Minghui Xu

Reduction/pH dual-sensitive PEGylated hyaluronan nanoparticles for targeted doxorubicin delivery.

To minimize the side effect of chemotherapy, a novel reduction/pH dual-sensitive drug nanocarrier, based on PEGylated dithiodipropionate dihydrazide (TPH)-modified hyaluronic acid (PEG-SS-HA copolymer), was developed for targeted delivery of doxorubicin (DOX) to hepatocellular carcinoma. The copolymer was synthesized by reductive amination via Schiffs base formation between TPH-modified HA and galactosamine-conjugated poly(ethylene glycol) aldehyde/methoxy poly(ethylene glycol) aldehyde. Conjugation of DOX to PEG-SS-HA copolymer was accomplished through the hydrazone linkage formed between DOX and PEG-SS-HA, and confirmed by FTIR and (1)H NMR spectra. The polymer-DOX conjugate could self-assemble into spherical nanoparticles (~150 nm), as indicated by TEM and DLS. In vitro release studies showed that the DOX-loaded nanoparticles could release DOX rapidly under the intracellular levels of pH and glutathiose. Cellular uptake experiments demonstrated that the nanoparticles could be efficiently internalized by HepG2 cells. These results indicate that the PEG-SS-HA copolymer holds great potential for targeted intracellular delivery of DOX.

Co-delivery of doxorubicin and P-glycoprotein siRNA by multifunctional triblock copolymers for enhanced anticancer efficacy in breast cancer cells

Combined treatment of chemotherapeutics and small interfering RNAs (siRNAs) is a promising therapy strategy for breast carcinoma via their synergetic effects. In this study, to improve the therapeutic effect of doxorubicin (DOX), novel triblock copolymers, folate/methoxy-poly(ethylene glycol)-block-poly(l-glutamate-hydrazide)-block-poly(N,N-dimethylaminopropyl methacrylamide) (FA/m-PEG-b-P(LG-Hyd)-b-PDMAPMA), were synthesized and used as a vehicle for the co-delivery of DOX and P-glycoprotein (P-gp) siRNA into breast cancer cells. The triblock copolymers were synthesized by a combination of ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydride using cystamine-terminated heterotelechelic PEG derivatives possessing folate or methoxy end groups (FA/m-PEG-Cys) as initiators and reversible addition-fragmentation chain transfer polymerization of N,N-dimethylaminopropyl methacrylamide followed by hydrazinolysis. The successful synthesis of the copolymers was confirmed by 1H NMR and gel permeation chromatography. DOX was covalently conjugated onto the poly(l-glutamate-hydrazide) blocks via a pH-labile hydrazone linkage, and the DOX-conjugated triblock copolymers could self-assemble into nanoparticles in aqueous solutions. P-glycoprotein (P-gp) siRNA was then bound to the cationic poly(N,N-dimethylaminopropyl methacrylamide) (PDMAPMA) blocks through an electrostatic interaction, resulting in the formation of spherical nanocomplexes with an average diameter of 196.8 nm and a zeta potential of +28.3 mV. The in vitro release behaviors of DOX and siRNA from the nanocomplexes were pH- and reduction-dependent, and the release rates were much faster under a reductive acidic condition (pH 5.0, glutathione: 10 mM) simulating the intracellular endo-lysosomal environment of cancer cells compared to physiological conditions. The fast payload release rates were closely related to both the glutathione-triggered detachment of PEG blocks from the nanocomplex surface and the pH-sensitive cleavage of hydrazone linkages. FA-decorated nanocomplexes showed higher cellular uptake efficiency and cytotoxicity against MCF-7 cells than FA-free nanocomplexes, as confirmed by confocal laser scanning microscopy, transmission electron microscopy, MTT and flow cytometry analyses. Our results demonstrated that the multifunctional triblock copolymer-mediated co-delivery of DOX and P-gp siRNA might be a new promising therapeutic strategy for breast cancer treatment.

