Stability,liposome interaction,and in vivo pharmacology of ghrelin in liposomal suspensions

Ghrelin is an appetite-stimulating peptide hormone. It is a pharmacologically interesting peptide because of its involvement in e.g. appetite and metabolism, but it has a very short half-life in the body. Ghrelin carries a Ser-3-octanoyl group, and it has previously been suggested that acylated peptides can bind to or be incorporated into liposomes. Therefore, neutral dipalmitoylphosphatidylcholine (DPPC) liposomes and phosphatidylcholine:cholesterol (PC:Chol) (70:30) liposomes as well as negatively charged dipalmitoylphosphatidylcholine:dipalmitoylphosphatidylserine (DPPC:DPPS) liposomes (70:30) were prepared, and ghrelin was added. The chemical and physical stability of ghrelin was examined. Affinity capillary electrophoresis (ACE) revealed an interaction between ghrelin and the negatively charged (DPPC:DPPS) liposomes, whereas only very small affinities were discerned in the other liposomal formulations of ghrelin. Differential scanning calorimetry showed no changes in phase transitions (T_m). In vivo pharmacokinetics following subcutaneous administration of ghrelin in buffer and in the liposomal formulations was examined in rats. The PC:Chol formulation had a longer-lasting effect as compared to the ghrelin buffer solution and the other two liposomal formulations. The prolonged effect of the PC:Chol formulation is suggested not to be caused by association between ghrelin and the liposome.     

Disposition and biotransformation of C-Benzo(a)pyrene in a pig ear skin model: Ex vivo and in vitro approaches

Biotransformation of chemicals by the skin is a critical determinant of systemic exposure in humans following dermal absorption. Pig ear skin potentially represents a valuable alternative model since it closely resembles to human skin. We developed an ex vivo pig ear skin system which absorption, diffusion and metabolic capabilities were investigated using benzo(a)pyrene [B(a)P] as a model molecule. The potential of the ex vivo pig ear skin model to biotransform xenobiotics was compared with metabolic data obtained using dermal and hepatic microsomes from human and pig. ¹⁴C-B(a)P [50–800 nmol] was applied on the surface of skin models. The diffusion and the production of B(a)P metabolites were quantified by radio-HPLC, LC–MS/MS and NMR. B(a)P was extensively metabolized by pig ear skin explants, the major metabolites being B(a)P-glucuronide and sulfate conjugates. B(a)P-OHs, B(a)P-diols, B(a)P-catechols and B(a)P-diones were also identified. In the pig ear skin model developed, skin diffusion was maintained over 72 h and both phase I and phase II activities were expressed, with the formation of similar metabolites as produced in incubations with liver and skin microsomal fractions. This ex vivo model, which combines a functional skin barrier and active biotransformation capabilities, appears to represent a valuable alternative tool in transdermal exposure studies.     

Enhanced cellular delivery of idarubicin by surface modification of propyl starch nanoparticles employing pteroic acid conjugated polyvinyl alcohol

Enhanced intracellular internalization of the anti-cancer active idarubicin (IDA) was achieved through appropriate surface modification of IDA loaded propyl starch nanoparticles. This was conducted by synthesizing pteroic acid modified polyvinyl alcohol (ptPVA) and employing this stabilizer for formulating the said nanoparticles. Pteroic acid attached at the nanoparticles improved the surface protein adsorption of the nanoparticle, a condition which the nanoparticles would largely experience in vitro and in vivo and hence improve their cellular internalization.Spherical, homogenous IDA nanoparticles (214 ± 5 nm) with surface modified by ptPVA were formulated using the solvent emulsification-diffusion technique. The encapsulation efficiency and drug loading amounted around 85%. In vitro release studies indicated a controlled release of IDA. Safety and efficacy of the nanoparticles was confirmed by suitable cellular cytotoxicity assays. Protein binding studies indicated a higher adsorption of the model protein on nanoparticles formulated with ptPVA as compared to PVA. Cellular uptake studies by confocal laser scanning microscopy revealed a higher cellular uptake of ptPVA stabilized nanoparticles thus confirming the proposed hypothesis of higher protein adsorption being responsible for higher cellular internalization.     

