A multifunctional envelope type nano device (MEND) for gene delivery to tumours based on the EPR effect: a strategy for overcoming the PEG dilemma

Co-delivery nanoparticle to overcome metastasis promoted by insufficient chemotherapy

Heterogeneous distribution of drug inside tumor is ubiquitous, causing regional insufficient chemotherapy, which might be the hotbed for drug resistance, tumor cell repopulation and metastasis. Herein, we verify, for the first time, that heterogeneous drug distribution induced insufficient chemotherapy would accelerate the process of epithelial mesenchymal transition (EMT), consequently resulting in the promotion of tumor metastasis. To eliminate the insufficient chemotherapy promoted metastasis, we conceived a co-delivery strategy by hydroxyethyl starch-polylactide (HES-PLA) nanoparticle, in which DOX and TGF-β receptor inhibitor, LY2157299 (LY), were administered together. In vitro and in vivo studies demonstrate that this co-delivery strategy can simultaneously suppress primary tumor and distant metastasis. Further study on immunofluorescence images of primary tumor verifies that low dose of DOX exasperates the EMT process, whereas the co-delivery nanoparticle can dramatically inhibit the progression of EMT. We reveal the impact of heterogeneous drug distribution on tumor metastasis and develop an effective co-delivery strategy to suppress the metastasis, providing guidance for clinical cancer therapy.

A multifunctional nanoparticle constructed with a detachable albumin outer shell and a redox-sensitive inner core for efficient siRNA delivery to hepatocellular carcinoma cells

Successful delivery of small interfering RNA (siRNA) into the cytoplasm of target cells relies on biocompatible and efficient vectors. In this study, a novel multifunctional core/shell nanoparticle [CS-SS-9R/BSA-c(RGDyK)] was developed to effectively deliver siVEGF to hepatocellular carcinoma cells (Bel-7402 cells). To improve the gene payload and transfection efficiency, a positively charged inner core (CS-SS-9R) was constructed by grafting nona-arginine (9R) onto chitosan (CS) using disulphide bonds. The negatively charged outer shell [BSA-c(RGDyK)] assembled on the surface of the inner core by electrostatic forces that shielded high cationic charges and provided improved targeting. The protein outer shell gradually detached from the inner core in the acidic lysosomal environment, leaving the cationic inner core exposed in order to escape from lysosomes. The nanoparticles were capable of delivering siVEGF into Bel-7402 cells via integrin receptor-mediated endocytosis. Successful lysosomal escape of the inner core and the rapid release of siVEGF into the cytoplasm resulted in a 78.9% decrease in VEGF expression and 81.2% inhibition of tumour cell proliferation. In conclusion, this nanoparticle is responsive to the intracellular environment and accurately delivered siRNA into the cytoplasm, providing a safe and highly efficient gene delivery strategy for cancer therapy.

Microfluidics for producing poly (lactic-co-glycolic acid)-based pharmaceutical nanoparticles

Microfluidic chips allow the rapid production of a library of nanoparticles (NPs) with distinct properties by changing the precursors and the flow rates, significantly decreasing the time for screening optimal formulation as carriers for drug delivery compared to conventional methods. The batch-to-batch reproducibility which is essential for clinical translation is achieved by precisely controlling the precursors and the flow rate, regardless of operators. Poly (lactic-co-glycolic acid) (PLGA) is the most widely used Food and Drug Administration (FDA)-approved biodegradable polymers. Researchers often combine PLGA with lipids or amphiphilic molecules to assemble into a core/shell structure to exploit the potential of PLGA-based NPs as powerful carriers for cancer-related drug delivery. In this review, we discuss the advantages associated with microfluidic chips for producing PLGA-based functional nanocomplexes for drug delivery. These laboratory-based methods can readily scale up to provide sufficient amount of PLGA-based NPs in microfluidic chips for clinical studies and industrial-scale production.

Advances in microfluidics for lipid nanoparticles and extracellular vesicles and applications in drug delivery systems

Lipid-based nanobiomaterials as liposomes and lipid nanoparticles (LNPs) are the most widely used nanocarriers for drug delivery systems (DDSs). Extracellular vesicles (EVs) and exosomes are also expected to be applied as DDS nanocarriers. The performance of nanomedicines relies on their components such as lipids, targeting ligands, encapsulated DNA, encapsulated RNA, and drugs. Recently, the importance of the nanocarrier sizes smaller than 100nm is attracting attention as a means to improve nanomedicine performance. Microfluidics and lab-on-a chip technologies make it possible to produce size-controlled LNPs by a simple continuous flow process and to separate EVs from blood samples by using a surface marker, ligand, or electric charge or by making a mass or particle size discrimination. Here, we overview recent advances in microfluidic devices and techniques for liposomes, LNPs, and EVs and their applications for DDSs.

Systemic tumor-targeted sodium iodide symporter (NIS) gene therapy of hepatocellular carcinoma mediated by B6 peptide polyplexes

BACKGROUND

Nonviral polymer-based gene transfer represents an adaptable system for tumor-targeted gene therapy because various design strategies of shuttle systems, together with the mechanistic concept of active tumor targeting, lead to improved gene delivery vectors resulting in higher tumor specificity, efficacy and safety.

METHODS

Using the sodium iodide symporter (NIS) as a theranostic gene, nonviral gene delivery vehicles based on linear polyethylenimine (LPEI), polyethylene glycol (PEG) and coupled to the synthetic peptide B6 (LPEI-PEG-B6), which specifically binds to tumor cells, were investigated in a hepatocellular carcinoma xenograft model for tumor selectivity and transduction efficiency.

RESULTS

In vitro incubation of three different tumor cell lines with LPEI-PEG-B6/NIS resulted in significant increase in iodide uptake activity compared to untargeted and empty vectors. After establishment of subcutaneous HuH7 tumors, NIS-conjugated nanoparticles were injected intravenously followed by analysis of radioiodide biodistribution using ¹²³ I-scintigraphy showing significant perchlorate-sensitive iodide accumulation in tumors of LPEI-PEG-B6/NIS-treated mice (8.0 ± 1.5% ID/g ¹²³ I; biological half-life of 4 h). After four cycles of repetitive polyplex/¹³¹ I applications, a significant delay of tumor growth was observed, which was associated with markedly improved survival in the therapy group.

