Lipid-based delivery systems and intestinal lymphatic drug transport: a mechanistic update

Effects of the solid lipid nanoparticle of carvacrol on rodents with lung injury from smoke inhalation

The aim of this present study was to evaluate the effect of solid lipid nanoparticles (SLN) containing carvacrol over the lung damage of airway smoke inhalation. The study was conducted with 30 rats subjected to smoke inhalation and divided into 5 groups such as, normal control, negative control, oxygen group, SLN alone, and SLN+CARV group. The animals were sacrificed 24 h after the induction of inhalation injury further, the tissues of larynx, trachea, and lungs were collected for the histological, hematological, myeloperoxidase, and malondialdehyde analysis. The obtained results showed that treatment with CARV+SLN minimized the inhalation injury, since it reduced malondialdehyde significantly, when compared to the negative control group and minimized the histological changes which proves the absence of pulmonary emphysema and exudate in laryngeal and tracheal lumen in the CARV+SLN-treated group. Meanwhile, the presence of lesion with chronic characteristics was observed in the negative control and oxygen groups. It is suggested that the SLN containing carvacrol minimized oxidative stress and histological damages generated from smoke inhalation in rodents.

Self-emulsifying drug delivery systems: In vivo evaluation of their potential for oral vaccination

Oral Immunization remains a challenge as antigens are rapidly metabolized in the gastrointestinal tract. In numerous previous studies, Self-emulsifying drug delivery systems (SEDDS) have demonstrated to be a promising tool for oral delivery of biologics. In this study, the potential of SEDDS as vehicle for oral vaccination has been evaluated. At this purpose, the model antigen Bovine serum albumin (BSA) has been incorporated in SEDDS after ion pairing. Squalane and monophosphoryl lipid A (MPLA) were chosen as adjuvants and dissolved in SEDDS containing BSA (SEDDS-BSA-squalane and SEDDS-BSA-MPLA). Formulations were administered orally to BALB/c mice. As control unformulated BSA was administrated orally (BSA-oral) and subcutaneously (BSA-sc). Systemic (anti BSA IgG titre) and mucosal (anti BSA IgA titre) immugenicity of BSA loaded in SEDDS and of unformulated BSA administered orally and subcutaneously was assessed and compared with each other. SEDDS-BSA-squalane and SEDDS-BSA-MPLA induced both higher anti BSA-IgG titre and anti BSA-IgA titre than orally administered unformulated BSA. BSA-sc induced the highest systemic immune response, however, the highest mucosal immune response was achieved via oral administration of SEDDS-BSA-squalane and SEDDS-BSA-MPLA. In general, SEDDS-BSA-MPLA showed the most promising systemic and mucosal immune response. According to these results, SEDDS seems to be a promising carrier for oral delivery of vaccines. STATEMENT OF SIGNIFICANCE: Oral vaccination is still a great challenge, as orally administered antigens are easily degraded in the gastrointestinal (GI) tract by peptidases and proteases. During the last years, self-emulsifying drug delivery systems (SEDDS) consisting of a mixture of oils and surfactants have been developed for the oral administration of hydrophilic macromolecular drugs. In this study, Bovine serum albumin (BSA) was chosen as model antigen and incorporated into self-emulsifying drug delivery systems (SEDDS) after hydrophobic ion pairing. Lipid A from Salmonella Minnesota R595 (MPLA) and squalane were chosen as adjuvants. SEDDS-BSA-MPLA and SEDDS-BSA-squalane were administered orally to mice. SEDDS-BSA-MPLA induced the strongest systemic (anti BSA-IgG titre) and mucosal (anti BSA-IgA titre) immune response. Based on these results, SEDDS are a promising alternative carrier for oral vaccine delivery.

Comparisons of in vitro Fick's first law, lipolysis, and in vivo rat models for oral absorption on BCS II drugs in SNEDDS

Purpose

The objective of this study was to compare the in vitro Fick’s first law, in vitro lipolysis, and in vivo rat assays for oral absorption of Biopharmaceutical Classification Systems Class II (BCS II) drugs in self-nanoemulsifying drug delivery system (SNEDDS), and studied drugs and oils properties effects on the absorption.

Methods

The transport abilities of griseofulvin (GRI), phenytoin (PHE), indomethacin (IND), and ketoprofen (KET) in saturated water solutions and SNEDDS were investigated using the in vitro Madin-Darby canine kidney cell model. GRI and cinnarizine (CIN) in medium-chain triglycerides (MCT)-SNEDDS and long-chain triglycerides (LCT)-SNEDDS were administered in the in vivo SD rat and in vitro lipolysis models to compare the oral absorption and the distribution behaviors in GIT and build an in vitro-in vivo correlation (IVIVC).

Results

In the cell model, the solubility of GRI, PHE, IND, and KET increased 6–8 fold by SNEDDS, but their permeability were only 18%, 4%, 8%, and 33% of those of their saturated water solutions, respectively. However, in vivo absorption of GRI-SNEDDS was twice that of the GRI suspension and those of CIN-SNEDDS were 15–21 fold those of the CIN suspension. In the lipolysis model, the GRI% in aqueous and pellet phases of MCT were similar to that in LCT. In contrast, the CIN% in the aqueous and pellet phases were decreased but that of the lipid phase increased. In addition, an IVIVC was found between the CIN% in the lipid phase and in vivo relative oral bioavailability (F_r).

Conclusion

The in vitro cell model was still a suitable tool to study drug properties effects on biofilm transport and SNEDDS absorption mechanisms. The in vitro lipolysis model provided superior oral absorption simulation of SNEDDS and helped to build correlation with in vivo rats. The oral drug absorption was affected by drug and oil properties in SNEDDS.

