Enhancing Stability and Mucoadhesive Properties of Chitosan Nanoparticles by Surface Modification with Sodium Alginate and Polyethylene Glycol for Potential Oral Mucosa Vaccine Delivery.

Background: The present study aimed to fabricate surface-modified chitosan nanoparticles with two mucoadhesive polymers (sodium alginate and polyethylene glycol) to optimize their protein encapsulation efficiency, improve their mucoadhesion properties, and increase their stability in biological fluids. Method: Ionotropic gelation was employed to formulate chitosan nanoparticles and surface modification was performed at five different concentrations (0.05, 0.1, 0.2, 0.3, 0.4% w/v) of sodium alginate (ALG) and polyethylene glycol (PEG), with ovalbumin (OVA) used as a model protein antigen. The functional characteristics were examined by dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM)/scanning transmission electron microscopy (STEM). Stability was examined in the presence of simulated gastric and intestinal fluids, while mucoadhesive properties were evaluated by in vitro mucin binding and ex vivo adhesion on pig oral mucosa tissue. The impact of the formulation and dissolution process on the OVA structure was investigated by sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) and circular dichroism (CD). Results: The nanoparticles showed a uniform spherical morphology with a maximum protein encapsulation efficiency of 81%, size after OVA loading of between 200 and 400 nm and zeta potential from 10 to 29 mV. An in vitro drug release study suggested successful nanoparticle surface modification by ALG and PEG, showing gastric fluid stability (4 h) and a 96 h sustained OVA release in intestinal fluid, with the nanoparticles maintaining their conformational stability (SDS-PAGE and CD analyses) after release in the intestinal fluid. An in vitro mucin binding study indicated a significant increase in mucin binding from 41 to 63% in ALG-modified nanoparticles and a 27-49% increase in PEG-modified nanoparticles. The ex vivo mucoadhesion showed that the powdered particles adhered to the pig oral mucosa. Conclusion: The ALG and PEG surface modification of chitosan nanoparticles improved the particle stability in both simulated gastric and intestinal fluids and improved the mucoadhesive properties, therefore constituting a potential nanocarrier platform for mucosal protein vaccine delivery.

Internal dose of vanadium in rats following repeated exposure to vanadyl sulfate and sodium orthovanadate via drinking water.

Vanadium is a ubiquitous environmental contaminant that exists in multiple oxidation states. Humans are exposed to vanadyl (V4+) and vanadate (V5+) from dietary supplements, food, and drinking water and hence there is a concern for adverse human health. The current investigation is aimed at identifying vanadium oxidation states in vitro and in vivo and internal concentrations following exposure of rats to vanadyl sulfate (V4+) or sodium metavanadate (V5+) via drinking water for 14 d. Investigations in simulated gastric and intestinal fluids showed that V4+ was stable in gastric fluid while V5+ was stable in intestinal fluid. Analysis of rodent plasma showed that the only vanadium present was V4+, regardless of the exposed compound suggesting conversion of V5+ to V4+ in vivo and/or instability of V5+ species in biological matrices. Plasma, blood, and liver concentrations of total vanadium, after normalizing for vanadium dose consumed, were higher in male and female rats following exposure to V5+ than to V4+. Following exposure to either V4+ or V5+, the total vanadium concentration in plasma was 2- to 3-fold higher than in blood suggesting plasma as a better matrix than blood for measuring vanadium in future work. Liver to blood ratios were 4-7 demonstrating significant tissue retention following exposure to both compounds. In conclusion, these data point to potential differences in absorption and disposition properties of V4+ and V5+ salts and may explain the higher sensitivity in rats following drinking water exposure to V5+ than V4+ and highlights the importance of internal dose determination in toxicology studies.

Effect of acid and in vitro digestion on conformation and IgE-binding capacity of major oyster allergen Cra g 1 (tropomyosin).

