Hanmei Li

A cell-specific poly(ethylene glycol) derivative with a wheat-like structure for efficient gene delivery.

A novel anionic PEG derivative with a wheat-like structure, PEG-poly(AGE-Suc), was synthesized. The spikelet part of this polymer consisting of 9.3 pairs of carboxylic acid side chains was conjugated at one end of the PEG chain. The neutral linear PEG(1580) was designed as the stalk part to improve the biocompatibility of the vectors. The obtained polymer PEG-poly(AGE-Suc) was further modified by folate (FA) at the distal end to achieve the cell-specific targeting. It was confirmed that the negatively charged FA-PEG-poly(AGE-Suc) could coat the positively charged PEI 25K/DNA complex and form a ternary complex by electrostatic interaction. The addition of FA-PEG-poly(AGE-Suc) could change the positive charge of PEI 25K/DNA complexes to negative with no influence on the diameter. The ternary complex with the coat of FA-PEG-poly(AGE-Suc) could effectively condense DNA and protect it from degradation by DNase I. The nonspecific interaction between PEI 25K/DNA complexes and blood components was also significantly reduced by the addition of anionic PEG. The ternary complex PEI 25K/DNA/FA-PEG-poly(AGE-Suc) exhibited a 12-fold higher transfection efficiency on 293T cells compared to PEI 25K/DNA in the serum-containing medium. The competitive folate inhibition assay demonstrated that the higher transfection efficiency of PEI 25K/DNA/FA-PEG-poly(AGE-Suc) was attributed to the folate molecule conjugated to the distal end of FA-PEG-poly(AGE-Suc). The ternary complex PEI 25k/DNA/FA-PEG-poly(AGE-Suc) with low side effects and high transfection efficiency may be a novel effective gene delivery system.

Intracellular redox potential-responsive micelles based on polyethylenimine-cystamine-poly(ε-caprolactone) block copolymer for enhanced miR-34a delivery

An amphiphilic cationic graft polymer polyethylenimine-cystamine-poly(e-caprolactone) (PSSP) with intracellular redox potential-responsive cleavable ability was synthesized for the first time by coupling poly(e-caprolactone) (PCL) to polyethylenimine (PEI) via a bio-cleavable disulfide linkage. PSSP based micelles, which can degrade in the intracellular reducing environment, were developed as smart non-viral gene vectors for enhanced miR-34a delivery. The PSSP/miR-34a complexes showed effective and stable miRNA condensation with a narrow particle size of around 120 nm. The gel retardation assay showed that PSSP micelles could protect miRNA from RNase and achieve intracellular release of miRNA in the reducing environment. Compared with PEI-25k, PSSP revealed comparable transfection efficiencies in the B16F10 cell with less cytotoxicity. The B16F10 cell treated with PSSP/miR-34a complexes showed a significantly higher cell apoptosis than the PEI-25k/miR-34a complexes. These encouraging results indicated that PSSP may possess promising potential as a smart non-viral gene vector with low cytotoxicity, intracellular redox potential to trigger miRNA release and high transfection efficiency.

pH-sensitive polymeric micelles for targeted delivery to inflamed joints.

