Combining two technologies: multifunctional polymers and self-nanoemulsifying drug delivery system (SNEDDS) for oral insulin administration

Future Nanotechnology-Based Strategies for Improved Management of Helicobacter pylori Infection

Helicobacter pylori (H. pylori) is a recalcitrant pathogen, which can cause gastric disorders. During the past decades, polypharmacy-based regimens, such as triple and quadruple therapies have been widely used against H. pylori. However, polyantibiotic therapies can disturb the host gastric/gut microbiota and lead to antibiotic resistance. Thus, simpler but more effective approaches should be developed. Here, some recent advances in nanostructured drug delivery systems to treat H. pylori infection are summarized. Also, for the first time, a drug release paradigm is proposed to prevent H. pylori antibiotic resistance along with an IVIVC model in order to connect the drug release profile with a reduction in bacterial colony counts. Then, local delivery systems including mucoadhesive, mucopenetrating, and cytoadhesive nanobiomaterials are discussed in the battle against H. pylori infection. Afterward, engineered delivery platforms including polymer-coated nanoemulsions and polymer-coated nanoliposomes are poposed. These bioinspired platforms can contain an antimicrobial agent enclosed within smart multifunctional nanoformulations. These bioplatforms can prevent the development of antibiotic resistance, as well as specifically killing H. pylori with no or only slight negative effects on the host gastrointestinal microbiota. Finally, the essential checkpoints that should be passed to confirm the potential effectiveness of anti-H. pylori nanosystems are discussed.

Strategies to Enhance the Solubility and Bioavailability of Tocotrienols Using Self-Emulsifying Drug Delivery System

Tocotrienols have higher medicinal value, with multiple sources of evidence showing their biological properties as antioxidant, anti-inflammatory, and osteoprotective compounds. However, tocotrienol bioavailability presents an ongoing challenge in its translation into viable products. This is because tocotrienol oil is known to be a poorly water-soluble compound, making it difficult to be absorbed into the body and resulting in less effectiveness. With the potential and benefits of tocotrienol, new strategies to increase the bioavailability and efficacy of poorly absorbed tocotrienol are required when administered orally. One of the proposed formulation techniques was self-emulsification, which has proven its capacity to improve oral drug delivery of poorly water-soluble drugs by advancing the solubility and bioavailability of these active compounds. This review discusses the updated evidence on the bioavailability of tocotrienols formulated with self-emulsifying drug delivery systems (SEDDSs) from in vivo and human studies. In short, SEDDSs formulation enhances the solubility and passive permeability of tocotrienol, thus improving its oral bioavailability and biological actions. This increases its medicinal and commercial value. Furthermore, the self-emulsifying formulation presents a useful dosage form that is absorbed in vivo independent of dietary fats with consistent and enhanced levels of tocotrienol isomers. Therefore, a lipid-based formulation technique can provide an additional detailed understanding of the oral bioavailability of tocotrienols.

Surface design of nanocarriers: Key to more efficient oral drug delivery systems

As nanocarriers (NCs) can improve the solubility of drugs, prevent their degradation by gastrointestinal (GI) enzymes and promote their transport across the mucus gel layer and absorption membrane, the oral bioavailability of these drugs can be substantially enhanced. All these properties of NCs including self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), liposomes, polymeric nanoparticles, inorganic nanoparticles and polymeric micelles depend mainly on their surface chemistry. In particular, interaction with food, digestive enzymes, bile salts and electrolytes, diffusion behaviour across the mucus gel layer and fate on the absorption membrane are determined by their surface. Bioinert surfaces limiting interactions with gastrointestinal fluid and content as well as with mucus, adhesive surfaces providing an intimate contact with the GI mucosa and absorption enhancing surfaces can be designed. Furthermore, charge converting surfaces shifting their zeta potential from negative to positive directly at the absorption membrane and surfaces providing a targeted drug release are advantageous. In addition to these passive surfaces, even active surfaces cleaving mucus glycoproteins on their way through the mucus gel layer can be created. Within this review, we provide an overview on these different surfaces and discuss their impact on the performance of NCs in the GI tract.

Self-emulsifying drug delivery systems: a novel approach to deliver drugs

Self-emulsifying drug delivery systems (SEDDS) are a proven method for poorly soluble substances works by increasing the solubility and bioavailability. SEDDS and isotropic mixtures, are composed of oils, surfactants, and occasionally cosolvents. The ability of these formulations and methods to produce microemulsions or fine oil-in-water (o/w) emulsions after moderate stirring and dilution by water phase along the GI tract might be a promising technique for lipophilic agents with dissolution rate-limited absorption. This review provides an outline of SEDDS's numerous advances and biopharmaceutical elements, types, manufacturing, characterization, limitations, and future prospects. The evaluation of SEDDS and its applications are also discussed, focusing on the advances of SEDDS's solid self-emulsifying delivery mechanism and dosage form. By integrating suitable polymer into the formulation, SEDDS may be studied for the creation of a formulation with sustained drug release. This technology's improvement might lead to a new application in the field of medicine delivery. SEDDS has been demonstrated to be quite efficient in increasing oral bioavailability of lipophilic products. SEDDS is one of the promising methods for controlling the characteristics of medications that are not great choices for oral delivery. It is also worth mentioning that SEDDS may be made in variety of solid dosage forms that are acceptable for both oral and parenteral administration.

Multi-strategic approaches for enhancing active transportation using self-emulsifying drug delivery system

Oral delivery is the most desired route of drug administration and it can be more beneficial for patients suffering from chronic diseases wherein frequent parenteral administration of proteins such as insulin and calcitonin is required. The BCS class II drugs show low aqueous solubility and high permeability whereas BCS class IV drugs suffer from low aqueous solubility and low permeability. Additionally, biologic drugs are highly sensitive to presence of bioenzymes and bile salts when administered orally. Self-emulsifying drug delivery system (SEDDS) is a thermodynamically stable lipid formulation that enhances oral absorption of active ingredients via the opening of tight junctions, increasing the membrane fluidity, and thus overcomes the physiological barriers like viscous mucus layer, strong acid conditions and enzymatic degradation. An understanding of different theories that govern SEDDS formation and drug release can help in formulating a highly stable and effective drug delivery system. Poorly permeable drugs such as chlorpromazine require modification using methods like hydrophobic ion pairing, complexation with phospholipids, etc. to enable high entrapment efficiency which is discussed in the article. Additionally, the article gives an overview of the influence of polymers, length of fatty acids chain and zeta potential in enhancing permeation across the intestinal membrane.

