Bile Salt Aggregates Research Articles

Efficiency of Encapsulation of Thioflavin T (ThT) into Polar and Nonpolar Environments of Different Bile Salt Aggregates: A Femtosecond Fluorescence Study.

The binding of Thioflavin T (ThT) with various bile salts, a potential host molecule, has been analyzed by steady-state and time-resolved fluorescence spectroscopy. A comparative study has been executed to investigate the influence of confinement of different bile salts, namely, sodium cholate (NaCh), sodium taurocholate (NaTC), and sodium deoxycholate (NaDC) on binding and excited state torsional motion of ThT molecules. The changes in absorption and emission properties of probe molecules were found to be sensitive to increasing bile salt concentration in aqueous 0.2 (M) NaCl solutions. The photophysics of ThT mainly depends on hydrophobicity, morphology, and size of bile salt aggregates in solution. In the presence of bile salts, the emission intensity and emission lifetime of ThT increase significantly, indicating encapsulation of dye. Moreover, we have also investigated the effect of the ionic strength of the medium by sodium chloride (NaCl) on the spectroscopic properties of ThT in the restricted surroundings of aqueous bile salts. It is observed that the fluorescence lifetime of ThT in bile salts increases significantly in the presence of NaCl. The encapsulation efficiency of ThT in bile salt aggregates has been assessed by iodide (I-) as an external ionic quencher. We found that NaDC aggregates are more efficient in the modulation of photophysical properties of ThT and also provide better protection efficiency to decrease the nonradiative deactivation processes.

Regulated the aggregation of bile salts by β-Cyclodextrin and Tangeretin at the oil-water interface for inhibiting lipid digestion

Our previous research has demonstrated that the changes in oil-water interface properties during dietary digestion have a significant impact on the digestion and absorption of lipids. In this study, these methods of interfacial tension, microscopic examination, isothermal titration calorimetry (ITC), molecular dynamics (MD) simulations, and free fatty acid (FFA) release were used to evaluate the effect and mechanism of assembly behavior of tangeretin (TAN) and β-cyclodextrin (β-CD) at the oil-water interface on the rate of lipid digestion. The results showed that the combination of β-CD and TAN at the oil-water interface made the interfacial tension first increase and then decrease with the increase of TAN: β-CD ratios (M: M, 1:1–20). The self-assembled structure formed by the interaction of TAN and β-CD can produce stronger interaction with bile salts, which makes bile salts flocculate at the oil-water interface. The FFAs release experiment showed that a TAN: β-CD molar ratio of 1:8 exerted the highest inhibitory (34.92%) effect on lipid digestion. Furthermore, the results from ITC and MD simulations confirmed that BS exhibited stronger binding affinity with the TAN/β-CD complex. These results suggested that the TAN/β-CD complex caused the bile salts to prematurely gather at the oil-water interface, thereby thickening the interfacial layer, hindering the displacement of bile salts and lipase between droplets, and ultimately impeding lipid digestion. This study emphasized the promising potential of the synergistic effect between cyclodextrin and flavoring molecules in inhibiting lipid digestion, proposing a novel avenue for the development of reduced-fat foods with enhanced health benefits.

Tailoring the Self-Assembly of Steviol Glycoside Nanocarriers with Steroidal Amphiphiles.

