Self-assembly nanomicelles based on cationic mPEG-PLA-b-Polyarginine(R15) triblock copolymer for siRNA delivery

PEGylated and Functionalized Aliphatic Polycarbonate Polyplex Nanoparticles for Intravenous Administration of HDAC5 siRNA in Cancer Therapy

Guanidine and morpholine functionalized aliphatic polycarbonate polymers are able to deliver efficiently histone deacetylase 5 (HDAC5) siRNA into the cytoplasm of cancer cells in vitro leading to a decrease of cell proliferation were previously developed. To allow these biodegradable and biocompatible polyplex nanoparticles to overcome the extracellular barriers and be effective in vivo after an intravenous injection, polyethylene glycol chains (PEG₇₅₀ or PEG₂₀₀₀) were grafted on the polymer structure. These nanoparticles showed an average size of about 150 nm and a slightly positive ζ-potential with complete siRNA complexation. Behavior of PEGylated and non-PEGylated polyplexes were investigated in the presence of serum, in terms of siRNA complexation (fluorescence correlation spectroscopy), size (dynamic light scattering and single-particle tracking), interaction with proteins (isothermal titration calorimetry) and cellular uptake. Surprisingly, both PEGylated and non-PEGylated formulations presented relatively good behavior in the presence of fetal bovine serum (FBS). Hemocompatibility tests showed no effect of these polyplexes on hemolysis and coagulation. In vivo biodistribution in mice was performed and showed a better siRNA accumulation at the tumor site for PEGylated polyplexes. However, cellular uptake in protein-rich conditions showed that PEGylated polyplex lost their ability to interact with biological membranes and enter into cells, showing the importance to perform in vitro investigations in physiological conditions closed to in vivo situation. In vitro, the efficiency of PEGylated nanoparticles decreases compared to non-PEGylated particles, leading to the loss of the antiproliferative effect on cancer cells.

Co-Assembly of Heparin and Polypeptide Hybrid Nanoparticles for Biomimetic Delivery and Anti-Thrombus Therapy

Biomimetic delivery carriers using polypeptide/heparin hybrid nanoparticles that are adsorbed onto red blood cells for extended blood circulation time have been developed. This might open up an avenue to promote the innovations and advances of biomimetic, stimuli-responsive drug delivery, especially for the site-specific treatment of intravascular diseases such as thrombosis.

Distinctive polymer micelle designed for siRNA delivery and reversal of MDR1 gene-dependent multidrug resistance

P-glycoprotein (P-gp) plays an importantrole in multidrug resistance (MDR), proved to be one of the major obstacles in cancer chemotherapy. Cationic polymers could specifically deliver siRNA to tumor cells and thus reverse MDR by the downregulation of P-gp. In this study, a triblock copolymer micelle was prepared based on the polymer of N-succinyl-chitosan-poly-l-lysine-palmitic acid (NSC-PLL-PA) to deliver siRNA-P-gp (siRNA-micelle) or doxorubicin (Dox-micelle). The resulting micelle exhibited an efficient binding ability for siRNA and high encapsulation efficiency for Dox, with an average particle size of ∼170 nm. siRNA-micelle and Dox-micellewere instable at low pH, thereby enhancing tumor accumulation and intracellular release of the encapsulated siRNA and Dox. siRNA-micelle micelles could enhance the knockdown efficacy of siRNA by improving the transfection efficiency, downregulating P-gp expression, and passing the drug efflux transporters, thereby improving the therapeutic effects of Dox-micelle. However, P-gp could transfer from HepG2/ADM to HepG2 cells independent of the expression of mdr1, and the acquired resistance could permit tumor cells to survive and develop intrinsic P-gp-mediated resistance, thereby limiting the desired efficiency of chemotherapeutics. This study demonstrated the effectiveness of siRNA-micelle for tumor-targeted delivery, MDR reversal, and provided an effective strategy for the treatment of cancers that develop MDR. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2093-2106, 2017.

Microfluidics-mediated assembly of functional nanoparticles for cancer-related pharmaceutical applications

The controlled synthesis of functional nanoparticles with tunable structures and properties has been extensively investigated for cancer treatment and diagnosis. Among a variety of methods for fabrication of nanoparticles, microfluidics-based synthesis enables enhanced mixing and precise fluidic modulation inside microchannels, thus allowing for the flow-mediated production of nanoparticles in a controllable manner. This review focuses on recent advances of using microfluidic devices for the synthesis of drug-loaded nanoparticles with specific characteristics (such as size, composite, surface modification, structure and rigidity) for enhanced cancer treatment and diagnosis as well as to investigate the bio-nanoparticle interaction. The discussion on microfluidics-based synthesis may shed light on the rational design of functional nanoparticles for cancer-related pharmaceutical applications.

