Reduction-sensitive polymeric carrier for the targeted delivery of a quinazoline derivative for enhanced generation of reactive oxygen species against cancer

Hepatocellular carcinoma (HCC) is one of the deadliest malignant tumors and the development of effective therapeutics against HCC is urgently needed. A novel quinazoline derivative 04NB-03 (Qd04) has been proved to be highly effective against HCC without obvious toxic side-effects. However, the poor water solubility and low bioavailability in vivo severely limit its clinical application. In addition, Qd04 kills tumor cells by inducing an accumulation of endogenous reactive oxygen species (ROS), which is highly impeded by the overexpression of glutathione (GSH) in tumor cells. Herein, we designed a disulfide cross-linked polyamino acid micelle to deliver Qd04 for HCC therapy. The disulfide linkage not only endowed a tumor-targeted delivery of Qd04 by responding to tumor cell GSH but also depleted GSH to achieve increased levels of ROS generation, which improved the therapeutic efficiency of Qd04. Both in vitro and in vivo results demonstrated that the synthesized nanodrug exerted good anti-hepatoma effects, which provided a potential application for HCC therapy in clinics.

Cation-free siRNA-cored nanocapsules for tumor-targeted RNAi therapy

Cation-associated cytotoxicity limits the systemic administration of RNA delivery in vivo, demanding the development of non-cationic nanosystems. In this study, cation-free polymer-siRNA nanocapsules with disulfide-crosslinked interlayer, namely T-SS(-), were prepared via the following steps: 1) complexation of siRNA with a cationic block polymer cRGD-poly(ethylene glycol)-b-poly[(2-aminoethanethiol)aspartamide]-b-poly{N'-[N-(2-aminoethyl)-2-ethylimino-1-aminomethyl]aspartamide}, abbreviated as cRGD-PEG-PAsp(MEA)-PAsp(C=N-DETA), 2) interlayer crosslinking via disulfide bond in pH 7.4 solution, and 3) removal of cationic DETA pendant at pH 5.0 via breakage of imide bond. The cationic-free nanocapsules with siRNA cores not only showed great performance (such as efficient siRNA encapsulation, high stability in serum, cancer cell targeting via cRGD modification, and GSH-triggered siRNA release), but also achieved tumor-targeted gene silencing in vivo. Moreover, the nanocapsules loaded with siRNA against polo-like kinase 1 (siRNA-PLK1) significantly inhibited tumor growth without showing cation-associated toxicity side effects and remarkably improved the survival rate of PC-3 tumor-bearing mice. The cation-free nanocapsules could potentially serve as a safe and effective platform for siRNA delivery. STATEMENT OF SIGNIFICANCE: Cation-associated toxicity limits the clinical translation of cationic carriers for siRNA delivery. Recently, several non-cationic carriers, such as siRNA micelles, DNA-based nanogels, and bottlebrush-architectured poly(ethylene glycol), have been developed to deliver siRNA. However, in these designs, siRNA as a hydrophilic macromolecule was attached to the nanoparticle surface instead of being encapsulated. Thus, it was easily degraded by serum nuclease and often induced immunogenicity. Herein, we demonstrate a new type of cation-free siRNA-cored polymeric nanocapsules. The developed nanocapsules not only showed capacities including efficient siRNA encapsulation, high stability in serum, and cancer cell targeting via cRGD modification, but also achieved an efficient tumor-targeted gene silencing in vivo. Importantly, unlike cationic carriers, the nanocapsules exhibited no cation-associated side effects.

Unprotonatable and ROS-Sensitive Nanocarrier for NIR Spatially Activated siRNA Therapy with Synergistic Drug Effect

Although small interfering RNA (siRNA) therapy has achieved great progress, unwanted gene inhibition in normal tissues severely limits its extensive clinical applications due to uncontrolled siRNA biodistribution. Herein, a spatially controlled siRNA activation strategy is developed to achieve tumor-specific siRNA therapy without gene inhibition in the normal tissues. The quaternary ammonium moieties are conjugated to amphiphilic copolymers via reactive oxygen species (ROS)-sensitive thioketal (TK) linkers for co-delivery of siRNA and photosensitizer chlorin e6 (Ce6), showing excellent siRNA complexation capacity and near infrared (NIR)-controlled siRNA release. In the normal tissue, siRNAs are trapped and degraded in the endo-lysosomes due to the unprotonatable property of quaternary ammonium moiety, showing the siRNA activity "off" state. When NIR irradiation is spatially applied to the tumor tissue, the NIR irradiation/Ce6-induced ROS trigger siRNA endo-lysosomal escape and cytosolic release through the photochemical internalization effect and cleavage of TK bonds, respectively, showing the siRNA activity "on" state. The siRNA-mediated glutathione peroxidase 4 gene inhibition enhances ROS accumulation. The synergistic antitumor activity of Ce6 photodynamic therapy and gene inhibition is confirmed in vivo. Spatially controlled tumor-specific siRNA activation and co-delivery with Ce6 using unprotonatable and ROS-sensitive cationic nanocarriers provide a feasible strategy for tumor-specific siRNA therapy with synergistic drug effects.