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.

Optimization and Evaluation of Self-nanoemulsifying Drug Delivery System for Enhanced Bioavailability of Plumbagin

Plumbagin, a potential bioactive lipophilic molecule, possesses limited solubility and low oral bioavailability. The purpose of the present study was to examine the potential of the self-nanoemulsifying drug delivery system for improving solubility and oral bioavailability of plumbagin. The self-nanoemulsifying drug delivery system was formulated from Capmul MCM (oil), Tween 20 (surfactant), and propylene glycol (cosurfactant). Central composite design was employed as statistical tool to optimize the formulation variables, X₁ (oil) and X₂ (surfactant: co-surfactant mixture ratio), of the self-nanoemulsifying drug delivery system. The responses studied were droplet size, self-emulsification time, % of drug release in 15 min, and equilibrium solubility. The optimized liquid self-nanoemulsifying drug delivery system was adsorbed on Neusilin US2 and characterized for flow properties, X-ray diffractometry, differential scanning calorimetry, in vitro dissolution, in vivo anti-inflammatory activity, and bioavailability study in Wistar rats, as well as ex vivo permeation study. The droplet size, polydispersity index, self-emulsification time, and equilibrium solubility of the optimized formulation were 58.500 ± 1.170 nm, 0.228 ± 0.012, 17.660 ± 1.520 s, and 34.180 ± 1.380 mg/mL, respectively. Its zeta potential, transmittance value, and cloud point were - 28.200 ± 1.200 mV, 99.200% ± 0.600, and 90 °C, respectively. Drug release was found to be 93.320% ± 1.090. In vivo anti-inflammatory study confirmed more enhanced activity from the self-nanoemulsifying drug delivery system than with pure plumbagin. Pharmacokinetic study in rats revealed that solid self-nanoemulsifying drug delivery system had 4.49-fold higher bioavailability than pure plumbagin. Ex vivo permeation study demonstrated 1.75-fold increased intestinal permeability of the self-nanoemulsifying drug delivery system than pure plumbagin. The developed self-nanoemulsifying drug delivery system is a useful solid platform for improving solubility and oral bioavailability of plumbagin.

Supersaturable self-microemulsifying delivery systems: an approach to enhance oral bioavailability of benzimidazole anticancer drugs

This study explored the design of supersaturable self-microemulsifying drug delivery systems (S-SMEDDS) to address poor solubility and oral bioavailability of a novel benzimidazole derivative anticancer drug (BI). Firstly, self-microemulsifying drug delivery systems SMEDDS made of Miglyol® 812, Kolliphor® RH40, Transcutol® HP, and ethanol were prepared and loaded with the BI drug. Upon dispersion, the systems formed neutrally charged droplets of around 20 nm. However, drug precipitation was observed following incubation with simulated gastric fluid (pH 1.2). Aiming at reducing this precipitation and enhancing drug payload, supersaturable systems were then prepared by adding 1% hydroxypropyl cellulose as precipitation inhibitor. Supersaturable systems maintained a higher amount of drug in a supersaturated state in gastric medium compared with conventional formulations and were stable in simulated intestinal medium (pH 6.8). In vitro cell studies using Caco-2 cell line showed that these formulations reduced in a transient manner the transepithelial electrical resistance of the monolayers without toxicity. Accordingly, confocal images revealed that the systems accumulated at tight junctions after a 2 h exposure. In vivo pharmacokinetic studies carried out following oral administration of BI-loaded S-SMEDDS, SMEDDS, and free drug to healthy mice showed that supersaturable systems promoted drug absorption compared with the other formulations. Overall, these data highlight the potential of using the supersaturable approach as an alternative to conventional SMEDDS for improving oral systemic absorption of lipophilic drugs.

Role of lipid nanocarriers for enhancing oral absorption and bioavailability of insulin and GLP-1 receptor agonists

Growing demand for insulin and glucagon-like peptide-1 receptor agonists (GLP-1 RA) is observed, considering the progressive nature of diabetes and the potential therapeutic role of peptides in its treatment. However, chronic parenteral administration is responsible for pain and rashes at the site of injection. Oral delivery of insulin and GLP-1 RA promises better patient compliance owing to their ease of administration and reduction in chances of peripheral hypoglycaemia and weight gain. The review article discusses the potential of lipid carriers in combination with different strategies such as absorption enhancers, PEGylation, lipidisation, etc. The lipid nanocarriers improve the membrane permeability and oral bioavailability of high molecular weight peptides. Additionally, the clinical status of different nanocarriers for anti-diabetic peptides is discussed. Previous research on nanocarriers showed significant hypoglycaemic activity and safety in animal studies; however, extrapolation of the same in human subjects is not validated. With the rising global burden of diabetes, the lipid nanocarriers show the potential to revolutionise treatment with oral delivery of insulin and GLP-1 RA.

Nanoemulgel, an Innovative Carrier for Diflunisal Topical Delivery with Profound Anti-Inflammatory Effect: in vitro and in vivo Evaluation

Purpose

Rheumatoid arthritis is an autoimmune disorder that directly affects joints. However, other body organs including heart, eyes, skin, blood vessels and lungs may also be affected. The purpose of this study was to design and evaluate a nanoemulgel formulation of diflunisal (DIF) and solubility enhanced diflunisal (DIF-IC) for enhanced topical anti-inflammatory activity.

Methodology

Nanoemulsion formulations of both DIF and DIF-IC were prepared and incorporated in three different gelling agents, namely carboxymethylcellulose sodium (CMC-Na), sodium alginate (Na-ALG) and xanthan gum (XG). All the formulations were evaluated in term of particle size, pH, conductivity, viscosity, zeta potential and in vitro drug release. The formulation 2 (NE2) of both DIF and DIF-IC which expressed optimum release and satisfactory physicochemical properties was incorporated with gelling agents to produce final nanoemulgel formulations. The optimized nanoemulgel formulation was subjected to three different in vivo anti-inflammatory models including carrageenan-induced paw edema model, histamine-induced paw edema model and formalin-induced paw edema model.

