Abstract

MicroRNA-21 (miR-21) inhibition is a promising biological strategy for breast cancer therapy. However its application is limited by the lack of efficient miRNA inhibitor delivery systems. As a cationic polymer transfection material for nucleic acids, the poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer combines the high transfection efficiency of polyethylenimine (PEI) and the good biodegradability of polyllysine (PLL). In this work, PEI-PLL was successfully synthesized and confirmed to transfect plasmid and oligonucleotide more effectively than PEI in MCF-7 cells (human breast cancer cells). In this regard, two kinds of miR-21 inhibitors, miR-21 sponge plasmid DNA (Sponge) and anti-miR-21 oligonucleotide (AMO), were transported into MCF-7 cells by PEI-PLL respectively. The miR-21 expression and the cellular physiology were determined post transfection. Compared with the negative control, PEI-PLL/Sponge or PEI-PLL/AMO groups exhibited lower miR-21 expression and cell viability. The anti-tumor mechanism of PEI-PLL/miR-21 inhibitors was further studied by cell cycle and western blot analyses. The results indicated that the miR-21 inhibition could induce the cell cycle arrest in G1 phase, upregulate the expression of Programmed Cell Death Protein 4 (PDCD4) and thus active the caspase-3 apoptosis pathway. Interestingly, the PEI-PLL/Sponge and PEI-PLL/AMO also sensitized the MCF-7 cells to anti-tumor drugs, doxorubicin (DOX) and cisplatin (CDDP). These results demonstrated that PEI-PLL/Sponge and PEI-PLL/AMO complexes would be two novel and promising gene delivery systems for breast cancer gene therapy based on miR-21 inhibition.

Statement of Significance

This work was a combination of the high transfection efficiency of polyethylenimine (PEI), the good biodegradability of polyllysine (PLL) and the breast cancer-killing effect of miR-21 inhibitors. The poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer was employed as the vector of miR-21 sponge plasmid DNA (Sponge) or anti-miR-21 oligonucleotide (AMO). PEI-PLL showed more transfection efficiency and lower cytotoxicity in human breast cancer cells than PEI. Moreover, the breast cancer cells exhibited significantly lower miR-21 expression and cell viability post transfection with sponge or AMO. Interestingly, the PEI-PLL/miR-21 inhibitor complexes also sensitized the cancer cells to anti-cancer chemotherapy drugs, doxorubicin (DOX) and cisplatin (CDDP). This synergistic effect provides a good application prospect of co-delivery miR-21 inhibitors and chemical drugs in breast cancer therapy.

Abstract

A novel pH-responsive gene delivery system for tumor acidity-targeted pDNA delivery is prepared by introducing a rapid charge-conversional zwitterionic copolymer to the positive surface of PEI/pDNA complexes through electrostatic interaction. The shielding system (OEAL) consists of oligoethylenimine (OEI), poly(l-aspartate) (PBLA), and poly(l-lysine) (PLL). The charge-conversional behavior of the OEAL/PEI/DNA ternary complex is evaluated by zeta potential assay. The surface charges of the complexes can change from negative to positive in the pH range of 7.4–6.8. Under a simulative in vivo environment, OEAL/PEI/DNA exhibits promotion of cellular uptake by tumor cells and enhanced gene transfection efficiency because of its good charge-conversional properties. Antitumor experiments further show that the pH-responsive charge-conversional system can mediate a therapeutic gene that can induce tumor apoptosis (pKH3-rev-casp-3) to achieve effective tumor inhibition. Accordingly, OEAL can be regarded as a promising tumor microenvironment-sensitive gene delivery shielding system for antitumor therapy.

Statement of Significance

This manuscript focused on the novel pH-responsive gene delivery system for tumor acidity-targeted pDNA delivery. The novel system is prepared by introducing a rapid charge-conversional zwitterionic copolymer, consisting of oligoethylenimine, poly(l-aspartate) and poly(l-lysine), to the positive surface of PEI/pDNA complexes. The surface charges of the complexes can change from negative to positive from pH 7.4 to 6.8. OEAL/PEI/DNA shows promoting cellular uptake by tumor cells and enhanced gene transfection efficiency. The antitumor experiments further show that the pH responsive charge conversional system can mediate pKH3-rev-casp-3 to achieve effective tumor inhibition. Accordingly, OEAL can be regarded as a promising tumor microenvironment sensitive gene delivery shielding system for antitumor therapy.

