Liandong Deng

Balancing the stability and drug release of polymer micelles by the coordination of dual-sensitive cleavable bonds in cross-linked core

The optimal structure design of nanocarriers to inhibit premature release of anticancer drugs from nanocarriers during blood circulation and improve drug release inside tumor cells is still a significant issue for polymer micelles applied to antitumor drug delivery. Herein, in order to balance the contradiction between polymer micellar stability and drug release, dual-sensitive cleavable cross-linkages of benzoic imine conjugated disulfide bonds were introduced into the core of the amphiphilic copolymer micelles to form core-cross-linked micelles. First, biodegradable poly(ethylene glycol)-b-(polycaprolactone-g-poly(methacrylic acid-p-hydroxy benzaldehyde-cystamine)), i.e. mPEG-b-(PCL-g-P(MAA-Hy-Cys)) (PECMHC) copolymers were synthesized and assembled into PECMHC micelles (PECMHC Ms). Then, simply by introducing H2O2 to the PECMHC Ms dispersions to oxidate the thiol groups of cystamine moieties in the core, core-cross-linked PECMHC micelles (cc-PECMHC Ms) ∼100 nm in size were readily obtained in water. In vitro studies of doxorubicin (DOX)-loaded cc-PECMHC Ms show that the cross-linked core impeded the drug release in the physical conditions, owing to the high stability of the micelles against both extensive dilution and salt concentration, while it greatly accelerated DOX release in mildly acidic (pH ∼5.0-6.0) medium with glutathione, owing to the coordination of the pH-sensitive cleaving of benzoic imine bonds and the reduction-sensitive cleaving of disulfide bonds. The in vivo tissue distribution and tumor accumulation of the DOX-loaded cc-PECMHC Ms were monitored via fluorescence images of DOX. DOX-loaded cc-PECMHC Ms exhibited enhanced tumor accumulation because of their high stability in blood circulation and less DOX premature release. Therefore, the cc-PECMHC Ms with dual-sensitive cleavable bonds in the cross-linked core were of excellent biocompatibility, high extracellular stability and had intelligent intracellular drug release properties, indicating promise as candidates for anticancer drug delivery.

Improving the oral delivery efficiency of anticancer drugs by chitosan coated polycaprolactone-grafted hyaluronic acid nanoparticles

Sequentially overcoming the obstacles mainly from the low water solubility of lipophilic anticancer drugs, gastrointestinal microenvironment and systemic circulation is the major concern for designing oral anticancer drug carriers. Herein, we prepared the multifunctional polyelectrolyte complex nanoparticles (CNPs), engineered by hyaluronic acid (HA) grafted polycaprolactone (PCL) nanoparticles (HA-g-PCL NPs) coated with chitosan (CS) electrostatically, as a platform to improve the oral delivery efficiency of lipophilic anticancer drugs. Paclitaxel (PTX) and doxorubicin (DOX) were used as the model medicine and fluorescence probe, respectively. The size, zeta potential, morphology and pH-sensitivity of the NPs were studied systematically. The results indicated that the core-shell structure of CS/HA-g-PCL CNPs was formed at pH 5.0, which remained intact in the pH ranging from 3.0 to 6.8, while the CS layer detached gradually with the increase of pH to 7.4 and the HA-g-PCL NPs were released. In vitro drug release studies showed that accelerated drug release was triggered by hyaluronidase-1 (Hyal-1), which was a major HA degradation enzyme abundant within tumor cells. Cell uptake studies showed that HA-g-PCL NPs were internalized into cancer cells (EC109) via receptor-mediated endocytosis, but were rarely taken up by normal fibroblasts (NIH3T3). Furthermore, intracellular drug release indicated that HA-g-PCL NPs could provide an effective approach for transport of loaded cargoes into the cytoplasm. Therefore, higher cytotoxicity for PTX loaded HA-g-PCL NPs (HA-g-PCL/PTX NPs) against cancer cells EC109 but lower cytotoxicity against normal cells NIH3T3 was observed. In vivo studies showed that CS/HA-g-PCL CNPs via oral administration were able to preferentially deliver drugs into tumor tissue with commendable antitumor efficiency and few side effects. Overall, CS/HA-g-PCL CNPs showed great potential for improving oral delivery efficiency of lipophilic anticancer drugs.