Bile salts are biosurfactants that can induce structure transformations in supramolecular nanoassemblies with conventional surfactants owing to their unique, planar amphiphilic character and the rigidity of their hydrophobic steroid skeleton. However, structural information about the association of bile salts and amphiphilic glycosides is lacking. In this work, we investigated the micelle structure of two anionic di- and trihydroxy bile salts [sodium deoxycholate (SDC) and sodium cholate (SC)] and a conventional anionic surfactant [sodium dodecyl sulfate (SDS)] in mixtures with a nonionic steviol glycoside [α-glucosyl stevia (Stevia-G)] and studied their potential as a nanocarrier system for two poorly water-soluble drugs (clotrimazole and ketoconazole). Decreased critical micelle concentrations determined from surface tension measurements demonstrate synergistic interactions between Stevia-G and SDS/SDC/SC in a decreasing order. Small-angle X-ray and neutron scattering, interpreted by a core-shell ellipsoid model, indicate that SDS and bile salts act differently on the mixed micelle structure. Compared with SDS/Stevia-G, bile salt/Stevia-G had a core-shell structure more similar to that of pure Stevia-G micelles. SDC and SDS had an increasing and decreasing influence, respectively, on the available molecular surface area in mixtures with Stevia-G on the micelle core but a similar influence on the micelle shell solvation number relative to that of their pure micellar structures. The number of bile salt hydroxyl groups was influential in determining the micelle stoichiometry: an increasing number of hydroxyl groups corresponded to decreasing bile salt aggregation numbers and a smaller hydrophobic micellar core. The core volume was the most important structural factor in explaining the drug solubilization capacity of the nanocarrier systems. Therefore, bile salt-steviol glycoside mixed micellar assemblies exhibit structure control mechanisms allowing the fine-tuning of their interior hydrophobic domains important for nanocarrier applications toward solubilization of poorly water-soluble drugs.

New Potentially Probiotic Strains Isolated from Humans - Comparison of Properties with Strains from Probiotic Products and ATCC Collection.

Lactic acid bacteria are used in various types of probiotic products. Due to the constantly growing probiotics market, new strains with pro-health properties are sought. The present study compared 39 strains of Lactobacillus, Lacticaseibacillus, and Lactiplantibacillus, isolated from probiotic products and healthy people. The current research aimed to search for new, potentially probiotic strains. For this purpose the relationship between Lactobacillaceae strains was carried out; moreover, the basic properties of probiotic microorganisms, such as survival at low pH and bile salt environment, antibiotic susceptibility, aggregation and antagonism were estimated. The properties of these isolates were also compared with the properties of probiotic strains from the ATCC collection. In comparing the genetic relationship (PFGE method) between the tested isolates, it was observed that some of them show a high degree of similarity. All tested strains tolerated an environment with a pH value of 3.0, and the addition of 0.3% bile salt; showed auto-aggregation properties and displayed antagonism against pathogenic microorganisms. In the present study, the bacteria were susceptible to tetracycline, chloramphenicol and ampicillin; the resistance to vancomycin depended on the bacteria type. All the properties were strain-depended. Most of the tested strains had properties comparable to the reference strains. Three L. acidophilus strains isolated from cervical swabs seem to be promising candidates for probiotic strains.

Evaluation of inhibitory and probiotic properties of lactic acid bacteria isolated from vaginal microflora.

Lactic acid bacteria (LABs) are known to secrete species-specific secondary metabolites that could be utilized as novel therapeutics against multi-drug resistant pathogens. This study aimed to investigate the antagonistic and probiotic properties of LABs isolated from the vaginal ecosystem of healthy women and to assess the stability of their antagonistic metabolites. Among 43 strains isolated from healthy women, eight LAB strains exhibited detectable BLISs (bacteriocin-like substances) producing ability against E. faecalis (JH-86), S. aureus (JH-68), Streptococcus sp. (JH-80), and E. coli (JH-101), with zone of inhibition (ZI) ranging from 9.00 to 20.33mm and minimum inhibitory concentrations (MICs) from 62.5 to 500 μL/mL, respectively. The partially purified compounds extracted from cell free supernatant (CFS) displayed an increase in antagonistic activity based on ZI, 9.67-30.17mm and MICs, 3.91-15.63mg/mL, respectively. In a time-kill study, both crude and partially purified compounds of Limosilactobacillus reuteri (MT180537), Pediococcus pentosaceus (MT176555), Limosilactobacillus pontis (MW362838), and Levilactobacillus brevis (MW362790) exhibited significant bactericidal action against E. faecalis (MW051601), the most frequent etiological agent of aerobic vaginitis (AV). The active secondary metabolites from L. reuteri (MT180537), P. pentosaceus (MT176555), and L. pontis (MW362838) were protein in nature and remained stable under different physicochemical conditions. Regarding probiotic properties, the strains presented probiotic characteristics, i.e., good acid, bile salt tolerance, aggregation properties, and biofilm formation. The strains were susceptible to most of the commonly used antibiotics and had no hemolytic activity. In conclusion, antagonistic compounds or BLIS produced by L. reuteri (MT180537) could be investigated further for preparation of ointments to treat AV.

