Esterase-Activated Charge-Reversal Polymer for Fibroblast-Exempt Cancer Gene Therapy

Tumor-Microenvironment-Responsive Nanomedicine for Enhanced Cancer Immunotherapy

The past decades have witnessed great progress in cancer immunotherapy, which has profoundly revolutionized oncology, whereas low patient response rates and potential immune-related adverse events remain major clinical challenges. With the advantages of controlled delivery and modular flexibility, cancer nanomedicine has offered opportunities to strengthen antitumor immune responses and to sensitize tumor to immunotherapy. Furthermore, tumor-microenvironment (TME)-responsive nanomedicine has been demonstrated to achieve specific and localized amplification of the immune response in tumor tissue in a safe and effective manner, increasing patient response rates to immunotherapy and reducing the immune-related side effects simultaneously. Here, the recent progress of TME-responsive nanomedicine for cancer immunotherapy is summarized, which responds to the signals in the TME, such as weak acidity, reductive environment, high-level reactive oxygen species, hypoxia, overexpressed enzymes, and high-level adenosine triphosphate. Moreover, the potential to combine nanomedicine-based therapy and immunotherapeutic strategies to overcome each step of the cancer-immunity cycle and to enhance antitumor effects is discussed. Finally, existing challenges and further perspectives in this rising field with the hope for improved development of clinical applications are discussed.

Highly Effective Crosslinker for Redox-Sensitive Gene Carriers

Polyethyleneimine (PEI) has been extensively used as a common gene carrier due to its high gene transfection efficiency. PEI1.8k shows significantly lower cytotoxicity than its high molecular weight counterparts. However, it also has the problem of low gene transfection efficiency. To address the dilemma, a highly effective crosslinker (DTME) was synthesized to react with PEI1.8k to obtain CS-PEI1.8k. The reaction showed several advantages, such as a fast process in room temperature within nine hours with the product which can directly complex with DNA after removing the solvent. The ability of CS-PEI1.8k to agglomerate with DNA was proven by particle size, zeta potential, and gel retardation assays. The cytotoxic in vitro transfection ability and cell internalization capacity of CS-PEI1.8k were tested to verify the transfection capacity of CS-PEI1.8k. Moreover, we also studied the mechanism of the relatively high level of gene transfection by this binary complex compared with PEI25k.

Systematic Combination of Oligonucleotides and Synthetic Polymers for Advanced Therapeutic Applications

The potential of oligonucleotides is exceptional in therapeutics because of their high safety, potency, and specificity compared to conventional therapeutic agents. However, many obstacles, such as low in vivo stability and poor cellular uptake, have hampered their clinical success. Use of polymeric carriers can be an effective approach for overcoming the biological barriers and thereby maximizing the therapeutic efficacy of the oligonucleotides due to the availability of highly tunable synthesis and functional modification of various polymers. As loaded in the polymeric carriers, the therapeutic oligonucleotides, such as antisense oligonucleotides, small interfering RNAs, microRNAs, and even messenger RNAs, become nuclease-resistant by bypassing renal filtration and can be efficiently internalized into disease cells. In this review, we introduced a variety of systematic combinations between the therapeutic oligonucleotides and the synthetic polymers, including the uses of highly functionalized polymers responding to a wide range of endogenous and exogenous stimuli for spatiotemporal control of oligonucleotide release. We also presented intriguing characteristics of oligonucleotides suitable for targeted therapy and immunotherapy, which can be fully supported by versatile polymeric carriers.

Prodrug nanoparticles rationally integrating stroma modification and chemotherapy to treat metastatic pancreatic cancer

Accumulating evidence suggests that stromal modifications improve chemotherapeutic outcomes in pancreatic ductal adenocarcinoma (PDAC). However, combination regimens of stroma-modifying agents and small-molecule cytotoxic drugs have achieved only limited improvements in the clinic, probably due to unsatisfactory pharmacokinetic profiles and restricted drug distribution in tumors. Here, we developed self-assembled prodrug nanoparticles integrating a stromal reprogramming inducer, calcipotriol (CAL), and a potent chemotherapeutic agent, 7-Ethyl-10-hydroxycamptothecin (SN38), to treat PDAC. While SN38 is conjugated to the block polymer backbone, CAL is loaded into the inner hydrophobic space during polymer self-assembly into nanoparticles. To achieve an efficient drug co-package, a planar and hydrophobic cholesterol domain was introduced to stabilize the hydrophobic CAL. Notably, the blood circulation time of CAL significantly improved as CAL|SN38 nanoparticle (CAL|SN38 NP). In addition, CAL|SN38 NP treatment significantly decreased the expression of N-cadherin, collagen, and fibronectin in tumors, which play critical roles in PDAC metastasis. Potent inhibition of primary tumor growth and vigorous anti-metastasis effects were observed after systemic administration of CAL|SN38 NP to stroma-rich PDAC orthotopic tumor-bearing mice. These findings provide a promising paradigm for developing tailor-made nanoparticles with potent stroma-modification capability to combat metastatic cancer.

Coordinating External and Built-In Triggers for Tunable Degradation of Polymeric Nanoparticles via Cycle Amplification

The selective activation of nanovectors in pathological tissues is of crucial importance to achieve optimized therapeutic outcomes. However, conventional stimuli-responsive nanovectors lack sufficient sensitivity because of the slight difference between pathological and normal tissues. To this end, the development of nanovectors capable of responding to weak pathological stimuli is of increasing interest. Herein, we report the fabrication of amphiphilic polyurethane nanoparticles containing both external and built-in triggers. The activation of external triggers leads to the liberation of highly reactive primary amines, which subsequently activates the built-in triggers with the release of more primary amines in a positive feedback manner, thereby triggering the degradation of micellar nanoparticles in a cycle amplification model. The generality and versatility of the cycle amplification concept have been successfully verified using three different triggers including reductive milieu, light irradiation, and esterase. We demonstrate that these stimuli-responsive nanoparticles show self-propagating degradation performance even in the presence of trace amounts of external stimuli. Moreover, we confirm that the esterase-responsive nanoparticles can discriminate cancer cells from normal ones by amplifying the esterase stimulus that is overexpressed in cancer cells, thereby enabling the selective release of encapsulated payloads and killing cancer cells. This work presents a robust strategy to fabricate stimuli-responsive nanocarriers with highly sensitive property toward external stimuli, showing promising applications in cancer therapy with minimized side effects.