Successful oral delivery of poorly water-soluble drugs both depends on the intraluminal behavior of drugs and of appropriate advanced drug delivery systems

Poorly water-soluble drugs continue to be a problematic, yet important class of pharmaceutical compounds for treatment of a wide range of diseases. Their prevalence in discovery is still high, and their development is usually limited by our lack of a complete understanding of how the complex chemical, physiological and biochemical processes that occur between administration and absorption individually and together impact on bioavailability. This review defines the challenge presented by these drugs, outlines contemporary strategies to solve this challenge, and consequent in silico and in vitro evaluation of the delivery technologies for poorly water-soluble drugs. The next steps and unmet needs are proposed to present a roadmap for future studies for the field to consider enabling progress in delivery of poorly water-soluble compounds.

Formulating a single thioether-bridged oleate prodrug into a self-nanoemulsifying drug delivery system to facilitate oral absorption of docetaxel

Oral chemotherapy of docetaxel (DTX) is restricted by active P-glycoprotein (P-gp) efflux, hepatic first-pass metabolism and then poor oral absorption. Herein, a lipophilic thioether-bridged oleate prodrug (DTX-S-OA) and an ester-bond linked oleate prodrug of docetaxel (DTX-OA) were synthesized and efficiently incorporated into a self-nanoemulsifying drug delivery system (SNEDDS) using core-matching technology with a high drug-loading rate. DTX-S-OA SNEDDS produced a uniform droplet size of about 30 nm and a significantly high drug loading capability (60 mg mL-1), compared with DTX SNEDDS (20 mg mL-1). Additionally, DTX-S-OA SNEDDS exhibited a markedly slower drug release property and higher (>2-fold) drug solubilization in the aqueous phase after 60 min lipolysis compared with DTX SNEDDS. In situ single-pass intestinal perfusion and intestinal biodistribution studies demonstrated that the membrane permeability and intestinal bioadhesion of SNEDDS were significantly increased. Moreover, DTX-S-OA showed a comparable ability with verapamil in inhibiting P-gp efflux. Lymphatic transport studies confirmed that DTX-S-OA SNEDDS could significantly enhance intestinal lymphatic transport. Notably, the bioavailability of DTX-S-OA SNEDDS was 6.2-fold and 2.0-fold higher than that of the DTX solution and DTX SNEDDS, respectively. Furthermore, DTX-S-OA achieved a more rapid release of free DTX from the prodrug in systemic circulation than DTX-OA. Therefore, such a unique combination strategy of the single thioether-bridged DTX-oleate prodrug and SNEDDS is a promising platform to enable effective oral delivery of DTX.

Solid lipid matrix mediated nanoarchitectonics for improved oral bioavailability of drugs

Introduction: Solid matrix mediated lipid nanoparticle formulations (LNFs) retain some of the best features of ideal drug carriers necessary for improving the oral absorption and bioavailability (BA) of both hydrophilic and hydrophobic drugs. LNFs with solid matrices may be typically categorized into three major types of formulations, viz., solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs) and lipid-drug conjugate nanoparticles (LDC-NPs). Solid matrix based LNFs are, potentially, the most appropriate delivery systems for poorly water soluble drugs in need of improved drug solubility, permeability, absorption, or increased oral BA. In addition, LNFs as matrices are able to encapsulate both hydrophobic and hydrophilic drugs in a single matrix based on their excellent ability to form cores and shells. Interestingly, LNFs also act as delivery devices to impart chemical stability to various orally administered drugs. Areas covered: Aim of the review is to forecast the presentation of pharmacokinetic characteristics of solid lipid matrix based nanocarriers which are typically biocompatible, biodegradable and non-toxic carrier systems for efficient oral delivery of various drugs. Efficient delivery is broadly mediated by the fact that lipophilic drugs are readily soluble in lipidic substrates that are capable of permeating across the gut epithelium following oral administration, subsequently delivering the moiety of interest more efficiently across the gut mucosal membrane. This enhances the overall BA of many drugs facing oral delivery challenges by improving their pharmacokinetic profile. This article specifically focuses on the biopharmaceutical and pharmacokinetic aspects of such solid lipid matrix based nanoformulations and possible mechanisms for better drug absorption and improved BA following oral administration. It also briefly reviews methods to access the efficacy of LNFs for improving oral BA of drugs, regulatory aspects and some interesting lipid-derived commercial formulations, with a concluding remark. Expert opinion: LNFs enhance the overall BA of many drugs facing oral delivery challenges by improving their pharmacokinetic profile.

The mechanisms of pharmacokinetic food-drug interactions - A perspective from the UNGAP group

The simultaneous intake of food and drugs can have a strong impact on drug release, absorption, distribution, metabolism and/or elimination and consequently, on the efficacy and safety of pharmacotherapy. As such, food-drug interactions are one of the main challenges in oral drug administration. Whereas pharmacokinetic (PK) food-drug interactions can have a variety of causes, pharmacodynamic (PD) food-drug interactions occur due to specific pharmacological interactions between a drug and particular drinks or food. In recent years, extensive efforts were made to elucidate the mechanisms that drive pharmacokinetic food-drug interactions. Their occurrence depends mainly on the properties of the drug substance, the formulation and a multitude of physiological factors. Every intake of food or drink changes the physiological conditions in the human gastrointestinal tract. Therefore, a precise understanding of how different foods and drinks affect the processes of drug absorption, distribution, metabolism and/or elimination as well as formulation performance is important in order to be able to predict and avoid such interactions. Furthermore, it must be considered that beverages such as milk, grapefruit juice and alcohol can also lead to specific food-drug interactions. In this regard, the growing use of food supplements and functional food requires urgent attention in oral pharmacotherapy. Recently, a new consortium in Understanding Gastrointestinal Absorption-related Processes (UNGAP) was established through COST, a funding organisation of the European Union supporting translational research across Europe. In this review of the UNGAP Working group "Food-Drug Interface", the different mechanisms that can lead to pharmacokinetic food-drug interactions are discussed and summarised from different expert perspectives.

