Exploration of Zinc Oxide Nanoparticles as a Multitarget and Multifunctional Anticancer Nanomedicine

Because of the complexity of cancer, an ideal anticancer strategy is better to target both cancer cells and the tumor microenvironment. In this study, for the first time, we demonstrated that zinc oxide nanoparticles (ZnO NPs) were able to target multiple cell types of cancer, including cancer cells, cancer stem cells (CSCs), and macrophages, and simultaneously perform several key functions, including inhibition of cancer proliferation, sensitization of drug-resistant cancer, prevention of cancer recurrence and metastasis, and resuscitation of cancer immunosurveillance. As a nanocarrier, the chemotherapy drug, doxorubicin (Dox), could be loaded to ZnO NPs and the Dox-loaded ZnO NPs (ZnO/Dox) possessed excellent physicochemical and pH-responsive drug release properties. ZnO/Dox could be effectively internalized by both drug-sensitive and multidrug resistant (MDR) cancer cells and penetrate more efficiently through three-dimensional (3D) cancer cell spheroids compared with free Dox. As a cytotoxic agent, ZnO NPs were more efficient to kill MDR cancer cells. Interestingly, neither ZnO nor Dox showed high cytotoxicity in the 3D cancer cell spheroids, whereas ZnO/Dox showed remarkable synergistic anticancer effects. More importantly, we demonstrated that ZnO NPs could effectively downregulate CD44, a key CSC surface marker, and decrease the stemness of CSCs, leading to the sensitization of the Dox treatment, inhibition of the cancer cell adhesion and migration, and prevention of the tumor (3D cancer cell spheroid) formation. As an immunomodulator, ZnO NPs could protect macrophages from the Dox-induced toxicity and boost the Dox-induced macrophage polarization toward an M1-like phenotype. The macrophage-conditioned medium could promote the cancer cell apoptosis in both cancer cell monolayers and 3D spheroids. The findings in this study indicated that ZnO NPs were a multifunctional and multitarget nanocarrier and nanomedicine that would have more profound effects on cancer treatment

Building Stable MMP2-Responsive Multifunctional Polymeric Micelles by an All-in-One Polymer–Lipid Conjugate for Tumor-Targeted Intracellular Drug Delivery

In this study, we described an “all-in-one” polymer–lipid conjugate (PEG2k-ppTAT-PEG1k-PE) that could self-assemble to matrix metalloproteinase 2 (MMP2)-sensitive multifunctional micelles. The assembled micelles had several key features, including a protective long chain poly­(ethylene glycol) (PEG2k) (the outer shell), an MMP2-sensitive peptide linker (pp) (the tumor-targeting middle layer), a trans-activating transcriptional activator (TAT) peptide (the cell-penetrating middle layer), and a stable PEG1k-PE micelle for drug loading (the inner core). In the absence of MMP2, the PEG2k-ppTAT-PEG1k-PE micelles were intact and showed low bioactivity due to the surface-anchored PEG2k, whereas in the presence of MMP2, the pp was cleaved, resulting in the PEG2k deshielding and exposure of the previously hidden TAT for enhanced intracellular drug delivery. Even if completely cleaved by MMP2, the remaining PEG1k-PE micelles were stable and the micelles’ particle size and drug release were not significantly influenced. The paclitaxel (PTX)-loaded PEG2k-ppTAT-PEG1k-PE micelles showed significant MMP2-dependent cellular uptake, tumor penetration, and anticancer activity in various cancer cells and three-dimensional multicellular spheroids. Because of the enhanced intracellular drug accumulation, these multifunctional micelles were able to sensitize the drug-resistant cancer cells and their spheroids to PTX treatments. Furthermore, in vivo tumor uptake and retention data indicated that the PEG2k-ppTAT-PEG1k-PE micelles could dramatically increase the residence time of their payloads in the tumor

Improving Tumor Specificity and Anticancer Activity of Dasatinib by Dual-Targeted Polymeric Micelles

