Preparation and characterization of enteric microspheres containing bovine insulin by a w/o/w emulsion solvent evaporation method

Advances in rectal drug delivery systems

Drug delivery via the rectum is a useful alternative route of administration to the oral route for patients who cannot swallow. Traditional rectal dosage forms have been historically used for localized treatments including delivery of laxatives, treatment of hemorrhoids and for delivery of antipyretics. However, the recent trend is showing an increase in the development of novel rectal delivery systems to deliver drug directly into the systemic circulation by taking advantage of porto-systemic shunting. The present review is based on research studies carried out between years 1969-2017. Data for this review have been derived from keyword searches using Scopus and Medline databases. Novel rectal drug delivery systems including hollow-type suppositories, thermo-responsive and muco-adhesive liquid suppositories, and nanoparticulate systems incorporated into an appropriate vehicle have offered more control over delivery of drug molecules for local or systemic actions. In addition, various methods for in vitro-in vivo evaluation of rectal drug delivery systems are covered which is as important as the formulation, and must be carried out using appropriate methodology. Continuous research and development in this field of drug delivery may unleash the hidden potential of the rectal drug delivery systems.

Microparticles, microcapsules and microspheres: A review of recent developments and prospects for oral delivery of insulin

Diabetes mellitus is a chronic metabolic health disease affecting the homeostasis of blood sugar levels. However, subcutaneous injection of insulin can lead to patient non-compliance, discomfort, pain and local infection. Sub-micron sized drug delivery systems have gained attention in oral delivery of insulin for diabetes treatment. In most of the recent literature, the terms "microparticles" and "nanoparticle" refer to particles where the dimensions of the particle are measured in micrometers and nanometers respectively. For instance, insulin-loaded particles are defined as microparticles with size larger than 1 μm by most of the research groups. The size difference between nanoparticles and microparticles proffers numerous effects on the drug loading efficiency, aggregation, permeability across the biological membranes, cell entry and tissue retention. For instance, microparticulate drug delivery systems have demonstrated a number of advantages including protective effect against enzymatic degradation, enhancement of peptide stability, site-specific and controlled drug release. Compared to nanoparticulate drug delivery systems, microparticulate formulations can facilitate oral absorption of insulin by paracellular, transcellular and lymphatic routes. In this article, we review the current status of microparticles, microcapsules and microspheres for oral administration of insulin. A number of novel techniques including layer-by-layer coating, self-polymerisation of shell, nanocomposite microparticulate drug delivery system seem to be promising for enhancing the oral bioavailability of insulin. This review draws several conclusions for future directions and challenges to be addressed for optimising the properties of microparticulate drug formulations and enhancing their hypoglycaemic effects.

Novel iron-polysaccharide multilayered microcapsules for controlled insulin release

Iron-polysaccharide complexes have been extensively used for the treatment of iron-deficiency anemia without side-effects. In this study, insulin-loaded microcapsules were prepared via layer-by-layer deposition of oppositely charged Fe(3+) and dextran sulfate (DS) onto the surface of insulin microparticles. Fe(3+) was combined with DS via both electrostatic interaction and chemical complexation process, leading to the formation of a stable complex of Fe(3+)/DS. Subsequently, protamine was used as the outermost layer of the insulin-loaded microcapsules to facilitate nuclear delivery. The sufficient charge reversal with successive deposition cycles and successful fabrication of hollow microcapsules provided strong evidence for the growth of (Fe(3+)/DS)(n) multilayer on the surface of microparticles. The experiments showed that the microcapsules successfully entrapped insulin with encapsulation efficiency of 70.56+/-0.97% and drug loading content of 46.15+/-0.97%. It was found that the release time and hypoglycemic effect increased as the number of deposited bilayers increased. The insulin-loaded microcapsules significantly improved glucose tolerance from 2 h (free insulin) to even 12 h (insulin-loaded microcapsules with 10 bilayers). Moreover, the microcapsules with protamine as the outermost layer displayed a prolonged and stable glucose-lowering profile over a period of over 6 h compared with Fe(3+) as the outermost layer. These findings indicate that such microcapsules can be a promising approach for the construction of an effective controlled release delivery system of insulin as well as other proteins with short half-life time.

Investigation on processing variables for the preparation of fluconazole-loaded ethyl cellulose microspheres by modified multiple emulsion technique

Fluconazole-loaded ethyl cellulose microspheres were prepared by alginate facilitated (water-in-oil)-in-water emulsion technology and the effects of various processing variables on the properties of microspheres were investigated. Scanning electron microscopy revealed spherical nature and smooth surface morphology of the microspheres except those prepared at higher concentration of emulsifiers and higher stirring speeds. The size of microspheres varied between 228 and 592 mum, and as high as 80% drug entrapment efficiency was obtained depending upon the processing variables. When compared up to 2 h, the drug release in pH 1.2 HCl solution was slower than in pH 7.4 phosphate buffer saline solution. However, this trend was reversed at high shear conditions. The microspheres provided extended drug release in alkaline dissolution medium and the drug release was found to be controlled by Fickian-diffusion mechanism. However, the mechanism shifted to anomalous diffusion at high shear rates and emulsifier concentrations. The aging of microspheres did not influence the drug release kinetics. However, the physical interaction between drug and excipients affected the drug dissolution behaviors. X-ray diffractometry (X-RD) and differential scanning calorimetry (DSC) analysis revealed amorphous nature of drug in the microspheres. Fourier transform infrared (FTIR) spectroscopy indicated stable character of fluconazole in the microspheres. The stability testing data also supported the stable nature of fluconazole in the microspheres. The fluconazole extracted from 80% drug-loaded formulation showed good in vitro antifungal activity against Candida albicans. Thus, proper control of the processing variables involved in this modified multiple emulsion technology could allow effective incorporation of slightly water soluble drugs into ethyl cellulose microspheres without affecting drug stability.