CONCLUSIONS

These results clearly demonstrate that systemic in vivo NIS gene transfer using nanoparticle vectors coupled to B6 tumor targeting ligand is capable of inducing tumor-specific radioiodide uptake. This promising gene therapy approach opens the exciting prospect of NIS-mediated radionuclide therapy in metastatic cancer, together with the possibility of combining several targeting ligands to enhance selective therapeutic efficacy in a broad field of cancer types with various receptor expression profiles.

Transferrin-targeted, resveratrol-loaded liposomes for the treatment of glioblastoma

Glioblastomas (GBMs) are highly aggressive brain tumors with a very grim prognosis even after multi-modal therapeutic regimens. Conventional chemotherapeutic agents frequently lead to drug resistance and result in severe toxicities to non-cancerous tissues. Resveratrol (RES), a natural polyphenol with pleiotropic health benefits, has proven chemopreventive effects in all the stages of cancer including initiation, promotion and progression. However, the poor physico-chemical properties of RES severely limit its use as a free drug. In this study, RES was loaded into PEGylated liposomes (RES-L) to counter its drawbacks as a free drug. Since transferrin receptors (TfRs) are up-regulated in GBM, the liposome surface was modified with transferrin moieties (Tf-RES-L) to make them cancer cell-specific. The liposomal nanomedicines developed in this project were aimed at enhancing the physico-chemical properties of RES and exploiting the passive and active targeting capabilities of liposomes to effectively treat GBM. The RES-L were stable, had a good drug-loading capacity, prolonged drug-release in vitro and were easily scalable. Flow cytometry and confocal microscopy were used to study the association with, and internalization of, Tf-L into U-87 MG cells. The Tf-RES-Ls were significantly more cytotoxic and induced higher levels of apoptosis accompanied by activation of caspases 3/7 in GBM cells when compared to free RES or RES-L. The ability of RES to arrest cells in the S-phase of the cell cycle, and selectively induce production of reactive oxygen species in cancer cells were probably responsible for its cytotoxic effects. The therapeutic efficacy of RES formulations was evaluated in a subcutaneous xenograft mouse model of GBM. A tumor growth inhibition study and a modified survival study showed that Tf-RES-Ls were more effective than other treatments in their ability to inhibit tumor growth and improve survival in mice. Overall, the liposomal nanomedicines of RES developed in this project exhibited favorable in vitro and in vivo efficacies, which warrant their further investigation for the treatment of GBMs.

Multifunctional hybrid micelles with tunable active targeting and acid/phosphatase-stimulated drug release for enhanced tumor suppression

Therapeutic efficacy of conventional single PEGylated polymeric micelles is significantly reduced by limited endocytosis and intracellular drug release. To improve drug delivery efficiency, poly (ethylene glycol)-block-poly (l-lactic acid)/(Arg-Gly-Asp-Phe)-poly (aminoethyl ethylene phosphate)-block-poly (l-lactic acid) (PEG-PLLA/RGDF-PAEEP-PLLA) hybrid micelles with tunable active targeting and acid/phosphatase-stimulated drug release are developed. The optimized hybrid micelles with 6 wt % of RGDF have favorable in vitro and in vivo activities. The hybrid micelles could temporarily shield the targeting efficacy of RGDF at pH 7.4 due to the steric effect exerted by concealment of RGDF peptides in the PEG corona, which strongly decreases the clearance by mononuclear phagocyte system and consequently improves the tumor accumulation. Inside the solid tumor with a lower acidic pH, the hybrid micelles restore the active tumor targeting property with exposed RGDF on the surface of the micelles because of the increased protonation and stretching degree of PAEEP blocks. RGDF-mediated endocytosis improves the tumor cell uptake. The hybrid micelles would also enhance intracellular drug release because of the hydrolysis of the acid/phosphatase-sensitivity of PAEEP blocks in endo/lysosome. Systemic administration of the hybrid micelles significantly inhibits tumor growth by 96% due to the integration of enhanced circulation time, tumor accumulation, cell uptake and intracellular drug release.

Enhanced antitumor and anti-metastasis efficacy against aggressive breast cancer with a fibronectin-targeting liposomal doxorubicin

The chemotherapy of aggressive breast tumor is usually accompanied by a poor prognosis because of the metastasis of tumor cells. Thus, it is important to simultaneously enhance antitumor and anti-metastasis efficacy. Fibronectin and its complexes are expressed on the walls of tumor vessels and in tumor stroma. Moreover, the expression of fibronectin in metastatic sites is even higher than that in primary tumors. Herein, we designed a fibronectin-targeting CREKA-modified liposomal doxorubicin (CREKA-Lipo-Dox) for the therapy of metastatic breast tumor. CREKA-Lipo was uniformly formed with high entrapment efficiency. It exhibited longer blood circulation time compared with free Dox, and there was no significant change compared with PEG-Lipo-Dox. Immunofluorescence results revealed that the CREKA-Lipo-Dox could specifically bind to fibronectin in the tumor vessels and tumor stroma. The antitumor and anti-metastasis efficacy of CREKA-loaded liposome was more obvious than that of free Dox or unmodified Dox-Lipo. Taken together, binding fibronectin by CREKA could be an attractive therapeutic strategy for metastatic breast cancer in the future.