Bile Salts in Chiral Micellar Electrokinetic Chromatography: 2000-2020.

Bile salts are naturally occurring chiral surfactants that are able to solubilize hydrophobic compounds. Because of this ability, bile salts were exploited as chiral selectors added to the background solution (BGS) in the chiral micellar electrokinetic chromatography (MEKC) of various small molecules. In this review, we aimed to examine the developments in research on chiral MEKC using bile salts as chiral selectors over the past 20 years. The review begins with a discussion of the aggregation of bile salts in chiral recognition and separation, followed by the use of single bile salts and bile salts with other chiral selectors (i.e., cyclodextrins, proteins and single-stranded DNA aptamers). Advanced techniques such as partial-filling MEKC, stacking and single-drop microextraction were considered. Potential applications to real samples, including enantiomeric impurity analysis, were also discussed.

Encapsulation and release of non-fluorescent crystal violet confined in bile-salt aggregates.

In this work, the entrapment of non-fluorescent dye Crystal Violet (CV) in presence of bio-mimetic confined bile-salt aggregates has been studied. The photophysical characteristic properties of CV have been carried out by changing different kinds of hydrophilic head groups and hydrophobic skeletons of bile-salt aggregates (NaC, NaDC, NaTC and NaTGC). The main aim of this work is to modulate the solubility behaviour, fluorescence properties and elucidation of different kinds of non-covalent interaction of CV confined in bile-salt aggregates. To interpret the result, steady state absorption and fluorescence emission techniques have been employed. In aqueous buffer, the CV molecule is non-fluorescent in nature. The value of fluorescence quantum yield (Φ) is ∼10−4. It has been observed that CV confined in bile-salt aggregates becomes highly fluorescent in nature. The enhancement of ‘Φ’ value of CV in bile-salt aggregates is ∼1000 fold compared to that of aqueous buffer medium. It has also been observed that in the presence of different bile-salt aggregates, CV exhibits remarkable enhancement of absorption and fluorescence emission spectral behaviour. The ground state and the excited state binding constant values of CV in the presence of different bile-salt aggregates have been determined. Moreover, the release of the dye molecule from the confined bile-salt aggregates to the aqueous medium has been executed. It has been found that addition of a very minute concentration of KCl salt (100 nm) to the bile-salt aggregates leads to extreme modification of their photophysical properties of CV. The absorption, fluorescence intensity, fluorescence quantum yield, ground state and excited state binding constant values, partition coefficient and aggregation number of CV molecules entrapped in bile-salt aggregates significantly reduces by addition of KCl. This result clearly confirms that CV releases from the confined system to the aqueous medium.

Probiotic potential and amylolytic properties of lactic acid bacteria isolated from Chinese fermented cereal foods

This study investigated the probiotic potential and amylase properties of amylolytic lactic acid bacteria (ALAB) isolated from fermented cereal-based foods in China. Of 132 LAB isolates screened for amylase production, three (430, 445, and 472) were found to have high amylase activities (8.15, 9.23, and 8.06 U/mL in MRS-1% starch broth, respectively). These three strains were identified as Lactobacillus plantarum by 16 S rRNA sequencing. Optimization of the starch content in the culture broth, pH, and temperature during fermentation revealed that the highest amylase activity (15.89 ± 0.51 U/mL) was found in L. plantarum 445. Moreover, the three ALAB isolates were assessed for their probiotic properties, tolerance to low pH, bile salt resistance, and antimicrobial and aggregation activities. All three ALAB isolates showed good survival at pH 2.0 and 3.0 and were resistant to 0.3% and 0.6% bile salts after 48 h of incubation. They also had different antimicrobial activities against five food-borne pathogens and similar intrinsic and non-transmissible antibiotic susceptibilities. The isolates had higher auto-aggregation ability but weaker co-aggregation ability than the reference strain, Lactobacillus rhamnosus ATCC 53103. These data demonstrate that the three ALAB isolates possess potential probiotic characteristics, suggesting that they are suitable candidates for cereal-based probiotic products and starter cultures for improving the cereal fermentation process.