A comparison of immunotoxic effects of nanomedicinal products with regulatory immunotoxicity testing requirements

Nanomaterials (NMs) are attractive for biomedical and pharmaceutical applications because of their unique physicochemical and biological properties. A major application area of NMs is drug delivery. Many nanomedicinal products (NMPs) currently on the market or in clinical trials are most often based on liposomal products or polymer conjugates. NMPs can be designed to target specific tissues, eg, tumors. In virtually all cases, NMPs will eventually reach the immune system. It has been shown that most NMs end up in organs of the mononuclear phagocytic system, notably liver and spleen. Adverse immune effects, including allergy, hypersensitivity, and immunosuppression, have been reported after NMP administration. Interactions of NMPs with the immune system may therefore constitute important side effects. Currently, no regulatory documents are specifically dedicated to evaluate the immunotoxicity of NMs or NMPs. Their immunotoxicity assessment is performed based on existing guidelines for conventional substances or medicinal products. Due to the unique properties of NMPs when compared with conventional medicinal products, it is uncertain whether the currently prescribed set of tests provides sufficient information for an adequate evaluation of potential immunotoxicity of NMPs. The aim of this study was therefore, to compare the current regulatory immunotoxicity testing requirements with the accumulating knowledge on immunotoxic effects of NMPs in order to identify potential gaps in the safety assessment. This comparison showed that immunotoxic effects, such as complement activation-related pseudoallergy, myelosuppression, inflammasome activation, and hypersensitivity, are not readily detected by using current testing guidelines. Immunotoxicity of NMPs would be more accurately evaluated by an expanded testing strategy that is equipped to stratify applicable testing for the various types of NMPs.

Efficient siRNA Delivery Using Novel Cell-Penetrating Peptide-siRNA Conjugate-Loaded Nanobubbles and Ultrasound

Because of the absence of tolerable and effective carriers for in vivo delivery, the applications of small interfering RNA (siRNA) in the clinic for therapeutic purposes have been limited. In this study, development of a novel siRNA delivery system based on ultrasound-sensitive nanobubbles (NBs, nano-sized echogenic liposomes) and cell-permeable peptides (CPPs) is described. A CPP-siRNA conjugate was entrapped in an NB, (CPP-siRNA)-NB, and the penetration of CPP-siRNA was temporally masked; local ultrasound stimulation triggered the release of CPP-siRNA from the NBs and activated its penetration. Subsequent research revealed that the (CPP-siRNA)-NBs had a mean particle size of 201 ± 2.05 nm and a siRNA entrapment efficiency >85%. In vitro release results indicated that >90% of the encapsulated CPP-siRNA was released from NBs in the presence of ultrasound, whereas <1.5% (30 min) was released in the absence of ultrasound. Cell experiments indicated higher cellular CPP-siRNA uptake of (CPP-siRNA)-NBs with ultrasound among the various formulations in human breast adenocarcinoma cells (HT-1080). Additionally, after systemic administration in mice, (CPP-siRNA)-NBs accumulated in the tumor, augmented c-myc silencing and delayed tumor progression. In conclusion, the application of (CPP-siRNA)-NBs with ultrasound may constitute an approach to selective targeted delivery of siRNA.

Reducible Micelleplexes are Stable Systems for Anti-miRNA Delivery in Cerebrospinal Fluid

Glioblastoma multiforme (GBM) and other central nervous system (CNS) cancers have poor long-term prognosis, and there is a significant need for improved treatments. GBM initiation and progression are mediated, in part, by microRNA (miRNA), which are endogenous posttranscriptional gene regulators. Misregulation of miRNAs is a potential target for therapeutic intervention in GBM. In this work, a micelle-like nanoparticle delivery system based upon the block copolymer poly(ethylene glycol-b-lactide-b-arginine) was designed with and without a reducible linkage between the lactide and RNA-binding peptide, R15, to assess the ability of the micelle-like particles to disassemble. Using confocal live cell imaging, intracellular dissociation was pronounced for the reducible micelleplexes. This dissociation was also supported by higher efficiency in a dual luciferase assay specific for the miRNA of interest, miR-21. Notably, micelleplexes were found to have significantly better stability and higher anti-miRNA activity in cerebrospinal fluid than in human plasma, suggesting an advantage for applying micelleplexes to CNS diseases and in vivo CNS therapeutics. The reducible delivery system was determined to be a promising delivery platform for the treatment of CNS diseases with miRNA therapy.

Polymer Nanoparticles Modified with Photo- and pH-Dual-Responsive Polypeptides for Enhanced and Targeted Cancer Therapy

The cationic nature of cell penetrating peptides (CPPs) and their absence of cell selectivity restrains their applications in vivo. In this work, polymer nanoparticles (NPs) modified with photo- and pH-responsive polypeptides (PPPs) were successfully developed and respond to near-infrared (NIR) light illumination at the tumor site and a lowered tumor extracellular pH (pHe). In PPPs, the internalization function of CPPs (positively charged) is quenched by a pH-sensitive inhibitory peptide (negatively charged), which is linked via a photocleavable group. Small interfering RNA (siRNA) was loaded into NPs by a double-emulsion technique. In vivo experiments included siRNA loading, cellular uptake, cell apoptosis, siRNA transfection, tumor targeting delivery, and the in vivo antitumor efficacy. Results showed that the prepared PPP-NPs could selectively accumulate at the tumor sites and internalized into the tumor cells by the NIR light illumination and the lowered pHe at the tumor site. These studies demonstrated that PPP-NPs are a promising carrier for future tumor gene delivery.

