Effect of excipients on breast cancer resistance protein substrate uptake activity

Enhanced in vitro bioavailability of resveratrol-loaded emulsion stabilized by β-lactoglobulin-catechin with excellent antioxidant activity

The study aimed to fabricate β-Lactoglobulin-catechin (β-La-Ca) conjugates as a natural designed antioxidant emulsifier to improve the physicochemical stability of resveratrol emulsion delivery system. Fourier transform infrared (FT-IR) and fluorescence spectroscopy analysis confirmed the formation of conjugates using free radical grafting. The antioxidant ability of emulsion was evaluated by DPPH scavenging activities and ORAC experiments. The emulsion stabilized by β-La-Ca conjugates exhibited strong antioxidant activity with ORAC value of 2541.39 ± 29.58 μmol TE/g, which was significantly higher than that by β-Lactoglobulin alone with 387.96 ± 23.45 μmol TE/g or their mixture with 948.23 ± 32.77 μmol TE/g. During the whole simulated gastrointestinal digestion, emulsion stabilized by β-La-Ca conjugates exhibited excellent oxidative stability that the lipid was mainly digested in the small intestine. This behavior attributed to the greater stability of resveratrol to chemical transformation leading to a higher overall bioavailability in vivo. These results suggested that the β-La-Ca conjugates could be used to fabricate the emulsion-based delivery system to improve the oxidative stability and bioavailability of chemically labile hydrophobic bioactive compounds.

Power-Up for Mucoadhesiveness: Two Generations of Thiolated Surfactants for Enhanced Sticky Nanoemulsions

Nanoemulsions can be tuned toward enhanced gastro-intestinal retention time by incorporating thiolated surfactants into their surface. Tailoring the chemical reactivity of the thiol headgroup has major influence on mucoadhesive features of the nanoemulsion. Two generations of thiolated surfactants were synthetically derived from PEG-40-stearate featuring either a free thiol group or an S-protected thiol group. The surfactants were characterized regarding critical micelle concentration (CMC), hemolytic activity, and cytotoxicity. Subsequently, they were incorporated into nanoemulsions and the resulting nanoemulsions were characterized regarding particle size, polydispersity index (PDI), zeta potential, and time-dependent stability. Afterward, mucosal interactions as well as mucoadhesion on porcine intestinal mucosa were investigated. Successful synthesis of Cysteine-PEG-40-stearate (CYS-PEG-40-stearate) and MNA-Cysteine-PEG-40-stearate (MNA-CYS-PEG-40-stearate) was confirmed by 1H NMR spectroscopy. Both chemical modifications led to slightly elevated CMC values while preserving low cytotoxicity and hemotoxicity. Incorporation into nanoemulsions had minor influence on overall physical particle characteristics, while interactions with mucus and mucoadhesiveness of the nanoemulsions were drastically improved resulting in the rank order PEG-40-stearate < CYS-PEG-40-stearate < MNA-CYS-PEG-40-stearate. Accordingly, thiolated surfactants, especially S-protected derivatives, are versatile tools to generate highly mucoadhesive nanoemulsions.

Redefine the role of d-α-Tocopheryl polyethylene glycol 1000 succinate on P-glycoprotein, multidrug resistance protein 1, and breast cancer resistance protein mediated cancer multidrug resistance

Cancer drug resistance is an ever-changing problem that most patients need to face in their later stages of treatment, especially the multidrug resistant (MDR) type. The drug efflux transporters, including P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), and breast cancer resistance protein (BCRP), play the crucial roles in this sophisticated battle. In recent decades, researchers try to find potential inhibitors to impede the drug efflux function of above transporters. d-α-Tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) is a prevalently used excipient in the formulation design. In the present study, the modulatory effects and mechanisms of vitamin E TPGS on the efflux transporters were investigated. And the cancer MDR reversing ability of vitamin E TPGS was evaluated as well. Stable-cloned transporter over-expressed cell lines were used for mechanisms study, while several types of MDR cancer cell lines were adopted as reversing evaluation models. The results exhibited that vitamin E TPGS significantly inhibited the efflux function of P-gp, MRP1, and BCRP under non-cytotoxic concentrations, but not influencing the protein expression levels. Through efflux assay and molecular docking, vitamin E TPGS was found to be an uncompetitive, non-competitive, and competitive inhibitor on chemotherapeutic drug doxorubicin efflux in P-gp, MRP1, and BCRP over-expressing cell lines, respectively. Furthermore, the basal ATPase activity of three transporters were significantly inhibited by vitamin E TPGS at 10 μM. And the cell membrane fluidity of P-gp over-expressing cell line was enhanced by 22.58% with 5 μM vitamin E TPGS treatment, compared to the parental Flp-In™-293 cell line (without P-gp). The resistance reversing ability of vitamin E TPGS was prominent in MCF-7/DOX MDR breast cancer cell line, which over-expressed P-gp, MRP1, and BCRP. These significant results suggested that vitamin E TPGS is a promising modulator on transporters mediated cancer MDR. Vitamin E TPGS is not an inert excipient, but possesses MDR-reversing pharmacological effects, and deserves a re-purposing application on the future combinatorial regimen design for MDR cancer treatment.