Formulation and optimization of nanoemulsion using antifungal lipid and surfactant for accentuated topical delivery of Amphotericin B

The objective of the study was to develop, optimize and evaluate a nanoemulsion (NE) of Amphotericin B (AmB) using excipients with inherent antifungal activities (Candida albicans and Aspergillus niger) for topical delivery. AmB-loaded NE was prepared using Capmul PG8 (CPG8), labrasol and polyethylene glycol-400 by spontaneous titration method and evaluated for mean particle size, polydispersity index, zeta potential and zone of inhibition (ZOI). NE6 composed of CPG8 (15%w/w), S_mix (24%w/w) and water (61%w/w) was finally selected as optimized NE. AmB-NE6 was studied for improved in vitro release, ex vivo skin permeation and deposition using the Franz diffusion cell across the rat skin followed with drug penetration using confocal laser scanning microscopy (CLSM) as compared to drug solution (DS) and commercial Fungisome^®. The results of in vitro studies exhibited the maximum ZOI value of NE6 as 19.1?±?1.4 and 22.8?±?2.0?mm against A. niger and C. albicans, respectively, along with desired globular size (49.5?±?1.5?nm), zeta potential (?24.59?mV) and spherical morphology. AmB-NE6 revealed slow and sustained release of AmB as compared to DS in buffer solution (pH 7.4). Furthermore, AmB-NE6 elicited the highest flux rate (22.88?±?1.7?μg/cm²/h) as compared to DS (2.7?±?0.02?μg/cm²/h) and Fungisome^® (11.5?±?1.0?μg/cm²/h). Moreover, the enhancement ratio and drug deposition were found to be highest in AmB-NE6 than DS across the stratum corneum barrier. Finally, CLSM results corroborated enhanced penetration of the AmB-NE6 across the skin as compared to Fungisome^® and DS suggesting an efficient, stable and sustained topical delivery.     

Alginate coated chitosan core shell nanoparticles for oral delivery of enoxaparin: In vitro and in vivo assessment

The objective of present research work was to develop alginate coated chitosan core shell nanoparticles (Alg-CS-NPs) for oral delivery of low molecular weight heparin, enoxaparin. Chitosan nanoparticles (CS-NPs) were synthesized by ionic gelation of chitosan using sodium tripolyphosphate. Core shell nanoparticles were prepared by coating CS-NPs with alginate solution under mild agitation. The Alg-CS-NPs were characterized for surface morphology, surface coating, particle size, polydispersity index, zeta potential, drug loading and entrapment efficiency using SEM, Zeta-sizer, FTIR and DSC techniques. Alginate coating increased the size of optimized chitosan nanoparticles from around 213 nm to about 335 nm as measured by dynamic light scattering in zeta sizer and further confirmed by SEM analysis. The performance of optimized enoxaparin loaded Alg-CS-NPs was evaluated by in vitro drug release studies, in vitro permeation study across intestinal epithelium, in vivo venous thrombosis model, particulate uptake by intestinal epithelium using fluorescence microscopy and pharmacokinetic studies in rats. Coating of alginate over the CS-NPs improved the release profile of enoxaparin from the nanoparticles for successful oral delivery. In vitro permeation studies elucidated that more than 75% enoxaparin permeated across the intestinal epithelium with Alg-CS-NPs. The Alg-CS-NPs significantly increased (p < 0.05) the oral bioavailability of enoxaparin in comparison to plain enoxaparin solution as revealed by threefold increase in AUC of plasma drug concentration time curve and around 60% reduction in thrombus formation in rat venous thrombosis model. The core shell Alg-CS-NPs showed promising potential for oral delivery and significantly enhanced the in vivo oral absorption of enoxaparin.     

Polyglutamic acid-based nanocomposites as efficient non-viral gene carriers in vitro and in vivo

A series of polyethylenimine (PEI) and γ-polyglutamic acid (PGA) nanocomposites (PPGA) was prepared and evaluated in terms of their cell viability and transfection efficiency in vitro and in vivo. On complexion with pDNA, the positively charged PPGA/DNA nanocomposites resulted in a higher level of in vitro reporter gene transfection (2.7-7.9-fold) as compared to native PEI, and selected commercial reagents and >95% cell viability in HEK293, HeLa and HepG2 cell lines. Further, PPGA-5 nanocomposite (the best working system in terms of transfection efficiency among the series) was found to efficiently transfect primary mouse keratinocytes up to 22% above the control level. PPGA-5, when tested for in vivo cytotoxicity in Drosophila, did not induce any stress in the exposed larvae in comparison with control. In vivo gene expression using PPGA-5 showed the highest transfection efficiency in spleen of mouse closely followed by heart tissues after intravenous injection through tail vein. Besides, these nanocomposites also delivered siRNA efficiently into mammalian cells, resulting in ∼80% suppression of EGFP expression. These results together demonstrated the potential of the projected nanocomposites for in vivo gene delivery.     

