Responsive Drug Delivery

A novel bioinspired strategy for protein nanoparticle (NP) synthesis to achieve pH‐responsive drug release exploits the pH‐dependent changes in the coordination stoichiometry of iron(III)–3,4‐dihydroxyphenylalanine (DOPA) complexes, which play a major cross‐linking role in mussel byssal threads. Doxorubicin‐loaded polymeric NPs that are based on Fe^III–DOPA complexation were thus synthesized with a DOPA‐modified recombinant mussel adhesive protein through a co‐electrospraying process. The release of doxorubicin was found to be predominantly governed by a change in the structure of the Fe^III–DOPA complexes induced by an acidic pH value. It was also demonstrated that the fabricated NPs exhibited effective cytotoxicity towards cancer cells through efficient cellular uptake and cytosolic release. Therefore, it is anticipated that Fe^III–DOPA complexation can be successfully utilized as a new design principle for pH‐responsive NPs for diverse controlled drug‐delivery applications.     

Near‐Infrared Light and pH‐Responsive Polypyrrole@Polyacrylic acid/Fluorescent Mesoporous Silica Nanoparticles for Imaging and Chemo‐Photothermal Cancer Therapy

We have rationally designed a new theranostic agent by coating near‐infrared (NIR) light‐absorbing polypyrrole (PPY) with poly(acrylic acid) (PAA), in which PAA acts as a nanoreactor and template, followed by growing small fluorescent silica nanoparticles (fSiO₂ NPs) inside the PAA networks, resulting in the formation of polypyrrole@polyacrylic acid/fluorescent mesoporous silica (PPY@PAA/fmSiO₂) core–shell NPs. Meanwhile, DOX‐loaded PPY@PAA/fmSiO₂ NPs as pH and NIR dual‐sensitive drug delivery vehicles were employed for fluorescence imaging and chemo‐photothermal synergetic therapy in vitro and in vivo. The results demonstrate that the PPY@PAA/fmSiO₂ NPs show high in vivo tumor uptake by the enhanced permeability and retention (EPR) effect after intravenous injection as revealed by in vivo fluorescence imaging, which is very helpful for visualizing the location of the tumor. Moreover, the obtained NPs inhibit tumor growth (95.6 % of tumors were eliminated) because of the combination of chemo‐photothermal therapy, which offers a synergistically improved therapeutic outcome compared with the use of either therapy alone. Therefore, the present study provides new insights into developing NIR and pH‐stimuli responsive PPY‐based multifunctional platform for cancer theranostics.     

Acetazolamide‐Loaded pH‐Responsive Nanoparticles Alleviating Tumor Acidosis to Enhance Chemotherapy Effects

Carbonic anhydrase IX (CA IX), over‐expressed on cancer cells, catalyzes CO₂ to bicarbonate and protons, contributing to the acidic extracellular pH (pHe), which enhances the multidrug resistance of tumor cells. Therefore, alleviating tumor acidosis would greatly improve the outcome of chemotherapy. This work fabricates acetazolamide (ACE)‐loaded pH‐responsive nanoparticles (ACE‐NPs), which are quickly disintegrated in an acidic solution (pH 6.8), resulting in a quick release of ACE from these NPs to inhibit the expression of CA IX, thus up‐regulating the pHe value. These ACE‐NPs have no obvious in vitro cytotoxicity and in vivo studies confirm the accumulation of ACE‐NPs in tumor tissue. In addition, mice treated with ACE and paclitaxel (PTX) co‐loaded NPs show a smaller tumor size and a higher survival rate when compared to that of mice treated with ACE‐ or PTX‐loaded NPs. This work reveals that simultaneous delivery of ACE and chemotherapy agents to tumor tissue can up‐regulate the acidic pHe value, consequently enhancing the anti‐tumor ability of chemotherapy medicine. These findings open a new window for enhancing the anti‐tumor ability of traditional chemotherapy in clinic.     