Results

DIF-IC-loaded nanoemulgel formulations yielded significantly enhanced in vitro skin permeation than DIF-loaded nanoemulgel. The nanoemulgel formulation of DIF-IC formulated with XG produced improved in vivo anti-inflammatory activity.

Conclusion

It was recommended that DIF-IC-based nanoemulgel formulation prepared with XG could be a better option for effective topical treatment of inflammatory conditions.

Oral self-nanoemulsifying formulation of GLP-1 agonist peptide exendin-4: development, characterization and permeability assesment on Caco-2 cell monolayer

The objective of this study was to prepare a stable self-nanoemulsifying formulation of exendin-4, which is an antidiabetic peptide. As exendin-4 is commercially available only in subcutaneous form, several attempts have been made to discover an effective oral formulation. Self-nanoemulsifying drug delivery systems are known to be suitable carriers for the oral administration of peptide drugs. Various ratios of oil, surfactant, and co-surfactant mixtures were used to determine the area in the pseudoternary phase diagram for clear nanoemulsion. The Design of Experiment approach was used for the optimization of the formulation. Blank self-nanoemulsifying formulations containing ethyl oleate as oil phase, Cremophor EL^®, and Labrasol^® as surfactant, absolute ethanol, and propylene glycol as co-solvent in various proportions were approximately 18-50 nm, 0.08-0.204 and - 3 to - 23 mV in droplet size, polydispersity index, and zeta potential, respectively. When all formulations were compared by statistical analysis, five of them with smaller droplet sizes were selected for further studies. The physical stability test was performed for 1 month at 5 °C ± 3 °C and 25 °C ± 2 °C/60% RH ± 5% RH storage conditions. As a result of the characterization and physical stability test results, ethyl oleate: Cremophor EL^®:absolute ethanol (30:52.5:17.5) formulation and four formulations containing ethyl oleate: Cremophor EL^®:Labrasol^®:propylene glycol:absolute ethanol at varying concentrations were considered for peptide encapsulation efficiency. Formulation having the highest encapsulation efficiency of exendin-4 containing ethyl oleate: Cremophor EL^®:Labrasol^®:propylene glycole:absolute ethanol (15:42.5:21.25:15.94:5.31) was selected for in vitro Caco-2 intestinal permeability study. The permeabiliy coefficient was increased by 1.5-folds by exendin-4-loaded self-nanoemulsifying formulation as compared to the exendin-4 solution. It can be concluded that intestinal permeability has been improved by self-nanoemulsifying formulation.

Polyphosphate coatings: A promising strategy to overcome the polycation dilemma

AIM

It was the aim of this study to develop a zeta potential changing drug delivery system by decorating lipid-based nanocarriers with a polycationic cell penetrating peptide (CPP) and subsequently masking these cationic substructures with polyphosphates.

METHODS

In order to anchor the CPP poly-l-lysine (PLL) on the surface of the oily droplets of an o/w nanoemulsion, stearic acid was covalently attached to the peptide. The resulting CPP-decorated oily droplets were coated with phytic acid and tripolyphosphate. The elimination of these polyphosphates due to cleavage by alkaline phosphatase was monitored by the release of monophosphate from the surface of the nanocarriers, by the change in zeta potential and by cellular uptake studies on Caco-2 cells.

RESULTS

Polyphosphate coated PLL-decorated nanocarriers exhibited a pronounced conversion of zeta potential from -14.1 mV to +4.2 mV in case of tripolyphosphate coated nanocarriers and from -9.9 mV to -2.6 mV in case of phytic acid coated nanocarriers. The cellular uptake on Caco-2 cells of the polyphosphate coated nanocarriers was 4-fold improved compared to the control nanocarriers. Furthermore, confocal images showed that the majority of nanodroplets distributed in cytoplasm not being internalized into lysosomes.

CONCLUSION

Polyphosphate coating of CPP-decorated nanocarriers seems to be a promising and simple strategy to overcome the polycation dilemma.

Evaluation of the hypoglycemic effect of exendin-4's new oral self-nanoemulsifying system in rats

The objective of this study is to develop a new self-nanoemulsifying system containing exendin-4 with or without enzyme inhibitor chymostatin and to evaluate the effects of oral administration of exendin-4 and exendin-4/chymostatin loaded self nanoemulsifying system on plasma exendin-4, plasma insulin, blood glucose levels and to compare with the oral and subcutaneous administration of exendin-4 in non-diabetic and streptozotocin-induced type 2 diabetic rats. Exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying system containing ethyl oleate as the oil phase, Cremophor EL®/Labrasol® as the surfactants and propylene glycol as the co-solvent were prepared. The mean droplet size, polydispersity index, zeta potential and viscosity of exendin-4 loaded self-nanoemulsifying system were found as 24.28 ± 0.43 nm, 0.17 ± 0.01, -1.28 ± 3.61 mV, 79.60 ± 3.30 m.Pas, respectively. The mean droplet size, polydispersity index, zeta potential and viscosity of exendin-4/chymostatin loaded self-nanoemulsifying system were found as 20.25 ± 0.35 nm, 0.11 ± 0.02, -1.85 ± 2.49 mV, 100.02 ± 7.65 m.Pas, respectively according to our previous study. In the present study, we focused on long-term physical stability studies, pharmacokinetic studies and pharmacodynamic studies of prepared self-nanoemulsifying systems. According to the long- term physical stability data, exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying systems were found stable both at 5°C ± 3°C and at 25°C ± 60% RH for 12 months. Exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying systems increased AUC and C_max values in non-diabetic rats compared to the oral exendin-4 solution. In diabetic rats, exendin-4/chymostatin loaded self nanoemulsifying systems increased C_max values compared to the exendin-4 solution. Exendin-4/chymostatin loaded self-nanoemulsifying system decreased inter-subject variability compared to commercial Byetta®. At 30^th minute after administration of exendin-4 loaded self-nanoemulsifying system, exendin-4/chymostatin loaded self nanoemulsifying system and Byetta®, blood glucose levels decreased to 23%, 25%, 29%, respectively. It has been shown that pharmacodynamic response is close to Byetta® with exendin-4/chymostatin self-nanoemulsifying system oral administration. In conclusion, a self nanoemulsifying system was found to be a suitable carrier system, and the combination with enzyme inhibitor chymostatin is thought to be promising for oral delivery of exendin-4.