INTRODUCTION AND OBJECTIVES: The production and consumption of oysters is increasing annually because it can provide essential nutrients and benefit for human health, leading to frequent occurrence of severe allergic reactions observed in sensitized individuals. The aim of the present study was to investigate the effects of acid and protease treatment on the conformation and IgE-binding capacity of recombinant Crassostrea gigas tropomyosin (Cra g 1). RESULTS: Under acidic conditions, Cra g 1 did not undergo degradation, however, the changes obvious in the intensity of CD signal and ANS-binding fluorescence were observed, which was associated with a decrease in antibody reactivity. In simulated gastrointestinal fluid (SGF) and simulated intestinal fluid (SIF) digestion system, acid-treated Cra g 1 was relatively resistant to digestion, but the degradative patterns were very different. Moreover, owing to alterations of secondary structure and hydrophobic surface of the protein during digestive processing, antigenicity of acid-induced Cra g 1 reduced in SGF while it increased significantly in SIF. CONCLUSION: To our knowledge, this is the first study reporting that antigenicity of acid-treated oyster tropomyosin increased after SIF digestion. These results revealed that treatment with acid and pepsin, rather than trypsin, was an effective way of reducing IgE-binding capacity of tropomyosin from oyster.

Gelation and rheological characterization of Carbopol® in simulated gastrointestinal fluid of variable chemical properties.

Carbopol® is a hydrophilic polymer commonly used in the preparation of oral controlled-release matrix tablets. These matrices are subjected to dissolution testing to investigate the rate and mechanism of drug release. The rate of drug release from these matrices is influenced by the viscoelastic properties of the gel layer formed upon hydration and surrounded tablet core. This study evaluates the gelation behavior and rheological characterization of Carbopol® in dispersion media, of varied chemical properties, commonly used in dissolution testing. The rheological properties of Carbopol® polymer underwent gelation were determined using a controlled-stress rheometer. Carbopol® gelation was not found in simulated gastric fluid of low pH (1.2-5.0) and simulated intestinal fluid of pH (5.0-6.5) during fasted (Fa) and fed (Fe) conditions. However, in water and at high pH (6.8-7.8), gelation occurred in phosphate buffers of high buffering capacity (ß). Furthermore, no gelation was found in sodium chloride solutions of different ionic strengths (µ). These results highlight the importance of investigating the gelation behavior and rheological characterization of Carbopol® in dispersion media prior to dissolution testing. These preliminary studies can give an insight on the formation/absence of the gel layer around Carbopol® matrices which is responsible for controlling the release of drugs.

Topography of Simulated Intestinal Equilibrium Solubility.

Oral administration of a solid dosage form requires drug dissolution in the gastrointestinal tract before absorption. Solubility is a key factor controlling dissolution, and it is recognized that, within the intestinal tract, this is influenced by the luminal fluid pH, amphiphile content, and composition. Various simulated intestinal fluid recipes have been introduced to mimic this behavior and studied using a range of different experimental techniques. In this article, we have measured equilibrium solubility utilizing a novel four component mixture design (4CMD) with biorelevant amphiphiles (bile salt, phospholipid, oleate, and monoglyceride) within a matrix of three pH values (5, 6, and 7) and total amphiphile concentrations (11.7, 30.6, and 77.5 mM) to provide a topographical and statistical overview. Three poorly soluble drugs representing acidic (indomethacin), basic (carvedilol), and neutral (fenofibrate) categories have been studied. The macroscopic solubility behavior agrees with literature and exhibits an overall increasing solubility from low pH and total amphiphile concentration to high pH and total amphiphile concentration. Within the matrix, all three drugs display different topographies, which can be related to the statistical effect levels of the individual amphiphiles or amphiphile interactions on solubility. The study also identifies previously unreported three and four way factor interactions notably between bile salt, phospholipid, pH, and total amphiphile concentration. In addition, the results also reveal that solubility variability is linked to the number of amphiphiles and the respective ratios in the measurement fluid, with the minimum variation present in systems containing all four amphiphiles. The individual 4CMD experiments within the matrix can be linked to provide a possible intestinal solubility window for each drug that could be applied in PBPK modeling systems. Overall the approach provides a novel overview of intestinal solubility topography along with greater detail on the impact of the various factors studied; however, each matrix requires 351 individual solubility measurements. Further studies will be required to refine the experimental protocol in order the maximize information garnered while minimizing the number of measurements required.

Understanding the Role of Sodium Lauryl Sulfate on the Biorelevant Solubility of a Combination of Poorly Water-Soluble Drugs Using High Throughput Experimentation and Mechanistic Absorption Modeling.