Abstract Effective treatment for rheumatoid arthritis is hindered by the lack of drugs that selectively target inflamed joints. Liposomes, nanoparticles and conventional micelles loaded with limited amounts of drugs may be unstable in the circulation and result in uncontrolled drug release kinetics. Here we developed a new drug delivery system of pH‐sensitive polymeric micelles based on an acid‐labile hydrazone bond. Amphiphilic conjugates of a PEG‐based derivative and the hydrophobic drug prednisolone (PD) self‐assembled into PD micelles with a drug loading of 19.29%. When the micelles reached the acidic environment of synovial fluid, the hydrazone bonds hydrolyzed, releasing free PD. Intravenous injection of PD micelles into mice with collagen‐induced arthritis led to PD accumulation in affected joint tissues. PD concentrations in plasma and joints of arthritic mice were significantly higher after injection with PD micelles than after injection with free PD. The enhancement effect in joints was 4.63‐fold based on the area under the concentration‐time curve and 2.50‐fold based on the maximum concentration (Cmax). In vivo pharmacodynamics experiments showed PD micelles to have better anti‐inflammatory and disease‐modifying effects than free PD. Our results indicate the promise of PD micelles for targeted drug delivery in inflammatory disease. Graphical abstract The pH‐sensitive APN‐PD amphiphilic conjugates self‐assembled into PD micelles. The hydrazone bonds hydrolyzed, releasing free PD in the acidic environment of synovial fluid, showing better anti‐inflammatory and disease‐modifying effects. Figure. No Caption available.

Targeting NF-kB signaling with polymeric hybrid micelles that co-deliver siRNA and dexamethasone for arthritis therapy

The transcription factor NF-kB plays a pivotal role in the pathogenesis of rheumatoid arthritis. Here we attempt to slow arthritis progression by co-delivering the glucocorticoid dexamethasone (Dex) and small-interfering RNA targeting NF-kB p65 using our previously developed polymeric hybrid micelle system. These micelles contain two similar amphiphilic copolymers: polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethyleneglycol (PCL-PEG). The hybrid micelles loaded with Dex and siRNA effectively inhibited NF-kB signaling in murine macrophages more efficiently than micelles containing either Dex or siRNA on their own. In addition, the co-delivery system was able to switch macrophages from the M1 to M2 state. Injecting hybrid micelles containing Dex and siRNA into mice with collagen-induced arthritis led the therapeutic agents to accumulate in inflamed joints and reduce inflammation, without damaging renal or liver function. Thus, blocking NF-kB activation in inflammatory tissue using micelle-based co-delivery may provide a new approach for treating inflammatory disease.

Novel oral administrated paclitaxel micelles with enhanced bioavailability and antitumor efficacy for resistant breast cancer

Paclitaxel (PTX) is a widely used antineoplastic drug in clinic. Due to poor aqueous solubility, it is administrated by intravenous infusion of cremophor EL containing formulation with serious adverse effects. The low oral bioavailability is a great challenge for oral formulation development. In addition, P-gp mediated multidrug resistance limit its clinical use in various resistant cancers. In this study, a novel super-antiresistant PTX micelle formulation for oral administration was developed. A P-gp inhibitor, bromotetrandrine (W198) was co-encapsulated in the micelle. The micelles were composed of Solutol HS 15 and d-a-tocopheryl polyethylene glycol succinate to avoid Cremophor EL induced toxicity. The micelles were round with a mean particle size of ∼13nm and an encapsulation efficiency of ∼90%. A series of in vitro evaluations were performed in non-resistant MCF-7 cells and resistant MCF-7/Adr cells. The super-antiresistant PTX micelles showed higher cell uptake efficiency, significantly increased cytotoxicity and antimitotic effect in drug resistant MCF-7/Adr cells when compared with Taxol and other PTX micelle formulations. Compared with Taxol, the super-antiresistant PTX micelles significantly improved bioavailability after oral administration in rats, and inhibited tumor growth in multidrug resistance xenografted MCF-7/Adr nude mice. In summary, the noval super-antiresistant PTX micelles showed a great potential for oral delivery of PTX against resistant breast cancer.

