Synthesis of quercetin-encapsulated alginate beads with their antioxidant and release kinetic studies

Abstract

In this present study, different forms of quercetin encapsulated beads were synthesized, namely ionic cross-linked gel beads and cryogel beads. Fourier Transform Infrared (FT-IR) spectra of the beads were used to characterize and prove quercetin encapsulation in alginate beads. Swelling and drying profiles were studied. Besides, release kinetics of quercetin molecules from gel beads and cryogels were carefully investigated in two different solvent/media; dimethyl sulfoxide (DMSO) and Roswell Park Memorial Institute Medium (RPMI-1640). Based upon the release kinetic studies, it is found that quercetin release from alginate cryogel beads fits the first-order release model in DMSO and it depends on the concentration of quercetin in the beads. The release of quercetin from alginate gel beads was described by the Higuchi release model, which highlights the release of quercetin molecules through the pores of the matrix. In RPMI-1640, the release of quercetin from both forms of alginate beads fits zero-order release model and it indicates a constant release of quercetin per unit time. Finally, the radical scavenging activity of the quercetin quantities was tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test, and successful results were obtained compared to reference material.     

Antioxidant Activity of Polymers Bearing Hindered Phenolic Groups

Abstract

Polyallylamine and polystyrene beads were allowed to react with 3,5-dibutyl-4-hydroxybenzaldehyde (BHB) and t-butylhydroquinone (BHQ), respectively. The polymeric products, poly-Aa(BHB) and polySt(BHQ) beads worked functionally as antioxidants. The antioxidant effect of the polymer beads in the oxidation of linoleic acid suspensions was investigated by both the ferric thiocyanate and thiobarbituric acid methods. The antioxidant activity of poly-St(BHQ) beads was higher than that of poly-Aa(BHB) ones. It was found that the antioxidant activity for 2 mg of 3, 5-dibutyl-4-hydroxytoluene (BHT) corresponded to that for 11.7 g of poly-Aa(BHB) and that of 0.6 g of poly-St(BHQ). The polymer beads are potential antioxidants for foods since their separation from a food oil after their use is easy because of their insolubility.     

Dynamic Release of Propranolol HCl from Cationic Ion–Exchanger–Loaded Calcium Alginate Beads

The dynamic release of drug propranolol HCl from the propranolol HCl–resin complex (PRC) loaded calcium alginate beads has been studied in the buffer media of pH 1.2 at the physiological temperature 37°C. The PRC encapsulated beads demonstrated nearly 58.04% release while naked PRC particles released 98.00% drug in 24 h in the gastric fluid. The amount of drug released was found to increase with and decrease in the amount of sodium alginate in the beads. Similarly, with the increase in the amount of entrapped PRC particles within the beads, the quantity of drug released was also observed to increase. The degree of crosslinking of beads also affected the release kinetics. Interestingly, the release from naked PRC particles followed ‘first‐order’ kinetics while PRC particles, entrapped in calcium–alginate beads, exhibited ‘diffusion controlled’ release behavior as indicated by liner nature of fractional release vs. √t plot.     

FluMag-SELEX as an advantageous method for DNA aptamer selection

Aptamers are ssDNA or RNA oligonucleotides with very high affinity for their target. They bind to the target with high selectivity and specificity because of their specific three-dimensional shape. They are developed by the so-called Systematic Evolution of Ligands by Exponential Enrichment (SELEX) process. We have modified this method in two steps—use of fluorescent labels for DNA quantification and use of magnetic beads for target immobilization. Thus, radioactive labelling is avoided. Immobilization on magnetic beads enables easy handling, use of very small amounts of target for the aptamer selection, rapid and efficient separation of bound and unbound molecules, and stringent washing steps. We have called this modified SELEX technology FluMag-SELEX. With FluMag-SELEX we have provided a methodological background for our objective of being able to select DNA aptamers for targets with very different properties and size. These aptamers will be applied as new biosensor receptors. In this work selection of streptavidin-specific aptamers by FluMag-SELEX is described. The streptavidin-specific aptamers will be used to check the surface occupancy of streptavidin-coated magnetic beads with biotinylated molecules after immobilization procedures.     

A Bead Injection System for Copper Determination

ABSTRACT

A bead injection system for copper determination is proposed. Chelex-100 resin beads are introduced in the system as a suspension that is trapped in the Jet Ring Cell. The passage of the sample zone by the beads promotes the sorption of Cu(II). When the colorimetric reagent (APDC) perfuses the beads it reacts with copper ions, forming a colored complex that is monitored at 436 nm. After the measurement, the spent beads are sent to waste and a new portion of fresh beads is trapped in the system. The bead injection system is versatile and can be used to concentrate analyte in different sample volumes, permitting determinations of a wide range of copper concentrations. The detection limit is 0.5 μg l^-1 with a 500 μl sample, and 1.2 μg l^-1 with a 100 μ1 sample.     