The facile formation of hierarchical mesoporous silica nanocarriers for tumor-selective multimodal theranostics

The combination of therapeutic and diagnostic functions in a single platform has aroused great interest due to the more optimal synergistic effects that can be obtained as compared to any single theranostic approach alone. However, current nanotheranostics are normally formed via complicated construction steps involving the pre-synthesis of each component and further conjugation via chemical bonds, which may cause low integration efficiency and limit production and applications. Herein, a tumor-targeting and tumor-responsive all-in-one nanoplatform based on mesoporous silica nanocarriers (MSNs) was fabricated via a facile approach utilizing efficient and nondestructive physical interactions for long-wavelength fluorescence imaging-guided synergistic chemo-catalytic-photothermal tumor therapy. The MSNs were endowed with these multimodal theranostics via a simple hydrothermal method after coordinating with Fe2+ and glutathione (GSH) to introduce ferroferric oxide and carbon dots in situ. The former acts as a photothermal agent and catalytic agent to generate local heat under 808 nm irradiation and also when toxic hydroxyl radicals (˙OH) are in contact with abundant hydrogen peroxide in cancer cells, while the latter participates in fluorescence imaging. After loading with paclitaxel (PTX), polyester and folic-acid-conjugated cyclodextrin were employed to serve as an esterase-sensitive gatekeeper controlling PTX release from the MSN pores and as a tumor-targeting agent for accurate therapy, respectively. As expected, the nanoplatform was efficiently taken up by tumor cells over healthy cells, and then, synergetic chemo-catalytic-photothermal therapy was performed, resulting in 5-fold greater apoptosis of tumor cells as compared to healthy cells under 808 nm irradiation. Moreover, in vivo data from tumor-bearing mouse models showed that tumors were significantly inhibited, and the survival rates of these mice increased to greater than 80% after 5 weeks of treatment with our nanoplatform. These therapeutic processes could be directly tracked via fluorescence imaging enabled by carbon dots and, therefore, our nanoplatform provides a promising theranostics approach for tumor treatment.

Traceable Nano-Biohybrid Complexes by One-Step Synthesis as CRISPR-Chem Vectors for Neurodegenerative Diseases Synergistic Treatment

Abnormal protein aggregations are essential pathological features of neurodegenerative diseases. Eliminating while inhibiting the regeneration of these protein aggregates is considered an effective treatment strategy. Herein, the CRISPR/Cas9 gene-editing tool is employed to inhibit the regeneration of disease-related proteins, while chemical drugs are applied to eliminate the proteins that are produced. To efficiently deliver CRISPR-chem drugs into brain lesions, traceable nano-biohybrid complexes (F-TBIO) are constructed by one-step synthesis and CRISPR/Cas9 plasmids (CF-TBIO) are loaded in a controllable manner. CF-TBIO can knock out the BACE1 gene and reduce the burden of amyloid-β, and thereby significantly improve the cognitive abilities of 2xTg-AD mice. In particular, by prolonging the dosing interval, the pathological damage and behavioral abilities of 2xTg-AD mice are still significantly improved. During the therapeutic process, CF-TBIO with a high relaxation rate provides accurate imaging signals in the complex brain physiological environment. The finding shows that CF-TBIO has great potential to serve as a CRISPR-chem drug-delivery platform for neurodegenerative diseases therapy.

Charge-Conversion Strategies for Nucleic Acid Delivery

Nucleic acids are now considered as one of the most potent therapeutic modalities, as their roles go beyond storing genetic information and chemical energy or as signal transducer. Attenuation or expression of desired genes through nucleic acids have profound implications in gene therapy, gene editing and even in vaccine development for immunomodulation. Although nucleic acid therapeutics bring in overwhelming possibilities towards the development of molecular medicines, there are significant loopholes in designing and effective translation of these drugs into the clinic. One of the major pitfalls lies in the traditional design concepts for nucleic acid drug carriers, viz. cationic charge induced cytotoxicity in delivery pathway. Targeting this bottleneck, several pioneering research efforts have been devoted to design innovative carriers through charge-conversion approaches, whereby built-in functionalities convert from cationic to neutral or anionic, or even from anionic to cationic enabling the carrier to overcome several critical barriers for therapeutics delivery, such as serum deactivation, instability in circulation, low transfection and poor endosomal escape. This review will critically analyze various molecular designs of charge-converting nanocarriers in a classified approach for the successful delivery of nucleic acids. Accompanied by the narrative on recent clinical nucleic acid candidates, the review concludes with a discussion on the pitfalls and scope of these interesting approaches.

Endogenous Enzyme-responsive Nanoplatforms for Anti-tumor Therapy

The emergency of responsive drug delivery systems has contributed to reduced cytotoxicity, improved permeability in tissues and extended circulation time of the active drug. In particular, enzyme-responsive nanoplatforms have attracted a lot of attention due to the specificity and efficiency of an enzyme-catalyzed reaction. In this review, enzyme-based mono responsive drug delivery systems designed in the past 5 years have been summarized. These drug delivery systems were introduced by different tumor-related enzymes such as matrix metalloproteinase, esterase, hyaluronidase, caspase and cathepsin. Moreover, the enzyme-sensitive nanoplatforms activated by dual-stimuli have been also described. Although great progress had been made in the past years, the translation into clinical practice is still difficult. Thus, three obstacles (enzyme heterogeneity, reaction environment, animal model) were also discussed. In short, enzyme-activated drug delivery systems offer great potential in treating cancers.

Dose-Independent Transfection of Hydrophobized Polyplexes

Cationic polymers dynamically complex DNA into complexes (polyplexes). So, upon dilution, polyplexes easily dissociate and lose transfection ability, limiting their in vivo systemic gene delivery. Herein, it is found that polyplex's stability and endocytosis pathway determine its transfection dose-dependence. The polyplexes of hydrophilic polycations have dose-dependent integrity and lysosome-trafficking endocytosis; at low doses, most of these polyplexes dissociate, and the remaining few are internalized and trapped in lysosomes, abolishing their transfection ability. In contrast, the polyplexes of the polycations with optimal hydrophobicity remain integrated even at low concentrations and enter cells via macropinocytosis directly into the cytosol evading lysosomes, so each polyplex can accomplish its infection process, leading to dose-independent DNA transfection like viral vectors. Furthermore, the tuned hydrophobicity balancing the affinity of anionic poly(γ-glutamic acid) (γ-PGA) to the polyplex surface enables γ-PGA to stick on the polyplex surface as a shielding layer but peel off on the cell membrane to release the naked polyplexes for dose-independent transfection. These findings may provide guidelines for developing polyplexes that mimick a viral vector's dose-independent transfection for effective in vivo gene delivery.

