Co-delivery of superfine nano-silver and solubilized sulfadiazine for enhanced antibacterial functions.

For the effective treatment of bacterial infection, it is essential to find a new strategy to deliver antibacterial agents. In the present study, the co-delivery of superfine nano-silver with solubilized sulfadiazine (SD) using cyclodextrin metal-organic frameworks (CD-MOF) as a carrier exhibited superior antibacterial efficacy to insoluble silver sulfadiazine. The abundant hydroxyl moieties in CD-MOF were utilized to reduce Ag precursor into silver nanoparticles (Ag NPs) of 4-5 nm and immobilized within the nano-sized cavities. Microporous CD-MOF facilitated the inclusion of SD molecules in the hydrophobic cavities of γ-cyclodextrin (γ-CD) molecular pairs. The hydrophilic CD-MOF can easily dissolve within exudates at the wound region to release the drug. This approach improved the aqueous solubility of SD by 50 folds which subsequently enhanced SD release and their antibacterial activity. The CD framework also prevented the aggregation of nano-silver particles, stabilizing the particle size and enhancing the curative effects. Hence, the incorporation of superfine nano-silver with solubilized SD using CD-MOF could be an alternate strategy to co-deliver silver and SD with higher efficacy.

Multi-dimensional visualization for the morphology of lubricant stearic acid particles and their distribution in tablets.

The shapes of particles and their distribution in tablets, controlled by pretreatment and tableting process, determine the pharmaceutical performance of excipient like lubricant. This study aims to provide deeper insights to the relationship of the morphology and spatial distribution of stearic acid (SA) with the lubrication efficiency, as well as the resulting tablet property. Unmodified SA particles as flat sheet-like particles were firstly reprocessed by emulsification in hot water to obtain the reprocessed SA particles with spherical morphology. The three-dimensional (3D) information of SA particles in tablets was detected by a quantitative and non-invasive 3D structure elucidation technique, namely, synchrotron radiation X-ray micro-computed tomography (SR-µCT). SA particles in glipizide tablets prepared by using unmodified SA (GUT), reprocessed SA (GRT), as well as reference listed drug (RLD) of glipizide tablets were analyzed by SR-µCT. The results showed that the reprocessed SA with better flowability contributed to similarity of breaking forces between that of GRT and RLD. SA particles in GRT were very similar to those in RLD with uniform morphology and particle size, while SA particles in GUT were not evenly distributed. These findings not only demonstrated the feasibility of SR-µCT as a new method in revealing the morphology and spatial distribution of excipient in drug delivery system, but also deepened insights of solid dosage form design into a new scale by powder engineering.

Folic acid and its metabolite codetermination for pharmacokinetics with circadian rhythms and evaluation of oral bioavailability.

OBJECTIVES: Pharmacokinetics of vitamins is still a challenge. In this study, folic acid (FA) was used as a model drug and aimed at investigating a reliable method for its detailed pharmacokinetic evaluations. METHODS: An high-performance liquid chromatography-tandem mass spectrometry method was developed and performed to determinate the FA and 5-methyltetrahydrofolic acid (5-methylTHF) simultaneously, which was applied to characterize the circadian rhythms as well as the pharmacokinetics of different preparations. KEY FINDINGS: The plasma concentration of 5-methylTHF in fasted state was twofold higher than that in fed state. The circadian rhythms were studied before the pharmacokinetics and revealed that free FA was almost undetected in blank plasma, while 5-methylTHF had a slight decrement at 12:00. Hence, the pharmacokinetics of FA was conducted and showed that the administration of FA solution resulted in enhancing bioavailability of 5-methylTHF comparing with FA raw material suspension, whereas the free FA level in plasma was similar. The mechanism could be that FA was rapidly metabolized to 5-methylTHF in intestinal epithelial cell after absorption, which revealed that intestinal metabolism would affect its bioavailability. CONCLUSION: A suitable method was established considering the baseline level, circadian rhythms and intestinal metabolism to investigate the pharmacokinetics of FA for guiding the further research of vitamins.

Ultrafine Silver Nanoparticles Embedded in Cyclodextrin Metal-Organic Frameworks with GRGDS Functionalization to Promote Antibacterial and Wound Healing Application.