Biodegradable Inorganic Nanovector: Passive versus Active Tumor Targeting in siRNA Transportation

The biodegradable inorganic nanovector based on a layered double hydroxide (LDH) holds great promise for gene and drug delivery systems. However, in vivo targeted delivery of genes through LDH still remains a key challenge in the development of RNA interference therapeutics. Here, we describe in vivo and in vitro delivery system for Survivin siRNA (siSurvivin) assembled with passive LDH with a particle size of 100 nm or active LDH conjugated with a cancer overexpressing receptor targeting ligand, folic acid (LDHFA), conferring them an ability to target the tumor by either EPR‐based clathrin‐mediated or folate receptor‐mediated endocytosis. When not only transfected into KB cells but also injected into xenograft mice, LDHFA/siSurvivin induced potent gene silencing at mRNA and protein levels in vitro, and consequently achieved a 3.0‐fold higher suppression of tumor volume than LDH/siSurvivin in vivo. This anti‐tumor effect was attributed to a selectively 1.2‐fold higher accumulation of siSurvivin in tumor tissue compared with other organs. Targeting to the tumor with inorganic nanovector can guide and accelerate an evolution of next‐generation theranosis system.     

DNAzyme‐Loaded Metal–Organic Frameworks (MOFs) for Self‐Sufficient Gene Therapy

DNAzymes have been recognized as potent therapeutic agents for gene therapy, while their inefficient intracellular delivery and insufficient cofactor supply precludes their practical biological applications. Metal–organic frameworks (MOFs) have emerged as promising drug carriers without in‐depth consideration of their disassembled ingredients. Herein, we report a self‐sufficient MOF‐based chlorin e6‐modified DNAzyme (Ce6‐DNAzyme) therapeutic nanosystem for combined gene therapy and photodynamic therapy (PDT). The ZIF‐8 nanoparticles (NPs) could efficiently deliver the therapeutic DNAzyme without degradation into cancer cells. The pH‐responsive ZIF‐8 NPs disassemble with the concomitant release of the guest DNAzyme payloads and the host Zn²⁺ ions that serve, respectively, as messenger RNA‐targeting agent and required DNAzyme cofactors for activating gene therapy. The auxiliary photosensitizer Ce6 could produce reactive oxygen species (ROS) and provide a fluorescence signal for the imaging‐guided gene therapy/PDT.     

Hypoxia‐Targeted siRNA Delivery

Altered vasculature and the resultant chaotic tumor blood flow lead to the appearance in fast‐growing tumors of regions with gradients of oxygen tension and acute hypoxia (less than 1.4 % oxygen). 1 Due to its roles in tumorigenesis and resistance to therapy, hypoxia represents a problem in cancer therapy. 1 , 2 Insufficient delivery of therapeutic agents to the hypoxic regions in solid tumors is recognized as one of the causes of resistance to therapy. 1 , 3 This led to the development of hypoxia imaging agents, 4 and the use of hypoxia‐activated anticancer prodrugs. 2a Here we show the first example of the hypoxia‐induced siRNA uptake and silencing using a nanocarrier consisting of polyethyleneglycol 2000, azobenzene, polyethyleneimine (PEI)(1.8 kDa), and 1,2‐dioleyl‐sn‐glycero‐3‐phosphoethanolamine (DOPE) units (the nanocarrier is referred to as PAPD), where azobenzene imparts hypoxia sensitivity and specificity. 4a We report hypoxia‐activated green fluorescent protein (GFP) silencing in vitro and its downregulation in GFP‐expressing tumors after intravenous administration. The proposed nanoformulation represents a novel tumor‐environment‐responsive modality for cancer targeting and siRNA delivery.     

H2S‐Activable MOF Nanoparticle Photosensitizer for Effective Photodynamic Therapy against Cancer with Controllable Singlet‐Oxygen Release

Photodynamic therapy (PDT) has emerged as an important minimally invasive tumor treatment technology. The search for an effective photosensitizer to realize selective cancer treatment has become one of the major foci in recent developments of PDT technology. Controllable singlet‐oxygen release based on specific cancer‐associated events, as another major layer of selectivity mode, has attracted great attention in recent years. Here, for the first time, we demonstrated that a novel mixed‐metal metal–organic framework nanoparticle (MOF NP) photosensitizer can be activated by a hydrogen sulfide (H₂S) signaling molecule in a specific tumor microenvironment for PDT against cancer with controllable singlet‐oxygen release in living cells. The effective removal of tumors in vivo further confirmed the satisfactory treatment effect of the MOF NP photosensitizer.     

