Preparation and characterization of chitosan-treated alginate microparticles incorporating all-trans retinoic acid

Chitosan treated alginate microparticles were prepared with the purpose of incorporating all-trans retinoic acid (ATRA) using an inexpensive, simple and fast method, enhancing dermal localization and sustaining the release of ATRA into the skin. Microparticles characterization, drug-polymer interaction, release profile and in vitro skin retention were investigated. Microparticles presented spherical shape and drug loading capacity of 47%. The drug content of these microparticles was affected by ATRA concentration and by the solvent used and it was more weakly affected by chitosan concentration. The release of ATRA was also affected by chitosan concentration. Microparticles prepared with 0.4% chitosan (w/w) resulted in drug release with a more sustained profile. The results of in vitro retention studies showed that chitosan treated alginate microparticles decreased the drug retention in the stratum corneum (SC), where occur the skin irritation, but maintained the ATRA concentration in the deeper skin layers, where occur the pathologies treated with ATRA. Then, the microparticles developed in this work can be a good candidate to improve the topical therapy with retinoid.     

Preparation of naproxen–ethyl cellulose microparticles by spray-drying technique and their application to textile materials

Abstract

The objective of this study is to develop a new textile-based drug delivery system containing naproxen (NAP) microparticles and to evaluate the potential of the system as the carrier of NAP for topical delivery. Microparticles were prepared by spray-drying using an aqueous ethyl cellulose dispersion. The drug content and entrapment efficiency, particle size and distribution, particle morphology and in vitro drug release characteristics of microparticles were optimized for the application of microparticles onto the textile fabrics. Microparticles had spherical shape in the range of 10–15?μm and a narrow particle size distribution. NAP encapsulated in microparticles was in the amorphous or partially crystalline nature. Microparticles were tightly fixed onto the textile fabrics. In vitro drug release exhibited biphasic release profile with an initial burst followed by a very slow release. Skin permeation profiles were observed to follow near zero-order release kinetics.     

In Vitro Evaluation of Microparticles and Polymer Gels for Use as Nasal Platforms for Protein Delivery

Purpose. Nasal delivery of protein therapeutics can be compromised by the brief residence time at this mucosal surface. Some bioadhesive polymers have been suggested to extend residence time and improve protein uptake across the nasal mucosa. We examined several potential polymer platforms for their in vitro protein release, relative bioadhesive properties and induction of cytokine release from respiratory epithelium. Methods. Starch, alginate, chitosan or Carbopol^® microparticles, containing the test protein bovine serum albumin (BSA), were prepared by spray-drying and characterized by laser diffraction and scanning electron microscopy. An open-membrane system was used to determine protein release profiles and confluent, polarized Calu-3 cell sheets were used to evaluate relative bioadhesion, enhancement of protein transport and induction of cytokine release in vitro. Results. All spray-dried microparticles averaged 2–4 m in diameter. Loaded BSA was not covalently aggregated or degraded. Starch and alginate microparticles released protein more rapidly but were less adhesive to polarized Calu-3 cells than chitosan and Carbopol^® microparticles. Protein transport across polarized Calu-3 cells was enhanced from Carbopol^® gels and chitosan microparticles. A mixture of chitosan microparticles with lysophosphatidylcholine increased protein transport further. Microparticles prepared from either chitosan or starch microparticles, applied apically, induced the basolateral release of IL-6 and IL-8 from polarized Calu-3 cells. Release of other cytokines, such as IL-l, TNF-, GM-CSF and TGF-, were not affected by an apical exposure to polymer formulations. Conclusions. We have described two systems for the in vitro assessment of potential nasal platforms for protein delivery. Based upon these assessments, Carbopol^® gels and chitosan microparticles provided the most desirable characteristics for protein therapeutic and protein antigen delivery, respectively, of the formulations examined.     