To improve tumor targetability and drug efficacy and decrease drug resistance of dasatinib (DSB), the multifunctional micellar nanoparticles that combined the matrix metalloproteinase 2 (MMP2)-sensitive tumor (site) targeting with folate receptor-mediated tumor (cell) targeting were developed. Two major functional polymers, polyethylene glycol (5000 Da)–MMP2-sensitive peptide–phosphoethanolamine (PEG5k-pp-PE) and folic acid–polyethylene glycol (2000 Da)–phosphoethanolamine (FA-PEG2k-PE), were synthesized to construct the dual-targeted micellar nanoparticles (MMP/FR micelles). In the absence of MMP2, the FA was shielded by PEG5k and the MMP/FR micelles showed low bioactivity. In the presence of MMP2, the nanoparticulate structure, stability, and cargo release profile of the MMP/FR micelles were not significantly affected, however, the MMP2-mediated PEG5k deshielding and FA exposure remarkably increased the cellular uptake and anticancer activity of the micelles in the MMP2 and FR expressing (MMP2+/FR+) cells, including multidrug resistant (MDR) cancer cells, rather than the MMP2– and FR– cells. In the 3D MDR tumor spheroids, the significant MMP2-dependent tissue penetration, uptake and cytotoxicity of the MMP/FR micelles were also observed. Furthermore, in the in vivo biodistribution study, the MMP2 and FR dual targeting strategy could significantly prolong the systemic circulation, decrease the nonspecific distribution in nontumor tissues, and increase the tumor accumulation of the polymeric micelles in a melanoma xenograft mouse model. The MMP2-sensitive FR-targeted micelles might have great potential as a tumor-targeted platform for delivery of molecular targeted therapeutics

Efficient Codelivery of Paclitaxel and Curcumin by Novel Bottlebrush Copolymer-based Micelles

The novel self-assembling bottlebrush polyethylene glycol-polynorbornene-thiocresol block copolymers (PEG-PNB-TC) were synthesized by the ring opening metathesis polymerization (ROMP), followed by functionalization of the polymer backbone via the thio-bromo “click” postpolymerization strategy. The PEG-PNB-TC copolymers could easily self-assemble into the nanoscale core–shell polymeric micelles. The hydrophobic anticancer drugs, such as paclitaxel (PTX), could be loaded into their hydrophobic core to form a stable drug-loaded micelle with a superior drug loading capacity of up to ∼35% (w/w). The sustained drug release behavior of the PEG-PNB-TC micelles was observed under a simulated “sink condition”. Compared with commercial PTX formulation (Taxol), the PTX-loaded PEG-PNB-TC micelles showed the enhanced in vitro cellular uptake and comparable cytotoxicity in the drug-sensitive cancer cells, while the copolymers were much safer than Cremophor EL, the surfactant used in Taxol. Furthermore, curcumin (CUR), a natural chemotherapy drug sensitizer, was successfully coloaded with PTX into the PEG-PNB-TC micelles. High drug loading capacity of the PEG-PNB-TC micelles allowed for easy adjustment of drug doses and the ratio of the coloaded drugs. The combination of PTX and CUR showed synergistic anticancer effect in both the drug mixture and drug coloaded micelles at high CUR/PTX ratio, while low CRU/PTX ratio only exhibited additive effects. The combinatorial effects remarkably circumvented the PTX resistance in the multidrug resistant (MDR) cancer cells. Due to the easy polymerization and functionalization, excellent self-assembly capability, high drug loading capability, and great stability, the PEG-PNB-TC copolymers might be a promising nanomaterial for delivery of the hydrophobic anticancer drugs, especially for combination drug therapy

H‑Gemcitabine: A New Gemcitabine Prodrug for Treating Cancer

In this report, we present a new strategy for targeting chemotherapeutics to tumors, based on targeting extracellular DNA. A gemcitabine prodrug was synthesized, termed H-gemcitabine, which is composed of Hoechst conjugated to gemcitabine. H-gemcitabine has low toxicity because it is membrane-impermeable; however, it still has high tumor efficacy because of its ability to target gemcitabine to E-DNA in tumors. We demonstrate here that H-gemcitabine has a wider therapeutic window than free gemcitabine