Improved hepatoprotective activity of Beta vulgaris L. leaf extract loaded self-nanoemulsifying drug delivery system (SNEDDS): in vitro and in vivo evaluation

OBJECTIVE

Beta vulgaris L. (beetroot) is a vegetable plant rich in phytochemical compounds such as phenolic acids, carotenoids and flavonoids. The objective of the current study is the development and optimization of self-nanoemulsifying drug delivery systems (SNEDDSs) to enhance the hepatoprotective activity of beet leaf (BL) extract.

METHODS

Total flavonoids content was estimated in the BL extract and its solubility was evaluated in various vehicles to select proper component combinations. Pseudo-ternary phase diagrams were constructed employing olive, linseed, castor and sesame oils (oil phase), Tween^® 20 (Tw20) and Tween^® 80 (Tw80) (surfactants (SAs)) as well as dimethyl sulfoxide (DMSO) and propylene glycol (PG) (co-surfactants (Co-SAs)). Optimization of formulations from the phase diagrams took place through testing their thermodynamic stability, dispersibility and robustness to dilution.

RESULTS

Four optimized BL-SNEDDS formulations, comprising linseed oil or olive oil, Tw80 and DMSO at two SA/Co-SA ratios (2:1 or 3:1) were chosen. They exhibited high cloud point and percentage transmittance values with spherical morphology of mean droplet sizes ranging from 14.67 to 16.06 nm and monodisperse distribution with negatively charged zeta potential < -9.51 mV. The in vitro release profiles of the optimized formulations in pH 1.2 and 6.8 were nearly similar, with a non-Fickian release mechanism. In vivo evaluation of BL-SNEDDSs hepatoprotective activity in a thioacetamide-induced hepatotoxicity rat model depicted promoted liver functions, inflammatory markers and histopathological findings, most prominently in the group treated by F7.

CONCLUSION

The results indicate that SNEDDS, as a nanocarrier system, has potential to improve the hepatoprotective activity of the BL extract.

Thiolated Chitosans: A Multi-talented Class of Polymers for Various Applications

Various properties of chitosan can be customized by thiolation for very specific needs in a wide range of application areas. Since the discovery of thiolated chitosans, many studies have proven their advantageous characteristics, such as adhesion to biological surfaces, adjustable cross-linking and swelling behavior, controllable drug release, permeation as well as cellular uptake enhancement, inhibition of efflux pumps and enzymes, complexation of metal ions, antioxidative properties, and radical scavenging activity. Simultaneously, these polymers remain biodegradable without increased toxicity. Within this Review, an overview about the different possibilities to covalently attach sulfhydryl ligands to the polymeric backbone of chitosan is given, and the resulting versatile physiochemical properties are discussed in detail. Furthermore, the broad spectrum of applications for thiolated chitosans in science and industry, ranging from their most advanced use in pharmaceutical and medical science over wastewater treatment to the impregnation of textiles, is addressed.

Development and characterization of exendin-4 loaded self-nanoemulsifying system and in vitro evaluation on Caco-2 cell line

Aim: Aim of this study was to develop exendin-4 and exendin-4/chymostatin loaded self-nanoemulsifying drug delivery system (SNEDDS).Methods: Surfactants and co-surfactants were mixed, oil phase containing exendin-4 or exendin-4/chymostatin was added dropwise for SNEDDS. Short term physical stability test was performed prior to the release, lipolysis and permeability studies.Results: SNEDDS containing ethyl oleate: Cremophor EL^®: Labrasol^®: propylene glycole (15:42.5:21.25: 21.25) were selected for in vitro release and intestinal permeability studies for suitable parameters and physical stability test results. SNEDDS were obtained which yielded Grade B nanoemulsions having droplet size below 25 nm. In vitro release studies showed that 73.79% of the peptide was released for 2 h at pH 6.8. Both exendin-4 and exendin-4/chymostatin loaded SNEDDS were non-toxic to Caco-2 cells. Permeability coefficients of both exendin-4 loaded SNEDDS and exendin-4/chymostatin loaded SNEDDS were higher than exendin-4 solution.Conclusions: Intestinal permeability of exendin-4 has been improved by SNEDDS formulations.

A new medium-throughput screening design approach for the development of hydroxymethylnitrofurazone (NFOH) nanostructured lipid carrier for treating leishmaniasis

Hydroxymethilnitrofurazone (NFOH) is a nitrofurazone derivative and has potential use in treating leishmaniasis. However, due to low water solubility and bioavailability, NFOH has failed in in vivo tests. Nanostructured lipid carrier (NLC) is an alternative to overcome these limitations by improving pharmacokinetics and modifying drug delivery. This work is focused on developing a novel NFOH-loaded NLC (NLC-NFOH) using a D-optimal mixture statistical design and high-pressure homogenization, for oral administration to treat leishmaniasis. The optimized NLC-NFOH consisted of Mygliol® 840, Gelucire® 50/13, and Precirol® ATO 5 as lipids. These lipids were selected using a rapid methodology Technobis Crystal 16 T M, microscopy, and DSC. Different tools for selecting lipids provided relevant scientific knowledge for the development of the NLC. NLC-NFOH presented a z-average of 198.6 ± 5.4 nm, PDI of 0.11 ± 0.01, and zeta potential of -13.7 ± 0.7 mV. A preliminary in vivo assay was performed by oral administration of NLC-NFOH (2.8 mg/kg) in one healthy male Wistar rat (341 g) by gavage. Blood from the carotid vein was collected, and the sample was analyzed by HPLC. The plasma concentration of NFOH after 5 h of oral administration was 0.22 μg/mL. This same concentration was previously found using free NFOH in the DMSO solution (200 mg/kg), which is an almost 100-fold higher dose. This study allowed a design space development approach of the first NLC-NFOH with the potential to treat leishmaniasis orally.