Polycation-telodendrimer nanocomplexes for intracellular protein delivery

Intracellular delivery of protein therapeutics by cationic polymer vehicles is an emerging technique that is, however, encountering poor stability, high cytotoxicity and non-specific cell uptake. Herein, we present a facile strategy to optimize the protein-polycation complexes by encapsulating with linear-dendritic telodendrimers. The telodendrimers with well-defined structures enable the rational design and integration of multiple functionalities for efficient encapsulation of the protein-polycation complexes by multivalent and hybrid supramolecular interactions to produce sub-20 nm nanoparticles. This strategy not only reduces the polycation-associated cytotoxicity and hemolytic activity, but also eliminates the aggregation and non-specific binding of polycations to other biomacromolecules. Moreover, the telodendrimers dissociate readily from the complexes during the cellular uptake process, which restores the capability of polycations for intracellular protein delivery. This strategy overcomes the limitations of polycationic vectors for intracellular delivery of protein therapeutics.

pH-Responsive Charge-Conversional and Hemolytic Activities of Magnetic Nanocomposite Particles for Cell-Targeted Hyperthermia

Magnetic nanocomposite particle (MNP)-induced hyperthermia therapy has been restricted by inefficient cellular targeting. pH-responsive charge-conversional MNPs can enhance selective cellular uptake in acidic cells like tumors by sensing extracellular acidity based on their charge alteration. We have synthesized new, pH-induced charge-conversional, superparamagnetic, and single-cored Fe₃O₄ nanocomposite particles coated by N-itaconylated chitosan (NICS) cross-linked with ethylene glycol diglycidyl ether (EGDE) (Fe₃O₄-NICS-EGDE) using a simple, one-step chemical coprecipitation-coating process. The surface of the Fe₃O₄-NICS-EGDE nanocomposite particles was modified with ethanolamine (EA) via aza-Michael addition to enhance their buffering capacity, aqueous stability, and pH sensitivity. The designed Fe₃O₄-NICS-EGDE-EA nanocomposite particles showed pH-dependent charge-conversional properties, colloidal stability, and excellent hemocompatibility in physiological media. By contrast, the charge-conversional properties enabled microwave-induced hemolysis only under weakly acidic conditions. Therefore, the composite particles are highly feasible for magnetically induced and targeted cellular thermotherapeutic applications.

Optimization of the Preparation Conditions of Borneol-Modified Ginkgolide Liposomes by Response Surface Methodology and Study of Their Blood Brain Barrier Permeability

Ginkgolides (GG), containing ginkgolide A (GA), ginkgolide B (GB) and ginkgolide C (GC), are mainly prescribed for ischemic stroke and cerebral infarction. However, the ginkgolides can hardly pass the blood-brain barrier (BBB) into the brain. The purpose of this study was to prepare borneol-modified ginkgolides liposomes (GGB-LPs) to study whether borneol could enhance the transport of ginkgolides across the BBB. The preparation conditions of GGB-LPs were optimized by a response surface-central composite design. Also, pharmacokinetics and biodistribution studies of GGB-LPs were conducted using UPLC-MS. The optimal preparation conditions for GGB-LP were as follows: ratio of lipid to drug (w/w) was 9:1, ratio of phospholipid to cholesterol (w/w) was 7:1, and hydrate volume was 17.5 mL. Under these conditions, the GGB-LP yield was 89.73 ± 3.45%. With GGB-LPs, borneol significantly promoted the transport of ginkgolide across the BBB. The pharmacokinetic parameters of GGB-LP were significantly improved too, with T_max of 15 min and a high drug concentration of 3.39 μg/g in brain. Additionally, the drug targeting index and relative uptake rate of GGB-LP was increased. Borneol-modified ginkgolide liposomes can thus potentially be used to improve the BBB permeability of gingkolide formulations.

Recent insights into mitochondrial targeting strategies in liver transplantation

Ischemia/reperfusion (I/R) injury in liver transplantation can disrupt the normal activity of mitochondria in the hepatic parenchyma. This potential dysfunction of mitochondria after I/R injury could be responsible for the initial poor graft function or primary nonfunction observed after liver transplantation. Thus, determining the mechanisms that lead to human hepatic mitochondrial dysfunction might contribute to improving the outcome of liver transplantation. Furthermore, early identification of novel prognostic factors involved in I/R injury could serve as a key endpoint to predict the outcome of liver grafts and also to promote the early adoption of novel strategies that protect against I/R injury. Here, we briefly review recent advances in the study of mitochondrial dysfunction and I/R injury, particularly in relation to liver transplantation. Next, we highlight various pharmacological therapeutic strategies that could be applied, and discuss their relationship to relevant mitochondrion-related processes and targets. Lastly, we note that although considerable progress has been made in our understanding of I/R injury and mitochondrial dysfunction, further investigation is required to elucidate the cellular and molecular mechanisms underlying these processes, thereby identifying biomarkers that can help in evaluating donor organs.

Mesoporous silica nanoparticle-based intelligent drug delivery system for bienzyme-responsive tumour targeting and controlled release

This paper proposes a novel type of multifunctional envelope-type mesoporous silica nanoparticle (MSN) to achieve cancer cell targeting and drug-controlled release. In this system, MSNs were first modified by active targeting moiety hyaluronic acid (HA) for breast cancer cell targeting and hyaluronidases (Hyal)-induced intracellular drug release. Then gelatin, a proteinaceous biopolymer, was grafted onto the MSNs to form a capping layer via glutaraldehyde-mediated cross-linking. To shield against unspecific uptake of cells and prolong circulation time, the nanoparticles were further decorated with poly(ethylene glycol) polymers (PEG) to obtain MSN@HA-gelatin-PEG (MHGP). Doxorubicin (DOX), as a model drug, was loaded into PEMSN to assess the breast cancer cell targeting and drug release behaviours. In vitro study revealed that PEG chains protect the targeting ligand and shield against normal cells. After reaching the breast cancer cells, MMP-2 overpressed by cells hydrolyses gelatin layer to deshield PEG and switch on the function of HA. As a result, DOX-loaded MHGP was selectively trapped by cancer cells through HA receptor-mediated endocytosis and subsequently release DOX due to Hyal-catalysed degradation of HA. This system presents successful bienzyme-responsive targeting drug delivery in an optimal fashion and provides potential applications for targeted cancer therapy.