Characterization of alginate/poly-L-lysine particles as antisense oligonucleotide carriers

The gel forming characteristics of alginate in the presence of calcium ions and further crosslinking with poly-L-lysine led to the formation of sponge-like nano- and microparticles. The particle size was varied by adjusting the final concentrations of and proportions between the components. The region for particle formation was from 0.04 to 0.08% (w/v) of alginate in the final formulation, the change from the nm to microm size range occurred at a concentration of approx. 0.055% (w/v). Oligonucleotide-loaded microparticles were prepared by two different methods, either by absorption of the drug into the crosslinked polymeric matrix or by incorporation of an oligonucleotide/poly-L-lysine complex into a calcium alginate pre-gel. The release of oligonucleotide from microparticles prepared by the first method was higher. The addition of increasing amounts of poly-L-lysine resulted in larger particles, higher oligonucleotide loading and slower drug release. An increase in the final solid content of the formulation led to larger particles, especially with high concentrated calcium alginate pre-gels. Microparticles based on alginate and poly-L-lysine are potential carriers for antisense oligonucleotides.     

Ex-vivo evaluation of alginate microparticles for Polymyxin B oral administration

A crosslinked alginate microparticle system for the targeting to the lymphatic system by Peyer's patches (PP) uptake was designed in order to improve the oral absorption of Polymyxin B (PMB). To verify mucoadhesion and PP uptake, microparticles labelled with fluorescein isothiocyanate (FITC) were prepared by spray-drying technique and crosslinking reactions with calcium ions and chitosan (CS), in vitro characterized and assayed by an ex vivo method. Microparticles showed a size less then 3 μm, an antibiotic loading level of 11.86 ± 0.70%, w/w, a sustained drug release behaviour in simulated gastro-intestinal (GI) fluids and a preserved biological activity throughout the manufacture. The ex vivo study was performed by a perfusion method on intestinal tracts of just sacrificed adult rats. The recovered samples were analysed by epifluorescence microscope for mucoadhesion and PP uptake and by microbiological analysis for antibiotic activity preservation, providing evidence of mucoadhesion at the level of both PP and non-PP epithelium, uptake by PP and PMB microbiological activity in PP tissue. Furthermore, the study revealed the involvement of transport pathways across villous enterocytes.     

Sustained release of antineoplastic drugs from chitosan-reinforced alginate microparticle drug delivery systems

Alginate based microparticle drug delivery systems were prepared for the sustained release of antineoplastic drugs. Two drugs, 5-fluorouracil (5-FU) and tegafur, were encapsulated into the microparticles. The drug loaded microparticles were fabricated using a very convenient method under very mild conditions, i.e., directly shredding the drug loaded beads into microparticles in a commercial food processor. The mean sizes of the obtained microparticles were between 100 and 200 μm. To effectively sustain the drug release, alginate microparticles were reinforced by chitosan during gelation. The drug release from the chitosan-reinforced alginate microparticles was obviously slower than that from the unreinforced microparticles. The effect of the reinforcement conditions on the drug release property of the microparticles was studied, and the optimized concentration of chitosan solution for reinforcement was identified. The effects of drug feeding concentration and pH value of the release medium on the drug release were investigated.     

An investigation of formulation factors affecting feasibility of alginate-chitosan microparticles for oral delivery of naproxen

In the present work we investigated the feasibility of chitosan treated Ca-alginate microparticles for delivery of naproxen in lower parts of GIT and evaluated influence of formulation factors on their physicochemical characteristics and drug release profiles. Investigated factors were drug/polymer ratio, chitosan molecular weight, chitosan concentration in hardening medium, and hardening time. Sixteen microparticle formulations were prepared utilizing 24 full factorial design (each factor was varied at two levels). Microparticles size varied between 262.3 ± 14.9 and 358.4 ± 21.7 μm with slightly deformed spherical shape. Low naproxen solubility and rapid reaction of ionotropic gelation resulted in high encapsulation efficiency (> 75.19%). Under conditions mimicking those in the stomach, after two hours, less than 6.18% of naproxen was released. Significant influence of all investigated factors on drug release rate was observed in simulated small intestinal fluid. Furthermore, experimental design analysis revealed that chitosan molecular weight and its concentration had the most pronounced effect on naproxen release. Release data kinetics indicated predominant influence of a pH-dependent relaxation mechanism on drug release from microparticles.     

