Modified bile acids as carriers for peptides and drugs

Bile acid-based advanced drug delivery systems, bilosomes and micelles as novel carriers for therapeutics

Diabetes mellitus affects almost half a billion patients worldwide and results from either destruction of β-cells responsible for insulin secretion or increased tissue resistance to insulin stimulation and the reduction of glycemic control. Novel drug delivery systems can improve treatment efficacy in diabetic patients. The low aqueous solubility of most oral antidiabetic drugs decreases drug bioavailability; therefore, there is a demand for the use of novel methods to overcome this issue. The application of bile acids mixed micelles and bilosomes can provide an enhancement in drug efficacy. Bile acids are amphiphilic steroidal molecules that contain a saturated tetracyclic hydrocarbon cyclopentanoperhydrophenanthrene ring, and consist of three 6-membered rings and a 5-membered ring, a short aliphatic side chain, and a tough steroid nucleus. This review offers a comprehensive and informative data focusing on the great potential of bile acid, their salts, and their derivatives for the development of new antidiabetic drug delivery system.

Synergistic activity of bile salts and their derivatives in combination with conventional antimicrobial agents against Acinetobacter baumannii

ETHNOPHARMACOLOGICAL RELEVANCE

Bile traditionally was used in wound healing, having erodent, antioxidant and antimicrobial potential. Acinetobacter baumannii is a frequent etiological agent of wound infections, exhibiting high level of resistance to conventional antibiotics.

AIM OF THE STUDY

To determine the effect of selected bile acid sodium salts and their 3-dehydro (i.e. 3-oxo) derivatives, as well as their combinations with commercial antibiotics against A. baumanniia, to confirm bile ethnopharmacological application in wound healing from aspect of microbiology.

MATERIALS AND METHODS

The sensitivity of reference and multidrug resistant (MDR) A. baumannii strains to bile salts, their derivatives and conventional antibiotics were examined by a microtiter plate method. The interaction of bile salts/derivatives and antibiotics was examined by a checkerboard method and time kill curve method. The interaction of bile salts with ciprofloxacin in terms of micelles formation was examined by DOSY NMR technique.

RESULTS

The bile salts sodium deoxycholate (Na-DCA) and sodium chenodeoxycholate (Na-CDCA), as well as their derivatives sodium 3-dehydro-deoxycholate (Na-3DH-DCA) and sodium 3-dehydro-chenodeoxycholate (Na-3DH-CDCA), potentiate antibiotic activity and resensitize A. baumannii. The bile salts and their derivatives enhance A. baumannii sensitivity to antibiotics, particularly those that should penetrate cell to exhibit activity. The sodium salts of bile acid derivatives, namely Na-3DH-DCA and Na-3DH-CDCA, showed synergy against both reference and MDR strain in combination with ciprofloxacin or gentamicin, while synergy with gentamicin was obtained in all combinations, regardless of bile salt type and bacterial strains. The synergy with Na-3DH-CDCA was further confirmed by the time-kill curve method, as bacterial number decreased after 12 h. NMR experiment revealed that this bile salt derivative and ciprofloxacin form co-aggregates when bile salts concentration was higher than critical micelle concentrations (CMC), which indicate the possibility that bile salts enhance ciprofloxacin cell penetration by membrane destabilization, contributing to the synergy.

CONCLUSION

The synergistic interactions between bile salts or derivatives with ciprofloxacin and particularly gentamicin represent a promising strategy for the treatment of A. baumannii wound infections.

Sequence-selective DNA recognition and enhanced cellular up-take by peptide-steroid conjugates

Several GCN4 bZIP TF models have previously been designed and synthesized. However, the synthetic routes towards these constructs are typically tedious and difficult. We here describe the substitution of the Leucine zipper domain of the protein by a deoxycholic acid derivative appending the two GCN4 binding region peptides through an optimized double azide-alkyne cycloaddition click reaction. In addition to achieving sequence specific dsDNA binding, we have investigated the potential of these compounds to enter cells. Confocal microscopy and flow cytometry show the beneficial influence of the steroid on cell uptake. This unique synthetic model of the bZIP TF thus combines sequence specific dsDNA binding properties with enhanced cell-uptake. Given the unique properties of deoxycholic acid and the convergent nature of the synthesis, we believe this work represents a key achievement in the field of TF mimicry.