P.233 Doxycycline attenuates anxiety and microglia activation induced by repeated lipopolysaccharide

Sodium hyodeoxycholate (NaHDC) is the main component of hog bile salts, which play a role in the absorption of sparingly soluble materials in the intestinal solution. The biosurfactant has an amphiphilic molecular structure, similar to that of ursodeoxycholate from bear gallbladder. Micelle formation from hyodeoxycholate was studied at 308.2 K using pyrene fluorescence probe to determine critical micelle concentrations (cmc) at various NaCl concentrations. The change in the fluorescence spectrum peak ratios with NaHDC concentration indicated two steps for bile salt aggregation. The first step was the formation of small micelles (cmc) at 5 mM, and the second step was the formation of stable aggregates at 14 mM in aqueous solution. The aggregation of hyodeoxycholate, analyzed using the stepwise association model, was found to grow its aggregation number from 4 to 7 with increasing concentration. The aggregation number in aqueous solution was also confirmed by the static light scattering method. The average measured aggregation number of the micelles was 6.7. The micellar size was relatively small as measured by either method, but it was covered by general aggregation number of human bile salts. The degree of counterion binding to the micelles, determined using a sodium ion-selective electrode, was ca. 0.5 for the NaHDC micelles. This value was relatively high among typical bile salts. Moreover, the solubilization capacity of the NaHDC micelles was assessed using cholesterol. It became clear that NaHDC micelles hardly solubilized cholesterol compared to typical human bile salts. The maximum solubilization by NaHDC was equivalent only to that by sodium ursodeoxycholate

Photophysical Properties of Coumarin 1 in Bile Salt Aggregates: An Insight into the Role of Bile Salt Structure on the Aggregation Behavior.

The photophysical behavior of Coumarin 1 (Cou1), a well-known 7-aminocoumarin derivative, is very sensitive to the microenvironment in which it resides. In the present study, the effect of six bile salt variants on the photophysical behavior of Cou1 has been investigated. Dihydroxy (deoxycholates) as well as trihydroxy (cholates) bile salts with conjugated and unconjugated side chains have been chosen to get insight into the role of bile salt structure on the microenvironment of Cou1. Cou1 photophysics was found to be extremely sensitive to the aggregation process of the bile salt variants. The reduced polarity of the micellar environment stabilizes the planar intramolecular charge transferred state of Cou1, resulting in significant modulation in its photophysics in the bile salt media. The changes in the fluorescence parameters such as fluorescence intensity, emission energy, fluorescence quantum yield, anisotropy, and lifetime of Cou1 reveal that there is a distinct difference in the aggregation behavior of deoxycholates from that of cholates. The deoxycholates form micelles more or less critically similar to those of conventional surfactants, whereas the cholates self-assemble rather noncritically over a wide concentration range, thus signifying the vital role of the extra hydroxyl group in the aggregation pattern of trihydroxy bile salts. The conjugated bile salts are found to provide a relatively more compact, rigid, and hydrophobic microenvironment to Cou1 as compared to their unconjugated counterparts. Considering the significant modulation in the photophysical properties of Cou1, it has been employed as a molecular reporter for monitoring the aggregation process of bile salt variants and important information could be obtained about the effect of bile salt structure on the aggregation pattern and also about the micellar properties.

Revealing the dynamics and energetics of interaction of a cationic biological photosensitizer within a bile salt aggregate.

