Metallic Oxide-Induced Self-Assembly of Block Copolymers to Form Polymeric Hybrid Micelles with Tunable Stability for Tumor Microenvironment-Responsive Drug Delivery.

Since block copolymers are able to self-assemble into various polymeric architectures, it is intriguing to explore a unique self-assembly strategy for polymers. Two different metallic oxides [manganese dioxide (MnO2) and zinc oxide (ZnO)] are displayed herein to demonstrate this self-assembly mechanism of polymers. In situ generation of metallic oxides induces self-assembly of block copolymers to form polymeric hybrid micelles with tunable stability in aqueous solutions. These final ZnO-cross-linked polymeric micelles exhibited a high drug loading capacity of 0.41 mg mg-1 toward doxorubicin (DOX), whereas DOX-loaded ZnO-cross-linked polymeric micelles could be broken down into Zn2+ and polymer scraps, which facilitated drug release in tumor microenvironments. Both in vitro and in vivo investigations showed that the drug-loaded ZnO-cross-linked polymeric micelles effectively suppressed tumor growth. Accordingly, the present study demonstrates a novel strategy of polymer self-assembly for fabricating polymeric architectures that can potentially provide insight for developing other polymeric architectures.

Optimized mesoporous silica nanoparticle-based drug delivery system with removable manganese oxide gatekeeper for controlled delivery of doxorubicin.

Rapid progress has been made for mesoporous silica nanoparticle (MSN) in recent years; however, efforts to fabricate MSN with adjustable size have been met with limited advancement in drug delivery, especially for the synthesis of MSN with adjustable size in the range of 150-300 nm. Herein we report the construction of a series of MSNs with adjustable specific surface area, size, and pore structure, depending on the different silicon monomers selected. The optimized MSN showed large specific surface area and appropriate size distribution for efficiently anchoring doxorubicin (DOX) through the imine linkage formed. Based on the remarkable features of the unique MSN, a novel MSN-based drug delivery system was prepared through the introduction of polydopamine/manganese oxide (PDA/MnO2) coating, which reduced the premature leakage of drugs in physiological environments, and yet facilitated drug release when destroyed by responding to endogenous glutathione (GSH) at the tumor sites. Notably, the transformation of MnO2 to Mn2+ resulted in the collapse of the PDA/MnO2 coating, which facilitated drug release and therefore indicated the controlled release feature. It was demonstrated that the drug-loaded MSN-based drug delivery system delivered drugs into cancer cells and showed effective inhibition against cancer cell growth. These results suggested that the emergence of MSN with adjustable size can expand the application of MSN in drug delivery.

Metal-Organic Framework-Assisted Nanoplatform with Hydrogen Peroxide/Glutathione Dual-Sensitive On-Demand Drug Release for Targeting Tumors and Their Microenvironment.

A hydrogen peroxide (H2O2)/glutathione (GSH) dual-sensitive nanoplatform holds great promise to alleviate the side effects of chemo drugs and improve their therapeutic efficacy against cancer. The site-specific release of chemo drugs with a low premature release still remains a challenge in the field of chemotherapy. In the present work, a novel and multifunctional drug delivery system (DDS) based on a polymethylacrylic acid core with a cross-linked structure of disulfide bond (PMAABACy), metal-organic framework (MOF) interlayer and biologically inspired polydopamine (PDA) coating was developed, serving as a vehicle for on-demand drug release. The dual-responsive nanoplatform not only prevents the premature leakage of a chemotherapeutic drug but also is sensitive to biologically relevant GSH and H2O2 for the precise delivery of chemotherapeutic drug. Considering the transmission route to DDS at the tumor site, the DDS might first respond to the extracellular H2O2 and then to the intracellular GSH, exhibiting a tunable release of chemotherapeutic drug. Through incubation using tumor cells, the growth of tumor cells could be significantly inhibited. Overall, by integrating these different building modules, this research demonstrates the advantages of the MOF-assisted regulate strategy to DDS for a precise site-specific release against tumor cells with a greatly reduced side effect on normal tissues.

Charge reversible and biodegradable nanocarriers showing dual pH-/reduction-sensitive disintegration for rapid site-specific drug delivery.

Dual pH-/reduction-sensitive biodegradable poly(methacrylic acid-co-N,N-bis(acryloyl)cystamine)/chitosan/dimethylmaleic anhydride-modified chitosan (PMAABACy/CS/CS-DMMA) nanoparticles with PMAABACy cores as carriers and dimethylmaleic anhydride-modified chitosan as charge reversible shells were rationally designed. PMAABACy cores using N,N-Bis(acryloyl)cystamine (BACy) as a crosslinker and methacrylic acid (MAA) as a monomer were fabricated via a mild and facile one-pot distillation-precipitation polymerization. After that, CS and CS-DMMA were alternately adsorbed on the surface of PMAABACy cores through a mild self-assembly. The results from TEM and DLS reveal that the PMAABACy/CS/CS-DMMA nanoparticles with desired size and hydrodynamic diameter. And then the nanoparticles exhibit the excellent drug-loading capacity and encapsulation efficiency toward anti-cancer agent doxorubicin (DOX), whereas be rapidly triggered to realize the GSH-sensitive site-specific release via the destruction of sulfide cross-linked structure in response to the intracellular environment of tumor cells. Furthermore, their surface charges could transfer from negative in neutral or basic medium to positive in acidic medium to enhance cellular uptake. Most importantly, the excellent anticancer activity has been also revealed using confocal laser scanning microscope (CLSM) analysis, namely successfully delivering DOX molecules to the cell nucleus. These experimental results indicate that such the novel dual pH-/reduction-sensitive biodegradable PMAABACy/CS/CS-DMMA with surface charge reversal have great potential as a desired anticancer drug carrier for cancer therapy.

Design and Development of Graphene Oxide Nanoparticle/Chitosan Hybrids Showing pH-Sensitive Surface Charge-Reversible Ability for Efficient Intracellular Doxorubicin Delivery.

A novel graphene oxide nanoparticle (GON)-based drug delivery system containing GONs as carriers of anticancer drugs and chitosan/dimethylmaleic anhydride-modified chitosan (CS/CS-DMMA) as surface charge-reversible shells is fabricated via the classic self-assembly of the deprotonated carboxyl of GONs and the protonated amine of the CS backbone by electrostatic interaction, and CS-DMMA serves as the outmost layer. In this GON-based drug delivery system, the GON cores as desired carriers might adsorb doxorubicin hydrochloride (DOX) via the π-π stacking interaction between the large π conjugated structures of GO and the aromatic structure of DOX. Meanwhile, the chitosan-based polyelectrolyte shells served as a smart protection screen to evade the premature release of the as-loaded DOX in normal extracellular condition, and then, the release of DOX was accelerated because of the detachment of chitosan coating at low pH. Furthermore, the re-exposure of amino groups after hydrolysis of CS-DMMA endowed the drug delivery system with positive surface charge by taking advantage of the pH difference between physiological conditions and the tumor microenvironment to enhance the cellular uptake. Then, the pH-dependent site-specific drug release was realized. The in vitro investigations confirmed that these promising GON/CS/CS-DMMA hybrids with the charge-reversible character possessed various merits including excellent encapsulation efficiency, high stability under physiological conditions, enhanced cellular uptake by HepG2 cells, and tunable intracellular chemotherapeutic agent release profiles, proving its capability as an intelligent anticancer agent nanocarrier with enhanced therapeutic effects. This smart GON/CS/CS-DMMA vehicle with the surface charge-reversible character may be used as a significant drug delivery system for cancer treatment.