Biocompatible hydrogelators based on bile acid ethyl amides

Four novel bile acid ethyl amides were synthetized using a well-known method. All the four compounds were characterized by IR, SEM, and X-ray crystal analyses. In addition, the cytotoxicity of the compounds was tested. Two of the prepared compounds formed organogels. Lithocholic acid derivative 1 formed hydrogels as 1% and 2% (w/v) in four different aqueous solutions. This is very intriguing regarding possible uses in biomedicine.

Optically Active Porous Microspheres Consisting of Helical Substituted Polyacetylene Prepared by Precipitation Polymerization without Porogen and the Application in Enantioselective Crystallization

A novel chiral acetylenic monomer derived from cholic acid was synthesized and structurally characterized. The monomer underwent precipitation polymerization in tetrahydrofuran/n-heptane mixed solvent with [Rh(nbd)Cl]₂ as catalyst. Without adding porogen, porous microspheres were successfully prepared in a high yield (>80 wt %). The formation mechanism of the porous structure was proposed. Circular dichroism and UV-vis absorption spectra demonstrated that the porous microspheres possessed optical activity. The optical activity was originated in the chiral helical conformations of substituted polyacetylene forming the microspheres. The porous microspheres were further used as specific chiral additive to induce enantioselective crystallization of racemic BOC-alanine, in which BOC-l-alanine was preferentially induced forming rod-like crystals with e.e. of 69%. This strongly indicates the significant potential applications of the porous microspheres in chiral technologies. The present study also provides a new approach to prepare chiral porous polymer microspheres.

The SLC10 carrier family: transport functions and molecular structure

The SLC10 family represents seven genes containing 1-12 exons that encode proteins in humans with sequence lengths of 348-477 amino acids. Although termed solute carriers (SLCs), only three out of seven (i.e. SLC10A1, SLC10A2, and SLC10A6) show sodium-dependent uptake of organic substrates across the cell membrane. These include the uptake of bile salts, sulfated steroids, sulfated thyroidal hormones, and certain statin drugs by SLC10A1 (Na(+)-taurocholate cotransporting polypeptide (NTCP)), the uptake of bile salts by SLC10A2 (apical sodium-dependent bile acid transporter (ASBT)), and uptake of sulfated steroids and sulfated taurolithocholate by SLC10A6 (sodium-dependent organic anion transporter (SOAT)). The other members of the family are orphan carriers not all localized in the cell membrane. The name "bile acid transporter family" arose because the first two SLC10 members (NTCP and ASBT) are carriers for bile salts that establish their enterohepatic circulation. In recent years, information has been obtained on their 2D and 3D membrane topology, structure-transport relationships, and on the ligand and sodium-binding sites. For SLC10A2, the putative 3D morphology was deduced from the crystal structure of a bacterial SLC10A2 analog, ASBT(NM). This information was used in this chapter to calculate the putative 3D structure of NTCP. This review provides first an introduction to recent knowledge about bile acid synthesis and newly found bile acid hormonal functions, and then describes step-by-step each individual member of the family in terms of expression, localization, substrate pattern, as well as protein topology with emphasis on the three functional SLC10 carrier members.

Approaches for enhancing oral bioavailability of peptides and proteins

Oral delivery of peptide and protein drugs faces immense challenge partially due to the gastrointestinal (GI) environment. In spite of considerable efforts by industrial and academic laboratories, no major breakthrough in the effective oral delivery of polypeptides and proteins has been accomplished. Upon oral administration, gastrointestinal epithelium acts as a physical and biochemical barrier for absorption of proteins resulting in low bioavailability (typically less than 1-2%). An ideal oral drug delivery system should be capable of (a) maintaining the integrity of protein molecules until it reaches the site of absorption, (b) releasing the drug at the target absorption site, where the delivery system appends to that site by virtue of specific interaction, and (c) retaining inside the gastrointestinal tract irrespective of its transitory constraints. Various technologies have been explored to overcome the problems associated with the oral delivery of macromolecules such as insulin, gonadotropin-releasing hormones, calcitonin, human growth factor, vaccines, enkephalins, and interferons, all of which met with limited success. This review article intends to summarize the physiological barriers to oral delivery of peptides and proteins and novel pharmaceutical approaches to circumvent these barriers and enhance oral bioavailability of these macromolecules.

