A novel gemcitabine derivative-loaded liposome with great pancreas-targeting ability.

Gemcitabine (Gem) is a standard first-line treatment for pancreatic cancer (PC). However, its chemotherapeutic efficacy is hampered by various limitations such as short half-life, metabolic inactivation, and lack of tumor localizing. We previously synthesized a lipophilic Gem derivative (Gem formyl hexadecyl ester, GemC16) that exhibited improved antitumor activity in vitro. In this study, a target ligand N,N-dimethyl-1,3-propanediamine was conjugated to 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[hydroxyl succinimidyl (polyethylene glycol-2000)] (DSPE-PEG-NHS) to form DSPE-PEG-2N. Then, pancreas-targeting liposomes (2N-LPs) were prepared using the film dispersion-ultrasonic method. GemC16-loaded 2N-LPs displayed near-spherical shapes with an average size distribution of 157.2 nm (polydispersity index (PDI) = 0.201). The encapsulation efficiency of GemC16 was up to 97.3% with a loading capacity of 8.9%. In human PC cell line (BxPC-3) and rat pancreatic acinar cell line (AR42J), cellular uptake of 2N-LPs was significantly enhanced compared with that of unmodified PEG-LPs. 2N-LPs exhibited more potent in vitro cytotoxicity against BxPC-3 and AR42J cell lines than PEG-LPs. After systemic administration in mice, 2N-LPs remarkably increased drug distribution in the pancreas. In an orthotopic tumor mouse model of PC, GemC16-bearing liposomes were more effective in preventing tumor growth than free GemC16. Among these treatments, 2N-LPs showed the best curative effect. Together, 2N-LPs represent a promising nanocarrier to achieve pancreas-targeting drug delivery, and this work would provide new ideas for the chemotherapy of PC.

High Tg and Thermo-Oxidatively Stable Thermosetting Polyimides Derived from a Carborane-Containing Diamine.

To provide high-temperature polyimide matrix resins, novel carborane-containing thermosetting polyimides are presented. First, the low-viscosity carborane-containing imide oligomers are synthesized using newly designed 1-(3-amino-4-tolyl)-2-(4-aminophenyl)-o-carborane and aromatic dianhydride as monomers, 4-phenylethynyl phthalic anhydride as the end-capping reagent. Followed by thermal curing, the resulting polyimides show high Tg (≥500 °C) and above 92.1% char yield at 800 °C both in nitrogen and air atmosphere due to the incorporation of the bulky carborane cages. Aging studies, performed at 400 and 500 °C for 5 h in air on a carborane-containing polyimide and a carborane-free polyimide, show that the polyimide with carborane groups possesses excellent thermo-oxidative stability. Moreover, the novel polyimides exhibit constant and relatively low coefficient of thermal expansion values over a wide range of temperature, indicative of a remarkable dimensional stability. Thus, this study clearly demonstrates the viability of the incorporation of carborane cages to access polyimide thermosets with ultrahigh Tg and thermo-oxidative stability.

Meta-para-linked octaaza[1(8)]cyclophanes and their polycationic states.

Octaazacyclophanes, octaaza[1(8)]m,p,m,p,m,p,m,p-cyclophane (2) and octaaza[1(8)]m,p,p,p,m,p,p,p-cyclophane (3), as ring-size extended congeners of tetraaza[1(4)]m,p,m,p-cyclophane were synthesized, and the electronic states of their polycationic species were investigated by quantum chemical calculations, electrochemical measurements (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)), UV-vis-NIR spectroelectrochemical measurements, and pulsed electron spin resonance (ESR) spectroscopy. These octaazacyclophanes exhibited multiredox activities depending on different linkage patterns along the macrocyclic molecular skeletons, and both molecules were oxidizable up to their respective octacations. Spectroelectrochemical measurements demonstrated that p-phenylenediamine (PD) moieties in 2 could be converted from the semiquinoidal structure to the quinoidal sturcture with increasing oxidation number, whereas higher oxidation states of 3 did not show definite quinoidal deformation of PD moieties. A pulsed ESR spectrum gave evidence about formation of the almost pure spin-triplet state for 3(2+), whereas the high-spin states of 2(2+) and 2(4+) are virtually degenerate with the competing low-spin states even at low temperatures, probably due to the fragility of spin-coupling pathway caused by facile conformational changes.