Disparate in vivo and in vitro immunomodulatory activities of rhodamine B

At nontoxic concentrations (1–10 μg/ml) rhodamine B (N-[9-(2-carboxyphenyl)-6-(diethylamino)-3 H-xanthen-3-ylidene]-N-ethylethanaminium chloride; D & C Red No. 19; CAS no. 81-88-9), a low-molecular-weight dye, suppressed the primary in vitro plaque-forming-cell response of BDF₁ mouse spleen cells both to the thymus-dependent antigen, sheep red blood cells and to the thymus-independent antigen, E. coli 0127:B8 lipopolysaccharide. Suppression was effective when the D & C Red No. 19 was added at any time up to 48 hr of culture. Rhodamine B at concentrations from 1 to 10 μg/ml significantly suppressed mitogen-induced proliferation of both B- and T-lymphocytes in vitro. BDF₁ mice exposed to 50 and 100 ppm dye in their drinking water for 14 days prior to splenectomy gave a depressed in vitro plaque-forming-cell response to sheep red blood cells. In contrast, a significant enhancement of antibody response resulted when mice were exposed to the dye and sheep-red-blood-cell antigen was administered in vivo. Mitogen-induced B- and T-lymphocyte proliferation was also enhanced in mice exposed to the dye for 14 days.     

Cytotoxicity and apoptotic signalling cascade induced by chelidonine-loaded PLGA nanoparticles in HepG2 cells in vitro and bioavailability of nano-chelidonine in mice in vivo

Poor oral bioavailability of chelidonine, a bio-active ingredient of Chelidonium majus, showing anti-cancer potentials against cancer cells with multidrug resistance, makes its optimal use rather limited. To address this problem, we encapsulated chelidonine in biodegradable poly(lactide-co-glycolide) (PLGA) polymers and evaluated nano-chelidonine's (NCs) anti-cancer efficacy vis-à-vis free chelidonine (FC) against HepG2 cells and also evaluated its bioavailability in mice. Physicochemical characteristics indicated that stable spherical NC were formed in nanometer size range (123 ± 1.15 nm) with good yield (86.34 ± 1.91%), better encapsulation efficiency (82.6 ± 0.574%), negative surface charge (−19.6 ± 2.48 mV) and ability of prolonged and sustained release of chelidonine. Fourier transform infrared analysis revealed that NC resembled similar peaks as that of FC suggesting effective encapsulation in PLGA. NC exhibited rapid cellular uptake and stronger apoptotic effect (∼46.6% reduced IC₅₀ value) than FC, blocking HepG2 cells at G2/M phase. p53, cyclin-D1, Bax, Bcl-2, cytochrome c, Apaf-1, caspase-9 and caspase-3 expressions also corroborated well to suggest greater anticancer potentials of NC. Our in vivo studies demonstrated NC to be more bio-available than FC and showed a better tissue distribution profile without inducing any toxicity (100 mg/kg bw) in mice. Unlike FC, NC could permeate into brain tissue, indicating thereby NC's better potentials for use in therapeutic oncology.     

Improving solubility and chemical stability of natural compounds for medicinal use by incorporation into liposomes

Natural bioactive compounds have been studied for a long time for their chemopreventive and therapeutic potential in several chronic inflammatory diseases, including cancer. However, their physicochemical properties generally result in poor chemical stability and lack of in vivo bioavailability. Very few human clinical trials have addressed absorption, distribution, metabolism, and excretion of these compounds in relation to efficacy. This limits the use of these valuable natural compounds in the clinic.In this study, we examined caffeic acid (derivatives), carvacrol (derivatives), thymol, pterostilbene (derivatives), and N-(3-oxo-dodecanoyl)-l-homoserine lactone. These are natural compounds with strong anti-inflammatory properties derived from plants and bacteria. However, these compounds have poor water solubility or are chemically unstable. To overcome these limitations we have prepared liposomal formulations. Our results show that lipophilic 3-oxo-C₁₂-homoserine lactone and stilbene derivatives can be loaded into liposomal lipid bilayer with efficiencies of 50-70%. Thereby, the liposomes solubilize these compounds, allowing intravenous administration without use of solvents. When compounds could not be loaded into the lipid bilayer (carvacrol and thymol) or are rapidly extracted from the liposomes in the presence of serum albumin (3-oxo-C₁₂-homoserine lactone and pterostilbene derivatives), derivatization of the compound into a water-soluble prodrug was shown to improve loading efficiency and encapsulation stability. The phosphate forms of carvacrol and pterostilbene were loaded into the aqueous interior of the liposomes and encapsulation was unaffected by the presence of serum albumin. Chemical instability of resveratrol was improved by liposome-encapsulation, preventing inactivating cis-trans isomerization. For caffeic acid, liposomal encapsulation did not prevent oxidation into a variety of products. Still, by derivatization into a phenyl ester, the compound could be stably encapsulated without chemical degradation.Despite the instability of liposome-association of 3-oxo-C₁₂-homoserine lactone and resveratrol, intravenous administration of these compounds inhibited tumor growth for approximately 70% in a murine tumor model, showing that simple solubilization can have important therapeutic benefits.     