Pluronic F-68 and F-127 Based Nanomedicines for Advancing Combination Cancer Therapy

Pluronics are amphiphilic triblock copolymers composed of two hydrophilic poly (ethylene oxide) (PEO) chains linked via a central hydrophobic polypropylene oxide (PPO). Owing to their low molecular weight polymer and greater number of PEO segments, Pluronics induce micelle formation and gelation at critical micelle concentrations and temperatures. Pluronics F-68 and F-127 are the only United States (U.S.) FDA-approved classes of Pluronics and have been extensively used as materials for living bodies. Owing to the fascinating characteristics of Pluronics, many studies have suggested their role in biomedical applications, such as drug delivery systems, tissue regeneration scaffolders, and biosurfactants. As a result, various studies have been performed using Pluronics as a tool in nanomedicine and targeted delivery systems. This review sought to describe the delivery of therapeutic cargos using Pluronic F-68 and F-127-based cancer nanomedicines and their composites for combination therapy.

Lactose hydrate can increase the transcellular permeability of β-naphthol in rat jejunum and ileum

BACKGROUND

The unstirred water layer (UWL) is an integral part of the apical surface of mucosal epithelia and comprises mucins (MUC), for which there are many molecular species. Galectins, a family of β-galactoside-binding lectins, form a lattice barrier on surface epithelial cells by interacting with MUC. Lactose inhibits the galectin-MUC interaction. Therefore, the present study investigated the galectin-MUC interaction in the mucosa of the gastrointestinal tract and its role in intestinal barrier functions.

MATERIALS AND RESULTS

The effects of lactose hydrate (LH) on the membrane permeability of the rat small intestine and Caco-2 cells were examined. LH enhanced the membrane permeability of the rat small intestine, which contains the UWL, via a transcellular route, for which the UWL is the rate limiting factor. The membrane permeability of Caco-2 cells, in which the UWL is insufficient, was not affected by LH. The apparent permeability coefficient (P_app) of a paracellular marker was not significantly altered in the rat small intestine or Caco-2 cells treated with LH at any concentration. Furthermore, the P_app of β-naphthol which is a transcellular marker was not significantly altered in Caco-2 cells treated with LH, but was significantly increased in the rat small intestine in a LH concentration-dependent manner.

CONCLUSIONS

The present results demonstrate that the physical barrier has an important function in gastrointestinal membrane permeability, and LH-induced changes increase the transcellular permeability of β-naphthol in rat small intestine.

Strategies and Mechanism in Reversing Intestinal Drug Efflux in Oral Drug Delivery

Efflux transporters distributed at the apical side of human intestinal epithelial cells actively transport drugs from the enterocytes to the intestinal lumen, which could lead to extremely poor absorption of drugs by oral administration. Typical intestinal efflux transporters involved in oral drug absorption process mainly include P-glycoprotein (P-gp), multidrug resistance proteins (MRPs) and breast cancer resistance protein (BCRP). Drug efflux is one of the most important factors resulting in poor absorption of oral drugs. Caco-2 monolayer and everted gut sac are sued to accurately measure drug efflux in vitro. To reverse intestinal drug efflux and improve absorption of oral drugs, a great deal of functional amphiphilic excipients and inhibitors with the function of suppressing efflux transporters activity are generalized in this review. In addition, different strategies of reducing intestinal drugs efflux such as silencing transporters and the application of excipients and inhibitors are introduced. Ultimately, various nano-formulations of improving oral drug absorption by inhibiting intestinal drug efflux are discussed. In conclusion, this review has significant reference for overcoming intestinal drug efflux and improving oral drug absorption.

Effect of excipients on oral absorption process according to the different gastrointestinal segments

INTRODUCTION

Excipients are necessary to develop oral dosage forms of any Active Pharmaceutical Ingredient (API). Traditionally, excipients have been considered inactive and inert substances, but, over the years, numerous studies have contradicted this belief. This review focuses on the effect of excipients on the physiological variables affecting oral absorption along the different segments of the gastrointestinal tract. The effect of excipients on the segmental absorption variables are illustrated with examples to help understand the complexity of predicting their in vivo effects.

AREAS COVERED

The effects of excipients on disintegration, solubility and dissolution, transit time, and absorption are analyzed in the context of the different gastrointestinal segments and the physiological factors affecting release and membrane permeation. The experimental techniques used to study excipient effects and their human predictive ability are reviewed.

EXPERT OPINION

The observed effects of excipient in oral absorption process have been characterized in the past, mainly in vitro (i.e. in dissolution studies, in vitro cell culture methods or in situ animal studies). Unfortunately, a clear link with their effects in vivo, i.e. their impact on Cmax or AUC, which need a mechanistic approach is still missing. The information compiled in this review leads to the conclusion that the effect of excipients in API oral absorption and bioavailability is undeniable and shows the need of implementing standardized and reproducible preclinical tools coupled with mechanistic and predictive physiological-based models to improve the current empirical retrospective approach.