Recent progress on charge-reversal polymeric nanocarriers for cancer treatments

Nanocarriers (NCs) for delivery anticancer therapeutics have been under development for decades. Although great progress has been achieved, the clinic translation is still in the infancy. The key challenge lies in the biological barriers which lie between the NCs and the target spots, including blood circulation, tumor penetration, cellular uptake, endo-/lysosomal escape, intracellular therapeutics release and organelle targeting. Each barrier has its own distinctive microenvironment and requires different surface charge. To address this challenge, charge-reversal polymeric NCs have been a hot topic, which are capable of overcoming each delivery barrier, by reversing their charges in response to certain biological stimuli in the tumor microenvironment. In this review, the triggering mechanisms of charge reversal, including pH, enzyme and redox approaches are summarized. Then the corresponding design principles of charge-reversal NCs for each delivery barrier are discussed. More importantly, the limitations and future prospects of charge-reversal NCs in clinical applications are proposed.

Bacterium-mimicking sequentially targeted therapeutic nanocomplexes based on O-carboxymethyl chitosan and their cooperative therapy by dual-modality light manipulation

An integrated gene nanovector capable of overcoming complicated physiological barriers in one vector is desirable to circumvent the challenges imposed by the intricate tumor microenvironment. Herein, a nuclear localization signals (NLS)-decorated element and an iRGD-functionalized element based on O-carboxymethyl chitosan were synthesized, mixed, and coated onto PEI/DNA to fabricate bacterium-mimicking sequentially targeted therapeutic nanocomplexes (STNPs) which were internalized through receptor-mediated endocytosis and other pathways and achieved nuclear translocation of DNA. The endo/lysosomal membrane disruption triggered by reactive oxygen species (ROS) after short-time illumination, together with the DNA nuclear translocation, evoked an enhanced gene expression. Alternatively, the excessive ROS from long-time irradiation induced apoptosis in tumor cells, bringing about greater anti-tumor efficacy owing to the integration of gene and photodynamic therapy. Overall, these results demonstrated bacterium-mimicking STNPs could be a potential candidate for tumor treatments.

Polymeric nano-carriers for on-demand delivery of genes via specific responses to stimuli

Polymeric nano-carriers have been developed as a most capable and feasible technology platform for gene therapy. As vehicles, polymeric nano-carriers are obliged to possess high gene loading capability, low immunogenicity, safety, and the ability to transfer various genetic materials into specific sites of target cells to express therapeutic proteins or block a process of gene expression. To this end, various types of polymeric nano-carriers have been prepared to release genes in response to stimuli such as pH, redox, enzymes, light and temperature. These stimulus-responsive nano-carriers exhibit high gene transfection efficiency and low cytotoxicity. In particular, dual- and multi-stimulus-responsive polymeric nano-carriers can respond to a combination of signals. Markedly, these combined responses take place either simultaneously or in a sequential manner. These dual-stimulus-responsive polymeric nano-carriers can control gene delivery with high gene transfection both in vitro and in vivo. In this review paper, we highlight the recent exciting developments in stimulus-responsive polymeric nano-carriers for gene delivery applications.

"Sweet tooth"-oriented SN38 prodrug delivery nanoplatform for targeted gastric cancer therapy

Most cancer cells employ overexpression of glucose transports (GLUTs) to satisfy glucose demand ("Sweet Tooth") for increased aerobic glycolysis rates. GLUT1, one of the most widely expressed GLUTs in numerous cancers, was identified as a prognosis-related biomarker of gastric cancer via tissue array analysis. Herein, a "Sweet Tooth"-oriented SN38 prodrug delivery nanoplatform (Glu-SNP) was developed for targeted gastric cancer therapy. For this purpose, a SN38-derived prodrug (PLA-SN38) was synthesized by tethering 7-ethyl-10-hydroxycamptothecin (SN38) to biocompatible polylactic acid (PLA) with the appropriate degree of polymerization (n = 44). The PLA-SN38 conjugate was further assembled with glycosylated amphiphilic lipid to obtain glucosamine-decorated nanoparticles (Glu-SNP). Glu-SNP exhibited potent antitumor efficiency both in vitro and in vivo through enhanced cancer cell-specific targeting associated with the overexpression of GLUT1, which provides a promising approach for gastric cancer therapy.

Prodrug Nanomedicine Inhibits Chemotherapy-Induced Proliferative Burst by Altering the Deleterious Intercellular Communication

Chemotherapy is one of the most commonly used clinical antitumor strategies. However, the therapy-induced proliferative burst, which always accompanies drug resistance and metastasis, has become a major obstacle during treatment. Except for some endogenous cellular or genetic mechanisms and some microenvironmental selection pressures, the intercellular connections in the tumor microenvironment (TME) are also thought to be the driving force for the acquired drug resistance and proliferative burst. Even though some pathway inhibitors or cell exempting strategies could be applied to partially avoid these unwanted communications, the complexity of the TME and the limited knowledge about those unknown detrimental connections might greatly compromise the efforts. Therefore, a more broad-spectrum strategy is urgently needed to relieve the drug-induced burst proliferation during various treatments. In this article, based on the possible discrepancies in metabolic activity between cells with different growth rates, several ester-bond-based prodrugs were synthesized. After screening, 7-ethyl-10-hyodroxycamptothecin-based prodrug nanoparticles were found to efficiently overcome the paclitaxel resistance, to selectively act on the malignantly proliferated drug-resistant cells and, furthermore, to greatly diminish the proliferative effect of common cytotoxic agents by blocking the detrimental intercellular connections. With the discriminating ability against malignant proliferating cells, the as-prepared prodrug nanomedicine exhibited significant anticancer efficacy against both drug-sensitive and drug-resistant tumor models, either by itself or by combining with highly potent nonselective chemotherapeutics. This work provides a different perspective and a possible solution for the treatment of therapy-induced burst proliferation.