The challenge of bacterial infection increases the risk of mortality and morbidity in acute and chronic wound healing. Silver nanoparticles (Ag NPs) are a promising new version of conventional antibacterial nanosystem to fight against the bacterial resistance in concern of the drug discovery void. However, there are several challenges in controlling the size and colloidal stability of Ag NPs, which readily aggregate or coalesce in both solid and aqueous state. In this study, a template-guided synthesis of ultrafine Ag NPs of around 2 nm using water-soluble and biocompatible γ-cyclodextrin metal-organic frameworks (CD-MOFs) is reported. The CD-MOF based synthetic strategy integrates AgNO3 reduction and Ag NPs immobilization in one pot achieving dual functions of reduced particle size and enhanced stability. Meanwhile, the synthesized Ag NPs are easily dispersible in aqueous media and exhibit effective bacterial inhibition. The surface modification of cross-linked CD-MOF particles with GRGDS peptide boosts the hemostatic effect that further enhances wound healing in synergy with the antibacterial effect. Hence, the strategy of ultrafine Ag NPs synthesis and immobilization in CD-MOFs together with GRGDS modification holds promising potential for the rational design of effective wound healing devices.

Optimization of taste-masking on ibuprofen microspheres with selected structure features.

The microsphere was a primary particulate system for taste-masking with unique structural features defined by production process. In this article, ibuprofen lipid microspheres of octadecanol and glycerin monostearate were prepared to mask the undesirable taste of ibuprofen via three kinds of spray congealing processes, namely, air-cooling, water-cooling and citric acid solution-cooling. The stereoscopic and internal structures of ibuprofen microspheres were quantitatively analyzed by synchrotron radiation X-ray micro-computed tomography (SR-µCT) to establish the relationship between the preparation process and microsphere architectures. It was found that the microstructure and morphology of the microspheres were significantly influenced by preparation processes as the primary factors to determine the release profiles and taste-masking effects. The sphericity of ibuprofen microspheres congealed in citric acid solution was higher than that of other two and its morphology was more regular than that being congealed in air or distilled water, and the contact angles between congealing media and melted ibuprofen in octadecanol and glycerin monostearate well demonstrated the structure differences among microspheres of three processes which controlled the release characteristics of the microspheres. The structure parameters like porosity, sphericity, and radius ratio from quantitative analysis were correlated well with drug release behaviors. The results demonstrated that the exterior morphology and internal structure of microspheres had considerable influences on the drug release behaviors as well as taste-masking effects.

Identification of beagle food taking patterns and protocol for food effects evaluation on bioavailability.

Food is a known primary role to the exposure of the drugs orally administered. Since each animal may have unique food taking pattern and it is difficult to manipulate the food taking to animals, there lacks rationalized protocol for the food effects in pre-clinic study. The objective of this study was to identify the beagle food taking patterns and demonstrate their effects on bioavailability in valsartan. Herein, four types of food taking patterns of beagle were identified via inter-day and intra-day analysis, and named as Persisting, Pulsing, Postponing, Pushing ("4P Modes"), respectively, which were also validated by principal component analysis (PCA). Interestingly, food intake resulted in a reduced area under the concentration-time curve (AUC0-12h), maximum concentration (Cmax) and absorption rate, whilst the reduction varied in "4P Modes" of food taking. General considerations in the design of experiment for food effect to the bioavailability in beagles have been established as: to recognize the food taking patterns in each animal, to confirm the inter-day stability of the food taking behaviors, to trace the food taking patterns in parallel with plasma sampling. In conclusion, the right animals with proper food taking patterns should be assessed and selected for pre-clinic bioavailability evaluations.

Molecular Mechanism of Loading Sulfur Hexafluoride in γ-Cyclodextrin Metal-Organic Framework.

γ-Cyclodextrin metal-organic framework (γ-CD-MOF) is a new type of highly porous carrier for potential loading of therapeutic or diagnostic gas like sulfur hexafluoride (SF6). Here, loading of SF6 into γ-CD-MOF was investigated for its mechanism by molecular simulation and quantitative determination of SF6 using quantitative nuclear magnetic resonance (qNMR). For the SF6 loading, γ-CD-MOF was first degassed to remove the air without thermal decomposition or loss of framework crystallinity, then placed in the copper tube, and sealed to adsorb SF6 under 1.2 MPa and 25 °C for 12 h. The qNMR was employed for the determination of SF6 loaded in γ-CD-MOF using Span 80 as suspending agent and trifluoroacetic acid as internal standard. Then, the thermodynamic parameters had been estimated. Finally, molecular modeling combining with 19F NMR spectra was conducted to reveal the status of SF6 molecules in γ-CD-MOF. The results demonstrated that the content of SF6 loaded in γ-CD-MOF was 2.67 ± 0.46 wt %. After exposing to the environment of free SF6 at 0.1 MPa for 10 days, the relative content was 74.7%. It was confirmed that SF6 preferred to stay in the cavity of γ-CD-MOF cubes rather than in the γ-CD molecular pairs, which was a nonchemical adsorptive process. In conclusion, this research has established qNMR method and molecular simulation to demonstrate SF6 molecules in γ-CD-MOF and its loading mechanism.