The present investigation reports a detailed characterization of the interaction of a cationic photosensitizer, phenosafranin (PSF) with sodium deoxycholate (NaDC) bile salt aggregates based on spectroscopic and calorimetric techniques. Our explicit spectroscopic results not only establish the occurrence of PSF-NaDC binding interaction, but also reveal marked lowering of micropolarity at the interaction site (ET(30) = 55.97 kcal mol-1 in the presence of NaDC as compared to ET(30) = 63.1 kcal mol-1 in bulk aqueous buffer). A thorough mathematical analysis of the fluorescence depolarization results based on the two-step and wobbling in cone model yields critical insight into the complex rotational relaxation dynamics of the bound drug. The impartation of motional restriction on the PSF molecules within the bile salt aggregates is evidenced from enhancement of average rotational correlation time from <τr> = 136 ps in aqueous buffer to 1.11 ns with added NaDC (8.0 mM). This is further supported from a high value of the generalized order parameter (S = 0.81) as well as the diffusion coefficient (Dw = 1.40 × 1012 s-1). Furthermore, our extensive calorimetric investigation unveils the complicated thermodynamics of the interaction process in terms of predominant entropic contribution over the enthalpic part in the lower temperature regime (TΔS = 18.84 ± 1.13 kJ mol-1, ΔH = -5.82 ± 0.35 kJ mol-1 at 288 K) with subsequent reversal of the relative contributions with increasing temperature (TΔS = 7.54 ± 0.39 kJ mol-1, ΔH = - 17.09 ± 0.90 kJ mol-1 at 318 K). The instrumental role of the hydrophobic effect underlying the PSF-NaDC interaction is characterized by a negative heat capacity change (ΔCp = -364 J mol-1 K-1). An intriguing thermodynamic feature in terms of enthalpy-entropy compensation (with increasing temperature ΔG remains almost constant while ΔH and TΔS vary significantly) aptly corroborates the aforesaid argument and establishes an appreciable hydrophobic contribution to the overall binding energies.

Probiotic Candidates Yeast Isolated from Dangke - Indonesian Traditional Fermented Buffalo Milk

The aim of the study was to isolate and identify the yeast isolated from Dangke and its potential as probiotics. The purified isolates obtained were identified based on observations of macroscopic characteristics of colonies and microscopic cells. The ability as a probiotic yeast is obtained by testing the resistance towards acid conditions, bile salt resistance test and aggregation ability test against pathogenic bacteria using Salmonella sp. The yeast isolates were identified using the RapID Yeast Plus System. The isolation result was obtained D.10.3.d isolate that identified as Candida guilliermondii which showed probiotic characteristic. The yeast colony is round, cream‑colored, smooth surfaces, low convex elevations and entire edges, capable of growing on mediums with the pH of 4, containing 1 % and 5 % of bile salts and having the ability to aggregate Salmonella sp. at 15, 60, and 180 minutes.

Insights into the Mechanism of Bile Salt Aggregates Forming in a PEGylated Amphiphilic Polymer/Bile Salt Mixed Micelle

AbstractTailoring the structure of core‐shell interface of amphiphilic copolymer micelles provides a potential to mediate the drug release from micelles. Here, bile salts were used to alter the molecular geometry of core‐shell structured amphiphilic copolymer micelles. With the different sodium deoxycholate (NaDC) addtions in the methoxy polyethylene glycol‐poly(D,L‐lactic acid) (MPEG‐PDLLA) solutions, the NaDC molecule could form different deoxycholic acid (DCA) dimers in the core and shell of micelles. A face‐to‐face DCA dimer structure could form and insert into the core of micelles when a small NaDC addition. This dimer could accelerate the drug release. At a high NaDC addition, a new back‐to‐back DCA dimer could form in the PEG shell region that would reduce the rate of drug release. The results obtained provide fundamental insights into the role of bile salts in adjusting the drug release of amphiphilic copolymer micelles and demonstrate the future potential for controlled drug‐delivery applications.

Effect of Bile Salt Aggregates on the Prototropic Equilibria of Harmine, a Fluorescent β‐Carboline Alkaloid

AbstractInterconversion between different ground and excited state prototropic forms of harmine (cation, neutral and zwitterionic forms) in presence of bile salt aggregates has been monitored using steady state and time‐resolved fluorescence spectroscopic techniques. The existence of two binding pockets in bile salt assembly with distinctly different polarity preferences gives rise to significant modulation in the prototropic equilibrium in terms of conversion of cation→neutral and cation*→zwitterionic* in the ground and excited states, respectively. The excited state conversion of cation*→zwitterionic* has been confirmed by both TRANES and TRES profiles and a clear iso‐emissive point indicates an excited state equilibrium between cation and zwitterionic forms. We have also observed that small variations in the hydrophilic head groups of the bile salt monomers changes the spectral feature of harmine appreciably. In non‐conjugated bile salt (NaC), both cation→neutral and cation*→zwitterionic* conversions occur while, in conjugated bile salt (NaTC) conversion from cation*→zwitterionic* is not observed due to stronger electrostatic interactions of C with NaTC head group. The coexistence of cation, neutral and zwitterionic forms in the excited state gives rise to simultaneous emission from three prototropic forms in NaC, which has not been previously observed at neutral pH.