Development of a New Ex Vivo Lipolysis-Absorption Model for Nanoemulsions

The use of lipid-based formulations (LBFs) in improving the absorption of poorly water-soluble drugs has now well established. Because the in vivo evaluation of LBFs is labor-intensive, in vitro or ex vivo approaches could provide advantages. In this study, a new ex vivo lipolysis-absorption model (evLAM) composed of an intestinal digestion system and an intestinal tissue system was developed to evaluate and predict the in vivo absorption performances of LBFs. Model factors, including the pH of the system and concentrations of d-glucose and pancreatic lipase, were investigated and optimized by a Box-Behnken design. To evaluate this new model, a lipid formulation of indomethacin, which was chosen based on preliminary studies of pseudo-ternary phase diagrams, emulsion droplets, and solubility, was further investigated by an in vivo pharmacokinetic study of rats, the everted gut sac model, and the evLAM, respectively. The absorption percentages obtained from the evLAM were much more similar to the data of rats in vivo than those from the everted gut sac model, showing a preferable in vitro-in vivo correlation (r = 0.9772). Compared with the conventional in vitro and in vivo methods, the evLAM, which allowed precise insights into the in vivo absorption characteristics without much time or a complicated process, could be a better tool for assessing LBFs of poorly water-soluble drugs.

In vitro digestion models to evaluate lipid based drug delivery systems; present status and current trends

During the past two decades, a range of in vitro models simulating the digestion processes occurring in the stomach and small intestine have been developed to characterize lipid based drug delivery systems (LbDDSs). This review describes the presently existing range of in vitro digestion models and their use in the field of oral drug delivery. The models are evaluated in terms of their suitability to assess LbDDSs, and their ability to produce in vitro - in vivo correlations (IVIVCs). While the pH-stat lipolysis model is by far the most commonly utilized in vitro digestion model in relation to characterizing LbDDSs, a series of recent studies have shown a lack of IVIVCs limiting its future use. Presently, no single in vitro digestion model exists which is able to predict the in vivo performance of various LbDDSs. However, recent research has shown the potential of combined digestion-permeation models as well as species specific digestion models.

Molecular physiology of chemical defenses in a poison frog

Poison frogs sequester small molecule lipophilic alkaloids from their diet of leaf litter arthropods for use as chemical defenses against predation. Although the dietary acquisition of chemical defenses in poison frogs is well-documented, the physiological mechanisms of alkaloid sequestration has not been investigated. Here, we used RNA sequencing and proteomics to determine how alkaloids impact mRNA or protein abundance in the Little Devil Frog (Oophaga sylvatica) and compared wild caught chemically defended frogs to laboratory frogs raised on an alkaloid-free diet. To understand how poison frogs move alkaloids from their diet to their skin granular glands, we focused on measuring gene expression in the intestines, skin, and liver. Across these tissues, we found many differentially expressed transcripts involved in small molecule transport and metabolism, as well as sodium channels and other ion pumps. We then used proteomic approaches to quantify plasma proteins, where we found several protein abundance differences between wild and laboratory frogs, including the amphibian neurotoxin binding protein saxiphilin. Finally, because many blood proteins are synthesized in the liver, we used thermal proteome profiling as an untargeted screen for soluble proteins that bind the alkaloid decahydroquinoline. Using this approach, we identified several candidate proteins that interact with this alkaloid, including saxiphilin. These transcript and protein abundance patterns suggest the presence of alkaloids influences frog physiology and that small molecule transport proteins may be involved in toxin bioaccumulation in dendrobatid poison frogs.

Solid Lipid Nanoparticles of Dronedarone Hydrochloride for Oral Delivery: Optimization, In Vivo Pharmacokinetics and Uptake Studies

BACKGROUND

Dronedarone HCl (DRD), owing to its poor aqueous solubility and extensive presystemic metabolism shows low oral bioavailability of about 4% without food, which increases to approximately 15% when administered with a high fat meal.

OBJECTIVE

Solid lipid nanoparticles (SLN) were designed with glyceryl monstearate (GMS) in order to improve oral bioavailability of DRD.

METHODS

Hot homogenization followed by probe sonication was used to prepare SLN dispersions. Box-Behnken design was used to optimize manufacturing conditions. SLN were characterized for particle size, zeta potential, entrapment efficiency, physical state and in vitro drug release. Pharmacokinetics and intestinal uptake study of dronedarone HCl loaded solid lipid nanoparticles (DRD-SLN) in the presence and absence of endocytic uptake inhibitor, chlorpromazine (CPZ) was performed with conscious male Wistar rats.

RESULTS

Optimized formulation of SLN showed particle size of 233 ± 42 nm and entrapment efficiency of 87.4 ± 1.29%. Results of pharmacokinetic studies revealed enhancement of bioavailability of DRD by 2.68 folds from SLN as compared to DRD suspension. Significantly reduced bioavailability of DRD-SLNs in the presence of chlorpromazine, demonstrated the role of endocytosis in uptake of SLN formulation.

CONCLUSION

These results indicated that dronedarone HCl loaded SLN could potentially be exploited as a delivery system for improving oral bioavailability by minimizing first pass metabolism.

