Transdermal Delivery of Metformin Utilizing Ionic Liquid Technology: Insight Into the Relationship Between Counterion Structures and Properties.

PURPOSE: The purpose of the present study was to explore the feasibility of transdermal delivery of metformin, a commonly used oral antidiabetic drug, by ionic liquid (IL) technology. METHODS: Metformin hydrochloride (MetHCl) was first transformed into three kinds of ILs with different counterions. The physicochemical properties of the obtained ILs were characterized in depth. The simulation of stable configuration and calculation of interaction energies were conducted based on density functional theory (DFT). Skin-PAMPA was used to evaluate the intrinsic transdermal permeation properties. The cytotoxicity assay of these ILs was conducted using HaCaT cells to evaluate the toxicity to skin. These metformin ILs were then formulated into transdermal patch, and the transdermal potential was further evaluated using in vitro dissolution test and skin permeation assay. Finally, the pharmacokinetic profiles of these metformin IL-containing patches were determined. RESULTS: Among all the three Met ILs, metformin dihexyl sulfosuccinate (MetDH) with proper overall physiochemical and biological properties demonstrated the highest relative bioavailability. Metformin docusate (MetD) with the highest lipophilicity and intrinsic transdermal permeability exhibited the most significant sustained release profile in vivo. Both MetDH and MetD were the promising candidates for further clinical investigations. CONCLUSIONS: Overall, the properties of ILs were closely related to the structures of counterion. IL technology provided the opportunities to finely tune the solid-state and biological properties of Metformin and facilitated the successful delivery by transdermal route.

Discovery of potent 2,4-difluoro-linker poly(ADP-ribose) polymerase 1 inhibitors with enhanced water solubility and in vivo anticancer efficacy.

Poly (ADP-ribose) polymerase 1 (PARP1) is overexpressed in a variety of cancers, especially in breast and ovarian cancers; tumor cells that are deficient in breast cancer gene 1/2 (BRCA1/2) are highly sensitive to PARP1 inhibition. In this study, we identified a series of 2,4-difluorophenyl-linker analogs (15-55) derived from olaparib as novel PARP1 inhibitors. Four potent analogs 17, 43, 47, and 50 (IC50=2.2-4.4 nmol/L) effectively inhibited the proliferation of Chinese hamster lung fibroblast V-C8 cells (IC50=3.2-37.6 nmol/L) in vitro, and showed specificity toward BRCA-deficient cells (SI=40-510). The corresponding hydrochloride salts 56 and 57 (based on 43 and 47) were highly water soluble in pH=1.0 buffered salt solutions (1628.2 µg/mL, 2652.5 µg/mL). In a BRCA1-mutated xenograft model, oral administration of compound 56 (30 mg·kg-1·d-1, for 21 d) exhibited more prominent tumor growth inhibition (96.6%) compared with the same dose of olaparib (56.3%); in a BRCA2-mutated xenograft model, oral administration of analog 43 (10 mg·kg-1·d-1, for 28 d) significantly inhibited tumor growth (69.0%) and had no negative effects on the body weights. Additionally, compound 56 exhibited good oral bioavailability (F=32.2%), similar to that of olaparib (F=45.4%). Furthermore, the free base 43 of the hydrochloride salt 56 exhibited minimal hERG inhibition activity (IC50=6.64 µmol/L). Collectively, these data demonstrate that compound 56 may be an excellent drug candidate for the treatment of cancer, particularly BRCA-deficient tumors.

2-{[3-Methyl-4-(2,2,2-trifluoro-eth-oxy)pyridin-2-yl]methyl-sulfan-yl}-1H-benzimidazole monohydrate: a monoclinic polymorph.

The title compound, C(16)H(14)F(3)N(3)OS·H(2)O, which had been previously characterized in the space group P-1 [Ren et al. (2011 ▶). Acta Cryst. E67, o270], has now been crystallized from 1-propanol in the monoclinic form in the space group P2(1)/c. While the triclinic form is a Z' = 2 crystal, the new monoclinic polymorph includes one main mol-ecule and one water lattice mol-ecule in the asymmetric unit. In the crystal, the water mol-ecule is sandwiched between neighboring main mol-ecules and behaves as both donor and acceptor in O-H⋯N and N-H⋯O hydrogen bonds with the imidazole N atoms. This pattern of chains parallel to [100] further inter-acts via O-H⋯N(pyridine) contacts.