Differential Perturbation of the Protrotropic Equilibrium of a Biological Photosensitizer within Bile Salt Aggregates of Varying Hydrophobicity: A Fluorimetric Investigation.

The present work reveals the binding interactions of a credible cancer cell photosensitizer, harmane (HM), with some selected bile salt aggregates of dissimilar hydrophobicity viz. sodium deoxycholate (NaDC), sodium cholate (NaC) and sodium taurocholate (NaTC). The explicit variation of the prototropic equilibrium of the photosensitizer both in the ground and excited state has been utilized to scrutinize the interaction phenomena. Differential modulation in the prototropic equilibrium of HM in the aforesaid aggregates has been explained on the basis of the structural dissimilarities of the bile salt monomers. The contrived hydrophobic surroundings provided by the aggregates have been reflected on the spectroscopic results, especially in the time-resolved fluorescence and the rotational dynamical behavior of the molecule of interest. Slow solvent reorientation time with regard to the lifetime of HM proliferated by the red-edge effect in two specific bile salts namely NaC and NaTC, whereas its absence in NaDC aggregates has also been elucidated on the basis of accessibility of the solvent molecules within the aggregates.

Differential interaction behaviors of an alkaloid drug berberine with various bile salts

The present study reports a meticulous characterization of the interaction of a potent anti-cancer drug, berberine chloride (BR) with a series of bile salt aggregates having varying hydrophobicity (sodium deoxycholate (NaDC), sodium cholate (NaC), and sodium taurocholate (NaTC)). The absorption spectrum of BR reveals a complex profile comprised of four distinct peaks. Analysis of the modulations of the absorption spectral properties of BR following interaction with the bile salts raising deeper questions unveils a critical insight into the mode of interaction of the cationic drug (BR) with the bile salts; a greater degree of perturbation of the microenvironment of the isoquinolinic part of BR compared to the benzenoid part. The remarkable modulation of the fluorescence profile of BR with added bile salts provides a sensitive indicator for monitoring the interaction scenario. However, an intriguing observation in this context reveals differential fluorescence behavior of BR in various bile salt aggregates, that is, similar observations in NaDC and NaC (which are legitimately interpreted according to the ‘two-step association model’) in comparison to NaTC. Such contrasting behavior of BR in NaTC aggregates has been rationalized on the basis of the possibility of formation of dye aggregate facilitated because of the proximity of the cationic drug molecules to the anionic headgroup of NaTC bile salt. Surprisingly, our spectroscopic results evidence for binding location of the drug at the interfacial region in all the bile salt aggregates. To this end, the time-resolved fluorescence decay behavior of the drug within various bile salt aggregates has been meticulously studied. The fluorescence decay results are found to be highly sensitive to the structure and size of the bile salt aggregates eventually leading to characterization of the interaction of the drug with the bile salts in excellent corroboration with the steady-state data. Furthermore, the time-resolved fluorescence anisotropy decay measurements yielded insight into the modulation of rotational dynamical behavior of the drug within the bile salt aggregates.

Slow solvation dynamics in supramolecular systems based on bile salts: Role of structural rigidity of bile salt aggregates

