Redox-responsive polymer inhibits macrophages uptake for effective intracellular gene delivery and enhanced cancer therapy

Tumor Microenvironment-Responsive Polymer-Based RNA Delivery Systems for Cancer Treatment

Ribonucleic acid (RNA) therapeutics offer a broad prospect in cancer treatment. However, their successful application requires overcoming various physiological barriers to effectively deliver RNAs to the target sites. Currently, a number of RNA delivery systems based on polymeric nanoparticles are developed to overcome these barriers in RNA delivery. This work provides an overview of the existing RNA therapeutics for cancer gene therapy, and particularly summarizes those that are entering the clinical phase. This work then discusses the core features and latest research developments of tumor microenvironment-responsive polymer-based RNA delivery carriers which are designed based on the pathological characteristics of the tumor microenvironment. Finally, this work also proposes opportunities for the transformation of RNA therapies into cancer immunotherapy methods in clinical applications.

Mitochondria targeted biomimetic platform for chemo/photodynamic combination therapy against osteosarcoma

Clinical treatment for osteosarcoma (OS) is still lacking effective means, and no significant progress in OS treatment have been made in recent years. Single chemotherapy has serious side effects and can produce drug resistance easily, resulting poor therapeutic effect. As a modern and non-invasive treatment form, photodynamic therapy (PDT) is widely used to treat diverse cancers. Chemotherapy in combination with PDT is a particularly efficient antitumor method that could overcome the defects of monotherapies. Since mitochondria is a key subcellular organelle involved in cell apoptosis regulation, targeting tumor cells mitochondria for drug delivery has become an important entry point for anti-tumor therapy. Herein, we rationally designed a core-shell structured biomimetic nanoplatform, i.e., D@SLNP@OSM-IR780, to achieve tumor homologous targeting and mitochondria targeted drug release for chemotherapy combined with PDT against OS. Upon 808 nm laser irradiation, D@SLNP@OSM-IR780 exhibited excellent photo-cytotoxicity in vitro. The excellent targeting effect of D@SLNP@OSM-IR780 in tumor tissues produced a tumor inhibition rate of 98.9% in vivo. We further indicated that synergistic chemo-photodynamic effect induced by D@SLNP@OSM-IR780 could activate mitochondria-mediated apoptosis pathway, along with host immune response and potential photothermal effect. On the whole, D@SLNP@OSM-IR780 is revealed to be a promising platform for OS targeted combination therapeutics.

Recent Advances in Micro- and Nano-Drug Delivery Systems Based on Natural and Synthetic Biomaterials

Polymeric drug delivery technology, which allows for medicinal ingredients to enter a cell more easily, has advanced considerably in recent decades. Innovative medication delivery strategies use biodegradable and bio-reducible polymers, and progress in the field has been accelerated by future possible research applications. Natural polymers utilized in polymeric drug delivery systems include arginine, chitosan, dextrin, polysaccharides, poly(glycolic acid), poly(lactic acid), and hyaluronic acid. Additionally, poly(2-hydroxyethyl methacrylate), poly(N-isopropyl acrylamide), poly(ethylenimine), dendritic polymers, biodegradable polymers, and bioabsorbable polymers as well as biomimetic and bio-related polymeric systems and drug-free macromolecular therapies have been employed in polymeric drug delivery. Different synthetic and natural biomaterials are in the clinical phase to mitigate different diseases. Drug delivery methods using natural and synthetic polymers are becoming increasingly common in the pharmaceutical industry, with biocompatible and bio-related copolymers and dendrimers having helped cure cancer as drug delivery systems. This review discusses all the above components and how, by combining synthetic and biological approaches, micro- and nano-drug delivery systems can result in revolutionary polymeric drug and gene delivery devices.

Current and emerging applications of saccharide-modified chitosan: a critical review