Prodrug-based self-assembled nanoparticles formed by 3′,5′-dioleoyl floxuridine for cancer chemotherapy

Amphiphilic prodrug molecules (3′,5′-dioleoyl floxuridine, DOF) were constructed to form prodrug nanoparticles (DOF NPs) through a self-assembly process in water. The DOF NPs were easily prepared, relatively stable, and displayed improved anti-tumor activity.

Tumor-Associated Macrophage and Tumor-Cell Dually Transfecting Polyplexes for Efficient Interleukin-12 Cancer Gene Therapy

Interleukin 12 (IL12) is a potent pro-inflammatory chemokine with multifunction, including promoting cytotoxic T-cell-mediated killing of cancer cells. IL12-based cancer gene therapy can overcome IL12's life-threatening adverse effects, but its clinical translation has been limited by the lack of systemic gene-delivery vectors capable of efficiently transfecting tumors to produce sufficient local IL12. Macrophages inherently excrete IL12, and tumor-associated macrophages (TAMs) are the major tumor component taking up a large fraction of the vectors arriving in the tumor. It is thus hypothesized that a gene vector efficiently transfecting both cancer cells and TAMs would make the tumor to produce sufficient IL12; however, gene transfection of TAMs is challenging due to their inherent strong degradation ability. Herein, an IL12 gene-delivery vector is designed that efficiently transfects both cancer cells and TAMs to make them as a factory for IL12 production, which efficiently activates anticancer immune responses and remodels the tumor microenvironment, for instance, increasing the M1/M2 ratio by more than fourfold. Therefore, the intravenously administered vector retards tumor growth and doubles survival in three animal models' with negligible systemic toxicities. This work reports the first nonviral IL12 gene delivery system that effectively makes use of both macrophages and tumor cells.

Esterase-Responsive Polypeptide Vesicles as Fast-Response and Sustained-Release Nanocompartments for Fibroblast-Exempt Drug Delivery

Enzyme-responsive polypeptide vesicles have attracted considerable attention for precision theranostics because of their biocompatibility, biodegradability, and unique secondary conformation transition triggered by the catalytic actions of enzymes. These promising potentials of polypeptide vesicles could be limited in a drug delivery system by the very slow enzyme diffusion rate into vesicles that could reduce the efficacy of the drug. On the other hand, stimuli-responsive polymeric vesicles that respond to stimuli can undergo microstructure destruction for the burst release of drugs, which would penetrate through the membrane of dead cells and the tumor extracellular matrix, inducing acute toxicity to neighboring cells. Here, we designed amphiphilic PEG-polypeptide copolymers containing esterase-labile carbamate-caged primary amines. It was found that the diblock can self-assemble into vesicular structures. Esterase-triggered self-immolative decaging reactions could quickly release the primary amine moiety of monomers that can undergo an amidation reaction for transition of the bilayer of vesicles from hydrophobic to partially hydrophilic. This esterase-responsive process retains the nanostructure of vesicles but permeabilizes the vesicle membrane, which can afford the sustained release of encapsulating drugs. These esterase-responsive polypeptide vesicles mediate selective cytotoxicity in cancer cells with high esterase expression over normal fibroblasts with low esterase, enabling the potent anticancer chemotherapy with minimized side effects.

Designing Enzyme-responsive Biomaterials

Enzymes are a class of protein that catalyze a wide range of chemical reactions, including the cleavage of specific peptide bonds. They are expressed in all cell types, play vital roles in tissue development and homeostasis, and in many diseases, such as cancer. Enzymatic activity is tightly controlled through the use of inactive pro-enzymes, endogenous inhibitors and spatial localization. Since the presence of specific enzymes is often correlated with biological processes, and these proteins can directly modify biomolecules, they are an ideal biological input for cell-responsive biomaterials. These materials include both natural and synthetic polymers, cross-linked hydrogels and self-assembled peptide nanostructures. Within these systems enzymatic activity has been used to induce biodegradation, release therapeutic agents and for disease diagnosis. As technological advancements increase our ability to quantify the expression and nanoscale organization of proteins in cells and tissues, as well as the synthesis of increasingly complex and well-defined biomaterials, enzyme-responsive biomaterials are poised to play vital roles in the future of biomedicine.

Functional Self-Assembled DNA Nanohydrogels for Specific Telomerase Activity Imaging and Telomerase-Activated Antitumor Gene Therapy

Engineering a functional nanoplatform that integrates dynamic monitoring of endogenous biomarkers and a stimuli-activated therapeutic mode is promising for early diagnosis and treatment of cancers. In this study, we developed an intelligent DNA nanohydrogel with specific targeting capability that can be stimuli-activated for both in vitro telomerase detection and in vivo telomerase-triggered gene therapy. The DNA nanohydrogel was formed simply by the self-assembly of two Y-shaped DNA units and a double-stranded DNA linker labeled with fluorophores and loaded with therapeutic siRNA. When intracellular telomerase was overexpressed, the DNA nanohydrogel collapsed owing to the prolongation of the telomeric primer at the terminal sequence of one of the Y-shaped DNA units. As a result, the quenched fluorescence due to fluorescence resonance energy transfer (FRET) of the DNA nanohydrogel recovered and the trapped siRNA was released, enabling the accurate detection and imaging of intracellular telomerase activity as well as effective gene therapy of tumors. Benefiting from the great biocompatibility, specificity, and stimuli-responsive property, the developed DNA nanoplatform provides a new opportunity for precise cancer diagnosis and treatment as well as other biological applications.

Multicomponent Polymerization toward Cationic Polymers for Efficient Gene Delivery

A new class of cationic polymers containing tertiary amine, thioether, and hydroxyl groups are prepared via a catalyst-free, multicomponent polymerization method using dithiol, formaldehyde, and di-sec-amine with a ratio of 1:2:1, to access a library of water-soluble polymers with well-defined structures and suitable molecular weights (M_w ranging from 5000 to 8000 Da) in high yields (up to 90%). Such polycations are demonstrated to be promising nonviral gene delivery vectors with high transfection efficiency (up to 3.5-fold of PEI25k) and low toxicity with multiple functionalities: 1) efficient gene condensation by tertiary amine groups; 2) reactive oxygen species scavenging by thioether groups; and 3) positive charge shielding by hydroxyl groups. Both the thioether and hydroxyl groups are contributed to reduce the cytotoxicity of the polycations by tuning the oxidative stress and preventing the undesired serum binding. The optimized polycations can achieve high transfection efficiency under the serum conditions, indicating the great potential as a nonviral gene delivery vector candidate for clinical application.