Development of Lecithin/Chitosan Nanoparticles for Promoting Topical Delivery of Propranolol Hydrochloride: Design,Optimization and In-Vivo Evaluation

Propranolol (PPL) administered orally is considered as the first line drug for the treatment of infantile hemangioma, however several systemic adverse effects limit its use. For this reason, our work tackles the development and evaluation of PPL loaded chitosan nanoparticles (NPs), as an effective alternative for the treatment of infantile hemangioma. PPL -NPs were prepared using the double emulsion technique and the influence of the formulation variables on drug entrapment efficiency (EE), particle size (PS), percent released after 24 h (%R_24h) and zeta potential (ZP) were optimized using full factorial design. Two systems, namely F3 and F28 showing highest E.E., ZP and %R_24h with lowest PS, were fully characterized for DSC and TEM and incorporated into hydrogel with adequate viscosity. After ensuring safety for the selected nanoparticle, the hydrogel containing the optimized system was applied topically to rats. The in-vivo skin deposition in rats showed an accumulation of propranolol from the lecithin/chitosan nanocarrier by 1.56–1.91-fold when compared to the drug solution. The obtained result was further supported by the confocal laser scanning microscopy which showed fluorescence across the skin. PPL-HCL-loaded lecithin/chitosan nanoparticles could be considered as a potential candidate for treating infantile hemangiomas (IH) by maintaining therapeutic concentration topically while minimizing systemic side effects.     

Cell membrane damage and protein interaction induced by copper containing nanoparticles—Importance of the metal release process

Cu-containing nanoparticles are used in various applications in order to e.g. achieve antimicrobial activities and to increase the conductivity of fluids and polymers. Several studies have reported on toxic effects of such particles but the mechanisms are not completely clear. The aim of this study was to investigate the interactions between cell membranes and well-characterized nanoparticles of CuO, Cu metal, a binary Cu-Zn alloy and micron-sized Cu metal particles. This was conducted via in vitro investigations of the effects of the nanoparticles on (i) cell membrane damage on lung epithelial cells (A549), (ii) membrane rupture of red blood cells (hemolysis), complemented by (iii) nanoparticle interaction studies with a model lipid membrane using quartz crystal microbalance with dissipation monitoring (QCM-D). The results revealed that nanoparticles of the Cu metal and the Cu-Zn alloy were both highly membrane damaging and caused a rapid (within 1 h) increase in membrane damage at a particle mass dose of 20 μg/mL, whereas the CuO nanoparticles and the micron-sized Cu metal particles showed no such effect. At similar nanoparticle surface area doses, the nano and micron-sized Cu particles showed more similar effects. The commonly used LDH (lactate dehydrogenase) assay for analysis of membrane damage was found impossible to use due to nanoparticle-assay interactions. None of the particles induced any hemolytic effects on red blood cells when investigated up to high particle concentrations (1 mg/mL). However, both Cu and Cu-Zn nanoparticles caused hemoglobin aggregation/precipitation, a process that would conceal a possible hemolytic effect. Studies on interactions between the nanoparticles and a model membrane using QCM-D indicated a small difference between the investigated particles. Results of this study suggest that the observed membrane damage is caused by the metal release process at the cell membrane surface and highlight differences in reactivity between metallic nanoparticles of Cu and Cu-Zn and nanoparticles of CuO.     

