Effects of non-ionic surfactants on in vitro triglyceride digestion and their susceptibility to digestion by pancreatic enzymes

Pharmaceutical Nanoplatforms Based on Self-nanoemulsifying Drug Delivery Systems for Optimal Transport and Co-delivery of siRNAs and Anticancer Drugs

Small interfering RNAs (siRNAs) have the ability to induce selective gene silencing, although siRNAs are vulnerable to degradation in vivo. Various active pharmaceutical ingredients (APIs) are currently used as effective therapeutics in the treatment of cancer. However, routes of administration are limited due to their physicochemical and biopharmaceutical properties. This research aimed to develop oral pharmaceutical formulations based on self-nanoemulsifying drug delivery systems (SNEDDS) for optimal transport and co-delivery of siRNAs related to cancer and APIs. Formulations were developed using optimal mixing design (Design-Expert 11 software) for SNEDDS loading with siRNA (water/oil emulsion), API (oil/water emulsion), and siRNA-API (multiphase water/oil/water emulsion). The final formulations were characterized physicochemically and biologically. The nanosystems less than 50 nm in size had a drug loading above 48 %. The highest drug release occurred at intestinal pH, allowing drug protection in physiological fluids. SNEDDS-siRNA-APIs showed a twofold toxicity effect than APIs in solution and higher transfection and internalization of siRNA in cancer cells with respect to free siRNAs. In the duodenum, higher permeability was observed with SNEDDS-API than with the API solution, as determined by ex-vivo fluorescence microscopy. The multifunctional formulation based on SNEDDS was successfully prepared, siRNA, hydrophobic chemotherapeutics (doxorubicin, valrubicin and methotrexate) and photosensitizers (rhodamine b and protoporphyrin IX) agents were loaded, using a chitosan-RNA core, and Labrafil® M 1944 CS, Cremophor® RH40, phosphatidylcholine shell, forming stable hybrid SNEDDS as multiphasic emulsion, suitable as co-delivery system with a potent anticancer activity.

Effect of talc and vitamin E TPGS on manufacturability, stability and release properties of trilaurin-based formulations for hot-melt coating

This study was focused on one particular case of hot-melt coating with trilaurin - a solid medium-chain monoacid triglyceride. The challenge of using trilaurin as coating agent in melting-based processes is linked to its relatively low melting profile: 15.6 °C (Tm,α), 35.1 °C ( [Formula: see text] ) and 45.7 °C (Tm,β). From a process perspective, the only possibility to generate products coated with formulations composed of trilaurin is by setting thermal operational conditions above Tm,α. From a material perspective, this processing possibility depends principally on trilaurin crystallisation which was investigated via a set of analytical techniques including turbidimetry, calorimetry, hot-melt goniometry, and polarised light microscopy. A highly soluble drug model substrate (sodium chloride crystals) was coated with three selected trilaurin-based formulations: (i) trilaurin, (ii) trilaurin plus talc, and (iii) trilaurin plus vitamin E TPGS and talc. Coated salt crystals were then analysed to investigate processing performance, coating quality, stability and release properties under digestion effect. The results show that firstly, talc addition promotes nucleation and crystal growth and, as a consequence, it facilitates the manufacture of trilaurin-based formulations. Secondly, the formulation of a solid triglyceride and a hydrophilic surfactant could potentially cause release instability, but formula (iii) was found to be stabilised by a mechanism whereby trilaurin crystallization enhanced in the presence of talc immobilised vitamin E TPGS in its crystal lattice. Thirdly, talc addition did not significantly influence trilaurin digestion which endows products with an immediate release in lipolytic conditions instead of an extended liberation in pure water. Nor did the addition of one or two additives alter the extent of trilaurin digestion under the conditions studied. These important findings relate to product manufacturability, stability, and release properties. A good understanding of material properties (e.g. crystallisation, polymorphism, digestibility) is essential for melt-processing, lipid coating stabilising and modulation of release profile of solid lipid-coated product, as demonstrated in this case study with trilaurin.

Bilosomes as Nanocarriers for the Drug and Vaccine Delivery against Gastrointestinal Infections: Opportunities and Challenges

The gastrointestinal tract (GIT) environment has an intricate and complex nature, limiting drugs' stability, oral bioavailability, and adsorption. Additionally, due to the drugs' toxicity and side effects, renders are continuously seeking novel delivery systems. Lipid-based drug delivery vesicles have shown various loading capacities and high stability levels within the GIT. Indeed, most vesicular platforms fail to efficiently deliver drugs toward this route. Notably, the stability of vesicular constructs is different based on the different ingredients added. A low GIT stability of liposomes and niosomes and a low loading capacity of exosomes in drug delivery have been described in the literature. Bilosomes are nonionic, amphiphilic, flexible surfactant vehicles that contain bile salts for the improvement of drug and vaccine delivery. The bilosomes' stability and plasticity in the GIT facilitate the efficient carriage of drugs (such as antimicrobial, antiparasitic, and antifungal drugs), vaccines, and bioactive compounds to treat infectious agents. Considering the intricate and harsh nature of the GIT, bilosomal formulations of oral substances have a remarkably enhanced delivery efficiency, overcoming these conditions. This review aimed to evaluate the potential of bilosomes as drug delivery platforms for antimicrobial, antiviral, antifungal, and antiparasitic GIT-associated drugs and vaccines.