Basic principles of drug delivery systems - the case of paclitaxel

Cancer is the second cause of death worldwide, exceeded only by cardiovascular diseases. The prevalent treatment currently used against metastatic cancer is chemotherapy. Among the most studied drugs that inhibit neoplastic cells from acquiring unlimited replicative ability (a hallmark of cancer) are the taxanes. They operate via a unique molecular mechanism affecting mitosis. In this review, we show this mechanism for one of them, paclitaxel, and for other (non-taxanes) anti-mitotic drugs. However, the use of paclitaxel is seriously limited (its bioavailability is <10%) due to several long-standing challenges: its poor water solubility (0.3 μg/mL), its being a substrate for the efflux multidrug transporter P-gp, and, in the case of oral delivery, its first-pass metabolism by certain enzymes. Adequate delivery methods are therefore required to enhance the anti-tumor activity of paclitaxel. Thus, we have also reviewed drug delivery strategies in light of the various physical, chemical, and enzymatic obstacles facing the (especially oral) delivery of drugs in general and paclitaxel in particular. Among the powerful and versatile platforms that have been developed and achieved unprecedented opportunities as drug carriers, microemulsions might have great potential for this aim. This is due to properties such as thermodynamic stability (leading to long shelf-life), increased drug solubilization, and ease of preparation and administration. In this review, we define microemulsions and nanoemulsions, analyze their pertinent properties, and review the results of several drug delivery carriers based on these systems.

Prospects and Challenges of Phospholipid-Based Prodrugs

Nowadays, the prodrug approach is used already at the early stages of drug development. Lipidic prodrug approach is a growing field for improving a number of drug properties/delivery/therapy aspects, and can offer solutions for various unmet needs. This approach includes drug moiety bound to the lipid carrier, which can be triglyceride, fatty acids, steroid, or phospholipid (PL). The focus of this article is PL-based prodrugs, which includes a PL carrier covalently bound to the active drug moiety. An overview of relevant physiological lipid processing pathways and absorption barriers is provided, followed by drug delivery/therapeutic application of PL-drug conjugates, as well as computational modeling techniques, and a modern bioinformatics tool that can aid in the optimization of PL conjugates. PL-based prodrugs have increased lipophilicity comparing to the parent drug, and can therefore significantly improve the pharmacokinetic profile and overall bioavailability of the parent drug, join the endogenous lipid processing pathways and therefore accomplish drug targeting, e.g., by lymphatic transport, drug release at specific target site(s), or passing the blood-brain barrier. Moreover, an exciting gateway for treating inflammatory diseases and cancer is presented, by utilizing the PL sn-2 position in the prodrug design, aiming for PLA₂-mediated activation. Overall, a PL-based prodrug approach shows great potential in improving different drug delivery/therapy aspects, and is expected to grow.

Chylomicron-pretended nano-bio self-assembling vehicle to promote lymphatic transport and GALTs target of oral drugs

Lymphatic transport of oral drugs allows extraordinary gains in bioavailability and efficacy through avoidance of first-pass hepatic metabolism and preservation of drugs at lymphatic tissues against lymph-mediated diseases. Chylomicrons can transport dietary lipids absorbed from the intestine to the tissues through lymphatic circulation. Herein, we engineered for the first time a chylomicron-pretended mesoporous silica nanocarrier that utilizes the digestion, re-esterification, and lymphatic transport process of dietary triglyceride to promote lymphatic transport of oral drugs. Taking lopinavir (LNV) as a model antiretroviral drug with disadvantages such as poor solubility, high first-pass effect and off-target deposition, this vehicle exhibited several properties belonging to ideal nanocarriers, including high drug load, amorphous dispersion and controlled release in the gastrointestinal tract. Additionally, a nano-bio interaction was demonstrated between nanoparticles and a key protein involved in chylomicron assembly; this biochemical reaction in cellular was utilized for the first time to promote lymphatic transport of nanocarriers for oral delivery. As a result, the chylomicron-pretended nanocarrier afforded 10.6-fold higher oral bioavailability compared with free LNV and effectively delivered LNV to gut-associated lymphoid tissues, where HIV persists and actively evolves. This approach not only promises a potential application to HIV-infected individuals but also opens a new avenue to other lymph-mediated pathologies such as autoimmune diseases and lymphatic tumor metastasis.

Nanoemulsion-Enabled Oral Delivery of Novel Anticancer ω-3 Fatty Acid Derivatives

Lipid-based drugs are emerging as an interesting class of novel anticancer drugs with the potential to target specific cancer cell metabolic pathways linked to their proliferation and invasiveness. In particular, ω-3 polyunsaturated fatty acids (PUFA) derivatives such as epoxides and their bioisosteres have demonstrated the potential to suppress growth and promote apoptosis in triple-negative human breast cancer cells MDA-MB-231. In this study, 16-(4′-chloro-3′-trifluorophenyl)carbamoylamino]hexadecanoic acid (ClFPh-CHA), an anticancer lipid derived from ω-3,17,18-epoxyeicosanoic acid, was formulated as a stable nanoemulsion with size around 150 nm and narrow droplet size distribution (PDI < 0.200) through phase-inversion emulsification process followed by high pressure homogenization in view of an oral administration. The ClFPh-CHA-loaded nanoemulsions were able to significantly decrease the relative tumor volume in mice bearing an intramammary tumor xenograft at all doses tested (2.5, 10 and 40 mg/kg) after 32 days of daily oral administration. Furthermore, absolute tumor weight was decreased to 50% of untreated control at 10 and 40 mg/kg, while intraperitoneal administration could achieve a significant reduction only at the highest dose of 40 mg/kg. Results suggest that oral administration of ClFPh-CHA formulated as a nanoemulsion has a sufficient bioavailability to provide an anticancer effect in mice and that the activity is at least equal if not superior to that obtained by a conventional parenteral administration of equivalent doses of the same drug.