Structural requirements of bile acid transporters: C-3 and C-7 modifications of steroidal hydroxyl groups

The apical sodium dependent bile acid transporter (ASBT) and sodium-taurocholate cotransporting polypeptide (NTCP) are potential prodrug targets, but the structural requirements for these transporters are incompletely defined. The objective of this study was to evaluate the effect of C-3 and C-7 substitution on bile acid interaction with these bile acid transporters. Nineteen bile acid analogs were tested against ASBT and NTCP for binding, as well as translocation. Results indicated that ASBT and NTCP accommodated a wide range of substituents for binding, but all major C-7 modifications resulted in analogs that did not demonstrate active uptake by either ASBT or NTCP. A C-3 modification that was not tolerated at C-7 still afforded translocation via ASBT and NTCP, confirming the relative unacceptability of C-7 modification. Both ASBT and NTCP demonstrated a generally similar binding potency. Results suggest that drug conjugation to the C-3 hydroxyl group, rather than C-7, has potential to lead to a successful prodrug targeting ASBT and NTCP.

Transporters, Trojan horses and therapeutics: suitability of bile acid and peptide transporters for drug delivery

Membrane transporters are major determinants for the pharmacokinetic, safety and efficacy behavior of drugs. Available technologies to study function and structure of transport proteins has strongly stimulated research in transporter biology and uncovered their importance for the drug discovery and development process, especially for drug absorption and disposition. Physiological transport systems are investigated as potential ferries to improve drug absorption and membrane permeation and to achieve organ-specific drug action. In particular, the bile acid transport systems in the liver and the small intestine and the oligopeptide transporters are of significant importance for molecular drug delivery.

Synthesis of a novel polymer bile salts-(polyethylene glycol)2000-bile salts and its application to the liver-selective targeting of liposomal DDB

PURPOSE

The objective of this study was to achieve a sustained and targeted delivery of liposome to the liver, by modifying the phospholipid [phosphatidylcholine (PC)/cholesterol (10 : 1) liposomes with a novel polymer bile salts-(polyethylene glycol)(2000)-bile salts (BP(2)B).

METHODS

First, we generated a novel BP(2)B by N,N'-dicyclohexylcarbodiimide/4-dimethylaminopyridine esterification method and confirmed by Fourier transform infraredand (1) H-NMR spectra. Second, we prepared the BP(2)B-modified liposomes (BP(2)BL) that included BP(2)B, and the effect of the weight ratios of BP(2)B/PC on entrapment efficiency was investigated and BP(2)B/PC = 3% (w/w) was determined as the optimum ratio for the 4,4'-dimethoxy-5,6,5',6'-bi (methylenedioxy)-2,2'-bicarbomethoxybiphenyl liposomes. And then, the ability of the liver target of BP(2)BL was studied by calculating the targeted parameters.

RESULTS AND DISCUSSION

All the results revealed that the introduction of polyoxyethylene chains could control interactions of bile salt moieties on liposome surfaces with the receptor compared with traditional liposomes (CL), marking BP(2)BL as a suitable carrier for hepatic parenchymal cell-specific and sustained targeting. It was suggested that liposomes containing such novel BP(2)B have great potential as drug delivery carriers for the liver-selective targeting that has targeted and sustained drug delivery.

New dental composites containing multimethacrylate derivatives of bile acids: a comparative study with commercial monomers

We have prepared multifunctional methacrylate derivatives of bile acids as cross-linkable monomers for use in dental composites. By modifying the chemical structure of the monomers, we were able to vary the viscosity, hydrophobicity, and reactivity and have studied the effect of these parameters on the conversion of the monomers, the shrinkage during polymerization, and the mechanical properties of the resulting polymers and composites. Materials containing these new monomers generally had physical, thermal, and mechanical properties comparable to those containing the commonly used dental monomers BisGMA or UDMA and had lower polymerization shrinkage. The multimethacrylate derivatives of cholic acid, which are known to be less cytotoxic than BisGMA and UDMA, are shown to be promising materials for dental applications.

Validation of a solid-phase-bound steroid scaffold for the synthesis of novel cyclic peptidosteroids

The current article reports on the synthesis of a new type of cyclic peptidosteroid, in which a bile-acid-based scaffold was used for the conformational restriction of a loop-like peptide. Convergent coupling of two tetrapeptides to the non-peptidic steroidal entity was carried out once in the classical C-to-N and once in the non-classical N-to-C direction. Peptide backbone cyclisation was then carried out, giving rise to a ring size equivalent to approximately 12 amino acids. This type of construct will be used in the development of a peptide vaccine against measles.