Intrinsic lipolysis rate for systematic design of lipid-based formulations

Lipid-based formulations (LBFs) are used by the pharmaceutical industry in oral delivery systems for both poorly water-soluble drugs and biologics. Digestibility is key for the performance of LBFs and in vitro lipolysis is commonly used to compare the digestibility of LBFs. Results from in vitro lipolysis experiments depend highly on the experimental conditions and formulation characteristics, such as droplet size (which defines the surface area available for digestion) and interfacial structure. This study introduced the intrinsic lipolysis rate (ILR) as a surface area-independent approach to compare lipid digestibility. Pure acylglycerol nanoemulsions, stabilized with polysorbate 80 at low concentration, were formulated and digested according to a standardized pH-stat lipolysis protocol. A methodology originally developed to calculate the intrinsic dissolution rate of poorly water-soluble drugs was adapted for the rapid calculation of ILR from lipolysis data. The impact of surfactant concentration on the apparent lipolysis rate and lipid structure on ILR was systematically investigated. The surfactant polysorbate 80 inhibited lipolysis of tricaprylin nanoemulsions in a concentration-dependent manner. Coarse-grained molecular dynamics simulations supported these experimental observations. In the absence of bile and phospholipids, tricaprylin was shielded from lipase at 0.25% polysorbate 80. In contrast, the inclusion of bile salt and phospholipid increased the surfactant-free area and improved the colloidal presentation of the lipids to the enzyme, especially at 0.125% polysorbate 80. At a constant and low surfactant content, acylglycerol digestibility increased with decreasing acyl chain length, decreased esterification, and increasing unsaturation. The calculated ILR of pure acylglycerols was successfully used to accurately predict the IRL of binary lipid mixtures. The ILR measurements hold great promise as an efficient method supporting pharmaceutical formulation scientists in the design of LBFs with specific digestion profiles.

Digestion of lipid excipients and lipid-based nanocarriers by pancreatic lipase and pancreatin

The digestion behaviour of lipid-based nanocarriers (LNC) has a great impact on their oral drug delivery properties. In this study, various excipients including surfactants, glycerides and waxes, as well as various drug-delivery systems, namely self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were examined via the pH-stat lipolysis model. Lipolysis experiments with lipase and pancreatin revealed the highest release of fatty acids for medium chain glycerides, followed by long chain glycerides and surfactants. Waxes appeared to be poor substrates with a maximum digestion of up to 10% within 60 min. Within the group of surfactants, the enzymatic cleavage decreased in the following order: glycerol monostearate > polyoxyethylene (20) sorbitan monostearate > PEG-35 castor oil > sorbitan monostearate. After digestion experiments of the excipients, SEDDS, SLN and NLC with sizes between 30 and 300 nm were prepared. The size of almost all formulations was increasing during lipolysis and levelled off after approximately 15 min except for the SLN and NLC consisting of cetyl palmitate. SEDDS exceeded 6000 nm after some minutes and were almost completely hydrolysed by pancreatin. No significant difference was observed between comparable SLN and NLC but surfactant choice and selection of the lipid component had an impact on digestion. SLN and NLC with cetyl palmitate were only digested by 5% whereas particles with glyceryl distearate were decomposed by 40-80% within 60 min. Additionally, the digestion of the same SLN or NLC, only differing in the surfactant, was higher for SLN/NLC containing polyoxyethylene (20) sorbitan monostearate than PEG-35 castor oil. This observation might be explained by the higher PEG content of PEG-35 castor oil causing a more pronounced steric hindrance for the access of lipase. Generally, digestion experiments performed with pancreatin resulted in a higher digestion compared to lipase. According to these results, the digestion behaviour of LNC depends on both, the type of nanocarrier and on the excipients used for them.

Oil-Based Delivery Control Release System Targeted to the Later Part of the Gastrointestinal Tract-A Mechanistic Study

Oil-based drug delivery systems have been studied in different aspects. The present study proposes a new application for an oil-based delivery system, focusing on controlled release until the drug reaches the later part of the small intestine. Bulk surfactants and interfacial surfactants were added into the oil formulation to provide a better mechanistic understating of the lipolysis. Validation of the modified in vitro method shows the overall conversion from medium-chain triglyceride oil (MCT oil) to free fatty acids (FFA) of 100 ± 4% in five replicates. This fully converted level and high reproducibility are fundamental for the following investigations where any retarding effect can be distinguished from the experimental errors. The results show that viscosity and thermodynamic activity have limited retardation. Furthermore, the former may change the kinetics of lipolysis, while the latter changes the equilibrium level. The gel-forming retarder (ethylcellulose) displayed a strong effect. Whereas the lipolysis was significantly retarded (>50%) when the retarders altered the interfacial composition (poloxamer 407), degradable interfacial surfactants did not have the same effect. However, surface-active, lipolysis-resistant retarders with a high CMC did not show a retarding effect.

