Biotin-doped porous polypyrrole films for electrically controlled nanoparticle release

A novel method for the preparation of biotin-doped porous conductive surfaces has been suggested for a variety of applications, especially for an electrically controlled release system. Well-ordered and three-dimensional porous conductive structures have been obtained by the electrochemical deposition of the aqueous biotin-pyrrole monomer mixture into particle arrays, followed by subsequent removal of the colloidal particles. Advantageously, direct incorporation of biotin molecules enhances the versatility by modifying surfaces through site-directed conjugate formation, thus facilitating further reactions. In addition, the porosity of the surfaces provides a significant impact on enhanced immobilization and efficient release of streptavidin-tagged gold nanoparticles. Biotinylated porous polypyrrole (Ppy) films were characterized by several techniques: (1) scanning electron microscopy (SEM) to evaluate surface topography, (2) X-ray photoelectron spectroscopy (XPS) to assess the potential-dependent chemical composition of the films, (3) four-point probe evaluation to measure the conductivity, cyclic voltammetry to observe surface eletroactivity, and contact angle measurement to evaluate the surface wettability, and (4) fluorescence microscopy to image and quantify the adsorption and release of gold nanoparticles. Overall, our results demonstrate that these biotinylated porous Ppy films, combined with electrical stimulation, permit a programmable release of gold nanoparticles by altering the chemical strength of the Ppy-biotin interaction.     

Thermal degradation studies of alkyl-imidazolium salts and their application in nanocomposites

Increasing the thermal stability of organically-modified layered silicates is one of the key points in the successful technical application of polymer-layered silicate nanocomposites on the industrial scale. To circumvent the detrimental effect of the lower thermal stability of alkyl ammonium-treated montmorillonite, a series of alkyl-imidazolium molten salts were prepared and characterized by elemental analysis, thermogravimetry (TGA) and thermal desorption mass spectroscopy (TDMS). The effect of counter ion, alkyl chain length and structural isomerism on the thermal stability of the imidazolium salts was investigated. Alkyl-imidazolium-treated montmorillonite clays were prepared by ion exchange of the imidazolium salts with Na-montmorillonite. These organically-modified clays were characterized by X-ray diffraction (XRD), TDMS and thermogravimetry coupled with Fourier transform infrared spectroscopy (TGA-FTIR), and compared to the conventional quaternary alkyl ammonium montmorillonite. Results indicate that the counter ion has an effect on the thermal stability of the imidazolium salts, and that imidazolium salts with PF₆⁻, N(SO₂CF₃)₂⁻ and BF₄⁻ anions are thermally more stable than the halide salts. A relationship was observed between the chain length of the alkyl group and the thermo-oxidative stability; as the chain length increased from propyl, butyl, decyl, hexadecyl, octadecyl to eicosyl, the stability decreased. The results also show that the imidazolium-treated montmorillonite has greater thermal stability compared to the imidazolium halide. Analysis of the decomposition products by FTIR provides an insight about the decomposition products which are water, carbon dioxide and hydrocarbons.     

Biodegradable polymer/clay systems for highly controlled release of NPK fertilizer

The aim of this work was to obtain biodegradable polymeric systems based on poly(hydroxybutyrate) (PHB) for use in the controlled release of agrochemicals and to analyze the relationship between the properties of polymers and the rates of release of active compounds. Two types of systems were obtained: one using nitrogen, phosphorous, and potassium (NPK) fertilizer directly mixed within the polymer matrix and another with the fertilizer previously incorporated in bentonite (Bent) and mixed with the polymer. The systems were obtained by melt processing and then evaluated by their properties. The release of the active compounds was analyzed by conductometric analysis using an aqueous solution as release medium for 240 hours. The obtained results were correlated with the biodegradation process of PHB. All of the systems presented a significant reduction in the active compounds released to the environment as compared with the direct application of NPK. The PHB/NPK systems showed a release of up to 37% of the compounds, while the PHB/m‐Bent showed greater control, with a release between 4% and 11% after 240 hours. In addition, the properties of the polymer systems presented a direct relationship with the rate of active compounds released. The type of production process, properties, and biodegradability indicate interesting potential of these systems for application in the controlled release of active compounds.     