Biofunctionalization of ß-cyclodextrin nanosponges using cholesterol.

Cyclodextrins nanosponges (CD-NSPs) are highly microporous crosslinked polymers with potential applications in the delivery of small and macro-molecular therapeutic agents. Despite the potent host-guest inclusion property, their inherent lack of cellular binding ability has limited applications in drug delivery. Herein, we functionalized the surface of ß-cyclodextrin nanosponge (ß-CD-NSP) with cholesterol, which is endogenous physiological molecules, widely distributed in all cells, and responsible for cell interactions and protein binding. The surface grafting of synthesized ß-CD-NSP was confirmed with spectroscopic, microscopic, thermogravimetric, and chromatographic techniques. Moreover, ß-CD-NSP was found to be safe in cytotoxicity assay. Doxorubicin (Dox) was selected as a model drug for drug adsorption study of cholesterol hydrogen succinate (CHS) grafted ß-CD-NSP. The cellular uptake of NSP was found to be enhanced after CHS modification confirmed by confocal laser scanning microscopy (CLSM). Thus, proposed CHS modified ß-CD-NSP system could be used as a site-specific drug delivery carrier.

Influence of Nutritional Status on the Absorption of Polyphyllin I, an Anticancer Candidate from Paris polyphylla in Rats.

BACKGROUND AND OBJECTIVES: Protein-calorie malnutrition (PCM) is one of the most suffered complications in cancer patients. Polyphyllin I (PPI), a saponin isolated from rhizome of Paris polyphylla, is a potential candidate in cancer therapy. In this study, the influence of nutritional status on the absorption of PPI in rats was explored after oral administration. METHODS: PCM rats, namely mal-nourished (MN) rats, were induced from well-nourished (WN) rats by caloric restriction protocol. Intestinal absorption of PPI in WN and MN rats was evaluated by pharmacokinetic and intestinal perfusion methods. The potential mechanisms between two groups were investigated on the basis of intestinal permeability, intestinal efflux and PPI's depletions in vivo. The intestinal permeability was analyzed by determining the concentration of paracellular marker transport in serum and the expression of junction proteins in intestine. The intestinal efflux was evaluated through comparing the protein level of P-glycoprotein (P-gp) in intestine, and the depletions of PPI and/or generation of its metabolites in liver and intestines were analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS) method. RESULTS: Compared to WN rats, the oral systemic exposure of PPI was significantly increased in MN rats, evidenced by significant enhancement of maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC0-60h) by more than 2.51- and 3.71-folds as well as terminal elimination half-life (t1/2) prolonged from to 7.3 to 14.1 h. Further studies revealed that the potential mechanism might be associated with combined contribution of improved intestinal absorption and depressed deglycosylation of PPI in MN rats. Furthermore, enhanced intestinal absorption of PPI was benefited from increased intestinal permeability and decreased intestinal efflux in MN rats. Meanwhile, the former manifested as increased transport of paracellular marker and decreased junction proteins levels, while the later evidenced by reduced P-gp expression. CONCLUSIONS: The oral exposure of PPI was enhanced in MN rats, which suggested that nutritional status alters the absorption of PPI, and thus the dosage of PPI should be modified during the treatment of cancer patient with PCM.

Metabolic profile and pharmacokinetics of polyphyllin I, an anticancer candidate, in rats by UPLC-QTOF-MS/MS and LC-TQ-MS/MS.

Polyphyllin I (PPI), a natural steroidal saponin originating from rihzome of Paris polyphylla, is a potential anticancer candidate. Previous pharmacokinetics study showed that the oral bioavailability of PPI was very low, which suggested that certain amount of PPI might be metabolized in vivo. However, to date, information regarding the final metabolic fates of PPI is very limited. In this study, metabolites of PPI and their pharmacokinetics in rats were investigated using UPLC-QTOF-MS/MS and LC-TQ-MS/MS. A total of seven putative metabolites, including six phase I and one phase II metabolites, were detected and identified with three exact structures by comparison with authentic standards for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. The pharmacokinetics of prosapogenin A, trillin and diosgenin, three deglycosylation metabolites of PPI with definite anticancer effects, were further studied, which suggested that the metabolites underwent a prolonged absorption and slower elimination after intragastric administration of PPI at the dose of 500 mg/kg. This study provides valuable and new information on the metabolic fate of PPI, which will be helpful in further understanding its mechanism of action.

