Thiomer nanoparticles: stabilization via covalent cross-linking.

The purpose of this study was the development of stable thiomer nanoparticles for mucosal drug delivery. Chitosan-thioglycolic acid (chitosan-TGA) nanoparticles (NP) were formed via ionic gelation with tripolyphosphate (TPP). In order to stabilize the NP inter- and intra-molecular disulfide bonds were formed via controlled oxidation with hydrogen peroxide (H2O2). Thereafter, stability was investigated in saline and simulated body fluids at pH 2 and pH 5.5 via optical density measurements. The mucoadhesive properties were evaluated in vitro on freshly excised porcine intestinal mucosa via the rotating cylinder method. Particles had a mean size of 158 ± 8 nm and a zeta potential of ~ + 16 mV. Three different degrees of oxidation were adjusted by the addition of H2O2 in final concentrations of 10.60 µmol (chitosan-TGA (ox1)), 21.21 µmol (chitosan-TGA (ox2)), and 31.81 µmol (chitosan-TGA (ox3)) leading to 60%, 75%, and 83% of oxidized thiol groups, respectively. More than 99% of chitosan-TGA (ox3) NP, 70% of chitosan-TGA (ox2) NP, and 50% of chitosan-TGA (ox1) NP were stable over a 60-min period in simulated gastric fluid. In contrast, only 10% of unmodified chitosan and chitosan-TGA NP which were just ionically cross-linked remained stable in the same experiment. The adhesion times of covalently cross-linked chitosan-TGA (ox1), chitosan-TGA (ox2), and chitosan-TGA (ox3) were ~ 41-fold, 31-fold, and 25-fold longer in comparison to unmodified ionically cross-linked chitosan. The method described here might be useful for the preparation of stable nanoparticulate drug delivery systems.

Development of a mucoadhesive nanoparticulate drug delivery system for a targeted drug release in the bladder.

PURPOSE: Purpose of the present study was the development of a mucoadhesive nanoparticulate drug delivery system for local use in intravesical therapy of interstitial cystitis, since only a small fraction of drug actually reaches the affected site by conventional treatment of bladder diseases via systemic administration. METHODS: Chitosan-thioglycolic acid (chitosan-TGA) nanoparticles (NP) and unmodified chitosan NP were formed via ionic gelation with tripolyphosphate (TPP). Trimethoprim (TMP) was incorporated during the preparation process of NP. Thereafter, the mucoadhesive properties of NP were determined in porcine urinary bladders and the release of TMP among simulated conditions with artificial urine was evaluated. RESULTS: The particles size ranged from 183nm to 266nm with a positive zeta potential of +7 to +13mV. Under optimized conditions the encapsulation efficiency of TMP was 37%. The adhesion of prehydrated chitosan-TGA NP on the urinary bladder mucosa under continuous urine voiding was 14-fold higher in comparison to unmodified chitosan NP. Release studies indicated a more sustained TMP release from covalently cross linked particles in comparison to unmodified chitosan-TPP NP over a period of 3h in artificial urine at 37°C. CONCLUSION: Utilizing the method described here, chitosan-TGA NP might be a useful tool for local intravesical drug delivery in the urinary bladder.

Distribution of thiolated mucoadhesive nanoparticles on intestinal mucosa.