Polyamidoamine Dendrimer Grafted with an Acid-Responsive Charge-Reversal Layer for Improved Gene Delivery

We report on a heterogeneous dendrimer (G3-acetal-NH₂) derivative possessing an acid-responsive charge-reversal layer. The synthesis of G3-acetal-NH₂ starts with a polyamidoamine (PAMAM) dendrimer G3 core and follows the aza-Michael addition with N-(2-(1-(allyloxy)ethoxy)ethyl)acrylamide synthesized by us and the thiol-ene click chemistry with cysteamine hydrochloride in sequence. In a weakly acidic environment, the surface of this newly formed dendrimer can turn from amine-terminated to hydroxyl-terminated due to the cleavage of the acetal groups. This charge conversion from 34.3 ± 2.7 to 18.0 ± 0.3 mV in 24 h at pH 5.3 enables its capacity as a gene delivery vehicle. G3-acetal-NH₂ with a positively charged surface can condense pMAX GFP plasmid at similar weight ratios as native G4-NH₂ (above 2:1), allowing for its protected uptake into cells and endosomal escape. Meanwhile, in the endosome, the drop in vesicle pH cleaves the acetal bond, releasing the genetic payload and limiting its recondensation by the reduction in the dendrimer surface charge. When the vector/plasmid weight ratio was 2:1, G3-acetal-NH₂ improved transfection of pMAX GFP plasmid by 5-fold over native G4-NH₂ in NIH3T3 cells in terms of GFP protein expression. Taken together, we show that this surface charge conversion performance makes the synthesized heterogeneous dendrimer an improved vehicle for gene transfection.

High-Fidelity End-Functionalization of Poly(ethylene glycol) Using Stable and Potent Carbamate Linkages

Commercial PEG-amine is of unreliable quality, and conventional PEG functionalization relies on esterification and etherification steps, suffering from incomplete conversion, harsh reaction conditions, and functional-group incompatibility. To solve these challenges, we propose an efficient strategy for PEG functionalization with carbamate linkages. By fine-tuning terminal amine basicity, stable and high-fidelity PEG-amine with carbamate linkage was obtained, as seen from the clean MALDI-TOF MS pattern. The carbamate strategy was further applied to the synthesis of high-fidelity multi-functionalized PEG with varying reactive groups. Compared to with an ester linkage, amphiphilic PEG-PS block copolymers bearing carbamate junction linkage exhibits preferential self-assembly tendency into vesicles. Moreover, nanoparticles of the latter demonstrate higher drug loading efficiency, encapsulation stability against enzymatic hydrolysis, and improved in vivo retention at the tumor region.

Doxifluridine-based pharmacosomes delivering miR-122 as tumor microenvironments-activated nanoplatforms for synergistic treatment of hepatocellular carcinoma

A novel kind of anti-cancer pharmacosome (named NPC-D) derived from Doxifluridine (5'-DFUR) was described, which could be activated by tumor microenvironments (TMEs). The NPC-D with H₂O₂-sensitive linker was dispersed well in water and simultaneously interacted with nucleic acids including plasmids encoding miR-122 (p122) and EpCAM-targeted aptamer (ap1) via charge interaction and hydrogen bonding. The integrated nanosystem (p122-ap1@NPC-D) was found to unleash by programmed TMEs (high level of H₂O₂ and low pH) to efficiently transfect miR-122 into MHCC-LM3 cells, followed by the releases of 5-FU. Besides, p122-ap1@NPC-D significantly countered the chemotherapy resistance and played a synergistic effect. These unique nanoparticles dramatically enhanced the anti-proliferation, and modulated the cellular apoptosis by the down-regulation of various signal pathways which imparted a bright application prospect in HCC treatment.

Harnessing the perinuclear actin cap (pnAC) to influence nanocarrier trafficking and gene transfection efficiency in skeletal myoblasts using nanopillars

Gene transfection is important in biotechnology and is used to modify cells intrinsically. It can be conducted in cell suspension or after cell adhesion, where the efficiency is dependent on many factors such as the type of nanocarrier used and cell division processes. Anchor-dependent cells are sensitive to the substrate they are attached to and adapt their behavior accordingly, including plasmid trafficking during gene transfection. Previously, it was shown in our group that the cytoskeleton is an essential factor in influencing gene transfection in skeletal myoblasts using nanogrooves as a substrate. In this study, the effect of the cytoskeleton on gene transfection efficiency of skeletal myoblasts was studied using various nanopillars and nanocarriers. Nanopillars with different diameters (200-1000 nm) and depths (200 or 400 nm) were fabricated using colloidal self-assembly and reactive ion etching. All surfaces were treated with oxygen plasma or polydopamine (PD) to further control cell morphology. Plasmid DNA was delivered into cells using jetPRIME or Lipofectamine 3000 nanocarriers. After screening hundreds of images, two distinguishable F-actin distributions were found, i.e., cells with or without a perinuclear actin cap (pnAC). Cells attached to nanopillars, especially the deep pillars, had a smaller spreading area, shorter F-actin, more 3D-like cell nuclei, and a lower percentage of pnAC, which lead to a higher gene transfection efficiency using jetPRIME. On the other hand, cells attached to the shallow nanopillars or flat surfaces had a larger spreading area, longer F-actin, more 2D-like cell nuclei, and a higher percentage of pnAC that facilitates gene transfection using Lipofectamine. The effects of cell density, cytoskeleton (cytoD), and focal adhesions (RGD) on gene transfection were also studied, and the results were consistent with our hypothesis that F-actin distribution is one of the critical factors in gene transfection. In conclusion, pnAC plays a vital role in the intracellular trafficking of nanocarrier/plasmid complexes and this study provides new insights into gene transfection in anchor-dependent cells. STATEMENT OF SIGNIFICANCE: This study provides a new perspective in gene transfection using attached cells where perinuclear actin cap (pnAC) is an essential factor involved in transfection efficiency. A series of nanopillars were used to harness cell and cytoskeleton morphology. Two distinguishable cytoskeletal structures were found including cells with or without pnAC. 2D-like cells with pnAC facilitate gene delivery using liposome-based nanocarriers, while 3D-like cells without pnAC benefit gene delivery using cationic polymer-based nanocarriers. This study reveals the importance of the cytoskeleton during gene transfection that is beneficial in tissue transfection.