Synthesis of silver nanoflakes on chitosan hydrogel beads and their antimicrobial potential

Abstract

The present study involves the fabrication of CH and CH-Ag hydrogel beads and the investigation of the antimicrobial properties. The beads were fabricated using a simple coacervation method. The successfully synthesized beads were characterized by UV-Vis and FTIR. The surface morphology, shape and diameter of the samples were determined by optical microscopy and SEM. The antimicrobial activities were determined against potential human pathogens including bacterial and fungal species. Our results demonstrated that beads can be utilized as potential materials for use in biomedical approaches including delivery systems and tissue engineering applications to prevent microbial contamination and to inhibit the growth of microorganisms.     

Determination of Benzylpenicillin In Pharmaceuticals By Capillary Zone Electrophoresis

Abstract

A rapid and direct method is described for the determination of benzylpenicillin (penicillin G) in pharmaceutical preparations. the method involves very little sample preparation and total analysis time for duplicate results is less than 30 minutes per sample.

The method takes advantage of the speed and separating power of capillary zone electrophoresis (CZE). Detection of penicillin is by absorption at 228 nm. an internal standard is employed to reduce sample injection error. the method was applied successfully to both tablets and injectable preparations.

larger on longer aging. It was the authors' hypothesis that this peak was due to formation of penicilloate. When this degradation product was synthesized according to an established procedure¹⁴, CZE retention time of the synthesized product was the same as that final peak in the aged penicillin samples. UV spectra on both solutions was further evidence we had properly identified the degradation product. Thus the relative amount of active and degraded compound in a sample can be estimated readily. Also, this indicates fresh solutions should be used for analytical work.

In conclusion, CZE of penicillin G was shown to not only be possible, but useful in a practical, rapid assay for the level of the antibiotic in pharmaceutical samples. Extension of this work to other types of penicillin and to the variety of samples in which the antibiotic is found in the next logical step.     

Heavy Metal Removal from Synthetic Solutions with Magnetic Beads Under Magnetic Field

The aim of this study is to prepare magnetic beads which can be used for the removal of heavy metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate‐vinyl imidazole) [m‐poly(EGDMA‐VIM)] beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ nano‐powder. The specific surface area of the m‐poly(EGDMA‐VIM) beads was found to be 63.1 m²/g with a size range of 150–200 µm in diameter and the swelling ratio was 85%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA‐VIM) beads was 12.4%. The maximum binding capacities of the m‐poly(EGDMA‐VIM) beads were 32.4 mg/g for Cu²⁺, 45.8 mg/g for Zn²⁺, 84.2 mg/g for Cd²⁺and 134.5 mg/g for Pb²⁺. The affinity order on mass basis is Pb²⁺>Cd²⁺>Zn²⁺>Cu²⁺. Equilibrium data agreed well with the Langmuir model. pH significantly affected the binding capacity of the magnetic beads. Binding of heavy metal ions from synthetic wastewater was also studied. The binding capacities were 26.2 mg/g for Cu²⁺, 33.7 mg/g for Zn²⁺, 54.7 mg/g for Cd²⁺ and 108.4 mg/g for Pb²⁺. The magnetic beads could be regenerated up to about 97% by treating with 0.1 M HNO₃. These features make m‐poly(EGDMA‐VIM) beads a potential candidate for support of heavy metal removal under magnetic field.     

Simpler and More Sensitive Immune Complex Transfer Enzyme Immunoassay for Anti-Htlv-I Igg Using Modified Polystyrene Beads,Microplates and Fluororeader

Abstract

In the previous immune complex transfer enzyme immunoassay for anti-HTLV-I IgG, the transfers of polystyrene beads in and out of test tube were handled with tweezers, and the bound β-D-galactosidase activity was measured with a fluorometer. The use of tweezers was considered the primary cause of false-positivity by carryover. Furthermore, the testing of many samples using a tweezer as a means of transfer was difficult. In the present immune complex transfer enzyme immunoassay, polystyrene beads were attached to plates through cylindrical bars and were used in microplate wells. Therefore, no tweezers were required. The bound β-D-galactosidase activity was measured with a fluororeader. This allowed the elimination of false-positivity due to carryover and made it easier to test many samples with higher sensitivity and reliability.     

Examination of the Higuchi Model for the Release of Vitamin B2 from Multilayered Calcium Alginate/Chitosan Beads in Varying pH Medium

The release of model drug vitamin B₂ from calcium alginate/chitosan multi‐layered beads has been studied in the media of varying pH (3 h in the medium of pH 1.0 and for the remaining time in pH 7.4) at 37°C. The quantitative deviation of experimental data from the Higuchi model has been interpretated by using a newly developed ‘curve area measurement’ (CAM) approach. The higher deviation in the initial phase has been explained on the basis of porous structure of beads due to the use of low molecular weight polymers in the preparation of beads.     