Preparation,In Vitro Characterization,and In Vivo Pharmacokinetic Evaluation of Respirable Porous Microparticles Containing Rifampicin

This study aimed to prepare and evaluate rifampicin microparticles for the lung delivery of rifampicin as respirable powder. The microparticles were prepared using chitosan by the spray-drying method and evaluated for aerodynamic properties and pulmonary drug absorption. To control the drug release, tripoly-phosphate in different concentrations 0.6, 0.9, 1.2, and 1.5 was employed to get a sustained drug release profile. The microparticles were evaluated for drug loading, % entrapment efficiency, tapped density, morphological characteristics, and in vitro drug release studies. Aerosol properties were determined using the Andersen cascade impactor. Porous microparticles with particle sizes (d_0.5) less than 10 μm were obtained. The entrapment of rifampicin in microparticles was up to 72%. In vitro drug release suggested that the crosslinked microparticles showed sustained release for more than 12 hrs. The drug release rate was found to be decreased as the TPP concentration was increased. The microparticles showed a fine particle fraction in the range of 55–63% with mass median aerodynamic diameter (MMAD) values below 3 μm. The in vivo pulmonary absorption of the chitosan microparticles suggested a sustained drug release profile up to 72 hrs with an elimination rate of 0.010 per hr. The studies revealed that the spray-dried porous microparticles have suitable properties to be used as respirable powder in rifampicin delivery to the lungs.     

Alginate microparticles for Polymyxin B Peyer's patches uptake: microparticles for antibiotic oral administration

Microparticles with size less than 3?µm, able to be taken up by M cell of Peyer's patches for the drug delivery to the Gut Associated Limphoid Tissue (GALT), were developed in order to improve oral bioavailability of Polymyxin B (PMB). Less than 3?µm alginate microparticles resistant to gastro-intestinal media were prepared by spray-drying technique and cross-linking by calcium ions and chitosan. The cross-linked microparticles were evaluated for PMB content by spectrophotometric method, alginate/PMB interaction by rheological study, cross-linking degree by EDS analysis and PMB activity by microbiological assay. By modulating the polymer cross-linking degree, cationic PMB interacted on alginate chains leading to a proper PMB loading as well as antibiotic retention in gastric environment and sustained delivery in intestinal fluid. Moreover, the procedure resulted suitable for PMB biological activity preservation.     

Alginate microparticles for Polymyxin B Peyer's patches uptake: microparticles for antibiotic oral administration

Microparticles with size less than 3 microm, able to be taken up by M cell of Peyer's patches for the drug delivery to the Gut Associated Limphoid Tissue (GALT), were developed in order to improve oral bioavailability of Polymyxin B (PMB). Less than 3 microm alginate microparticles resistant to gastro-intestinal media were prepared by spray-drying technique and cross-linking by calcium ions and chitosan. The cross-linked microparticles were evaluated for PMB content by spectrophotometric method, alginate/PMB interaction by rheological study, cross-linking degree by EDS analysis and PMB activity by microbiological assay. By modulating the polymer cross-linking degree, cationic PMB interacted on alginate chains leading to a proper PMB loading as well as antibiotic retention in gastric environment and sustained delivery in intestinal fluid. Moreover, the procedure resulted suitable for PMB biological activity preservation.     

Design of a pectin-based microparticle formulation using zinc ions as the cross-linking agent and glutaraldehyde as the hardening agent for colonic-specific delivery of resveratrol: In vitro and in vivo evaluations