Engineering Polymeric Prodrug Nanoplatform for Vaccination Immunotherapy of Cancer

Neoantigen-based cancer vaccines are promising for boosting cytotoxic T lymphocyte (CTL) responses. However, the therapeutic effect of cancer vaccines is severely blunted by functional suppression of the dendritic cells (DCs). Herein, we demonstrated an acid-responsive polymeric nanovaccine for activating the stimulator of interferon genes (STING) pathway and improving cancer immunotherapy. The nanovaccines were fabricated by integrating an acid-activatable polymeric conjugate of the STING agonist and neoantigen into one single nanoplatform. The nanovaccines efficiently accumulated at the lymph nodes for promoting DC uptake and facilitating cytosol release of the neoantigens. Meanwhile, the STING agonist activated the STING pathway in the DCs to elicit interferon-β secretion and to boost T-cell priming with the neoantigen. The nanovaccine dramatically inhibited tumor growth and occurrence of B16-OVA melanoma and 4T1 breast tumors in immunocompetent mouse models. Combination immunotherapy with the nanovaccines and anti-PD-L1 antibody demonstrated further improved antitumor efficacy in a 4T1 breast tumor model.

NIR light-triggered nanomaterials-based prodrug activation towards cancer therapy

Nanomaterials-based prodrug activation systems have been widely explored in cancer therapy, aiming at overcoming limited dosage formulation, systemic toxicity, and insufficient pharmacokinetic performance of parent drugs. For better delivery control, various stimuli systems, especially nanomaterials-based ones, have come to the forefront. Among them, near-infrared (NIR) light takes advantage of on-demand/site-specific regulation and non-invasiveness. In this review, we will address the developments of nanomaterials-based prodrug over the last decade, the activation mechanisms, and bioapplications under NIR light triggering. The advantages and limitations of NIR-triggered prodrug activation strategies and the perspectives of the next-generation prodrug nanomedicine will also be summarized. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Glutathione-Specific and Intracellularly Labile Polymeric Nanocarrier for Efficient and Safe Cancer Gene Delivery

Cationic polymers condense nucleic acids into nanosized complexes (polyplexes) that are widely explored for nonviral gene delivery, but their strong electrostatic binding with DNA causes inefficient intracellular gene release and translation and thereby unsatisfactory gene transfection efficiencies. Facilitated intracellular dissociation of polyplexes by making the polymer undergo positive-to-negative/neutral charge reversal can effectively solve these problems, but they must be sufficiently stable during the delivery. Herein, we report the first glutathione (GSH)-specific intracellular labile polyplexes for cancer-targeted gene delivery. The polymers are made from p-(2,4-dinitrophenyloxybenzyl)-ammonium cationic moieties, whose p-2,4-dinitrophenyl ether is cleaved specifically by GSH, rather than other biological thiols, triggering the conversion of the ammonium cation into the carboxylate anion and thus the fast intracellular DNA release of the polyplexes. Furthermore, the polyplexes coated with PEG-functionalized lipids are stable in biological fluids to gain long blood circulation for tumor accumulation. Thus, the efficient tumor accumulation and cell transfection of the polyplexes loaded with the tumor suicide gene tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) give rise to potent antitumor activity similar to that of the first-line chemotherapy drug paclitaxel but with much less adverse effects.

Core/Shell PEGS/HA Hybrid Nanoparticle Via Micelle-Coordinated Mineralization for Tumor-Specific Therapy

Nanomicelles, by virtue of their prominent biocompatibility, degradability, and ability to solubilize hydrophobic drugs, have been widely used as the most effective delivery platform for anticancer drugs. However, undesirable drug-loading capacity, unfeasible modification, poor in vivo stability, and intratumoral penetration remain to be addressed. Herein, we introduce a novel core/shell PEGylated poly(glycerol sebacate) (PEGS)/hydroxyapatite (HA) hybrid nanomicelle based on a unique triblock PEGS substrate with functional carboxyls in terminals and free hydroxyls as pendant groups. The hydrophobic doxorubicin (DOX) can be controllably encapsulated in the core of nanomicelles via hydrogen bonding, and ensuing in situ mineralization of HA occurs as a shell layer with the electrostatic effect between the carboxylate radical (COO^-) and calcium ion (Ca²⁺). Through optimizing the coordination of PEGS nanomicelles and HA mineralization, 20-30 nm spherical nanoparticles can be formed with considerable drug loading (0.38 mg DOX/1 mg nanoparticles) and a sensitive pH-responsive release (about 50% release amount at pH 5.6 while <5% release amount at pH 7.4 in 24 h). In further in vitro studies, this PEGS/HA hybrid nanoparticle system exhibits excellent selective tumor inhibitory efficacy, while in in vivo studies, high efficacy of tumor suppression and low incidence of toxicity can be evidenced in a DOX-loaded PEGS/HA group (71.7% decrease in average tumor volume compared to a control group after 15 day hypodermic treatment). The core/shell PEGS/HA nanoparticle coordinated with PEGS nanomicelles and in situ HA mineralization represents high drug-loading capacity, multifunctional possibility, and tumor-selective and responsive release profiles and could offer a highly promising platform for tumor therapy in clinical application.

Tumor extravasation and infiltration as barriers of nanomedicine for high efficacy: The current status and transcytosis strategy

Nanotechnology-based drug delivery platforms have been explored for cancer treatments and resulted in several nanomedicines in clinical uses and many in clinical trials. However, current nanomedicines have not met the expected clinical therapeutic efficacy. Thus, improving therapeutic efficacy is the foremost pressing task of nanomedicine research. An effective nanomedicine must overcome biological barriers to go through at least five steps to deliver an effective drug into the cytosol of all the cancer cells in a tumor. Of these barriers, nanomedicine extravasation into and infiltration throughout the tumor are the two main unsolved blockages. Up to now, almost all the nanomedicines are designed to rely on the high permeability of tumor blood vessels to extravasate into tumor interstitium, i.e., the enhanced permeability and retention (EPR) effect or so-called "passive tumor accumulation"; however, the EPR features are not so characteristic in human tumors as in the animal tumor models. Following extravasation, the large size nanomedicines are almost motionless in the densely packed tumor microenvironment, making them restricted in the periphery of tumor blood vessels rather than infiltrating in the tumors and thus inaccessible to the distal but highly malignant cells. Recently, we demonstrated using nanocarriers to induce transcytosis of endothelial and cancer cells to enable nanomedicines to actively extravasate into and infiltrate in solid tumors, which led to radically increased anticancer activity. In this perspective, we make a brief discussion about how active transcytosis can be employed to overcome the difficulties, as mentioned above, and solve the inherent extravasation and infiltration dilemmas of nanomedicines.