Design and Validation of PEG-Derivatized Vitamin E Copolymer for Drug Delivery into Breast Cancer

This study examined the ability of amphiphilic poly(ethylene glycol) (PEG) derivatives to assemble into micelles for drug delivery. Linear PEG chains were modified on one end with hydrophobic vitamin E succinate (VES), and PEG and VES were mixed in different molar ratios to make amphiphiles, which were characterized in terms of critical micelle concentration (CMC), drug loading capacity (DLC), serum stability, tumor spheroid penetration and tumor targeting in vitro and in vivo. The amphiphile PEG5K-VES6 (PAMV6), which has a wheat-like structure, showed a CMC of 3.03 × 10(-6) M, good serum stability, and tumor accumulation. The model drug, pirarubicin (THP), could be efficiently loaded into PAMV6 micelles at a DLC of 24.81%. PAMV6/THP micelles were more effective than THP solution at inducing cell apoptosis and G2/M arrest in 4T1 cells. THP-loaded PAMV6 micelles also inhibited tumor growth much more than free THP in a syngeneic mouse model of breast cancer. PAMV6-based micellar systems show promise as nanocarriers for improved anticancer chemotherapy.

Turning the Old Adjuvant from Gel to Nanoparticles to Amplify CD8+ T Cell Responses

Abstract Due to its safety and efficacy, aluminum hydroxide is used as an immune adjuvant in human vaccines for over 80 years. Being a Th2 stimulator, the classical gel‐like adjuvant, however, fails to generate CD8+ T cell responses, which are important for cancer vaccines. Here, aluminum hydroxide is turned from gel into nano‐sized vaccine carriers AlO(OH)‐polymer nanoparticles (APNs) to promote their lymphatic migration. After actively uptaken via scavenger receptor‐A by antigen‐presenting cells (APCs) resident in lymph nodes (LNs), APNs destabilize lysosomes resulting in efficient cytosolic delivery and cross‐presentation of antigens. It is demonstrated that administration of APNs loaded with ovalbumin (OVA) and CpG led to the codelivery of both cargos into APCs in LNs, leading to their activation and subsequent adaptive immunity. A prime‐boost strategy with low doses of OVA (1.5 µg) and CpG (0.45 µg) induces potent CD8+ T cell responses and dramatically prolongs the survival of B16‐OVA tumor‐bearing mice. More impressively, when using B16F10 lysates instead of OVA as antigen, substantial antitumor effects on B16F10 tumor model are observed by using APN‐CpG. These results suggest the great potential of APNs as vaccine carriers that activate CD8+ T cell responses and the bright prospect of aluminum adjuvant in a nanoparticle formulation.

Rational design of Polymeric Hybrid Micelles to Overcome Lymphatic and Intracellular Delivery Barriers in Cancer Immunotherapy

Poor distribution of antigen/adjuvant to target sites and inadequate induction of T cell responses remain major challenges in cancer immunotherapy because of the lack of appropriate delivery systems. Nanocarrier-based antigen delivery systems have emerged as an innovative strategy to improve vaccine efficacy. Here we present polymeric hybrid micelles (PHMs) as a simple and potent antigen/adjuvant co-delivery system with highly tunable properties. PHMs consist of two amphiphilic diblock copolymers, polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethyleneglycol (PCL-PEG). PHMs with different proportions of cationic PCL-PEI were prepared and loaded with tyrosinase-related protein 2 (Trp2) peptide and adjuvant CpG oligodeoxynucleotide to generate the Trp2/PHM/CpG co-delivery system. Lymphatic and intracellular antigen delivery as a function of PCL-PEI proportion was evaluated in vitro and in vivo. PHMs containing 10% (w/w) PCL-PEI (Trp2/PHM10/CpG) showed the optimal balance of good distribution to lymph nodes, strong immunization effect after subcutaneous administration, and low toxicity to dendritic cells. In a mouse model of B16F10 melanoma, Trp2/PHM10/CpG showed significantly higher antigen-specific cytotoxic T lymphocyte activity and greater anticancer efficacy than Trp2/PHM0/CpG without PCL-PEI or a mixture of free Trp2 and CpG. These results provide new insights into how cationic segments affect the efficiency of antigen delivery by cationic nanocarriers. They also suggest that PHMs can serve as a structurally simple and highly tunable platform for co-delivery of antigen and adjuvant in cancer immunotherapy.