Dynamics of controlled release of heparin from swellable crosslinked starch microspheres

The microspheres of crosslinked starch have been prepared and characterized by IR spectral analysis and SEM technique. The prepared microspheres were loaded with an anticoagulant drug ‘heparin’ and the kinetics of in-vitro release of heparin was investigated spectrophotometrically at physiological pH (7.4) and body temperature (37 °C). The influence of percent loading of heparin, chemical architecture of the microspheres and pH of the release medium were examined on the release profiles of the drug. The chemical stability of heparin was tested in phosphate buffer saline (pH 7.4) and the release was also studied in various simulated biological fluids.     

Fast and controlled release of triamcinolone acetonide from extrusion-spheronization pellets based on mixtures of native starch with dextrin or waxy maize starch

Pellets composed chiefly of inexpensive starches allow modulation of the rate of release of the poorly soluble drug triamcinolone acetonide in media of pH 1.2-6.8. Wheat- or maize-starch-based pellets with 20% of white dextrin release the drug in vitro almost completely within 20 min, while maize-starch-based pellets with 5-35% of waxy maize starch sustain gradual release over periods of 9-12 hr or longer when prepared using appropriate amounts of granulation fluid.     

Mixture design for evaluation of potassium sorbate and xanthan gum effect on properties of tapioca starch films obtained by extrusion

A mixture experimental design was used to study the physical and microbiological properties of tapioca starch–glycerol based edible films added with xanthan gum (XG) and potassium sorbate (PS) and obtained by extrusion technology. The results showed that PS presence decreased the ultimate tensile strength and elastic modulus and increased strain at break. XG produced a reinforcing effect on the films and also enhanced solubility in water and decreased moisture content. The analysis revealed significant interactions between components in the mixture. The water vapor permeability values ranged from 3.72 × 10^? 10 to 6.4 × 10^? 10 g/m s Pa. The PS concentration was not affected by the extrusion process and the preservative was available to act as an antimicrobial agent. Extruded films made from biopolymers showed a potential application in food technology as an active packaging.     

Release of potassium sorbate from active films of sodium alginate crosslinked with calcium chloride

The release of potassium sorbate from alginate films was evaluated considering different active agent concentrations in the film and three levels of alginate crosslinking. The mechanism involved in the diffusional process was investigated using the Power Law Model. The results indicated that potassium sorbate diffusion in alginate films has characteristics of Fickian and non‐Fickian behaviour. Effective diffusion coefficients obtained using the solution in series derived from Fick's Second Law are close to values obtained by the short‐time solution, indicating that the influence of swelling on effective diffusivity, although perceptible, is small, allowing the use of an average effective diffusivity. The values of effective diffusivity found indicate that alginate films have a potential use as systems for release of active substances. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of carbon sphere from corn starch by a simple method

Carbon spheres with a regular and perfect shape was successfully synthesized from corn starch by a two stage process: oxidation and carbonization. In this process, oxidation treatment was the main step; the optimal oxidation temperature was 210 °C. The resulting products were characterized by using combined techniques including X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The results showed that the products could keep the original shape of corn starch perfectly, and the diameters of carbon spheres ranged from 5 to 25 μm. It showed characteristic structure of non-graphitizing carbons heated at high temperatures. The preparation mechanism has also been discussed.     

Evaluation of starch based cryogels as potential biomaterials for controlled release of antibiotic drugs

In the present study starch has been blended with poly(vinyl alcohol) to design macroporous architectures following a repeated freeze-thaw method. These macroporous cryogels were loaded with an antibiotic drug, ciprofloxacin hydrochloride (Cfx), and evaluated for its in vitro delivery in a completely controlled manner thus exploring possibilities to use it as a biomaterial in burn or wound healing applications. The key advantage of the present system is that cryogels formed do not contain any chemical crosslinking agent which is often harmful to organic compounds. These Cfx loaded cryogels were characterized by infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The controlled release of Cfx drug from cryogels was investigated under varying experimental conditions such as percent loading of the antibiotic drug, chemical architecture of the cryogels and pH, temperature, and nature of the release media. The prepared cryogels show promise to provide a possible pathway for controlling delivery of antibiotic drug thus minimizing the known side effects and improving efficacy also.     