Abdulbaqi I, Seok Ming T, Siok Yee C, A. Wahab H, Asif SM, Darwis Y. Liquid and Solid Self-Emulsifying Drug Delivery Systems (SEDDs) as Carriers for the Oral Delivery of Azithromycin: Optimization, In Vitro Characterization and Stability Assessment

Azithromycin (AZM) is a macrolide antibiotic used for the treatment of various bacterial infections. The drug is known to have low oral bioavailability (37%) which may be attributed to its relatively high molecular weight, low solubility, dissolution rate, and incomplete intestinal absorption. To overcome these drawbacks, liquid (L) and solid (S) self-emulsifying drug delivery systems (SEDDs) of AZM were developed and optimized. Eight different pseudo-ternary diagrams were constructed based on the drug solubility and the emulsification studies in various SEDDs excipients at different surfactant to co-surfactant (Smix) ratios. Droplet size (DS) < 150 nm, dispersity (Đ) ≤ 0.7, and transmittance (T)% > 85 in three diluents of distilled water (DW), 0.1 mM HCl, and simulated intestinal fluids (SIF) were considered as the selection criteria. The final formulations of L-SEDDs (L-F1(H)), and S-SEDDs (S-F1(H)) were able to meet the selection requirements. Both formulations were proven to be cytocompatible and able to open up the cellular epithelial tight junctions (TJ). The drug dissolution studies showed that after 5 min > 90% and 52.22% of the AZM was released from liquid and solid SEDDs formulations in DW, respectively, compared to 11.27% of the pure AZM, suggesting the developed SEDDs may enhance the oral delivery of the drug. The formulations were stable at refrigerator storage conditions.

Inhibitory effect of sixteen pharmaceutical excipients on six major organic cation and anion uptake transporters

To date, relatively little is known about the interactions of pharmaceutical excipients with hepatic and renal drug uptake transporters. The present study was designed to systematically evaluate the effects of 16 commonly consumed excipients on human organic cation transporter 1 and 2 (hOCT1 and hOCT2), human organic anion transporter 1 and 3 (hOAT1 and hOAT3) and human organic anion transporting polypeptide 1B1 and 1B3 (hOATP1B1 and hOATP1B3). The inhibitory effects and mechanisms of excipients on transporters were investigated using in vitro uptake studies, cell viability assays, concentration-dependent studies, and the Lineweaver-Burk plot method. Triton X-100 is a non-competitive inhibitor for all six transporters. Tween 20 inhibits hOCT2, hOAT1, hOAT3, and hOATP1B3 in a mixed way, whereas it competitively inhibits hOATP1B1. The inhibition of Tween 80 is competitive for hOCT2, non-competitive for hOATP1B1 and hOATP1B3, and mixed for hOAT1 and hOAT3. Concentration-dependent studies identify Triton X-100 as a strong inhibitor of hOCT1 and hOCT2 with IC₅₀ values of 20.1 and 4.54 μg/mL, respectively. Additionally, Triton X-100, Tween 20, and Tween 80 strongly inhibit hOAT3 with IC₅₀ values ≤31.0 μg/mL. The present study is significant in understanding the excipient-drug interactions and provides valuable information for excipient selection in drug development.

Lipid-Based Nanosystem As Intelligent Carriers for Versatile Drug Delivery Applications

:

The contemporary drug discovery research shows that most of the drug candidates are highly potent, but showing poor aqueous solubility leads a variety of challenges for formulation scientists to develop a suitable formulation to improve the systemic bioavailability of such drugs. Lipid-based nanocarriers act as a major and most projecting approach overcoming the limitations which affect several physiochemical properties of drug such as the solubility, partition coefficient and bioavailability or absorption. This also fulfills a variety of product requirements and helps to overcome several limitations as decided by symptoms of the disease, various routes of administration of drug, price concern, increasing strength of product, noxious or harmful effect of drug, and dose efficacy. The lipidic nanosystem formulates aqueous drug in lipid base and is also a commercially feasible approach for the formulation of different dosage forms meant for topical or transdermal, oral, ocular, pulmonary, and parenteral delivery. This review provides a brief on lipid-based drug delivery nanocarrier and the mechanisms by which lipids and lipidic excipients improve the oral absorption of drugs with poor aqueous solubility and also provide a viewpoint on the promising applications of lipidic nanoparticulate systems.

Engineering of Long-Term Stable Transparent Nanoemulsion Using High-Gravity Rotating Packed Bed for Oral Drug Delivery

Background

Oil-in-water drug nanoemulsion forms drug delivery systems with high oral bioavailability. The conventional fabrication methods of nanoemulsion are low energy emulsification methods and high energy emulsification methods. However, both two methods are not ideal for industrial production. The problem of low energy emulsification methods is the high dosage of surfactant and co-surfactant which has potential biosecurity issues. What is more, high energy emulsification methods have some disadvantages, like the destruction of drug components, the price of equipment and the difficulties of industrial production. Hence, there have been a few commercial drug nanoemulsions so far.

Methods

In this work, we reported a novel method for the fabrication of stable and transparent drug nanoemulsion which contains hydrophilic drug rosuvastatin (ROS) calcium or hydrophobic drug silybinin (SYN) by using high-gravity rotating packed bed (RPB). The drug nanoemulsion was systematically characterized by droplet size, size distribution, stability and in vitro drug release as well as Caco-2 cells permeability.

