Alginate-Coated Alginate-Polyethyleneimine Beads for Prolonged Release of Furosemide in Simulated Intestinal Fluid

Furosemide-loaded calcium alginate (ALG), calcium alginate-polyethyleneimine (ALG-PEI) and alginate-coated ALG-PEI (ALG-PEI-ALG) beads were prepared by ionotropic/polyelectrolyte complexation method to achieve controlled release of the drug. Effects of several formulation factors on the characteristics of the beads were investigated. Although variation in formulation factors did not influence the drug-loading efficiency (DLE) of ALG beads, rapid release of the drug in simulated intestinal fluid (SIF) could not be prevented. PEI treatment of ALG beads, however, prolonged the drug release considerably. Ionic interaction, as appeared from FTIR studies, between alginate and PEI led to the formation of polyelectrolyte complex membrane, the thickness of which was dependent on the conditions of PEI treatment as demonstrated by scanning electron microscopy (SEM). The membrane acted as a physical barrier to drug release from ALG-PEI beads. Alginate coating of ALG-PEI beads further prolonged the release of the drug by increasing membrane thickness and reducing swelling of the beads possibly by blocking the surface pores. Differential scanning calorimetry (DSC) study indicated that drug was not degraded by PEI treatment. The release data from ALG-PEI beads showed a good fit in power law expression, whereas the release data from ALG-PEI-ALG beads were found to fit in modified power law expression, and the mechanism of drug release changed from super case II transport to nearly Fickian transport, depending on the degree of gelation and formation of polyelectrolyte complex membrane.     

Gelcasting of alumina-chitosan beads

Several papers have reported the advantageous combination of chitosan and ceramic particles for such applications as biomimetic scaffolds, membranes, pollution remediation and gelcasting complex shapes. This work presents a novel gelcasting consolidation mechanism, based on the effects of pH changes on chitosan solubility and zeta potential of alumina particles. Unlike other chitosan-based gelcasting methods, it employs a small content of organic material (lower than 3 wt%) and does not require crosslinking agents (such as glutaraldehyde). With this new method alumina beads with 0.5-1 mm diameter could be produced, whose porosity and specific surface area could be tuned for various applications.     

Studies on in vitro release of CPM from semi-interpenetrating polymer network (IPN) composed of chitosan and glutamic acid

Interpenetrating polymer network (IPN) beads consisting of chitosan-glutamic acid were prepared for in vitro study of controlled release of chlorpheniramine maleate (CPM). A viscous solution of chitosan-glutamic acid was prepared in 2% acetic acid solution, extruded as droplets through a syringe to alkalimethanol solution and the precipitated beads were crosslinked using glutaraldehyde solution. Swelling and drug release studies were carried out. Transport of release medium through the semi-IPN depended upon its pH and extent of crosslinking. The structural and morphological studies of beads were carried out by using a scanning electron microscope (SEM). The larger surface area of beads as well as their ease of handling makes them ideal agents of controlled release.     

Automated single nucleotide polymorphism typing using bead array in capillary tube

A low-cost and simple on-site technique for genotyping single nucleotide polymorphisms (SNPs) was developed. The technique is based on allele-specific primer PCR and the recently developed bead arrays in a single tip technique. The performance of the method was verified by genotyping four SNPs that correlate with cardiovascular diseases.     

Automated Microscale His‐tagged Protein Purification Using Ni‐NTA Magnetic Agarose Beads

To achieve standardized and parallelized microscale protein purification, an automated purification system was developed and optimized using a pipetting robot for purifying large sets of proteins with Ni‐NTA magnetic agarose beads. Recombinant hexahistidine‐tagged proteins β‐glucanase (Bgl‐His) and esterase I of Pseudomonas fluorescens (PFE I) were tested on the system. High purity along with high coherence was achieved. The purification procedure can be applied to 96 samples simultaneously and only takes about 1/3 of the time required for purification conducted by hand. Due to the stability of the robot system, the consistency of the results is much better than the results achieved through manual purification. This rapid and reliable method is reproducible and applicable to high throughput screening of huge amounts of samples.     

Alginate drug delivery systems: application in context of pharmaceutical and biomedical research

Alginates are natural polymers widely used in the food industry because of their biocompatible, biodegradable character, nontoxicity and easy availability. The bioadhesive character of alginates makes them useful in the pharmaceutical industry as well. The application areas of sodium alginate-based drug delivery systems are many and these systems can be formulated as gels, matrices, membranes, nanospheres, microspheres, etc. Worldwide researchers are exploring possible applications of alginates as coating material, preparation of controlled-release drug delivery systems such as microspheres, beads, pellets, gels, fibers, membranes, etc. In the present review, such applications of alginates are discussed.     