Preparation and in vitro characterization of biomorphic silk fibroin scaffolds for bone tissue engineering

In bone tissue engineering, a qualified scaffold should provide a three-dimensional porous structure mimicking the extracellular matrix of bone except good biological properties. In this study, biomorphic silk fibroin (SF) scaffolds were fabricated from cane by an innovative biotemplating-negative mold process. The physicochemical properties, in vitro enzymatic degradation behavior and biocompatibility of the biomorphic SF scaffolds were investigated. The results showed that the scaffolds well inherited the original porous morphology of cane, and possessed good mechanical stability. The scaffolds had a compressive modulus of 1.56 ± 0.08 MPa and a porosity of 82.73%, and exhibited a bimodal pore size distribution (15 and 172 μm). The degradation ratio of the SF scaffolds increased with prolonging degradation time and reached 29% within 21 days when exposed to 1.0 U/mL collagenase IA. The in vitro cytocompatibility evaluation indicated that the scaffolds could support cell attachment, proliferation, and osteogenic differentiation of osteoblast-like MC3T3-E1 cells, as assessed by SEM, fluorescent staining, MTT, and ALP activity assays. The results indicated the potential of biomorphic SF scaffolds for bone tissue engineering.

A reduction-dissociable PEG-b-PGAH-b-PEI triblock copolymer as a vehicle for targeted co-delivery of doxorubicin and P-gp siRNA

To enhance the therapeutic efficacy of doxorubicin (DOX) to breast cancer cells, a multifunctional triblock copolymer, poly(ethylene glycol)-block-poly(L-glutamic acid γ-hydrazide)-block-polyethylenimine (PEG-b-PGAH-b-PEI) having a cleavable disulfide linkage between blocks, was developed as a vehicle for targeted co-delivery of DOX and P-glycoprotein (P-gp) siRNA into MCF-7/ADR cells. The PGAH blocks were used to chemically conjugate DOX molecules via hydrazone bonds, while the PEI blocks could complex siRNA through electrostatic interactions. A tumor-targeting agent, folic acid (FA), was attached to the distal ends of the PEG blocks to specifically bind to the folate receptors overexpressed in MCF-7/ADR cells. The DOX-conjugated copolymer would self-assemble in aqueous solutions into cationic nanomicelles, which could condense siRNA to form nanomicelleplexes with an average particle size of ∼194 nm and a positive zeta potential of >+10 mV. The nanomicelleplexes exhibited sustained drug release profiles, and the release rates of DOX and siRNA from the nanomicelleplexes in a reductive acidic environment (pH 5.0 + 10 mM glutathione) were much faster than those under physiological conditions (pH 7.4). FA-decorated nanomicelleplexes were more efficiently internalized by MCF-7/ADR cells via folate-receptor-mediated endocytosis and exhibited a higher cytotoxic effect on MCF-7/ADR cells in comparison with FA-undecorated nanomicelleplexes. Furthermore, the synergistic effects of DOX and P-gp siRNA in inhibiting cell proliferation and inducing apoptosis in MCF-7/ADR cells were achieved by the FA-targeted co-delivery system. The triblock copolymer itself had a low cytotoxicity. These results indicate that the triblock copolymer could serve as an ideal tumor-targeting vehicle for simultaneous delivery of drugs and siRNA in breast cancer therapy.

Stimuli-responsive terpolymer mPEG-b-PDMAPMA-b-PAH mediated co-delivery of adriamycin and siRNA to enhance anticancer efficacy