Development and In Vitro Evaluation of Stearic Acid Phosphotyrosine Amide as New Excipient for Zeta Potential Changing Self-Emulsifying Drug Delivery Systems

PURPOSE

Development of zeta potential changing SEDDS containing newly synthesized derivative stearic acid phosphotyrosine amide.

METHODS

Stearoyl chloride was conjugated with phosphotyrosine, which is substrate for the brush border enzyme intestinal alkaline phosphate. The synthesized derivative was implemented in different SEDDS formulations and the zeta potential changing properties and the concluding mucus diffusion abilities were evaluated.

RESULTS

Stearic acid phosphotyrosine amide was successfully synthesized and incorporated into SEDDS. A SEDDS formulation containing the new derivative showed a zeta potential of -14 mV before, and + 2 mV after enzymatic cleavage by intestinal alkaline phosphatase. Experiments on a Caco-2 monolayer demonstrated that the phosphate cannot only be cleaved by isolated enzyme, but also by enzyme, which was expressed by cells. The mucus diffusion abilities of the untreated, negatively charged SEDDS were significantly higher compared to the enzymatically cleaved, positively charged SEDDS.

CONCLUSION

The developed stearic acid phosphotyrosine represents a promising excipient for zeta potential changing SEDDS. Graphical Abstract.

Nanoformulation strategies for improving intestinal permeability of drugs: A more precise look at permeability assessment methods and pharmacokinetic properties changes

The therapeutic efficacy of orally administered drugs is often restricted by their inherent limited oral bioavailability. Low water solubility, limited permeability through the intestinal barrier, instability in harsh environment of the gastrointestinal (GI) tract and being substrate of the efflux pumps and the cytochrome P450 (CYP) can impair oral drug bioavailability resulting in erratic and variable plasma drug profile. As more drugs with low membrane permeability are developed, new interest is growing to enhance their intestinal permeability and bioavailability. A wide variety of nanosystems have been developed to improve drug transport and absorption. Sufficient evidence exists to suggest that nanoparticles are able to increase the transepithelial transport of drug molecules. However, key questions remained unanswered. What types of nanoparticles are more efficient? What are preclinical (or clinical) achievements of each type of nanoformulation in terms of pharmacokinetic (PK) parameters? Addressing this issue in this paper, we have reviewed the current literature regarding permeability enhancement, permeability assessment methods and changes in PK parameters following administration of various nanoformulations. Although permeability enhancement by various nanoformulations holds great promise for oral drug delivery, many challenges still need to be addressed before development of more clinically successful nanoproducts.

Chitosan-Coated Alginate Nanoparticles Enhanced Absorption Profile of Insulin Via Oral Administration

BACKGROUND

In this study, four nanoparticle formulations (F1 to F4) comprising varying ratios of alginate, Pluronic F-68 and calcium chloride with a constant amount of insulin and chitosan as a coating material were prepared using polyelectrolyte complexation and ionotropic gelation methods to protect insulin against enzymatic degradation.

METHODS

This study describes the formulation design, optimisation, characterisation and evaluation of insulin concentration via oral delivery in rats. A reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated to quantify insulin concentration in rat plasma. The proposed method produced a linear response over the concentration range of 0.39 to 50 µg/ml.

RESULTS

In vitro release study showed that dissolution of insulin in simulated gastric juice of pH 1.2 was prevented by alginate core and chitosan coating but rapidly released in simulated intestinal fluid (pH 6.8). Additionally, Formulation 3 (F3) has a particle size of 340.40 ± 2.39 nm with narrow uniformity exhibiting encapsulation efficiency (EE) of 72.78 ± 1.25 % produced highest absorption profile of insulin with a bioavailability of 40.23 ±1.29% and reduced blood glucose after its oral administration in rats.

CONCLUSION

In conclusion, insulin oral delivery system containing alginate and chitosan as a coating material has the ability to protect the insulin from enzymatic degradation thus enhance its absorption in the intestine. However, more work should be done for instance to involve human study to materialise this delivery system for human use.

Evaluation of self-emulsifying drug delivery systems for oral insulin delivery using an in vitro model simulating the intestinal proteolysis

The gentle preparation and the functionalization potential of self-emulsifying drug delivery systems (SEDDS) make them an interesting formulation strategy for oral administration of peptide and protein (p/p) drugs. A series of Kolliphor® RH40 (RH40) and Labrasol® (LAB)-based SEDDS containing either long-chain (LC) or medium-chain (MC) glycerides were formulated and characterized with regard to their rheological behavior, as well as the size distribution and zeta potential of the generated emulsions. Insulin, in order to be incorporated in SEDDS, was complexed with soybean phosphatidylcholine. The ability of different SEDDS to protect the incorporated insulin against enzymatic hydrolysis was evaluated by an in vitro model simulating the intestinal proteolysis. SEDDS were incubated in simulated intestinal fluids in the presence of α-Chymotrypsin (α-CT), and HPLC was used to quantify the remaining insulin. Principal component analysis (PCA) was applied to identify the relations between different excipients and properties of SEDDS that describe the SEDDS protective effect on insulin during in vitro proteolysis. The RH40-SEDDS behaved Newtonian in the presence of ethanol (EtOH) and non-Newtonian in the absence of EtOH, which generated emulsion with droplets between 30 to 300 nm. The LAB-SEDDS always behaved Newtonian and generated polydisperse emulsions with broad size distribution (190-4000 nm). During the in vitro proteolysis, insulin can be effectively protected against α-CT (> 60% remaining insulin after 60 min in vitro proteolysis). According to PCA analysis, insulin was better protected in MC-SEDDS compared to LC-SEDDS, and better in LAB-SEDDS compared to RH40-SEDDS. Monoacyl phosphatidylcholine and Capmul® MCM C8 were recognized as excipients favored for SEDDS protection on insulin. However, SEDDS viscosity and the addition of EtOH in SEDDS played insignificant roles on the remaining insulin after in vitro proteolysis. In summary, an in vitro proteolysis model with increased physiological relevance was applied to enable the optimal design of SEDDS for oral p/p drug delivery.

Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature

Thiolated polymers designated "thiomers" are obtained by covalent attachment of thiol functionalities on the polymeric backbone of polymers. In 1998 these polymers were first described as mucoadhesive and in situ gelling compounds forming disulfide bonds with cysteine-rich substructures of mucus glycoproteins and crosslinking through inter- and intrachain disulfide bond formation. In the following, it was shown that thiomers are able to form disulfides with keratins and membrane-associated proteins exhibiting also cysteine-rich substructures. Furthermore, permeation enhancing, enzyme inhibiting and efflux pump inhibiting properties were demonstrated. Because of these capabilities thiomers are promising tools for drug delivery guaranteeing a strongly prolonged residence time as well as sustained release on mucosal membranes. Apart from that, thiomers are used as drugs per se. In particular, for treatment of dry eye syndrome various thiolated polymers are in development and a first product has already reached the market. Within this review an overview about the thiomer-technology and its potential for different applications is provided discussing especially the outcome of studies in non-rodent animal models and that of numerous clinical trials. Moreover, an overview on product developments is given.

Recent Advancements in Non-Invasive Formulations for Protein Drug Delivery

Advancements in biotechnology and protein engineering expand the availability of various therapeutic proteins including vaccines, antibodies, hormones, and growth factors. In addition, protein drugs hold many therapeutic advantages over small synthetic drugs in terms of high specificity and activity. This has led to further R&D investment in protein-based drug products and an increased number of drug approvals for therapeutic proteins. However, there are many biological and biopharmaceutical obstacles inherent to protein drugs including physicochemical and enzymatic destabilization, which limit their development and clinical application. Therefore, effective formulations of therapeutic proteins are needed to overcome the various physicochemical and biological barriers. In current medical practice, protein drugs are predominantly available in injectable formulations, which have disadvantages including pain, the possibility of infection, high cost, and low patient compliance. Consequently, non-invasive drug delivery systems for therapeutic proteins have gained great attention in the research and development of biomedicines. Therefore, this review covers the various formulation approaches to optimizing the delivery properties of protein drugs with an emphasis on improving bioavailability and patient compliance. It provides a comprehensive update on recent advancements in nanotechnologies with regard to non-invasive protein drug delivery systems, which is also categorized by the route of administrations including oral, nasal, transdermal, pulmonary, ocular, and rectal delivery systems.

SEDDS: A game changing approach for the oral administration of hydrophilic macromolecular drugs

Since the development of self-emulsifying drug delivery systems (SEDDS) in 1980's, they attract the attention of researchers in order to confront the challenge of poor water-solubility of orally given drugs. Within recent years, SEDDS were also discovered for oral administration of hydrophilic macromolecular drugs such as peptides, proteins, polysaccharides and pDNA. Due to hydrophobic ion pairing (HIP) with oppositely charged lipophilic auxiliary agents the resulting complexes can be incorporated in the lipophilic phase of SEDDS. Depending on the solubility of the complex in the SEDDS pre-concentrate and in the release medium drug release can be adjusted on purpose by choosing more or less lipophilic auxiliary agents in appropriate quantities for HIP. Within the oily droplets formed in the GI-tract drugs are protected towards degradation by proteases and nucleases and thiol-disulfide exchange reactions with dietary proteins. The oily droplets can be made mucoadhesive or highly mucus permeating depending on their target site. Furthermore, even their cellular uptake properties can be tuned by adjusting their zeta potential or decorating them with cell penetrating peptides. The potential of SEDDS for oral administration of hydrophilic macromolecular drugs could meanwhile be demonstrated via various in vivo studies showing a bioavailability at least in the single digit percentage range. Owing to these properties advanced SEDDS turned out to be a game changing approach for the oral administration of hydrophilic macromolecular drugs.

Lipids and polymers in pharmaceutical technology: Lifelong companions

In pharmaceutical technology, lipids and polymers are considered pillar excipients for the fabrication of most dosage forms, irrespective of the administration route. They play various roles ranging from support vehicles to release rate modifiers, stabilizers, solubilizers, permeation enhancers and transfection agents. Focusing on selected applications, which were discussed at the Annual Scientific Meeting of the Gattefossé Foundation 2018, this manuscript recapitulates the fundamental roles of these two important classes of excipients, either employed alone or in combination, and provides insight on their functional properties in various types of drug formulations. Emphasis is placed on oral formulations for the administration of active pharmaceutical ingredients with low aqueous solubilities or poor permeation properties. Additionally, this review article covers the use of lipids and polymers in the design of colloidal injectable delivery systems, and as substrates in additive manufacturing technologies for the production of tailor-made dosage forms.

Oral Bioavailability and Lymphatic Transport of Pueraria Flavone-Loaded Self-Emulsifying Drug-Delivery Systems Containing Sodium Taurocholate in Rats

We developed self-microemulsifying drug-delivery systems (SMEDDS), including bile salts, to improve the oral bioavailability of pueraria flavones (PFs). The physical properties of the SMEDDS using Cremophor RH 40, and bile salts as mixed surfactants at weight ratios of 10:0⁻0:10 were determined. The particle sizes of PFs-SMEDDS_NR containing sodium taurocholate (NaTC) and Cremophor RH 40, and PFs-SMEDDS_R containing Cremophor RH 40 were measured upon dilution with deionized water and other aqueous media. Dilution volume presented no remarkable effects on particle size, whereas dilution media slightly influenced particle size. PFs-SMEDDS_NR and PFs-SMEDDS_R provided similar release rates in pH-1.2 hydrochloride solution. However, the release rate of PFs-SMEDDS_NR was faster than that of PFs-SMEDDS_R in pH-6.8 phosphate buffer containing 20 mM NaTC and 500 U/mL porcine pancreas lipase. The pharmacokinetics and bioavailability were measured in rats. The oral bioavailability of PFs-SMEDDS_NR was 2.57- and 2.28-fold that of a suspension of PFs (PFs-suspension) before and after the blockade of the lymphatic transport route by cycloheximide, respectively. These results suggested PFs-SMEDDS_NR could significantly improve the oral relative absorption of PFs via the lymphatic uptake pathway. SMEDDS containing NaTC may provide an effective approach for enhancing the oral bioavailability of PFs.