The aim of this study was to develop a colon-specific microparticle formulation based on pectin. Resveratrol was used as a model drug due to its potential therapeutic efficacy on colitis and colon cancer. Microparticles were produced by cross-linking pectin molecules with zinc ions and with glutaraldehyde as hardening agent for pectins. Different microparticles were prepared by varying the formulation variables. Effect of these formulation variables were investigated on particle shape and size, moisture content and weight-loss during drying, encapsulation efficiency, swelling–erosion ratio, and drug release pattern of the formulated microparticles. Formulation conditions were optimized based on the in vitro drug release study. Morphology, Fourier transform infrared spectroscopy, stability, and in vivo pharmacokinetic study of the microparticles prepared at the optimized formulation conditions were performed. Microparticles were spherical with <1?mm diameter and encapsulation efficiencies of >94%. The glutaraldehyde-modified microparticles prepared at optimized formulation conditions revealed colon specific in vitro and in vivo drug release. Plasma appearance of drug was delayed for 4–5?h after their administration directly into stomach, but displayed comparable area under the curve to other controls in the experiment, indicating the potential of the developed formulation as a colon-specific drug delivery system.     

Assessment of formulated amodiaquine microparticles in Leishmania donovani infected rats

The aim of this study was to formulate, characterise and evaluate the activity of amodiaquine microparticles against Leishmania donovani. Microparticles were formulated by encapsulating the drug in bovine serum albumin using the spray-dryer method. The microparticles were evaluated for size, zeta potential, drug content, encapsulation efficiency and in vitro release profile. The size range of the microparticles formulated was between 1.9 and 10?μm with an average zeta potential of ?25.5?mV. Of the expected 20% drug loading, an average of 18.27% was obtained giving an encapsulation efficiency of 91.35%. Pharmacokinetic profile of amodiaquine improved with microencapsulation of the drug with C_max, AUC_0→48 and t_1//2 all significantly higher than amodiaquine solution. Amodiaquine microparticles showed an overall higher bioavailability and hence were more effective in eliminating intra-tissue parasites than the drug solution. It would therefore be expected that the formulated microparticles will be more effective in treating visceral leishmaniasis.     

Preparation and evaluation of microparticles from thiolated polymers via air jet milling

Microparticles were formulated by incorporation of the model protein horseradish peroxidase in (thiolated) chitosan and (thiolated) poly(acrylic acid) via co-precipitation. Dried protein/polymer complexes were ground with an air jet mill and resulting particles were evaluated regarding size distribution, shape, zeta potential, drug load, protein activity, release pattern, swelling behaviour and cytotoxicity. The mean particle size distribution was 0.5-12 microm. Non-porous microparticles with a smooth surface were prepared. Microparticles from (thiolated) chitosan had a positive charge whereas microparticles from (thiolated) poly(acrylic acid) were negatively charged. The maximum protein load for microparticles based on chitosan, chitosan-glutathione (Ch-GSH), poly(acrylic acid) (PAA) and for poly(acrylic acid)-glutathione (PAA-GSH) was 7+/-1%, 11+/-2%, 4+/-0.2% and 7+/-2%, respectively. The release profile of all microparticles followed a first order release kinetic. Chitosan (0.5mg), Ch-GSH, PAA and PAA-GSH particles showed a 31.4-, 13.8-, 54.2- and a 42.2-fold increase in weight, respectively. No significant cytotoxicity could be found. Thiolated microparticles prepared by jet milling technique were shown to be stable and to have controlled drug release characteristics. After further optimizations the preparation method described here might be a useful tool for the production of protein loaded drug delivery systems.     

Methacrylate micro/nano particles prepared by spray drying: a preliminary in vitro/in vivo study

Delivery systems controlling drug release only in the colon holds great promises since they improve utilization of drug and decrease the dosing times comparison with conventional forms. The aim of the present study was to prepare polymeric microparticles on the basis of Ciprofloxacin via oral route for the treatment of inflammatory bowel disease. Ciprofloxacin was selected because of its extensive coverage for intestinal flora, relatively favorable side-effect profile and preliminary data suggesting its efficacy in the treatment of active Crohn's Disease. Microparticles were prepared using different acrylic compounds, namely Eudragit® RL (PO) and RS (PO) and a mixture of both. Spray-drying was used as a preparation method of Ciprofloxacin/Eudragit® microparticles using a Mini Spray Dryer B-290 (Büchi, Postfach, Switzerland). In vitro dissolution studies were performed to choose the best formulation and selected microparticles were characterized by size and morphology by environmental scanning electron microscopy. Yield and encapsulation efficiency were calculated and in vivo/ex vivo experiments were investigated both of which suggest that selected microparticles can be used for colon targeting of drugs increasing residence time of the drug in the affected area.     