Combinatorially inducible RNA interference triggered by chemically modified oligonucleotides

Chemically inducible RNA interference (RNAi) enables temporal and/or spatial control of virtually any gene, making it useful for study of gene functions, discovery of potential drug targets, and gene therapy applications. Here we describe a new inducible RNAi platform in which orthogonal chemically modified oligonucleotides are used to trigger silencing of two genes in a combinatorial manner. We developed a modular RNA architecture consisting of an oligonucleotide sensor stem-loop and an RNAi effector domain that is designed to undergo a structural shift upon addition of an oligonucleotide inducer. The induced structural change allows the RNA to be processed by the RNAi machinery, ultimately resulting in gene silencing of the target encoded by the RNAi effector module. Combinatorial regulation of multiple genes should accelerate studies of complex gene-gene interactions and screening of new drug targets.     

Tailored Synthesis of Octopus‐type Janus Nanoparticles for Synergistic Actively‐Targeted and Chemo‐Photothermal Therapy

A facile, reproducible, and scalable method was explored to construct uniform Au@poly(acrylic acid) (PAA) Janus nanoparticles (JNPs). The as‐prepared JNPs were used as templates to preferentially grow a mesoporous silica (mSiO₂) shell and Au branches separately modified with methoxy‐poly(ethylene glycol)‐thiol (PEG) to improve their stability, and lactobionic acid (LA) for tumor‐specific targeting. The obtained octopus‐type PEG‐Au‐PAA/mSiO₂‐LA Janus NPs (PEG‐OJNP‐LA) possess pH and NIR dual‐responsive release properties. Moreover, DOX‐loaded PEG‐OJNP‐LA, upon 808 nm NIR light irradiation, exhibit obviously higher toxicity at the cellular and animal levels compared with chemotherapy or photothermal therapy alone, indicating the PEG‐OJNP‐LA could be utilized as a multifunctional nanoplatform for in vitro and in vivo actively‐targeted and chemo‐photothermal cancer therapy.     

Model‐Based Nanoengineered Pharmacokinetics of Iron‐Doped Copper Oxide for Nanomedical Applications

The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. As low NM delivery rates limit therapeutic efficacy, an entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purposes (carrier and drug) with a direct chemical composition–biological functionality relationship. Model‐based dissolution kinetics of CuO NPs in the cellular interior at post‐exposure conditions were controlled through Fe‐doping for intra/extra cellular Cu²⁺ and biological outcome. Through controlled ion release and reactions taking place in the cellular interior, tumors could be treated selectively, in vitro and in vivo. Locally administered NPs enabled tumor cells apoptosis and stimulated systemic anti‐cancer immune responses. We clearly show therapeutic effects without tumor cells relapse post‐treatment with 6 % Fe‐doped CuO NPs combined with myeloid‐derived suppressor cell silencing.     

Multi‐Stimuli‐Responsive Polymeric Prodrug for Enhanced Cancer Treatment

Accomplishing efficient delivery of a nanomedicine to the tumor site will encounter two contradictions as follows: 1) a contradiction between prolonged circulation time and endocytosis by cancer cells; 2) a dilemma between the stability of nanomedicine during blood circulation and intracellular drug release. While developing a nanomedicine which can solve the above two contradictions simultaneously is still a challenge, here, a multi‐stimuli‐responsive polymeric prodrug (PLys‐co‐(PLys‐DA)‐co‐(PLys‐SS‐PTX))‐b‐PLGLAG‐mPEG (P‐PEP‐SS‐PTX‐DA) is synthesized which is multi‐sensitive to overexpressed matrix metalloproteinase‐2 (MMP‐2), low pH, and high concentration of glutathione in tumors. The P‐PEP‐SS‐PTX‐DA can be dePEGylated and reversed from negative at normal physiological pH to positive charge at tumor extracellular microenvironment; in this way, it can solve the contradiction between prolonged circulation time and endocytosis by cancer cells. Owing to the high reductive conditions in cancer cells, P‐PEP‐SS‐PTX‐DA is ruptured to release paclitaxel (PTX) intracellular efficiently; therefore, it can resolve the dilemma between the stability of nanomedicine during blood circulation and intracellular drug release. These indicate that the multi‐stimuli‐responsive polymeric prodrug has potential application prospects in drug delivery and cancer therapy.     