2-{[3-Methyl-4-(2,2,2-trifluoro-eth-oxy)pyridin-2-yl]methyl-sulfan-yl}-1H-benzimidazole propan-2-ol monosolvate: a second monoclinic polymorph.

In the crystal structure of the title compound, C16H14F3N3OS·C3H8O, the mol-ecules are linked into chains along [010] via N-H⋯O and O-H⋯N hydrogen bonds. The triclinic form was reported by Ren et al. [(2011). Acta Cryst. E67, o270] and the first monoclinic form by Chen et al. [(2012). Acta Cryst. E68, o2015-o2016]. The fused five-and six-membered rings make a dihedral angle of 1.22 (2)°, while the benzene and pyridine rings make a dihedral angle of 10.15 (2)°.

1,3-Dihy-droxy-2-(hy-droxy-meth-yl)propan-2-aminium formate.

The title compound, C(4)H(12)NO(3) (+)·CHO(2) (-), was obtained from 1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-aminium acetate and ethyl formate. In the crystal, the cations and anions are held together by inter-molecular N-H⋯O and O-H⋯O hydrogen bonds.

2-{[3-Methyl-4-(2,2,2-trifluoro-eth-oxy)pyridin-2-yl]methyl-sulfan-yl}-1H-benzimidazole monohydrate.

The asymmetric unit of the title compound, C(16)H(14)F(3)N(3)OS·H(2)O, contains two independent mol-ecules (A and B) and two water mol-ecules, one of which is disordered over two positions in a 0.790 (8):0.210 (8) ratio. The mol-ecular conformations are close, the benzimidazole mean plane and pyridine ring forming dihedral angles of 1.8 (3) and 0.1 (2)° in mol-ecules A and B, respectively. The water mol-ecules are involved in formation of two independent hydrogen-bonded chains via N-H⋯O and O-H⋯N hydrogen bonds. Chains propagating along the a axis are formed by mol-ecule A and one independent water mol-ecule, while chains propagating along the b axis are formed by mol-ecule B and the other independent water mol-ecule. The crystal packing exhibits π-π inter-actions, as indicated by short distances of 3.607 (3) and 3.701 (3) Šbetween the centroids of the imidazole and pyridine rings of neighbouring mol-ecules.

Development of gliclazide ionic liquid and the transdermal patches: An effective and noninvasive sustained release formulation to achieve hypoglycemic effects.

Ionic liquids (IL) technology provides a useful platform to achieve the topical delivery of therapeutic agents, because of its capability to improve skin permeability. While the majority of the researches aimed to achieve local action by topical IL delivery, systemic action of therapeutic agents by local topical application has rarely been reported. In the present work, Gliclazide (GLI), a second-generation sulfonylurea drug was transformed into an IL with tributyl(tetradecyl)phosphonium for the first time. The physicochemical properties of this IL were systematically characterized by DSC, TGA, FT-IR, NMR, and HPLC. The transdermal patch based on this IL was further prepared using DURO-TAK®87-4098. The fabricated gliclazide based ionic liquid [P6,6,6,14][GLI] transdermal patch displayed satisfactory in vitro and in vivo performance. The [P6,6,6,14][GLI] patch released 88.17% of the loaded drug within a 3-day period in the in vitro dissolution test, confirming its sustained release property. Meanwhile, GLI effectively permeated through the artificial skin from [P6,6,6,14][GLI] transdermal patch in the in vitro skin permeation test, with the permeation rate and lag time of 16.571 ± 0.328 µg/cm2/h and 3.027 ± 0.154 h respectively. The [P6,6,6,14][GLI] transdermal patch showed favorable PK profile in rat as compared with GLI oral suspension. The relative bioavailability of GLI reached 92.06% of GLI oral suspension, while the Cmax was significantly reduced. Most importantly, [P6,6,6,14][GLI] transdermal patch demonstrated superior hypoglycemic effect to the oral suspension both in the fasted and fed condition, confirming the feasibility of systemic action by local topical delivery of IL. In addition, the [P6,6,6,14][GLI] transdermal patch caused no skin irritation based on histopathological analysis.

