Polyelectrolyte Microparticles Research Articles

Preparation and evaluation in vitro release of sodium alginate/chitosan polyelectrolyte microparticles containing rifampicin and theoretical study using DFT methods

In this work, rifampicin-loaded sodium alginate/chitosan polyelectrolyte microparticles were prepared by the ionotropic gelation technique using CaCl2 as a cross-linking agent. The influence of different sodium alginate and chitosan concentrations on particle size, surface properties, and in vitro release behavior was studied. An infrared spectroscopy investigation verified the lack of any drug–polymer interaction. The microparticles prepared using (30, 50) mg of sodium alginate were spherical while when using 75 mg of sodium alginate, vesicles with round heads and tapered tails were formed. The results showed that the microparticle diameters were between (11.872–35.3645) µm. The amount of rifampicin released and the kinetics of drug release from microparticles were studied, and the results showed that by increasing the concentration of the polymer, the release of the rifampicin from the microparticles decreased. The findings showed that rifampicin release followed zero-order kinetics and that drug release from these particles is frequently influenced by diffusion. The electronic structure and characteristics of the conjugated polymers (sodium alginate/Chitosan) were examined using density functional theory (DFT) and PM3 calculations with Gaussian 9, using the B3LYP, and electronic structure calculations using 6–311 G (d,p). The HOMO and LUMO energy levels are determined as the HOMO's maximum and the LUMO's minimum, respectively. Communicated by Ramaswamy H. Sarma

Drug transport mechanisms and in vitro release kinetics of vancomycin encapsulated chitosan-alginate polyelectrolyte microparticles as a controlled drug delivery system

In this study, chitosan-alginate polyelectrolyte microparticles containing the antibiotic, vancomycin chloride were prepared using the ionotropic gelation (coacervation) technique. In vitro release and drug transport mechanisms were studied concerning the chitosan only and alginate only microparticles as a control group. Further, the effect of porosity on the drug transport mechanism was also studied for chitosan-alginate mixed particles produced by lyophilizing in contrast to the air-dried non-porous particles. According to the in vitro release data, alginate only and chitosan only microparticles showed burst release and prolonged release respectively. Chitosan-alginate lyophilized microparticles showed the best-controlled release of vancomycin with the average release of 22μg per day for 14days. Also, when increasing alginate concentration there was no increase in the release rate of vancomycin. The release data of all the microparticles were treated with Ritger-Peppas, Higuchi, Peppas-Sahlin, zero-order, and first-order kinetic models. The best fit was observed with Peppas-Sahlin model, indicating the drug transport mechanism was controlled by both Fickian diffusion and case II relaxations. Also, Fickian diffusion dominates the drug transport mechanism of all air-dried samples during the study period. However, the Fickian contribution was gradually reducing with time. Porosity significantly effects the drug transport mechanism as case II relaxation dominates after day 10 of the lyophilized microparticles.

Polyelectrolyte microparticles for enhancing anode performance in an air–cathode μ-Liter microbial fuel cell

Microbial fuel cell (MFC) is considered an environmentally friendly energy source because it generates electrical power by digesting organic substrates in the wastewater. However, it is still challenging for MFC to become an economically affordable and highly efficient energy source due to its relatively low power output and coulombic efficiency. The aim of this study is to increase the performance of anode by using polyelectrolyte microparticles to facilitate the accumulation of microorganisms and the collection of electrons. The polyelectrolyte microparticle is subjected to microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and continuous electricity generation in an air–cathode μ-Liter MFC (μMFC) to validate its biocompatibility, ability in retaining redox species, reduced electron transfer resistance, and sustained energy generation. During the 168-hour operation, microorganisms proliferate inside the microparticle and generate around 250% power output and 200% limiting current of those from microorganism biofilm. The polyelectrolyte microparticle also decreased charge-transfer resistance of anode electrode in air–cathode μMFC by 56% compared with biofilm.

Nanoporous polyelectrolyte vaccine microcarriers. A formulation platform for enhancing humoral and cellular immune responses

In this paper we report on the design, characterization and immuno-biological evaluation of nanoporous polyelectrolyte microparticles as vaccine carrier. Relative to soluble antigen, formulation of antigen as a sub-10μm particle can strongly enhance antigen-specific cellular immune responses. The latter is crucial to confer protective immunity against intracellular pathogens and for anti-cancer vaccines. However, a major bottleneck in microparticulate vaccine formulation is the development of generic strategies that afford antigen encapsulation under benign and scalable conditions. Our strategy is based on spray drying of a dilute aqueous solution of antigen, oppositely charged polyelectrolytes and mannitol as a pore-forming component. The obtained solid microparticles can be redispersed in aqueous medium, leading to leaching out of the mannitol, thereby creating a highly porous internal structure. This porous structure enhances enzymatic processing of encapsulated proteins. After optimizing the conditions to process these microparticles we demonstrate that they strongly enhance cross-presentation in vitro by dendritic cells to CD8 T cells. In vivo experiments in mice confirm that this vaccine formulation technology is capable of enhancing cellular immune responses.

