Microparticles for delivering therapeutic peptides and proteins to the lumen of the small intestine

Metformin Hydrochloride Loaded Mucoadhesive Microspheres and Nanoparticles for Anti-Hyperglycemic and Anticancer Effects Using Factorial Experimental Design

Background

Metformin hydrochloride (HCl) microspheres and nanoparticles were formulated to enhance bioavailability and minimize side effects through sustained action and optimized drug-release characteristics. Initially, the same formulation design with different ratios of metformin HCl and Eudragit RSPO was used to formulate four batches of microspheres and nanoparticles using solvent evaporation and nanoprecipitation methods, respectively.

Methods

The produced formulations were evaluated based on particle size and shape (particle size distribution (PSD), scanning electron microscope (SEM)), incompatibility (differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR)), drug release pattern, permeation behavior, in vivo hypoglycemic effects, and in vitro anticancer potential.

Results

Compatibility studies concluded that there was minimal interaction between metformin HCl and the polymer, whereas SEM images revealed smoother, more spherical nanoparticles than microspheres. Drug release from the formulations was primarily controlled by the non-Fickian diffusion process, except for A1 and A4 by Fickian, and B3 by Super case II. Korsmeyer-Peppas was the best-fit model for the maximum formulations. The best formulations of microspheres and nanoparticles, based on greater drug release, drug entrapment, and compatibility characteristics, were attributed to the study of drug permeation by non-everted intestinal sacs, in vivo anti-hyperglycemic activity, and in vitro anticancer activity.

Conclusion

This study suggests that the proposed metformin HCl formulation can dramatically reduce hyperglycemic conditions and may also have anticancer potential.

Triggered and controlled release of bioactives in food applications

Bioactive compounds (e.g., nutraceuticals, micronutrients, antimicrobial, antioxidant) are added to food products and formulations to enhance sensorial/nutritional attributes and/or shelf-life. Many of these bioactives are susceptible to degradation when exposed to environmental and processing factors. Others involve in undesirable interactions with food constituents. Encapsulation is a useful tool for addressing these issues through various stabilization mechanisms. Besides protection, another important requirement of encapsulation is to design a carrier that predictably releases the encapsulated bioactive at the target site to elicit its intended functionality. To this end, controlled release carrier systems derived from interactive materials have been developed and commercially exploited to meet the requirements of various applications. This chapter provides an overview on basic controlled and triggered release concepts relevant to food and active packaging applications. Different approaches to encapsulate bioactive compounds and their mode of release are presented, from simple blending with a compatible matrix to complex multiphase carrier systems. To further elucidate the mass transport processes, selected diffusion and empirical release kinetic models are presented, along with their brief historical significance. Finally, interactive carriers that are responsive to moisture, pH, thermal and chemical stimuli are presented to illustrate how these triggered release mechanisms can be useful for food applications.

Inhibition of Methamphetamine-Induced Cytotoxicity in the U87-Cell Line by Atorvastatin-Conjugated Carbon Nanotubes

In biological systems, carbon nanotubes can enhance the biological effects of drugs and reduce their side effects. Methamphetamine (METH) is a stimulant drug that induces cell death in various cell types, primarily neural cells. On the other hand, specific doses of atorvastatin (ATO) can stimulate cell growth and inhibit cell death in different cell lines. This study aimed to investigate the improvement effect of ATO@single-walled carbon nanotube (SWCNT) on METH-induced cell cytotoxicity in the U87 glioblastoma cell line. In this study, cells were cultured in 10 mM of METH during the cell treatment with 0-10 nM of ATO and ATO@SWCNT. The conjugated drugs to SWCNT as Van der Waals were detected using field emission scanning electron microscopy, Fourier transform-infrared spectroscopy, and other analyses. Then, the in vitro proliferating of ATO@SWCNT was explored against glioblastoma cells compared to pure ATO. This examine was performed using methyl thiazole tetrazolium approach, terminal deoxynucleotidyl transferase deoxy uridine-triphosphate nick end labeling assay, caspase-3 method, lactate dehydrogenase assay, and RH-123 assay with 10 mM METH. The results obtained from transmission electron microscopy analysis showed the average size of 50 nm for ATO@SWCNT. This study indicated that U87 cells, which were exposed to METH and suffered cell death, were severely reduced in the presence of ATO, especially ATO@SWCNT (for its anti-apoptotic effect), but they survived. This study suggests that ATO, which was primarily used to reduce blood lipids, can significantly reduce brain cell death. The findings of this study indicate that by using SWCNT, more drugs can reach the target cells. This method reduces the total amount of required medication and shows a more beneficial therapeutic effect.