Binary-copolymer system base on low-density lipoprotein-coupled N-succinyl chitosan lipoic acid micelles for co-delivery MDR1 siRNA and paclitaxel, enhances antitumor effects via reducing drug

The development of effective and stable carriers of small interfering RNA (siRNA) is important for treating cancer with multidrug resistance (MDR). We developed a new gene and drug co-delivery system and checked its characteristics. Low-density lipoprotein (LDL) was coupled with N-succinyl chitosan (NSC) Lipoic acid (LA) micelles and co-delivered MDR1 siRNA and paclitaxel (PTX-siRNA/LDL-NSC-LA) to enhance antitumor effects by silencing the MDR gene of tumors (Li et al., Adv Mater 2014;26:8217-8224). In our study, we developed a new type of containing paclitaxel-loaded micelles and siRNA-loaded LDL nanoparticle. This "binary polymer" is pH and reduction dual-sensitive core-crosslinked micelles. PTX-siRNA/LDL-NSC-LA had an average particle size of (171.6 ± 6.42) nm, entrapment efficiency of (93.92 ± 1.06) %, and drug-loading amount of (12.35% ± 0.87) %. In vitro, MCF-7 cells, high expressed LDL receptor, were more sensitive to this delivery system than to taxol^® and cell activity was inhibited significantly. Fluorescence microscopy showed that PTX-siRNA/LDL-NSC-LA was uptaken very conveniently and played a key role in antitumor activity. PTX-siRNA/LDL-NSC-LA protected the siRNA from degradation by macrophage phagocytosis and evidently down-regulated the level of mdr1 mRNA as well as the expression of P-gp. We tested the target ability of PTX-siRNA/LDL-NSC-LA in vivo in tumor-bearing nude mice. Results showed that this system could directly deliver siRNA and PTX to cancer cells. Thus, new co-delivering siRNA and antitumor drugs should be explored for solving MDR in cancer. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1114-1125, 2017.

Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery

A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin.

Cell-penetrating peptide-siRNA conjugate loaded YSA-modified nanobubbles for ultrasound triggered siRNA delivery

Due to the absence of effective in vivo delivery systems, the employment of small interference RNA (siRNA) in the clinic has been hindered. In this paper, a new siRNA targeting system for EphA2-positive tumors was developed, based on ultrasound-sensitive nanobubbles (NBs) and cell-permeable peptides (CPPs). Here, a CPP-siRNA conjugate (CPP-siRNA) was entrapped in an ephrin mimetic peptide (YSA peptide)-modified NB (CPP-siRNA/YSA-NB) and the penetration of the CPP-siRNA was temporally masked; local ultrasound stimulation triggered the release of CPP-siRNA from the NBs and activated its penetration. Subsequent research demonstrated that the CPP-siRNA/YSA-NBs had particle sizes of approximately 200 nm and a siRNA entrapment efficiency of more than 85%. The in vitro release results showed that over 90% of the encapsulated CPP-siRNA released from the NBs in the presence of ultrasound, while less than 1.5% of that (30 min) released without ultrasound. Cell experiments showed a the higher CPP-siRNA cellular uptake of CPP-siRNA/YSA-NB among the various formulations in human breast adenocarcinoma cells (MCF-7, EphA2 positive cells). Additionally, after systemic administration in mice, CPP-siRNA/YSA-NB accumulated in the tumor, augmented c-Myc silencing and delayed tumor progression. In conclusion, the application of CPP-siRNA/YSA-NB with ultrasound may provide a strategy for the selective and efficient delivery of siRNA.

Cell-penetrating peptide-doxorubicin conjugate loaded NGR-modified nanobubbles for ultrasound triggered drug delivery

A new drug-targeting system for CD13(+) tumors has been developed, based on ultrasound-sensitive nanobubbles (NBs) and cell-permeable peptides (CPPs). Here, the CPP-doxorubicin conjugate (CPP-DOX) was entrapped in the asparagine-glycine-arginine (NGR) peptide modified NB (CPP-DOX/NGR-NB) and the penetration of CPP-DOX was temporally masked; local ultrasound stimulation could trigger the CPP-DOX release from NB and activate its penetration. The CPP-DOX/NGR-NBs had particle sizes of about 200 nm and drug entrapment efficiency larger than 90%. In vitro release results showed that over 85% of the encapsulated DOX or CPP-DOX would release from NBs in the presence of ultrasound, while less than 1.5% of that (30 min) without ultrasound. Cell experiments showed the higher cellular CPP-DOX uptake of CPP-DOX/NGR-NB among the various NB formulations in Human fibrosarcoma cells (HT-1080, CD13(+)). The CPP-DOX/NGR-NB with ultrasound treatment exhibited an increased cytotoxic activity than the one without ultrasound. In nude mice xenograft of HT-1080 cells, CPP-DOX/NGR-NB with ultrasound showed a higher tumor inhibition effect (3.1% of T/C%, day 24), longer median survival time (50 days) and excellent body safety compared with the normal DOX injection group. These results indicate that the constructed vesicle would be a promising drug delivery system for specific cancer treatment.