Chitin, as the main component of the exoskeleton of Arthropoda, is a highly available natural polymer that can be processed into various value-added products. Its most important derivative, i.e., chitosan, comprising β-1,4-linked 2-amino-2-deoxy-β-d-glucose (deacetylated d-glucosamine) and N-acetyl-d-glucosamine units, can be prepared via alkaline deacetylation process. Chitosan has been used as a biodegradable, biocompatible, non-antigenic, and nontoxic polymer in some in-vitro applications, but the recently found potentials of chitosan for in-vivo applications based on its biological activities, especially antimicrobial, antioxidant, and anticancer activities, have upgraded the chitosan roles in biomaterials. Chitosan approval, generally recognized as a safe compound by the United States Food and Drug Administration, has attracted much attention toward its possible applications in diverse fields, especially biomedicine and agriculture. Even with some favorable characteristics, the chitosan's structure should be customized for advanced applications, especially due to its drawbacks, such as low drug-load capacity, low solubility, high viscosity, lack of elastic properties, and pH sensitivity. In this context, derivatization with relatively inexpensive and highly available mono- and di-saccharides to soluble branched chitosan has been considered a "game changer". This review critically reviews the emerging technologies based on the synthesis and application of lactose- and galactose-modified chitosan as two important chitosan derivatives. Some characteristics of chitosan derivatives and biological activities have been detailed first to understand the value of these natural polymers. Second, the saccharide modification of chitosan has been discussed briefly. Finally, the applications of lactose- and galactose-modified chitosan have been scrutinized and compared to native chitosan to provide an insight into the current state-of-the research for stimulating new ideas with the potential of filling research gaps.

A Nanosized Codelivery System Based on Intracellular Stimuli-Triggered Dual-Drug Release for Multilevel Chemotherapy Amplification in Drug-Resistant Breast Cancer

Lacking nano-systems for precisely codelivering the chemotherapeutics paclitaxel (PTX) and the natural P-glycoprotein (P-gp) inhibitor, quercetin (QU), into cancer cells and controlling their intracellular release extremely decreased the anticancer effects in multidrug resistant (MDR) tumors. To overcome this hurdle, we constructed hybrid polymeric nanoparticles (PNPs) which consist of redox-sensitive PTX/polyethyleneimine-tocopherol hydrogen succinate-dithioglycollic acid PNPs and pH-sensitive hyaluronic acid-QU conjugates. The obtained hybrid PNPs can be internalized into drug-resistant breast cancer cells by the hyaluronic acid/CD44-mediated endocytosis pathway and escape from the lysosome through the “proton sponge effect”. Under the trigger of intracellular stimuli, the nanoplatform used the pH/glutathione dual-sensitive disassembly to release QU and PTX. The PTX diffused into microtubules to induce tumor cell apoptosis, while QU promoted PTX retention by down-regulating P-gp expression. Moreover, tocopherol hydrogen succinate and QU disturbed mitochondrial functions by generating excessive reactive oxygen species, decreasing the mitochondrial membrane potential, and releasing cytochrome c into the cytosol which consequently achieved intracellular multilevel chemotherapy amplification in MDR cancers. Importantly, the PNPs substantially suppressed tumors growth with an average volume 2.54-fold lower than that of the control group in the MCF-7/ADR tumor-bearing nude mice model. These presented PNPs would provide a valuable reference for the coadministration of natural compounds and anticarcinogens for satisfactory combination therapy in MDR cancers.

Dual ATP/reduction-responsive polyplex to achieve the co-delivery of doxorubicin and miR-23b for the cancer treatment

Combination therapy based on the co-delivery of therapeutic genes and anti-cancer drugs has emerged as a promising approach in the cancer treatment, and stimuli-responsive delivery systems could further improve the therapeutic efficacy. Herein, an ATP aptamer and its complementary DNA were used to form Duplex into which doxorubicin (DOX) was loaded to construct DOX-Duplex, and then the lipoic acid-modified oligoethyleneimine (LA-OEI) was employed as a carrier to realize the co-delivery of DOX-Duplex and miR-23b. The ternary nanocomplex LA-OEI/miR-23b/DOX-Duplex showed excellent anti-proliferative effect by inducing the cell apoptosis via mitochondrial signaling pathway and arresting the cell cycle at S phase. Meanwhile, the co-delivery of DOX-Duplex and miR-23b could efficiently inhibit the metastasis of cancer cells by reducing the expression level of MMP-9. The favorable anti-tumor efficacy of ternary nanocomplex was attributed to the rapid drug release in response to intracellular ATP concentration and reduction conditions and the synergistic effect between DOX-Duplex and miR-23b. Thus, ATP aptamer and reduction-responsive polymer provided a convenient platform to construct dual stimuli-responsive systems for the co-delivery of gene and drug in the cancer treatment.