Size and charge dual-transformable mesoporous nanoassemblies for enhanced drug delivery and tumor penetration

A series of biological barriers in a nanoparticle-formulated drug delivery process inevitably result in the current low delivery efficiency, limited tumor penetration and insufficient cellular internalization of drugs. These multiple biological barriers are intimately related to the physicochemical properties of nanoparticles, especially the contradictory demand on size and surface charge for long blood circulation (larger and negative) and deep tumor penetration (smaller) as well as efficient cellular internalization (positive). Herein, we report tumor microenvironment triggered size and charge dual-transformable nanoassemblies. The nanoassembly is realized by immobilizing positive up/downconverting luminescent nanoparticles (U/DCNPs) onto large mesoporous silica nanoparticles (MSNs) via acid-labile bonds to form core@satellite structured MSN@U/DCNPs nanoassemblies, and subsequent capping of charge reversible polymers. At physiological pH, the integrated nanoassemblies with a larger size (∼180 nm) and negative charge can effectively achieve a prolonged blood circulation and high tumor accumulation. While under an acidic tumor microenvironment, the charge reversal of outer polymers and cleavage of linkers between MSNs and U/DCNPs can induce disintegration of the nanoassemblies into isolated MSNs and smaller U/DCNPs, both with a positively charged surface, which thereby potentiate the tumor penetration and cell uptake of dissociated nanoparticles. Combined with the independent near-infrared (NIR)-to-visible and NIR-to-NIR luminescence of U/DCNPs and high surface area of MSNs, the nanoassemblies can implement NIR bioimaging guided chemo- and photodynamic combined therapy with remarkable antitumor efficiency because of the high accumulation and deep tumor penetration induced by the dual transformability of the nanoassemblies.

Size and charge dual-transformable core@satellite structured nanoassemblies are developed to overcome multiple biological barriers in a drug delivery system.

Scar Tissue-Targeting Polymer Micelle for Spinal Cord Injury Treatment

Spinal cord injury (SCI) is a devastating disorder, leading to permanent motor and sensory deficit. Despite recent advances in neurosciences, the treatment efficacy on SCI patients remains unsatisfactory, mainly due to the poor accumulation, short retention, and lack of controlled release of therapeutics in lesion tissue. Herein, an injured spinal cord targeting prodrug polymer micelle is built. An esterase-responsive bond is used to link apocynin (APO) monomer, because of the enhanced esterase activity found in microglia cells after activation, which ensures a controlled degradation of APO prodrug (Allyloxypolyethyleneglycol-b-poly [2-(((4-acetyl-2-methoxyphenoxy)carbonyl)oxy)ethyl methacrylate], APEG-PAPO or PAPO) by activated microglia cells. A scar tissue-homing peptide (cysteine-alanine-glutamine-lysine, CAQK) is introduced to the PAPO to endow the polymer micelle the lesion tissue-targeting ability. As a result, this CAQK-modified prodrug micelle (cPAM) exhibits an improved accumulation and prolonged retention in lesion tissue compared to the control micelle. The cPAM also leads to superior tissue protection and sustained motor function recovery than the control groups in a mouse model of SCI. In conclusion, the cPAM induces an effective treatment of SCI by the lesion tissue specific delivery of the prodrug polymer via its robust scar binding effect, making the scar tissue a drug releasing platform for sustained treatment of SCI.

Self-assembly of paramagnetic amphiphilic copolymers for synergistic therapy

Theranostic nanoparticles composed of amphiphilic paramagnetic polymers are assembled for dual mode imaging and synergistic therapy.

Design and synthesis of a polyguanidium vector with enhanced DNA binding ability for effective gene delivery at a low N/P ratio

A polyguanidium polymer has extra affinity toward DNA and can mediate transfection efficiently at a low polymer to DNA ratio.

From single to a dual-gene delivery nanosystem: coordinated expression matters for boosting the neovascularization in vivo

A dual-gene delivery system with coordinated expression function boosted the neovascularization.

Longitudinal Visualization of Viable Cancer Cell Intratumoral Distribution in Mouse Models Using Oatp1a1-Enhanced Magnetic Resonance Imaging

OBJECTIVES

Multimodality reporter gene imaging provides valuable, noninvasive information on the fate of engineered cell populations. To complement magnetic resonance imaging (MRI) measures of tumor volume and 2-dimensional reporter-based optical measures of cell viability, reporter-based MRI may offer 3-dimensional information on the distribution of viable cancer cells in deep tissues.

MATERIALS AND METHODS

Here, we engineered human and murine triple-negative breast cancer cells with lentivirus encoding tdTomato and firefly luciferase for fluorescence imaging and bioluminescence imaging (BLI). A subset of these cells was additionally engineered with lentivirus encoding organic anion transporting polypeptide 1a1 (Oatp1a1) for MRI. Oatp1a1 operates by transporting gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) into cells, and it concomitantly improves BLI substrate uptake. After orthotopic implantation of engineered cells expressing or not expressing Oatp1a1, longitudinal fluorescence imaging, BLI, and 3-Tesla MRI were performed.

RESULTS

Oatp1a1-expressing tumors displayed significantly increased BLI signals relative to control tumors at all time points (P < 0.05). On MRI, post-Gd-EOB-DTPA T1-weighted images of Oatp1a1-expressing tumors exhibited significantly increased contrast-to-noise ratios compared with control tumors and precontrast images (P < 0.05). At endpoint, tumors expressing Oatp1a1 displayed intratumoral MR signal heterogeneity not present at earlier time points. Pixel-based analysis of matched in vivo MR and ex vivo fluorescence microscopy images revealed a strong, positive correlation between MR intensity and tdTomato intensity for Oatp1a1-expressing tumors (P < 0.05), but not control tumors.