Near-infrared AIEgen-functionalized and diselenide-linked oligo-ethylenimine with self-sufficing ROS to exert spatiotemporal responsibility for promoted gene delivery

We attempted to synthesize an oligo-ethyleneimine (OEI)-crosslinked polycation, characterized with self-sufficing ROS by virtue of a functional AIE component and an ROS-labile diselenide linkage.

Radiation-enhanced delivery of plasmid DNA to tumors utilizing a novel PEI polyplex

The excitement surrounding the potential of gene therapy has been tempered due to the challenges that have thus far limited its successful implementation in the clinic such as issues regarding stability, transfection efficiency, and toxicity. In this study, low molecular weight linear polyethyleneimine (2.5 kDa) was modified by conjugation to a lipid, lithocholic acid, and complexed with a natural polysaccharide, dermatan sulfate (DS), to mask extra cationic charges of the modified polymer. In vitro examination revealed that these modifications improved complex stability with plasmid DNA (pDNA) and transfection efficiency. This novel ternary polyplex (pDNA/3E/DS) was used to investigate if tumor-targeted radiotherapy led to enhanced accumulation and retention of gene therapy vectors in vivo in tumor-bearing mice. Imaging of biodistribution revealed that tumor irradiation led to increased accumulation and retention as well as decreased off-target tissue buildup of pDNA in not only pDNA/3E/DS, but also in associated PEI-based polyplexes and commercial DNA delivery vehicles. The DS-containing complexes developed in this study displayed the greatest increase in tumor-specific pDNA delivery. These findings demonstrate a step forward in nucleic acid vehicle design as well as a promising approach to overall cancer gene therapy through utilization of radiotherapy as a tool for enhanced delivery.

Effective in vivo gene delivery with reduced toxicity, achieved by charge and fatty acid -modified cell penetrating peptide

Non-viral gene delivery systems have gained considerable attention as a promising alternative to viral delivery to treat diseases associated with aberrant gene expression. However, regardless of extensive research, only a little is known about the parameters that underline in vivo use of the nanoparticle-based delivery vectors. The modest efficacy and low safety of non-viral delivery are the two central issues that need to be addressed. We have previously characterized an efficient cell penetrating peptide, PF14, for in vivo applications. In the current work, we first develop an optimized formulation of PF14/pDNA nanocomplexes, which allows removal of the side-effects without compromising the bioefficacy in vivo. Secondly, based on the physicochemical complex formation studies and biological efficacy assessments, we develop a series of PF14 modifications with altered charge and fatty acid content. We show that with an optimal combination of overall charge and hydrophobicity in the peptide backbone, in vivo gene delivery can be augmented. Further combined with the safe formulation, systemic gene delivery lacking any side effects can be achieved.

Understanding the formation mechanism of lipid nanoparticles in microfluidic devices with chaotic micromixers

Lipid nanoparticles (LNPs) or liposomes are the most widely used drug carriers for nanomedicines. The size of LNPs is one of the essential factors affecting drug delivery efficiency and therapeutic efficiency. Here, we demonstrated the effect of lipid concentration and mixing performance on the LNP size using microfluidic devices with the aim of understanding the LNP formation mechanism and controlling the LNP size precisely. We fabricated microfluidic devices with different depths, 11 μm and 31 μm, of their chaotic micromixer structures. According to the LNP formation behavior results, by using a low concentration of the lipid solution and the microfluidic device equipped with the 31 μm chaotic mixer structures, we were able to produce the smallest-sized LNPs yet with a narrow particle size distribution. We also evaluated the mixing rate of the microfluidic devices using a laser scanning confocal microscopy and we estimated the critical ethanol concentration for controlling the LNP size. The critical ethanol concentration range was estimated to be 60–80% ethanol. Ten nanometer-sized tuning of LNPs was achieved for the optimum residence time at the critical concentration using the microfluidic devices with chaotic mixer structures. The residence times at the critical concentration necessary to control the LNP size were 10, 15–25, and 50 ms time-scales for 30, 40, and 50 nm-sized LNPs, respectively. Finally, we proposed the LNP formation mechanism based on the determined LNP formation behavior and the critical ethanol concentration. The precise size-controlled LNPs produced by the microfluidic devices are expected to become carriers for next generation nanomedicines and they will lead to new and effective approaches for cancer treatment.

Role of CTGF in Sensitivity to Hyperthermia in Ovarian and Uterine Cancers

Even though hyperthermia is a promising treatment for cancer, the relationship between specific temperatures and clinical benefits and predictors of sensitivity of cancer to hyperthermia is poorly understood. Ovarian and uterine tumors have diverse hyperthermia sensitivities. Integrative analyses of the specific gene signatures and the differences in response to hyperthermia between hyperthermia-sensitive and -resistant cancer cells identified CTGF as a key regulator of sensitivity. CTGF silencing sensitized resistant cells to hyperthermia. CTGF small interfering RNA (siRNA) treatment also sensitized resistant cancers to localized hyperthermia induced by copper sulfide nanoparticles and near-infrared laser in orthotopic ovarian cancer models. CTGF silencing aggravated energy stress induced by hyperthermia and enhanced apoptosis of hyperthermia-resistant cancers.

Delivery Pathway Regulation of 3',3″-Bis-Peptide-siRNA Conjugate via Nanocarrier Architecture Engineering

Small interfering RNA (siRNA) has been continuously explored for clinical applications. However, neither nanocarriers nor conjugates have been able to remove the obstacles. In this study, we employed a combined nanochemistry strategy to optimize its delivery dilemma, where different interactions and assembly modes were cooperatively introduced into the forming process of siRNA/lipids nanoplexes. In the nanoplexes, the 3',3″-bis-peptide-siRNA conjugate (pp-siRNA) and gemini-like cationic lipids (CLDs) were employed as dual regulators to improve their bio-behavior. We demonstrated that the "cicada pupa"-shaped nanoplexes of MT-pp-siRNA/CLDs (MT represented the mixed two-phase method) exhibited more compact multi-sandwich structure (∼25 layers), controllable size (∼150 nm), and lower zeta potential (∼22 mV) than other comparable nanoplexes and presented an increased siRNA protection and stability. Significantly, the nanoplex was internalized into melanoma cells by almost caveolae-mediated endocytosis and macropinocytosis (∼99.46%), and later reduced/avoided lysosomal degradation. Finally, the nanoplex facilitated the silencing of mRNA of the mutant B-Raf protein (down by ∼60%). In addition, pp-siRNA had a high intracellular sustainability, a significantly prolonged circulating time, and accumulation in tumor tissues in vivo. Our results have demonstrated that the combined approach can improve the intracellular fate of siRNA, which opens up novel avenues for efficient siRNA delivery.