Oral delivery of therapeutic peptides and proteins: Technology landscape of lipid-based nanocarriers

The oral administration of therapeutic peptides and proteins is favoured from a patient and commercial point of view. In order to reach the systemic circulation after oral administration, these drugs have to overcome numerous barriers including the enzymatic, sulfhydryl, mucus and epithelial barrier. The development of oral formulations for therapeutic peptides and proteins is therefore necessary. Among the most promising formulation approaches are lipid-based nanocarriers such as oil-in-water nanoemulsions, self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), liposomes and micelles. As the lipophilic character of therapeutic peptides and proteins can be tremendously increased such as by the formation of hydrophobic ion pairs (HIP) with hydrophobic counter ions, they can be incorporated in the lipophilic phase of these carriers. Since gastrointestinal (GI) peptidases as well as sulfhydryl compounds such as glutathione and dietary proteins are too hydrophilic to enter the lipophilic phase of these carriers, the incorporated therapeutic peptide or protein is protected towards enzymatic degradation as well as unintended thiol/disulfide exchange reactions. Stability of lipid-based nanocarriers towards lipases can be provided by the use to excipients that are not or just poorly degraded by these enzymes. Nanocarriers with a size <200 nm and a mucoinert surface such as PEG or zwitterionic surfaces exhibit high mucus permeating properties. Having reached the underlying absorption membrane, lipid-based nanocarriers enable paracellular and lymphatic drug uptake, induce endocytosis and transcytosis or simply fuse with the cell membrane releasing their payload into the systemic circulation. Numerous in vivo studies provide evidence for the potential of these delivery systems. Within this review we provide an overview about the different barriers for oral peptide and protein delivery, highlight the progress made on lipid-based nanocarriers in order to overcome them and discuss strengths and weaknesses of these delivery systems in comparison to other technologies.

Characterizing the Drug-Release Enhancement Effect of Surfactants on Megestrol-Acetate-Loaded Granules

In this study, the effect of Cremophor® RH 40 (CR 40) classic micelles and Soluplus® (SP) polymeric micelles were investigated on a novel granule-type drug-delivery system containing megestrolacetate (MGA). Using a risk assessment-based approach on the formulation via melt technology resulted in the formation of these granules, presented as the dosage, with proper particle size and flow characteristics. Due to the application of a eutectic carrier base composition, gentle process conditions were reached, retaining the crystalline structure of the carrier system and allowing for the proper distribution of MGA in the granules. The increased water solubility (0.111 mg/mL to 2.154 mg/mL), and the decreased nano particle size (102.27 nm) with uniform distribution (polydispersity index of 0.259) and colloid stability (zeta potential of −12.99 mV) resulted in SP polymeric micelles prevailing over CR 40 micelles in this gastric dissolution study, performed in biorelevant fasted and fed state drug-release media. Mathematical characterization and kinetic model fitting supported the fast drug-release mechanism of polymeric micelles over micelles. The value-added polymeric micelle-containing formulation developed can be successfully administered perorally and the enhanced drug release offers the possibility of greater drug absorption in the gastrointestinal tract.

Inclusion of Medium-Chain Triglyceride in Lipid-Based Formulation of Cannabidiol Facilitates Micellar Solubilization In Vitro, but In Vivo Performance Remains Superior with Pure Sesame Oil Vehicle

Oral sesame oil-based formulation facilitates the delivery of poorly water-soluble drug cannabidiol (CBD) to the lymphatic system and blood circulation. However, this natural oil-based formulation also leads to considerable variability in absorption of CBD. In this work, the performance of lipid-based formulations with the addition of medium-chain triglyceride (MCT) or surfactants to the sesame oil vehicle has been tested in vitro and in vivo using CBD as a model drug. The in vitro lipolysis has shown that addition of the MCT leads to a higher distribution of CBD into the micellar phase. Further addition of surfactants to MCT-containing formulations did not improve distribution of the drug into the micellar phase. In vivo, formulations containing MCT led to lower or similar concentrations of CBD in serum, lymph and MLNs, but with reduced variability. MCT improves the emulsification and micellar solubilization of CBD, but surfactants did not facilitate further the rate and extent of lipolysis. Even though addition of MCT reduces the variability, the in vivo performance for the extent of both lymphatic transport and systemic bioavailability remains superior with a pure natural oil vehicle.

Nanostructured Lipid Carriers (NLCs) for Oral Peptide Drug Delivery: About the Impact of Surface Decoration

This study was aimed to evaluate the impact of surfactants used for nanostructured lipid carriers (NLCs) to provide enzymatic protection for incorporated peptides. Insulin as a model peptide was ion paired with sodium dodecyl sulfate to improve its lipophilicity. Three NLC formulations containing polyethylene glycol ester (PEG-ester), polyethylene glycol ether (PEG-ether), and polyglycerol ester (PG-ester) surfactants were prepared by solvent diffusion method. NLCs were characterized regarding particle size, polydispersity index, and zeta potential. Biocompatibility of NLCs was assessed on Caco-2 cells via resazurin assay. In vitro lipolysis study was performed using a standard lipid digestion method. Proteolytic studies were performed in simulated gastric fluid containing pepsin and simulated intestinal fluid containing pancreatin. Lipophilicity of insulin in terms of log Poctanol/water was improved from -1.8 to 2.1. NLCs were in the size range of 64-217 nm with a polydispersity index of 0.2-0.5 and exhibited a negative surface charge. PG-ester NLCs were non-cytotoxic up to a concentration of 0.5%, PEG-ester NLCs up to a concentration of 0.25% and PEG-ether NLC up to a concentration of 0.125% (w/v). The lipolysis study showed the release of >90%, 70%, and 10% of free fatty acids from PEG-ester, PG-ester, and PEG-ether NLCs, respectively. Proteolysis results revealed the highest protective effect of PEG-ether NLCs followed by PG-ester and PEG-ester NLCs for incorporated insulin complex. Findings suggest that NLCs bearing substructures less susceptible to degrading enzymes on their surface can provide higher protection for incorporated peptides toward gastrointestinal proteases.