Self-preparation system using glucose oxidase-inspired nitroreductase amplification for cascade-responsive drug release and multidrug resistance reversion

Early antitumor therapy is an important determinant of survival in patients with cancer. Utilization of specific pathological states, such as hypoxia, greatly promotes the development of intelligent drug delivery systems (DDSs) for targeted antitumor therapy. However, a slight decrease in oxygen levels in early-stage tumors is not sufficient to trigger hypoxia-responsive drug release. Nitroreductase (NTR) is overexpressed in bioreductive hypoxic cancers, and its expression level has been verified to be directly related to hypoxic status. Herein, using glucose oxidase (GOx) as an O₂-consuming agent to exacerbate hypoxia, a cascade strategy of GOx-induced overexpression of NTR and amplified NTR-catalyzed release was proposed for early antitumor therapy. Briefly, NTR-sensitive p-nitrobenzyl chloroformate (PNZ-Cl) was adopted to conjugate with the polysaccharide chitosan (CS) and self-assemble into CS-PNZ-Cl micelles. These polymer micelles possess the dual abilities to specifically immobilize GOx and load mitoxantrone (MIT) to form the NTR-responsive nanocascade reactor GOx/MIT@CS-PNZ-Cl. First, as a "key", tumor hypoxia triggers the initial release of GOx, which serves as the O₂-consuming agent when catalyzing its reaction with glucose, which is accompanied by H₂O₂ production. Depleted oxygen levels facilitate the expression of NTR, which in turn amplifies the capacity of the nanocascade reactor to decompose into secondary micelles for enhanced intratumoral permeation. GOx-inspired NTR amplification further elicits MIT release, realizing a synergistic "domino effect" cascade. In addition, upregulated H₂O₂ has been shown to effectively reverse GSH-mediated MIT resistance, reaching the superior tumor inhibition rate of 93.08%. This GOx-based NTR-responsive nanocascade reactor provides amplification of the bioreductive hypoxic tumor microenvironment for early antitumor therapy.

Evaluation of Chitosan Derivatives Modified Mesoporous Silica Nanoparticles as Delivery Carrier

Chitosan is a non-toxic biological material, but chitosan is insoluble in water, which hinders the development and utilization of chitosan. Chitosan derivatives N-2-Hydroxypropyl trimethyl ammonium chloride (N-2-HACC) and carboxymethyl chitosan (CMCS) with good water solubility were synthesized by our laboratory. In this study, we synthesized mesoporous SiO₂ nanoparticles by the emulsion, and then the mesoporous SiO₂ nanoparticles were modified with γ-aminopropyltriethoxysilane to synthesize aminated mesoporous SiO₂ nanoparticles; CMCS and N-2-HACC was used to cross-link the aminated mesoporous SiO₂ nanoparticles to construct SiO₂@CMCS-N-2-HACC nanoparticles. Because the aminated mesoporous SiO₂ nanoparticles with positively charged can react with the mucous membranes, the virus enters the body mainly through mucous membranes, so Newcastle disease virus (NDV) was selected as the model drug to evaluate the performance of the SiO₂@CMCS-N-2-HACC nanoparticles. We prepared the SiO₂@CMCS-N-2-HACC nanoparticles loaded with inactivated NDV (NDV/SiO₂@CMCS-N-2-HACC). The SiO₂@CMCS-N-2-HACC nanoparticles as delivery carrier had high loading capacity, low cytotoxicity, good acid resistance and bile resistance and enteric solubility, and the structure of NDV protein encapsulated in the nano vaccine was not destroyed. In addition, the SiO₂@CMCS-N-2-HACC nanoparticles could sustain slowly released NDV. Therefore, the SiO₂@CMCS-N-2-HACC nanoparticles have the potential to be served as delivery vehicle for vaccine and/or drug.

Hepatocyte-targeting and microenvironmentally responsive glycolipid-like polymer micelles for gene therapy of hepatitis B

Hepatitis B (HB) is a viral infectious disease that seriously endangers human health, and since there are no radical drugs to counter this, effective and safe therapies urgently need to be developed. HB virus (HBV) mainly infects hepatocytes (HCs), while the drugs are easily phagocytosed by Kupffer cells (KCs). In this study, the glutathione concentration difference between HCs and KCs was examined and utilized in an ideal drug-release strategy. Here, galactosylated chitosan-oligosaccharide-SS-octadecylamine (Gal-CSSO) was prepared to accurately deliver 10-23 DNAzyme DrzBC (blocking HBeAg expression) or DrzBS (blocking HBsAg expression) in targeted HB therapy. In vitro Gal-CSSO systems exhibited low cytotoxicity, endosomal escape, and glutathione responsiveness. The HBeAg and HBsAg secretion of HepG2.2.15 was significantly decreased by Gal-CSSO systems, and the maximum inhibition rates were 1.82-fold and 2.38-fold greater than those of commercial Lipofectamine 2000 (Lipo2000) systems. In vivo Gal-CSSO systems exhibited HC targeting and HC microenvironmental responsiveness without noticeable hepatotoxicity or systemic toxicity. The HBeAg and HBsAg titers of the HBV-infected mice were evidently decreased by Gal-CSSO systems, and the inhibition rates were 1.52-fold and 1.22-fold greater than those of Lipo2000 systems. This study presents a kind of glycolipid-like polymer micelles that promise efficient and safe gene therapy of HB.