Gastrointestinal absorption enhancement of insulin by administration of enteric microspheres and SNAC to rats

The preparation and characteristics of insulin enteric microspheres (EMS) were studied and the gastrointestinal absorption enhancement of insulin by co-administering EMS with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC) was determined. The w/o/w and o(1)/o(2) emulsion solvent evaporation methods were used to prepare insulin-hydroxypropyl methylcellulose phthalate (HPMCP) EMS. High-performance liquid chormatography determined the drug loading, entrapment efficiency, stability to pepsin, and drug dissolution rate in hydrochloric acid solution (pH 1.2) and phosphate buffer solution (pH 6.8). The hypoglycaemic effect was studied by orally administrating the insulin EMS and SNAC to rats. The particle size of EMS (o(1)/o(2)) and EMS (w/o/w) was about 500 and 30 micro m respectively, and drug loading was 7 and 3% respectively. After being incubated with 18 micro g/mL pepsin solution (pH 1) at 37 degrees C, only 20% of insulin in EMS (o(1)/o(2)) was digested within 4 h, while 60% of the insulin in EMS (w/o/w) was digested within 1 h. In hydrochloric acid solution (pH 1.2), EMS (o(1)/o(2)) had less drug dissolution than EMS (w/o/w). In phosphate buffer solution (pH 6.8), the entire drug release time of EMS (o(1)/o(2)) and EMS (w/o/w) was 75 and 10 min, respectively. After orally administering with SNAC, EMS (o(1)/o(2)) could decrease the blood glucose level of rats remarkably and maintain the hypoglycaemic effect for 4 h, while EMS (w/o/w) had just a weakly hypoglycaemic effect. The results showed that the characteristics-optimized EMS, i.e. EMS (o(1)/o(2)) incorporating SNAC, could enhance insulin absorption significantly in the gastrointestional tract by taking advantage of both protection from enzyme degradation and improvement of drug permeability.

Polymeric particulates to improve oral bioavailability of peptide drugs

Oral administration remains the most convenient way of delivering drugs. Recent advances in biotechnology have produced highly potent new molecules such as peptides, proteins and nucleic acids. Due to their sensitivity to chemical and enzymatic hydrolysis as well as a poor cellular uptake, their oral bioavailability remains very low. Despite sophisticated new delivery systems, the development of a satisfactory oral formulation remains a challenge. Among the possible strategies to improve the absorption of drugs, micro- and nanoparticles represent an exciting approach to enhance the uptake and transport of orally administered molecules. Increasing attention has been paid to their potential use as carriers for peptide drugs for oral administration.

This article reviews the most common manufacturing methods for polymeric particles and the physiology of particle absorption from the gastrointestinal (GI) tract. In a second part, the use of polymeric particulate systems to improve the oral absorption of insulin is discussed.

Cross-linked high amylose starch derivatives as matrices for controlled release of high drug loadings

Selection of hydrogels as excipients in controlled drug release systems depends on the characteristics of the gel and of the drug. Three types of derivatives were synthesized from cross-linked high amylose starch (HASCL-6) by substitution of hydroxylic groups with cationic (carboxymethyl: CM), anionic (aminoethyl: AE) and acetate (Ac) groups. These new polymeric excipients are able to control the release over 20 h from monolithic tablets loaded with 20 to 60% drug. Three drugs were used as model tracer: acetaminophen (uncharged), acetylsalicylic acid (having an acidic group) and metformin (having a basic group). It was found that the release of ionic drugs from CM-HASCL-6 and AE-HASCL-6 matrices can be partially controlled by ionic interaction between pendant groups of polymer and drugs. The substitution degree of HASCL-6 derivatives can also be varied to modulate the drug's release time. These derivatives represent a novel generation of pharmaceutical excipients, recommended for high loading dosage formulations.

Basic study for stabilization of w/o/w emulsion and its application to transcatheter arterial embolization therapy

Stabilization of w/o/w emulsion and its application to transcatheter arterial embolization (TAE) therapy are reviewed. W/o/w emulsion was stabilized by making inner aqueous phase hypertonic, addition of chitosan in inner phase, and techniques of phase-inversion with porous membrane. Lipiodol w/o/w emulsion for TAE therapy was prepared by using a two-step pumping emulsification procedure. The procedure is so easy that the emulsion could be prepared even during the surgical operation. The deposition after hepatic arterial administration of the emulsion was detected by an X-ray CT scanner. The concentration of epirubicin hydrochloride (EPI) in liver was increased and its residence was prolonged by encapsulating it in the w/o/w emulsion. The toxic effects of EPI and lipiodol on the normal hepatic cells were reduced. The w/o/w emulsion prepared by us is a suitable formulation for the TAE therapy.