Charged group surface accessibility determines micelleplexes formation and cellular interaction

Micelleplexes are a class of nucleic acid carriers that have gained acceptance due to their size, stability, and ability to synergistically carry small molecules. MicroRNAs (miRNAs) are small non-coding RNA gene regulator that is consists of 19-22 nucleotides. Altered expression of miRNAs plays an important role in many human diseases. Using a model 22-nucleotide miRNA sequence, we investigated the interaction between charged groups on the micelle surface and miRNA. The model micelle system was formed from methoxy-poly(ethylene glycol)-b-poly(lactide) (mPEG-PLA) mixed with methoxy-poly(ethylene glycol)-b-poly(lactide)-b-oligoarginine (mPEG-PLA-Rx, x = 8 or 15). Surface properties of the micelles were varied by controlling the oligoarginine block length and conjugation density. Micelles were observed to have a core-shell conformation in the aqueous environment where the PLA block constituted the hydrophobic core, mPEG and oligoarginine formed a hydrophilic corona. Significantly different thermodynamic behaviors were observed during the interaction of single stranded miRNA with micelles of different surface properties, and the resulting micelleplexes mediated substantial cellular association. Depending upon the oligoarginine length and density, micelles exhibited miRNA loading capacity directly related to the presentation of charged groups on the surface. The effect of charged group accessibility of cationic micelle on micelleplex properties provides guidance on future miRNA delivery system design.

Microfluidic synthesis of rigid nanovesicles for hydrophilic reagents delivery

We present a hollow-structured rigid nanovesicle (RNV) fabricated by a multi-stage microfluidic chip in one step, to effectively entrap various hydrophilic reagents inside, without complicated synthesis, extensive use of emulsifiers and stabilizers, and laborious purification procedures. The RNV contains a hollow water core, a rigid poly (lactic-co-glycolic acid) (PLGA) shell, and an outermost lipid layer. The formation mechanism of the RNV is investigated by dissipative particle dynamics (DPD) simulations. The entrapment efficiency of hydrophilic reagents such as calcein, rhodamine B and siRNA inside the hollow water core of RNV is ≈90 %. In comparison with the combination of free Dox and siRNA, RNV that co-encapsulate siRNA and doxorubicin (Dox) reveals a significantly enhanced anti-tumor effect for a multi-drug resistant tumor model.

Folate-decorated hydrophilic three-arm star-block terpolymer as a novel nanovehicle for targeted co-delivery of doxorubicin and Bcl-2 siRNA in breast cancer therapy

To minimize the side effects and enhance the efficiency of chemotherapy, a novel folate-decorated hydrophilic cationic star-block terpolymer, [poly(l-glutamic acid γ-hydrazide)-b-poly(N,N-dimethylaminopropyl methacrylamide)]3-g-poly(ethylene glycol) ((PGAH-b-PDMAPMA)3-g-PEG), with disulfide linkages between the PEG and PDMAPMA blocks, was developed for targeted co-delivery of doxorubicin and Bcl-2 small interfering RNA (siRNA) into breast cancer cells. The terpolymer was synthesized by a combination of ring-opening polymerization, reversible addition-fragmentation chain transfer polymerization, PEGylation and hydrazinolysis. The chemical structures of the polymers were confirmed by (1)H-NMR analysis. The terpolymer could conjugate doxorubicin via an acid-labile hydrazone linkage and simultaneously efficiently complex siRNA through electrostatic interaction at N/P ratios of ⩾4:1 to form "two-in-one" nanomicelleplexes, which displayed a spherical shape and had an average size of 101.3 nm. The doxorubicin loading efficiency and content were 61.0 and 13.23%, respectively. The cytotoxicity, drug release profile, targeting ability, cellular uptake and intracellular distribution of the nanomicelleplexes were evaluated in vitro. We found that the release behaviors of doxorubicin and siRNA had a pH/reduction dual dependency. They were released faster under reductive acidic conditions (pH 5.0, glutathione: 10mM) than under physiological conditions (pH 7.4). The folate-decorated nanomicelleplexes could deliver doxorubicin and Bcl-2 siRNA more efficiently into the same MCF-7 cell and exhibited a higher cytotoxicity than non-targeted nanomicelleplexes. These results indicate that the terpolymer could act as an efficient vehicle for targeted intracellular co-delivery of doxorubicin and therapeutic siRNA in cancer therapy.

