Reduction-Responsive Anticancer Nanodrug Using a Full Poly(ethylene glycol) Carrier

Poly(ethylene glycol) (PEG) is applied extensively in biomedical fields because of its nontoxic, nonimmunogenic, and protein resistance properties. However, the strong hydrophilicity of PEG prevents it from self-assembling into an amphiphilic micelle in water, making it a challenge to fabricate a full-PEG carrier to deliver hydrophobic anticancer drugs. Herein, a paclitaxel (PTX)-loaded nanodrug was readily prepared through self-assembly of PTX and an amphiphilic PEG derivative, which was synthesized via melt polycondensation of two PEG diols (i.e., PEG₂₀₀ and PEG_10k) and mercaptosuccinic acid. The full PEG component endows the nanocarrier with good biocompatibility. Furthermore, because of the core cross-linked structure via the oxidation of mercapto groups, the nanodrug can be selectively disassociated under an intratumor reductive microenvironment through the reduction of disulfide bonds to release the loaded PTX and kill the cancer cells while maintaining high stability under the extratumor physiological condition. Additionally, it was confirmed that the nanodrug not only prolongs the biocirculation time of PTX but also possesses excellent in vivo antitumor efficacy while avoiding side effects of free PTX, for example, liver damage, which is promising for delivering clinical hydrophobic drugs to treat a variety of malignant tumors.

Full Poly(ethylene glycol) Hydrogels with High Ductility and Self-Recoverability

Energy dissipation is a common mechanism to improve the ductility of polymeric hydrogels. However, for poly(ethylene glycol) (PEG) hydrogels, it is not easy to dissipate energy, as polymer chains are dispersed in water without strong interchain interactions or decent entanglement. The brittleness limits the real applications of PEG hydrogels, although they are promising candidates in biomedical fields, as PEG has been approved by the U.S. Food and Drug Administration. Herein, we chemically introduced a center for energy dissipation in the PEG hydrogel system. Amphiphilic segmented PEG derivatives were designed through the melt polycondensation of triethylene glycol (PEG₁₅₀) and high molecular weight PEG in the presence of succinic acid and mercaptosuccinic acid as dicarboxylic acids. Full PEG hydrogels with elastic nanospheres as giant cross-linkers were facilely prepared by the self-assembly of esterified PEG₁₅₀ segments and the oxidation of mercapto groups. The resultant full PEG hydrogels can dissipate energy by the deformation of elastic nanospheres with outstanding ductility and self-recoverability while maintaining the excellent biocompatibility owing to their full PEG components. This work provides an original strategy to fabricate full PEG hydrogels with high ductility and self-recoverability, potentially applicable in biomedical fields.

Small-sized copolymeric nanoparticles for tumor penetration and intracellular drug release

Small-sized copolymeric nanoparticles have been developed for deep tumor penetration and nuclear drug delivery, which exhibit excellent solid tumor growth suppression.

Enzymatic synthesis of selenium-containing amphiphilic aliphatic polycarbonate as an oxidation-responsive drug delivery vehicle

Although functional aliphatic polycarbonates (APCs) have attracted prominent research interest as stimuli-responsive biomaterials, the majority of functional APCs are fabricated by detrimental organometallic catalysts or organo-catalysts. Herein, a facile synthetic strategy based on enzymatic polymerization was developed to construct a selenium-containing amphiphilic aliphatic polycarbonate (mPEG-b-CMP₄₅). Specifically, the selenium in its backbone framework underwent a hydrophobic–hydrophilic transition upon exposure to the abnormal ROS level of the tumor, thus providing a promising platform for ROS-triggered drug release. This amphiphilic mPEG-b-CMP₄₅ efficiently encapsulated doxorubicin (DOX) via self-assembly in aqueous solution and showed an excellent ability to regulate the release of DOX in response to H₂O₂ at biologically relevant concentrations (100 μM). These DOX-loaded nanoparticles could easily be internalized into U87 cells and possess the inherent antitumor properties of DOX, while they exhibited much lower cytotoxicity in normal cells HL-7702. Moreover, in many cases, the introduction of selenium caused high cytotoxicity of the materials, but the cytotoxicity results in HL-7702 cells demonstrated the good biocompatibility of mPEG-b-CMP₄₅. These collective data suggested the potential use of mPEG-b-CMP₄₅ as a biocompatible and smart drug delivery vehicle.

A facile synthetic strategy based on enzymatic polymerization was developed to construct a ROS-responsive polycarbonate served as biocompatible drug vehicle.