The dynamical aspects of solvation has been explored in supramolecular biomimetic systems of bile salt aggregates, using an intramolecular charge transfer (ICT) dye 5-(4″-dimethylaminophenyl)-2-(4′-sulfophenyl)oxazole, sodium salt (DMO). The solvation response is bimodal, with a fast time constant of a few tens of picoseconds due to relaxation of the hydrophilic surface-bound water molecules, and a slower component of few nanoseconds, originating from the coupling of the structural flexibility of the bile salt aggregates with their hydration dynamics. The dynamics of solvation is mainly governed by the slower nanosecond relaxation component, due to its dominant contribution (68–90%), and is significantly retarded (average solvation time ∼4.9 ns) in the aggregates of sodium deoxycholate (NaDC) relative to sodium taurocholate (NaTC) or sodium cholate (NaCh), (∼2.2–2.7 ns). From the time-resolved anisotropy decay measurements, a strong correlation between the structural rigidity of the bile salt aggregates and the slower relaxation component is observed, which clearly demonstrates the presence of a strong dynamical coupling between the structural flexibility of the bile salt aggregates and their hydration water. The local structure of the dye environment is significantly more rigid in the bile salt aggregates of NaDC than NaCh or NaTC, owing to higher rigidity of the former, which directly influences the neighboring water-network flexibility and hence, coupled water-bile salt fluctuations. In consequence, a remarkably slower dynamics of solvation is manifested in the more rigid aggregates of NaDC than the more flexible aggregates of NaCh or NaTC.

Impact of Bile Salts on Solution Crystal Growth Rate and Residual Supersaturation of an Active Pharmaceutical Ingredient

Supersaturating formulations have become a popular approach to address the issue of inadequate aqueous solubility for small molecules. Given that prevention of nucleation may not be always possible, it is of particular interest to control crystal growth from supersaturated solutions in order to maximize the extent of oral absorption of therapeutic agents. Bile salts are endogenous surfactants that are present in biorelevant dissolution media and can have direct impact on the in vivo performance of therapeutic agents due to their presence in the gastrointestinal tract. In this study, an in situ common history seeding method was implemented to provide seeds that better mimic crystals formed from aqueous supersaturated solutions. By forming seeds in situ and then regenerating supersaturation, we were able to probe the influence of biorelevant bile salts on telaprevir crystal growth rates and secondary nucleation. The extent of growth inhibition was found to vary with bile salt chemistry and aggregation level...

Interaction of Biologically Active Flavins inside Bile Salt Aggregates: Molecular Level Investigation.

In this work we have studied the photophysics of biologically active flavin molecule lumichrome (LCM) in different bile-salt aggregates. With alteration of the functional groups of the bile salts, the photophysics of confined fluorophore is largely affected and shows difference in their spectral behavior. This study also reveals the selective prototropic species of LCM present in bile salt aggregates. In the presence of the bile salt aggregates, LCM molecule shows excitation and emission wavelength-dependent emission properties, indicating switch over of the structural change of different prototropic form of the LCM molecule. The observation of higher rotational relaxation time in NaDC aggregates compared to NaTC aggregates clearly reflects that NaDC aggregates are more rigid due to its greater hydrophobicity and large in size, which is capable to bind the guest molecule more into their nanoconfined medium. Moreover, due to less acidic nature, NaDC aggregates have more ability to accept hydrogen bond from the LCM molecule and show the selective formation of isoalloxazine N10 anion (A1 monoanionic form) of LCM.

Modulated photophysics of an anthracene-based fluorophore within bile-salt aggregates: the effect of the ionic strength of the medium on the aggregation behavior

In this article, the binding interactions of a promising chloride channel blocker 9-methyl anthroate (9-MA) with a series of bile-salt aggregates of varying hydrophobicity have been thoroughly demonstrated. The altered photophysical properties of the fluorescent probe within the concerned microheterogeneous environments have been exploited spectroscopically to assess the communication between the aggregates and the guest. The contrived hydrophobic environment provided by the aggregates appreciably diminishes the water-assisted non-radiative decay channels and thus extends the fluorescence lifetime and the rotational relaxation time of the probe. NaDC aggregates, being more rigid and hydrophobic, provide a better protection to the bound guest from the external influence which is apparent from a much longer fluorescence lifetime and rotational correlation time for the encapsulated probe in NaDC aggregates compared to those in NaC and NaTC aggregates, as is further validated by fluorescence quenching experiments. Salt induced alterations of the binding behavior of the probe with the bile-salt aggregates have also been evaluated via fluorimetric studies, which conclude larger and tighter aggregate formation resulting in a superior degree of rigidity imposed on the aggregate-bound probe at high ionic strength of the medium.