Drug release from heat-treated polyvinyl alcohol films

Polyvinyl alcohol (PVA) films containing 10% w/w of a model drug, sulphathiazole, were cast from aqueous solutions and subjected to heat treatment at specific temperatures for known periods of time. Heat treatment at temperatures above the T_g of the PVA films slowed down the rate of drug release from the films. Increasing the temperature of heat treatment from 120°C to 160°C further decreased the rate of drug release. On the other hand, if the heat treatment were conducted at a temperature below the T_g e.g. at 80°C, there were insignificant differences between the release profile of sulphathiazole from heat-treated films and that from untreated films. The duration of heat treatment affected the rate of drug release to a smaller extent compared to the temperature of heat treatment. These results correlated with the heat induced changes in the morphology of, and in the extent of water uptake by the PVA films.     

Drug release from heat-treated polyvinyl alcohol films

Abstract

Polyvinyl alcohol (PVA) films containing 10% w/w of a model drug, sulphathiazole, were cast from aqueous solutions and subjected to heat treatment at specific temperatures for known periods of time. Heat treatment at temperatures above the T_g of the PVA films slowed down the rate of drug release from the films. Increasing the temperature of heat treatment from 120°C to 160°C further decreased the rate of drug release. On the other hand, if the heat treatment were conducted at a temperature below the T_g e.g. at 80°C, there were insignificant differences between the release profile of sulphathiazole from heat-treated films and that from untreated films. The duration of heat treatment affected the rate of drug release to a smaller extent compared to the temperature of heat treatment. These results correlated with the heat induced changes in the morphology of, and in the extent of water uptake by the PVA films.     

Dexamethasone electrically controlled release from polypyrrole-coated nanostructured electrodes

One of the key challenges to engineering neural interfaces is to reduce their immune response toward implanted electrodes. One potential approach to minimize or eliminate this undesired early inflammatory tissue reaction and to maintain signal transmission quality over time is the delivery of anti-inflammatory biomolecules in the vicinity of the implant. Here, we report on a facile and reproducible method for the fabrication of high surface area nanostructured electrodes coated with an electroactive polymer, polypyrrole (PPy) that can be used to precisely release drug by applying an electrical stimuli. The method consists of the electropolymerization of PPy incorporated with drug, dexamethasone (DEX), onto a brush of metallic nanopillars, obtained by electrodeposition of the metal within the nanopores of gold-coated polycarbonate template. The study of the release of DEX triggered by electrochemical stimuli indicates that the system is a true electrically controlled release system. Moreover, it appears that the presence of metallic nanowires onto the electrode surface improves the adherence between the polymer and the electrode and increases the electroactivity of the PPy coating.     

The controlled release of tilmicosin from silica nanoparticles

The aim of this study was to use silica nanoparticles as the carrier for controlled release of tilmicosin. Tilmicosin was selected as a drug model molecule because it has a lengthy elimination half-life and a high concentration in milk after subcutaneous administration. Three samples of tilmicosin-loaded silica nanoparticles were prepared with different drug-loading weight. The drug-loading weight in three samples, as measured by thermal gravimetric analysis, was 29%, 42%, and 64%, respectively. With increased drug-loading weight, the average diameter of the drug-loaded silica nanoparticles was increased from 13.4 to 25.7?nm, and the zeta potential changed from?30.62 to?6.78 mV, indicating that the stability of the drug-loaded particles in the aqueous solution decreases as drug-loading weight increases. In vitro release studies in phosphate-buffered saline showed the sample with 29% drug loading had a slow and sustained drug release, reaching 44% after 72?h. The release rate rose with increased drug-loading weight; therefore, the release of tilmicosin from silica nanoparticles was well-controlled by adjusting the drug loading. Finally, kinetics analysis suggested that drug released from silica nanoparticles was mainly a diffusion-controlled process.     