Lipophilic activated ester prodrug approach for drug delivery to the intestinal lymphatic system

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

HIV RNA persists in rectal tissue despite rapid plasma virologic suppression with dolutegravir-based therapy

OBJECTIVES

Despite plasma virologic suppression with antiretroviral therapy (ART), HIV persists in gut tissue. The objectives of this study were to compare plasma and rectal tissue HIV RNA dynamics and to assess relationships with dolutegravir (DTG) plasma and tissue concentrations.

DESIGN

A longitudinal cohort study of HIV-infected treatment-naïve individuals initiating DTG-based ART was conducted over 12 weeks with plasma and rectal tissue sampling (Clinicaltrials.gov:NCT02924389).

METHODS

HIV RNA and DTG concentrations were quantified in plasma and rectal tissue samples collected pre-ART (baseline) and post-ART at weeks 2, 6, and 12 using Abbott Real-Time HIV-1 assays and high-performance liquid chromatography tandem mass spectroscopy, respectively. Relationships between rectal tissue RNA and DTG concentrations were modeled using binary logistic regression, controlling for repeated measures.

RESULTS

Twelve participants were enrolled: six (50.0%) women, nine (75.0%) black, median age 42.0 years (Q1 31.2, Q3 52.0). All attained plasma virologic suppression by week 6. 11 of 12 (91.7%) had detectable rectal tissue HIV RNA at baseline, and only three of 11 (27.3%) achieved rectal tissue virologic suppression at any time-point. Compared with rectal tissue nonsuppressors, three of three (100.0%) of rectal tissue suppressors were women, had higher BMI, 35.9 kg/m (range 24.9-38.5) versus 20.6 (17.7-29.9), P = 0.05, and lower baseline log plasma HIV RNA: 3.7 copies/ml (range 3.6-4.4) versus 4.7 (3.8-5.4), P = 0.02. No significant relationships between rectal tissue RNA suppression and DTG concentrations were seen.

CONCLUSION

Rectal tissue HIV RNA persisted in most participants and was not predicted by DTG concentrations. Impact of host factors, particularly sex, on tissue HIV viral dynamics warrants further exploration.

Soft- and hard-lipid nanoparticles: a novel approach to lymphatic drug delivery

With the current advance in nanotechnology, the development has accelerated of a number of nanoparticle-type drugs such as nano-emulsions, lipid emulsions, liposomes, and cell therapeutics. With these developments, attempts are being made to apply these new drugs to healing many intractable diseases related to antibody production, autoimmune disorders, cancer, and organ transplantation in both clinical and nonclinical trials. Drug delivery to the lymphatic system is indispensable for treating these diseases, but the core technologies related to the in vivo distribution characteristics and lymphatic delivery evaluation of these particle-type drugs have not yet been established. Additionally, the core technologies for setting up the pharmacotherapeutic aspects such as their usage and dosages in the development of new drugs do not meet the needs of the market. Therefore, it is necessary to consider dividing these particle-type drugs into soft-lipid nanoparticles that can change size in the process of body distribution and hard-lipid nanoparticles whose surfaces are hardened and whose sizes do not easily change in vivo; these soft- and hard-lipid nanoparticles likely possess different biodistribution characteristics including delivery to the lymphatic system. In this review, we summarize the different types, advantages, limitations, possible remedies, and body distribution characteristics of soft- and hard-lipid nanoparticles based on their administration routes. We also emphasize that it will be necessary to fully understand the differences in distribution between these soft- and hard-lipid nanoparticle-type drugs and to establish pharmacokinetic models for their more ideal lymphatic delivery.

In situ monitoring of the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET

Microemulsions are promising drug delivery systems for the oral administration of poorly water-soluble drugs. However, the evolution of microemulsions in the gastrointestinal tract is still poorly characterized, especially the structural change of microemulsions under the effect of lipase and mucus. To better understand the fate of microemulsions in the gastrointestinal tract, we applied small-angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET) to monitor the structural change of microemulsions under the effect of lipolysis and mucus. First, the effect of lipolysis on microemulsions was studied by SAXS, which found the generation of liquid crystalline phases. Meanwhile, FRET spectra indicated micelles with smaller particle sizes were generated during lipolysis, which could be affected by CaCl2, bile salts and lecithin. Then, the effect of mucus on the structural change of lipolysed microemulsions was studied. The results of SAXS and FRET indicated that the liquid crystalline phases disappeared, and more micelles were generated. In summary, we studied the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET, and successfully monitored the appearance and disappearance of the liquid crystalline phases and micelles.

A novel core-shell lipid nanoparticle for improving oral administration of water soluble chemotherapeutic agents: inhibited intestinal hydrolysis and enhanced lymphatic absorption

The oral administration of water-soluble chemotherapeutical agents is limited by their serious gastrointestinal side effects, instability at intestinal pH, and poor absorption. Aiming to solve these problems, we chose topotecan (TPT) as a model drug and developed a novel lipid formulation containing core-shell lipid nanoparticle (CLN) that makes the water-soluble drug to ‘dissolve’ in oil. TPT molecules can be encapsulated into nanoparticles surrounded by oil barrier while avoiding the direct contact with intestinal environment, thus easing the intestinal hydrolytic degradation and gastrointestinal (GI) irritation. Microstructure and mean particle size of TPT-CLN were characterized by Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS), respectively. The average size of nanoparticles was approximately 60 nm with a homogeneous distribution in shapes of spheres or ellipsoid. According to in vitro stability studies, more initial form of TPT was observed in presence of lipid nanoparticle compared with free topotecan solution in artificial intestinal juice (pH 6.5). After oral administration of TPT-CLN in rats, AUC and C_max of TPT were all increased compared with free TPT, indicating significant enhancement of oral absorption. Intestinal lymphatic transport was confirmed as the major way for CLN to enhance oral absorption of TPT by the treatment of blocking chylomicron flow. Lower GI irritation of TPT-CLN was observed in the gastrointestinal damage studies. The in vivo antitumor activity of TPT-CLN showed an improved antitumor efficacy by oral treatment of TPT-CLN compared to free TPT. From the obtained data, the systems appear an attractive progress in oral administration of topotecan.