Synthesis of soluble poly(amide-ether-imide-urea)s bearing amino acid moieties in the main chain under green media (ionic liquid).

In this study, an optically active diamine, N,N'-(pyromellitoyl)-bis{N-[4(4-aminophenoxy)phenyl]-2-(4-methyl)pentanamide} (1) containing amino acid L-leucine was prepared in three steps. The step-growth polymerization of this chiral diamine with several diisocyanates in room temperature ionic liquid (IL), 1,3-dipropylimidazolium bromide as an environmentally friendly solvent and in a volatile organic solvent, is investigated. The polymerization yields and inherent viscosities of the resulting poly(amide-ether-imide-urea)s are compared in both solvents. The results show that the IL to be the superior polymerization media. All of the obtained polymers exhibited good solubility in some polar aprotic organic solvents such as N,N-dimethyacetamide, N,N-dimethyformamide, dimethyl sulfoxide while thermal stability was not disturbed based on thermogravimetric analysis and differential scanning calorimetry experiments. X-ray diffraction analysis of polymers shows that they are amorphous. The observation of optical rotation confirms the optical activity of prepared polymers.

Design of PEI-conjugated bio-reducible polymer for efficient gene delivery.

The poly(cystaminebis(acrylamide)-diaminohexane) (poly(CBA-DAH)) was designed previously as a bio-reducible efficient gene delivery carrier. However, the high weight ratio required to form the polyplexes between poly(CBA-DAH) with pDNA is still a problem that needs to be addressed. To solve this problem and increase the transfection efficiency, poly(ethylenimine) (PEI, 1.8 kDa) was conjugated to poly(CBA-DAH) via disulfide bond. The PEI conjugated poly(CBA-DAH) (PCDP) can bind with pDNA at a very low weight ratio of 0.5 and above, like PEI 25 kDa, and form the polyplexes with nano-size (102-128 nm) and positive surface charge (27-34 mV). PCDP and PCDP polyplexes had negligible cytotoxicity and indicated similar or better cellular uptake than the comparison groups such as PEI 25 kDa and Lipofectamine® polyplexes. To confirm the transfection efficiency, the plasmid DNA (pDNA) encoded with the luciferase reporter gene (gWiz-Luc) and green fluorescent protein reporter gene (GFP) were used and treated with PCDP into the A549, Huh-7, and Mia PaCa-2 cells. PCDP/pDNA polyplexes showed highest transfection efficiency in all tested cell lines. In the luciferase assay, PCDP polyplexes showed 10.2 times higher gene transfection efficiency than Lipofectamine® polyplexes in mimic in vivo conditions (30% FBS, A549 cells). The VEGF siRNA expressing plasmid (pshVEGF), which is constructed as a therapeutic gene by our previous work, was delivered by PCDP into the cancer cells. The VEGF gene expression of PCDP/pshVEGF polyplexes was dramatically lower than control and the VEGF gene silencing efficiencies of PCDP/pshVEGF (w/w; 10/1) polyplexes were 54% (A549 cells), 77% (Huh-7 cells), and 66% (Mia PaCa-2 cells). In addition, PCDP/pshVEGF had reduced cell viability rates of about 31% (A549 cells), 39% (Huh-7 cells), and 42% (Mia PaCa-2 cells) and showed better results than all comparison groups. In the transfection efficiency and VEGF silencing assay, PCDP polyplexes showed better results than poly(CBA-DAH) at 4-fold lower weight ratio. The data of all experiments demonstrate that the synthesized PCDP could be used for efficient gene delivery and could be widely applied.

Crosslinked Platform Coatings Incorporating Bioactive Signals for the Control of Biointerfacial Interactions.