Spectrodensitometric Analysis of Penicillins by Detection with Iodine

Abstract

A rapid, sensitive and selective method is described for the determination of some penicillin derivatives and their additive and degradation products in the presence of each other. Penicillin derivatives are separated from their degradation and additive products on high performance thin layer silica gel G plates. The plates were developed in a linear chamber, air dried, exposed to iodine vapour and measured on a spectrodensitometer at 290 nm. Procaine and procaine penicillin are measured at 360 nm. The results of the analysis show good agreement with the method of the USP XXI. For the reaction of penicillins with iodine, the formation of charge-transfer complexes is considered.     

A Fluorescent Biosensor for Detection of Zearalenone

ABSTRACT

A fluorescent biosensor was developed on a KinExA^TM flow spectrofluorimeter for the near real-time detection of soluble zeaalenone.

Briefly, solutions of zearalenone and a monoclonal antibody directed against a protein conjugate of zearalenone, were incubated for thirty minutes to permit equilibrium binding to occur. The reaction mixture was then passed over a packed column of small beads (98 μm) whose surfaces were coated with a covalent conjugate of zearalenone and bovine serum albumin (BSA). Following a short wash with buffer to remove excess unbound primary reagents, the packed beads were subjected to a brief contact with fluorescein isothiocyanate-labeled polyclonal secondary antibody directed against the primary monoclonal, once again followed by a short wash. As this assay depends on the ability of soluble antigen to compete with immobilized antigen, increasing concentrations of zearalenone result in decreasing fluorescence observed on the bead pack. This assay is rapid (? 60 minutes) and can be adapted to various other analytes of interest.     

SYNTHESIS AND ANTIBACTERIAL ACTIVITY OF SOME METAL COMPLEXES OF BETA-LACTAMIC ANTIBIOTICS

Abstract

An overview of the results of the interaction of β-lactamic antibiotics with some transition metal ions is given. Several complexes have been synthesized and characterized by physicochemical and spectroscopic methods. Some exhibit very promising antibacterial activity. Clavulanic acid (L₁), penicillin (L₂), ampicillin (L₃), cephalexin (L₄), cefazolin (L₅) and cephalothin (L₆) were allowed to react with metal ions in methanol under nitrogen. IR spectra of clavulanic acid, penicillin and ampicillin complexes showed strong modifications of the carbonyl group located on the lactamic ring, indicating that this oxygen participates in the coordination to the metal ions along with the carboxylate group. Thus L₁ and L₂ behave as monoanionic bidentate ligands while L₃ behaves as a monoanionic tridentate ligand. The IR spectra of cephalexin, cefazolin and cephalotin chelates show that the beta lactamic carbonyl group does not participate in coordination to the metal ions. A relationship between the structure of the complexes and their antibacterial activity can be observed.

In vitro antibacterial activity of the antibiotics and the complexes were tested using the filter paper diffusion method and the chosen strains include Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimorium ATCC 14028, Staphylococcus aureus ATCC 6538, Bacillus cereus ATCC 9634, Proteus mirabilis 35659, Proteus vulgaris ATCC 9920, Klebsiella pneumoniae ATCC 10031, Salmonella sp, Shigella sp ATCC 11126, Streptococcus viridans and Salmonella enteritidis ATCC 497.     

Chromatography of E. coli tRNA on 5–20 μm Agarose Beads

Abstract

Escherichia coli transfer RNAs have been separated by chromatography on 5–20 μm beads of divinylsulfone-crosslinked agarose with the use of isocratic elution combined with a negative salt gradient. For example, tRNA^Leu was resolved into six isoacceptor species and tRNA^Ser into four. Leucine-charged tRNA's were eluted after their corresponding uncharged isoacceptor species. By optimizing flow rate, column length and elution buffer the fractionation of tRNA could be performed within 3 hours.     

Flow Rate Dependence of Separation and Broadening Effects in GPC

Abstract

The primary objective of this work is an investigation of the separation and zone brodening effect in columns packed with porous and nonporous materials, and estimation of the accuracy of the broadening parameter, h, obtained by a reverse flow method. In order to study the separation and dispersion phenomenon in the mobile phase, and that caused by a mass-transfer process, columns packed with smooth glass beads and porous silica columns were used.     

Evaluation of Treatments to Attain Isotopic Equilibration of Plutonium Preceding the Resin Bead Technique for Mass Spectrometric Assay Analysis of Spent Reactor Fuel

Abstract

Ten chemical treatments are evaluated for the attainment of isotopic equilibration of plutonium prior to its sorption on resin beads for assay of dissolved reactor fuel by isotope-dilution mass spectrometry. The one consistently reliable treatment is reduction to Pu(III) with heated ferrous sulfamate followed by oxidation to Pu(IV) with heated sodium nitrite.     