Synthesis and characterization of molecularly imprinted polymer for controlled release of tramadol

In this paper, we describe how to prepare a highly selective imprinted polymer by a bulk polymerization technique. We used tramadol as the template, (MAA) as functional monomers, and (EGDMA) as the cross-linker in chloroform as solvent. Results from Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Scanning Electron microscopy (SEM) show that this imprinted sorbent exhibits good recognition and high affinity for tramadol. Selectivity of molecularly imprinted polympers (MIP) was evaluated by comparing several substances with similar molecular structures to that of tramadol. Controlled release of tramadol from MIPs was investigated through in vitro dissolution tests and by measuring the absorbance at λ _max of 272 nm by (HPLC-UV). The dissolution media employed were hydrochloric acid pH 3.0 and phosphate buffers, pH 5.0 and 7.4, maintained at 37 and 25 ± 0.5°C. The results show the ability of MIP polymers to control tramadol release. In all cases, the release of MIPs was deferred for a longer time as compared to NMIP. At a pH of 7.4 and 25°C slower release of tramadol imprinted polymer occurred.      

Synthesis and characterization of ZnS-montmorillonite nanocomposites and their application for degrading eosin B

Nanocomposites of zinc sulfide (ZnS) and montmorillonite (MMT) were prepared via a hydrothermal route. In this method, the MMT treated with hexadecyltrimethyl ammonium bromide (HTAB) aqueous solution was dispersed in the aqueous solution of thiourea and Zn(OOCHCH(3))(2)2H(2)O, and heated at 170 degrees C for about 4 h, resulting in ZnS-MMT composites. The as-prepared nanocomposites were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. It was demonstrated that the interlayer space of MMT was enlarged from 0.98 to 3.77 nm after the treatment with HTAB aqueous solution, and the ZnS nanoparticles were deposited on the layers of MMT. Nitrogen sorption analysis demonstrated that the specific surface area of the samples decreased from 39.2 m(2)/g of the pristine MMT to 5.9 m(2)/g of the final ZnS-MMT composites. The resulting ZnS-MMT nanocomposites (50.0 mg) could degrade eosin B completely in aqueous solution (75 ml, 3.2x10(-5) M) within 20 min under UV irradiation.     

Preparation and characterization of hyaluronate-hydroxyethyl acrylate blend hydrogel for controlled release device

Hyaluronate-hydroxyethyl acrylate blend hydrogels were investigated as matrices for controlled release devices. Glycidyl methacrylate (GMA) derivatized HA (GMA-HA) was synthesized by coupling of GMA to HA in the presence of a suitable catalyst. These hydrogels were prepared by a free radical copolymerization of GMA-HA and hydroxyethyl acrylate. The water content of these hydrogels at equilibrium swelling in water (Ww) was 0.978+/-0.0073 (n=18); however, these hydrogel was mechanically tough and could be used as disk shape. The hydrogels swelling were found to depend on ionic strength and pH. The dried hydrogels quickly regained their original condition in water, and they swelled to more than 90% of its initial water contents after 30 min. This swelling-deswelling behavior was reproducible. The release of chlorpromazine HCl as a model cationic drug from the gels was suppressed significantly in water. The release increased with increasing the ionic strength and decreasing pH of bulk solutions.     

Synthesis and characterization of a pH responsive and mucoadhesive drug delivery system for the controlled release application of anti-cancerous drug

In this work a novel pH sensitive composite, polyacrylamide grafted succinyl chitosan intercalated bentonite (AAm-g-NB/SC) was prepared as a drug carrier system for the controlled delivery of paclitaxel. Characterization of the drug delivery system was carried out using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis etc. The equilibrium swelling behaviour of the composite was studied and the result showed a maximum at pH 7.4. The in vitro drug release study of paclitaxel indicated that about 15.6% of drug release was found to be occurred at pH 1.2 within 16 h, whereas about 82.5% of drug release was occurred at the intestinal pH condition of 7.4. In vitro biocompatibility study was performed and the result showed good biocompatibility of the composite in the concentration range 6.25–100 µg/mL. The cytotoxicity assay was carried out in cancerous cell line of Human colorectal Adenocarcinoma. Mucous glycoprotein assay study showed that the drug delivery system having good apparent adhering property towards mucin. The investigation indicated that paclitaxel, an anticancer drug can be successfully entrapped in the AAm-g-NB/SC composite for the controlled and targeted delivery for colorectal cancer therapy.     