Spray-Dried Polyelectrolyte Microparticles in Oral Antigen Delivery: Stability, Biocompatibility, and Cellular Uptake

During the past decade, extensive research has undeniably improved the formulation and delivery of oral vaccines. Nevertheless, several factors, such as the harsh gastrointestinal environment together with tolerance induction to exogenous antigens, have thus far impeded the optimal effectiveness and clinical application of oral delivery systems. The current study encompasses an initial evaluation of the stability, biocompatibility, and cellular uptake of two promising candidate systems for oral antigen delivery, that is, calcium carbonate- (CP) and mannitol-templated (MP) porous microspheres. Both spray-dried formulations were efficiently internalized by human intestinal epithelial cells (Caco-2 and HT-29) and degraded into phagolysosomal intracellular compartments. In addition, cellular particle uptake and processing significantly up-regulated the expression of (HLA) class-II and costimulatory molecules on intestinal epithelial cells. Even though the high surface-area-to-volume ratio of the microspheres was expected to favor protease access, antigen release was remarkably limited in simulated intestinal fluid and was even absent under gastric conditions. Finally, neither CP nor MP exerted cytotoxicity upon prolonged in vitro incubation with high antigen concentration. Altogether, these data support the potential of CP and MP for oral antigen delivery and motivate the further development of these promising carrier systems in in vivo studies.

Polyelectrolyte complexes of lactoferrin and pH-sensitive microparticles on their basis

Suspensions of insoluble polyelectrolyte complexes of dextran sulfate? (DS) of different molecular masses with lactoferrin (LF) have been fabricated and characterized. The encapsulation efficiency of LF and DS in a complex at pH 3.0 and 4.0 was assessed, and particles were characterized by their sizes and zeta-potential. The complexes formed at pH 3.0 differed by a higher stability level. The interaction with DS resulted in a twofold decrease in the antioxidant activity of LF, although the formation of complexes was not accompanied by conformational changes in LF molecules according to IR-spectrometry data. Microencapsulation was carried out by treating the suspensions with negatively charged LF-DS complexes with protamine and chitosane solutions with different molecular masses. The composition, size, and the zeta-potential of interaction products were assessed which allowed us to select the conditions for the preparation of pH-sensitive polyelectrolyte microparticles loaded with LF which would be able to gradually release glycoprotein under conditions that model the passage through the gastrointestinal tract of humans. These data indicate that this approach is promising for the creation of pH-sensitive biopolyelectrolytes suitable for oral administration of LF to target cells.

Wheat germ agglutinin-functionalised crosslinked polyelectrolyte microparticles for local colon delivery of 5-FU: in vitro efficacy and in vivo gastrointestinal distribution

We have previously reported the development and characterisation of wheat germ agglutinin (WGA)-functionalised chitosan-Ca-alginate (CTS-Ca-ALG) microparticles (MPs) loaded with acid-resistant particles of 5-fluorouracil (5-FU). In the present work, our goal was to evaluate the potential of these carriers for efficient treatment of colon cancer by studying in vitro permeability and cell association of 5-FU and [methyl-3H]thymidine uptake in Caco-2 cells, as well as in vivo gastrointestinal distribution. The amount of 5-FU permeated through Caco-2 cells was 15.1, 7.7 and 6.5% for 5-FU solution, CTS-Ca-ALG MPs and WGA conjugates. The concentration of 5-FU associated with Caco-2 cells was significantly greater when delivered from MPs. By incorporation of 5-FU into MPs and further decoration with WGA, an increased [methyl-3H]thymidine uptake was observed few hours after continuous drug treatment followed by significantly reduced uptake after 6 h. Gastrointestinal distribution was in favour of increased localisation and concentration of the particles in colon region.