Control over biointerfacial interactions on material surfaces is of significant interest in many biomedical applications and extends from the modulation of protein adsorption and cellular responses to the inhibition of bacterial attachment and biofilm formation. Effective control over biointerfaces is best achieved by reducing nonspecific interactions on the surface while also displaying specific bioactive signals. A poly(ethylene glycol) (PEG)-based multifunctional coating has been developed that provides effective reduction of protein fouling while enabling covalent immobilization of peptides in a one or two-step manner. The highly protein resistant properties of the coating, synthesized via the crosslinking of PEG diepoxide and diaminopropane, are confirmed via europium-labeled fibronectin adsorption and cell attachment assays. The ability to covalently incorporate bioactive signals is demonstrated using the cyclic peptides cRGDfK and cRADfK. L929 cells show enhanced attachment on the biologically active cRGDfK containing surfaces, while the surface remains nonadhesive when the nonbiologically active cRADfK peptide is immobilized. The crosslinked PEG-based coating also demonstrates excellent resistance toward Staphylococcus aureus attachment in a 48 h biofilm assay, achieving a >96% reduction compared to the control surface. Additionally, incorporation of the antimicrobial peptide melimine during coating formation further significantly decreases biofilm formation (>99%).

More lipophilic dialkyldiamine-based diazeniumdiolates: synthesis, characterization, and application in preparing thromboresistant nitric oxide release polymeric coatings.

The synthesis, characterization, and biomedical application in preparing more thromboresistant polymeric coatings for a series of lipophilic dialkyldiamine-based diazeniumdiolatesare described. Dialkylhexamethylenediamine diazeniumdiolates of the form RN[N(O)NO](-)(CH(2))(6)NH(2)(+)R, where R = CH(3), CH(2)CH(3), (CH(2))(2)CH(3), (CH(2))(3)CH(3), (CH(2))(4)CH(3,) (CH(2))(5)CH(3), and (CH(2))(11)CH(3), are prepared via reaction of the corresponding diamine with NO. The more lipophilic diazeniumdiolates [e.g., R = (CH(2))(3)CH(3)] can be incorporated into hydrophobic polymeric films (e.g., plasticized PVC), and the resulting materials release NO for extended periods of time upon exposure to PBS buffer. The mechanism of NO release from these films is examined in detail. More stable initial NO release can be achieved by adding lipophilic anionic species (e.g., tetraphenylborate derivative) to the polymeric material to buffer the activity of protons within the organic phase. It is shown that the use of these new lipophilic NO-donors in polymers provides the ability to tailor NO release rates for a variety of medical applications. As an example, polymers doped with N,N'-dibutylhexamethylenediamine diazeniumdiolate and a tetraphenylborate derivative are employed as coatings for vascular grafts in sheep. The NO release grafts exhibited enhanced performance and had an average 95% thrombus-free surface area compared to 42% for the corresponding control grafts when examined after 21d of implantation.

Improved synthesis of hyaluronic acid hydrogel and its effect on tissue augmentation.

HA-HMDA hydrogels were developed by direct amide bond formation between the carboxyl groups of hyaluronic acid (HA) and hexamethylenediamine (HMDA) with an optimized carboxyl group modification in the preliminary experiment. However, these HA-HMDA hydrogels transformed into an unstable liquid form after steam sterilization, and were problematic for application to actual dermal filler. A new method to overcome the problem of the previously developed HA-HMDA hydrogels is to prepare them by adjusting the pH in this study. Not only are these improved HA-HMDA hydrogels prepared with lower amounts of cross-linking and activation agents compared to the previously developed hydrogels, but they also maintain a stable form after steam sterilization. These improved HA-HMDA hydrogels showed higher viscoelasticity and longer lasting effects than the previous ones, despite the fact that the amount of the HMDA used as a cross-linking agent as well as 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and 1-hydroxybenzotriazole monohydrated (HOBt) used as activation agents were substantially reduced. According to an in vivo test using a wrinkled mouse model, the improved HA-HMDA hydrogels exhibited significantly improved tissue augmentation effects compared to a positive control of Restylane, which is widely used for the tissue augmentation throughout the world. Furthermore, histological analysis revealed excellent biocompatibility and safety of the improved synthesized HA-HMDA hydrogels.

Renewable rigid diamines: efficient, stereospecific synthesis of high purity isohexide diamines.