Results

Compared with the self-emulsification method (SE), high-gravity technology could reduce 75% amount of mixed surfactants. The as-prepared nanoemulsion exhibited a very narrow droplet size distribution with a size of 13.53 ± 0.53 nm and a polydispersity index of 0.073 ± 0.018. Meanwhile, the drug nanoemulsion was physicochemically stable at 25°C and 4°C for one-year storage. Furthermore, both ROS and SYN nanoemulsion displayed higher cell permeability and in vitro dissolution than that of commercial formulations.

Conclusion

These results demonstrate that RPB can be a potential device to facilitate the industrial production of drug nanoemulsion.

Pluronic micelles with suppressing doxorubicin efflux and detoxification for efficiently reversing breast cancer resistance

The antitumor activity of doxorubicin (DOX) is often limited owing to the occurrence of multidrug resistance (MDR) during treatment. Herein, we developed hybrid polymeric micelles, which consisted of pluronic F127 as long-circulating helper in blood, and phenylboronic ester-grafted pluronic P123 (PHE) as efflux and detoxification regulator to efficiently deliver DOX and reverse MDR in vivo. Hybrid F127/PHE micelles exhibited higher stability and drug encapsulation (~80%) than simple F127/P123 micelles due to its lower CMC, and displayed in vitro drug release in a hydrogen peroxide (H₂O₂)-sensitive manner. Besides, DOX-loaded hybrid micelles (F127/PHE-DOX) possessed higher cell-killing ability and induce more apoptotic in MDR-cells than other groups, which was probably because it not only could greatly increase intracellular drug concentration by inhibiting P-gp mediated drug efflux, but also promote reactive oxygen species (ROS) generation by decreasing glutathione (GSH) levels. Besides, in vivo evaluation indicated that F127/PHE-DOX could well accumulate at tumor regions and exhibit the strongest tumor growth inhibition (TGI 87.87%) accompanied with low side effects. As a result, F127/PHE micelles had great potentials as a platform for anticancer drugs delivery and tumor MDR reversal in clinical application.

Current trends in drug metabolism and pharmacokinetics

Pharmacokinetics (PK) is the study of the absorption, distribution, metabolism, and excretion (ADME) processes of a drug. Understanding PK properties is essential for drug development and precision medication. In this review we provided an overview of recent research on PK with focus on the following aspects: (1) an update on drug-metabolizing enzymes and transporters in the determination of PK, as well as advances in xenobiotic receptors and noncoding RNAs (ncRNAs) in the modulation of PK, providing new understanding of the transcriptional and posttranscriptional regulatory mechanisms that result in inter-individual variations in pharmacotherapy; (2) current status and trends in assessing drug-drug interactions, especially interactions between drugs and herbs, between drugs and therapeutic biologics, and microbiota-mediated interactions; (3) advances in understanding the effects of diseases on PK, particularly changes in metabolizing enzymes and transporters with disease progression; (4) trends in mathematical modeling including physiologically-based PK modeling and novel animal models such as CRISPR/Cas9-based animal models for DMPK studies; (5) emerging non-classical xenobiotic metabolic pathways and the involvement of novel metabolic enzymes, especially non-P450s. Existing challenges and perspectives on future directions are discussed, and may stimulate the development of new research models, technologies, and strategies towards the development of better drugs and improved clinical practice.

Development of a Ternary Solid Dispersion Formulation of LW6 to Improve the In Vivo Activity as a BCRP Inhibitor: Preparation and In Vitro/In Vivo Characterization

LW6 (3-[2-(4-adamantan-1-yl-phenoxy)-acetylamino]-4-hydroxy-benzoic acid methyl ester) is a potent inhibitor of drug efflux by the breast cancer resistance protein (BCRP). However, its poor aqueous solubility leads to low bioavailability, which currently limits in vivo applications. Therefore, the present study aimed to develop ternary solid dispersion (SD) formulations in order to enhance the aqueous solubility and dissolution rate of LW6. Various SDs of LW6 were prepared using a solvent evaporation method with different drug/excipient ratios. The solubility and dissolution profiles of LW6 in different SDs were examined, and F8-SD which is composed of LW6, poloxamer 407, and povidone K30 at a weight ratio of 1:5:8 was selected as the optimal SD. The structural characteristics of F8-SD were also examined using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM). In the acidic to neutral pH range, F8-SD achieved rapid dissolution with a drug release of 76–81% within 20 min, while the dissolution of pure LW6 was negligible. The XRPD patterns indicated that F8-SD probably enhanced the solubility and dissolution of LW6 by changing the drug crystallinity to an amorphous state, in addition to the solubilizing effect of the hydrophilic carriers. Furthermore, F8-SD significantly improved the oral bioavailability of topotecan, which is a BCRP substrate, in rats. The systemic exposure of topotecan was enhanced approximately 10-fold by the concurrent use of F8-SD. In conclusion, the ternary SD formulation of LW6 with povidone K30 and poloxamer 407 appeared to be effective at improving the dissolution and in vivo effects of LW6 as a BCRP inhibitor.

Improved In vivo Effect of Chrysin as an Absorption Enhancer Via the Preparation of Ternary Solid Dispersion with Brij®L4 and Aminoclay

Background

Chrysin is a strong inhibitor of breast cancer resistance protein (BCRP) but it is practically insoluble in water. Effective solubilization of chrysin is critical for its pharmaceutical application as an absorption enhancer via inhibition of BCRP-mediated drug efflux.