Combined anti-Galectin-1 and anti-EGFR siRNA-loaded chitosan-lipid nanocapsules decrease temozolomide resistance in glioblastoma: in vivo evaluation

Glioblastoma is the most frequent primary malignant brain tumor in adults. Despite treatments including surgery, radiotherapy and chemotherapy by oral Temozolomide (TMZ), the prognosis of patients with glioblastoma remains very poor. This is partly due to the resistance of malignant cells to therapy particularly TMZ. Overexpression of epidermal growth factor receptor (EGFR) and Galectin-1 by tumor cells significantly contributes to TMZ resistance. The purpose of this study was to evaluate in vivo, the effect of local administration by convection enhanced delivery (CED) of the anti-EGFR and anti-Galectin-1 siRNAs administered separately or in combination on (i) the survival of nude mice-bearing orthotopic U87MG glioblastoma cells and on (ii) the EGFR and Galectin-1 expression in excised U87MG tumor tissue. Both siRNAs were carried by chitosan lipid nanocapsules (LNCs). Survival of mice treated 14 days after tumor implantation by the combination of anti-EGFR and anti-Galectin-1 siRNAs and TMZ (40 mg/kg) was significantly increased compared to animals treated by single anti-EGFR or anti-Galectin-1 siRNAs carried by chitosan-LNCs. This was confirmed by a decreased EGFR and Galectin-1 expression at the protein level in excised U87MG tumor tissue, 8 days post-transfection, visualized by immunofluorescence. This study demonstrates the potential of our strategy in glioblastoma therapy.

Peptides used in the delivery of small noncoding RNA

RNA interference (RNAi) is an endogenous process in which small noncoding RNAs, including small interfering RNAs (siRNAs) and microRNAs (miRNAs), post-transcriptionally regulate gene expressions. In general, siRNA and miRNA/miRNA mimics are similar in nature and activity except their origin and specificity. Although both siRNAs and miRNAs have been extensively studied as novel therapeutics for a wide range of diseases, the large molecular weight, anionic surface charges, instability in blood circulation, and intracellular trafficking to the RISC after cellular uptake have hindered the translation of these RNAs from bench to clinic. As a result, a great variety of delivery systems have been investigated for safe and effective delivery of small noncoding RNAs. Among these systems, peptides, especially cationic peptides, have emerged as a promising type of carrier due to their inherent ability to condense negatively charged RNAs, ease of synthesis, controllable size, and tunable structure. In this review, we will focus on three major types of cationic peptides, including poly(l-lysine) (PLL), protamine, and cell penetrating peptides (CPP), as well as peptide targeting ligands that have been extensively used in RNA delivery. The delivery strategies, applications, and limitations of these cationic peptides in siRNA/miRNA delivery will be discussed.

Rational modification of oligoarginine for highly efficient siRNA delivery: structure-activity relationship and mechanism of intracellular trafficking of siRNA

Recently, cell-penetrating peptides (CPPs) have received much attention for cellular delivery of therapeutic molecules. However, in the case of CPPs as carriers for siRNA delivery, their utility is often restricted by low cellular uptake and/or entrapment in endosomes. Here, in order to deliver siRNAs with high efficiency, oligoarginine, a prominent member in CPPs, is rationally modified with oligohistidine and stearyl moieties (STR-) by fully taking into account the formation of nanoparticles, uptake and intracellular trafficking. We show that when the ratio of histidine/arginine in a peptide sequence is >1.5, pronounced gene silencing is induced. Following this rule, STR-HnR8 (n=16 and 20) are developed, which show a high knockdown efficiency rarely reported before. Finally, we find that endosomal escape of siRNA induced by stearylated and oligohistidylated oligoarginine is only from "proton-sponge" effect. Taken together, our results suggest a new strategy for the improvement of CPP-based siRNA delivery systems.

FROM THE CLINICAL EDITOR

This study present a novel cell penetrating peptide-based siRNA delivery system utilizing modified oligo-arginine demonstrating a successful siRNA delivery approach.

Matrix metalloproteinase 2-responsive micelle for siRNA delivery

Systemic delivery of small interfering RNA (siRNA) into cancer cells remains the major obstacle to siRNA drug development. An ideal siRNA delivery vehicle for systemic administration should have long circulation time in blood, accumulate at tumor site, and sufficiently internalize into cancer cells for high-efficiency of gene silence. Herein, we report a core-shell Micelleplex delivery system that made from block copolymer bearing poly(ethylene glycol) (PEG), matrix metalloproteinase 2 (MMP-2)-degradable peptide PLG*LAG, cationic cell penetrating peptide polyarginine r9 and poly(ε-caprolactone) (PCL) for siRNA delivery. We show clear evidences in vitro and in vivo to prove that the micelle carrying siRNA can circulate enough time in blood, enrich accumulation at tumor sites, shed the PEG layer when triggered by tumor overexpressing MMP-2, and then the exposing cell penetrating peptide r9 enhanced cellular uptake of siRNA. Accordingly, this design strategy enhances the inhibition of breast tumor growth following systemic injection of this system carrying siRNA against Polo-like kinase 1, which demonstrating this Micelleplex can be a potential delivery system for systemic siRNA delivery in cancer therapy.

