Reactive oxygen species (ROS)-responsive ferrocene-polymer-based nanoparticles for controlled release of drugs.

Ferrocene-containing nanoparticles show reversible redox activity that could trigger drug release mediated by reactive oxygen species (ROS). In this study, four ferrocene-containing polymers, comprising ferrocenylmethyl methacrylate (FMMA)-methacrylic acid (MA) random copolymers, i.e., poly(FMMA-r-MA), were synthesized via radical polymerization, resulting in self-assembled ferrocene nanoparticles (FNPs) with outstanding performance in environments in which ROS are present. These spherical FNPs have tunable diameters ranging from 270 nm to 180 nm and surface charges from -20 mV to -50 mV. Importantly, the diameters and surface charges of the FNPs changed dramatically after 2 h of post-treatment using 0.4 M hydrogen peroxide (H2O2) as the oxidant, indicating that the FNPs were highly ROS-sensitive. Furthermore, the controlled release of a model drug from the FNPs, reflected in the release profiles, indicates that these novel FNPs could be potentially used as drug carriers for the effective therapy of ROS-related diseases such as cancer and inflammation.

Design, synthesis and biological evaluation of glutamic acid derivatives as anti-oxidant and anti-inflammatory agents.

A series of glutamic acid derivatives was synthesized and evaluated for their antioxidant activity and stability. We found several potent and stable glutamic acid derivatives. Among them, compound 12b exhibited good in vitro activity, chemical stability and cytotoxicity. A prototype compound 12b showed an anti-inflammatory effect in LPS-stimulated RAW 264.7 cell lines and in a zebrafish model.

An approach for half-life extension and activity preservation of an anti-diabetic peptide drug based on genetic fusion with an albumin-binding aptide.

Although the peptide, exenatide, has been widely used as a drug for the treatment of type 2 diabetes, its short plasma half-life requires frequent subcutaneous injection, resulting in poor patient compliance in addition to side effects such as infection at the sites of injection. Here, we report a novel long-acting fusion peptide comprising exenatide and a human serum albumin (HSA)-binding aptide. A phage display screen of a library of aptides, yielded an HSA-specific aptide (APTHSA) that bound HSA with a Kd of 188nM. The recombinant fusion peptide comprising exenatide and APTHSA (exenatide-APTHSA) was expressed in Escherichia coli and purified by affinity and size-exclusion chromatography. The resulting exenatide-APTHSA fusion peptide showed glucose-induced insulin secretion activity similar to that of native exenatide when tested in vitro using the INS-1 cell line. A pharmacokinetic analysis of exenatide-APTHSA after subcutaneous administration revealed a 4-fold longer plasma half-life (1.3 vs. 0.35h) compared with exenatide. Furthermore, exenatide-APTHSA showed significantly improved anti-hyperglycemic effects in oral glucose tolerance tests and enhanced hypoglycemic effects compared with exenatide in a db/db type 2 diabetes mouse model. These results suggest that the exenatide-APTHSA fusion peptide could be used as a potential anti-diabetic agent for the treatment of type 2 diabetes.

Effects of gold nanoparticle-based vaccine size on lymph node delivery and cytotoxic T-lymphocyte responses.

Although it has been shown that the size of nanoparticle-based vaccines is a key determining factor for the induction of immune responses, few studies have provided detailed analyses of thresholds or critical sizes of nanoparticle vaccines. Here we report effects of the size of gold nanoparticle (GNP)-based vaccines on their efficiency of delivery to lymph nodes (LNs) and induction of CD8+ T-cell responses. We further propose a threshold size of GNPs for use as an effective vaccine. To examine the effects of GNP size, we synthesized GNPs with diameters of 7, 14 and 28nm, and then conjugated them with recombinant ovalbumin (OVA) as a model antigen. The resulting OVA-GNPs had hydrodynamic diameter (HD) of ~10, 22, and 33nm for 7, 14 and 28nm GNPs, respectively and exhibited a size-dependent increase in cellular uptake by dendritic cells (DCs) and subsequent T-cell cross-priming and activation. Upon injection into a mouse footpad, both 22- and 33-nm OVA-GNPs showed much higher delivery efficiency to draining LNs than did 10-nm OVA-GNPs. An ex vivo restimulation assay using OVA as an antigen revealed that frequencies of OVA-specific CD8+ T cells were higher in mice immunized with 22- and 33-nm OVA-GNPs than in those immunized with 10-nm OVA-GNPs; moreover, these cells were shown to be poly-functional. In a tumor-prevention study, 22-nm OVA-GNPs showed greater antitumor efficacy, and higher infiltration of CD8+ T-cells and greater tumor cell apoptosis and cell death than 10-nm OVA-GNPs. Taken together, our results suggest that the size threshold for induction of potent cellular responses and T-cell poly-functionality by GNPs lies between 10nm and 22nm, and highlight the importance of nanoparticle size as a critical parameter in designing and developing nanoparticle-based vaccines.

Effect of PEG pairing on the efficiency of cancer-targeting liposomes.