CONCLUSIONS

These results characterize Oatp1a1 as a sensitive, quantitative, positive contrast MRI reporter gene for 3-dimensional assessment of viable cancer cell intratumoral distribution and concomitant BLI enhancement. This multimodality reporter gene system can provide new insights into the influence of viable cancer cell intratumoral distribution on tumor progression and metastasis, as well as improved assessments of anticancer therapies.

Application and design of esterase-responsive nanoparticles for cancer therapy

Nanoparticles have been developed for tumor treatment due to the enhanced permeability and retention effects. However, lack of specific cancer cells selectivity results in low delivery efficiency and undesired side effects. In that case, the stimuli-responsive nanoparticles system designed for the specific structure and physicochemical properties of tumors have attracted more and more attention of researchers. Esterase-responsive nanoparticle system is widely used due to the overexpressed esterase in tumor cells. For a rational designed esterase-responsive nanoparticle, ester bonds and nanoparticle structures are the key characters. In this review, we overviewed the design of esterase-responsive nanoparticles, including ester bonds design and nano-structure design, and analyzed the fitness of each design for different application. In the end, the outlook of esterase-responsive nanoparticle is looking forward.

TRAIL-based gene delivery and therapeutic strategies

TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), also known as APO2L, belongs to the tumor necrosis factor family. By binding to the death receptor 4 (DR4) or DR5, TRAIL induces apoptosis of tumor cells without causing side toxicity in normal tissues. In recent years TRAIL-based therapy has attracted great attention for its promise of serving as a cancer drug candidate. However, the treatment efficacy of TRAIL protein was under expectation in the clinical trials because of the short half-life and the resistance of cancer cells. TRAIL gene transfection can produce a "bystander effect" of tumor cell killing and provide a potential solution to TRAIL-based cancer therapy. In this review we focus on TRAIL gene therapy and various design strategies of TRAIL DNA delivery including non-viral vectors and cell-based TRAIL therapy. In order to sensitize the tumor cells to TRAIL-induced apoptosis, combination therapy of TRAIL DNA with other drugs by the codelivery methods for yielding a synergistic antitumor efficacy is summarized. The opportunities and challenges of TRAIL-based gene delivery and therapy are discussed.

Tumor-Associated Fibroblast-Targeted Regulation and Deep Tumor Delivery of Chemotherapeutic Drugs with a Multifunctional Size-Switchable Nanoparticle

Tumor-associated fibroblasts (TAFs), which form a predominant stromal cellular component of the tumor microenvironment, hinder the delivery of nanomedicine to deep tumor cells and lead to poor prognosis of tumors. However, depletion of TAFs by therapeutic agents results in the secretion of damage response program (DRP) molecules to weaken the efficacy of tumor treatment. This paper reports a multifunctional size-switchable nanoparticle (denoted DGL (dendrigraft poly-l-lysine) (DGL)/GEM@PP/GA) for TAF-targeted regulation and deep tumor penetration. After accumulation at the tumor site, in response to overexpressed matrix metalloproteinase-2 (MMP-2) in the tumor microenvironment, gemcitabine (GEM)-conjugated small nanoparticles (DGL/GEM) are released from DGL/GEM@PP/GA, leaving 18β-glycyrrhetinic acid (GA)-loaded large nanoparticles (PP/GA). The released DGL/GEM can penetrate to the deep region of the tumor as well as intracellularly release GEM to kill tumor cells. However, residual GA-loaded nanoparticles with lower tumor penetration ability could accumulate around tumor vessels and be preferentially absorbed by TAFs to regulate the secretion of Wnt 16, which is an important DRP molecule. By taking actions on both tumor cells and TAFs, DGL/GEM@PP/GA displayed significant and long-term antitumor effect in stroma-rich pancreatic cancer and breast cancer models.

Layered Double Hydroxide Nanoparticles for Efficient Gene Delivery for Cancer Treatment

The use of cationic polymer based gene delivery vectors has several limitations such as low transfection efficiency, high toxicity, and inactivation by serum. The present work provides an inorganic based nanocarrier for efficient gene delivery and a method for preparing the same through a facile coprecipitation technique. The vehicle showed high loading capacity of DNA and can release the loaded DNA in a controlled pH-responsive manner. The developed gene delivery vehicle offers remarkable protection against DNase I and also provides protection against thermal damage. This vehicle also demonstrated efficient cellular uptake performance. Transfection and expression of plasmid gene encoding GFP proteins is achieved successfully by this LDH based vehicle. More interestingly, the developed Li-Al LDH efficiently induces GFP-p53 mediated apoptosis in HeLa cells exclusively sparing the normal tissue cells like NIH-3T3. The study demonstrates the potential of the developed inorganic based nanocarrier as a promising nonviral gene vector for tumor treatment.

Glycyrrhizin Acid and Glycyrrhetinic Acid Modified Polyethyleneimine for Targeted DNA Delivery to Hepatocellular Carcinoma

In the last 2-3 decades, gene therapy represented a promising option for hepatocellular carcinoma (HCC) treatment. However, the design of safe and efficient gene delivery systems is still one of the major challenges that require solutions. In this study, we demonstrate a versatile method for covalent conjugation of glycyrrhizin acid (GL) or glycyrrhetinic acid (GA) to increase the transfection efficiency of Polyethyleneimine (PEI, Mw 1.8K) and improve their targeting abilities of hepatoma carcinoma cells. GA and GL targeting ligands were grafted to PEI via N-acylation, and we systematically investigated their biophysical properties, cytotoxicity, liver targeting and transfection efficiency, and endocytosis pathway trafficking. PEI-GA0.75, PEI-GL10.62 and PEI-GL20.65 conjugates caused significant increases in gene transfection efficiency and superior selectivity for HepG2 cells, with all three conjugates showing specific recognition of HepG2 cells by the free GA competition assay. The endocytosis inhibition and intracellular trafficking results indicated that PEI-GA0.75 and GL10.62 conjugates behaved similarly to SV40 virus, by proceeding via the caveolae- and clathrin-independent mediated endocytosis pathway and bypassing entry into lysosomes, with an energy independent manner, achieving their high transfection efficiencies. In the HepG2 intraperitoneal tumor model, PEI-GA0.75 and PEI-GL10.62 carrying the luciferase reporter gene gained high gene expression, suggesting potential use for in vivo application.