3D highly porous microspherical morphology of NiO nanoparticles for supercapacitor application

Journal of Solid State Electrochemistry - In the present work, the effect of reaction temperature and urea concentration on the electrochemical performance of NiO nanoparticles is investigated. The...     

Fabrication of hollow porous PLGA microspheres for controlled protein release and promotion of cell compatibility

This letter reports on the fabrication of hollow,porous and non-porous poly(D,L-lactide-co-glycolide) (PLGA) microspheres(MSs) for the controlled release of protein and promotion of cell compatibility of tough hydrogels.PLGA MSs with different structures were prepared with modified double emulsion methods,using bovine serum albumin(BSA) as a porogen during emulsification.The release of the residual BSA from PLGA MSs was investigated as a function of the MS structure.The hollow PLGA MSs show a faster protein release than the porous MSs,while the non-porous MSs have the slowest protein release.Compositing the PLGA MSs with poly(vinyl alcohol)(PVA) hydrogels promoted chondrocyte adhesion and proliferation on the hydrogels.     

A reservoir-type controlled release device using aqueous-organic partitioning and a porous membrane

A reservoir-type controlled release device based on aqueous-organic partitioning is described. The reservoir is bounded by a microporous or porous membrane, either a hollow fiber or a flat film. The agent partitions between phases at the aqueous-organic interface of the reservoir and the pore mouth, and then diffuses through the membrane pore into a surrounding aqueous solution. The partition coefficient significantly influences the rate of release of the agent. The performance of the system is evaluated using model agents. Controlled release from a reservoir containing a pure organic liquid agent is demonstrated using toluene. Zero-order release is achieved for benzoic acid partitioning from an organic reservoir into water-filled pores, and for nicotine partitioning from an aqueous reservoir into organic-filled pores. Studies using benzoic acid demonstrate the effectiveness of a thin, nonporous coating on slowing the rate of release. A fast-dissolving suspension of benzoic acid in decanol extends the duration of zero-order release. Two agents, nicotine and caffeine, are released simultaneously and independently from a divided reservoir. A simplified mathematical model is presented, and experimental results compared well with those predicted by the model.     

Thermal characterization and compatibility studies of norfloxacin for development of extended release tablets

Norfloxacin (NFX) is a synthetic antibacterial drug. The development of extended release tablets improves the patients’ comfort and compliance, resulting in lower discontinuation of the therapy; with consequently decrease in bacterial resistance. In the present work, the thermal behavior of NFX was investigated using TG and DSC techniques. Isothermal and non-isothermal methods were employed to determine kinetic data of decomposition process. Compatibility studies between NFX and pharmaceutical excipients, including three hydrophilic polymers were carried out in order to develop a new formulation of NFX to obtain extended release tablets with an approved quality.     

Chemical synthesis of MnFe2O4/chitosan nanocomposites for controlled release of ofloxacin drug

In this study, we synthesized ofloxacin‐loaded MnFe₂O₄ nanoparticles (NPs) surface modified with chitosan (CS‐MnFe₂O₄) for prolonged antibiotic release in a controlled manner. It was found that the synthesized CS‐MnFe₂O₄ was spherical in shape with an average size of 30–50 nm, low aggregation, and good magnetic responsibility. An in vitro drug loading and release kinetics study reveals that the drug delivery system can take 86% of drug load and can release ofloxacin over a sustained period of 3 days. The release kinetics study reveals that the drug follows zero order kinetics and the mechanism of drug release is diffusion‐controlled type. These results indicated that CS‐MnFe₂O₄ NPs with pH‐sensitive properties can be used as candidates for intestinal targeted drug delivery through oral administration by avoiding the drug release in the highly acidic gastric fluid region of the stomach.     