Standardized poly(ethylene glycol)-modified (PEGylated) liposomes, which have been widely used in research as well as in pre-clinical and clinical studies, are typically constructed using PEG with a molecular weight of 2000 Da (PEG(2000)). Targeting ligands are also generally conjugated using various functionalized PEG(2000)). However, although standardized protocols have routinely used PEG(2000), it is not because this molecular weight PEG has been optimized to enhance tumor uptake of nanoparticles. Herein, we investigated the effect of various PEG lipid pairings--that is, PEG lipids for targeting-ligand conjugation and PEG lipids for achieving 'stealth' function--on in vitro cancer cell- and in vivo tumor-targeting efficacy. A class of high-affinity peptides (aptides) specific to extra domain B of fibronectin (APT(EDB)) was used as a representative model for a cancer-targeting ligand. We synthesized a set of aptide-conjugated PEGylated phospholipids (APT(EDB)­PEG(2000))­DSPE and APT(EDB)­PEG(2000))­DSPE) and then paired them with methoxy-capped PEGylated phospholipids with diverse molecular weights (PEG(2000)), PEG(2000)), PEG(2000)), and PEG(2000))) to construct various aptide-conjugated PEGylated liposomes. The liposomes with APT(EDB)­PEG(2000))/PEG(2000)) and APT(EDB)­PEG(2000))/PEG(2000)) pairings had the highest uptake in EDB-positive cancer cells. Furthermore, in a U87MG xenograft model, APT(EDB)­PEG(2000))/PEG(2000)) liposomes retarded tumor growth to the greatest extent, followed closely by APT(EDB)­PEG(2000))/PEG(2000)) liposomes. Among the PEGylated liposomes tested, pairs in which the methoxy-capped PEG length was about half that of the targeting ligand-displaying PEG exhibited the best performance, suggesting that PEG pairing is a key consideration in the design of drug-delivery vehicles.

Gold nanoparticles displaying tumor-associated self-antigens as a potential vaccine for cancer immunotherapy.

Golden vaccine for cancers. Gold nanoparticles enable efficient antigen delivery to dendritic cells and then activate the cells to facilitate cross-presentation, inducing antigen-specific cytotoxic T-lymphocyte responses for effective cancer therapy.

A specific STAT3-binding peptide exerts antiproliferative effects and antitumor activity by inhibiting STAT3 phosphorylation and signaling.

STAT3 promotes the survival, proliferation, metastasis, immune escape, and drug resistance of cancer cells, making its targeting an appealing prospect. However, although multiple inhibitors of STAT3 and its regulatory or effector pathway elements have been developed, bioactive agents have been somewhat elusive. In this report, we report the identification of a specific STAT3-binding peptide (APTSTAT3) through phage display of a novel "aptide" library. APTSTAT3 bound STAT3 with high specificity and affinity (∼231 nmol/L). Addition of a cell-penetrating motif to the peptide to yield APTSTAT3-9R enabled uptake by murine B16F1 melanoma cells. Treatment of various types of cancer cells with APTSTAT3-9R blocked STAT3 phosphorylation and reduced expression of STAT targets, including cyclin D1, Bcl-xL, and survivin. As a result, APTSTAT3-9R suppressed the viability and proliferation of cancer cells. Furthermore, intratumoral injection of APTSTAT3-9R exerted potent antitumor activity in both xenograft and allograft tumor models. Our results offer a preclinical proof-of-concept for APTSTAT3 as a tractable agent for translation to target the broad array of cancers harboring constitutively activated STAT3.

Oral delivery of an anti-diabetic peptide drug via conjugation and complexation with low molecular weight chitosan.

Despite the therapeutic potential of exendin-4 as a glucagon-like peptide-1 (GLP-1) mimetic for the treatment of type 2 diabetes, its utility has so far been limited because of the low level of patient compliance due to the requirement for frequent injections. In this study, an orally available exendin-4 was produced by conjugating it to low molecular weight chitosan (LMWC). Conjugation between the LMWC and cysteinylated exendin-4 was carried out using a cleavable linker system in order to maximize the availability of the active peptide. The LMWC-exendin-4 conjugate formed a nanoparticle structure with a mean particle size of 101 ± 41 nm through complexation between the positively charged LMWC backbone and the negatively charged exendin-4 of individual conjugate molecules. The biological activity of the LMWC-exendin-4 conjugate was evaluated in an INS-1 cell line. The LMWC-exendin-4 conjugate stimulated insulin secretion in a dose dependent manner as similar as that of native exendin-4. From the pharmacokinetic study after oral administration of the conjugate, a C(max) value of 344 pg/mL and a T(max) of 6 h were observed, and the bioavailability, relative to the subcutaneous counterpart, was found to be 6.4%. Furthermore, the absorbed exendin-4 demonstrated a significantly enhanced hypoglycemic effect. These results suggest that the LMWC-exendin-4 conjugate could be used as a potential oral anti-diabetic agent for the treatment of type 2 diabetes.