This study investigates the influence of surfactant sodium lauryl sulfate (SLS) on the solubility of poorly-water soluble drug substances, model Compound X and Compound Y, used in a fixed dose combination oral solid dosage form. To determine the impact of SLS concentration on the solubility of compounds X and Y, we experimentally determined the critical micelle concentration (CMC) of SLS in water, simulated gastric fluid (SGF), and fed state simulated intestinal fluid (FeSSIF) in the presence of Compound X and Compound Y using UV/Visible spectrophotometry at 25°C. The aggregation of SLS was characterized by calculating the standard Gibbs free energy of micellization in all the media investigated.  To enhance the understanding of SLS aggregation, high throughput experiments and in-vivo mechanistic modelling were used to determine the effect of increasing levels of SLS on the solubility of compounds X and Y as both single agent and combination products to be formulated into a suitable oral solid dosage form. Micellar formation of SLS is a spontaneous process as shown by the negative values of the standard free energy of micellization. The CMC of SLS in the various media investigated in the presence of compounds X and Y decreases in the following order: water> FeSSIF> SGF. However, the aggregation of SLS in the various media is overall more spontaneous in the following order: SGF>FeSSIF>water. Using high throughput experimentation and in-vivo mechanistic modelling, it was determined that a combination oral solid product of compounds X and Y will have optimum solubility and in-vivo absorption if 2 mg of SLS was used in the oral solid dosage form.  The results obtained from this study will help broaden the understanding of the micellization process involving SLS and poorly-water soluble drugs used in combination oral solid dosage forms.

Evaluation of food effect on the oral absorption of clarithromycin from immediate release tablet using physiological modelling.

BACKGROUND: Food may affect the oral absorption of drugs. PURPOSE: The aim of the present study was to investigate the influence of food on the oral absorption of clarithromycin by evaluating the effect of media parameters, such as pH, bile secretions and food composition, on the release of the drug from immediate release tablets, using in vitro and in silico assessments. METHOD: The solubility, disintegration and dissolution profiles of clarithromycin 500 mg immediate release tablets in compendial media with/without the addition of a homogenized FDA meal as well as in biorelevant simulated intestinal media mimicking fasting and fed conditions were determined. These in vitro data were input to GastroPlus™, which was used for developing a physiological absorption model capable of anticipating the effect of food on clarithromycin absorption. Level A in vitro-in vivo linear correlations were established using a mechanistic absorption modelling based deconvolution approach. RESULTS: The pH of the media has a profound effect on clarithromycin solubility, tablet disintegration and drug release. Clarithromycin has lower solubility in biorelevant media compared with other media, due to complex formation with bile salts. Clarithromycin tablets exhibited prolonged disintegration times and reduced dissolution rates in the presence of the standard FDA meal. The simulation model predicted no significant food effect on the oral bioavailability of clarithromycin. The developed IVIVC model considered SIF, acetate buffer and FaSSIF media to be the most relevant from the physiological standpoint. CONCLUSION: The intake of a standard FDA meal may have no significant effect on the oral bioavailability of clarithromycin immediate release tablet.

Mechanistic study of absorption and first-pass metabolism of GL-V9, a derivative of wogonin.

GL-V9, a derivative of wogonin, has potent anti-cancer activity. The absorption and metabolism of this compound have not been investigated systematically. This study aims to illustrate the pharmacokinetic characters of GL-V9 by exploring its metabolic status under different administration routes. To further clarify the absorption mechanism of GL-V9, an in situ single-pass perfusion model and a Caco-2 cell monolayer model were used. Meanwhile, a microsomal incubation system was used to evaluate the enzyme kinetic parameters. In vivo, the obtained gastrointestinal availability (Fa × Fg ) was 21.28 ± 5.38%. The unmetabolized fraction in the gut wall (Fgut wall ) was 98.59 ± 9.74%, while the hepatic bioavailability (Fh ) was 29.11 ± 5.22%. These results indicated that poor absorption and extensive metabolism may contribute greatly to the low bioavailability of GL-V9. The effective permeability (Peff ) in the duodenum and jejunum was 1.34 ± 0.50 × 10-4 and 0.90 ± 0.27 × 10-4  cm/s, respectively. The high permeability of GL-V9 indicated that other unknown factors (such as metabolism) may account for its systemic exposure problem. Studies in rat liver microsomal (RLMs) confirmed this hypothesis, and the Clint, CYP450s and UGT of GL-V9 was 0.20 ml/min/mg protein. In conclusion, these results suggest that GL-V9 possesses higher permeability than wogonin and the metabolism of GL-V9 is related to its disposition in rat intestine and liver.

Gastric Emptying and Small Bowel Water Content after Administration of Grapefruit Juice Compared to Water and Isocaloric Solutions of Glucose and Fructose: A Four-Way Crossover MRI Pilot Study in Healthy Subjects.