The combination of endolysosomal escape and basolateral stimulation to overcome the difficulties of "easy uptake hard transcytosis" of ligand-modified nanoparticles in oral drug delivery

Ligand-modified nanoparticles (NPs) are an effective tool to increase the endocytosis efficiency of drugs, but these functionalized NPs face the drawback of "easy uptake hard transcytosis" in the oral delivery of proteins and peptides. Adversely, the resulting deficiency in transcytosis has not attracted much attention. Herein, NPs modified with the low-density lipoprotein receptor (LDLR) ligand NH₂-C6-[cMPRLRGC]c-NH₂, i.e., peptide-22 (P22NPs) were fabricated to investigate strategies related to the enhancement of transcytosis. By systematically studying the intracellular trafficking of NPs, it was found that reduced transcytosis might be associated with the entrapment of P22NPs in endosomes or lysosomes and limited basolateral exocytosis. On this basis, the prevention of the endolysosomal entrapment of NPs and the acceleration of basolateral exocytosis should be considered as strategies to enhance the transcytosis of NPs. By screening chemicals that could help the endosomal/lysosomal escape of chemicals related to LDLR-mediated transcytosis, it was shown that hemagglutinin-2 (HA₂) and metformin had higher abilities to enhance the exocytosis of P22NPs. The transcytosis efficiencies of insulin loaded in P22NPs were also investigated, and a 3.2-fold increase in transcytosis was observed in comparison with free insulin. The transcytosis efficiencies of insulin could be further increased by the addition of metformin or HA₂ (3.6-fold or 4.1-fold higher than that of free insulin). Inspiringly, the simultaneous addition of the abovementioned two chemicals led to the highest transcytosis efficiency of insulin, which was up to 5.1-fold higher than that of free insulin. These results demonstrated that endolysosomal entrapment and basolateral exocytosis are two of the most important limiting steps for the "easy uptake hard transcytosis" of orally administered ligand-modified NPs. Moreover, our work provides a new point of view for the design of novel oral drug delivery systems.

Challenges and trends in apomorphine drug delivery systems for the treatment of Parkinson's disease

Parkinson's disease (PD) is a chronic debilitating disease affecting approximately 1% of the population over the age of 60. The severity of PD is correlated to the degree of dopaminergic neuronal loss. Apomorphine has a similar chemical structure as the neurotransmitter dopamine and has been used for the treatment of advanced PD patients. In PD patients, apomorphine is normally administered subcutaneously with frequent injections because of the compound's extensive hepatic first-pass metabolism. There is, hence, a large unmet need for alternative administrative routes for apomorphine to improve patient compliance. The present review focuses on the research and development of alternative delivery of apomorphine, aiming to highlight the potential of non-invasive apomorphine therapy in PD, such as sublingual delivery and transdermal delivery.

A new lipid formulation of low dose ibuprofen shows non-inferiority to high dose standard ibuprofen: the FLARE study (flaring arthralgia relief evaluation in episodic flaring knee pain) - a randomised double-blind study

OBJECTIVE

To investigate short-term efficacy and safety of a novel lipid ibuprofen formulation 1200 mg/day compared with standard ibuprofen 1200 mg/day and 2400 mg/day in episodic knee arthralgia/flaring pain.

DESIGN

Multicentre, randomised, double-blind, 3-arm, non-inferiority trial conducted at 27 primary care centres. Adults with ≥1 knee flare episode within 12 months were recruited within 24 h of new flare with pain severity ≥5 on a 0-10 numerical rating scale (NRS). Primary outcome was change from baseline in WOMAC pain subscale over 5 days. Main secondary outcome was Gastrointestinal Symptom Rating Scale (GSRS) change from baseline. Other endpoints included assessment of WOMAC total subscale scores and self-reported NRS for pain, subject nominated activity, stiffness and swelling.

RESULTS

462 patients were enrolled (58.9% males; mean age 52.2 years). Treatment allocation comprised 148 lipid 1200 mg, 155 soft-gel 1200 mg, 159 soft-gel 2400 mg. WOMAC pain subscale scores decreased in all groups, with lipid 1200 mg being non-inferior to soft-gel 1200 mg (adjusted mean difference -0.26 [95% confidence interval [CI] -0.69, 0.17]) and to soft-gel 2400 mg (difference 0.19 [95% CI -0.24, 0.62]). No differences were seen in mean GSRS total scores. NRS secondary endpoints suggested greater improvements in the lipid 1200 mg group compared to soft-gel 1200 mg, with similar results to soft-gel 2400 mg. The most frequent drug-related adverse events (AEs) were gastrointestinal (GI) disorders, with statistically fewer events for lipid 1200 mg vs soft-gel 2400 mg (P = 0.01, post-hoc analysis).

CONCLUSIONS

Ibuprofen 1200 mg/day lipid formulation was non-inferior to standard ibuprofen soft-gel capsules 1200 mg and 2400 mg/day in relieving flaring knee pain. NRS endpoints showed lipid 1200 mg was numerically similar to soft-gel 2400 mg.

TRIAL REGISTRATION NUMBER

EudraCT number: 2014-004254-33.