Recent advances of polysaccharide-based nanoparticles for oral insulin delivery

Diabetes mellitus is a highly prevalent metabolic and chronic disease affecting millions of people in the world. The most common route of insulin therapy is the subcutaneous injection due to its low bioavailability and enzymatic degradation. The search for effective and high patient compliance insulin delivery systems has been a major challenge over many decades. The polysaccharide-based nanoparticles as delivery vehicles for insulin oral administration have recently attracted substantial interests. The present review highlights the recent advances on the development of nanoparticles prepared from polysaccharides, including chitosan, alginate, dextran and glucan, for oral delivery of insulin, overcoming multiple barriers in gastrointestinal tract. The aims of this review are first to summarize the strategies that have been applied in the past 5 years to fabricate polysaccharide-based nanoparticles for insulin oral delivery, and then to provide in-depth understanding on the mechanisms by which such nanoparticles protect insulin against degradation in the digestive tract and provide sustained release to enhance mucus permeation and transepithelial transport of insulin administered via oral route.

Impact of digestion on the transport of dextran-loaded self-emulsified nanoemulsion through MDCK epithelial cell monolayer and rat intestines

Many of the lipids and surfactants used to prepare the self-emulsified nanoemulsion (SEN) are subjected to the gastro-intestinal enzymatic digestion, which may affect the absorption of the loaded drug. The present study was to investigate the impact of such digestion on the transport of hydrophilic macromolecules (10-kDa dextran as the model compound) loaded in SEN through the MDCK cell monolayer and ex-vivo rat intestines. FITC-labeled dextran (FD) was loaded inside the inner oil phase of SEN by the formation of FD-phospholipid solid dispersion (FDPS). After digestion, the droplet size increased from 31.06 ± 2.10 nm to 494.6 ± 22.1 nm, and the FD content in the external aqueous phase increased from 41.6 ± 4.2% to 61.1 ± 4.4%. Compared to the FD solution, SEN without digestion enhanced the transport of FD through MDCK cell monolayer 4.1 times and through rat intestines 3.0-7.4 times. However, the digestion reduced the transport of FD 3.5 times through MDCK cell monolayer and 1.3-2.0 times through rat intestines, compared to that without digestion. This reduction was due to the destruction of lipid nano-droplets and release of FD to the external aqueous phase of SEN. This finding should be considered when SEN is used as a delivery system for hydrophilic macromolecules.

Oral insulin delivery: existing barriers and current counter-strategies

Objectives

The chronic and progressive nature of diabetes is usually associated with micro- and macrovascular complications where failure of pancreatic β-cell function and a general condition of hyperglycaemia is created. One possible factor is failure of the patient to comply with and adhere to the prescribed insulin due to the inconvenient administration route. This review summarizes the rationale for oral insulin administration, existing barriers and some counter-strategies trialled.

Key findings

Oral insulin mimics the physiology of endogenous insulin secreted by pancreas. Following the intestinal absorption of oral insulin, it reaches the liver at high concentration via the portal vein. Oral insulin on the other hand has the potential to protect pancreatic β-cells from autoimmune destruction. Structural modification, targeting a particular tissue/receptor, and the use of innovative pharmaceutical formulations such as nanoparticles represent strategies introduced to improve oral insulin bioavailability. They showed promising results in overcoming the hurdles facing oral insulin delivery, although delivery is far from ideal.

Summary

The use of advanced pharmaceutical technologies and further research in particulate carrier system delivery predominantly nanoparticle utilization would offer useful tools in delivering insulin via the oral route which in turn would potentially improve diabetic patient compliance to insulin and the overall management of diabetes.

Can natural polymers assist in delivering insulin orally?

Diabetes mellitus is one of the most grave and lethal non communicable diseases. Insulin is normally used to medicate diabetes. Due to bioavailability issues, the most regular route of administration is through injection, which may pose compliance problems to treatment. The oral administration thus appears as a suitable alternative, but with several important problems. Low stability of insulin in the gastrointestinal tract and low intestinal permeation are some of the issues. Encapsulation of insulin into polymer-based particles emerges as a plausible strategy. Different encapsulation approaches and polymers have been used in this regard. Polymers with different characteristics from natural or synthetic origin have been assessed to attain this goal, with natural polymers being preferable. Natural polymers studied so far include chitosan, alginate, carrageenan, starch, pectin, casein, tragacanth, dextran, carrageenan, gelatine and cyclodextrin. While some promising knowledge and results have been gained, a polymeric-based particle system to deliver insulin orally has not been introduced onto the market yet. In this review, effectiveness of different natural polymer materials developed so far along with fabrication techniques are evaluated.

Novel strategies in the oral delivery of antidiabetic peptide drugs - Insulin, GLP 1 and its analogs

As diabetes is a complex disorder being a major cause of mortality and morbidity in epidemic rates, continuous research has been done on new drug types and administration routes. Up to now, a large number of therapeutic peptides have been produced to treat diabetes including insulin, glucagon-like peptide-1 (GLP-1) and its analogs. The most common route of administration of these antidiabetic peptides is parenteral. Due to several drawbacks associated with this invasive route, delivery of these antidiabetic peptides by the oral route has been a goal of pharmaceutical technology for many decades. Dosage form development should focus on overcoming the limitations facing oral peptides delivery as degradation by proteolytic enzymes and poor absorption in the gastrointestinal tract (GIT). This review focuses on currently developed strategies to improve oral bioavailability of these peptide based drugs; evaluating their advantages and limitations in addition to discussing future perspectives on oral peptides delivery. Depending on the previous reports and papers, the area of nanocarriers systems including polymeric nanoparticles, solid lipid nanoparticles, liposomes and micelles seem to be the most promising strategy that could be applied for successful oral peptides delivery; but still further potential attempts are required to be able to achieve the FDA approved oral antidiabetic peptide delivery system.