Maximizing the Oral Bioavailability of Poorly Water-Soluble Drugs Using Novel Oil-Like Materials in Lipid-Based Formulations

Lipid-based formulations, such as self-microemulsifying drug-delivery systems (SMEDDSs), are promising tools for the oral delivery of poorly water-soluble drugs. However, failure to maintain adequate aqueous solubility after coming into contact with gastrointestinal fluids is a major drawback. In this study, we examined the use of a novel cinnamic acid-derived oil-like material (CAOM) that binds drugs with a high affinity through π-π stacking and hydrophobic interactions, as an oil core in a SMEDDS for the oral delivery of fenofibrate in rats. The use of the CAOM in the SMEDDS resulted in an unprecedented enhancement in fenofibrate bioavailability, which exceeded the bioavailability values obtained using SMEDDSs based on corn oil, a conventional triglyceride oil, or Labrasol, an enhancer of intestinal permeation. Further characterization revealed that the CAOM SMEDDS does not alter the intestinal permeability and has no inhibitory activity on P-glycoprotein-mediated drug efflux. The results reported herein demonstrate the strong potential of CAOM formulations as new solubilizers for the efficient and safe oral delivery of drugs that have limited water solubility.

The impact of emulsion droplet size on in vitro lipolysis rate and in vivo plasma uptake kinetics of triglycerides and vitamin D3 in rats

Emulsions play an important role in the process of triglyceride (TG) digestion (lipolysis). Through emulsification, the oil-water interface is increased by orders of magnitude. This often leads to faster and more efficient lipolysis, which is potentially beneficial for the intestinal uptake of oils and lipophilic compounds. In this paper, we first examined the effect of emulsion droplet size on the in vitro lipolysis rate. Then an in vivo experiment was performed, to examine the plasma uptake kinetics of TGs and vitamin D₃ (vitD₃) over a 24 hours period after oral administration of the emulsions in rats. Basic corn oil emulsions loaded with vitD₃ were prepared using polysorbate 80 as the emulsifier, with three different droplet sizes (D[3,2]): ∼3 μm (large), ∼1 μm (medium) and ∼0.3 μm (small). In vitro lipolysis experiments showed, as expected, that smaller droplets were lipolyzed more rapidly. However, the medium emulsion had by far the highest rate of lipolysis per surface area. This was attributed to bile salt limitation, polysorbate 80 lipolysis inhibition and TG digestion product accumulation. In vivo, the two smallest emulsions showed the highest uptake (C_max and AUC) of vitD₃ and TG, while the largest emulsion and bulk oil control showed lower values. However, only the (incremental) TG plasma values and kinetics displayed some statistically significant differences. These findings may have relevance for the formulation of functional foods/beverages or delivery units containing oils or lipophilic bioactives.

Exploring the Impact of Surfactant Type and Digestion: Highly Digestible Surfactants Improve Oral Bioavailability of Nilotinib

The scientific rationale for selection of the surfactant type during oral formulation development requires an in-depth understanding of the interplay between surfactant characteristics and biopharmaceutical factors. Currently, however, there is a lack of comprehensive knowledge of how surfactant properties, such as hydrophilic-lipophilic balance (HLB), digestibility, and fatty acid (FA) chain length, translate into in vivo performance. In the present study, the relationship between surfactant properties, in vitro characteristics, and in vivo bioavailability was systematically evaluated. An in vitro lipolysis model was used to study the digestibility of a variety of nonionic surfactants. Eight surfactants and one surfactant mixture were selected for further analysis using the model poorly water-soluble drug nilotinib. In vitro lipolysis of all nilotinib formulations was performed, followed by an in vivo pharmacokinetic evaluation in rats. The in vitro lipolysis studies showed that medium-chain FA-based surfactants were more readily digested compared to long-chain surfactants. The in vivo study demonstrated that a Tween 20 formulation significantly enhanced the absolute bioavailability of nilotinib up to 5.2-fold relative to an aqueous suspension. In general, surfactants that were highly digestible in vitro tended to display higher bioavailability of nilotinib in vivo. The bioavailability may additionally be related to the FA chain length of digestible surfactants with an improved exposure in the case of medium-chain FA-based surfactants. There was no apparent relationship between the HLB value of surfactants and the in vivo bioavailability of nilotinib. The impact of this study's findings suggests that when designing surfactant-based formulations to enhance oral bioavailability of the poorly water-soluble drug nilotinib, highly digestible, medium chain-based surfactants are preferred. Additionally, for low-permeability drugs such as nilotinib, which is subject to efflux by intestinal P-glycoprotein, the biopharmaceutical effects of surfactants merit further consideration.