Stimuli-Responsive Polymeric Nanocarriers for Drug Delivery, Imaging, and Theragnosis

In the past few decades, polymeric nanocarriers have been recognized as promising tools and have gained attention from researchers for their potential to efficiently deliver bioactive compounds, including drugs, proteins, genes, nucleic acids, etc., in pharmaceutical and biomedical applications. Remarkably, these polymeric nanocarriers could be further modified as stimuli-responsive systems based on the mechanism of triggered release, i.e., response to a specific stimulus, either endogenous (pH, enzymes, temperature, redox values, hypoxia, glucose levels) or exogenous (light, magnetism, ultrasound, electrical pulses) for the effective biodistribution and controlled release of drugs or genes at specific sites. Various nanoparticles (NPs) have been functionalized and used as templates for imaging systems in the form of metallic NPs, dendrimers, polymeric NPs, quantum dots, and liposomes. The use of polymeric nanocarriers for imaging and to deliver active compounds has attracted considerable interest in various cancer therapy fields. So-called smart nanopolymer systems are built to respond to certain stimuli such as temperature, pH, light intensity and wavelength, and electrical, magnetic and ultrasonic fields. Many imaging techniques have been explored including optical imaging, magnetic resonance imaging (MRI), nuclear imaging, ultrasound, photoacoustic imaging (PAI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). This review reports on the most recent developments in imaging methods by analyzing examples of smart nanopolymers that can be imaged using one or more imaging techniques. Unique features, including nontoxicity, water solubility, biocompatibility, and the presence of multiple functional groups, designate polymeric nanocues as attractive nanomedicine candidates. In this context, we summarize various classes of multifunctional, polymeric, nano-sized formulations such as liposomes, micelles, nanogels, and dendrimers.

siRNA and chemotherapeutic molecules entrapped into a redox-responsive platform for targeted synergistic combination therapy of glioma

Vascular endothelial growth factor (VEGF) has been implicated as the key regulator of tumor neovascularization. RNAi interference plays a critical role on down-regulation of VEGF, while single VEGF inhibition could not completely suppress angiogenesis and tumor growth; the effect of siRNA is temporary. To improve glioma therapy efficacy, an angiopep-2 (Ap) modified redox-responsive glycolipid-like copolymer co-delivering siVEGF and paclitaxel (PTX), termed as Ap-CSssSA/P/R complexes, was developed in this study. Ap modification significantly enhanced the distribution of Ap-CSssSA in glioma cells both in vitro and in vivo. Ap-CSssSA/P/R complexes could simultaneously deliver siVEGF and PTX into tumor cells, exhibiting great superiority in glioma growth suppression via receptor-mediated targeting delivery and cell apoptosis, accompanied with an obvious inhibition of neovascularization induced by VEGF gene silencing. The present study indicated that the combination delivery of siVEGF and PTX via Ap-modified copolymeric micelles presented a promising and safe platform for glioma targeted therapeutics.

Emerging Strategies in Stimuli-Responsive Nanocarriers as the Drug Delivery System for Enhanced Cancer Therapy

The conventional Drug Delivery System (DDS) has limitations such as leakage of the drug, toxicity to normal cells and loss of drug efficiency, while the stimuli-responsive DDS is non-toxic to cells, avoiding the leakage and degradation of the drug because of its targeted drug delivery to the pathological site. Thus nanomaterial chemistry enables - the development of smart stimuli-responsive DDS over the conventional DDS. Stimuliresponsive DDS ensures spatial or temporal, on-demand drug delivery to the targeted cancer cells. The DDS is engineered by using the organic (synthetic polymers, liposomes, peptides, aptamer, micelles, dendrimers) and inorganic (zinc oxide, gold, magnetic, quantum dots, metal oxides) materials. Principally, these nanocarriers release the drug at the targeted cells in response to external and internal stimuli such as temperature, light, ultrasound and magnetic field, pH value, redox potential (glutathione), and enzyme. The multi-stimuli responsive DDS is more promising than the single stimuli-responsive DDS in cancer therapy, and it extensively increases drug release and accumulation in the targeted cancer cells, resulting in better tumor cell ablation. In this regard, a handful of multi-stimuli responsive DDS is in clinical trials for further approval. A comprehensive review is crucial for addressing the existing knowledge about multi-stimuli responsive DDS, and hence, we summarized the emerging strategies in tailored ligand functionalized stimuli-responsive nanocarriers as the DDS for cancer therapies.