We report an efficient three-step strategy for synthesizing rigid, chiral isohexide diamines derived from 1,4:3,6-dianhydrohexitols. These biobased chiral building blocks are presently the subject of several investigations (in our and several other groups) because of their application in high-performance biobased polymers, such as polyamides and polyurethanes. Among the three possible stereo-isomers, dideoxy-diamino isoidide and dideoxy-diamino isosorbide can be synthesized from isomannide and isosorbide respectively in high yield with absolute stereo control. Furthermore, by using this methodology dideoxy-amino isomannide-a tricyclic adduct-was obtained starting from isoidide in high yield. Our improved synthetic route is a valuable advance towards meeting scale and purity demands for evaluating the properties of new biobased performance materials, which will benefit the development of these plastics.

Synthesis and in vitro cytotoxicity of novel lipophilic (diamine)platinum(II) complexes of salicylate derivatives.

Novel lipophilic (diamine)platinum(II) complexes of salicylate derivatives as the leaving groups were synthesized and characterized by elemental analysis, FAB(+)-MS, FT-IR, and (1)H NMR spectroscopy. Most of the resulting platinum complexes had high solubility in organic solvents such as ethanol, acetone, and ether, and had right partition coefficient suited to be encapsulated in liposomes. The pertinent complexes were evaluated for their in vitro cytotoxicity against A549 human lung carcinoma and SGC-7901 human gastric carcinoma cell lines. They showed better cytotoxic activity than carboplatin and oxaliplatin.

Synthesis of peptidomimetics using a polymer-bound Boc-linker.

Boc-resin-bound alpha-hydroxy-beta-amino-aldehydes are accessible starting from N-terminally bound amino acid esters by using Dondoni's C1-homologation reaction sequence. The conversion of these synthons to two different peptide mimetics--2-hydroxy-1,3-ethyl-diamines and gamma-hydroxy-delta-amino-vinyl sulfones--has been investigated. The successful transfer of the complex alpha-amino acid homologation reaction sequence into solid-phase chemistry demonstrates the potentials of the Boc-resin for synthesis of peptidomimetics.

A convenient procedure for the synthesis of nonsymmetrical bivalent selective serotonin reuptake inhibitors using polymer-supported reagents.

A convenient synthesis of nonsymmetrical bivalent inhibitors of the serotonin transporter is described. The synthesis utilizes polymer-supported reagents that allow for rapid access to novel bivalent ligands without the need for isolation or purification of synthetic intermediates.

Combinatorial lead optimization of [1,2]-diamines based on ethambutol as potential antituberculosis preclinical candidates.

Despite relatively modest potency, ethambutol (EMB, (S,S)-[N,N-di-2-amino-1-butanol]ethylenediamine) is a mainstay of contemporary chemotherapy for the treatment of tuberculosis. We have developed a solid-phase synthesis of 1,2-diamine analogues of EMB using a novel acylation-reduction sequence that is compatible with high-throughput 96-well format chemistry. Using this procedure, we have synthesized 63 238 diamine analogues in pools of 10 that are suitable for testing. MIC and a target-based reporter assay were used to direct deconvolution of 2796 individual compounds from these mixtures, and the 69 most potent molecules were resynthesized in milligram quantities for hit confirmation. Purification of these individual active diamine analogues allowed the identification of 26 compounds with activity equal to or greater than EMB. Amines which occurred most frequently in active compounds included many with large hydrophobic moieties, suggesting that optimization was perhaps selecting for the isoprenoid binding site of the arabinosyltransferase target of EMB. N-Geranyl-N'-(2-adamantyl)ethane-1,2-diamine (109), the most active of these diamines, displayed a 14-35-fold improvement in activity in vitro against Mycobacterium tuberculosis, as compared to EMB.

Dibasic inhibitors of human mast cell tryptase. Part 1: synthesis and optimization of a novel class of inhibitors.

The synthesis and optimization of a novel class of reversible and active-site directed dibasic inhibitors of human mast cell tryptase are described. The compounds were shown to be both remarkably potent and selective for tryptase with Ki values for optimized inhibitors in the picomolar range.