Preparation of pH/redox dual responsive polymeric micelles with enhanced stability and drug controlled release

Stimuli-responsive polymeric micelles were prepared through self-assembly of amphiphilic copolymers poly(ethylene glycol)-poly(γ-benzyl l-glutamate), followed by a core-crosslinking reaction using cystamine as the crosslinking agent. The crosslinked micelles with spherical morphologies in nanometer size showed enhanced stability against dilution and concentrated salt solutions compared to the micelles before crosslinking. Doxorubicin (DOX) as a model drug was encapsulated into the core of micelles through electrostatic interactions between carboxylic acid and DOX. In vitro drug release under pH and redox conditions was investigated. Furthermore, the cytotoxicity of micelles was evaluated before and after drug loading. The endocytosis of DOX-loaded micelles and the intracellular drug release were studied. DOX-loaded micelles exhibited accelerated drug release behaviors in an acidic and reductive environment, and showed an inhibited premature release behavior as compared to the noncrosslinked micelles. Considering their enhanced stability, pH and redox dual triggered responsive characteristics, the polymeric micelles can serve as potential systems for controlled drug delivery.

Redox-Responsive Self-Assembly Micelles from Poly(N-acryloylmorpholine-block-2-acryloyloxyethyl ferrocenecarboxylate) Amphiphilic Block Copolymers as Drug Release Carriers

Novel well-defined redox-responsive ferrocene-containing amphiphilic block copolymers (PACMO-b-PAEFC) were synthesized by ATRP, with poly(N-acryloylmorpholine) (PACMO) as hydrophilic blocks and poly(2-acryloyloxyethyl ferrocenecarboxylate) (PAEFC) as hydrophobic blocks. The copolymers were characterized by FT-IR and ¹H NMR spectroscopies and gel permeation chromatography, and the crystalline behavior was determined by X-ray diffraction and small-angle X-ray scattering. The results showed that the size of the lamellar crystals and crystallinity vary with the systematic compositions while the periodic structure of the lamellar stacks has no obvious change. These block copolymers could self-assemble and form globular nanoscaled core-shell micellar aggregates in aqueous solution. The reductive ferrocene groups could be changed into hydrophilic ferrocenium via mild oxidation, whereas the polymer micelles at the oxidation state could reversibly recover from their original states upon reduction by vitamin C. The tunable redox response was investigated and verified by transmission electron microscopy, ultraviolet-visible spectroscopy, cyclic voltammetry, and dynamic light scattering measurements. The copolymer micelles were used to entrap anticancer drug paclitaxel (PTX), with high drug encapsulation efficiency of 61.4%, while the PTX-loaded drug formulation exhibited oxidation-controlled drug release, and the release rate could be mediated by the kinds and concentrations of oxidants. MTT assay was performed to disclose the biocompatibility and security of the copolymer micelles and to assess anticancer efficiency of the PTX-loaded nanomicelles. The developed copolymer nanomicelles with reversible redox response are anticipated to have potential in targeted drug delivery systems for cancer therapy.

Surface charge switchable and core cross-linked polyurethane micelles as a reduction-triggered drug delivery system for cancer therapy

The core cross-linked polyurethane micelles with redox sensitive and pH-responsive surface charge switchable properties were prepared by using diisocyanates as crosslinkers and studied as anticancer drug carriers.

Injectable doxorubicin-loaded hydrogels based on dendron-like β-cyclodextrin–poly(ethylene glycol) conjugates

Dendron-like CD–PEG conjugates with multiple acrylates were synthesized facilely, which can incorporate adamantane-modified doxorubicin and further be crosslinked by POEGMS, to give injectable doxorubicin-loaded hydrogels.

An injectable drug-loaded hydrogel based on a supramolecular polymeric prodrug

We reported a novel injectable doxorubicin-loaded hydrogel based on host-guest interaction and Schiff's base reaction. A supramolecular polymeric prodrug was prepared through the inclusion of adamantane-modified doxorubicin into the β-cyclodextrin cavity on the polyaldehyde dextran chain, which was in situ crosslinked by carboxymethyl chitosan.

Facile Synthesis of Reductively Degradable Biopolymers Using Cystamine Diisocyanate as a Coupling Agent

Reductively degradable biopolymers have emerged as a unique class of smart biomedical materials. Here, a functional coupling agent, cystamine diisocyanate (CDI), was designed to offer a facile access to reductively degradable biopolymers via polycondensation with various diols. CDI was readily obtained with a decent yield of 46% by reacting cystamine dihydrochloride with triphosgene. The polycondensation of oligo(ethylene glycol) diol (Mn = 0.4 or 1.5 kg/mol) or oligo(ε-caprolactone) diol (Mn = 0.53 kg/mol) with CDI in N,N-dimethylformamide at 60 °C using dibutyltin dilaurate as a catalyst afforded reductively degradable poly(ethylene glycol) (SSPEG, Mn = 6.2-76.8 kg/mol) or poly(ε-caprolactone) (SSPCL, Mn = 6.8-16.3 kg/mol), in which molecular weights were well controlled by diol/CDI molar ratios. Moreover, PEG-SSPCL-PEG triblock copolymers could be readily prepared by reacting dihydroxyl-terminated SSPCL with PEG-isocyanate derivative. PEG-SSPCL-PEG with an Mn of 5.0-16.3-5.0 kg/mol formed small-sized micelles with an average diameter of about 85 nm in PB buffer. The in vitro release studies using doxorubicin (DOX) as a model drug showed that, in sharp contrast to reduction-insensitive PEG-PCL(HDI)-PEG controls, drug release from PEG-SSPCL-PEG micelles was fast and nearly complete in 24 h under a reductive condition containing 10 mM glutathione. The confocal microscopy experiments in drug-resistant MCF-7 cells (MCF-7/ADR) displayed efficient cytoplasmic DOX release from PEG-SSPCL-PEG micelles. MTT assays revealed that DOX-loaded PEG-SSPCL-PEG micelles were much more potent against MCF-7/ADR cells than reduction-insensitive PEG-PCL(HDI)-PEG controls (IC50: 6.3 vs 55.4 μg/mL). It should further be noted that blank PEG-SSPCL-PEG micelles were noncytotoxic up to a tested concentration of 1 mg/mL. Hence, cystamine diisocyanate appears to be an innovative coupling agent that facilitates versatile synthesis of biocompatible and reductively degradable biopolymers.