Objective

This study aimed to develop an effective oral formulation of chrysin to improve its in vivo effect as an absorption enhancer.

Method

Solid dispersions (SDs) of chrysin were prepared with hydrophilic carriers having surface acting properties and a pH modulator. In vitro and in vivo characterizations were performed to select the optimal SDs of chrysin.

Results

SDs with Brij®L4 and aminoclay was most effective in increasing the solubility of chrysin by 13-53 fold at varying drug-carrier ratios. Furthermore, SDs significantly improved the dissolution rate and extent of drug release. SDs (chrysin: Brij®L4: aminoclay=1:3:5) achieved approximately 60% and 83% drug release within 1 h and 8 h, respectively, in aqueous medium, while the dissolution of the untreated chrysin was less than 13%. XRD patterns indicated the amorphous state of chrysin in SDs. The SD formulation was effective in improving the bioavailability of topotecan, a BCRP substrate in rats. Following oral administration of topotecan with the SDs of chrysin, the Cmax and AUC of topotecan was enhanced by approximately 2.6- and 2-fold, respectively, while the untreated chrysin had no effect.

Conclusion

The SD formulation of chrysin with Brij®L4 and aminoclay appeared to be promising in improving the dissolution of chrysin and enhancing its in vivo effect as an absorption enhancer.

Brain-targeted delivery of PEGylated nano-bacitracin A against Penicillin-sensitive and -resistant Pneumococcal meningitis: formulated with RVG29 and Pluronic® P85 unimers

Pneumococcal meningitis (PM), caused by Streptococcus pneumonia, remains a high-burden disease in developing countries. Antibiotic therapy has been limited due to the inefficiency of drug transport across the blood-brain barrier (BBB) and the emergence of drug-resistant strains. In our preliminary study, PEGylated nano-self-assemblies of bacitracin A (PEGylated Nano-BA_12K) demonstrated a strong antibacterial potency against S. pneumonia. In this study, the potential application of this micelle for the treatment of both Penicillin-sensitive and -resistant PM was studied. To address BBB-targeting and -crossing issues, PEGylated Nano-BA_12K was formulated with a specific brain-targeting peptide (rabies virus glycopeptide-29, RVG₂₉) and a P-glycoprotein inhibitor (Pluronic^® P85 unimers) to construct a mixed micellar system (RVG₂₉-Nano-BA_P85). RVG₂₉-Nano-BA_P85 demonstrated a strong antibacterial potency against 13 clinical isolates of S. pneumonia, even higher than that of Penicillin G, a conventional anti-PM agent. RVG₂₉-Nano-BA_P85 had more cellular uptake in brain capillary endothelial cells (BCECs) and higher BBB-crossing efficiency than single formulated Nano-BAs as shown in an in vitro BBB model. The enhanced BBB-permeability was attributed to the synergetic effect of RVG₂₉ and P85 unimers through receptor-mediated transcytosis, exhaustion of ATP, and reduction in membrane microviscosity. In vivo results further demonstrated that RVG₂₉-Nano-BA_P85 was able to accumulate in brain parenchyma as confirmed by in vivo optical imaging. In addition, RVG₂₉-Nano-BA_P85 exhibited high therapeutic efficiencies in both Penicillin-sensitive and -resistant PM mouse models with negligible systemic toxicity. Collectively, RVG₂₉-Nano-BA_P85 could effectively overcome BBB barriers and suppressed the growth of both drug-sensitive and -resistant S. pneumonia in the brain tissues, which demonstrated its potential for the treatment of PM.

Inhibitory Effects of Commonly Used Excipients on P-Glycoprotein in Vitro

Pharmaceutical excipients are no longer considered inert and have been shown to influence the activity of metabolic enzymes and transporters, resulting in altered pharmacokinetics of substrate drugs. In this study, the effect of 25 excipients commonly used in drug formulations were investigated for their effect on P-glycoprotein (P-gp) activity. The effect of excipients on P-gp were assessed by measuring the change in the cellular accumulation of a P-gp substrate, digoxin, in MDCK-MDR1 (Madin Darby canine kidney transfected with multidrug resistance 1 gene) cells. The cells were exposed to low (10 μM) and high (200 μM) concentrations of excipient along with 10 μM digoxin. Excipient concentrations were chosen to span the range of concentrations previously used for investigating activities in vitro. At 10 μM of excipient, an increase in the intracellular digoxin concentration was seen with d-α-tocopherol poly-(ethylene glycol) succinate (Vit-E-PEG; p = 0.002), poly(ethylene oxide)₂₀ sorbitan monooleate (Tween 80; p = 0.001), cetyltrimethylammonium bromide (CTAB; p = 0.021), poly(ethylene oxide)₃₅ modified castor oil (Cremophor EL; p = 0.01), polyethylene glycol₁₅-hydroxystearate (Solutol HS 15; p = 0.006), and poly(ethylene glycol) hexadecyl ether (Brij 58; p = 0.001). At 200 μM, Vit-E-PEG ( p < 0.0001), sodium 1,4-bis (2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate (AOT; p < 0.0001), Tween 80 ( p < 0.0001), CTAB ( p = 0.004), poly(ethylene oxide)₂₀ sorbitan monolaurate (Tween 20; p < 0.0001), Cremophor EL ( p < 0.0001), Solutol HS 15 ( p < 0.0001), Brij 58 ( p < 0.0001), and sodium carboxymethyl cellulose (NaCMC; p = 0.006) increased intracellular digoxin significantly. Concentration-dependent inhibition of P-gp was then investigated for selected excipients giving an IC₅₀ for Vit-E-PEG (12.48 μM), AOT (192.5 μM), Tween 80 (45.29 μM), CTAB (96.67 μM), Tween 20 (74.15 μM), Cremophor EL (11.92 μM), Solutol HS 15 (179.8 μM), Brij 58 (25.22 μM), and NaCMC (46.69 μM). These data add to the growing body of evidence demonstrating that not all excipients are inert and will aid excipient choice for rational formulation development.

Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics

To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.

Effects of Various Pharmaceutical Excipients on the Intestinal Transport and Absorption of Sulfasalazine, a Typical Substrate of Breast Cancer Resistance Protein Transporter

Breast cancer resistance protein (BCRP) transporter is an efflux transporter that utilizes energy from adenosine triphosphate hydrolysis to push its substrates, regardless of the concentration gradient. Its presence on the apical membrane of the intestinal mucosa is a major obstacle for the intestinal absorption of its substrates. In this study, we examined the effects of various pharmaceutical excipients on the intestinal transport and absorption of sulfasalazine, a BCRP substrate. Four excipients, including 0.05% and 0.075% BL-9EX, 0.01% and 0.05% Brij 97, 0.075% Labrasol, and 0.05% and 0.1% Tween 20 decreased the secretory transport of sulfasalazine in an in vitro diffusion chamber. Further investigation in an in situ closed loop experiment in rats showed that 0.05% and 0.1% BL-9EX and 0.1% Brij 97 effectively enhanced the intestinal absorption of sulfasalazine while maintaining minimal toxicity to the intestinal mucosa. However, 0.1% Brij 97 also increased the intestinal absorption of 5(6)-carboxyfluorescein, a paracellular marker compound. These findings suggest that BL-9EX might effectively inhibit the BCRP-mediated efflux of sulfasalazine in vivo, indicating that BL-9EX could improve the intestinal absorption of sulfasalazine and other BCRP substrates.

Mechanisms of TPGS and its derivatives inhibiting P-glycoprotein efflux pump and application for reversing multidrug resistance in hepatocellular carcinoma

We have developed a TPGS–GA conjugate and TPGS–LA conjugate which possess more effective P-gp inhibition compared to TPGS because of the enhancement of hydrophilicity and negative charge.

Characterization and evaluation of a self-microemulsifying drug delivery system containing tectorigenin, an isoflavone with low aqueous solubility and poor permeability

The purpose of this study was to characterize and evaluate tectorigenin-loaded self-microemulsifying drug delivery system (TG-SMEDDS), a previously studied preparation, and further confirm the improvement of TG in solubility and bioavailability. The appearance of TG-SMEDDS was clear and transparent, with good mobility. The microemulsion formed by TG-SMEDDS was globular, edge smooth, clear-cut, and distribution homogeneous under transmission electron microscope. The stability studies revealed that TG-SMEDDS remained stable at room temperature for at least 3 months. TG-SMEDDS showed excellent dissolution behavior that more than 90% of TG was released in only 5 min. The in situ intestinal perfusion studies indicated enhancement of absorption in four tested intestinal segments, and the main absorption site of TG was changed to duodenum. In addition, TG-SMEDDS showed significantly higher Cmax and AUC values (11-fold and 5-fold higher values, respectively; P < 0.05) than TG, and the absolute oral bioavailability of TG-SMEDDS was 56.33% (5-fold higher than that of crude TG). What's more, the AUC0-t of crude TG and TG-SMEDDS in bile duct non-ligation rats were 6.05 and 2.80 times, respectively, than that in bile duct ligation rats, indicating the existence of enterohepatic circulation and the secretion of bile could significantly affect the absorption of TG. Further studies showed that even the bile duct was ligation, TG-SMEDDS can still keep a better oral bioavailability (179.67%, compared with crude TG in the bile duct non-ligation rats). Therefore, our study implies that SMEDDS containing TG could be an effective strategy for the oral administration of TG.

Self-Nanoemulsified Drug Delivery System of Hydrochlorothiazide for Increasing Dissolution Rate and Diuretic Activity

Hydrochlorothiazide (HCTZ) is a class IV drug according to the Biopharmaceutical Classification System. This study aimed the development of self-nanoemulsifying drug delivery system (SNEDDS) for HCTZ as an approach to overcome the biopharmaceutical limitations. Pre-formulation screening and ternary phase diagrams were carried out to select the oil phase, the surfactant, and the co-surfactant as the amount of each constituent. The optimized formulations, with reduced amount of surfactant, and composed of medium chain triglycerides, Cremophor EL and Transcutol P did not affect the pH or show drug incompatibilities. The SNEDDS were stabilized by the nanoscale globules and high negative zeta potential. All the physicochemical characterization assays were performed in biorelevant media to better predict the in vivo performance. The enhanced dissolution rate of the SNEDDS reflected in the in vivo diuretic activity, presenting a natriuresis, kaliuresis, and chloriuresis at early stages and an increased volume of total urine compared with HCTZ alone. The designed SNEDDS produced an improvement in the pharmacodynamics due to high dissolution and probable inhibition of intestinal efflux protein by Cremophor EL. The use of SNEDDS demonstrated to be an efficient approach to modulate the absorption of HCTZ and drug therapeutics.