The controlled release of tilmicosin from silica nanoparticles

The aim of this study was to use silica nanoparticles as the carrier for controlled release of tilmicosin. Tilmicosin was selected as a drug model molecule because it has a lengthy elimination half-life and a high concentration in milk after subcutaneous administration. Three samples of tilmicosin-loaded silica nanoparticles were prepared with different drug-loading weight. The drug-loading weight in three samples, as measured by thermal gravimetric analysis, was 29%, 42%, and 64%, respectively. With increased drug-loading weight, the average diameter of the drug-loaded silica nanoparticles was increased from 13.4 to 25.7?nm, and the zeta potential changed from-30.62 to-6.78 mV, indicating that the stability of the drug-loaded particles in the aqueous solution decreases as drug-loading weight increases. In vitro release studies in phosphate-buffered saline showed the sample with 29% drug loading had a slow and sustained drug release, reaching 44% after 72?h. The release rate rose with increased drug-loading weight; therefore, the release of tilmicosin from silica nanoparticles was well-controlled by adjusting the drug loading. Finally, kinetics analysis suggested that drug released from silica nanoparticles was mainly a diffusion-controlled process.     

Controlled release of tetracycline-HCl from halloysite-polymer composite films

The first direct comparison between two common methods for loading halloysite with a small molecule for controlled release is presented. While the methods differ in the degree of simplicity, they provide essentially the same level of loading and release kinetics. A tentative explanation of the "burst" effect often seen in the release of low molecular weight molecules from halloysite is provided. The ability of halloysite to mediate the release rate of a water soluble drug, tetracycline, from solution cast polyvinyl alcohol and polymethyl methacrylate films was evaluated. In some films, montmorillonite was also incorporated. The addition of montmorillonite to solutions used to cast tetracycline containing films significantly reduced the release rate from the dried films. The same overall effect was seen when the drug was loaded into halloysite prior to preparation of the films. In both cases, the release was best fit with the simple Higuchi model. However, when montmorillonite was added to solutions of polyvinyl alcohol and drug loaded halloysite the release profiles were better fit by the Ritgar-Peppas model for anomalous transport. Release from polymethyl methacrylate was reduced by a factor of three by incorporating the drug in halloysite prior to producing the films.     

Evaluation and controlled release characteristics of modified xanthan films for transdermal delivery of atenolol

The present study was performed to evaluate the possibility of using modified xanthan films as a matrix system for transdermal delivery of atenolol (ATL), which is an antihypertensive drug. Acrylamide was grafted onto xanthan gum (XG) by free radical polymerization using ceric ion as an initiator. Fourier transform infrared spectroscopy and differential scanning calorimetry indicated the formation of the graft copolymer. The obtained graft copolymer was loaded with ATL and films were fabricated by solution casting method for transdermal application. Various formulations were prepared by varying the grafting ratio, drug loading, and different penetration enhancers. The formulations prepared were characterized for weight, thickness uniformity, water vapor transmission rate, and uniformity in drug content of the matrix. All the thin films were slightly opaque, smooth, flexible, and permeable to water vapor, indicating their permeability characteristics suitable for transdermal studies. Fourier transform infrared spectroscopy and differential scanning calorimetry studies indicated no significant interactions between drug and polymer. Drug is distributed uniformly in the matrix but showed a slight amorphous nature. Drug-loaded films were analyzed by X-ray diffraction to understand the drug polymorphism inside the films. Scanning electron microscopic studies of the placebo and drug-loaded films demonstrated a remarkable change in their surface morphology. The skin irritation tests were performed in mice and these results suggested that both placebo and drug-loaded films produced negligible erythema and edema compared to formalin (0.8% v/v) as the standard irritant. The in vitro drug release studies were performed in phosphate buffer saline using a Keshary-Chien diffusion cell. Different formulations were prepared and variations in drug release profiles were observed. Release data were analyzed by using the Ritger and Peppas equation to understand the mechanism of drug release as well as the estimation of n values, which ranged between 0.41 and 0.53, suggesting a Fickian diffusion trend.     