Abstract

The metastasis of breast cancer is the leading cause of cancer death in women. In this work, an attempt to simultaneously inhibit the primary tumor growth and organ-specific metastasis by the cisplatin-loaded LHRH-modified dextran nanoparticles (Dex-SA-CDDP-LHRH) was performed in the 4T1 orthotopic mammary tumor metastasis model. With the rationally designed conjugation site of the LHRH ligand, the Dex-SA-CDDP-LHRH nanoparticles maintained the targeting function of LHRH and specifically bound to the LHRH-receptors overexpressed on the surface of 4T1 breast cancer cells. Therefore, the Dex-SA-CDDP-LHRH nanoparticles exhibited improved cellular uptake and promoted cytotoxicity, when compared with the non-targeted Dex-SA-CDDP nanoparticles. Moreover, both the non-targeted and targeted nanoparticles significantly decreased the systemic toxicity of CDDP and increased the maximum tolerated dose of CDDP from 4 to 30 mg kg⁻¹. Importantly, Dex-SA-CDDP-LHRH markedly enhanced the accumulation of CDDP in the injected primary tumor and metastasis-containing organs, and meanwhile significantly reduced the nephrotoxicity of CDDP. Dose-dependent therapeutic effects further demonstrated that the CDDP-loaded LHRH-decorated polysaccharide nanoparticles significantly enhanced the antitumor and antimetastasis efficacy, as compared to the non-targeted nanoparticles. These results suggest that Dex-SA-CDDP-LHRH nanoparticles show great potential for targeted chemotherapy of metastatic breast cancer.

Abstract

In the pursuit of new strategies for the design and synthesis of high performance, physically associated hydrogels, dynamic materials formed through electrostatic interactions can serve as a powerful model. Here, we introduce a convenient strategy to obtain biodegradable hydrogels from ABA triblock ionic polypeptides formed by mixing poly(l-glutamic acid)–block-poly(ethylene glycol)–block-poly(l-glutamic acid) (PGA–PEG–PGA) with poly(l-lysine)–block-poly(ethylene glycol)–block-poly(l-lysine) (PLL–PEG–PLL). The hydrogels showed tunable physical properties, high strength and reversible response. The reactive function groups in the ionic blocks can conjugate with oppositely charged drugs or proteins and allow for further modification. These ionic ABA triblock polyelectrolytes can also encapsulate intact cells without significantly compromising cell viability, suggesting that the hydrogels have excellent cytocompatibility. In vivo evaluation performed in rats with subcutaneous injection indicated that the gels were formed and degraded, and hematoxylin and eosin staining suggested good biocompatibility in vivo. In addition, these advantages, combined with the synthetic accessibility of the copolymer, make this cross-linking system a flexible and powerful new tool for the development of injectable hydrogels for biomedical applications.

Abstract

Two kinds of triblock poly(ethylene glycol)–polyleucine (PEG–PLeu) copolymers were synthesized through the ring-opening polymerization of l-Leu N-carboxyanhydride (NCA), or equivalent d-Leu NCA and l-Leu NCA with amino-terminated PEG as a macroinitiator. The amphiphilic copolymers spontaneously self-assembled into spherical micellar aggregations in an aqueous environment. The micelle with a racemic polypeptide core exhibited smaller critical micelle concentration and diameter compared to those with a levorotatory polypeptide core. A model anthracycline antineoplastic agent, i.e., doxorubicin (DOX), was loaded into micelles through nanoprecipitation, and the PEG–P(d,l-Leu) micelle exhibited higher drug-loading efficacy than that with a P(l-Leu) core—this difference was attributed to the flexible and compact P(l-Leu) core. Sustained in vitro DOX release from micelles with both levorotatory and racemic polypeptide cores was observed, and the DOX-loaded PEG–P(d,l-Leu) micelle exhibited a slower release rate. More interestingly, DOX-loaded micelles exhibited chirality-mediated antitumor efficacy in vitro and in vivo, which are all better than that of free DOX. Furthermore, both enhanced tumor inhibition and excellent security in vivo were confirmed by histopathological or in situ cell apoptosis analyses. Therefore, DOX-loaded PEG–PLeu micelles appear to be an interesting nanoscale polymeric formulation for promising malignancy chemotherapy.