Grapefruit juice (GFJ) is known to affect the bioavailability of drugs in different ways. Despite the influence on gastrointestinal enzymes and transporters, the influence on gastrointestinal fluid kinetics is regarded to be relevant for the absorption of several drugs. Thus, it was the aim of this pilot study to investigate the gastric and intestinal volumes after intake of GFJ compared to isocaloric fructose and glucose solutions and water. The gastric and small intestinal volume kinetics after intake of 240 mL of GFJ, 10.6% fructose solution, 10.6% glucose solution, and water were investigated with magnetic resonance imaging in a four-way crossover study in six healthy human volunteers. The carbohydrate content of the administered beverages was quantified by high-performance liquid chromatography. Even with the small sample size of this pilot study, the gastric emptying of GFJ and the glucose solution was significantly slower than that of water. The fructose solution had only a slightly delayed gastric emptying. Small bowel water content was increased by administration of GFJ and fructose solution, whereas it was decreased by glucose compared to the administration of pure water. At 80 min the small bowel water content after GFJ was twice as high as the small bowel water content after administration of water. The observed influence of GFJ on gastrointestinal fluid kinetics may explain certain phenomena in drugs pharmacokinetics. The effect is double edged, as the slower gastric emptying and increased intestinal filling can lead to enhanced or altered absorption. Due to the comparability of fruit juices, a general effect of fruit juices on gastrointestinal volumes is likely.

Crystallization from Supersaturated Solutions: Role of Lecithin and Composite Simulated Intestinal Fluid.

PURPOSE: The overall purpose of this study was to understand the impact of different biorelevant media types on solubility and crystallization from supersaturated solutions of model compounds (atazanavir, ritonavir, tacrolimus and cilnidipine). The first aim was to understand the influence of the lecithin content in FaSSIF. As the human intestinal fluids (HIFs) contain a variety of bile salts in addition to sodium taurocholate (STC), the second aim was to understand the role of these bile salts (in the presence of lecithin) on solubility and crystallization from supersaturated solutions, METHODS: To study the impact of lecithin, media with 3 mM STC concentration but varying lecithin concentration were prepared. To test the impact of different bile salts, a new biorelevant medium (Composite-SIF) with a composition simulating that found in the fasted HIF was prepared. The crystalline and amorphous solubility was determined in these media. Diffusive flux measurements were performed to determine the true supersaturation ratio at the amorphous solubility of the compounds in various media. Nucleation induction times from supersaturated solutions were measured at an initial concentration equal to the amorphous solubility (equivalent supersaturation) of the compound in the given medium. RESULTS: It was observed that, with an increase in lecithin content at constant STC concentration (3 mM), the amorphous solubility of atazanavir increased and crystallization was accelerated. However, the crystalline solubility remained fairly constant. Solubility values were higher in FaSSIF compared to Composite-SIF. Longer nucleation induction times were observed for atazanavir, ritonavir and tacrolimus in Composite-SIF compared to FaSSIF at equivalent supersaturation ratios. CONCLUSIONS: This study shows that variations in the composition of SIF can lead to differences in the solubility and crystallization tendency of drug molecules, both of which are critical when evaluating supersaturating systems.

Expression of recombinant truncated domains of mucus-binding (Mub) protein of Lactobacillus plantarum in soluble and biologically active form.

Mucins amount to 70% of total proteins present in mammalian mucus and serve as important substrata for bacterial adhesion. In probiotic bacteria such as Lactobacillus plantarum, surface adhesion proteins mediate its adhesion to mucus and adhesion is pivotal in bi-directional host-microbe interactions. Mucus binding (Mub) proteins are a group of bacterial surface adhesion proteins that bind to mucin proteins. The structural framework and functional role of these proteins needs immediate attention but is poorly understood because of their large size, low yield and lack of highly purified protein. The lp_1643 gene of L. plantarum encodes a large Mub protein of 240 kDa and has six mucus binding (Mub) domains in tandem. In this study, the fragment of lp_1643 containing the last two domains with their preceding spacers herein referred to as Mubs5s6 was cloned and expressed in E. coli for probing its functional role in the adhesion of L. plantarum. The protein was expressed with a solubility enhancing maltose binding protein (MBP) fusion tag, yet the MBP-Mubs5s6 protein expressed majorly (>90%) as biologically insoluble inclusion bodies. Thus, extensive optimization of culture conditions was carried out to achieve high level soluble expression (∼70%) of Mubs5s6 protein from its initial low level of solubility. The recombinant protein was purified up to homogeneity by affinity chromatography. Recombinant MBP-Mubs5s6 protein showed strong adhesion potential by binding with human intestinal tissue sections. Our results show a step-by-step hierarchical approach to improve the solubility of difficult-to-express extracellular surface proteins while retaining high functional viability.

