Meng-Hua Xiong

Doxorubicin-Tethered Responsive Gold Nanoparticles Facilitate Intracellular Drug Delivery for Overcoming Multidrug Resistance in Cancer Cells

Multidrug resistance (MDR) is a major impediment to the success of cancer chemotherapy. Through the development of a drug delivery system that tethers doxorubicin onto the surface of gold nanoparticles with a poly(ethylene glycol) spacer via an acid-labile linkage (DOX-Hyd@AuNPs), we have demonstrated that multidrug resistance in cancer cells can be significantly overcome by a combination of highly efficient cellular entry and a responsive intracellular release of doxorubicin from the gold nanoparticles in acidic organelles. DOX-Hyd@AuNPs achieved enhanced drug accumulation and retention in multidrug resistant MCF-7/ADR cancer cells when it was compared with free doxorubicin. It released doxorubicin in response to the pH of acidic organelles following endocytosis, opposite to the noneffective drug release from doxorubicin-tethered gold nanoparticles via the carbamate linkage (DOX-Cbm@AuNPs), which was shown by the recovered fluorescence of doxorubicin from quenching due to the nanosurface energy transfer between the doxorubicinyl groups and the gold nanoparticles. DOX-Hyd@AuNPs therefore significantly enhanced the cytotoxicity of doxorubicin and induced elevated apoptosis of MCF-7/ADR cancer cells. With a combined therapeutic potential and ability to probe drug release, DOX-Hyd@AuNPs represent a model with dual roles in overcoming MDR in cancer cells and probing the intracellular release of drug from its delivery system.

Lipase-Sensitive Polymeric Triple-Layered Nanogel for “On-Demand” Drug Delivery

We report a new strategy for differential delivery of antimicrobials to bacterial infection sites with a lipase-sensitive polymeric triple-layered nanogel (TLN) as the drug carrier. The TLN was synthesized by a convenient arm-first procedure using an amphiphilic diblock copolymer, namely, monomethoxy poly(ethylene glycol)-b-poly(ε-caprolactone), to initiate the ring-opening polymerization of the difunctional monomer 3-oxapentane-1,5-diyl bis(ethylene phosphate). The hydrophobic poly(ε-caprolactone) (PCL) segments collapsed and surrounded the polyphosphoester core, forming a hydrophobic and compact molecular fence in aqueous solution which prevented antibiotic release from the polyphosphoester core prior to reaching bacterial infection sites. However, once the TLN sensed the lipase-secreting bacteria, the PCL fence of the TLN degraded to release the antibiotic. Using Staphylococcus aureus (S. aureus) as the model bacterium and vancomycin as the model antimicrobial, we demonstrated that the TLN released almost all the encapsulated vancomycin within 24 h only in the presence of S. aureus, significantly inhibiting S. aureus growth. The TLN further delivered the drug into bacteria-infected cells and efficiently released the drug to kill intracellular bacteria. This technique can be generalized to selectively deliver a variety of antibiotics for the treatment of various infections caused by lipase-secreting bacteria and thus provides a new, safe, effective, and universal approach for the treatment of extracellular and intracellular bacterial infections.

Functionalized micelles from block copolymer of polyphosphoester and poly(ɛ-caprolactone) for receptor-mediated drug delivery

Cellular specific micellar systems from functional amphiphilic block copolymers are attractive for targeted intracellular drug delivery. In this study, we developed reactive micelles based on diblock copolymer of poly(ethyl ethylene phosphate) and poly(epsilon-caprolactone). The micelles were further surface conjugated with galactosamine to target asialoglycoprotein receptor (ASGP-R) of HepG2 cells. The size of micellar nanoparticles was about 70nm in diameter, and nanoparticles were negatively charged in aqueous solution. Through recognition between galactose ligands with ASGP-R of HepG2 cells, cell surface binding and internalization of galactosamine-conjugated micelles were significantly promoted, which were demonstrated by flow cytometric analyses using rhodamine 123 fluorescent dye. Paclitaxel-loaded micelles with galactose ligands exhibited comparable activity to free paclitaxel in inhibiting HepG2 cell proliferation, in contrast to the poor inhibition activity of micelles without galactose ligands particularly at lower paclitaxel doses. In addition, population of HepG2 cells arrested in G2/M phase was in positive response to paclitaxel dose when cells were incubated with paclitaxel-loaded micelles with galactosamine conjugation, which was against the performance of micelles without galactose ligand, owing to the ligand-receptor interaction. The surface functionalized micellar system is promising for specific anticancer drug transportation and intracellular drug release.