Mucoadhesive microspheres for nasal administration of an antiemetic drug, metoclopramide: in-vitro/ex-vivo studies

Microparticulate delivery systems designed for the nasal administration of an antiemetic drug, metoclopramide hydrochloride, were prepared. Microspheres composed of sodium alginate, chitosan hydrochloride, or both, were obtained using a spray-drying method; some batches of drug-free microparticles were prepared as a comparison. The morphology, in-vitro swelling behaviour, mucoadhesive properties and drug release from microparticles were evaluated. Ex-vivo drug permeation tests were carried out using sheep nasal mucosa; permeation test of the drug solution was performed as comparison. During ex-vivo permeation tests, transmission electron microscopy (TEM) analyses were carried out on the nasal mucosa to study the morphological changes of epithelial cells and tight junctions, while the change in microsphere morphology was examined using photostereo microscopy (PM). Spray-dried microparticles had a mean diameter (d(vs)) in the range of about 3-10 microm. They showed good in-vitro mucoadhesive properties. In-vitro release profiles and swelling behaviour depended on their composition: the drug release occurred in 1-3 h. Ex-vivo studies showed that drug permeation through the mucosa from microparticles based on chitosan was higher than from those consisting of alginate alone. This can be related to the penetration enhancing properties of chitosan. Complexation of chitosan with alginate led to a control of the drug release. Microscopy observation of microspheres during the permeation tests revealed that microparticles swelled and gelled, maintaining their shape. TEM analyses of the mucosa after exposure to the microparticles consisting of alginate/chitosan showed opened tight junctions. This preliminary study shows that alginate/chitosan spray-dried microspheres have promising properties for use as mucoadhesive nasal carriers of an antiemetic drug.     

Formulation and optimization of alkaline extracted ispaghula husk microparticles of isoniazid – in vitro and in vivo assessment

Microparticles containing isoniazid were prepared by the emulsification internal ionic gelation method using a novel, alkaline extracted ispaghula husk as a wall forming material. A four-factor three-level Box–Behnken design was employed to study the effect of independent variables on dependent variables. Sodium alginate concentration (X₁), alkaline extraction of ispaghula husk (AEISP) concentration (X₂), concentration of cross-linking agents (X₃) and stirring speed (X₄) were four independent variables considered in the preparation of microparticles, while the particle size (Y₁) and entrapment efficiency (Y₂) were dependent variables. Optimized microparticles exhibited 83.43% drug entrapment and 51.53?µm particle size with 97.80% and 96.37% validity, respectively, at the following conditions – sodium alginate (3.55% w/v), alkaline extracted ispaghula husk (3.60% w/v), cross-linker concentration (7.82% w/v) and stirring speed (1200?rpm). The optimized formulation showed controlled drug release for more than 12?h by following Higuchi kinetics via non-Fickian diffusion. The gamma scintigraphy of the optimized formulation in Wistar rats showed that microparticles could be observed in the intestinal lumen after 1?h and were detectable in the intestine up to 12?h, with decreased percentage of radioactivity (t_1/2 of ^99mTc 4–5?h).     