Development of a gliclazide ionic liquid and its mesoporous silica particles: an effective formulation strategy to improve oral absorption properties.

Ionic liquid (IL) technology provides a useful platform to enhance the oral absorption of therapeutic agents. In the present work, gliclazide (GLI), a second-generation sulfonylurea drug was transformed into an IL with tetrabutylphosphonium. The physicochemical properties of this IL were systematically characterized by DSC, TGA, FT-IR, NMR, and HPLC. For the further preparation development, a solution stability test was conducted. GLI-based IL could improve the solution stability in a neutral environment. To assess oral potential, the solubility characteristics including equilibrium solubility, 24 h kinetic saturation solubilities and supersaturation profiles were first explored. Significant enhancement of solubilities, supersaturation ratio and duration of supersaturation was found for the synthesized IL. Computational methodology was utilized to better understand the improved solubility results. From the simulated results, [TBP][GLI] showed a longer time period when the distance between cation and anion was far above the baseline and a higher deviation degree, indicating less stable ion pairs of [TBP][GLI] in an aqueous environment and it being easy for the cation and anion to tear apart and form interactions with water molecules. The prepared [TBP][GLI] exhibited intestinal transportation ability and safety as evidenced by the in vitro gastrointestinal tract artificial membrane permeability assays (GIT-PAMPA) and cytotoxicity experiments with Caco-2 cells. A mesoporous carrier, AEROPERL® 300 Pharma, was chosen to load the IL and then encapsuled into enteric capsules. The prepared oral capsules containing GLI-based IL loaded mesoporous silica particles released fast and could realize 100% release within 60 min.

Enhancing the solubility of natural compound xanthotoxin by modulating stability via cocrystallization engineering.

A comprehensive cocrystal study for the insoluble natural pharmaceutical compound xanthotoxin (XT) was conducted, in which xanthotoxin-para aminobenzoic acid (XT-PABA) and xanthotoxin-oxalic acid (XT-OA) cocrystals were obtained. The xanthotoxin cocrystals were characterized by powder X-ray diffraction, thermal analysis, and FT-IR spectra, and the crystal structures were determined by single-crystal X-ray diffraction. Crystal structures and thermal analysis showed that XT-OA was more stable than XT-PABA. Energy framework calculation indicated that H-bond and π···π interactions generated in XT-OA were stronger than that in XT-PABA and xanthotoxin. The powder dissolution experiments of xanthotoxin and its cocrystals suggested the XT-OA cocrystal might be applied as an alternative formulation of API, on account of its enhanced solubility and stability in the hydrochloric acid buffer solution (pH 1.2). The cocrystallization engineering can prolong the enhanced apparent solubility via modulating the stability.

[Spectroscopic diagnoses of glow discharge plasma for the carbon nitride growth process].

Plasma diagnostics is performed during dc. glow discharge plasma-enhanced chemical vapor deposition (PECVD) on nitride thin films using optical emission spectra. Several molecular bands such as the second positive series of N2 transitions, the first negative series of N2+ and the CN, NH violet bands are identified. Variations of the emission intensities of N2(337.1 nm), N2+(391.4 nm) and CN(388.3 nm) are investigated as the function of the percentage of H2, discharge current and deposition pressure. The related excitation mechanism of the species emission is discussed. Experimental results show that adding a small amount of H2(about 5%) into the gas source will be beneficial to produce all the active species. Higher discharge current will result in an increase of the active species concentration while there is maximum emission intensity at medium gas pressure at about 4 kPa. The collisions between the species, including metastable nitrogen and hydrogen are related with the concentration variations of the measured species. All the results and discussion provide reference data for optimizing the deposition parameters and controlling the deposition process in the synthesis of carbon nitride thin films.