Rational design of hybrid nanomicelles integrating mucosal penetration and P-glycoprotein inhibition for efficient oral delivery of paclitaxel

A dual functional TPGS-succinic acid-mercaptoethylamine (TPGS-SH) material was synthesized to improve the oral absorption of anticancer drugs, aiming to integrate the advantages of mucosal penetration with P-glycoprotein (P-gp) inhibition. Paclitaxel-loaded hybrid nanomicelles (CS-VES/TPGS-SH) with a uniform particle size (234.2-273.9nm), high drug loading (11.50±0.91%), and good encapsulation efficiency (86.18±3.73%) were fabricated. The absorption rate and apparent permeability coefficient were significantly improved in the whole intestine, especially in the duodenum segment, with a 3.68- and 3.22-fold enhancement being detected after perfusion with CS-VES/TPGS-SH hybrid nanomicelles. Moreover, TPGS-SH showed a considerable P-gp inhibition effect with verapamil. CS-VES/TPGS-SH nanomicelles can effectively pass through the mucosal layer and increase the intracellular drug content in duodenum, jejunum, and colon segments as further reflected by the in situ mucosal penetration study. Maximum concentration (C_max) and area under curve (AUC_(0-t)) values of hybrid nanomicelles were improved by 3.39- and 3.58-fold, respectively, compared to those of paclitaxel solution in rats. Therefore, the designed bifunctional hybrid CS-VES/TPGS-SH nanomicelles could function as efficient drug carriers, facilitating the oral absorption of hydrophobic anticancer drugs.

The biopharmaceutical classification system of excipients

The increasing number of new chemical entities is bringing new challenges to the field of drug delivery. These drugs present bioavailability issues that are frequently associated with intestinal metabolism or efflux mechanisms. Some excipients, particularly surfactants, have demonstrated a capacity to interfere with these mechanisms, improving drug bioavailability. Consequently, these excipients can no longer be considered as inert and should be subject to special considerations from a regulatory perspective. In the present manuscript, the state-of-the-art research related to these abilities of excipients to interfere with intestinal metabolism and efflux mechanisms are presented and discussed. Here, a biopharmaceutical classification system of excipients is proposed for the first time as a tool in the development of new products and for regulatory purposes.

Encapsulation of Antibiotic Levofloxacin in Biocompatible Microemulsion Formulation: Insights from Microstructure Analysis

Microemulsions (μEs) are unique systems that offer exciting perspectives in biophysical research for mimicing biomembranes at the molecular level. In the present study, biocompatible μE formulation of a new oil-in-water (o/w) system comprising clove oil/Tween 20/2-propanol/water was accomplished for encapsulating an antibiotic, levofloxacin (LVF). The pseudoternary phase diagram was delineated at a constant cosurfactant/surfactant (2:1) ratio to meet the economic feasibility. The gradual changes occurring in the microstructure of the as-formulated four-component μEs were explored via multiple complementary characterization techniques. The results of electrical conductivity (σ), viscosity (η), and optical microscopic measurements suggested the existence of a percolation transition to a bicontinuous structure in the microregions of the as-formulated μE. LVF displayed a high solubility (5.0 wt %) at the pH of 6.9 in an optimum μE formulation comprising 2-propanol (36.4%), Tween 20 (18.2%), clove oil (20.7%), and water (24.7%). The LVF-loaded μE composition showed long-term stability for over 6 months of storage. Fourier transform IR analysis showed that LVF was stable inside the μE formulation, indicating the absence of any possible aggregation of LVF. Dynamic light scattering revealed that the average particle size of drug-free μE (64.5 ± 3.4 nm) increases to 129.7 ± 5.8 nm upon loading of LVF, suggesting the accumulation of LVF in the interfacial layers of the micelles. Moreover, fluorescence measurements indicated that LVF might be localized in the interfacial film of μE system, which may result in a controlled release of drug.

Preparation and Characterization of Microemulsions of Myricetin for Improving Its Antiproliferative and Antioxidative Activities and Oral Bioavailability

To improve the bioactivity and oral bioavailability of myricetin, a microemulsion formulation was successfully developed, which consisted of Cremophor RH40 (12%), Tween 80 (6%), Transcutol HP (9%), WL 1349 (18%), and distilled water (55%). With lower content of surfactants and higher stability after dilution and storage for 6 months, the optimized myricetin microemulsion (MYR-ME) could dramatically enhance the solubility of myricetin 1225 times that in water. MYR-ME significantly increased antiproliferative activity against human cancer cell HepG2 without influence on normal cell LO2. It also notably improved the cellular antioxidative activity of myricetin. Furthermore, the oral bioavailability of myricetin was remarkably enhanced by MYR-ME in Sprague-Dawley rats after oral administration, which was 14.43-fold that with myricetin suspension. Therefore, the MYR-ME developed here could be used as a potential carrier for myricetin with substantially enhanced bioactivities and bioavailability and might promote myricetin's future utilization in functional foods and cosmetics.