Liphophilic complexation of heparin based on bile acid for oral delivery

Oral delivery of heparin will offer great advantages over injectable heparin therapy in the treatment of patients with deep vein thrombosis. Since heparin absorption in the intestine is restricted due to its physicochemical properties, we designed a bile acid derivative, cationic deoxycholylethylamine (DCEA), to be complexed with anionic low molecular weight heparin (LMWH). Complexation between LMWH and DCEA was saturated above 1:10 molar ratio and improved lipophilicity of LMWH. The LMWH/DCEA complex was completely solubilized in 80% propylene glycol solution. The oral absorption of LMWH in rats was proportional to the molar ratio of DCEA and the administered dose of complex. The C(max) values to the complex molar ratios of 1:0, 1:3, 1:5 and 1:10 were about 0.07, 0.27, 0.83, and 0.47 IU/ml, respectively, and the C(max) values to the doses of 10, 25, 50 mg/kg were 0.16, 0.44, and 0.83 IU/ml, respectively. The LMWH/DCEA complex was found to be absorbable through all regions of the small intestine of rats without causing tissue damage. This study demonstrates the feasibility of oral heparin delivery using the cationic DCEA for chronic administration in clinical trials as an effective therapy.

Absorption study of deoxycholic acid-heparin conjugate as a new form of oral anti-coagulant

The oral delivery of macromolecules is a topic of much interest as this would undoubtedly improve patient acceptance and compliance with chronic regimens. Heparin and insulin are perhaps among the first candidates that should be considered for oral macromolecule delivery systems. Heparin is the most potent anti-coagulant known for the prevention of deep vein thrombosis and pulmonary embolism, and an orally active heparin would undoubtedly effectively reduce chronic thrombotic events. Here, we report on the development of an orally administrable chemical conjugate of heparin and hydrophobic deoxycholic acid (DOCA), which we refer to as LHD. LHD was pre-formulated with dimethyl sulfoxide (DMSO) as solubilizer to further improve its oral bioavailability (9.1% in monkey). LHD was found to be absorbed mainly in the jejunum and ileum of the small intestine, although it is in the ileum that the absorption is most notable. From the mechanism studies of LHD absorption using Caco-2 cell monolayers for mimicking the intestine, we found that LHD highly permeated by passive diffusion through the transcellular route and its permeation was partially affected by bile acid transporters. This study demonstrates the feasibility of chemically modified heparin for long-term oral administration as an effective therapy for venous thromboembolism in clinical trials.

Efficacy of orally active chemical conjugate of low molecular weight heparin and deoxycholic acid in rats, mice and monkeys

Deoxycholic acid (DOCA) is a bile acid that facilitates the gastrointestinal (GI) absorption of low molecular weight heparin (LMWH) by bonding chemically to it. The calculated coupling ratio and bioactivity of LMWH-DOCA was 3.6 and 126.8 IU/mg, respectively. This study examined the efficacy of orally administered LMWH-DOCA in rat, mouse and monkey models. When 100 mg/kg (12,680 IU/kg) of LMWH-DOCA was administered to rats or mice, its maximum anti-factor Xa activity was 0.76+/-0.15 and 0.15+/-0.03 IU/ml, respectively. On the other hand, when a single dose of 100 mg/kg LMWH-DOCA mixed with either a bile solution or 200 mg/kg free DOCA was administered to mice, the anti-factor Xa activity of LMWH-DOCA was 0.42-0.45 IU/ml. Fluorescence studies confirmed that the free bile acid induced the morphological change in LMWH-DOCA in the buffer solution. In the monkey experiments, the bioavailability of LMWH-DOCA after administering 200 mg/kg free DOCA orally was 6.8%, which was 8 times higher than that of LMWH (0.8%) and 4 times higher than that of LMWH-DOCA in the absence of free DOCA (1.7%). The absorption of orally administered LMWH-DOCA occurred in all parts of the small intestine, particularly in the ileum without causing any damage such as fusion of the microvilli and dissolution or disorientation of the cell layers. The optimum oral formulation for LMWH-DOCA delivery in each animal model was determined according to the different absorption behavior of LMWH-DOCA.