Solid lipid nanoparticles as carriers for oral delivery of hydroxysafflor yellow A

Hydroxysafflor yellow A (HSYA) is the main bioactive flavonoid extracted from the flower of Carthamus tinctorius L., which is widely used in traditional Chinese medicine for the treatment of myocardial ischemia and cerebral ischemia. HSYA has high water solubility but poor intestinal membrane permeability, resulting in low oral bioavailability. Currently, only HSYA sodium chloride injection has been approved for clinical use and oral formulations are urgently needed. In this study, HSYA solid lipid nanoparticles (SLNs) with the structure of w/o/w were prepared by a warm microemulsion process using approved drug excipients for oral delivery to increase the oral absorption of HSYA. The optimized HSYA SLNs are spherical with an average size of 214nm and the encapsulation efficiency is 55%. HSYA SLNs exhibited little cytotoxicity in Caco-2 and Hela cells, but increased the oral absorption of HSYA about 3.97-fold in rats, compared to HSYA water solution. In addition, cycloheximide pretreatment significantly decreased the oral absorption of HSYA delivered by SLNs. Importantly, the pharmacodynamics evaluation demonstrated that SLNs further decreased the infarct areas in rats. In conclude, SLNs could be a promising delivery system to enhance the oral absorption and pharmacological activities of HSYA.

Review and analysis of FDA approved drugs using lipid-based formulations

Lipid-based drug delivery systems (LBDDS) are one of the most studied bioavailability enhancement technologies and are utilized in a number of U.S. Food and Drug Administration (FDA) approved drugs. While researchers have used several general rules of thumb to predict which compounds are likely to benefit from LBDDS, formulation of lipid systems is primarily an empiric endeavor. One of the challenges is that these rules of thumb focus in different areas and are used independently of each other. The Developability Classification System attempts to link physicochemical characteristics with possible formulation strategies. Although it provides a starting point, the formulator still has to empirically develop the formulation. This article provides a review and quantitative analysis of the molecular properties of these approved drugs formulated as lipid systems and starts to build an approach that provides more directed guidance on which type of lipid system is likely to be the best for a particular drug molecule.

Self-Assembled Lipid Nanoparticles for Oral Delivery of Heparin-Coated Iron Oxide Nanoparticles for Theranostic Purposes

Recently, solid lipid nanoparticles (SLNs) have attracted increasing attention owing to their potential as an oral delivery system, promoting intestinal absorption in the lymphatic circulation which plays a role in disseminating metastatic cancer cells and infectious agents throughout the body. SLN features can be exploited for the oral delivery of theranostics. Therefore, the aim of this work was to design and characterise self-assembled lipid nanoparticles (SALNs) to encapsulate and stabilise iron oxide nanoparticles non-covalently coated with heparin (Fe@hepa) as a model of a theranostic tool. SALNs were characterised for physico-chemical properties (particle size, surface charge, encapsulation efficiency, in vitro stability, and heparin leakage), as well as in vitro cytotoxicity by methyl thiazole tetrazolium (MTT) assay and cell internalisation in CaCo-2, a cell line model used as an indirect indication of intestinal lymphatic absorption. SALNs of about 180 nm, which are stable in suspension and have a high encapsulation efficiency (>90%) were obtained. SALNs were able to stabilise the heparin coating of Fe@hepa, which are typically unstable in physiological environments. Moreover, SALNs–Fe@hepa showed no cytotoxicity, although their ability to be internalised into CaCo-2 cells was highlighted by confocal microscopy analysis. Therefore, the results indicated that SALNs can be considered as a promising tool to orally deliver theranostic Fe@hepa into the lymphatic circulation, although further in vivo studies are needed to comprehend further potential applications.

Impact of Lipid Phase on the Bioavailability of Vitamin E in Emulsion-Based Delivery Systems: Relative Importance of Bioaccessibility, Absorption, and Transformation

A simulated gastrointestinal tract/Caco-2 cell culture model was used to investigate the effects of lipid phase type on vitamin E (VE) bioavailability. Oil-in-water emulsions fortified with α-tocopherol acetate were fabricated using a natural emulsifier (quillaja saponin) and long or medium chain triglycerides (LCTs or MCTs) as lipids. The impact of lipid type on VE bioaccessibility, absorption, and transformation was determined. VE bioaccessibility was greater for LCT (46%) than MCT (19%) due to greater solubilization in mixed micelles assembled from longer fatty acids. VE absorption by Caco-2 cells was similar for LCT (28%) and MCT (30%). The transformation of α-tocopherol acetate to α-tocopherol was higher for LCT (90%) than MCT (75%) due to differences in esterase accessibility to VE. Emulsion-based delivery systems formulated using LCT are therefore more suitable for encapsulating and delivering vitamin E than those formulated using MCT.

Self-microemulsifying drug delivery system for improving the bioavailability of huperzine A by lymphatic uptake

Huperzine A (Hup-A) is a poorly water-soluble drug with low oral bioavailability. A self-microemulsifying drug delivery system (SMEDDS) was used to enhance the oral bioavailability and lymphatic uptake and transport of Hup-A. A single-pass intestinal perfusion (SPIP) technique and a chylomicron flow-blocking approach were used to study its intestinal absorption, mesenteric lymph node distribution and intestinal lymphatic uptake. The value of the area under the plasma concentration–time curve (AUC) of Hup-A SMEDDS was significantly higher than that of a Hup-A suspension (P<0.01). The absorption rate constant (K_a) and the apparent permeability coefficient (P_app) for Hup-A in different parts of the intestine suggested a passive transport mechanism, and the values of K_a and P_app of Hup-A SMEDDS in the ileum were much higher than those in other intestinal segments. The determination of Hup-A concentration in mesenteric lymph nodes can be used to explain the intestinal lymphatic absorption of Hup-A SMEDDS. For Hup-A SMEDDS, the values of AUC and maximum plasma concentration (C_max) of the blocking model were significantly lower than those of the control model (P<0.05). The proportion of lymphatic transport of Hup-A SMEDDS and Hup-A suspension were about 40% and 5%, respectively, suggesting that SMEDDS can significantly improve the intestinal lymphatic uptake and transport of Hup-A.