Dual-function hybrid nanoparticles with gene silencing and anti-inflammatory effects

Background: Nanocarriers loaded with siRNA can be administered intranasally to provide a noninvasive, safe alternative to direct intracerebral or intrathecal infusions. Dual-function nanocarriers can also be designed to deliver several payloads that address different components of the pathological process. Aim: To design and test a hybrid nanocarrier with the capacity to lower Huntington's Disease gene (HTT) expression and prevent or diminish inflammation. Methods: Novel hybrid nanoparticles were fabricated using a chitosan-based matrix core loaded with siRNA and an outer shell consisting of a lipid composition containing cannabidiol. Results: Incubation of hybrid nanoparticles in mesenchymal stem cell cultures obtained from a YAC128 transgenic mouse modeling Huntington's disease resulted in effective lowering of mutant HTT gene expression and reduced levels of expression of the proinflammatory cytokine IL-6. Conclusion: A novel hybrid nanocarrier system with dual actions is effective in lowering HTT gene expression and attenuating inflammatory processes.

Nanoparticles for vaccine and gene therapy: Overcoming the barriers to nucleic acid delivery

Nucleic acid therapeutics can be used to control virtually every aspect of cell behavior and therefore have significant potential to treat genetic disorders, infectious diseases, and cancer. However, while clinically approved to treat a small number of diseases, the full potential of nucleic acid therapeutics is hampered by inefficient delivery. Nucleic acids are large, highly charged biomolecules that are sensitive to degradation and so the approaches to deliver these molecules differ significantly from traditional small molecule drugs. Current studies suggest less than 1% of the injected nucleic acid dose is delivered to the target cell in an active form. This inefficient delivery increases costs and limits their use to applications where a small amount of nucleic acid is sufficient. In this review, we focus on two of the major barriers to efficient nucleic acid delivery: (1) delivery to the target cell and (2) transport to the subcellular compartment where the nucleic acids are therapeutically active. We explore how nanoparticles can be modified with targeting ligands to increase accumulation in specific cells, and how the composition of the nanoparticle can be engineered to manipulate or disrupt cellular membranes and facilitate delivery to the optimal subcellular compartments. Finally, we highlight how with intelligent material design, nanoparticle delivery systems have been developed to deliver nucleic acids that silence aberrant genes, correct genetic mutations, and act as both therapeutic and prophylactic vaccines. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Biology-Inspired Nanomaterials > Lipid-Based Structures.

TME-Responsive Multistage Nanoplatform for siRNA Delivery and Effective Cancer Therapy

Since the discovery of RNA interference (RNAi), RNAi technology has rapidly developed into an efficient tool for post-transcriptional gene silencing, which has been widely used for clinical or preclinical treatment of various diseases including cancer. Small interfering RNA (siRNA) is the effector molecule of RNAi technology. However, as polyanionic macromolecules, naked siRNAs have a short circulatory half-life (<15 min) and is rapidly cleared by renal filtration, which greatly hinders their clinical application. Furthermore, the anionic and macromolecular characteristics of naked siRNAs impede their readiness to cross the cell membrane and therefore delivery vehicles are required to facilitate the cellular uptake and cytosolic delivery of naked siRNAs. In the past decade, numerous nanoparticles (NPs) such as liposomes have been employed for in vivo siRNA delivery, which have achieved favorable therapeutic outcomes in clinical disease treatment. In particular, because tumor microenvironment (TME) or tumor cells show several distinguishing biological/endogenous factors (eg, pH, enzymes, redox, and hypoxia) compared to normal tissues or cells, much attention has recently paid to design and construct TME-responsive NPs for multistaged siRNA delivery, which can respond to biological stimuli to achieve efficient in vivo gene silencing and better anticancer effect. In this review, we summarize recent advances in TME-responsive siRNA delivery systems, especially multistage delivery NPs, and discuss their design principles, functions, effects, and prospects.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