Stability studies of potent opioid analgesic, morphine-6-O-sulfate in various buffers and biological matrices by HPLC-DAD analysis.

The 6-O-sulfate ester of morphine (M6S) has previously been shown to be an analgesic with greater potency and fewer side effects than morphine. However, being a sulfate ester derivative of morphine, the question exists as to whether this compound is stable in biological fluids and tissues with regard to pH- and esterase-mediated degradation. To date, no studies have focused on the stability profile of M6S across the physiologically relevant pH range of 1.2-7.4. In addition, the stability of M6S is not known in rat plasma and rat brain homogenate, or in simulated rat gastric and intestinal fluids. This study determines the stability profile of M6S (utilized as the sodium salt) and demonstrates that M6S is highly stable and resilient to either enzymatic- or pH-dependent hydrolysis in vitro.

High body clearance and low oral bioavailability of alantolactone, isolated from Inula helenium, in rats: extensive hepatic metabolism and low stability in gastrointestinal fluids.

Alantolactone (ALA) is a major bioactive sesquiterpene lactone present in the roots of Inula helenium L. (Asteraceae) which has been used widely in traditional medicine against various diseases such as asthma, cancer and tuberculosis. The pharmacologic activities of alantolactone have been well characterized, yet information on the physicochemical and pharmacokinetic properties of alantolactone and their mechanistic elucidation are still limited. Thus, this study aims to investigate the oral absorption and disposition of alantolactone and their relevant mechanisms. Log P values of alantolactone ranged from 1.52 to 1.84, and alantolactone was unstable in biological samples such as plasma, urine, bile, rat liver microsomes (RLM) and simulated gastrointestinal fluids. The metabolic rate of alantolactone was markedly higher in rat liver homogenates than in the other tissue homogenates. A saturable and concentration-dependent metabolic rate profile of alantolactone was observed in RLM, and rat cytochrome P450 (CYP) 1 A, 2C, 2D and 3 A subfamilies were significantly involved in its hepatic metabolism. Based on the well-stirred model, the hepatic extraction ratio (HER) was estimated to be 0.890-0.933, classifying alantolactone as a drug with high HER. Moreover, high total body clearance (111 ± 41 ml/min/kg) and low oral bioavailability (0.323%) of alantolactone were observed in rats. Taken together, the present study demonstrates that the extensive hepatic metabolism, at least partially mediated by CYP, is primarily responsible for the high total body clearance of alantolactone, and that the low oral bioavailability of alantolactone could be attributed to its low stability in gastrointestinal fluids and a hepatic first-pass effect in rats. Copyright © 2016 John Wiley & Sons, Ltd.

Comparison of biorelevant simulated media mimicking the intestinal environment to assess the solubility profiles of poorly soluble drugs.

During the discovery stage in lead identification/optimization, compounds are characterized for their solubilities in biorelevant media and these data are often used to model the in vivo behavior of the compounds and predict the fraction absorbed. These media are selected to closely approximate the composition of human intestinal fluid. Owing to the complexity and variability in human intestinal fluid composition, it is essential that the chosen simulated media mimic the in vivo condition as closely as possible. Several recipes have been developed and are routinely used in assessing the solubilities of compounds. It is necessary to revisit these recipes and modify them as the understanding of the human GI tract increases. In the present work, we have evaluated the solubilities of six model compounds in several media and have proposed slight modifications to the currently used recipes based on our own data and that reported in the literature.

Pomegranate Seed Oil Exerts Synergistic Effects with trans-Resveratrol in a Self-nanoemulsifying Drug Delivery System.