It was the aim of the present study to evaluate and compare the distribution of thiolated mucoadhesive anionic poly(acrylic acid) (PAA) and cationic chitosan (CS) nanoparticles on intestinal mucosa. Modifications of these polymers were achieved by conjugation with cysteine (PAA-Cys) and 2-iminothiolane (CS-TBA). Nanoparticles (NP) were prepared by ionic gelation and labelled with the strong hydrophilic fluorescent dye Alexa Fluor 488 (AF 488) and hydrophobic fluorescein diacetate (FDA). Unmodified and modified CS and PAA NP were examined in vitro in terms of their mucoadhesive and mucus penetrating properties on the mucosa of rat small intestine. To investigate the transport of NP across the mucus layer, their diffusion behaviour through natural porcine intestinal mucus was studied through a new diffusion method developed by our group. Lyophilised particles displayed 526 µmol/g (CS) and 513 µmol/g (PAA) of free thiol groups and a zeta potential of 20 mV (CS) and -14 mV for PAA NP. Nanoparticle distribution on rat intestine suggested that mucoadhesion of thiolated NP is higher than the diffusion into the intestinal mucosa. Modified particles displayed more than a 6-fold increase in mucoadhesion compared to unmodified ones. The rank order with regard to mucoadhesion of all particles was: CS-TBA>PAA-Cys>CS>PAA, whereas CS-TBA showed 2-fold higher mucoadhesive properties compared to PAA-Cys NP. Diffusion through intestinal mucus was much higher for unmodified than for thiolated as well as for anionic compared to cationic particles. Overall, it was shown that thiolated particles of both anionic and cationic polymers have improved mucoadhesive properties and could be promising carriers for mucosal drug delivery.

Synthesis and in vitro characterization of a novel PAA-ATP conjugate.

The objective of this study was to improve the multifunctional properties of poly(acrylic acid) (PAA) by covalent attachment of 4-aminothiophenol (ATP) to its backbone. The permeation enhancing effect of PAA-ATP together with glutathione was evaluated in Ussing-type chambers using fluorescein isothiocyanate dextran as model compound. The mucoadhesive properties were evaluated in vitro on freshly excised porcine intestinal mucosa through the rotating cylinder method. The resulting conjugates PAA-ATP1 and PAA-ATP2 displayed 168 ± 35 and 426 ± 55 µmol immobilized free thiol groups per gram polymer, respectively. In addition, 279 ± 28 and 139 ± 22 µmol disulfide bonds per gram polymer, respectively, were identified on PAA-ATP1 and PAA-ATP2. Within disintegration studies in aqueous buffer solution, the modified polymers showed improved cohesive properties. Because of the immobilization of ATP, the swelling of PAA-ATP1 and PAA-ATP2 improved 12.0- and 17.8-fold, respectively. The adhesion times of the conjugates PAA-ATP1 and PAA-ATP2 were more than 20- and 30-fold increased in comparison to unmodified PAA. Furthermore, conjugates PAA-ATP1 and PAA-ATP2 exhibited a 1.86- and 2.07-fold higher permeation enhancing effect, respectively, over unmodified PAA. According to these results, PAA-ATP conjugates represent a very promising novel type of thiomer for the development of various mucoadhesive drug delivery systems.

Permeation studies on freshly excised rat gastric mucosa: influence of pH.

The objective of this study was to evaluate the influence of pH on the permeation of model drugs through freshly excised rat stomach. Additionally, the capability of excised gastric mucosa to maintain an acidic pH was assessed. In vitro permeation studies were performed in Ussing-type diffusion chambers with rat stomach using fluorescence-labeled bacitracin (bac-FITC), sodium fluorescein (NaFlu), propranolol HCl, and cimetidine as model drugs. The pH was adjusted to pH 1, 2, and 6.8 in the donor chamber and pH 7.4 in the acceptor chamber. The study demonstrated that both, the fore stomach and the glandular gastric mucosa, are capable of maintaining an acidic pH of 1-1.2 in the donor chamber. P(app) (permeation coefficients) were found to be 1.4 ± 0.6 ×·10(-7) and 7.6 ± 0.7 ×·10(-7) for bac-FITC and 3.3 ± 1.5 ×·10(-7) and 2.4 ± 0.6 ×·10(-6) cm/sec for NaFlu at pH 2 and 6.8, respectively, in the glandular stomach. In order to evaluate the effect of pH on the integrity of paracellular space, propranolol as high-permeability drug and cimetidine as low-permeability drug were chosen. The P(app) of propranolol HCl was determined to be 5.9 ± 0.3 ×·10(-7) and 1.1 ± 0.7 ×·10(-6) cm/sec at pH 2 and 6.8, respectively, in the glandular stomach. Cimetidine showed a permeability of 1.4 ± 0.4 ×·10(-5) and 9.6 ± 2.3 ×·10(-6) cm/sec at pH 2 and 6.8. Results provide essential basic information for the development of gastric drug delivery systems.