Solid-phase supported design of carriers for therapeutic nucleic acid delivery

Nucleic acid molecules are important therapeutic agents in the field of antisense oligonucleotide, RNA interference, and gene therapies. Since nucleic acids are not able to cross cell membranes and enter efficiently into cells on their own, the development of efficient, safe, and precise delivery systems is the crucial challenge for development of nucleic acid therapeutics. For the delivery of nucleic acids to their intracellular site of action, either the cytosol or the nucleus, several extracellular and intracellular barriers have to be overcome. Multifunctional carriers may handle the different special requirements of each barrier. The complexity of such macromolecules however poses a new hurdle in medical translation, which is the chemical production in reproducible and well-defined form. Solid-phase assisted synthesis (SPS) presents a solution for this challenge. The current review provides an overview on the design and SPS of precise sequence-defined synthetic carriers for nucleic acid cargos.

Small molecule delivery to solid tumors with chitosan-coated PLGA particles: A lesson learned from comparative imaging

For polymeric nanoparticles (NPs) to deliver more drugs to tumors than free drug solution, it is critical that the NPs establish interactions with tumor cells and avoid removal from the tumors. Since traditional polyethylene glycol (PEG) surface layer interferes with the cell-NP interaction in tumors, we used a water-soluble and blood-compatible chitosan derivative called zwitterionic chitosan (ZWC) as an alternative surface coating for poly(lactic-co-glycolic acid) (PLGA) NPs. The ZWC-coated PLGA NPs showed pH-dependent surface charge profiles and differential cellular interactions according to the pH of the medium. The in vivo delivery of ZWC-coated NPs was evaluated in mice bearing LS174T-xenografts using magnetic resonance (MR) imaging and fluorescence whole body imaging, which respectively tracked iron oxide particles and indocyanine green (ICG) encapsulated in the NPs as tracers. MR imaging showed that ZWC-coated NPs were more persistent in tumors than PEG-coated NPs, in agreement with the in vitro results. However, the fluorescence imaging indicated that the increased NP retention in tumors by the ZWC coating did not significantly affect the ICG distribution in tumors due to the rapid release of the dye. This study shows that stable drug retention in NPs during circulation is a critical prerequisite to successful translation of the potential benefits of surface-engineered NPs.

Multifunctional nanoparticles co-delivering EZH2 siRNA and etoposide for synergistic therapy of orthotopic non-small-cell lung tumor

Malignant proliferation and metastasis in non-small cell lung carcinoma (NSCLC) are great challenges for effective clinical treatment through conventional chemotherapy. The combinational therapy strategy of RNA interfering (RNAi) technology and chemotherapeutic agents have been reported to be promising for effective cancer therapy. In this study, based on multifunctional nanoparticles (NPs), the simultaneous delivery of etoposide (ETP) and anti-Enhancer of Zeste Homologue 2 (EZH2) siRNA for the effective treatment of orthotopic lung tumor was achieved. The NPs exhibited pH/redox dual sensitivity verified by particle size changes, morphological changes, and in vitro release of drugs. Confocal microscopy analysis confirmed that the NPs exhibited endosomal escape property and on-demand intracellular drug release behavior, which can protect siRNA from degradation and facilitate the chemotherapeutic effect respectively. In vitro tumor cell motility study demonstrated that EZH2 siRNA loaded in NPs can decrease the migration and invasion capabilities of tumor cells by downregulating the expression of EZH2 mRNA and protein. In particular, an antiproliferation study revealed that the co-delivery of siRNA and ETP in the multifunctional NPs can induce a synergistic therapeutic effect on NSCLC. In vivo targeting evaluation showed that cRGDyC-PEG modification on NPs exhibited a low distribution in normal organs and an obvious accumulation in orthotopic lung tumor. Furthermore, targeted NPs co-delivering siRNA and ETP showed superior inhibition on tumor growth and metastasis and produced minimal systemic toxicity. These findings indicated that multifunctional NPs can be utilized as a co-delivery system, and that the combination of EZH2 siRNA and ETP can effectively treat NSCLC.

EGFR Targeting and Shielding of pDNA Lipopolyplexes via Bivalent Attachment of a Sequence-Defined PEG Agent

For successful nonviral gene delivery, cationic polymers are promising DNA carrier, which need to comprise several functionalities. The current work focuses on the postincorporation of epidermal growth factor receptor (EGFR) targeted PEGylation agents onto lipopolyplexes for pDNA delivery. T-shaped lipo-oligomers are previously found to be effective sequence-defined carriers for pDNA and siRNA. Here, the bis-oleoyl-oligoaminoethanamide 454 containing tyrosine trimer-cysteine ends is applied for complex formation with pDNA coding for luciferase or sodium iodide symporter (NIS). In a second step, the lipopolyplexes are modified via disulfide formation with sequence-defined monovalent or bivalent PEGylation agents containing one or two 3-nitro-2-pyridinesulfenyl (NPys)-activated cysteines, respectively. For targeting, the polyethylene glycol (PEG) agents comprise the EGFR targeting peptide GE11. In comparison of all transfection complexes, 454 lipopolyplexes modified with the bidentate PEG-GE11 agent show the best, EGFR-dependent uptake as well as luciferase and NIS gene expression into receptor-positive tumor cells.