Pomegranate seed oil (PSO) has diverse bioactivities. It was hyphothesized that if PSO were employed to construct a trans-resveratrol-loaded self-nanoemulsifying drug delivery system (RES SNEDDS-PSO), not only could PSO serve as an oil phase but also exert synergistic effects with resveratrol to yield better therapeutic outcomes. In this study, we prepared RES SNEDDS-PSO for the first time to validate that hypothesis. The anti-inflammatory and anticancer activities of RES SNEDDS-PSO were compared with another SNEDDS composed of oil phase isopropyl palmitate (RES SNEDDS-IP). The results showed that upon exposure to a 10-fold amount of water, RES SNEDDS-PSO was converted into nanoemulsions with a mean size of 44 nm. Nanoemulsions enhanced the water solubility of resveratrol by 20-fold, significantly improved resveratrol stability in intestinal fluid, and slowed the decomposition of resveratrol in water by 1-fold. An in vivo anti-infection test showed that the degree of inflammatory swelling in mice given RES SNEDDS-PSO was only 60 and 76% that of the group fed with RES SNEDDS-IP at doses of 10 and 20 mg/kg, respectively. An in vitro anticancer study showed that the inhibitory rate of RES SNEDDS-PSO against MCF-7 breast cancer cells was 2.03- and 1.24-fold that of RES SNEDDS-IP at a concentration of 12.5 and 25 µg/mL, respectively. This study demonstrated that the newly developed SNEDDS may be a prospective formulation in the functional food and clinical fields.

Quality evaluation and in vitro interaction studies between levofloxacin 250mg and diclofenac sodium 50mg tablets.

Fluoroquinolones are broad-spectrum antibiotics, work against Gram-positive and Gram-negative bacteria and are a clinically proven option for many resistant infections. Among fluoroquinolones Levofloxacin works best against acute sinusitis, inflammation of the lower airways, acute exacerbation of chronic bronchitis, community acquired pneumonia, complicated urinary tract infection including Pyelonephritis, chronic bacterial prostatitis and skin and soft tissue infection. Levofloxacin is a frequently prescribed antibacterial agent with Diclofenac Sodium for pain management in infectious conditions. The objective of the present work is to evaluate the level of interaction between Levofloxacin and Diclofenac Sodium. In this work market available brands of both drugs were also evaluated for quality.The physiochemical parameters like weight variation, thickness variation, and mechanical strength were determined. Similarly the percentage drug release and content uniformity test were also analyzed; the tested quality attributes were found within the recommended pharmacopeia ranges except brand L(6) that had high drug content 124.629±3.614 while brand L(4) and L(5) were not found similar in pH 1.2. When subjected to model dependent analysis Levofloxacin showed compliance with (first order, Higuchi, Hixson Crowell and Weibull) at pH (1.2, 4.5 and 6.8). However Diclofenac Sodium showed adherence with (first order, Hixson Crowell and Weibull) at pH (1.2, 4.5 and 6.8) but following Higuchi at pH 1.2 and 4.5 only. The interaction studies were also performed spectrophotometrically and simultaneous equation was used to estimate the percentage availability of both the drugs at pH 4.5, 6.8, FaSSGF and FaSSIF. The studies showed that the percent availability of Levofloxacin was increased significantly in FaSSIF i.e. 129.173±0.323 at 45 minutes in the presence of Diclofenac Sodium.

A novel simulated media system for in vitro evaluation of bioequivalent intestinal drug solubility.

Orally administered solid drug must dissolve in the gastrointestinal tract before absorption to provide a systemic response. Intestinal solubility is therefore crucial but difficult to measure since human intestinal fluid (HIF) is challenging to obtain, varies between fasted (Fa) and fed (Fe) states and exhibits inter and intra subject variability. A single simulated intestinal fluid (SIF) cannot reflect HIF variability, therefore current approaches are not optimal. In this study we have compared literature Fa/FeHIF drug solubilities to values measured in a novel in vitro simulated nine media system for either the fasted (Fa9SIF) or fed (Fe9SIF) state. The manuscript contains 129 literature sampled human intestinal fluid equilibrium solubility values and 387 simulated intestinal fluid equilibrium solubility values. Statistical comparison does not detect a difference (Fa/Fe9SIF vs Fa/FeHIF), a novel solubility correlation window enclosed 95% of an additional literature Fa/FeHIF data set and solubility behaviour is consistent with previous physicochemical studies. The Fa/Fe9SIF system therefore represents a novel in vitro methodology for bioequivalent intestinal solubility determination. Combined with intestinal permeability this provides an improved, population based, biopharmaceutical assessment that guides formulation development and indicates the presence of food based solubility effects. This transforms predictive ability during drug discovery and development and may represent a methodology applicable to other multicomponent fluids where no single component is responsible for performance.

Drug solubilization in dog intestinal fluids with and without administration of lipid-based formulations.