Characteristics of tolerance in the guinea pig ileum produced by chronic in vivo exposure to opioid versus cannabinoid agonists

Few studies have compared the nature of tolerance that develops following chronic opioid treatment with that which develops after chronic cannabinoid exposure in the same tissue and species. The degree and character of tolerance induced by 7 twice daily injections of morphine or 5 daily injections of the cannabinoid receptor agonist, WIN-55,212-2, was examined by comparing the ability of DAMGO, 2-chloroadenosine (CADO) and WIN-55,212-2 to inhibit neurogenic contractions of the longitudinal muscle/myenteric plexus preparation (LM/MP) and the ability of nicotine to elicit contractions in the LM/MP. Chronic morphine treatment resulted in subsensitivity to all inhibitory agonists (rightward shift in IC₅₀ values of 4-5-fold) and an increased responsiveness to the excitatory effect of nicotine while chronic WIN-55,212-2 exposure resulted in subsensitivity only to WIN-55,212-2 and a reduction in maximum response to both WIN-55,212-2 and DAMGO but no change in responsiveness to CADO. Chronic WIN-55,212-2 treatment significantly reduced CB₁ but not MOR receptor protein abundance while chronic morphine treatment did not change either. Assessment of the distribution of MOR and CB₁ receptors in myenteric neurons revealed distinct individual receptor expression as well as co-localization which was unaffected by either cannabinoid or opioid treatment. Thus, in contrast to the heterologous tolerance that develops after opioid treatment, tolerance in the LM/MP following chronic in vivo WIN-55,212-2 exposure appears to be homologous in character and is accompanied by a selective decrease in CB₁ receptor protein abundance. The data suggest that the cellular basis of tolerance differs between the two systems.     

Improving the ex vivo stability of drug ester compounds in rat and dog serum: Inhibition of the specific esterases and implications on their identity

In drug development, it has been noticed that some drug compounds, especially esters, are unstable in serum samples ex vivo. This can lead to a substantial underestimation of the actual drug concentration.     

Microbial conversion and anticandidal effects of bioconverted product of cabbage (Brassica oleracea) by Pectobacterium carotovorum pv. carotovorum 21

This study was undertaken to examine the anticandidal effects of microbially bioconverted product of cabbage, obtained from the microbial conversion of cabbage (Brassica oleracea var. capitata) by a bacterial strain Pectobacterium carotovorum pv. carotovorum 21 (Pcc 21) against various isolates of Candida species including a clinical isolate. The bioconverted product (10 μl, corresponding to 500 μg/disc) displayed potential anticandidal effect against Candida albicans KACC 30062, Candida geochares KACC 30061, Candida albicans KACC 30003, Candida saitoana KACC 41238 and Candida glabrata P00368 (clinical isolate) as a diameter of zones of inhibition, found in the range of 14 ± 0.9 to 19 ± 1.1 mm. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of bioconverted product against the tested isolates were found in the range of 62.5–250 and 125–250 μg/ml, respectively. Also the bioconverted product had remarkable anticandidal effect on the viable counts of the tested Candida isolates. Further, scanning electron microscopic study revealed potential detrimental effect of bioconverted product on the morphology of C. albicans KACC 30062 at MIC concentration. All these findings together indicate that bioconverted product of cabbage has potential therapeutic value of medicinal significance to control Candida species including clinical isolates.     

The influence of chitosan content in cationic chitosan/PLGA nanoparticles on the delivery efficiency of antisense 2′-O-methyl-RNA directed against telomerase in lung cancer cells

Tailorable cationic chitosan/PLGA nanoparticles (CPNP) were used for the delivery of an antisense 2′-O-methyl-RNA (2OMR) directed against RNA template of human telomerase. Here, we describe the influence of the chitosan content on binding efficiency, complex stability, uptake in different human lung cell types and finally demonstrate the efficacy of this nanoplex system.CPNPs were prepared by the emulsion-solvent evaporation method using different amounts of chitosan and purified by preparative size exclusion chromatography. The characterization by photon correlation spectroscopy and zeta potential measurements showed a small increase in size and an increase of zeta potential with increasing amounts of chitosan. Binding efficiency and complex stability with 2OMR was high in water and correlated well with the chitosan content of particles but was weak in physiologically relevant media (PBS and RPMI cell culture medium). However, flow cytometry analysis showed that the uptake of 2OMR into A549 lung cancer cells was considerably higher in combination with nanoparticles and dependent on the amount of chitosan when compared to 2OMR alone. Confocal laser scanning microscopy revealed that the uptake into A549 cells is mediated via complexes of 2OMR and chitosan/PLGA nanoparticles despite the weak binding in cell culture medium. The nanoparticles were well tolerated and efficient in inhibiting telomerase activity.     