Near-Infrared Triggered Upconversion Polymeric Nanoparticles Based on Aggregation-Induced Emission and Mitochondria Targeting for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is an auspicious strategy for cancer therapy by yielding reactive oxygen species (ROS) under light irradiation. Here, we have developed near-infrared (NIR) triggered polymer encapsulated upconversion nanoparticles (UCNPs) based on aggregation-induced emission (AIE) characteristics and mitochondria target ability for PDT. The coated AIE polymer as a photosensitizer can be photoactivated by the up-converted energy of UCNPs upon 980 nm laser irradiation, which could generate ROS efficiently in mitochondria and induce cell apoptosis. Moreover, a "sheddable" poly(ethylene glycol) (PEG) layer was easily conjugated at the surface of NPs. The pH-responsive PEG layer shields the surface positive charges and shows stronger protein-resistance ability. In the acidic tumor environment, PEGylated NPs lose the PEG layer and show the mitochondria-targeting ability by responding to tumor acidity. A cytotoxicity study indicated that these NPs have good biocompatibility in the dark but exert severe cytotoxicity to cancer cells, with only 10% cell viability, upon being irradiated with an NIR laser. The AIE nanoparticles are a good candidate for effective mitochondria targeting photosensitizer for PDT.

Non-Covalent Assembly Method that Simultaneously Endows a Liposome Surface with Targeting Ligands, Protective PEG Chains, and Deep-Red Fluorescence Reporter Groups

A new self-assembly method is used to rapidly functionalize the surface of liposomes without perturbing the membrane integrity or causing leakage of the aqueous contents. The key molecule is a cholesterol-squaraine-PEG conjugate with three important structural elements: a cholesterol membrane anchor, a fluorescent squaraine docking station that allows rapid and high-affinity macrocycle threading, and a long PEG-2000 chain to provide steric shielding of the decorated liposome. The two-step method involves spontaneous insertion of the conjugate into the outer leaflet of pre-formed liposomes followed by squaraine threading with a tetralactam macrocycle that has appended targeting ligands. A macrocycle with six carboxylates permitted immobilization of intact fluorescent liposomes on the surface of cationic polymer beads, whereas a macrocycle with six zinc(II)-dipicolylamine units enabled selective targeting of anionic membranes, including agglutination of bacteria in the presence of human cells.

Sequentially Responsive Shell-Stacked Nanoparticles for Deep Penetration into Solid Tumors

Nanomedicine to overcome both systemic and tumor tissue barriers ideally should have a transformable size and surface, maintaining a certain size and negative surface charge for prolonged circulation, while reducing to a smaller size and switching to a positive surface charge for efficient penetration to and retention in the interstitial space throughout the tumor tissue. However, the design of such size and charge dual-transformable nanomedicine is rarely reported. Here, the design of a shell-stacked nanoparticle (SNP) is reported, which can undergo remarkable size reduction from about 145 to 40 nm, and surface charge reversal from -7.4 to 8.2 mV at acidic tumor tissue, for enhanced tumor penetration and uptake by cells in deep tumor tissue. The disulfide-cross-linked core maintains the stability of the particle and prevents undesired premature drug release until the shedding of the shell, which accelerates the cleavage of more exposed disulfide bond sand intracellular drug release. SNP penetrates about 1 mm into xenografted A549 lung carcinoma, which is about four times penetration depth of the nontransformable one. The doxorubicin (DOX)-loaded SNP (SNP/DOX) shows significant antitumor efficacy and nearly eradicates the tumor, substantiating the importance of the design of size and charge dual-transformable nanomedicine.

pH-labile PEGylation of siRNA-loaded lipid nanoparticle improves active targeting and gene silencing activity in hepatocytes

Lipid nanoparticles (LNPs) are one of the promising technologies for the in vivo delivery of short interfering RNA (siRNA). Modifying LNPs with polyethyleneglycol (PEG) is widely used to inhibit non-specific interactions with serum components in the blood stream, and is a useful strategy for maximizing the efficiency of active targeting. However, it is a widely accepted fact that PEGylation of the LNP surface strongly inhibits fusion between LNPs and endosomal membranes, resulting in poor cytosolic siRNA delivery, a process that is referred to as the 'PEG-dilemma'. In the present study, in an attempt to overcome this problem, siRNA-loaded LNPs were modified with PEG through maleic anhydride, a pH-labile linkage. The in vitro, suppression of cationic charge, stealth function at physiological pH up to 1h and the rapid desorption of PEG and restoration of fusogenic activity under slightly acidic conditions (within only 2min) were achieved by PEG modification of the LNPs through maleic anhydride. In vivo, PEG modification through maleic anhydride resulted in a dramatic improvement in the targeting capability of the active targeting of ligand (N-acetyl-d-galactosamine)-modified LNPs to hepatocytes, with an approximately 14-fold increase in gene silencing activity in factor 7 model mice. Taken together, the maleic anhydride-mediated pH-labile PEGylation of the active targeting LNPs is a useful strategy for achieving the specific and efficient delivery of siRNAs in vivo.

Block copolymer conjugated Au-coated Fe3O4 nanoparticles as vectors for enhancing colloidal stability and cellular uptake

BACKGROUND

Polymer surface-modified inorganic nanoparticles (NPs) provide a multifunctional platform for assisting gene delivery. Rational structure design for enhancing colloidal stability and cellular uptake is an important strategy in the development of safe and highly efficient gene vectors.

RESULTS

Heterogeneous Au-coated Fe3O4 (Fe3O4@Au) NPs capped by polyethylene glycol-b-poly1-(3-aminopropyl)-3-(2-methacryloyloxy propylimidazolium bromine) (PEG-b-PAMPImB-Fe3O4@Au) were prepared for DNA loading and magnetofection assays. The Au outer shell of the NPs is an effective platform for maintaining the superparamagnetism of Fe3O4 and for PEG-b-PAMPImB binding via Au-S covalent bonds. By forming an electrostatic complex with DNA at the inner PAMPImB shell, the magnetic nanoplexes offer steric protection from the outer corona PEG, thereby promoting high colloidal stability. Transfection efficiency assays in human esophageal cancer cells (EC109) show that the nanoplexes have high transfection efficiency at a short incubation time in the presence of an external magnetic field, due to increased cellular internalization via magnetic acceleration. Finally, after transfection with the magnetic nanoplexes EC109 cells acquire magnetic properties, thus allowing for selective separation of transfected cells.