Study on the pharmacokinetics profiles of polyphyllin I and its bioavailability enhancement through co-administration with P-glycoprotein inhibitors by LC-MS/MS method.

Polyphyllin I (PPI), one of the steroidal saponins in Paris polyphylla, is a promising natural anticancer candidate. Although the anticancer activity of PPI has been well demonstrated, information regarding the pharmacokinetics and bioavailability is limited. In this study, a series of reliable and rapid liquid chromatography-tandem mass spectrometry methods were developed and successfully applied to determinate PPI in rat plasma, cell incubation media and cell homogenate. Then the pharmacokinetics of PPI in rats was studied and the result revealed that PPI was slowly eliminated with low oral bioavailability (about 0.62%) at a dose of 50 mg/kg, and when co-administrated with verapamil (VPL) and cyclosporine A (CYA), the oral bioavailability of PPI could increase from 0.62% to 3.52% and 3.79% respectively. In addition, in vitro studies showed that with the presence of VPL and CYA in Caco-2 cells, the efflux ratio of PPI decreased from 12.5 to 2.96 and 2.22, and the intracellular concentrations increased 5.8- and 5.0-fold respectively. These results demonstrated that PPI, with poor oral bioavailability, is greatly impeded by P-gp efflux, and inhibition of P-gp can enhance its bioavailability.

[Study on pharmacokinetics of asperosaponin VI and its active metabolite in rats].

To study the pharmacokinetics, excretion characteristics and plasma protein binding rate of asperosaponin VI (A-VI) and its active metabolite hederagenin (M1). A-VI and M1 concentrations in plasma, bile, urine and feces were determined by established LC-MS/MS to calculate the pharmacokinetic parameters. The plasma protein binding rate of A-VI was determined by equilibrium dialysis method. the double peaks was observed in the A-VI plasma concentration-time curve, after rats were orally administered with low, medium and high doses of A-VI (0.03, 0.09, 0.27 g x kg(-1)). The Cmax1 and Cmax2 of A-VI were (28.88 +/- 49.78) and (4.480 +/- 1.872) microg x L(-1), (35.19 +/- 23.53) and (22.11 +/- 16.15) microg x L(-1), (73.37 +/- 37.28) and (132.2 +/- 160.7) microg x L(-1), respectively. The AUC0-t, of A-VI were (43.21 +/- 37.32), (133.9 +/- 102.5) and (779.6 +/- 876.9) microg x h x L(-1), respectively. The t1/2 of A-VI were (3.3 +/- 0.8), (3.2 +/- 2.3) and (4.5 +/- 1.2) h, respectively. The Cmax of M1 were (16.03 +/- 9.336), (26.41 +/- 11.95) and (28.71 +/- 5.874) microg x L(-1), respectively. The AUC0-t, of M1 were (105.6 +/- 73.60), (260.0 +/-153.9) and (323.1 +/- 107.9) microg x h x L(-1), respectively. The t1/2 of M1 were (4.1 +/- 3.4), (4.4 +/- 2.3), (3.9 +/- 0.9) h, respectively. No significant gender difference was found in the in vivo pharmacokinetics of A-VI and M1. There was no accumulation of A-VI and M1 after multiple administrations of A-VI (0.09 g x kg(-1)). After oral administration of A-VI, the double peaks were also observed in biliary and urinary excretion rate-time curves for A-VI. M1 was detected in the feces samples at 6 h after oral administration. The average plasma protein binding rate of A-VI was 92. 9% in rats.

Simple LC-MS/MS methods for simultaneous determination of pitavastatin and its lactone metabolite in human plasma and urine involving a procedure for inhibiting the conversion of pitavastatin lactone to pitavastatin in plasma and its application to a pharmacokinetic study.