Enhancing the Solubility and Oral Bioavailability of Poorly Water-Soluble Drugs Using Monoolein Cubosomes

Monoolein cubosomes containing either spironolactone (SPI) or nifedipine (NI) were prepared using a high-pressure homogenization technique and characterized in terms of their solubility and oral bioavailability. The mean particle size, polydispersity index (PDI), zeta potential, solubility and encapsulation efficiency (EE) values of the SPI- and NI-loaded cubosomes were determined to be 90.4 nm, 0.187, -13.4 mV, 163 µg/mL and 90.2%, and 91.3 nm, 0.168, -12.8 mV, 189 µg/mL and 93.0%, respectively, which were almost identical to those of the blank cubosome. Small-angle X-ray scattering analyses confirmed that the SPI-loaded, NI-loaded and blank cubosomes existed in the cubic space group Im3̄m. The lattice parameters of the SPI- and NI-loaded cubosomes were 147.6 and 151.6 Å, respectively, making them almost identical to that of blank cubosome (151.0 Å). The in vitro release profiles of the SPI- and NI-loaded cubosomes showed that they released less than 5% of the drugs into various media over 12-48 h, indicating that most of the drug remained encapsulated within the cubic phase of their lipid bilayer. Furthermore, the in vivo pharmacokinetic results suggested that these cubosomes led to a considerable increase in the systemic oral bioavailability of the drugs compared with pure dispersions of the same materials. Notably, the stability results indicated that the mean particle size and PDI values of these cubosomes were stable for at least 4 weeks. Taken together, these results demonstrate that monoolein cubosomes represent promising drug carriers for enhancing the solubility and oral bioavailability of poorly water-soluble drugs.

Solid lipid nanoparticles as vesicles for oral delivery of olmesartan medoxomil: formulation, optimization and in vivo evaluation

OBJECTIVE

Olmesartan medoxomil (OLM) is an antihypertensive drug with low oral bioavailability (28%) resulting from poor aqueous solubility, presystemic metabolism and P-glycoprotein mediated efflux. The present investigation studies the role of lipid nanocarriers in enhancing the OLM bioavailability through oral delivery.

MATERIALS AND METHODS

Solid lipid nanoparticles (SLN) were prepared by solvent emulsion-evaporation method. Statistical tools like regression analysis and Pareto charts were used to detect the important factors effecting the formulations. Formulation and process parameters were then optimized using mean effect plot and contour plots. The formulations were characterized for particle size, size distribution, surface charge, percentage of drug entrapped in nanoparticles, drug-excipients interactions, powder X-ray diffraction analysis and drug release in vitro.

RESULTS AND DISCUSSION

The optimized formulation comprised glyceryl monostearate, soya phosphatidylcholine and Tween 80 as lipid, co-emulsifier and surfactant, respectively, with an average particle size of 100 nm, PDI 0.291, zeta potential of -23.4 mV and 78% entrapment efficiency. Pharmacokinetic evaluation in male Sprague Dawley rats revealed 2.32-fold enhancement in relative bioavailability of drug from SLN when compared to that of OLM plain drug on oral administration.

CONCLUSION

In conclusion, SLN show promising approaches as a vehicle for oral delivery of drugs like OLM.

Lipid-based nanocarriers for the oral administration of biopharmaceutics

Biopharmaceutics have been recognized as the drugs of choice for the treatment of several diseases, mainly due to their high selectivity and potent action. Nonetheless, their oral administration is a rather challenging problem, since their bioavailability is significantly hindered by various physiological barriers along the GI tract, including their acid-induced hydrolysis in the stomach, their enzymatic degradation throughout the GI tract and their poor mucosa permeability. Lipid-based nanocarriers represent a viable means for enhancing the oral bioavailability of biomolecules while diminishing toxicity-related issues. The present review describes the main physiological barriers limiting the oral bioavailability of macromolecules and highlights recent advances in the field of lipid-based carriers as well as the respective lipid intestinal absorption mechanisms.

Lipid-associated oral delivery: Mechanisms and analysis of oral absorption enhancement

The majority of newly discovered oral drugs are poorly water soluble, and co-administration with lipids has proven effective in significantly enhancing bioavailability of some compounds with low aqueous solubility. Yet, lipid-based delivery technologies have not been widely employed in commercial oral products. Lipids can impact drug transport and fate in the gastrointestinal (GI) tract through multiple mechanisms including enhancement of solubility and dissolution kinetics, enhancement of permeation through the intestinal mucosa, and triggering drug precipitation upon lipid emulsion depletion (e.g., by digestion). The effect of lipids on drug absorption is currently not quantitatively predictable, in part due to the multiple complex dynamic processes that can be impacted by lipids. Quantitative mechanistic analysis of the processes significant to lipid system function and overall impact on drug absorption can aid in the understanding of drug-lipid interactions in the GI tract and exploitation of such interactions to achieve optimal lipid-based drug delivery. In this review, we discuss the impact of co-delivered lipids and lipid digestion on drug dissolution, partitioning, and absorption in the context of the experimental tools and associated kinetic expressions used to study and model these processes. The potential benefit of a systems-based consideration of the concurrent multiple dynamic processes occurring upon co-dosing lipids and drugs to predict the impact of lipids on drug absorption and enable rational design of lipid-based delivery systems is presented.