Mechanisms of lead biosorption on cellulose/chitin beads

Environment-friendly cellulose/chitin beads being prepared by coagulating a blend of cellulose and chitin in 6 wt% NaOH/5 wt% thiourea aqueous solution with 5% H2SO4 possessed higher heavy metals uptake capacity than pure chitin flakes. The mechanisms of Pb2+ adsorption on cellulose/chitin beads at pH0=5 were investigated at the molecular levels by scanning electron micrographs (SEM), transmission electron micrographs (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). The result revealed that mechanisms for the adsorption of Pb2+ on the cellulose/chitin beads could be described as complexation between Pb2+ and N atom in the chitin, and further adsorption of Pb2+ nearby the complexed Pb2+ and precipitation of the hydrolysis product of the Pb2+ complex on the beads as the crystalline state. Furthermore, structural factors such as larger surface area of the beads resulted from microporous-network structure, low crystallinity of cellulose/chitin beads and high hydrophilicity induced by hydrophilic skeleton of cellulose played an important role in increasing adsorption ability.     

Effect of air flowrate on particle velocity profile in a circulating fluidized bed

The research was conducted in a cold flow circulating fluidized bed (CFB). The diameter and height of riser are 5 and 200 cm, respectively. The objective is to study effect of gas velocity on hydrodynamic of glass beads having mean diameter of 547 micron and density of 2,400 kg/m³. The measurement of particle velocity profile was achieved by using a high-speed camera and an image processing software. A probe of 0.5 cm in diameter was inserted into the riser at the height of 110 cm from gas distributor and was set at 3 positions along the radius of the riser; 0, 0.6, and 1.8 cm from center. Transport velocity (U _tr ), core-annulus velocity (V _CA ) and minimum pneumatic velocity (V _mp ) were employed in determining solid flow pattern in the riser. It was observed that the flow regimes changed from fast fluidization to core-annulus and to homogeneous dilute bed when the gas velocities increased from 7, 8 and 9 m/s, respectively. The results from high-speed camera showed that glass beads velocity existed a maximum value at the center of the riser and gradually decreased toward the wall for all three gas velocities. It was also found that most of solid traveled upward in the core of the riser, however, solid traveled downward was identified at the wall layer.     

A study towards release dynamics of thiram fungicide from starch-alginate beads to control environmental and health hazards

In order to make the judicious use of thiram fungicide we have developed starch- and alginate-based controlled and sustained agrochemical delivery system in the form of beads using calcium chloride (CaCl2) as crosslinker. The beads were characterized by FTIR and swelling studies. To study the effect of composition of the beads on the release dynamics of fungicide (thiram), beads were prepared by varying the amount of starch, alginate and crosslinker in the beads. Formulation characteristics like entrapment efficiency, bead size, percentage equilibrium swelling of the beads and diffusion mechanism for thiram release have been evaluated. Maximum (93.33+/-2.89)% swelling and maximum (80.67+/-0.83)% thiram release has occurred in the beads prepared with 15% starch, 1% alginate and 0.1M crosslinker solution. In most of the formulations the entrapment efficacy of thiram has been observed more than 90% and the values for the diffusion exponent 'n' have been obtained >1 which shows that the release of fungicides occurred through Case II diffusion mechanism.     

Adsorption equilibria of reactive dye onto highly polyaminated porous chitosan beads

The adsorption of vinyl sulfone type reactive black 5 (RB 5) in aqueous solution onto chitosan beads and cross-linked chitosan beads with glutaraldehyde has been investigated in terms of initial pH and temperature of the solution. The adsorption equilibrium data were correlated with three adsorption models, such as Langmuir, Freundlich and Sips isotherms. Among them, the Freundlich isotherm best fit the data over the entire pH and temperature range of the solution. The adsorption capacity of RB 5 onto chitosan beads and cross-linked chitosan beads increased with decreasing initial pH and with increasing temperature. Equilibrium amount of RB 5 on chitosan beads was greater than that of cross-linked chitosan beads at the same initial pH values. Thermodynamic studies have also been carried out and values of standard free energy (°Gℴ), enthalpy (°Hℴ) and entropy (°Sℴ) were calculated.