Self-assembled nanoparticles based on the c(RGDfk) peptide for the delivery of siRNA targeting the VEGFR2 gene for tumor therapy

The clinical application of small interfering RNA (siRNA) has been restricted by their poor intracellular uptake, low serum stability, and inability to target specific cells. During the last several decades, a great deal of effort has been devoted to exploring materials for siRNA delivery. In this study, biodegradable, tumor-targeted, self-assembled peptide nanoparticles consisting of cyclo(Arg–Gly–Asp–d–Phe–Lys)-8–amino–3,6–dioxaoctanoic acid–β–maleimidopropionic acid (hereafter referred to as RPM) were found to be an effective siRNA carrier both in vitro and in vivo. The nanoparticles were characterized based on transmission electron microscopy, circular dichroism spectra, and dynamic light scattering. In vitro analyses showed that the RPM/VEGFR2-siRNA exhibited negligible cytotoxicity and induced effective gene silencing. Delivery of the RPM/VEGFR2 (zebrafish)-siRNA into zebrafish embryos resulted in inhibition of neovascularization. Administration of RPM/VEGFR2 (mouse)-siRNA to tumor-bearing nude mice led to a significant inhibition of tumor growth, a marked reduction of vessels, and a down-regulation of VEGFR2 (messenger RNA and protein) in tumor tissue. Furthermore, the levels of IFN-α, IFN-γ, IL-12, and IL-6 in mouse serum, assayed via enzyme-linked immunosorbent assay, did not indicate any immunogenicity of the RPM/VEGFR2 (mouse)-siRNA in vivo. In conclusion, RPM may provide a safe and effective delivery vector for the clinical application of siRNAs in tumor therapy.

Poly(styrene)-b-poly(DL-lactide) copolymer-based nanoparticles for anticancer drug delivery

Poly(styrene)-b-poly(DL-lactide) (PS-PDLLA) copolymer-based nanoparticles (NPs) of a narrow size distribution, negative zeta potential, and spherical shape were fabricated for the delivery of docetaxel (DCT). The particle size was consistently maintained in serum for 24 hours and a sustained drug release pattern was observed for 10 days in the tested formulations. The cytotoxicity of the developed blank NPs was negligible in prostate cancer (PC-3) cells. Cellular uptake and distribution of the constructed NPs containing a hydrophobic fluorescent dye was monitored by confocal laser scanning microscopy (CLSM) for 24 hours. Anti-tumor efficacy of the PS-PDLLA/DCT NPs in PC-3 cells was significantly more potent than that of the group treated with commercially available DCT, Taxotere (P<0.05). Blood biochemistry tests showed that no serious toxicity was observed with the blank NPs in the liver and kidney. In a pharmacokinetic study of DCT in rats, in vivo clearance of PS-PDLLA/DCT NPs decreased while the half-life in blood increased compared to the Taxotere-treated group (P<0.05). The PS-PDLLA NPs are expected to be a biocompatible and efficient nano-delivery system for anticancer drugs.

Novel self-assembled micelles based on palmitoyl-trimethyl-chitosan for efficient delivery of harmine to liver cancer

BACKGROUND

Polymeric micelles is a safe and effective delivery system, which belong to the targeted delivery system (TDS). An anticancer drug, harmine(HM) is a hydrophobic drug with much adverse effects when used for treatment of liver cancer. Chitosan (CS) is a polysaccharide and can be modified to be an amphiphilic polmer which could self-assemble into micelles and be applied for delivery of hydrophobic drugs.

OBJECTIVES

To synthesize three kinds of novel biodegradable polymers, designated as palmitoyl-trimethyl-CS (TPCS)1, TPCS2 and Lac-TPCS2, and investigate their efficiency and mechanism of delivery HM to liver tumors in vitro and in viro.

RESULTS

The self-assembled micelles presented satisfactory particle size (∼ 200 nm) and drug release characteristics in vitro. It's proved that Lac-TPCS2/HM may enter HepG2 cell through endocytosis. Antitumor experiments in vivo revealed that Lac-TPCS2/HM could significantly inhibit tumor growth and extend the lifetime of mice bearing H22 tumors after intravenous administration. Subsequently in vivo near-infrared fluorescence imaging results demonstrated a satisfactory liver tumor-targeting effect of Lac-TPCS2/HM.

CONCLUSION

Three novel polymers hold great potential in the development of nanomedicine for treatment of liver tumors, in particular Lac-TPCS2 exhibits the greatest antitumor potential through active target effect.