Small molecule-dependent genetic selection in stochastic nanodroplets as a means of detecting protein-ligand interactions on a large scale

Background: Understanding the cellular role of a protein often requires a means of altering its function, most commonly by mutating the gene encoding the protein. Alternatively, protein function can be altered directly using a small molecule that binds to the protein, but no general method exists for the systematic discovery of small molecule ligands. Split-pool synthesis provides a means of synthesizing vast numbers of small molecules. Synthetic chemists will soon be able to synthesize natural product-like substances by this method, so compatible screening methods that detect the activity of minute quantities of molecules among many inactive ones will be in demand.Results: We describe two advances towards achieving the above goals. First, a technique is described that uses a simple spray gun to create 5000–8000 droplets randomly, each having a volume of 50–200 nanoliters. The individual ‘nanodroplets’ contain a controlled number of cells and many also contain individual synthesis beads. As small molecules can be photochemically released from the beads in a time-dependent manner, the concentration of ligands that the cells are exposed to can be controlled. The spatial segregation of nanodroplets prevents the mixing of compounds from other beads so the effects of each molecule can be assayed individually. Second, a small molecule-dependent genetic selection involving engineered budding yeast cells was used to detect intracellular protein-ligand interactions in nanodroplets.Conclusions: The technique described here should facilitate the discovery of new cell-permeable ligands, especially when combined with a positive selection assay that detects intracellular binding of small molecules to proteins. Using ‘anchored combinatorial libraries’, it may be possible to screen entire libraries of natural product-like molecules against the entire collection of proteins encoded within cDNA libraries in a single experiment.     

A New Spherical Hydroxyapatite for High Performance Liquid Chromatography of Proteins

Abstract

Basic properties of a newly developed hydroxyapatite column and results of its application to the separation of proteins are described. The hydroxyapatite was completely spherical and porous beads in appearance by scanning electron microscopy, and showed superior properties to other types of hydroxyapatite column. The column was mechanically strong enough to show the pressure limit of 140–150 kg/cm². The hydroxyapatite column showed excellent mechanical and chemical stability, and was applicable to high speed and high resolution separation of proteins. Proteins are recovered in high yield after the chromatography.     

High Performance Liquid Chromatography of Mouse Monoclonal Antibodies on Spherical Hydroxyapatite Beads

Abstract

High performance liquid chromatography (HPLC) on newly developed spherical beads of hydroxyapatite was applied for the simple purification of monoclonal antibodies (mAbs) secreted into mouse ascitic fluid. Sixteen mAbs including all four subclasses of IgG and IgM were separated successfully from serum albumin a major contaminant in the crude mAb preparation by a 30 min-linear gradient of phosphate ion concentration from 0.01M-0.3M at pH 7.2. Not only IgG mAbs but also IgM mAbs were quantitatively eluted from the column. Each antibody had a different retention time (apparent capacity factor of 2.24–4.14) in the chromatography and no relation was found between the retention time and the type of immunoglobulin (class or subclass). A monomeric form of IgM was also resolved successfully from IgM (pentamer) after its reduction with dithiothreitol; the monomer form of IgM was eluted from the column by a lower concentration of phosphate ion than was the pentamer. These results indicate that HPLC on the hydroxylapatite beads will be useful for the purification and characterization of mouse mAbs.     

Rheology of dilute polyelectrolyte solutions in narrow channels

The shear flow of dilute polyelectrolyte solutions bounded by either neutral or repulsive walls is modeled using a nonlinear dumbbell with conformation-dependent friction. Assuming that the configurational probability density function depends on the internal coordinates (r) and the distance of the center of mass of the molecule to the walls, coupled differential equations for the tensor moments <rr> are obtained. Coulombic repulsion between beads is considered to simulate the charge repulsion between ionized sites distributed along the backbone of a real polyelectrolyte. The repulsive interaction between the polyelectrolyte molecule and the charged walls is that of the DLVO model and the molecule is considered to be a charged sphere. Numerical solutions for the components of the tensor <rr> are worked out with the preaverage approach, and only when neutral walls considered are exact solutions obtained. Viscosity results show that in the limit of very wide channels, the corresponding viscosity in the bulk is obtained. The wall repulsion on the charged molecules produces migration of molecules towards the center of the channel resulting in a depleted layer with lower viscosity next to the walls. The calculated slip phenomenon using the method employed by Grisafi and Brunn is dependent on the beads repulsion and the shear rate. The slip velocity obtained with the Mooney method shows similarities with available experimental results for polyelectrolyte solutions. Birefringence calculations are performed in narrow and wide channels for different bead repulsions, with interesting results for both flexible and rigid molecules. Received: 26 September 1998 Accepted in revised form: 11 March 1999