50years of oral lipid-based formulations: Provenance, progress and future perspectives

Lipid based formulations (LBF) provide well proven opportunities to enhance the oral absorption of drugs and drug candidates that sit close to, or beyond, the boundaries of Lipinski's 'rule-of-five' chemical space. Advantages in permeability, efflux and presystemic metabolism are evident; however, the primary benefit is in increases in dissolution and apparent intestinal solubility for lipophilic, poorly water soluble drugs. This review firstly details the inherent advantages of LBF, their general properties and classification, and provides a brief retrospective assessment of the development of LBF over the past fifty years. More detailed analysis of the ability of LBF to promote intestinal solubilisation, supersaturation and absorption is then provided alongside review of the methods employed to assess formulation performance. Critical review of the ability of simple dispersion and more complex in vitro digestion methods to predict formulation performance subsequently reveals marked differences in the correlative ability of in vitro tests, depending on the properties of the drug involved. Notably, for highly permeable low melting drugs e.g. fenofibrate, LBF appear to provide significant benefit in all cases, and sustained ongoing solubilisation may not be required. In other cases, and particularly for higher melting point drugs such as danazol, where re-dissolution of crystalline precipitate drug is likely to be slow, correlations with ongoing solubilisation and supersaturation are more evident. In spite of their potential benefits, one limitation to broader use of LBF is low drug solubility in the excipients employed to generate formulations. Techniques to increase drug lipophilicity and lipid solubility are therefore explored, and in particular those methods that provide for temporary enhancement including lipophilic ionic liquid and prodrug technologies. The transient nature of these lipophilicity increases enhances lipid solubility and LBF viability, but precludes enduring effects on receptor promiscuity and off target toxicity. Finally, recent efforts to generate solid LBF are briefly described as a means to circumvent the need to encapsulate in soft or hard gelatin capsules, although the latter remain popular with consumers and a proven means of LBF delivery.

The Effects of Pharmaceutical Excipients on Gastrointestinal Tract Metabolic Enzymes and Transporters-an Update

Accumulating evidence from the last decade has shown that many pharmaceutical excipients are not pharmacologically inert but instead have effects on metabolic enzymes and/or drug transporters. Hence, the absorption, distribution, metabolism, and elimination (ADME) of active pharmaceutical ingredients (APIs) may be altered due to the modulation of their metabolism and transport by excipients. The impact of excipients is a potential concern for Biopharmaceutics Classification System (BCS)-based biowaivers, particularly as the BCS-based biowaivers have been extended to class 3 drugs in certain dosage forms. The presence of different excipients or varying amounts of excipients between formulations may result in bio-inequivalence. The excipient impact may lead to significant variations in clinical outcomes as well. The aim of this paper is to review the recent findings of excipient effects on gastrointestinal (GI) absorption, focusing on their interactions with the metabolic enzymes and transporters in the GI tract. A wide range of commonly used excipients such as binders, diluents, fillers, solvents, and surfactants are discussed here. We summarized the reported effects of those excipients on GI tract phase I and phase II enzymes, uptake and efflux transporters, and relevant clinical significance. This information can enhance our understanding of excipient influence on drug absorption and is useful in designing pharmacokinetic studies and evaluating the resultant data.

Effect of Absorption Behavior of Solubilizers on Drug Dissolution in the Gastrointestinal Tract: Evaluation Based on In Vivo Luminal Concentration-Time Profile of Cilostazol, a Poorly Soluble Drug, and Solubilizers

The purpose of this study was to evaluate the effect of absorption behavior of solubilizers on drug dissolution in the gastrointestinal tract. After oral administration of FITC-dextran (FD-10), a nonabsorbable marker, and cilostazol (CZ), a low-solubility drug, with or without solubilizers (dimethyl sulfoxide [DMSO], and d-α-tocopherol polyethylene glycol 1000 succinate [TPGS]), the in vivo rat luminal concentrations of these compounds were determined by direct sampling of residual water in each segment of the gastrointestinal tract. DMSO was rapidly absorbed and not detected in the middle small intestine. Conversely, the TPGS concentration increased by 1.5- and 2-fold relative to the initial dose concentration in the middle and lower small intestine, respectively, owing to condensation. Then, normalized area under the luminal concentration-time curve of solid CZ was calculated from the luminal concentration-time profiles of FD-10 and solid CZ to evaluate in vivo dissolution behavior of CZ. The dissolution of CZ was marked when administered with TPGS compared with that when administered with DMSO, especially in the lower small intestine. This clearly indicates that absorbability of solubilizers is one of the important factors in determining the solubilizing effect. These findings may be beneficial to development of oral lipophilic drugs.

Diblock- and triblock-copolymer based mixed micelles with high tumor penetration in vitro and in vivo

A series of self-assembled mixed micelles composed of TPGS and Pluronics were fabricated and their cellular uptake and exocytosis behaviors were studied in 2D cell and 3D tumor spheroid models.