Injectable camptothecin conjugated hydrogels with simultaneous drug release and degradation

Novel injectable camptothecin conjugated hydrogels with simultaneous drug release and degradation properties were prepared, which show significant cytotoxicity to HepG2 cells, and could be a potential candidate for intratumor drug delivery.

Redox-responsive, core-crosslinked degradable micelles for controlled drug release

We developed novel redox-responsive, core-crosslinked micelles (CCLMs) via a simple, one-step click chemistry reaction.

Injectable cationic hydrogels with high antibacterial activity and low toxicity

We prepared injectable cationic hydrogels with strong antibacterial activity and remarkably low toxicity by in situ thiol–ene “click” reaction between dimethacrylate terminated poly(hexamethylene guanidine) (PHMGDMA) and poly[oligo(ethylene) glycol mercaptosuccinate] (POEGMS) under physiological conditions.

One-pot synthesis of crosslinked amphiphilic polycarbonates as stable but reduction-sensitive carriers for doxorubicin delivery

In this paper, we first synthesized a novel disulfide-coupled bis-(cyclic carbonate) (TDCSS) monomer. After ring-opening co-polymerization (ROP) of TDCSS and trimethylene carbonate (TMC) initiated by mono-methoxyl poly(ethylene glycol), the crosslinked reduction-sensitive copolymer PEG-P(TMC-co-TDCSS) was obtained via a facile one-step procedure for efficient delivery of doxorubicin (DOX) into cancer cells. To serve as controls, PEG-P(TMC-co-TDCCC), which has an analogous structure without disulfide bond, and a linear polymer PEG-PTMC were also prepared. The copolymers could self-assemble to form nano-sized micelles in an aqueous solution. As compared to PEG-PTMC, crosslinked PEG-P(TMC-co-TDCSS) and PEG-P(TMC-co-TDCCC) showed lower CMC values and thus induced a much better micelle-forming ability. In vitro release studies revealed that the drug release behavior of DOX-loaded PEG-P(TMC-co-TDCSS) micelles, which could be accelerated in the presence of 10 mM dithiothreitol (DTT), showed a similar trend in the absence of DTT compared to DOX-loaded PEG-P(TMC-co-TDCCC) micelles. Furthermore, confocal laser scanning microscopy (CLSM) indicated that DOX-loaded PEG-P(TMC-co-TDCSS) micelles were efficiently internalized into HeLa cells, releasing DOX into the cytoplasm after which the drug finally entered the nuclei, while MTT assays also demonstrated potent cytotoxic activity against HeLa cells. DOX was mainly located in the cytoplasm for reduction-insensitive PEG-P(TMC-co-TDCCC) and PEG-PTMC controls.

An injectable drug-loaded hydrogel using a “clickable” amphiphilic triblock copolymer as a precursor

A PCL-POEGM-PCL amphiphilic triblock copolymer was facilely synthesized in “one pot”, which can disperse hydrophobic drugs in aqueous solution and be crosslinked by poly[oligo(ethylene glycol)mercaptosuccinate] (POEGMS) under physiological conditions.

Reduction-triggered release of paclitaxel from in situ formed biodegradable core-cross-linked micelles

We provide a facile strategy to prepare redox-responsive core-crosslinked micelles for the controlled release of paclitaxel.

Acid-triggered drug release from micelles based on amphiphilic oligo(ethylene glycol)–doxorubicin alternative copolymers

We prepared pH-sensitive amphiphilic oligo(ethylene glycol)–doxorubicin alternative conjugates for the controlled release of doxorubicin.

Facile fabrication of ultrathin antibacterial hydrogel films via layer-by-layer “click” chemistry

Ultrathin antibacterial hydrogel films were prepared via layer-by-layer “click” chemistry.

Facile synthesis of a reduction-responsive amphiphilic triblock polymer via a selective thiol–disulfide exchange reaction

A reduction-responsive amphiphilic triblock polymer was prepared via polycondensation between a dithiol and dipyridyl disulfide, followed by a selective thiol–disulfide exchange reaction.