Use of Protease Inhibitors in Composite Polyelectrolyte Microparticles in Order to Increase the Bioavailability of Perorally Administered Encapsulated Proteins

Protein protease inhibitors (aprotinin, soybean Bowman–Birk inhibitor, and Kunitz soybean trypsin inhibitor) possessing different specificity with respect to trypsin, chymotrypsin, and elastase were encapsulated together with a cargo protein in polyelectrolyte microparticles using layer-by-layer (LbL) deposition techniques. The most efficient inclusion of the inhibitors occurred at the formation stage of the insoluble protein complex with the polyanion. Simultaneous immobilization of the inhibitor and protein did not influence the physicochemical properties of the microparticles, specifically their pH-sensitive behavior under conditions modeling the passage through various parts of the human gastrointestinal tract after peroral administration. The most effective protection against the action of proteolytic enzymes of pancreatic juice and the small intestine was achieved for simultaneous release of cargo protein and inhibitor from the microparticles. Soybean Bowman–Birk inhibitor, which is most similar to insulin with respect to physicochemical properties, in addition to the soybean extract enriched with protease inhibitors were the most suitable agents for protection of human insulin or its rapidly acting analogs (lispro and aspart). These findings suggested that simultaneous microencapsulation of both protein and protein protease inhibitor was a promising way to increase the protein bioavailability upon peroral administration of polyelectrolyte microparticles.

Biopharmaceutical evaluation of diclofenac sodium controlled release tablets prepared from gum karaya − chitosan polyelectrolyte complexes

The phenomena of polymer interactions and formation of polyelectrolyte complexes (PECs) of oppositely charged polymers have been the focus of interest in fundamental and applied research. Such PECs may possess unique properties that are different from those of individual polymers. In the present study, attempts were made to prepare PECs of negative colloid gum karaya (GK) and positively charged polysaccharide chitosan (CH). The association and factors affecting the interactions between GK and CH were studied by pH and conductivity studies. The dried complexes were characterized by X-ray diffraction, Fourier transformed Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy. The PECs were utilized for encapsulation of diclofenac sodium. Selected polyelectrolyte microparticles were compressed into tablets and were compared with commercial sustained release product Voveran SR®. Positive results of the study indicated the applicability of PECs in the design of oral controlled release drug delivery systems.

Fabrication of Multilayered Microparticles by Integrating Layer‐by‐Layer Assembly and MicroContact Printing

Polyelectrolyte microparticles, widely used for biomedical applications, are produced via a simple and inexpensive approach by integrating microcontact printing and layer-by-layer assembly techniques. This new approach is not only able to produce microparticles with well-defined sizes and shapes, but is also highly versatile in creating particles with various complex structures and a patterned particle array.

Mucoadhesive polyelectrolyte microparticles containing recombinant human insulin and its analogs aspart and lispro

Microparticles containing recombinant human insulin and its analogs aspart and lispro were prepared using an alternate adsorption of chitosan and dextran sulfate from solutions onto microaggregates of protein-dextran sulfate insoluble complex. The following properties of polyelectrolyte hormone-containing microparticles were studied: pH stability, surface charge, mucoadhesive properties, Ca(2+) binding, degradation under the influence of proteases (trypsin, chymotrypsin). The influence of the self-association ability of encapsulated insulins on the form of protein releasing from microparticles was studied. Insulins aspart and lispro released from the microparticles as monomers were more liable to proteolysis than human insulin released as a hexamer. The combined effect of properties of polyelectrolyte microparticles and of encapsulated recombinant proteins on the bioavailability of insulin under peroral administration is discussed.

Fabrication and properties of pH-sensitive nanostructured polyelectrolyte microparticles loaded with insulin

Thorough investigation and comparative study were conducted for insulin-loaded microparticles fabricated by consecutive adsorption of polyanions (dextran sulfate and chitosan sulfate) and polycations (chitosan and protamine) onto protein microaggregates. The possible regulation of insulin release from the particles by variation in polyelectrolyte pairs, in the number of their adsorption cycles and in pH of media was demonstrated. For all studied cases the microparticles showed protective action towards insulin inactivation at acid pH values and protein release at pH > 5, corresponding to human gastro-intestinal conditions.