Synthesis of phospholipid-conjugated bile salts and interaction of bile salt-coated liposomes with cultured hepatocytes

To examine the possibility of targeting liposomes to hepatocytes via bile salts, the bile salt lithocholyltaurine was covalently linked to a phospholipid. The isomeric compounds disodium 3alpha-(2-(1,2-O-distearoyl-sn-glycero-3-phospho-2'-ethanolamidosuccinyloxy)ethoxy)-5beta-cholan-24-oyl-2'-aminoethansulfonate and disodium 3beta-(2-(1,2-O-distearoyl-sn-glycero-3-phospho-2'-ethanolamidosuccinyloxy)ethoxy-5beta-cholan-24-oyl-2'-aminoethansulfonate (DSPE-3beta-LCT) were synthesized and incorporated into liposomal membranes. Confocal laser scanning microscopy studies showed that bile salt-bearing liposomes (BSLs) attach to the surface of rat hepatocytes in culture. Studies with radioactively labeled liposomes revealed that the bile salt linked via the 3beta-conformation resulted in a higher attachment efficiency than that with the 3alpha-derivative. In the presence of BSLs corresponding to 2 mM liposomal phosphatidylcholine, uptake of 50 microM cholyltaurine (CT) into hepatocytes was reduced by approximately 40% by the 3beta-derivative and by approximately 17% by the 3alpha-derivative. When added simultaneously with the liposomes, CT up to 75 microM inhibited the binding of DSPE-3beta-LCT-bearing liposomes. By contrast, increasing concentrations reversed this inhibition and resulted in an increased bile salt-mediated binding. The same was true when CT was added 10 min before the liposomes were added. The attachment of BSLs to the surface of hepatocytes opens up promising possibilities for hepatocyte-specific drug delivery. More generally, not only substrates for cellular endocytosing receptors but also substrates for cellular carrier proteins should be suitable ligands for the cell-specific targeting of nanoscale particles such as liposomes.

Increased acyclovir oral bioavailability via a bile acid conjugate

The objective of this work was to design an acyclovir prodrug that would utilize the human apical sodium-dependent bile acid transporter (hASBT) and enhance acyclovir oral bioavailability. Using each chenodeoxycholate, deoxycholate, cholate, and ursodeoxycholate, four bile acid prodrugs of acyclovir were synthesized, where acyclovir was conjugated to a bile acid via a valine linker. The affinity of the prodrug for hASBT was determined through inhibition of taurocholate uptake by COS-7 cells transfected with hASBT (hASBT-COS). The prodrug with the highest inhibitory affinity was further evaluated in vitro and in vivo. The prodrug acyclovir valylchenodeoxycholate yielded the highest affinity for hASBT (Ki = 35 microM), showing that chenodeoxycholate is the free bile acid with the greatest affinity for hASBT. Acyclovir valylchenodeoxycholate's affinity was similar to that of cholic acid (Ki = 25 microM). Further characterization showed that acyclovir was catalytically liberated from acyclovir valylchenode-oxycholate by esterase. Relative to cellular uptake studies of acyclovir alone, the cellular uptake from the prodrug resulted in a 16-fold greater acyclovir accumulation within hASBT-COS cells, indicating enhanced permeation properties of the prodrug. Enhanced permeability was due to hASBT-mediated uptake and increased passive permeability. The extent of acyclovir uptake in the presence of sodium was 1.4-fold greater than the extent of passive prodrug uptake in the absence of sodium (p = 0.02), indicating translocation of the prodrug by hASBT. The prodrug also exhibited an almost 12-fold enhanced passive permeability, relative to acyclovir's passive permeability. Oral administration of acyclovir valylchenodeoxycholate to rats resulted in a 2-fold increase in the bioavailability of acyclovir, compared to the bioavailability after administration of acyclovir alone. Results indicate that a bile acid prodrug strategy may be useful in improving the oral bioavailability of intestinal permeability-limited compounds.