The use of animal experiments can be minimized with computational models capable of reflecting the simulated environments. One such environment is intestinal fluid and the colloids formed in it. In this study we used molecular dynamics simulations to investigate solubilization patterns for three model drugs (carvedilol, felodipine and probucol) in dog intestinal fluid, a lipid-based formulation, and a mixture of both. We observed morphological transformations that lipids undergo due to the digestion process in the intestinal environment. Further, we evaluated the effect of bile salt concentration and observed the importance of interindividual variability. We applied two methods of estimating solubility enhancement based on the simulated data, of which one was in good qualitative agreement with the experimentally observed solubility enhancement. In addition to the computational simulations, we also measured solubility in i) aspirated dog intestinal fluid samples and ii) simulated canine intestinal fluid in the fasted state, and found there was no statistical difference between the two. Hence, a simplified dissolution medium suitable for in vitro studies provided physiologically relevant data for the systems explored. The computational protocol used in this study, coupled with in vitro studies using simulated intestinal fluids, can serve as a useful prescreening tool in the process of drug delivery strategies development.

In vitro phosphate-binding ability of calcium-based agents is augmented by co-administration of activated charcoal.

BACKGROUND: Calcium carbonate is widely used as a phosphate binder in patients on maintenance hemodialysis. An unwanted side effect of calcium carbonate is hypercalcemia and vascular calcification. Oral activated charcoal (AC) is a non-selective and highly effective adsorbent. We hypothesized that AC augments the phosphate binding capacity of calcium-based agents. We performed an in vitro study to test this hypothesis. METHODS: Simulated gastric fluid and intestinal fluid were prepared with a phosphate concentration of 10 mmol/l. Different dosages of calcium chloride (0.083 g, 0.167 g, and 0.250 g), AC (0.15 g, 0.30 g, and 0.45 g) or a combination of both were added to either gastric or intestinal fluid for phosphate binding. After a reaction time of 2 hours, phosphate concentrations in the supernatant were measured, and absolute reduction and percent reduction of phosphate were calculated. The phosphate-binding abilities of calcium chloride, AC, and a combination of both were compared. RESULTS: In simulated intestinal fluid there was no significant difference in the percent reduction of phosphate concentrations among the different calcium chloride concentration groups (28.90 ± 2.04 vs. 33.33 ± 3.90 vs. 31.86 ± 5.23) and there was still no significant difference in phosphate concentrations among the different AC groups (3.33 ± 0.08 vs. 3.26 ± 0.01 vs. 3.36 ± 0.11). In simulated gastric fluid phosphate concentrations at each of the time points (before the reaction, 1 hour after calcium chloride was added, and 2 hours after AC was added) were not significantly different. In simulated intestinal fluid the percent decrease in phosphate concentration in the calcium chloride + AC group was significantly higher than that in the calcium chloride group (48.23 ± 5.55 vs. 30.72 ± 6.11). CONCLUSIONS: AC alone had no phosphate-binding ability in either gastric or intestinal fluid. The phosphate-binding ability of calcium chloride was improved by AC in intestinal fluid.

Activities of free and encapsulated Lactobacillus acidophilus LA5 or Lactobacillus casei 01 in processed longan juices on exposure to simulated gastrointestinal tract.

BACKGROUND: Fruit drinks containing probiotics are gaining interest in the global marketplace. For example, longan juice, containing carbohydrate and various bioactive components, is a potentially health-promoting beverage as well as probiotic carrier for human consumption. In this study, high-pressure and thermal processes were applied to eliminate competitive micro-organisms in longan juice prior to the addition of Lactobacillus acidophilus LA5 or Lactobacillus casei 01. The activities of these probiotics in a simulated gastrointestinal tract were also investigated. RESULTS: Encapsulated probiotics could survive in the acidic environment of the stomach and small intestine, while the free cells were completely eliminated. In the colon experiment, the influence of encapsulated L. casei 01 on colon lactobacilli was significantly greater than that of encapsulated L. acidophilus LA5. Both encapsulated probiotics suspended in processed longan juices led to extensive increases in the formation of lactic acid and short-chain fatty acids (SCFA). Acetate was the major SCFA produced by colon bacteria, followed by propionate and butyrate. The discernible clear zone suggested that L. casei 01 provided greater antibacterial activity than L. acidophilus LA5. CONCLUSION: Both encapsulated probiotics along with processed longan juice led to significant increases in colon lactobacilli, lactic acid and SCFA formation.