Fabrication and Physical-Chemical Characterisation of Polyelectrolyte Microparticles: Platform for Controlled Release of Bioactives

Porous CaCO(3) microparticles were fabricated by colloidal crystallization. Two oppositely charged polyelectrolytes, poly (styrene sulfonate, PSS) and poly (allylamine hydrochloride, PAH) were adsorbed layer-by-layer on the CaCO(3) templates. Polyelectrolyte microcapsules were then obtained by removing the CaCO(3) core. Scanning electron microscopy (SEM), energy-dispersion X-ray analysis (EDX), laser diffraction particle sizing and Raman spectroscopy were employed to characterize the physico-chemical properties of the constructed microcapsules. In vitro drug release studies were conducted using the model water-soluble drug Rhodamine B. Factors such as the number of polyelectrolyte layers and pH were investigated. SEM micrographs revealed uniform CaCO(3) microparticles, nearly spherical in shape with pronounced surface roughness, and highly developed interior porous structure. The surface of polyelectrolyte coated particles became rougher than the initial CaCO(3) microparticles. The acquired SEM micrographs of the (PSS/PAH)(n) microcapsules indicated that the number of layers affected the morphology of the microcapsules. The (PSS/PAH)(3) microcapsules revealed a very porous network with many holes resembling the initial morphology of CaCO(3) microparticles. Raman spectra showed peaks at 1125 cm(-1) (S=O bond) and 1600 cm(-1) (aromatic ring stretching) which represented the PSS molecule. The thickness of each layer was about 10 to 20 nm and it can be tailored to such nanometer level by controlling the number of adsorbed layers. The in vitro release of Rhodamine B was dependent on both the number of wall bilayers as well as the pH of the release media. These systems provide an opportunity for the development of controlled release dosage forms with greater effectiveness in the treatment of chronic conditions.

Polyelectrolyte assembling for protein microencapsulation

We have developed a novel microencapsulation technique based on covering micronized protein-containing aggregates with a polyelectrolyte multilayer. Here we describe the procedure of the incorporation of pancreatic proteases or ovalbumin into microparticles by layer-by-layer adsorption of oppositely charged polyelectrolytes (dextran sulfate, chitosan) on a proteinaceous core and give an account of the impact of the microencapsulation protocol on the protein release parameters. Insoluble protein-polyanion microaggregates were used as templates. Microparticles varying in the number of cycles of polyelectrolyte adsorption on protein-polyanion aggregates were examined and compared. Polyelectrolyte microparticles were shown to retain the shape and dimensions of the initial template. The microparticles were stable at pH below 5; at pH close to the pH of small intestine a protein release started. The higher the number of polyelectrolyte adsorption cycles was, the lower was the protein release rate. The microparticles obtained seem to be a promising vehicle for oral protein delivery.

Fabrication and characterization of polyelectrolyte microparticles with protein.

The incorporation of proteins into microparticles fabricated by layer-by-layer adsorption of oppositely charged polyelectrolytes (dextran sulfate and protamine) on protein microaggregates was studied. Microaggregates with insulin were prepared by two different techniques: 1) formation of insoluble polyelectrolyte complex consisting of insulin and dextran sulfate (aggregate size of 7-20 micro m), or 2) salting out of insulin from solution by sodium chloride (aggregate size of 5-13 micro m). Microparticles varying in the number of cycles (from 1 to 8) of polyelectrolyte adsorption on protein aggregates were examined and compared. Morphology of the microparticles was studied by scanning electron and optical microscopy. It was shown that polyelectrolyte microparticles retained the shape and dimensions of the initial protein aggregates used as a template. Ultrasonication of microparticles obtained using salted out protein aggregates resulted in the formation of stable nanoparticles (100-200 nm). Regulation of protein release from the microparticles of both types by varying the number of polyelectrolyte adsorption cycles and pH of the medium was demonstrated. Insulin not bound to polyelectrolytes was released from the microparticles at pH values between 6 and 8, which corresponds to the pH of the human small intestine and ileum.

Inclusion of proteins into polyelectrolyte microparticles by alternative adsorption of polyelectrolytes on protein aggregates.

A new method of protein immobilization into polyelectrolyte microparticles by alternative adsorption of the oppositely charged polyelectrolytes on the aggregates obtained by salting out of protein is proposed. The model protein alpha-chymotrypsin (ChT) was included in the polyelectrolyte microparticles obtained by various number of polyelectrolyte adsorption steps (from 1 to 11). The main parameters of ChT inclusion into microparticles were calculated. Scanning electron and optical microscopy were used for characterization of morphology and determination of particle size which was from 1 to 10 micro m in most cases. It was shown that the size and shape of protein-containing particles and protein aggregates used as a matrix were similar. Change in ChT enzymatic activity during entrapment into polyelectrolyte particles and activity of released protein were studied. The effect of pH on release of incorporated proteins was investigated; it was shown that change in pH and the number of polyelectrolyte adsorption steps allows protein release to be manipulated.