The impact of vehicles on the mucoadhesive properties of orally administrated nanoparticles: a case study with chitosan-4-thiobutylamidine conjugate.

The aim of this study was to evaluate the impact of various vehicles on mucoadhesive properties of thiolated chitosan nanoparticles both in vitro and in vivo. Nanoparticles (NPs) were prepared by in situ gelation technique followed by labeling with fluorescein diacetate. Comparative studies on mucoadhesion were done with these thiolated chitosan NPs and unmodified chitosan NPs (control). The obtained nanoparticles displayed a mean diameter of 164.2 ± 6.9 nm and a zeta potential of 21.5 ± 5 mV. In an in vitro adhesion study, unhydrated thiolated NPs adhered strongly to freshly excised porcine small intestine, which was more than threefold increase compared to the control. In contrast, in the presence of various vehicles (PEG 300, miglyol 840, PEG 6000, cremophor EL, and caprylic triglyceride), the mucoadhesive properties of thiolated NPs were comparatively weak. Thiolated NPs suspended in caprylic triglyceride, for example, had a percent mucoadhesion of 22.50 ± 5.35% on the mucosa. Furthermore, results from in vivo mucoadhesion studies revealed that the dry form of nanoparticles exhibits the strongest mucoadhesion, followed by nanoparticles suspended in PEG 300, miglyol, and 100 mM phosphate buffer, in that order. Three hours after administration, the gastrointestinal residence time of the dry form of thiolated NPs was up to 3.6-fold prolonged. These findings should contribute to the design of highly effective oral mucoadhesive nanoparticulate drug delivery systems.

Design and in vitro evaluation of a novel polymeric P-glycoprotein (P-gp) inhibitor.

The aim of the present study was to improve the inhibitory properties of poly(ethylene glycol) (PEG) as excipient in drug delivery systems by covalent attachment of thiol moieties. This was achieved by grafting PEG to polyethylenimine (PEI) and finally thiolation with γ-thiobutyrolatone. Furthermore, the potential of this novel thiolated PEG-g-PEI co-polymer on the transport of rhodamine-123 (Rho-123) as P-gp substrate across freshly excised rat intestinal mucosa was evaluated in Ussing-type chambers. Apparent permeability coefficients (P(app)) were calculated and compared with values gained from experiments with the well-established P-gp inhibitors verapamil, reduced GSH, 6-mercatopurine and vitamin E-TPGS and the structurally similar compounds, myrj 52 and brij 35. The thiolated co-polymer displayed 145.07 ± 1.64 µmol/g of remaining primary amino groups, 84.30 ± 5.43 µmol/g of immobilized thiol groups and 12.74 ± 1.57 µmol/g of disulfide bonds. The approximate molecular mass of the thiolated co-polymer was 16,000 Da. The (1)H-NMR spectrum of PEG-g-PEI co-polymer was characterized by the presence of signal groups of PEG, hexamethylene diisocyanate (HMDI) and PEI substructures. Studies with Caco-2 cells revealed that the thiolated co-polymer shows 6.69 ± 0.27% of cytotoxicity by LDH assay and 93.33 ± 0.07% of cell viability by MTT assay. The thiolated co-polymer in a concentration of 0.5% (w/v) displayed a more pronounced effect on the absorptive transport of Rho-123 (P(app)=15.2 ± 1.0 × 10(-)(6)cm/s) in comparison to reduced GSH, 6-mercatopurine, vitamin E-TPGS, myrj 52 and brij 35. The thiolated co-polymer increased the transport of Rho-123 up to 3.3-fold in comparison to Rho-123 without any inhibitor used as control (P(app)=4.7 ± 0.1 × 10(-)(6)cm/s). The thiolated co-polymer applied in a concentration of 0.1%, 0.25% and 0. 5% (w/v) did not only enhance the absorption but also decreased the secretory transport of Rho-123 resulting in efflux ratios (secretory P(app)/absorptive P(app)) of 1.0, 1.4 and 2.0, respectively. Because of these features the novel thiolated PEG-g-PEI co-polymer seems to exhibit promising properties as novel P-gp inhibitor.