Conjugates of Gadolinium Complexes to Bile Acids as Hepatocyte-Directed Contrast Agents for Magnetic Resonance Imaging

A series of structurally different Gd(III) conjugates incorporating a bile acid moiety have been prepared. Polyaminopolycarboxylic ligands such as diethylenetriaminepentaacetic acid (DTPA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid (DOTA) have been selected as chelating subunit for the Gd(III) ion. Cholic acid, cholylglycine, and cholyltaurine have been incorporated as the bile acid moieties. In first generation conjugates the Gd(III) complex is linked to the carboxyl group of cholic acid. Second generation conjugates feature the attachment of the Gd(III) complex to the 3 position of the steroidic backbone of the bile acid. Finally, in third generation conjugates the Gd(III) complex is attached to the epsilon nitrogen atom of cholyllysine. The conjugates are eliminated through the biliary route to a various extent (7.5 to 77% in rats) according to their structural features. Among the most promising terms, a second generation conjugate in which the Gd(III) complex is linked to cholic acid through the 3alpha hydroxy group seems to enter hepatocytes using the Na(+)/taurocholate transporter. Noticeably, some of the second generation conjugates are characterized by very high tolerabilities (LD(50) up to 9.5 mmol/kg) after intravenous administration in mice.

[Improvement of transmucosal absorption of biologically active peptide drugs]

Peptide and protein drugs are becoming a very important class of therapeutic agents. However, the oral bioavailability of peptide and protein drugs is generally poor because they are extensively degraded by proteases in the gastrointestinal tract or impermeable through the intestinal mucosa. For the systemic delivery of the peptide and protein drugs, parenteral administration is currently required to achieve their therapeutic activities. However, this administration is poorly accepted by patients and may cause allergic reactions and serious side effects. Therefore, various approaches have been examined to overcome the delivery problems of these peptides when they are administered into the gastrointestinal tract and other mucosal sites. These approaches include (1) to use additives such as absorption enhancers and protease inhibitors, (2) to develop an administration method for peptides that can serve as an alternative to oral and injection administration, (3) to modify the molecular structure of peptide and protein drugs to produce prodrugs and analogues, and (4) to use the dosage forms to these peptide drugs. In this study, we demonstrated that the transmucosal absorption of various peptides including insulin, calcitonin, tetragastrin and thyrotropin releasing hormone (TRH) could be improved by the use of these approaches. Therefore, these approaches may give us basic information to improve the transmucosal absorption of peptide and protein drugs.

Hepatobiliary transport of bile acid amino acid, bile acid peptide, and bile acid oligonucleotide conjugates in rats

Uptake of drugs by bile acid carriers could account for the selectivity of drug actions in the gut and liver. We have previously shown that conjugation of xenobiotics with bile acids facilitates their transfer to hepatocytes and ileal enterocytes. In this study L-alanine and 2 biooligomers, the tetrapeptide L-(ala)(4) and a 15 mer oligodeoxynucleotide (ODN) were coupled covalently via linker molecules to the 3-position of bile acids. The L-alanine-coupled bile acid conjugates were rapidly taken up by the liver and efficiently eliminated into bile. These compounds mimicked hepatic transport of bile acids. Also in case of the tetrapeptide (ala)(4), bile acid conjugation significantly improved hepatic and intestinal cell uptake and rendered the peptide conjugate resistant to peptidases. Because uptake by isolated hepatocytes was not dependent on sodium ions and was blocked by ochratoxin A, we assume basolateral transport by an oatp-type bile acid carrier. In the case of the 15 mer ODN, normal and bile acid-conjugated oligodeoxynucleotide appeared intact in bile but without marked improvement of hepatocellular uptake and biliary elimination. We conclude that bile acids can deliver small peptides to gut and parenchymal liver cells via bile acid transport pathways, whereas in the case of oligonucleotides an attached bile acid was not sufficient to shuttle them successfully into hepatocytes.

Preparation of alginate gel beads containing chitosan nicotinic acid salt and the functions

Calcium-induced alginate gel beads containing chitosan salt (Alg-CS) was prepared using nicotinic acid (NA), a drug for hyperlipidemia, and investigated its two functions in gastrointestinal tract, (a) NA release from Alg-CS, (b) uptake of bile acids into Alg-CS. The amount of NA incorporated in Alg-CS increased according to increment of CS content. NA was rapidly released from Alg-CS in diluted HCl solution (pH 1.2) or physiological saline without disintegration of the beads. When Alg-CS was placed in bile acid solution it took bile acid into itself. About 80% of taurocholic acid dissolved in the medium was taken into Alg-CS. According to increment of bile acid concentration, the uptake amount increased and an approximately linear relationship existed among them.