Nanotechnology in diagnostics and therapeutics for gastrointestinal disorders

This review describes the state of the art in nanoparticle and nanodevice applications for medical diagnosis and disease treatment. Nanodevices, such as cantilevers, have been integrated into high-sensitivity disease marker diagnostic detectors and devices, are stable over long periods of time, and display reliable performance properties. Nanotechnology strategies have been applied to therapeutic purposes as well. For example, nanoparticle-based delivery systems have been developed to protect drugs from degradation, thereby reducing the required dose and dose frequency, improving patient comfort and convenience during treatment, and reducing treatment expenses. The main objectives for integrating nanotechnologies into diagnostic and therapeutic applications in the context of intestinal diseases are reviewed.

Layer-by-layer nanoparticles for systemic codelivery of an anticancer drug and siRNA for potential triple-negative breast cancer treatment

A single nanoparticle platform has been developed through the modular and controlled layer-by-layer process to codeliver siRNA that knocks down a drug-resistance pathway in tumor cells and a chemotherapy drug to challenge a highly aggressive form of triple-negative breast cancer. Layer-by-layer films were formed on nanoparticles by alternately depositing siRNA and poly-l-arginine; a single bilayer on the nanoparticle surface could effectively load up to 3500 siRNA molecules, and the resulting LbL nanoparticles exhibit an extended serum half-life of 28 h. In animal models, one dose via intravenous administration significantly reduced the target gene expression in the tumors by almost 80%. By generating the siRNA-loaded film atop a doxorubicin-loaded liposome, we identified an effective combination therapy with siRNA targeting multidrug resistance protein 1, which significantly enhanced doxorubicin efficacy by 4 fold in vitro and led to up to an 8-fold decrease in tumor volume compared to the control treatments with no observed toxicity. The results indicate that the use of layer-by-layer films to modify a simple liposomal doxorubicin delivery construct with a synergistic siRNA can lead to significant tumor reduction in the cancers that are otherwise nonresponsive to treatment with Doxil or other common chemotherapy drugs. This approach provides a potential strategy to treat aggressive and resistant cancers, and a modular platform for a broad range of controlled multidrug therapies customizable to the cancer type in a singular nanoparticle delivery system.

Development of streptavidin-based nanocomplex for siRNA delivery

In our previous study, we have identified a PCBP2 siRNA that exhibits antifibrotic activity in rat hepatic stellate cells (HSCs) by inhibition of αCP2, a protein responsible for stabilization of the collagen α1 (I) mRNA in alcoholic liver fibrosis. This study aims to develop a streptavidin-based nanocomplex that can efficiently deliver the PCBP2 siRNA to HSCs. Biotin-siRNA and biotin-cholesterol were mixed with streptavidin to form the streptavidin-biotin complex, which was further condensed electrostatically with positively charged protamine to form the final multicomponent siRNA nanocomplex in the size range of 150-250 nm. The siRNA nanocomplex does not induce cytotoxicity in rat HSCs as compared to commercially available transfection agents. The cellular uptake efficiency of the siRNA nanocomplex is higher in rat HSCs than other cell lines, such as Caco-2 and PC-3, indicating that receptor-mediated endocytosis mainly contributes to the cellular uptake of the siRNA nanocomplex. The siRNA nanocomplex exhibits more than 85% silencing effect on the PCBP2 mRNA in HSCs. Stability study indicates that the nanocomplex can efficiently protect siRNA from degradation in the serum. The streptavidin-based multicomponent siRNA nanocomplex provides a promising strategy to deliver the PCBP2 siRNA to HSCs. Moreover, the nanocomplex can be used as a platform for other diseases by changing the siRNA sequence and targeting ligand.

Nanostructure formation and transition from surface to bulk degradation in polyethylene glycol gels chain-extended with short hydroxy acid segments

Degradable, in situ gelling, inert hydrogels with tunable properties are very attractive as a matrix for cell encapsulation and delivery to the site of regeneration. Cell delivery is generally limited by the toxicity of gelation and degradation reactions. The objective of this work was to investigate by simulation and experimental measurement gelation kinetics and degradation rate of star acrylated polyethylene glycol (PEG) macromonomers chain-extended with short hydroxy acid (HA) segments (SPEXA) as a function of HA monomer type and number of HA repeat units. HA monomers included least hydrophobic glycolide (G), lactide (L), p-dioxanone (D), and most hydrophobic ε-caprolactone (C). Chain extension of PEG with short HA segments resulted in micelle formation for all HA types. There was a significant decrease in gelation time of SPEXA precursor solutions with HA chain-extension for all HA types due to micelle formation, consistent with the simulated increase in acrylate-acrylate (Ac-Ac) and Ac-initiator integration numbers. The hydrolysis rate of SPEXA hydrogels was strongly dependent on HA type and number of HA repeat units. SPEXA gels chain-extended with the least hydrophobic glycolide completely degraded within days, lactide within weeks, and p-dioxanone and ε-caprolactone degraded within months. The wide range of degradation rates observed for SPEXA gels can be explained by large differences in equilibrium water content of the micelles for different HA monomer types. A biphasic relationship between HA segment length and gel degradation rate was observed for all HA monomers, which was related to the transition from surface (controlled by HA segment length) to bulk (controlled by micelle equilibrium water content) hydrolysis within the micelle phase. To our knowledge, this is the first report on transition from surface to bulk degradation at the nanoscale in hydrogels.