Temperature Effect on the Adsorption and Volumetric Properties of Aqueous Solutions of Kolliphor®ELP

Density, viscosity and surface tension of Kolliphor^® ELP, the nonionic surfactant aqueous solutions were measured at temperature T = 293–318 K and at 5K interval. Steady-state fluorescence measurements have been also made using pyrene as a probe. On the basis of the obtained results, a number of thermodynamic, thermo-acoustic and anharmonic parameters of the studied surfactant have been evaluated and interpreted in terms of structural effects and solute–solvent interactions. The results suggest that the molecules of studied surfactant at concentrations higher than the critical micelle concentration act as structure makers of the water structure.

Evaluation of Sucrose Laurate as an Intestinal Permeation Enhancer for Macromolecules: Ex Vivo and In Vivo Studies

Oral delivery of macromolecules requires permeation enhancers (PEs) adaptable to formulation. Sucrose laurate (SL) (D1216), a food grade surfactant, was assessed in Caco-2 monolayers, isolated rat intestinal tissue mucosae, and rat intestinal instillations. Accordingly, 1 mM SL increased the apparent permeability coefficient (Papp) of [14C]-mannitol and reduced transepithelial electrical resistance (TEER) across monolayers. It altered expression of the tight junction protein, ZO-1, increased plasma membrane potential, and decreased mitochondrial membrane potential in Caco-2 cells. The concentrations that increased flux were of the same order as those that induced cytotoxicity. In rat colonic tissue mucosae, the same patterns emerged in respect to the concentration-dependent increases in paracellular marker fluxes and TEER reductions with 5 mM being the key concentration. While the histology revealed some perturbation, ion transport capacity was retained. In rat jejunal and colonic instillations, 50 and 100 mM SL co-administered with insulin induced blood glucose reductions and achieved relative bioavailability values of 2.4% and 8.9%, respectively, on a par with the gold standard PE, sodium caprate (C10). The histology of the intestinal loops revealed little damage. In conclusion, SL is a candidate PE with high potential for emulsion-based systems. The primary action is plasma membrane perturbation, leading to tight junction openings and a predominant paracellular flux.

Enhanced Permeation of Methotrexate via Loading into Ultra-permeable Niosomal Vesicles: Fabrication, Statistical Optimization, Ex Vivo Studies, and In Vivo Skin Deposition and Tolerability

The aim of this study was to incorporate methotrexate (MTX) into ultra-permeable niosomal vesicles, containing cremophor RH40 as an edge activator (EA) and polyvinyl alcohol (PVA) as a stabilizer to enhance the drug permeation. Formulae were prepared by ethanol injection method following a Box-Behnken design in order to optimize the formulation variables (EA%, stabilizer %, and sonication time). To investigate the role of both cremophor RH40 and PVA, conventional MTX niosomes and MTX niosomes containing PVA only were fabricated. Drug entrapment efficiency percent (EE%), particle size (PS) analysis, zeta potential (ZP) measurements, and transmission electron microscopy (TEM) were conducted to characterize the vesicles. Cell viability studies and ex vivo permeation experiments of the optimized formula were conducted. Lastly, in vivo skin deposition of MTX from both the optimized formula and MTX solution was performed in rats. Besides, histopathological changes in rat skin were assessed. The optimized MTX ultra-permeable niosomal formula demonstrated spherical morphology, with an EE% of 65.16% and a PS of 453.6 nm. The optimized formula showed better physical stability in comparison with that of the same composition but lacking PVA. The cell viability studies verified the superior cytotoxicity of the optimized formula, and the ex vivo permeation studies revealed its ability to improve the drug permeation. The optimized formula demonstrated a significant deposition of MTX in rat dorsal skin, and histopathological evaluation confirmed the tolerability of the optimized formula in rats upon topical application. Accordingly, ultra-permeable noisomes, as a stable nanosystem, could be promising for effective delivery of MTX.

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.

Insulin- and quercetin-loaded liquid crystalline nanoparticles: implications on oral bioavailability, antidiabetic and antioxidant efficacy

Aim: The present study reports insulin (INS)- and quercetin (QT)-lyotropic liquid crystalline nanoparticles (LCNPs) with improved bioavailability, antidiabetic and antioxidant efficacy following oral administration. Materials & methods: The developed INS-QT-LCNPs were evaluated for simulated gastric fluid stability. In vitro Caco-2 uptake studies were also performed. Furthermore, in vivo pharmacokinetics and pharmacodynamics of INS-QT-LCNPs were evaluated. Results & conclusion: INS entrapped within LCNPs demonstrated excellent stability in simulated gastric fluid. Higher uptake of fluorescein isothiocyanate-INS-LCNPs were observed in Caco-2 cells. INS-LCNPs demonstrated approximately 20% relative bioavailability compared with subcutaneously administered INS. Significant decrease in oxidative stress was confirmed by reduction in malondialdehyde level. Overall, combination strategy not only overcomes poor oral bioavailability of INS and QT, but also prevents the generation of reactive oxygen species, responsible for diabetes-mediated complications.