Mucoadhesive drug delivery systems.

The uptake of drugs is often limited by the short contact time between the formulation and the absorption membrane and by a fast washout. Using mucoadhesive polymers, however, the residence time of the dosage form on the mucosa can be significantly increased. In this chapter the composition of the mucus, the different mucoadhesion theories and binding types between mucus and mucoadhesives, mucoadhesion tests and factors influencing mucoadhesion are introduced. Various mucoadhesive polymers are also described and an overview of various mucoadhesive delivery systems is provided.

Hydrophobic thiolation of pectin with 4-aminothiophenol: synthesis and in vitro characterization.

The aim of this study was to modify pectin by covalent attachment of the water-insoluble ligand 4-aminothiophenol to its polymeric backbone. 4-Aminothiophenol is a ligand which is highly prone to oxidation. Therefore, this ligand allows oxidative cross-linking of pectin under mild oxidative conditions. Additionally, hydrophobization of pectin can be achieved by the mentioned modification which offers certain advantages over highly hydrophilic native pectins. 4-Aminothiophenol was covalently attached to pectin via amide bond formation between carboxylic moieties of pectin and the amino-group of 4-aminothiophenol. Two different pectin-4-aminothiophenol conjugates were synthesized and investigated regarding the amount of coupled ligand, rheological behavior under oxidative conditions, swelling behavior, and cytotoxic effects. Within this study, 557.3 +/- 49.0 and 158.8 +/- 23.1 micromol 4-aminothiophenol have been coupled per gram pectin. Within both conjugates, around 75% of the bound ligand appeared in its reduced form. Within rheological studies, a 500-fold increase in viscosity was achieved by addition of hydrogen peroxide as an oxidizing agent. Investigations on the swelling behavior revealed that this hydrophobic modification of pectin results in decelerated water uptake on the one hand and improved cohesive properties after oxidation of thiol groups to disulfide bonds on the other hand. Thereby, the maximum amount of water which can be uptaken by pectin matrices could be increased. According to these results, Pec-ATP conjugates could be valuable tools for several pharmaceutical applications due to the established method of gelation and the altered swelling and disintegration behavior.

In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of oxidizing agents.

The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four oxidizing agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol-gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053+/-44 micromol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any oxidizing agents became gel within 40 min. In contrast, when the oxidizing agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/oxidizing agent systems assessed by MTT assay was 70-85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p<0.05) raising compared to the negative control. According to these results, chitosan-TGA/oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.

Chitosan solutions and particles: evaluation of their permeation enhancing potential on MDCK cells used as blood brain barrier model.

It was the aim of the present study to investigate the potential of chitosan of different molecular weight in solution and as particles to enhance the transport into the brain. FITC-dextran 4 (FD4) transport with and without chitosans of different molecular weight across MDCK cell monolayers, a model for the blood brain barrier, was compared. In the following particles of chitosan exhibiting the most appropriate molecular weight were prepared and their particle size and stability were evaluated. Furthermore permeation studies, MDCK cell toxicity test and red blood cell lysis test were performed. The rank order for chitosan for permeation enhancement across MDCK cells was determined to be 20 kDa~150 kDa > 400 kDa~600 kDa. Moreover particles showed a higher permeation enhancement than the corresponding solution and the smaller the particles were the higher the permeation of FD4 was. All particles were stable for 72 h. Particles displayed increased MDCK cell toxicity and red blood cell lysis compared to chitosan in solution. The smaller the particles were, the higher their toxicity was. According to these results chitosan particles are more potent in absorption enhancement than chitosan solutions.

In vivo evaluation of thiolated poly(acrylic acid) as a drug absorption modulator for MRP2 efflux pump substrates.