Combination of SEDDS and Preactivated Thiomer Technology: Incorporation of a Preactivated Thiolated Amphiphilic Polymer into Self-Emulsifying Delivery Systems

PURPOSE

The aim of the study was to create novel mucoadhesive drug delivery systems by incorporating amphiphilic hydrophobically modified, thiolated and preactivated polymers (preactivated thiomers) into self-emulsifying drug delivery systems (SEDDS).

METHODS

L-Cysteine methyl ester was covalently attached to the polymeric backbone of Pemulen TR-2 and preactivated using 2-mercaptonicotinic acid (2-MNA). These thiomers were incorporated in a concentration of 0.3% (w/v) into SEDDS. The size distribution and the zeta potential of the emulsions were evaluated by dynamic light scattering. Mucoadhesive properties of thiomers-SEDDS spiked with FDA (fluorescein diacetate) were examined utilizing rheological measurement, permeation studies and in vitro residence time study on porcine mucosa. Cell viability tests were additionally performed.

RESULTS

734 ± 58 μmol L-Cysteine methyl ester and 562 ± 71 μmol 2-MNA could be attached per gram polymer of Pemulen TR-2. Emulsions exhibited a droplet size range between 180 and 270 nm. Blank SEDDS possessed a zeta potential value between -5.7 and -8.6 mV, whereas thiomers-SEDDS between -14.6 and -17.2 mV. Viscous modulus of thiomer and preactivated thiomer containing SEDDS-mucus mixture was 8-fold and 11-fold increased in comparison to reference. The amount of FDA permeated the mucus layer was 2-fold lower in case of thiomers-SEDDS compared to blank SEDDS. A prolonged residence time was observed for thiomers-SEDDS over 45 min. During cell viability studies no severe toxic effects were detected.

CONCLUSION

The novel developed SEDDS with incorporated thiomers might be a promising tool for mucoadhesive oral drug delivery.

Nanocarriers protecting toward an intestinal pre-uptake metabolism

Pre-uptake metabolism within the GI tract is responsible for the poor oral bioavailability of numerous drugs. As nanocarriers function as a 'shield', protecting incorporated drugs from enzymatic attack, there is an increasing interest in utilizing them as a tool for overcoming drug degradation. Degradation of carriers resulting in the release of incorporated drugs, mucus permeation, enzyme inhibitory properties and their toxicity are crucial factors that must be taken into account when designing proper nanocarriers. The use of polymer- and lipid-based nanocarriers as protective vehicles are discussed within this review. Lipid-based carriers and novel mucopenetrating particles seem to have a great potential in avoiding metabolizing enzymes. Accordingly, nanocarriers are promising tools for improving the bioavailability of drugs, being sensitive to a pre-uptake metabolism.

Self-emulsifying drug delivery systems (SEDDS): Proof-of-concept how to make them mucoadhesive

AIM

The objective of this study was to provide a proof-of-concept that self-emulsifying drug delivery systems can be made mucoadhesive by the incorporation of hydrophobic mucoadhesive polymers.

METHODS

In order to obtain such a hydrophobic mucoadhesive polymer, Eudragit® S100 was thiolated by covalent attachment of cysteamine. After determination of the thiol group content, in vitro mucoadhesion studies (rotating cylinder and rheological measurements) were performed. Then, synthesized conjugate was incorporated into self-emulsifying drug delivery systems (SEDDS) and their toxic potential as well as that of unmodified and thiolated Eudragit® S100 was examined on Caco-2 cell line. Lastly, the mucoadhesiveness of developed SEDDS on porcine intestinal mucosa was determined.

RESULTS

Generated thiolated Eudragit® S100 displaying 235±14μmol of free thiol groups and 878±101μmol of disulfide bonds per gram polymer showed a great improvement in both: dynamic viscosity with mucus and adhesion time on mucosal tissue compared to the unmodified polymer. Resazurin assay revealed that unmodified and thiolated polymers and also SEDDS dispersions were non-toxic over Caco-2 cells. Furthermore, the incorporation of 1.5% (w/w) of such thiomer into SEDDS led to remarkably improved mucoadhesiveness. Blank SEDDS were completely removed from the mucosa within 15min, whereas >60% of SEDDS containing thiolated Eudragit® S100 were still attached to it.

CONCLUSION

These results provide evidence that SEDDS can be made mucoadhesive by the incorporation of hydrophobic mucoadhesive polymers.

Synthesis and characterization of insulin/zirconium phosphate@TiO2 hybrid composites for enhanced oral insulin delivery applications

In this work, a series of composites of insulin (Ins)/zirconium phosphate (ZrP) were synthesized by intercalation method, then, these composites were coated with TiO₂ by sol-gel method to prepare Ins/ZrP@TiO₂ hybrid composites and the drug release of the composites was investigated by using UV-Vis spectroscopy. Ins/ZrP (10, 30, 60 wt%) composites were prepared by intercalation of insulin into the ZrP layers in water. Then Ins/ZrP composites were coated with different amounts of TiO₂ (30, 50, 100 wt %) by using titanium tetra n-butoxide, as precursor. Formation of intercalated Ins/ZrP and Ins/ZrP@TiO₂ hybrid composites was characterized by FT-IR, FE-SEM, BET and XRD analysis. Zeta potential of the optimized Ins/ZrP@TiO₂ hybrid composite was determined -27.2 mV. Cytotoxic effects of the optimized Ins/ZrP@TiO₂ hybrid composite against HeLa and Hek293T cell lines were evaluated using MTT assay and the results showed that designed drug delivery system was not toxic in biological environment. Compared to the Ins/ZrP composites, incorporation of TiO₂ coating enhanced the drug entrapment considerably, and reduced the drug release. The Ins/ZrP composites without TiO₂ coating released the whole drug after 30 min in pH 7.4 (phosphate buffer solution) while the TiO₂-coated composites released the entrapped drug after 20 h. In addition to increasing the shelf life of hormone, this nanoencapsulation and nanocoating method can convert the insulin utilization from injection to oral and present a painless and more comfortable treatment for diabetics.