Interactions between surfactants and hydrolytic enzymes

Hydrolytic enzymes are combined with surfactants in many types of formulations, for instance detergents and personal care products. If the surfactant interacts with the enzyme there may be conformational changes that eventually lead to loss of the enzymatic activity. From a practical point of view it is important to understand the nature and magnitude of these interactions. After an introduction of the topic the review briefly discusses enzyme catalyzed reactions where surfactants are substrates for the enzyme. The rest of the review relates to associations between surfactants and hydrolytic enzymes without the surfactant being a substrate in the reaction. A discussion about general principles for such interactions is followed by a survey of the relevant literature related to four important types of hydrolytic enzymes: lipases, proteases, amylases and cellulases. It is shown in the review that the effect exerted by the surfactant differs between the different types of enzymes; it is therefore difficult to make general statements about which surfactants are most detrimental to the activity of hydrolytic enzymes. However, as a general rule nonionic surfactants can be regarded as more benign to an enzyme than anionic and cationic surfactants. This difference can be ascribed to the difference in binding mode. Whereas a nonionic surfactant only binds to the enzyme through hydrophobic interactions, an ionic surfactant can bind by a combination of electrostatic attraction and hydrophobic interaction. This latter type of binding can be strong and lead to conformational changes already at very low surfactant concentration, often far below its critical micelle concentration.

Utility of Cremophor RH 40 as a micellar improvement for spectrofluorimetric estimation of sorafenib in pure form, commercial preparation, and human plasma

An easy, quick, simple and accurate spectrofluorimetric method was recognized and validated for evaluation of sorafenib (SOR) in pure form and biologically in plasma. Cremophor RH 40 (Cr RH 40) used for enhancing the fluorescence activity of SOR in phosphate buffer (pH 7). Cr RH 40 improved the native fluorescence of SOR remarkably in water. The fluorescence spectrum of SOR was observed at 405 nm after excitation at 265 nm. The linearity appeared to be in the range of 5 to 600 ng ml^-1 for pure and from 9 to 500 ng ml^-1 for plasma using the protein precipitation (ppt) method while from 10 to 500 ng ml^-1 for plasma using liquid-liquid extraction method. The precisions and the accuracy of the estimated method gave satisfactory results. The recommended method was effectively applied for determination of SOR in human plasma with high recovery values. The results of some compounds that are possibly found in plasma were studied. The proposed method was also focused on real volunteers and a drug dissolution test.

Self-emulsifying preconcentrates of daidzein–phospholipid complex: design, in vitro and in vivo appraisal

Aim: Self-emulsifying phospholipid-complex preconcentrates (SEPPs) were fabricated to improve oral bioavailability of daidzein (DAI), an anticancer drug with challenging amphiphobic nature and extensive presystemic metabolism. Methods: DAI–phosphatidylcholine complex was prepared to enhance DAI lipophilicity and loading in SEPPs. The physicochemical characteristics and the pharmacokinetic behavior in rats were studied. Results: Surfactant-free SEPP (plain DAI:Phosal® 53MCT complex) was monodisperse upon aqueous dilution with nanorange globule size (485 ± 15 nm). Compared with drug suspension, it showed enhanced drug release and 2.38-fold enhanced oral bioavailability with minimized drug-induced intestinal irritation. Addition of 30% surfactant/co-surfactant mixture did not show any significant difference in drug release rate or absorption profile. Conclusion: The highly safe surfactant-free SEPP could be an effective approach to improve DAI oral bioavailability.

Knockout of a difficult-to-remove CHO host cell protein, lipoprotein lipase, for improved polysorbate stability in monoclonal antibody formulations

While the majority of host cell protein (HCP) impurities are effectively removed in typical downstream purification processes, a small population of HCPs are particularly challenging. Previous studies have identified HCPs that are challenging for a variety of reasons. Lipoprotein lipase (LPL)-a Chinese hamster ovary (CHO) HCP that functions to hydrolyze esters in triglycerides-was one of ten HCPs identified in previous studies as being susceptible to retention in downstream processing. LPL may degrade polysorbate 80 (PS-80) and polysorbate 20 (PS-20) in final product formulations due to the structural similarity between polysorbates and triglycerides. In this work, recombinant LPL was found to have enzymatic activity against PS-80 and PS-20 in a range of solution conditions that are typical of mAb formulations. LPL knockout CHO cells were created with CRISPR and TALEN technologies and resulting cell culture harvest fluid demonstrated significantly reduced polysorbate degradation without significant impact on cell viability when compared to wild-type samples. Biotechnol. Bioeng. 2017;114: 1006-1015. © 2016 Wiley Periodicals, Inc.

PLGA nanoparticles for peroral delivery: How important is pancreatic digestion and can we control it?

Biodegradable nanoparticles made of Poly(lactide-co-glycolide) are increasingly proposed for the improvement of oral drug absorption, but also as carriers for the treatment of colonic diseases. Unfortunately, our knowledge of the digestibility of PLGA-NPs is rather limited. Therefore, we investigated the impact of pancreatin on the digestibility of PLGA-NPs stabilized with different emulsifiers. The pancreatin induced degradation was monitored by the pH-stat method and an enzymatic l-lactic acid assay. A high digestibility was found for poloxamer 188 and polysorbate 80 stabilized PLGA-NPs. The digestion could be blocked by Orlistat, indicating a major role of pancreatic lipase. PLGA-NPs stabilized with Poly(vinyl alcohol) (=PVA) were not digested at comparable surfactant concentrations (0.6%). However, PLGA-NPs stabilized with very low amounts of PVA (0.1%) were digestible. In conclusion, PLGA-NPs are substrates for the pancreatic lipase. The digestibility can be enhanced or blocked by the proper selection of the surfactant composition and concentration.