Bacteria‐Responsive Multifunctional Nanogel for Targeted Antibiotic Delivery

Bacteria-Responsive Multifunctional Nanogel: We developed a bacteria-responsive multifunctional nanogel for targeted antibiotic delivery, in which bacterial enzymes are utilized to trigger antibiotic release by degrading the polyphosphoester core. The mannosylated nanogel preferentially delivers drugs to macrophages and leads to drug accumulation at bacterial infection sites through macrophage transport. This nanogel provides macrophage targeting and lesion site-activatable drug release properties, which enhances bacterial growth inhibition.

Core-shell-corona micelle stabilized by reversible cross-linkage for intracellular drug delivery.

Reversibly cross-linked core-shell-corona micelles based on a triblock copolymer composed of poly(aliphatic ester), polyphosphoester, and poly(ethylene glycol) are reported. The triblock copolymer is synthesized through consecutive ring-opening polymerization of ε-caprolactone and 2,4-dinitrophenylthioethyl ethylene phosphate, followed by conjugation of poly(ethylene glycol). After deprotection under mild conditions, the amphiphilic polymer forms core-shell-corona micelles with free thiols in the shell. Cross-linking of the micelles within the shell reduces their critical micellization concentration and enhances their stability against severe conditions. The redox-sensitive cross-linkage allows the facilitated release of entrapped anticancer drugs in the cytoplasm in response to the intracellular reductive environment. With enhanced stability during circulation after administration, and accelerated intracellular drug release at the target site, the biocompatible and biodegradable shell-cross-linked polymeric micelle is promising as a drug vehicle for cancer chemotherapy.

Single-step assembly of cationic lipid-polymer hybrid nanoparticles for systemic delivery of siRNA.

The clinical success of therapeutics of small interfering RNA (siRNA) is still hindered by its delivery systems. Cationic polymer or lipid-based vehicles as the major delivery systems of siRNA cannot sufficiently satisfy siRNA therapeutic applications. It is hypothesized that cationic lipid-polymer hybrid nanoparticles may take advantage of both polymeric and lipid-based nanoparticles for siRNA delivery, while diminishing the shortcomings of both. In this study, cationic lipid-polymer hybrid nanoparticles were prepared by a single-step nanoprecipitation of a cationic lipid (N,N-bis(2-hydroxyethyl)-N-methyl-N-(2-cholesteryloxycarbonyl aminoethyl) ammonium bromide, BHEM-Chol) and amphiphilic polymers for systemic delivery of siRNA. The formed hybrid nanoparticles comprised a hydrophobic polylactide core, a hydrophilic poly(ethylene glycol) shell, and a cationic lipid monolayer at the interface of the core and the shell. Such hybrid nanoparticles exhibited excellent stability in serum and showed significantly improved biocompatibility compared to that of pure BHEM-Chol particles. The hybrid nanoparticles were capable of delivering siRNA into BT474 cells and facilitated the escape of loaded siRNA from the endosome into the cytoplasm. The hybrid nanoparticles carrying polo-like kinase 1 (Plk1)-specific siRNA (siPlk1) remarkably and specifically downregulated expression of the oncogene Plk1 and induced cancer cell apoptosis both in vitro and in vivo and significantly suppressed tumor growth following systemic administration. We demonstrate that this system is stable, nontoxic, highly efficient, and easy to scale up, bringing the clinical application of siRNA therapy one important step closer to reality.

N-acetylgalactosamine functionalized mixed micellar nanoparticles for targeted delivery of siRNA to liver.

Due to its efficient and specific gene silencing ability, RNA interference has shown great potential in the treatment of liver diseases. However, achieving in vivo delivery of siRNA to critical liver cells remains the biggest obstacle for this technique to be a real clinic therapeutic modality. Here, we describe a promising liver targeting siRNA delivery system based on N-acetylgalactosamine functionalized mixed micellar nanoparticles (Gal-MNP), which can efficiently deliver siRNA to hepatocytes and silence the target gene expression after systemic administration. The Gal-MNP were assembled in aqueous solution from mixed N-acetylgalactosamine functionalized poly(ethylene glycol)-b-poly(ε-caprolactone) and cationic poly(ε-caprolactone)-b-poly(2-aminoethyl ethylene phosphate) (PCL-b-PPEEA); the properties of nanoparticles, including particle size, zeta potential and the density of poly(ethylene glycol) could be easily regulated. The hepatocyte-targeting effect of Gal-MNP was demonstrated by significant enriching of fluorescent siRNA in primary hepatocytes in vitro and in vivo. Successful down-regulation of liver-specific apolipoprotein B (apoB) expression was achieved in mouse liver, at both the transcriptional and protein level, following intravenous injection of Gal-MNP/siapoB to BALB/c mice. Systemic delivery of Gal-MNP/siRNA did not induce the innate immune response or positive hepatotoxicity. The results of this study suggested therapeutic potential for the Gal-MNP/siRNA system in liver disease.