CONCLUSION

Precisely engineered architectures based on neutral-cationic block copolymer-conjugated heterogeneous NPs provide a valuable strategy for improving the applicability and efficacy of synthesized vectors.

Immune-camouflaged graphene oxide nanosheets for negative regulation of phagocytosis by macrophages

Signal regulatory protein alpha (SIRPα) is highly expressed in macrophages of the reticuloendothelial system and in tumor-associated macrophages, whereas tumor cells express the surface membrane protein, CD47, which interacts with SIRPα to negatively regulate phagocytosis. In this study, we modified the surfaces of graphene oxide (GO) nanosheets with a CD47-like SIRPα-binding peptide (SP). The presence of SP on GO nanosheets reduced the macrophage uptake to a greater extent than the PEGylation of such nanosheets. This reduced uptake was found to be mediated by the activation of Src homology region 2 domain-containing phosphatase 1 (SHP-1) and the downstream inhibition of myosin assembly, which is necessary for phagosome formation. Unlike SP-coated GO nanosheets, PEGylated GO nanosheets did not affect myosin assembly or phagocytosis. After in vivo systemic administration, the clearance of SP-coated GO nanosheets was slower than that of PEGylated GO nanosheets, and this difference increased with repeated administration. Finally, SP-coated GO nanosheets showed a higher distribution to tumor tissues than PEGylated GO nanosheets or a physical mixture of SP and GO nanosheets. Our findings indicate that immune-camouflaged GO nanosheets with natural CD47-like SIRPα-binding molecules can reduce the nonspecific loss of such nanosheets through macrophage uptake, thereby enhancing their blood circulation and tumor delivery after multiple injections.

α-Amylase- and Redox-Responsive Nanoparticles for Tumor-Targeted Drug Delivery

Paclitaxel (PTX) is an effective antineoplastic agent and shows potent antitumor activity against a wide spectrum of cancers. Yet, the wide clinical use of PTX is limited by its poor aqueous solubility and the side effects associated with its current therapeutic formulation. To tackle these obstacles, we report, for the first time, α-amylase- and redox-responsive nanoparticles based on hydroxyethyl starch (HES) for the tumor-targeted delivery of PTX. PTX is conjugated onto HES by a redox-sensitive disulfide bond to form HES-SS-PTX, which was confirmed by results from NMR, high-performance liquid chromatography-mass spectrometry, and Fourier transform infrared spectrometry. The HES-SS-PTX conjugates assemble into stable and monodispersed nanoparticles (NPs), as characterized with Dynamic light scattering, transmission electron microscopy, and atomic force microscopy. In blood, α-amylase will degrade the HES shell and thus decrease the size of the HES-SS-PTX NPs, facilitating NP extravasation and penetration into the tumor. A pharmacokinetic study demonstrated that the HES-SS-PTX NPs have a longer half-life than that of the commercial PTX formulation (Taxol). As a consequence, HES-SS-PTX NPs accumulate more in the tumor compared with the extent of Taxol, as shown in an in vivo imaging study. Under reductive conditions, the HES-SS-PTX NPs could disassemble quickly as evidenced by their triggered collapse, burst drug release, and enhanced cytotoxicity against 4T1 tumor cells in the presence of a reducing agent. Collectively, the HES-SS-PTX NPs show improved in vivo antitumor efficacy (63.6 vs 52.4%) and reduced toxicity in 4T1 tumor-bearing mice compared with those of Taxol. These results highlight the advantages of HES-based α-amylase- and redox-responsive NPs, showing their great clinical translation potential for cancer chemotherapy.

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.

Responsive Nanocarriers as an Emerging Platform for Cascaded Delivery of Nucleic Acids to Cancer

Cascades of systemic and intracellular obstacles, including low stability in blood, little tumor accumulation, weak tumor penetration, poor cellular uptake, inefficient endosomal escape and deficient disassembly in the cytoplasm, must be overcome in order to deliver nucleic acid drugs for cancer therapy. Nanocarriers that are sensitive to a variety of physiological stimuli, such as pH, redox status, and cell enzymes, are substantially changing the landscape of nucleic acid drug delivery by helping to overcome cascaded systemic and intracellular barriers. This review discusses nucleic acid-based therapeutics, systemic and intracellular barriers to efficient nucleic acid delivery, and nanocarriers responsive to extracellular and intracellular biological stimuli to overcome individual barriers. In particular, responsive nanocarriers for the cascaded delivery of nucleic acids in vivo are highlighted. Developing novel cascaded nanocarriers that transform their physicochemical properties in response to various stimuli in a timely and spatially controlled manner for nucleic acid drug delivery holds great potential for translating the promise of nucleic acid drugs and achieving clinically successful cancer therapy.