The In Vitro Lipolysis of Lipid-Based Drug Delivery Systems: A Newly Identified Relationship between Drug Release and Liquid Crystalline Phase

The purpose of this study was to offer a new insight into the microstructure changes during in vitro lipolysis of five lipid-based drug delivery formulations belonging to different lipid formulation types. Five lipid-based formulations of indomethacin were investigated using an in vitro lipolysis model. During lipolysis, microstructures of the intermediate phase formed by lipolytic products were observed. The results showed that the time of liquid crystal formation during in vitro digestion for these formulations was Type I > Type II > Type IIIB > Type IV > Type IIIA (p < 0.05). After lipolysis, the drug releases from these formulations were determined. The results showed that the amount of drug distributed in the aqueous phase, obtained by ultracentrifuge after lipolysis, was, astonishingly, in inverse rank order of the above mentioned, that is, Type IIIA > Type IV > Type IIIB > Type II > Type I (p < 0.05). These results showed that the liquid crystalline phase probably has a critical influence on the fate of the drug during in vitro lipolysis and suggested that the liquid crystalline phase facilitated drug precipitation. These findings may improve the understanding of lipolysis of lipid-based drug delivery systems for designing better delivery system.

Micellar Enhanced Spectrofluorimetric Method for the Determination of Ponatinib in Human Plasma and Urine via Cremophor RH 40 as Sensing Agent

An impressively simple and precise spectrofluorimetric procedure was established and validated for ponatinib (PTB) quantitation in biological fluids such as human plasma and human urine. This method depends on examining the fluorescence characteristics of PTB in a micellar system of Cremophor RH 40 (Cr RH 40). Cr RH 40 enhanced the intrinsic fluorescence of PTB distinctly in aqueous water. The fluorescence spectra of PTB was recorded at 457 nm following its excitation at 305 nm. Maximum fluorescence intensity was attained by addition of 0.7 mL of Cr RH 40 and one mL of phosphate buffer to PTB aliquots and then dilution with distilled water. There is a linear relationship between the fluorescence intensity of PTB and its concentration over the range 5–120 ngmL⁻¹, with limit of detection and limit of quantification equal to 0.905 ngmL⁻¹ and 2.742 ngmL⁻¹, respectively. The accuracy and the precisions of the proposed method were checked and gave adequate results. The adopted method was applied with a great success for PTB quantitation in different biological matrices (spiked human plasma and urine) giving high recovery values.

Self-emulsifying drug delivery systems in oral (poly)peptide drug delivery

INTRODUCTION

Oral administration of most therapeutic peptides and proteins is mainly restricted due to the enzymatic and absorption membrane barrier of the GI tract. In order to overcome these barriers, various technologies have been explored. Among them, self-emulsifying drug delivery systems (SEDDS) received considerable attention as potential carriers to facilitate oral peptide and protein delivery in recent years.

AREAS COVERED

This review article intends to summarize physiological barriers which limit the bioavailability of orally administrated peptide and protein drugs. Furthermore, the potential of SEDDS to protect incorporated peptides and proteins towards peptidases and proteases and to penetrate the mucus layer is reviewed. Their permeation-enhancing properties and their ability to release the drug in a controlled way are described. Moreover, this review covers the results of in vivo studies providing evidence for this promising approach.

EXPERT OPINION

As SEDDS can: i) provide a protective effect towards a presystemic metabolism; ii) efficiently permeate the intestinal mucus gel layer in order to reach the absorption membrane; and iii) be produced in a very simple and cost-effective manner, they are a promising tool for oral peptide and protein drug delivery.

PEGylated γ-tocotrienol isomer of vitamin E: Synthesis, characterization, in vitro cytotoxicity, and oral bioavailability

Vitamin E refers to a family of eight isomers divided into two subgroups, tocopherols and the therapeutically active tocotrienols (T3). The PEGylated α-tocopherol isomer of vitamin E (vitamin E TPGS) has been extensively investigated for its solubilizing capacity as a nonionic surfactant in various drug delivery systems. Limited information, however, is available about the PEG conjugates of the tocotrienol isomers of vitamin E. In this study two PEGylated γ-T3 variants with mPEG molecular weights of 350 (γ-T3PGS 350) and 1000 (γ-T3PGS 1000) were synthesized by a two-step reaction procedure and characterized by (1)H NMR, HPLC, and mass spectroscopy. The physical properties of their self-assemblies in water were characterized by zeta, CMC, and size analysis. Similar physical properties were found between the PEGylated T3 and vitamin E TPGS. PEGylated T3 were also found to retain the in vitro cytotoxic activity of the free T3 against the MCF-7 and the triple-negative MDA-MB-231 breast cancer cells. PEGylated γ-T3 also increased the oral bioavailability of γ-T3 by threefolds when compared to the bioavailability of γ-T3 formulated into a self-emulsified drug delivery system. No significant differences in biological activity were found between the PEG 350 and 100 conjugates. Results from this study suggest that PEGylation of γ-T3 represents a viable platform for the oral and parenteral delivery of γ-T3 for potential use in the prevention of breast cancer.