Nanoparticles for skin penetration enhancement--a comparison of a dendritic core-multishell-nanotransporter and solid lipid nanoparticles

Nanosized particles are of growing interest for topical treatment of skin diseases to increase skin penetration of drugs and to reduce side effects. Effects of the particle structure and size were studied loading nile red to dendritic core-multishell (CMS) nanotransporters (20-30 nm) and solid lipid nanoparticles (SLNs, 150-170 nm). Interaction properties of CMS nanotransporters with the dye molecules--attachment to the carrier surface or incorporation in the carrier matrix--were studied by UV/Vis and parelectric spectroscopy. Pig skin penetration was studied ex vivo using a cream for reference. Interactions of SLN and skin were followed by scanning electron microscopy, internalisation of the particles by viable keratinocytes by laser scanning microscopy. Incorporating nile red into a stable dendritic nanoparticle matrix, dye amounts increased eightfold in the stratum corneum and 13-fold in the epidermis compared to the cream. Despite SLN degradation at the stratum corneum surface, SLN enhanced skin penetration less efficiently (3.8- and 6.3-fold). Viable human keratinocytes showed an internalisation of both nanocarriers. In conclusion, CMS nanotransporters can favour the penetration of a model dye into the skin even more than SLN which may reflect size effects.     

Prevention and recovery of (μ-diethylentriamino)-chloro-palladium(II)-chloride induced inhibition of Na/K-ATPase by SH containing ligands – l-cysteine and glutathione

The effect of (mu(3)-diethylentriamino)-chloro-palladium(II)-chloride ([PdCl(dien)]Cl) on the activity of Na/K-ATPase from porcine cerebral cortex was studied in vitro, in the absence and presence of -SH containing ligands L-cysteine and glutathione (GSH). The aim of the study was to elucidate the mechanism of [PdCl(dien)](+) induced inhibition of the enzyme activity and to examine the ability of thiols to prevent and recover the inhibition. The coordinative interaction between [PdCl(dien)](+) and enzyme was verified by UV and (1)H NMR spectra. The semblance in the changes in absorption spectra of [PdCl(dien)](+) in the presence of Na/K-ATPase and thiols (L-cysteine and GSH) suggested that the complex ion interacts with enzymatic sulfhydryl groups. [PdCl(dien)](+) inhibited the enzyme activity in a dose-dependent manner. The Hill analysis of the inhibition curve yielded the half-maximum inhibitory activity value, IC(50)=1.21 x 10(-4)M, and Hill coefficient, n=0.7, suggesting the negative cooperation for binding of [PdCl(dien)](+) to the enzyme. Dependence of the initial reaction rate on the concentration of MgATP(2-) exhibited typical Michelis-Menten kinetics in the absence and presence of the inhibitor. Kinetic analysis showed that [PdCl(dien)](+) inhibited Na/K-ATPase by reducing the maximum reaction rate (V(max)), rather than changing the affinity to the substrate (K(m)). Kinetic parameters derived using Lineweaver-Burk transformation of experimental data indicated the non-competitive nature of Na/K-ATPase inhibition. The inhibitory constant, K(i)=1.05 x 10(-4)M, was determined from secondary replot of Lineweaver-Burk graph, and correlated with stability constants of [Pd(dien)(thiol)] complexes. 1 x 10(-3)M L-cysteine or GSH prevented the enzyme inhibition induced by Pd(II) complex cation when present below 1 x 10(-4)M. The both thiols completely reversed the inhibited activity in the concentration dependent manner, due to the complex formation with [PdCl(dien)](+).     