A pH and reduction dual-sensitive polymeric nanomicelle for tumor microenvironment triggered cellular uptake and controlled intracellular drug release

Minimal drug leakage during blood circulation and intracellular drug delivery in tumor sites are of great significance in chemotherapeutics. Herein we propose an interlayer crosslinked polymeric micelle with tumor acidity and reduction dual sensitivity for highly efficient drug delivery to cancer cells. A novel copolymer mPEG-C[double bond, length as m-dash]N-PAsp(MEA)-CA was synthesized and self-assembled into a dual-sensitive interlayer-crosslinked micelle (ICM). The micelle was composed of a tumor acidity sheddable PEG outer layer, a reduction-sensitive disulfide-crosslinked interlayer (PAsp(MEA)) and a hydrophobic core of cholic acid (CA) for doxorubicin (DOX) delivery. The nano-sized ICM was stable and showed little drug leakage in a neutral physiological environment. In tumor microenvironments (TMEs) with mild acidity, the PEG outer layer was readily detached due to the hydrolysis of the Schiff base linker, and the surface of the ICM was switched to positively charged to enhance the cellular uptake. Furthermore, inside tumor cells DOX was rapidly released due to the reduction of disulfide bonds by glutathione (GSH). The DOX-loaded ICM exhibited an effective anticancer effect against C6 glioma and reduced side effects both in vitro and in vivo. The study reveals that this pH and reduction dual-sensitive micelle may have great potential to mediate effective anticancer therapy.

Symbiotic Self-Assembly Strategy toward Lipid-Encased Cross-Linked Polymer Nanoparticles for Efficient Gene Silencing

A novel "symbiotic self-assembly" strategy that integrates the advantages of biocompatible lipids with a structurally robust polymer to efficiently encapsulate and deliver siRNAs is reported. The assembly process is considered to be symbiotic because none of the assembling components are capable of self-assembly but can form well-defined nanostructures in the presence of others. The conditions of the self-assembly process are simple but have been chosen such that it offers the ability to arrive at a system that is noncationic for mitigating carrier-based cytotoxicity, efficiently encapsulate siRNA to minimize cargo loss, be effectively camouflaged to protect the siRNA from nuclease degradation, and efficiently escape the endosome to cause gene knockdown. The lipid-siRNA-polymer (L-siP) nanoassembly formation and its disassembly in the presence of an intracellular trigger have been extensively characterized experimentally and through computational modeling. The complexes have been evaluated for the delivery of four different siRNA molecules in six different cell lines, where an efficient gene knockdown is demonstrated. The reported generalized strategy has the potential to make an impact on the development of a safe and effective delivery agent for RNAi-mediated gene therapy that holds the promise of targeting several hard-to-cure diseases.

Core-Shell Distinct Nanodrug Showing On-Demand Sequential Drug Release To Act on Multiple Cell Types for Synergistic Anticancer Therapy

Among various inflammatory factors/mediators, autocrine and paracrine prostaglandin 2 (PGE₂), which are abundant in various tumors, promote the proliferation and chemoresistance of cancer cells. Thus, eliminating the cytoprotective effect of PGE₂ may strengthen the antitumor effect of chemotherapy. Chemo/anti-inflammatory combination therapy requires the programmed activities of two different kinds of drugs that critically depend on their spatiotemporal manipulation inside the tumor. Here, a micellar polymeric nanosphere, encapsulating chemotherapeutic paclitaxel (PTX) in the core and conjugating anti-inflammatory celecoxib (CXB) to the shell through a peptide linker (PLGLAG), was developed. The PLGLAG linker was cleavable by the enzyme matrix metalloproteinase-2 (MMP-2) in the tumor tissue, causing CXB release and turning the negatively charged nanosphere into a positively charged one to facilitate PTX delivery into cancer cells. The released CXB not only acted on cyclooxygenase-2 (COX-2) to suppress the production of pro-inflammatory PGE₂ in multiple cell types but also suppressed the expression of the anti-apoptotic Bcl-2 gene to sensitize cancer cells to chemotherapy, thus resulting in a synergistic anticancer effect of PTX and CXB. This study represents an example of using a surface charge-switchable nanosphere with on-demand drug release properties to act on multiple cell types for highly effective chemo/anti-inflammatory combination therapy of cancer.