Solvent-free melting techniques for the preparation of lipid-based solid oral formulations

Lipid excipients are applied for numerous purposes such as taste masking, controlled release, improvement of swallowability and moisture protection. Several melting techniques have evolved in the last decades. Common examples are melt coating, melt granulation and melt extrusion. The required equipment ranges from ordinary glass beakers for lab scale up to large machines such as fluid bed coaters, spray dryers or extruders. This allows for upscaling to pilot or production scale. Solvent free melt processing provides a cost-effective, time-saving and eco-friendly method for the food and pharmaceutical industries. This review intends to give a critical overview of the published literature on experiences, formulations and challenges and to show possibilities for future developments in this promising field. Moreover, it should serve as a guide for selecting the best excipients and manufacturing techniques for the development of a product with specific properties using solvent free melt processing.

Kolliphor surfactants affect solubilization and bioavailability of fenofibrate. Studies of in vitro digestion and absorption in rats

Selection of excipients for drug formulations requires both intellectual and experimental considerations as many of the used excipients are affected by physiological factors, e.g., they may be digested by pancreatic enzymes in the gastrointestinal tract. In the present paper we have looked systematically into the differences between Kolliphor ELP, EL, and RH40 and how they affect the bioavailability of fenofibrate, through pharmacokinetic studies in rats and in vitro lipolysis studies. The study design was made as simple as possible to avoid confounding factors, for which reason the tested formulations only comprised an aqueous micellar solution of the model drug (fenofibrate) in varying concentrations (2-25% (w/v)) of the three tested surfactants. Increased concentrations of Kolliphor ELP and EL led to increased fenofibrate AUC0-24h values. For the Kolliphor RH40 formulations, an apparent fenofibrate absorption optimum was seen at 15% (w/v) surfactant, displaying both the highest AUC0-24h and Cmax. The reduced absorption of fenofibrate from the formulation containing the highest level of surfactant (25% w/v) was thought to be caused by some degree of trapping within Kolliphor RH40 micelles. In vitro, Kolliphor ELP and EL were found to be more prone to digestion than Kolliphor RH40, though not affecting the in vivo results. The highest fenofibrate bioavailability was attained from formulations with high Kolliphor ELP/EL levels (25% (w/v)), indicating that these surfactants are the better choice for solubilizing fenofibrate in order to increase the absorption upon oral administration. Due to drug dependent effects of the different types of Kolliphor, more studies are recommended in order to understand which type of Kolliphor is best suited for a given drug.

A new method to determine the new C-Met inhibitor “Cabozantinib” in dosage form and human plasma via micelle-enhanced spectrofluorimetry

A highly sensitive and simple micelle-enhanced spectrofluorimetric method was developed for the determination of cabozantinib (CBZ) in its pharmaceutical formulation and spiked human plasma without any derivatization.

'Stealth' lipid-based formulations: poly(ethylene glycol)-mediated digestion inhibition improves oral bioavailability of a model poorly water soluble drug

For over 20years, stealth drug delivery has been synonymous with nanoparticulate formulations and intravenous dosing. The putative determinants of stealth in these applications are the molecular weight and packing density of a hydrophilic polymer (commonly poly(ethylene glycol) (PEG)) that forms a steric barrier at the surface of the nanoparticle. The current study examined the potential translation of the concepts learned from stealth technology after intravenous administration to oral drug delivery and specifically, to enhance drug exposure after administration of oral lipid-based formulations (LBFs) containing medium-chain triglycerides (MCT). MCT LBFs are rapidly digested in the gastrointestinal tract, typically resulting in losses in solubilisation capacity, supersaturation and drug precipitation. Here, non-ionic surfactants containing stealth PEG headgroups were incorporated into MCT LBFs in an attempt to attenuate digestion, reduce precipitation risk and enhance drug exposure. Stealth capabilities were assessed by measuring the degree of digestion inhibition that resulted from steric hindrance of enzyme access to the oil-water interface. Drug-loaded LBFs were assessed for maintenance of solubilising capacity during in vitro digestion and evaluated in vivo in rats. The data suggest that the structural determinants of stealth LBFs mirror those of parenteral formulations, i.e., the key factors are the molecular weight of the PEG in the surfactant headgroup and the packing density of the PEG chains at the interface. Interestingly, the data also show that the presence of labile ester bonds within a PEGylated surfactant also impact on the stealth properties of LBFs, with digestible surfactants requiring a PEG Mw of ~1800g/mol and non-digestible ether-based surfactants ~800g/mol to shield the lipidic cargo. In vitro evaluation of drug solubilisation during digestion showed stealth LBFs maintained drug solubilisation at or above 80% of drug load and reduced supersaturation in comparison to digestible counterparts. This trend was also reflected in vivo, where the relative bioavailability of drug after administration in two stealth LBFs increased to 120% and 182% in comparison to analogous digestible (non-stealth) formulations. The results of the current study indicate that self-assembled "stealth" LBFs have potential as a novel means of improving LBF performance.