Fabrication of highly porous starch monoliths and their application as green desiccants

Starch monoliths with oriented porous structures were developed from starches and glycerin as a plasticizer using unidirectional freeze‐drying technology. The morphology of the porous starch monoliths made from different starches was determined by scanning electron microscopy (SEM), and the porosity, mechanical properties and moisture absorption of the porous materials were evaluated. The results show that porous starch monoliths made from oxidized starch with 15% glycerin had good mechanical strength with the best moisture absorption. Increasing the starch concentration significantly improved their strength and increased the moisture absorption rate as well. The moisture absorption of the porous monolith made from oxidized starch is comparable with commonly used desiccants. The porous starch monoliths can successfully remove water from 95% ethanol to produce absolute ethanol due to their selective absorption for water. Copyright © 2011 John Wiley & Sons, Ltd.     

Study of controlled tetracycline release from porous calcium phosphate/polyhydroxybutyrate composites

Porous calcium phosphate ceramics were prepared by sintering of mixtures of nanocrystalline apatitic calcium phosphate and fibrous natural cotton cellulose after pressing at temperatures of 1150 °C and 1250 °C. Micro-and macropores were present in microstructures of ceramic samples. The microstructures of porous ceramics were similar to those observed in bone tissues and fiber-like randomly oriented texture was observed in ceramics. Polyhydroxybutyrate (PHB) biopolymer layers are distributed homogeneously in the samples after evaporation of the diluent (chloroform) from the PHB vacuum impregnated porous samples. The tetracycline (TTC) release rate decreases with the content of polyhydroxybutyrate in the ceramic samples, which corresponds to the rise in amount of biopolymer displaced in the pores of ceramics. The concentration of TTC in the phosphate buffer saline solution varies almost linearly with time after the first seven hours from the start of the release of the calcium phosphate ceramic samples with 2.4 mass % of polyhydroxybutyrate. The initial burst effect was significantly depressed by the preparation method used.     

Preparation and characterization of controlled heparin release waterborne polyurethane coating systems

In this study, to improve hemocompatibility of biomedical materials, a waterborne polyurethane (WPU)/heparin release coating system (WPU/heparin) is fabricated via simply blending biodegradable WPU emulsions with heparin aqueous solutions. The surface compositions and hydrophilicity of these WPU/heparin blend coatings are characterized by attenuated total reflectance infrared spectroscopy (ATR-FTIR) and water contact angle measurements. These WPU/heparin blend coatings show effectively controlled release of heparin, as determined by the toluidine blue method. Furthermore, the biocompatibility and anticoagulant activity of these blend coatings are evaluated based on the protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), thrombin time (TT), hemolysis, and cytotoxicity. The results indicate that better hemocompatibility and cytocompatilibity are obtained due to blending heparin into this waterborne polyurethane. Thus, the WPU/heparin blend coating system is expected to be valuable for various biomedical applications.     

Preparation and characterization of PLGA particles for subcutaneous controlled drug release by membrane emulsification

Uniformly sized microparticles of poly(d,l-lactic-co-glycolic) (PLGA) acid, with controllable median diameters within the size range 40–140 μm, were successfully prepared by membrane emulsification of an oil phase injected into an aqueous phase, followed by solvent removal. Initially, simple particles were produced as an oil in water emulsion, where dichloromethane (DCM) and PLGA were the oil phase and water with stabiliser was the continuous phase. The oil was injected into the aqueous phase through an array type microporous membrane, which has very regular pores equally spaced apart, and two different pore sizes were used: 20 and 40 μm in diameter. Shear was provided at the membrane surface, causing the drops to detach, by a simple paddle stirrer rotating above the membrane. Further tests involved the production of a primary water in oil emulsion, using a mechanical homogeniser, which was then subsequently injected into a water phase through the microporous membrane to form a water in oil in water emulsion. These tests used a water-soluble model drug (blue dextran) and encapsulation efficiencies of up to 100% were obtained for concentrations of 15% PLGA dissolved in the DCM and injected through a 40 μm membrane.

Solidification of the PLGA particles was followed by removal of the DCM through the surrounding aqueous continuous phase. Different PLGA concentrations, particle size and osmotic pressures were considered in order to find their effect on encapsulation efficiency. Osmotic pressure was varied by changing the salt concentration in the external aqueous phase whilst maintaining a constant internal aqueous phase salt concentration. Osmotic pressure was found to be a significant factor on the resulting particle structure, for the tests conducted at lower PLGA concentrations (10% and 5% PLGA). The PLGA concentration and particle size distribution influence the time to complete the solidification stage and a slow solidification, formed by stirring gently overnight, provided the most monosized particles and highest encapsulation efficiency.     