Effects of hydrophobic core components in amphiphilic PDMAEMA nanoparticles on siRNA delivery.

Due to their biodegradable character, polyesters such as polycaprolactone (PCL), poly(D,L-lactide) (PDLLA), and polylactic-co-glycolic acid (PLGA) were widely used as the hydrophobic cores of amphiphilic cationic nanoparticles (NPs) for siRNA delivery. However, fewer researches focused on facilitating siRNA delivery by adjusting the polyester composition of these nanoparticles. Herein, we investigated the contribution of polyester segments in siRNA delivery in vitro by introducing different ratio of DLLA moieties in PCL segments of mPEG-block-PCL-graft-poly(dimethylamino ethyl methacrylate)(PEG-b-PCL-g-PDMAEMA). It was noticed that compared with the other ratios of DLLA moieties, a certain molar ratio (about 70%) of the NPs, named mPEG45-P(CL21-co-DLLA48)-g-(PDMAEMA29)2 (PECLD-70), showed the highest gene knockdown efficiency but poorest cellular uptake ability in vitro. Further research revealed that NPs with various compositions of the polyester cores showed different physicochemical properties including particle size, zeta potential and stiffness, leading to different endocytosis mechanisms thus influencing the cellular uptake efficiency. Subsequently, we observed that the cells treated by PECLD-70 NPs/Cy5 siRNA complexes exhibited more diffuse Cy5 signal distribution than other NPs by confocal laser scanning microscope, which suggested that siRNA delivered by PECLD-70 NPs/Cy5 siRNA complexes possessed of stronger capabilities in escaping from endosome/lysosome, entering the RNA-induced silencing complex (RISC) and cutting the target mRNA efficiently. The different siRNA release profile was dominated by the degradation rate of polyester segments. Therefore, it could be concluded that the adjustment of hydrophobic core of cationic nanoparticles could significantly affect their transfection behavior and appropriate polyester composition should be concerned in designing of analogous siRNA vectors.

Composites of electrospun‐fibers and hydrogels: A potential solution to current challenges in biological and biomedical field

With increasingly rigorous requirements for biomaterials, the design and fabrication of novel materials with smart functions are urgently needed. The fabrication of composite materials that can surmount individual shortcomings as well as bring synergistic benefits represents an efficient route to improve the performances and expand application scopes of biomaterials. Due to their unique structures and properties, electrospun-fibers and hydrogels have been widely applied in many biological and biomedical fields. Based on this, more and more attentions have been paid on the composites of electrospun-fibers and hydrogels as biomaterials, aiming to bring their individual superiority into full play as well as remedy their intrinsic defects. This review summarizes approaches used to integrate electrospun-fibers and hydrogels into various structures and the development of their composites as a potential solution to some current challenges in drug delivery, tissue engineering and some other bio-related aspects. The individual roles and mutual synergy of electrospun-fibers and hydrogels in the composites will be emphasized.

A strategy for oral chemotherapy via dual pH-sensitive polyelectrolyte complex nanoparticles to achieve gastric survivability, intestinal permeability, hemodynamic stability and intracellular activity