AKT activation by SC79 to transiently re-open pathological blood brain barrier for improved functionalized nanoparticles therapy of glioblastoma

Glioblastoma (GBM) is one of the malignant tumors with high mortality, and the presence of the blood brain barrier (BBB) severely limits the penetration and tissue accumulation of therapeutic agents in the lesion of GBM. Active targeting nanotechnologies can achieve efficient drug delivery in the brain, while still have a very low success rate. Here we revealed a previously unexplored phenomenon that chemotherapy with active targeting nanotechnologies causes pathological BBB functional recovery through VEGF-PI3K-AKT signaling pathway inhibition, accompanied with up-regulated expression of Claudin-5 and Occludin. Seriously, pathological BBB functional recovery induces a significant decrease of intracerebral active targeting nanotechnologies transport during GBM multiple administration, leading to chemotherapy failure in GBM therapeutics. To address this issue, we chose AKT agonist SC79 to transiently re-open functional recovering pathological BBB for continuously intracerebral delivery of brain targeted nanotherapeutics, finally producing an observable anti-GBM effect in vivo, which may offer new sight for other CNS disease treatment.

Chitosan Derivatives and Their Application in Biomedicine

Chitosan is a product of the deacetylation of chitin, which is widely found in nature. Chitosan is insoluble in water and most organic solvents, which seriously limits both its application scope and applicable fields. However, chitosan contains active functional groups that are liable to chemical reactions; thus, chitosan derivatives can be obtained through the chemical modification of chitosan. The modification of chitosan has been an important aspect of chitosan research, showing a better solubility, pH-sensitive targeting, an increased number of delivery systems, etc. This review summarizes the modification of chitosan by acylation, carboxylation, alkylation, and quaternization in order to improve the water solubility, pH sensitivity, and the targeting of chitosan derivatives. The applications of chitosan derivatives in the antibacterial, sustained slowly release, targeting, and delivery system fields are also described. Chitosan derivatives will have a large impact and show potential in biomedicine for the development of drugs in future.

Polycation Architecture and Assembly Direct Successful Gene Delivery: Micelleplexes Outperform Polyplexes via Optimal DNA Packaging

Cellular delivery of biomacromolecules is vital to medical research and therapeutic development. Cationic polymers are promising and affordable candidate vehicles for these precious payloads. However, the impact of polycation architecture and solution assembly on the biological mechanisms and efficacy of these vehicles has not been clearly defined. In this study, four polymers containing the same cationic poly(2-(dimethylamino)ethyl methacrylate) (D) block but placed in different architectures have been synthesized, characterized, and compared for cargo binding and biological performance. The D homopolymer and its diblock copolymer poly(ethylene glycol)-block-poly(2-(dimethylamino) ethyl methacrylate) (OD) readily encapsulate pDNA to form polyplexes. Two amphiphilic block polymer variants, poly(2-(dimethylamino)ethyl methacrylate)-block-poly(n-butyl methacrylate) (DB) and poly(ethylene glycol)-block-poly(2-(dimethylamino)ethyl methacrylate)-block-poly(n-butyl methacrylate) (ODB), self-assemble into micelles, which template pDNA winding around the cationic corona to form micelleplexes. Micelleplexes were found to have superior delivery efficiency compared to polyplexes and detailed physicochemical and biological characterizations were performed to pinpoint the mechanisms by testing hypotheses related to cellular internalization, intracellular trafficking, and pDNA unpackaging. For the first time, we find that the higher concentration of amines housed in micelleplexes stimulates both cellular internalization and potential endosomal escape, and the physical motif of pDNA winding into micelleplexes, reminiscent of DNA compaction by histones in chromatin, preserves the pDNA secondary structure in its native B form. This likely allows greater payload accessibility for protein expression with micelleplexes compared to polyplexes, which tightly condense pDNA and significantly distort its helicity. This work provides important guidance for the design of successful biomolecular delivery systems via optimizing the physicochemical properties.