Modification of poly(benzimidazole‐amide) nanocomposites by the incorporation of amine‐functionalized ZnO nanoparticles: Thermal and morphological characterization

Fabrication, characterization, and properties of novel poly(benzimidazole‐amide)/functionalized ZnO nanocomposites (PBIA/APS‐ZnO NCs) were investigated. At first, an aromatic PBA containing 3 imidazole units per repeat unit was synthesized by direct polycondensation of 1,3‐bis(5‐carboxylic acid‐2‐benzimidazole)benzene (BCAB) with 5‐(2‐benzimidazole)‐1,3‐phenylenediamine (DAMI) with good yield as a polymeric matrix. The periphery of zinc oxide nanoparticles (ZnO NPs) was modified with 3‐aminopropyltriethoxysilane (APS) to have a better dispersion NPs and enhancing interactions between nanoparticles and PBIA matrix. Different percentages of functionalized NPs (0, 4, 8, and 12 wt.%) were then embedded in PBA matrix through ultrasonic irradiation technique. Fourier transform infrared and thermo‐gravimetric analysis (TGA) confirmed that APS was successfully attached on the ZnO NP surface. The obtained NCs were characterized by means of Fourier transform infrared, X‐ray diffraction, scanning electron microscopy, and TGA. The TGA of the PBIA/APS‐ZnO NCs showed the enhancement in the thermal stability in comparison with the neat PBIA and that this increase is higher when the NP content increases. Scanning electron microscopy analyses of NCs revealed that the dispersion of APS‐ZnO NPs was uniformly done in the PBIA matrix.     

Surface structural characterization of highly porous activated carbon prepared from corn grain

A novel corn grain precursor was used for the preparation of activated carbon by chemical activation. The detailed investigation of the porosity development in the prepared activated carbon was done by altering the various activation conditions such as the activation temperature, activation time and ratio between the powdered form of carbonized corn grain char and KOH. The surface characteristics including the surface roughness of all the activated carbon samples were evaluated from the analysis of nitrogen (N₂) adsorption isotherm data. At the maximum of 2978 m²/g, a super surface area having the corn grain‐based activated carbon (CG‐AC) was synthesized by using the following conditions: 1/4 ratio of powdered form of carbonized corn grain char/KOH; 800 °C; and 4 h. The possibility of preparing highly porous activated carbons with controlled porosity by varying different activation conditions was found from the pore size distribution results. In particular, the domination of the ratio between the powdered form of carbonized corn grain char and KOH on the porosity development was high compared to the activation temperature and activation time. In addition, the surface roughness calculated from the surface fractal dimension indicates the decrease of surface roughness with increasing activation conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

Fabrication of biofunctional complex micelles with tunable structure for application in controlled drug release

In acidic solution, complex micelles were formed by diblock copolymers of poly (ethylene glycol)-b-poly (ε-caprolactone) (PEG-b-PCL) and folate-poly (2-(dimethylamino) ethyl methylacrylate)-b-poly (ε-caprolactone) (Fol-PDMAEMA-b-PCL) with a PCL core, a mixed PEG/Fol-PDMAEMA shell. The surface charge of the complex micelles was positive at acidic surroundings for the protonated PDMAEMA. With increasing pH value to 7.4 (above pK _a of PDMAEMA), these micelles could convert into a core-shell-corona (CSC) structure composing a hydrophobic PCL core, a collapsed PDMAEMA shell, and a soluble PEG corona. Compared to core-shell micelles formed by PEG-b-PCL, micelles with CSC structure can prolong degradation by enzyme. Doxorubicin was physically loaded into the PCL core. The drug release rate was pH-dependent. At pH 5.5, complex micelles with core-shell structure showed faster drug release rate, while at pH 7.4, complex micelles gained CSC structure which control the drug release at a lower rate. The multifunctional complex micelles were prepared for enhanced tumor therapy.