Sometimes, drugs and their metabolites in plasma may convert to each other. This phenomenon is called interconversion, which may result in the instability problem of the plasma samples. The instability problem caused by interconversion of the co-existing metabolites may often be ignored, since there is no drug metabolite in the quality control samples prepared for method validation. Pitavastatin lactone (Pi-LAC), a main metabolite of pitavastatin (Pi), is very unstable and easily converted to Pi in plasma. In this paper, simple and rapid LC-ESI-MS/MS methods were developed for the simultaneous determination of Pi and Pi-LAC in human plasma and urine. The sample stability was examined under different conditions. The interconversion of Pi and Pi-LAC was prevented by adding a pH 4.2 buffer solution to the freshly collected plasma samples. Detection was performed using an electrospray ionization (ESI) operating in positive ion multiple reaction monitoring mode by monitoring the ion transitions from m/z 422.2→290.3 (Pi), 404.2→290.3 (Pi-LAC) and m/z 611.3→423.2 (candesartan cilextetil, the internal standard), respectively. The calibration curve of Pi and Pi-LAC in both human plasma and urine showed good linearity over the concentration range of 0.1-200 ng/mL. The established methods were successfully applied to a pharmacokinetic study of pitavastatin calcium tablets in healthy Chinese volunteers after oral administration of 1, 2 and 4 mg single and multiple doses of pitavastatin calcium. The pharmacokinetic parameters of Pi and Pi-LAC in Chinese volunteers were given respectively. The urinary excretion profiles of Pi and Pi-LAC in Chinese volunteers were also presented. After receiving a single 4 mg oral dose of pitavastatin calcium, the average cumulative urinary excretion percentages of Pi and Pi-LAC in Chinese volunteers were (0.41 ± 0.16)% and (6.1 ± 5.0)%, respectively.

Determination of asperosaponin VI in dog plasma by high-performance liquid chromatography-tandem mass spectrometry and its application to a pilot pharmacokinetic study.

A sensitive and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the determination of asperosaponin VI in beagle dog plasma using glycyrrhizic acid as the internal standard (IS). Plasma samples were simply pretreated with methanol for deproteinization. Chromatographic separation was performed on a Hedera ODS-2 column using mobile phase of methanol-10 mm ammonium acetate buffer solution containing 0.05% acetic acid (71:29, v/v) at a flow rate of 0.38 mL/min. Asperosaponin VI and the IS were eluted at 2.8 and 1.9 min, respectively, ionized in negative ion mode, and then detected by multiple reaction monitoring. The detection used the transitions of the deprotonated molecules at m/z 927.5 → 603.4 for asperosaponin VI and m/z 821.4 → 645.4 for glycyrrhizic acid (IS). The assay was linear over the concentration range of 0.15-700 ng/mL and was successfully applied to a pilot pharmacokinetic study in beagle dogs.

Simultaneous determination of asperosaponin VI and its active metabolite hederagenin in rat plasma by liquid chromatography-tandem mass spectrometry with positive/negative ion-switching electrospray ionization and its application in pharmacokinetic study.

A new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method operated in the positive/negative electrospray ionization (ESI) switching mode has been developed and validated for the simultaneous determination of asperosaponin VI and its active metabolite hederagenin in rat plasma. After addition of internal standards diazepam (for asperosaponin VI) and glycyrrhetic acid (for hederagenin), the plasma sample was deproteinized with acetonitrile, and separated on a reversed phase C18 column with a mobile phase of methanol (solvent A)-0.05% glacial acetic acid containing 10 mM ammonium acetate and 30 µM sodium acetate (solvent B) using gradient elution. The detection of target compounds was done in multiple reaction monitoring (MRM) mode using a tandem mass spectrometry equipped with positive/negative ion-switching ESI source. At the first segment, the MRM detection was operated in the positive ESI mode using the transitions of m/z 951.5 ([M+Na](+))→347.1 for asperosaponin VI and m/z 285.1 ([M+H](+))→193.1 for diazepam for 4 min, then switched to the negative ESI mode using the transitions of m/z 471.3 ([M-H](-))→471.3 for hederagenin and m/z 469.4 ([M-H](-))→425.4 for glycyrrhetic acid, respectively. The sodiated molecular ion [M+Na](+) at m/z 951.5 was selected as the precursor ion for asperosaponin VI, since it provided better sensitivity compared to the deprotonated and protonated molecular ions. Sodium acetate was added to the mobile phase to make sure that abundant amount of the sodiated molecular ion of asperosaponin VI could be produced, and more stable and intensive mass response of the product ion could be obtained. For the detection of hederagenin, since all of the mass responses of the fragment ions were very weak, the deprotonated molecular ion [M-H](-)m/z 471.3 was employed as both the precursor ion and the product ion. But the collision energy was still used for the MRM, in order to eliminate the influences induced by the interference substances from the rat plasma. The validated method was successfully applied to study the pharmacokinetics of asperosaponin VI and its active metabolite hederagenin in rat plasma after oral administration of asperosaponin VI at a dose of 90 mg/kg.