Self-assembly cationic nanoparticles based on cholesterol-grafted bioreducible poly(amidoamine) for siRNA delivery

In this study, a series of bioreducible poly(amidoamine)s grafting different percentages of cholesterol (rPAA-Ch14: 14%, rPAA-Ch29: 29%, rPAA-Ch57: 57% and rPAA-Ch87: 87%) was synthesized and used for siRNA delivery. These amphiphilic polymers were able to self-assemble into cationic nanoparticles in aqueous solution at low concentrations. The nanoparticle formation was evidenced via cryo-transmission electron microscope (Cryo-TEM) and dynamic light scattering analysis. The average hydrodynamic size of rPAA-Ch blank nanoparticles was about 80-160 nm with zeta potential of 50-60 mV. Also, the effects of different percentages of cholesterol grafted onto rPAA on physicochemical characteristics, in vitro cytotoxicity, cellular uptake, VEGF gene silencing efficacy and translocation mechanism of rPAA-Ch/siRNA complexes were investigated. The results showed that rPAA-Ch57 polymer was not only able to form stable nanocomplexes and possess high cell uptake, but also to exhibit the best in vitro VEGF gene silencing efficacy and the best in vivo tumor growth inhibition effect when it was formulated with VEGF-siRNA. Moreover, the observations of confocal laser scanning microscope (CLSM) and the study of cholesterol competitive inhibition demonstrated that endosomal/lysosomal escape and cytoplasmic dissociation of rPAA-Ch57/siRNA complexes were dependent on the "proton sponge effect" and disulfide cleavage, following internalization with cholesterol-related endocytosis pathway and subsequent transportion into endosomes/lysosomes. These findings indicated that the rPAA-Ch57 polymer should be a promising and potent carrier for siRNA delivery.

Controlled drug release system based on cyclodextrin-conjugated poly(lactic acid)-b-poly(ethylene glycol) micelles

Cyclodextrin-conjugated poly(lactic acid)-b-poly(ethylene glycol) (β-CD-PLA-mPEG), a well-defined amphiphilic copolymer, was synthesized by controlled ring-open copolymerization and click coupling reaction, in order to obtain a biocompatible drug delivery system with controlled release profiles. The β-CD-PLA-mPEG copolymer could self-assemble in aqueous solution to form micelles with a mean particle size of 173.4 nm, which will decrease to 159.2 nm after loaded with a kind of hydrophobic drug (indomethacin, IND). The IND-loaded β-CD-PLA-mPEG micelles show spherical shape within the nano-size scale under TEM imaging. Compared with that formed by PLA-mPEG, the micelles formed by β-CD-PLA-mPEG copolymer present higher drug loading efficiency and controlled release profile of IND, especially in the control of its initial burst release. Meanwhile, β-CD-PLA-mPEG copolymer exhibits low toxicity to cells. The micelles formed by β-CD-PLA-mPEG copolymer could be a promising controlled release system for various hydrophobic drugs.

Copolymers of poly(lactic acid) and D-α-tocopheryl polyethylene glycol 1000 succinate-based nanomedicines: versatile multifunctional platforms for cancer diagnosis and therapy

INTRODUCTION

The major drawbacks associated with most of the anti-cancer drugs are their potential adverse effects. Distribution of these drugs throughout the body causes untoward adverse effects and less accumulation of drug at the site of tumors also causes decrease in therapeutic efficacy. Targeted nanomedicines are the emerging systems to improve the targetability of drug to the tumor site and to reduce the toxicity with maximum efficacy. Copolymers of poly-lactic acid (PLA) and D-α-tocopheryl polyethylene glycol 1000 succinate (Vitamin-E TPGS or TPGS) are innovative materials being actively investigated for the fabrication of non-targeted and targeted nanomedicines for diagnosis and therapy of cancer.

AREAS COVERED

In this review, different nanomedicines of copolymers such as poly-lactic acid - polyoxyethylene sorbitan monooleate (PLA - Tween® 80), poly-lactic acid - poly-ethyleneglycol (PLA-PEG), poly-lactic acid-D-α-tocopheryl polyethylene glycol 1000 succinate (PLA-TPGS) and TPGS-based nanomedicines (i.e., TPGS emulsified polymeric nanoparticles, TPGS prodrugs, TPGS liposomes, and TPGS micelles) for the diagnosis and therapy of cancer have been discussed.

EXPERT OPINION

PLA, PLA-Tween® 80, PLA-PEG, PLA-TPGS, and TPGS are the promising polymeric biomaterials well studied as cancer nanomedicines. These biomaterials have proved that they could be applied in the fabrication of multifunctional nanomedicines for the future needs in simultaneous diagnosis of cancer as well as targeted chemotherapy.