Co-Delivery of Doxorubicin and Anti-BCL-2 siRNA by pH-Responsive Polymeric Vector to Overcome Drug Resistance in In Vitro and In Vivo HepG2 Hepatoma Model

Drug resistance, developed through multiple mechanisms, is a major hindrance to successful chemotherapy of tumor. Combination therapy of chemotherapeutic drugs and siRNA represents an emerging strategy which may improve anticancer effect by synergistic actions. In this study, triblock copolymer of poly(ethylene glycol)- block-poly(l-lysine)- block-poly aspartyl ( N-( N', N'-diisopropylaminoethyl)) (PEG-PLL-PAsp(DIP)) was synthesized for the first time to enable the codelivery of BCL-2 siRNA and DOX. The system is supposed to not only bypass drug efflux but also down-regulate the antiapoptotic gene and consequently confronting against chemoresistance as well. Moreover, the pH responsive ability of the codelivery system can prevent drug leakage during circulation and guarantee swift drug release at tumors. The codelivered siRNA serves to suppress the expression of antiapoptotic BCL-2 and hence sensitize the cancer cells to anticancer drugs and produce improved therapeutic effect. Consequently, the codelivery of BCL-2 siRNA and anticancer drug DOX serves as a promising strategy against drug resistance in chemotherapy.

Preliminary Study of MR and Fluorescence Dual-mode Imaging: Combined Macrophage-Targeted and Superparamagnetic Polymeric Micelles

Purpose: To establish small-sized superparamagnetic polymeric micelles for magnetic resonance and fluorescent dual-modal imaging, we investigated the feasibility of MR imaging (MRI) and macrophage-targeted in vitro. Methods: A new class of superparamagnetic iron oxide nanoparticles (SPIONs) and Nile red-co-loaded mPEG-Lys3-CA4-NR/SPION polymeric micelles was synthesized to label Raw264.7 cells. The physical characteristics of the polymeric micelles were assessed, the T2 relaxation rate was calculated, and the effect of labeling on the cell viability and cytotoxicity was also determined in vitro. In addition, further evaluation of the application potential of the micelles was conducted via in vitro MRI. Results: The diameter of the mPEG-Lys3-CA4-NR/SPION polymeric micelles was 33.8 ± 5.8 nm on average. Compared with the hydrophilic SPIO, mPEG-Lys3-CA4-NR/SPION micelles increased transversely (r2), leading to a notably high r2 from 1.908 µg/mL-1S-1 up to 5.032 µg/mL-1S-1, making the mPEG-Lys3-CA4-NR/SPION micelles a highly sensitive MRI T2 contrast agent, as further demonstrated by in vitro MRI. The results of Confocal Laser Scanning Microscopy (CLSM) and Prussian blue staining of Raw264.7 after incubation with micelle-containing medium indicated that the cellular uptake efficiency is high. Conclusion: We successfully synthesized dual-modal MR and fluorescence imaging mPEG-Lys3-CA4-NR/SPION polymeric micelles with an ultra-small size and high MRI sensitivity, which were effectively and quickly uptaken into Raw 264.7 cells. mPEG-Lys3-CA4-NR/SPION polymeric micelles might become a new MR lymphography contrast agent, with high effectiveness and high MRI sensitivity.

Reduction and pH dual-sensitive nanovesicles co-delivering doxorubicin and gefitinib for effective tumor therapy

pH and reduction dual-sensitive polymeric nanovesicles were developed to simultaneously deliver hydrophobic gefitinib and hydrophilic doxorubicin for cancer therapy.

Nonviral cancer gene therapy: Delivery cascade and vector nanoproperty integration

Gene therapy represents a promising cancer treatment featuring high efficacy and limited side effects, but it is stymied by a lack of safe and efficient gene-delivery vectors. Cationic polymers and lipid-based nonviral gene vectors have many advantages and have been extensively explored for cancer gene delivery, but their low gene-expression efficiencies relative to viral vectors limit their clinical translations. Great efforts have thus been devoted to developing new carrier materials and fabricating functional vectors aimed at improving gene expression, but the overall efficiencies are still more or less at the same level. This review analyzes the cancer gene-delivery cascade and the barriers, the needed nanoproperties and the current strategies for overcoming these barriers, and outlines PEGylation, surface-charge, size, and stability dilemmas in vector nanoproperties to efficiently accomplish the cancer gene-delivery cascade. Stability, surface, and size transitions (3S Transitions) are proposed to resolve those dilemmas and strategies to realize these transitions are comprehensively summarized. The review concludes with a discussion of the future research directions to design high-performance nonviral gene vectors.

Polymeric vector-mediated delivery of an miR-21 inhibitor for prostate cancer treatment

An miR-21 silencing strategy based on a polymeric vector-mediated delivery system was developed for the effective treatment of human prostate cancer.