Synthetic Lethal Therapy for KRAS Mutant Non-small-cell Lung Carcinoma with Nanoparticle-mediated CDK4 siRNA Delivery

The KRAS mutation is present in ~20% of lung cancers and has not yet been effectively targeted for therapy. This mutation is associated with a poor prognosis in non-small-cell lung carcinomas (NSCLCs) and confers resistance to standard anticancer treatment drugs, including epidermal growth factor receptor tyrosine kinase inhibitors. In this study, we exploited a new therapeutic strategy based on the synthetic lethal interaction between cyclin-dependent kinase 4 (CDK4) downregulation and the KRAS mutation to deliver micellar nanoparticles (MNPs) containing small interfering RNA targeting CDK4 (MNPsiCDK4) for treatment in NSCLCs harboring the oncogenic KRAS mutation. Following MNPsiCDK4 administration, CDK4 expression was decreased, accompanied by inhibited cell proliferation, specifically in KRAS mutant NSCLCs. However, this intervention was harmless to normal KRAS wild-type cells, confirming the proposed mechanism of synthetic lethality. Moreover, systemic delivery of MNPsiCDK4 significantly inhibited tumor growth in an A549 NSCLC xenograft murine model, with depressed expression of CDK4 and mutational KRAS status, suggesting the therapeutic promise of MNPsiCDK4 delivery in KRAS mutant NSCLCs via a synthetic lethal interaction between KRAS and CDK4.

Differential anticancer drug delivery with a nanogel sensitive to bacteria-accumulated tumor artificial environment.

Differential anticancer drug delivery that selectively releases a drug within a tumor represents an ideal cancer therapy strategy. Herein, we report differential drug delivery to the tumor through the fabrication of a special bacteria-accumulated tumor environment that responds to bacteria-sensitive triple-layered nanogel (TLN). We demonstrate that the attenuated bacteria SBY1 selectively accumulated in tumors and were rapidly cleared from normal tissues after intravenous administration, leading to a unique bacteria-accumulated tumor environment. Subsequent administrated doxorubicin-loaded TLN (TLND) was thus selectively degraded in the bacteria-accumulated tumor environment after its accumulation in tumors, triggering differential doxorubicin release and selectively killing tumor cells. This concept can be extended and improved by using other factors secreted by bacteria or materials to fabricate a unique tumor environment for differential drug delivery, showing potential applications in drug delivery.

ScFv-Decorated PEG-PLA-Based Nanoparticles for Enhanced siRNA Delivery to Her2+ Breast Cancer

Patients with Her2-overexpressing (Her2(+)) breast cancers generally have a poorer prognosis due to the high aggressiveness and chemoresistance of the disease. Small interfering RNA (siRNA) targeting the gene encoding polo-like kinase 1 (Plk1; siPlk1) has emerged as an efficient therapeutic agent for Her2(+) breast cancers. Poly(ethylene glycol)-block-poly(D,L-lactide) (PEG-PLA)-based nanoparticles for siRNA delivery were previously developed and optimized. In this study, for targeted delivery of siPlk1 to Her2(+) breast cancer, anti-Her2 single-chain variable fragment antibody (ScFv(Her2))-decorated PEG-PLA-based nanoparticles with si Plk1 encapsulation (ScFv(Her2)-NP(si) Plk1) are developed. With the rationally designed conjugation site, ScFv(Her2)-NP(siRNA) can specifically bind to the Her2 antigen overexpressed on the surface of Her2(+) breast cancer cells. Therefore, ScFv(Her2)-NP(si) Plk1 exhibits improved cellular uptake, promoted Plk1 silencing efficiency, and induced enhanced tumor cell apoptosis in Her2(+) breast cancer cells, when compared with nontargeted NP(si) Plk1. More importantly, ScFv(Her2)-NP(siRNA) markedly enhances the accumulation of siRNA in Her2(+) breast tumor tissue, and remarkably improves the efficacy of tumor suppression. Dose-dependent anti-tumor efficacy further demonstrates that ScFvHer2 -decorated PEG-PLA-based nanoparticles with siPlk1 encapsulation can significantly enhance the inhibition of Her2(+) breast tumor growth and reduce the dose of injected siRNA. These results suggest that ScFvHer2 -decorated PEG-PLA-based nanoparticles show great potential for targeted RNA interference therapy of Her2(+) breast tumor.