Efficient oral administration of anticancer agents requires a nanocarrier to long survive in the stomach, effectively penetrate across the small intestine, tightly retain the drug during bloodstream and quickly release drug in tumor cells. Herein a kind of dual pH-sensitive polyelectrolyte complex nanoparticles (CNPs) was developed by employing electrostatic interaction between positively charged chitosan (CS) and negative poly (L-glutamic acid) grafted polyethylene glycol-doxorubicin conjugate nanoparticles (PG-g-PEG-hyd-DOX NPs) with acid-labile hydrazone linkages. The obtained NPs and CNPs were characterized for their morphology, particle size, ζ-potential, pH-sensitivity under the simulated physiological conditions, drug release, as well as in vivo antitumor activity and biodistribution. The results indicated that CNPs can remain intact structure in pH range from 3.0 to 6.5. After detaching CS layer due to the pH-induced deprotonation with increasing pH to 7.4 in the mucus layer of the small intestine, the inner NPs would be released and effectively absorbed into blood circulation via opening the tight junctions by CS. PG-g-PEG-hyd-DOX NPs with demonstrated long-circulating properties can be accumulated in the tumor via EPR effect and dump the drug within tumor cells by acid-cleavage of hydrazone bonds between PG-g-PEG and DOX, achieving high therapeutic efficacy and low systemic toxicity. These results suggest that the design presented here, combining the functions of the gastrointestinal pH-sensitive electrostatic complex and intracellular acid-sensitive macromolecular prodrugs NPs, can sequentially overcome the biological barriers of oral anticancer drug delivery, which thus provides a promising nanomedicine platform for oral chemotherapy.

Thermosensitive hydrogel system assembled by PTX-loaded copolymer nanoparticles for sustained intraperitoneal chemotherapy of peritoneal carcinomatosis

Intraperitoneal (IP) chemotherapy is a preferable treatment option for peritoneal carcinomatosis of malignancies by delivering chemotherapeutic drugs into the abdominal cavity. A persistent major challenge in IP chemotherapy is the need to provide effective drug concentration in the peritoneal cavity for an extended period of time. In the present work, the thermosensitive hydrogel system (PTX/PECT(gel)) assembled by PTX (paclitaxel)-loaded amphiphilic copolymer (PECT, poly (ε-caprolactone-co-1,4,8-trioxa [4.6]spiro-9-undecanone)-poly(ethylene glycol)-poly (ε-caprolactone-co-1,4,8-trioxa [4.6]spiro-9-undecanone)) nanoparticles was developed for sustained IP chemotherapy of peritoneal carcinomatosis model. Cytotoxicity assay indicated that PECT hydrogel was biocompatible with very low cytotoxicity and PTX/PECT(gel) had enhanced cytotoxicity than free PTX. In vivo toxicity study demonstrated the biocompatibility and biosafety of PECT hydrogel as an IP chemotherapy carrier. The fluorescence imaging method was employed to monitor the intraperitoneal degradation of PECT hydrogel by labeling PECT with rhodamine B. PECT hydrogel with the dose of 200μL showed about 8days retention time and most of the injected hydrogel was located in the intestine. The anti-tumor efficacy study was carried out in mice bearing CT26 intraperitoneal ascites fluid as colorectal peritoneal carcinomatosis model. The result showed that intraperitoneal administration of PTX/PECT(gel) could effectively suppress growth and metastasis of CT26 peritoneal carcinomatosis in vivo, compared with Taxol® group. The pharmacokinetic studies demonstrated that PTX/PECT(gel) could improve the bioavailability of PTX by being formulated in PECT hydrogel. Overall, sustained drug concentration at peritoneal levels in combination with drug in the form of nanoparticle contributes to the enhanced anti-tumor efficacy. Thus, our results suggested that PTX/PECT(gel) may have great potential applications in IP chemotherapy.

Acid-induced disassemblable nanoparticles based on cyclic benzylidene acetal-functionalized graft copolymer via sequential RAFT and ATRP polymerization

Polymeric nanoparticles assembled from the amphiphilic graft copolymer with cyclic benzylidene acetal-functionalized backbone and short poly(2-hydroxyethyl methacrylate) side chains can remain structurally stable at pH 7.4, but undergo stepwise disassembly in mildly acidic conditions due to the acid-triggered cleavage of the acetals, providing a promising nanocarrier for cancer therapy.