Abstract

Herein, learning from the idea of the modular concept widely used in ship building, as a design approach that assembles some subdivided smaller modules to a specific ship, a new modular multifunctional drug delivery (MMDD) with excellent biocompatibility was directly prepared by a flexible host–guest interaction between pH-sensitive benzimidazole-graft-dextran (Dex-BM) and pre-synthesized multifunctional cyclodextrins. In this drug system, pH-sensitive Dex-BM acted as the main case and pre-synthesized multifunctional cyclodextrins were the changeable modules. To verify the feasibility of MMDD in cancer chemotherapy, doxorubicin (DOX) was used as a model drug. In vitro drug release experiments indicated that the drug released around 80% from DOX-loaded MMDD at pH 5.3, while approximately 40% of DOX released under the condition of pH 7.4. Moreover, the targeting antitumor activity of DOX-loaded MMDD was investigated in HeLa and HepG2 cells using MTT assays, confocal laser scanning microscopy and flow cytometer, which indicated that the targeted DOX-loaded MMDD provided an efficient drug delivery platform for inhibition of different cancer cells. Meantime, the incorporation of different functional modules into one system was also investigated, simultaneously exhibiting targeting and imaging property. These features suggest that this modular multifunctional drug delivery system can efficiently enhance the inhibition of cellular proliferation in vitro, and according to the needs in clinical treatment, some targeting and imaging molecules can be chosen.

Abstract

A series of biodegradable and biocompatible cationic hybrid hydrogels was developed from water-soluble arginine-based unsaturated polymer (Arg-AG) and poly(ethylene glycol) diacrylate (PEG-DA) by a photocrosslinking method. The physicochemical, mechanical and biological properties of these hydrogels were intensively examined. The hydrogels were characterized in terms of equilibrium swelling ratio (Q_eq), compression modulus and interior morphology. The effects of the chemical structure of the two Arg-AG precursors and the feed ratio of these precursors on the properties of resulting hybrid hydrogels were investigated. The crosslinking density and mechanical strength of the hybrid hydrogels increased with an increase in allylglycine (AG) content in the Arg-AG precursor, as the gelation efficiency (G_f) increased from 80% to 90%, but the swelling and pore size of the hybrid hydrogels decreased as the equilibrium swelling weight (Q_eq) decreased from 1890% to 1330% and the pore size from 28 to 22 μm. The short-term in vitro biodegradation properties of hydrogels were investigated as a function of Arg-AG chemical structures and enzymes. Hybrid hydrogels showed faster biodegradation in an enzyme solution than in a phosphate-buffered saline solution. Bovine serum albumin and insulin release profiles indicated that this cationic hydrogel system could significantly improve the sustained release of the negatively charged proteins. The cellular response of the hybrid hydrogels was preliminarily evaluated by cell attachment, encapsulation and proliferation tests using live–dead and MTT assay. The results showed that the hybrid hydrogels supported cell attachment well and were nontoxic to the cells.

No abstract is available for this article.

ABSTRACT

Abstract

Abstract

An amphiphilic anionic copolymer, methoxy poly(ethylene glycol)-b-poly(l-glutamic acid-co-l-phenylalanine) (mPEG-b-P(Glu-co-Phe)), with three functionalized domains, was synthesized and used as a nanovehicle for cationic anticancer drug doxorubicin hydrochloride (DOX·HCl) delivery via electrostatic interactions for cancer treatment. The three domains displayed distinct functions: PEG block chain for prolonged circulation; poly(phenylalanine) domain for stabilizing the nanoparticle construct through hydrophobic/aromatic interactions; and the poly(glutamic acid) domain for providing electrostatic interactions with the cationic drug to be loaded. The copolymer could self-assemble into micellar-type nanoparticles, and DOX was successfully loaded into the interior of nanoparticles by simple mixing of DOX·HCl and the copolymer in the aqueous phase. DOX-loaded mPEG-b-P(Glu-co-Phe) nanoparticles (DOX-NP) had a superior drug-loading content (DLC) (21.7%), a high loading efficiency (almost 98%) and a pH-triggered release of DOX. The size of DOX-NP was ∼140 nm, as determined by dynamic light scattering measurements and transmission electron microscopy. In vitro assays showed that DOX-NP exhibited higher cell proliferation inhibition and higher cell uptake in A549 cell lines compared with free DOX·HCl. Maximum tolerated dose (MTD) studies showed that DOX-NP demonstrated an excellent safety profile with a significantly higher MTD (15 mg DOX kg⁻¹) than that of free DOX·HCl (5 mg DOX kg⁻¹). The in vivo studies on the subcutaneous non-small cell lung cancer (A549) xenograft nude mice model confirmed that DOX-NP showed significant antitumor activity and reduced side effects, and then enhanced tumor accumulation as a result of the prolonged circulation in blood and the enhanced permeation and retention effect, compared with free DOX, indicating its great potential for cancer therapy.