Chemically Synthesized,Self-Assembling Small Interfering RNA-Prohead RNA Molecules Trigger Dicer-Independent Gene Silencing

RNA interference (RNAi) mediated by small interfering RNA (siRNA) duplexes is a powerful therapeutic modality, but the translation of siRNAs from the bench into clinical application has been hampered by inefficient delivery in vivo. An innovative delivery strategy involves fusing siRNAs to a three-way junction (3WJ) motif derived from the phi29 bacteriophage prohead RNA (pRNA). Chimeric siRNA-3WJ molecules are presumed to enter the RNAi pathway through Dicer cleavage. Here, we fused siRNAs to the phi29 3WJ and two phylogenetically related 3WJs. We confirmed that the siRNA-3WJs are substrates for Dicer in vitro. However, our results reveal that siRNA-3WJs transfected into Dicer-deficient cell lines trigger potent gene silencing. Interestingly, siRNA-3WJs transfected into an Argonaute 2-deficient cell line also retain some gene silencing activity. siRNA-3WJs are most efficient when the antisense strand of the siRNA duplex is positioned 5′ of the 3WJ (5′-siRNA-3WJ) relative to 3′ of the 3WJ (3′-siRNA-3WJ). This work sheds light on the functional properties of siRNA-3WJs and offers a design rule for maximizing their potency in the human RNAi pathway.     

Microenvironment‐Induced In Situ Self‐Assembly of Polymer–Peptide Conjugates That Attack Solid Tumors Deeply

In cancer treatment, the unsatisfactory solid‐tumor penetration of nanomaterials limits their therapeutic efficacy. We employed an in vivo self‐assembly strategy and designed polymer–peptide conjugates (PPCs) that underwent an acid‐induced hydrophobicity increase with a narrow pH‐response range (from 7.4 to 6.5). In situ self‐assembly in the tumor microenvironment at appropriate molecular concentrations (around the IC₅₀ values of PPCs) enabled drug delivery deeper into the tumor. A cytotoxic peptide KLAK, decorated with the pH‐sensitive moiety cis‐aconitic anhydride (CAA), and a cell‐penetrating peptide TAT were conjugated onto poly(β‐thioester) backbones to produce PT‐K‐CAA, which can penetrate deeply into solid tumors owing to its small size as a single chain. During penetration in vivo, CAA responds to the weak acid, leading to the self‐assembly of PPCs and the recovery of therapeutic activity. Therefore, a deep‐penetration ability for enhanced cancer therapy is provided by this in vivo assembly strategy.     

Calcium Phosphate‐Reinforced Photosensitizer‐Loaded Polymer Nanoparticles for Photodynamic Therapy

Calcium phosphate‐reinforced photosensitizer‐loaded polymer nanoparticles have been developed for photodynamic therapy. Chlorin e6 (Ce6)‐loaded core–shell–corona polymer micelles of poly(ethylene glycol)‐b‐poly(L ‐aspartic acid)‐b‐poly(L ‐phenylalanine) ( PEG-PAsp-PPhe ) were employed as template nanoparticles for mineralization with calcium phosphate (CaP). CaP deposition was performed by the electrostatic localization of calcium ions at the anionic PAsp middle shells and the subsequent addition of phosphate anions. CaP‐reinforced nanoparticles exhibited enhanced stability. The CaP mineral layer effectively inhibited Ce6 release from the Ce6‐loaded mineralized nanoparticles (Ce6‐NP‐CaP) at physiological pH value. At an acidic endosomal pH value of 5.0, Ce6 release was enhanced, owing to rapid dissolution of the CaP minerals. Upon irradiation of Ce6‐NP‐CaP‐treated MCF‐7 breast‐tumor cells, the cell viability dramatically decreased with increasing irradiation time. The phototoxicity of Ce6‐NP‐CaP was much higher than that of free Ce6. Non‐invasive optical‐imaging results indicated that Ce6‐NP‐CaP exhibited enhanced tumor specificity compared with free Ce6 and Ce6‐loaded non‐mineralized polymer nanoparticles (Ce6‐NP).