Alginate/Poly-L-Lysine Microparticles for the Intestinal Delivery of Antisense Oligonucleotides

Purpose. A microparticle carrier based on alginate and poly-L-lysine was developed and evaluated for the delivery of antisense oligonucleotides at the intestinal site. Formulations of oligonucleotide-loaded microparticles having differences in the carrier molecular weight and composition were characterized in vitro and in vivo. Methods. Polymeric microparticles were prepared by ionotropic gelation and crosslinking of alginate with calcium ions and poly-L-lysine. The loading of the antisense oligonucleotide into the microparticles was achieved by absorption in aqueous medium. The association capacity, loading and particle size of the microparticles were characterized. The in vivo performances of various formulations after intrajejunal administration were studied in rat and in dog models. Results. Microparticles had a sponge-like structure and an oligonucleotide loading of 27-35%. The composition of the medium affected the particle size and the in vitro release profiles. The oligonucleotide bioavailability after intrajejunal administration to rats in the presence of permeation enhancers was good for most of the tested systems. The application of microparticles in powder form compared to an equivalent suspension improved the intrajejunal bioavailability of the oligonucleotide (25% and 10% respectively) in rats. On the contrary, the intrajejunal administration to dogs resulted in poor oligonucleotide bioavailability (0.42%). Conclusions. The formulation of antisense oligonucleotides within alginate and poly-L-lysine microparticles is a promising strategy for the oral application.     

Chitosan microparticle preparation for controlled drug release by response surface methodology

The objectives were to investigate the effects of formulation variables on the release of drug and to optimize the formulation of chitosan microparticles loaded with drug for controlled release using response surface methodology. Chitosan microparticles were prepared by dropping a chitosan solution into sodium tripolyphosphate (TPP) through ionic cross-linking. The release behaviour of felodipine as a model drug was affected by preparation variables. A central composite design was used to evaluate and optimize the effect of preparation variables, chitosan concentration (X₁), the pH of the TPP solution (X₂) and cross-linking time (X₃) on the cumulative per cent drug release (Y) in 24 h. Chitosan concentration and cross-linking time affected negatively the release of felodipine, while the pH of the TPP did so positively and was the highest influential factor. The optimum rate of drug release, 100% in 24 h, was achieved at 1.8% chitosan concentration, a pH 8.7 for the TPP solution and 9.7 min cross-linking time.     

Novel microparticle drug delivery systems based on chitosan and Eudragit®RSPM to enhance diltiazem hydrochloride release property

The aim of this study was to enhance the release properties of diltiazem hydrochloride (diltiazem HCl) by using microparticle system. For this reason, microparticle drug delivery systems based on chitosan and Eudragit^®RSPM were developed. The microparticles were prepared by using double-emulsion solvent extraction method and the mean sizes of microparticles were less than 120?µm. The in vitro drug release from microparticles was studied in simulated gastric (pH 1.2) and intestinal media (pH 7.4) than the results were evaluated by kinetically. In vitro diltiazem HCl release from microparticles showed good zero order kinetic. For the microparticles with chitosan, the release of diltiazem HCl at pH 1.2 could be effectively sustained, while the release of diltiazem HCl increased at pH 7.4 when compared to Eudragit^®RSPM microparticles. The highest release percent obtained was 1:1 ratio of drug: polymer at pH 1.2 and 7.4. All results clearly suggest that the release properties of diltiazem HCl were improved by using microparticle systems especially which contain chitosan.     

Chitosan microparticles for oral bioavailability improvement of the hydrophobic drug curcumin

The aim of this study was to assess the feasibility of microparticles for dissolution enhancement and oral bioavailability of curcumin (Cur). Microparticles were prepared by the ionic crosslinking interaction with the use of tripolyphosphate (TPP) and chitosan (Cs). The physicochemical characteristics of microparticles were investigated. The in vivo performance was assessed by a pharmacokinetic study. The microparticles had an average diameter of 58.50 microm. Acceptable drug loading and encapsulation efficiency of microparticles were obtained to be 33.5% and 85.2%, respectively. Dissolution of Cur enhanced in the microparticles in comparison with pure drug. Drug release profile of Cur from microparticles fitted the first-order model. Microparticles provided improved pharmacokinetic parameters (Cmax 270.24 ng/ml, T(max) 1.30 h) in rats as compared with pure drug (C(max) 87.06 nglml, Tmax 0.66 h). The AUC value of microparticles was 8.4 fold that of the pure drug. The information from this study suggests that the developed microparticles successfully enhanced dissolution of the poorly water-soluble drug Cur, and eventually, improved its oral bioavailability effectively.