Cytotoxicity and genotoxicity of superporous hydrogel containing interpenetrating polymer networks

The superporous hydrogel containing poly(acrylic acid-co-acrylamide)/O-carboxymethyl chitosan (O-CMC) interpenetrating polymer networks (SPH-IPN) that had been developed as an oral delivery vehicle for protein drugs was subject to cytotoxicity and genotoxicity testing, thus evaluating its biological safety in use. In a battery of cytotoxicity assays on RBL-2H3 and Caco-2 cells, the SPH-IPN caused minimal damage towards cell viability, lysosomal activity, and metabolic activity following both direct and indirect treatment. The SPH-IPN did not induce cell apoptosis or DNA breakage in the above cell lines; it did not increase micronucleus (MN) incidence in mouse bone marrow, either. Therefore, the SPH-IPN was preliminarily considered to be biocompatible and might be a safe carrier for protein drugs. In addition, using the HPLC method, residual acrylic acid, acrylamide, and glutaraldehyde in the SPH-IPN were quantified to be 1.4, 2.0, and below 0.2 ppm, respectively. Lack of these low molecular monomers and crosslinker that were mainly responsible for the toxicity provided evidence for the good biocompatibility of the SPH-IPN.     

Development of Octreotide-Loaded Chitosan and Heparin Nanoparticles: Evaluation of Surface Modification Effect on Physicochemical Properties and Macrophage Uptake

Octreotide (OCT) is a therapeutic peptide which is administered for the treatment of acromegaly. The purpose of this study was to design a new polyethylene glycol (PEG)–conjugated nanoparticle (PEG-NP) to overcome the short half-life and poor stability of OCT. The developed PEG-NPs were compared with non-PEGylated NPs with respect to their size, morphological characteristics, loading efficiency, release profile, and macrophage uptake. The OCT-loaded NPs and PEG-NPs were prepared by ionic complexion of chitosan (Cs) with either heparin (Hp) or PEGylated heparin (PEG-Hp). The chemical structure of PEG-Hp was confirmed by IR and proton nuclear magnetic resonance. Morphological analyses by scanning electron microscopy showed that NPs and PEG-NPs have a uniform shape. Dynamic laser scattering measurements indicated that hydrodynamic diameter of NPs and PEG-NPs were 222.5 ± 10.0 nm and 334.9 ± 6.7 nm, respectively. NPs and PEG-NPs had a positive zeta potential of about 32.5 ± 1.1 mv and 20.6 ± 2.4 mv, respectively. Entrapment efficiency was 61.4 ± 1.0% and 55.7 ± 2.4% for NPs and PEG-NPs, respectively. Compared with the NPs, the PEG-NPs exhibited a slower release profile. Subsequently, fluorescein isothiocyanate–labeled chitosanCs was synthesized and used to evaluate the stealth characteristic of PEG-NPs. In vitro macrophage uptake of fluorescently labeled NPs was measured by flow cytometry.     

Reactive blue 2 inhibition of cyclic AMP-dependent differentiation of rat C6 glioma cells by purinergic receptor-independent inactivation of phosphatidylinositol 3-kinase

Cyclic AMP-dependent differentiation of rat C6 glioma cells into an astrocyte type II is characterized by inhibition of cell growth and induction of glial fibrillary acidic protein (GFAP) synthesis. Activation of the P2Y(12) receptor with 2-methylthioadenosine-5'-diphosphate inhibited beta-adrenergic receptor-induced differentiation. The selective P2Y(12) receptor antagonist N(6)-(2-methylthioethyl)-2-(3,3,3-trifluoropropylthio)-beta,gamma-dichloromethylene ATP abolished the receptor-mediated effect on differentiation. In contrast non-selective antagonists of P2Y receptors did not revert the inhibiting effect of the P2Y(12) receptor on differentiation. Reactive blue 2 (RB2), a potent P2Y(12) receptor antagonist, completely inhibited the synthesis of GFAP, while the P2Y receptor antagonists suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid were less efficient. However, although P2Y receptor antagonists inhibited GFAP synthesis to a different extent they were unable to relieve the growth inhibition that accompanied induction of differentiation, whereas stimulation of the P2Y(12) receptor with 2-methylthioadenosine-5'-diphosphate inhibited GFAP expression and restored cell proliferation. Assay of the activity of phosphatidylinositol 3-kinase (PI 3-K), an enzyme required for GFAP expression [J. Neurochem. 76 (2001) 610], showed that RB2 inhibited this enzyme after cellular uptake, while suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid inhibited PI 3-K to a lesser extent. The intracellular concentration of RB2 increased in time and attained the ic(50) for PI 3-K inhibition (4microM) after 40-min incubation with 50microM RB2. In conclusion, cAMP-induced differentiation in C6 cells is inhibited by activation of the P2Y(12) receptor. In addition, synthesis of GFAP is also inhibited by cellular uptake of non-selective nucleotide receptor antagonists that inhibit PI 3-K, a kinase required for the cAMP-dependent induction of differentiation.