A novel polymeric micelle used for in vivo MR imaging tracking of neural stem cells in acute ischemic stroke

Novel cationic polymeric micelles based on biodegradable poly(aspartic acid-dimethylethanediamine)–lysine–cholic acid were synthesized for in vivo tracking therapeutic stem cells using MRI.

Zwitterionic stealth peptide-capped 5-aminolevulinic acid prodrug nanoparticles for targeted photodynamic therapy

5-Aminolevulinic acid (ALA) is a FDA-approved photodynamic therapy (PDT) precursor of protoporphyrin IX (PpIX) used for treating various cancers. However, the internalization of ALA is a big challenge due to its hydrophilic nature and low specificity to cancer cells. In this work, ALA conjugated prodrug nanoparticles were prepared by conjugation of thiolated stealth peptide sequence CPPPPEKEKEKEKEKEDGR and hydrazone-containing ALA to gold nanoparticles (AuNPs). Remarkable anti-fouling ability of ALA prodrug nanoparticles in complex environment was achieved owing to the zwitterionic stealth peptide sequence EKEKEKEKEK. The release of ALA could be greatly accelerated upon incubation of ALA prodrug nanoparticles in lysosomal/endosomal pH (pH 5.5). Meanwhile, the cellular internalization could be greatly enhanced by RGD moieties. MTT results demonstrated that ALA prodrug nanoparticles exhibited better photodynamic cytotoxicity than free ALA after light irradiation, suggesting enhanced photodynamic therapeutic efficacy.

Hierarchical Targeting Strategy for Enhanced Tumor Tissue Accumulation/Retention and Cellular Internalization

Targeted delivery of therapeutic agents is an important way to improve the therapeutic index and reduce side effects. To design nanoparticles for targeted delivery, both enhanced tumor tissue accumulation/retention and enhanced cellular internalization should be considered simultaneously. So far, there have been very few nanoparticles with immutable structures that can achieve this goal efficiently. Hierarchical targeting, a novel targeting strategy based on stimuli responsiveness, shows good potential to enhance both tumor tissue accumulation/retention and cellular internalization. Here, the recent design and development of hierarchical targeting nanoplatforms, based on changeable particle sizes, switchable surface charges and activatable surface ligands, will be introduced. In general, the targeting moieties in these nanoplatforms are not activated during blood circulation for efficient tumor tissue accumulation, but re-activated by certain internal or external stimuli in the tumor microenvironment for enhanced cellular internalization.

Zwitterionic Phosphorylcholine-TPE Conjugate for pH-Responsive Drug Delivery and AIE Active Imaging

Polymeric micelles have emerged as a promising nanoplatform for cancer theranostics. Herein, we developed doxorubicin (DOX) encapsulated pH-responsive polymeric micelles for combined aggregation induced emission (AIE) imaging and chemotherapy. The novel zwitterionic copolymer poly(2-methacryloyloxyethylphosphorylcholine-co-2-(4-formylphenoxy)ethyl methacrylate) (poly(MPC-co-FPEMA)) was synthesized via RAFT polymerization and further converted to PMPC-hyd-TPE after conjugation of tetraphenylethene (TPE, a typical AIE chromophore) via acid-cleavable hydrazone bonds. The AIE activatable copolymer PMPC-hyd-TPE could self-assemble into spherical PC-hyd-TPE micelles, and DOX could be loaded through hydrophobic interactions. The zwitterionic micelles exhibited excellent physiological stability and low protein adsorption due to the stealthy phosphorylcholine (PC) shell. In addition, the cleavage of hydrophobic TPE molecules under acidic conditions could induce swelling of micelles, which was verified by size changes with time at pH 5.0. The in vitro DOX release profile also exhibited accelerated release rate with pH value decreasing from 7.4 to 5.0. Fluorescent microscopy and flow cytometry studies further demonstrated fast internalization and accumulation of drug loaded PC-hyd-TPE-DOX micelles in HepG2 cells, resulting in considerable time/dose-dependent cytotoxicity. Meanwhile, high-quality AIE imaging of PC-hyd-TPE micelles was confirmed in HepG2 cells. Notably, ex vivo imaging study exhibited efficient accumulation and drug release of PC-hyd-TPE-DOX micelles in the tumor tissue. Consequently, the multifunctional micelles with combined nonfouling surface, AIE active imaging, and pH-responsive drug delivery showed great potential as novel nanoplatforms for a new generation of cancer theranostics.