Microparticulate and nanoparticulate drug delivery systems for metformin hydrochloride

CONTEXT

Metformin hydrochloride is a biguanide derivative widely used for the treatment of type 2 diabetes, prescribed nearly to 120 million people worldwide. Metformin has a relatively low oral bioavailability (about 50-60%). Although the major effect of metformin is to decrease hepatic glucose output as an antihyperglycemic agent, its inhibitory effects on the proliferation of some cancer cells (e.g. prostate, breast, glioma cells) have been demonstrated in the cell culture studies. Development of novel formulation (e.g. microparticles, nanoparticles) strategies for metformin might be useful to improve its bioavailability, to reduce the dosing frequency, to decrease gastrointestinal side effects and toxicity and to be helpful for effective use of metformin in cancer treatment.

OBJECTIVE

The main aim of this review is to summarize metformin HCl-loaded micro- and nanoparticulate drug delivery systems.

METHOD

The literature was rewieved with regard to the physicochemical, pharmacological properties of metformin, and also its mechanism of action in type 2 diabetes and cancer. In addition, micro- and nanoparticulate drug delivery systems developed for metformin were gathered from the literature and the results were discussed.

CONCLUSION

Metformin is an oral antihyperglycemic agent and also has potential antitumorigenic effects. The repeated applications of high doses of metformin (as immediate release formulations) are needed for an effective treatment due to its low oral bioavailability and short biological half-life. Drug delivery systems are very useful systems to overcome the difficulties associated with conventional dosage forms of metformin and also for its effective use in cancer treatment.

Preparation and characterization of metformin hydrochloride loaded-Eudragit®RSPO and Eudragit®RSPO/PLGA nanoparticles

The aim of the present study was to develop and characterize metformin HCl-loaded nanoparticle formulations. Nanoparticles were prepared by the nanoprecipitation method using both a single polymer (Eudragit(®)RSPO) and a polymer mixture (Eudragit/PLGA). The mean particle size ranged from 268.8 to 288 nm and the nanoparticle surface was positively charged (9.72 to 10.1 mV). The highest encapsulation efficiency was observed when Eudragit®RSPO was used. All formulations showed highly reproducible drug release profiles and the in vitro drug release in phosphate buffer (pH = 6.8) ranged from 92 to 100% in 12 h. These results suggest that Eudragit(®)RSPO or Eudragit/PLGA nanoparticles might represent a promising sustained-release oral formulation for metformin HCl, reducing the necessity of repeated administrations of high doses to maintain effective plasma concentrations, and thus, increasing patient compliance and reducing the incidence of side-effects.

Formulation-based approach to support early drug discovery and development efforts: a case study with enteric microencapsulation dosage form development for a triarylmethane derivative TRAM-34; a novel potential immunosuppressant

BACKGROUND

Enteric microencapsulation of the potential immunosuppressant TRAM-34 was investigated as a means of enhancing oral drug delivery and minimizing or eliminating hydrolysis of pyrazole-substituted triarylmethane to the respective alcohol.

METHOD

TRAM-34 was successfully enteric microencapsulated by a coacervation method using the pH-sensitive Eudragit L 100 polymer. In this study, we utilized water-miscible organic solvents such as acetone and ethanol, which are considered safe class 3 solvents according to the ICH guideline. We deemed such an approach suitable for safe scale up and for enteric coating application to other compounds of a similar lipophilicity.

RESULTS

The resulting microparticles were spherical and uniform with an average particle size of 460 microm at 15% theoretical loading. The encapsulation efficiency was 90 +/- 1.9% and the percentage yield was found to be 91.5 +/- 0.3%. The oral administration in rhesus macaques of TRAM-34-loaded enteric-coated microparticles illustrated six times enhancement in its oral bioavailability. However, the TRAM-34 plasma concentration was less than the therapeutic effective level.

CONCLUSION

The low oral bioavailability, even after enteric coating, could be attributed to the compound's inherent absorption characteristics and high lipophilicity.

Improving the stability of insulin in solutions containing intestinal proteases in vitro

Degradation of insulin was studied in this work. Casein and protamine could obviously suppress degradation of insulin by intestinal enzymes, and could protect insulin from degradation by the mechanism of competition and combination with proteolysis enzyme. What is more, co-incubated with HP-β-CD-casein or HP-β-CD-protamine, most insulin was protected from degradation by intestinal enzymes. In addition, it was found that the complexation of insulin with HP-β-CD was characterized by UV absorption spectra. These results indicated that HP-β-CD, casein and protamine could offer some positive and useful results, and could protect insulin from degradation during their transit through the intestinal tract.

Preparation and characterization of poly(methyl methacrylate) - iron (III) oxide microparticles using a modified solvent evaporation method