Recently, several polymers have been reported to modulate drug absorption by inhibition of intestinal efflux pumps such as multidrug resistance proteins (MRPs) and P-glycoprotein (P-gp). The aim of the present study was to evaluate the efficiency of thiolated poly(acrylic acid) (PAA-Cys) to act as a drug absorption modulator for MRP2 efflux pump substrates in vivo, using sulforhodamine 101 as representative MRP2 substrate. In vitro, the permeation-enhancing effect of unmodified PAA and PAA(250)-Cys(,) displaying 580 micromol free thiol groups per gram polymer, was evaluated by using freshly excised rat intestinal mucosa mounted in Ussing-type chambers. In comparison to that of the buffer control, the sulforhodamine 101 transport in the presence of 0.5% unmodified PAA(250) and 0.5% (w/v) PAA(250)-Cys was 1.3- and 4.0-fold improved, respectively. In vivo, sulforhodamine 101 solutions containing 4% (w/v) unmodified PAA(250) or 4% (w/v) thiolated PAA(250) were orally given to rats. The PAA(250)-Cys solution increased the area under the plasma concentration-time curve (AUC(0-12)) of sulforhodamine 101 3.8-fold in comparison to control and 2.2-fold in comparison to unmodified PAA(250). This in vivo study revealed that PAA(250)-Cys significantly increased the oral bioavailability of MRP2 substrate sulforhodamine 101.

In vitro evaluation of natural and methylated cyclodextrins as buccal permeation enhancing system for omeprazole delivery.

In this work the enhancing effect of cyclodextrins on the buccal permeation of a hydrophobic model drug, omeprazole was studied. First, the influence of the complexation with cyclodextrins in the absence and in the presence of an alkali agent, L-arginine, on the drug stability was checked at neutral conditions since omeprazole alone is only stable in basic conditions. In vitro transbuccal permeation of omeprazole non-complexed and complexed with beta- and methyl-beta-cyclodextrin and in presence of L-arginine was examined using freshly obtained porcine buccal mucosa. Tissue viability after incubation with sample solutions was assessed using a MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) biochemical assay and histological evaluation. The toxicity of the sample solutions on buccal mucosa was evaluated by measuring lactate dehydrogenase activity. The present results show that complexation with cyclodextrins increases drug stability at neutral conditions; furthermore, L-arginine contributed to higher drug stability. Permeation studies indicate an increase on drug permeation in complexed form of 1.1- and 1.7-fold for beta-cyclodextrin and methyl-beta-cyclodextrin, respectively. The presence of L-arginine increases drug permeation 1.4-fold in omeprazole complexed with beta-cyclodextrin and 2.4-fold in the inclusion complex formed with methyl-beta-cyclodextrin. The cell viability of the buccal mucosa after a 3 h incubation period, with all sample solutions, remained around 70% and lactate dehydrogenase assay showed that studied cyclodextrins, even in the presence of an alkali agent are not cytotoxic for porcine buccal mucosa. Histological evaluation of the tissue demonstrated that the buccal epithelium remains viable after 3 h of incubation with sample solutions.

Development and in vitro evaluation of a mucoadhesive vaginal delivery system for nystatin.

The purpose of the present study was to design and evaluate a novel vaginal delivery system for nystatin based on mucoadhesive polymers. L-Cysteine and cysteamine, respectively, were covalently attached to poly(acrylic acid), and the two different thiolated polymers were evaluated in vitro regarding their swelling behavior, mucoadhesive properties and release behavior. Tablets comprising these thiolated polymers and nystatin demonstrated a high stability in vaginal fluid simulant pH 4.2 and an increase in weight by swelling whereas control tablets comprising unmodified poly(acrylic acid) disintegrated and dissolved. The mucoadhesion time of tablets on freshly excised bovine vaginal mucosa on a rotating cylinder and the total work of adhesion of gels and tablets increased significantly due to the formation of disulfide bonds between the thiolated polymer and cysteine rich subdomaines of the mucus layer. The drug nystatin was released more slowly out of thiomer tablets and gels than out of PAA control tablets and gels. Therefore these thiolated polymers are promising delivery systems for nystatin providing a prolonged residence time and a sustained drug release in vitro under physiological relevant conditions.

Chitosan-N-acetyl cysteine conjugates: in vitro evaluation of permeation enhancing and P-glycoprotein inhibiting properties.