pH/redox dual-sensitive nanoparticles based on the PCL/PEG triblock copolymer for enhanced intracellular doxorubicin release

pH/redox dual-sensitive nanoparticles (NPs) based on a poly(e-caprolactone) (PCL) and polyethylene glycol (PEG) triblock copolymer were developed and investigated aiming at improving the drug release property of PCL in cancer chemotherapy. A redox-sensitive disulfide bond and pH-sensitive benzoic-imine linkers were introduced to the backbone of the amphiphilic block copolymer termed SCHE, which could self-assemble into stable spherical NPs in aqueous solutions with an average size of about 100 nm. Doxorubicin (DOX) as a hydrophobic anticancer drug was loaded into the NPs by a dialysis method. The in vitro drug release results showed that the accumulative release amount of DOX at pH 5.0 with 10 mM glutathione (GSH) was accelerated apparently by more than twice compared to that at pH 7.4 without GSH. After a pre-treatment with GSH, the intracellular fluorescence intensity of Hela cells was enhanced compared to those without the pretreatment, which indicated faster DOX release in cells with higher GSH concentration. In an MTT assay, no obvious toxicity of blank NPs was found. In conclusion, SCHE NPs could serve as a novel colloidal drug delivery system in cancer chemotherapy and the introduced unstable linkers could enhance the drug release rate at tumor sites.

Influence of 2-(diisopropylamino)ethyl methacrylate on acid-triggered hydrolysis of cyclic benzylidene acetals and their importance in efficient drug delivery

The ability to tune the degradation rate of a biodegradable polymer, which can achieve precise spatiotemporal control of drug delivery, is of considerable interest for biomedical applications. In this study, a series of amphiphilic copolymers, methoxy poly(ethyleneglycol)-b-poly((2,4,6-trimethoxybenzylidene-1,1,1-tris(hydroxymethyl) ethane methacrylate)-co-2-(diisopropylamino)ethyl methacrylate) (mPEG-b-P(TTMA-co-DPA), PETD) with different numbers of DPA units, were synthesized by Reversible Addition Fragmentation Chain Transfer (RAFT) copolymerization, in which DPA containing tertiary amines were introduced to adjust the hydrolysis behavior of cyclic benzylidene acetals (CBAs). The molecular structure and the chemical composition of PETD were characterized by 1H NMR and gel permeation chromatography (GPC). PETD could self-assemble into stable nanoparticles with well-defined spherical morphology and displayed high drug loading capacity with doxorubicin (DOX) as the drug model. The hydrolysis behavior of CBAs in the PETD NPs was investigated by UV/vis spectroscopy under different pH values. Compared with PETD-0 bearing no DPA unit, the hydrolysis rate of PETD-3 with more DPA was faster, while PETD-1 with less DPA hydrolyzed much slower, which indicated that the introduction of DPA had an amphoteric effect on the hydrolysis behavior of CBAs under acidic conditions. In addition, the in vitro release of DOX was also investigated under different pH conditions and the result was in accordance with the hydrolysis result. Furthermore, the results of fluorescence microscopy demonstrated improved internalization of DOX-loaded PETD-3 NPs in HepG-2 cells with rapid DOX release intracellularly, which showed considerable cytotoxicity against HepG-2 cells.

Supramolecular Hydrogel from Nanoparticles and Cyclodextrins for Local and Sustained Nanoparticle Delivery.

Injectable and biodegradable supramolecular hydrogel mPECT NP/α-CD(gel) composed of high-concentration nanoparticle dispersion (≤20% W/V) and α-cyclodextrins (α-CD) are prepared by a two-level physical cross-linking using amphiphilic block polymer methoxy poly(ethylene glycol)-b-poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (mPECT) and α-CD. The gelation behavior depends on the concentration of nanoparticles and α-CD. The viscoelasticity and shear thinning of mPECT NP/α-CD(gel) are confirmed. In vitro hydrogel erosion is demonstrated to be mainly a concentration-dependent dissociation process with general release of discrete mPECT nanoparticles about 50 nm that can be easily taken up by cells. The in vitro release behavior can be modulated by changing the concentration of nanoparticles or α-CD. In vitro and in vivo cytotoxicity study demonstrates its biocompatibility and biosafety. Gel formation after subcutaneous injection is also confirmed and mPECT NP/α-CD(gel) shows about 2 weeks retention time. This work validates the potential application for this supramolecular hydrogel in local and sustained delivery of nanoparticles.