At present, there is widespread interest in developing new, biocompatible microparticles made from polymers such as poly(methyl methacrylate) (PMMA) that could have applications ranging from diagnostic imaging to drug delivery. In these experiments, there were two primary objectives: (1) to stabilize a suspension of iron (III) oxide (alpha-Fe(2)O(3); mean diameter = 100 nm) nanoparticles in a solution of PMMA by using an emulsifier and different mixtures of two miscible solvents; and (2) to fabricate PMMA-alpha-Fe(2)O(3) microparticles by using an oil-in-water (o/w) solvent evaporation method. By accomplishing the first objective, it was hypothesized that the encapsulation efficiency of alpha-Fe(2)O(3) within PMMA microparticles would improve and induce the clustering of alpha-Fe(2)O(3) along the circumferential edges of the microparticles. Of the seven emulsifiers tested, Tween 80 was selected primarily for its hydrophilicity and its ability to produce a stable alpha-Fe(2)O(3) dispersion. As a result, 22 batches of microspheres (11 with Tween 80 and 11 without) were made and the solvent (dichloromethane) to co-solvent (ethyl acetate) ratios were varied. Particles made with solvent mixtures of >50% ethyl acetate (<50% dichloromethane) were more likely to be hollow and had larger mean volumetric particle diameters (>5 microns) than particles made with mixtures containing >50% dichloromethane. Particles made with Tween 80 were larger, more porous, and had alpha-Fe(2)O(3) aligned along the circumferential edges of the particles. The use of solvent mixtures did not improve the encapsulation efficiency of alpha-Fe(2)O(3) but the use of ethyl acetate helped to induce the clustering of alpha-Fe(2)O(3) along the peripheries of the microparticles.

Eudragit RS 100 microparticles containing 2-hydroxypropyl-beta-cyclodextrin and glutathione: physicochemical characterization, drug release and transport studies

The aim of this study was to encapsulate glutathione (GSH) alone or in combination with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) in Eudragit RS 100 microparticles (MPs), and to evaluate these novel delivery systems for oral administration of the considered tripeptide. The MPs were prepared by an O/O emulsion-solvent evaporation method according to a multilevel experimental design involving the volume of liquid paraffin, the HP-beta-CD amount, and the drug/polymer ratio as independent variables. The effects of these parameters on particle size, entrapment efficiency, and drug release were investigated. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) studies were performed to evaluate possible interactions between GSH and Eudragit RS 100 polymer and to characterize the physical state of drug within the MPs. The release profiles of GSH from MPs were examined in vitro at pH 1.2, 6.8. and 7.4 using the USP III (BioDis) dissolution apparatus. In general, a slow and zero-order release of GSH from MPs at pH 1.2 occurred, while at higher pH values considerable amounts of glutathione disulfide (i.e., GSSG) were observed. The enzymatic stability and the intestinal permeability of some GSH-containing MPs were assessed by using pepsin, alpha-chymotrypsin, gamma-glutamyl-transpeptidase and everted frog intestinal sac methodology, respectively. The results suggest that GSH-loaded Eudragit RS 100 MPs containing HP-beta-CD represent a new sustained GSH delivery system useful for the oral administration of the examined tripeptide.

Design and evaluation of colon specific drug delivery system containing flurbiprofen microsponges

The purpose of this study was to design novel colon specific drug delivery system containing flurbiprofen (FLB) microsponges. Microsponges containing FLB and Eudragit RS 100 were prepared by quasi-emulsion solvent diffusion method. Additionally, FLB was entrapped into a commercial Microsponge 5640 system using entrapment method. Afterwards, the effects of drug:polymer ratio, inner phase solvent amount, stirring time and speed and stirrer type on the physical characteristics of microsponges were investigated. The thermal behaviour, surface morphology, particle size and pore structure of microsponges were examined. The colon specific formulations were prepared by compression coating and also pore plugging of microsponges with pectin:hydroxypropylmethyl cellulose (HPMC) mixture followed by tabletting. In vitro dissolution studies were done on all formulations and the results were kinetically and statistically evaluated. The microsponges were spherical in shape, between 30.7 and 94.5microm in diameter and showed high porosity values (61-72%). The pore shapes of microsponges prepared by quasi-emulsion solvent diffusion method and entrapment method were found as spherical and cylindrical holes, respectively. Mechanically strong tablets prepared for colon specific drug delivery were obtained owing to the plastic deformation of sponge-like structure of microsponges. In vitro studies exhibited that compression coated colon specific tablet formulations started to release the drug at the 8th hour corresponding to the proximal colon arrival time due to the addition of enzyme, following a modified release pattern while the drug release from the colon specific formulations prepared by pore plugging the microsponges showed an increase at the 8th hour which was the time point that the enzyme addition made. This study presents a new approach based on microsponges for colon specific drug delivery.

Thymosin-loaded enteric microspheres for oral administration: Preparation and in vitro release studies

Thymosin, a water-soluble polypeptide compound, was encapsulated within enteric microspheres of acrylic acid resin II by modified oil in oil (o/o) emulsion solvent evaporation method. The mixture emulsifier composed of lecithin and Span 80 was critical to the formation of sphere-shaped thymosin microparticles. Optimizing process parameters, such as the volume ratio of organic solvent to water, initial drug feed and polymer concentration, resulted in high drug encapsulation efficiency of 89.7% (6% polymer concentration and 0.5% initial drug feed). In vitro release studies suggested that thymosin release from microspheres exhibited pH dependent profiles. For formulation with 6% polymer concentration and 0.5% initial drug feed, 68.7% thymosin was released within 4h in pH 6.8 PBS buffer, while only 6.5% was observed in acid medium.