This study evaluated three chitosan-N-acetyl cysteine (CAC) conjugates of increasing molecular mass as a valuable tool to improve the absorption of drugs by assessing its permeation enhancing effect regarding the active P-gp substrate rhodamine-123 in comparison to the trans- and paracellular marker FD 4 both in rat intestine and Caco 2 monolayers. Additional LDH and MTT cytotoxicity tests have attested a non-toxic profile to CAC, which can consequently be seen as a safe and promising novel drug carrier with the ability to enhance drug absorption and to inhibit P-gp efflux transporters.

Thiolated chitosans: development and in vitro evaluation of an oral tobramycin sulphate delivery system.

The aim of the present study was to develop and evaluate an oral delivery system for tobramycin sulphate intended to improve the oral bioavailability. Chitosan was thiolated by the immobilisation of N-acetylcysteine (NAC) to the amino groups of the polymer. The permeation enhancing effect of the resulting chitosan-NAC conjugate in combination with the permeation mediator glutathione (GSH) was evaluated both in Ussing-type chambers across freshly excised rat intestinal mucosa and Caco-2 cells using the poorly orally absorbed aminoglycoside tobramycin sulphate as model drug. Additionally, the release profile from tablets containing tobramycin sulphate, chitosan-NAC and glutathione was determined. The obtained thiomer chitosan-NAC displayed 962.2+/-53.2 micromol thiol groups per gram polymer of which 35.5+/-5.0% were oxidised. In comparison to buffer only, tobramycin sulphate uptake in presence of 0.5% (w/v) unmodified chitosan, 0.5% (w/v) chitosan-NAC, 0.5% (w/v) glutathione and the combination of 0.5% (w/v) glutathione and 0.5% (w/v) chitosan-NAC was improved 1.2-fold, 1.3-fold, 1.5-fold and 2.0-fold, respectively, across rat small intestine and 2.6-fold, 2.7-fold, 1.6-fold and 3.3-fold, respectively, across Caco-2 cell monolayer. Almost 90% of the tobramycin sulphate was released from tablets within 4h. The developed drug delivery system containing chitosan-NAC and glutathione is a promising tool for oral tobramycin sulphate administration showing improved gastrointestinal uptake and a sustained release.

Thiolated chitosan: development and in vitro evaluation of an oral delivery system for acyclovir.

The aim of the study was to develop a novel oral delivery system for the efflux pump substrate acyclovir (ACY) utilizing thiolated chitosan as excipient which is capable of inhibiting P-glycoprotein (P-gp). Three chitosan-4-thiobutylamidine (Chito-TBA) conjugates with increasing molecular mass (Chito-9.4kDa-TBA, Chito-150kDa-TBA and Chito-600kDa-TBA) were synthesized and permeation studies on rat intestinal mucosa and Caco-2 monolayers were performed. Additionally, tablets comprising the conjugates and ACY were tested towards their drug release behaviour. The efflux ratio (secretory P(app)/absorptive P(app)) of ACY across Caco-2 monolayers was determined to be 2.5 and in presence of 100microM verapamil 1.1 which indicates ACY as P-gp substrate. In comparison to buffer only, the transport of ACY in presence of 0.5% (m/v) unmodified chitosan, 0.5% (m/v) Chito-150kDa-TBA and 0.5% (m/v) Chito-150kDa-TBA with 0.5% (m/v) reduced glutathione (GSH), was 1.3-, 1.6- and 2.1-fold improved, respectively. Transport studies across Caco-2 monolayers showed that P-gp inhibition is dependent on the average molecular mass of thiolated chitosan showing following rank order: 0.5% (m/v) Chito-150kDa-TBA/GSH>0.5% (m/v) Chito-9.4kDa-TBA/GSH>0.5% (m/v) Chito-600kDa-TBA/GSH. The higher the molecular mass of Chito-TBA was, the more sustained was the release of ACY. Chito-150kDa-TBA/GSH might be an appropriate sustained release drug delivery system for ACY, which is able to enhance ACY transport due to efflux pump inhibition.