Combination of chemotherapy and small interfering RNA (siRNA)-based therapy has emerged as a promising approach for cancer treatment with the synergistic effect. In this study, a novel terpolymer methoxy poly(ethylene glycol)-block-poly(N,N-dimethylaminopropyl methacrylamide)-block-poly(acrylhydrazine) (mPEG-b-PDMAPMA-b-PAH) with a disulfide linkage between mPEG and PDMAPMA blocks was developed for the intracellular targeted co-delivery of adriamycin and P-gp siRNA. The terpolymer was synthesized by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of N,N-dimethylaminopropyl methacrylamide and N-tert-butoxycarbonyl-N′-acryl hydrazine (Boc-acrylhydrazine) in the presence of a PEGylated macro-RAFT agent, followed by Boc-deprotection. The terpolymer could chemically conjugate adriamycin via an acid-cleavable hydrazone bond and simultaneously condense the negatively charged siRNA through electrostatic interactions at an N/P ratio of 2. The resultant adriamycin-conjugated nanoparticles/siRNA complexes (ADR-NPs/siRNA complexes) showed a spherical morphology and had an average diameter of 186 nm. The release profiles of the two payloads from the ADR-NPs/siRNA complexes exhibited a pH/reduction dual-dependent sustained release behavior. The ADR-NPs/siRNA complexes could simultaneously deliver adriamycin and siRNA efficiently into MCF-7/ADR cells and significantly inhibit their growth in a synergistic fashion. All the results indicated that the terpolymer mPEG-b-PDMAPMA-b-PAH could serve as a potential vehicle for the combination of chemotherapy and gene therapy.

Folate-decorated PEGylated triblock copolymer as a pH/reduction dual-responsive nanovehicle for targeted intracellular co-delivery of doxorubicin and Bcl-2 siRNA

Co-delivery of chemotherapeutic drug and small interfering RNA (siRNA) within a single nanovehicle has emerged as a promising combination therapy approach to treating cancers because of their synergistic effect. Nanocarrier delivery systems with low cytotoxicity and high efficiency are needed for such a purpose. In this study, a novel folate-conjugated PEGylated cationic triblock copolymer, poly(acrylhydrazine)-block-poly(3-dimethylaminopropyl methacrylamide)-block-poly(acrylhydrazine) (PAH-b-PDMAPMA-b-PAH), was synthesized and evaluated as a stimuli-sensitive vehicle for the targeted co-delivery of doxorubicin (DOX) and Bcl-2 siRNA into breast cancer MCF-7 cells. The synthetic process of the PEGylated triblock copolymer involved sequential reversible addition-fragmentation chain transfer polymerization, PEGylation and removal of tert-butoxy carbamate protecting groups. Folate-conjugated and/or -unconjugated poly(ethylene glycol) segments were grafted onto PAH-b-PDMAPMA-b-PAH via a reduction-sensitive disulfide linkage. The synthetic polymers were characterized by 1H NMR and gel permeation chromatography. The PEGylated triblock copolymer could chemically conjugate DOX onto PAH blocks via pH-responsive hydrazone bonds and simultaneously complex negatively charged Bcl-2 siRNA with cationic PDMAPMA blocks through electrostatic interactions at N/P ratios≥32:1 to form multifunctional nanomicelleplexes. The nanomicelleplexes exhibited spherical shape, possessed a positively charged surface with a zeta potential of +22.5mV and had a desirable and uniform particle size of 187nm. In vitro release studies revealed that the nanomicelleplexes could release DOX and Bcl-2 siRNA in a reduction and pH dual-sensitive manner and the payload release was significantly enhanced in a reductive acidic environment mimicking the endosomes/lysosomes of cancer cells compared to under physiology conditions. Furthermore, the release of both DOX and siRNA was found to follow Higuchi kinetic model. Confocal laser scanning microscopy, flow cytometry and MTT analyses confirmed that, compared with folate-undecorated nanomicelleplexes, folate-decorated nanomicelleplexes could more effectively co-deliver DOX and Bcl-2 siRNA into MCF-7 cells and showed a stronger cell-killing effect. The pristine PEGylated triblock copolymer exhibited good cytocompatibility. Moreover, co-delivery of DOX and Bcl-2 siRNA achieved a significant synergistic antitumor efficacy. These findings suggested that the folate-decorated PEGylated cationic triblock copolymer might be a promising vehicle for targeted intracellular co-delivery of DOX and siRNA in MCF-7 cells, representing a potential clinical combination therapy for breast cancer treatment.