Preparation of intravenous injection nanoformulation via co-assemble between cholesterylated gemcitabine and cholesterylated mPEG: enhanced cellular uptake and intracellular drug controlled release

The objective of this study was to prepare the CHS-mPEG/CHS-dFdC nanoformulation could be administrated through intravenous injection in nude mice. Particularly, CHS-mPEG was selected to co-assemble with CHS-dFdC to improve the prodrug concentration and enhance the stability of nanoformulation. The nanoformulation could be prepared by codissolution-coprecipitation. All of the nanoformulations kept stable in PBS at 4 °C or simulative human plasma at 37 °C. As molar ratios of CHS-mPEG₁₉₀₀/CHS-dFdC increased from 0.1/1 to 2/1, the weight concentration of CHS-dFdC increased from 2.5 to 15 mg/mL. It was found the optimal CHS-mPEG₁₉₀₀/CHS-dFdC nanoformulation displayed controlled drug release in simulative lysosome condition. The amount of released dFdC reached up to 90% within 10 h. It also exhibited enhanced cellular uptake ability, 7-folds higher than that of dFdC during 2.5 h incubation. And it showed superior cytotoxicity resulted from the enhanced cellular uptake ability on BxPC-3 cells.

pH Triggered Size Increasing Gene Carrier for Efficient Tumor Accumulation and Excellent Antitumor Effect

High efficiency and serum resistant capacity are important for gene carrier in vivo usage. In this study, transfection efficiency and cell toxicity of polyethylenimine (PEI) (branched, Mw = 25K) was remarkably improved, when mixed with polyanion (polyethylene glycol-polyglutamic acid (PEG-PLG) or polyglutamic acid (PLG)). Different composite orders of PEI, polyanion, and gene, for example, PEI is first complexed with DNA, and then with polyanion, or PEI is first complexed with polyanion, and then with DNA, were studied. Results showed that only the polyanion/PEI complexes exhibited additional properties, such as decreased pH, resulting in increased particle size, as well as enhanced serum resistance capability and improved tumor accumulation. The prepared gene carrier showed excellent antitumor effect, with no damage on major organs, which is suitable for in vivo gene antitumor therapy.

Polyethylene glycol-poly(ε-benzyloxycarbonyl-l-lysine)-conjugated VEGF siRNA for antiangiogenic gene therapy in hepatocellular carcinoma

A polyethylene glycol-poly(ε-benzyloxycarbonyl-l-lysine) (PEG-SS-PLL) block copolymer based on a disulfide-linked, novel biodegradable catiomer bearing a PEG-sheddable shell was developed to avoid "PEG dilemma" in nanoparticle intracellular tracking of PEG-PLL where PEG was nondegradable. However, PEG-SS-PLL catiomers have not been used to deliver small interfering VEGF RNA (siVEGF) in antiangiogenesis gene therapy. In this study, we aimed to investigate whether this novel biodegradable catiomer can deliver siVEGF into cancer cells and at the same time have an antitumor effect in a xenograft mouse model. It was found that PEG-SS-PLL efficiently delivered siVEGF with negligible cytotoxicity, and significantly decreased the expression of VEGF at both the messenger-RNA and protein levels both in vitro and in vivo, and thus tumor growth was inhibited. Our findings demonstrated that PEG-SS-PLL/siVEGF could potentially be applied to antiangiogenesis gene therapy for hepatocellular carcinoma.

Europium-phenolic network coated BaGdF5 nanocomposites for tri-modal computed tomography/magnetic resonance/luminescence imaging

Multifunctional nanocomposites based on BaGdF₅ nanoparticles (NPs) and metal phenolic network (MPN) have been engineered as novel contrast agents for potential applications in X-ray computed tomography, magnetic resonance and luminescence imaging. The BaGdF₅@MPN nanocomposites were synthesized at room temperature by coating BaGdF₅ NPs with europium-phenolic network, which was obtained by the coordination of europium (III) with tannic acid (TA). The in vitro cytotoxicity assays against HepG2 cells revealed that the BaGdF₅@MPN nanocomposites presented better cytocompatibility and lower cytotoxity than pure BaGdF₅ NPs. In addition, vivid red and green luminescence can be observed by confocal laser scanning microscope (CLSM) from the BaGdF₅@MPN nanocomposites laden HepG2 cells under the excitation of UV (390 nm) and visible light (440 nm), respectively. The longitudinal relaxivity value (r₁) of the nanocomposites was 2.457 mM^-1s^-1. Moreover, the nanocomoposites exhibited X-ray computed tomography (CT) and T₁-weighted magnetic resonance (MR) imaging capacities, and the intensities of the enhanced signals of in vitro CT and MR images were proportional to the concentrations of the nanocomposites. These results indicated that the as-prepared BaGdF₅@MPN nanocomposites are promising contrast agents for CT/MR/luminescence imaging.

Novel, nano-sized, liposome-encapsulated polyamidoamine dendrimer derivatives facilitate tumour targeting by overcoming the polyethylene glycol dilemma and integrin saturation obstacle

Drug delivery systems (DDSs) commonly employ arginine-glycine-aspartic acid (RGD) peptides with polyethylene glycol (PEG)-dependent enhanced permeability and retention (EPR) effect to optimise tumour-targeting. However, the PEG dilemma and integrin saturation obstacle are major challenges. To address these issues, we constructed a novel, nano-sized DDS by encapsulating doxorubicin (DOX)-loaded folic acid derivatives of polyamidoamine dendrimer (PAMAM G5.0) in cyclic RGD-tyrosine-lysine pentapeptide (c[RGDyK])-modified liposomes (RGD-SL[FND/DOX]), prepared using thin-film hydration, film-dispersion and hydration-sonication. The liposomes were PEGylated, sterically stabilised and pH-sensitive. In vitro, RGD-SL[FND/DOX] showed pH-sensitive holistic FND/DOX release, and pH-dependent uptake and cytotoxicity in human cancer KB cells. At pH 7.4, RGD-SL[FND/DOX] demonstrated greater cellular uptake and cytotoxicity than relevant control formulations (except FND/DOX) did, although this advantage disappeared at pH 6.5. In vivo, RGD-SL[FND/DOX] inhibited S180 sarcoma xenografted tumour growth in Kunming mice more effectively than FND/DOX did. These findings demonstrate the feasibility of constructing double-stage tumour-targeting nano-sized DDSs such as RGD-SL[FND/DOX]. c[RGDyK] and the EPR effect, facilitated by the particle size (about 110 nm) and PEGylation, helped to target the DDS to the tumour tissue, while the subsequent pH-dependent release of FND/DOX and folic acid-mediated endocytosis specifically targeted the tumour cells, thereby overcoming the PEG dilemma and integrin saturation obstacle.