Insulin release bio-platform from all nano-container assembled thin films

We introduce nano-container assembled multilayer structures for controlling the release of human insulin. Two block copolymer micelles (BCMs) were used as a nano-container for hydrogen bonding-based, layer-by-layer (LbL) assembly of thin films. BCMs were composed of either hairy (long corona region relative to the hydrophobic core part) or crew-cut (huge hydrophobic core chains, compared with the hydrophilic corona region) polystyrene-block-poly(4-vinylpyridine) and polystyrene-block-poly(acrylic acid) micelles. Human insulin-encapsulated BCM multilayer structures were deconstructed when rehydrated in model physiological conditions (37 °C, 5% CO₂), phosphate buffer saline solutions (pH 7.4), and released BCMs as an insulin carrier, suggesting that the dissociation behavior of BCMs integrated into the LbL‐assembled structures differs due to BCM combinations. These results indicate the preparing functional platforms for biomedical applications including the controlled release of insulin. MC3T3 cells were suggested for the cell viability and adhesion onto BCM multilayer thin films.     

Biocompatibilty of starch-based films from starch of Andean crops for biomedical applications

In this communication we report the use of starch films as cell substrates. To the best of our knowledge it is the first time that films prepared from native Andean starches are studied as biomaterials. For the present study 3T3 fibroblast cells were seeded in seventeen novel starch based films from different Andean crops. In order to analyze the use of these types of starch as biomedical materials, biocompatibility, viability and cell adhesion studies were performed at the third day of incubation on supplemented DMEM medium. After cultured, films made from starch of “tunta”, “muro-huayro” potato and white carrot showed the highest level of living cells and cell viability. These results indicate that native starches from Andean crops can be used for biomedical applications.     

pH响应性可控释放材料

智能可控释放材料由于具有多种潜在的用途而引起广泛关注.其中,具有pH响应性的可控释放材料被认为是较易获得并对外界环境刺激响应较敏感的一类智能响应性材料.本文综述了具有不同结构的pH响应性可控释放材料的研究进展,包括pH响应性微胶囊、pH响应性聚合物微球、pH响应性水凝胶、pH响应性介孔材料的制备、可控释放作用及其应用.     

谈玉米淀粉废水治理的一种新工艺

本文主要论述玉米淀粉治理新工艺,从源头抓起,按资源化,减量化,无害化的原则对玉米淀粉废水进行综合治理,减少污染排放物,更好地提高玉米加工的经济效益,实现经济效益、环境效益双赢。     

Electrically controlled drug release from nanostructured polypyrrole coated on titanium

Previous studies have demonstrated that multi-walled carbon nanotubes grown out of anodized nanotubular titanium (MWNT-Ti) can be used as a sensing electrode for various biomedical applications; such sensors detected the redox reactions of certain molecules, specifically proteins deposited by osteoblasts during extracellular matrix bone formation. Since it is known that polypyrrole (PPy) can release drugs upon electrical stimulation, in this study antibiotics (penicillin/streptomycin, P/S) or an anti-inflammatory drug (dexamethasone, Dex), termed PPy[P/S] or PPy[Dex], respectively, were electrodeposited in PPy on titanium. The objective of the present study was to determine if such drugs can be released from PPy on demand and (by applying a voltage) control cellular behavior important for orthopedic applications. Results showed that PPy films possessed nanometer-scale roughness as analyzed by atomic force microscopy. X-ray photoelectron spectroscopy confirmed the presence of P/S and Dex encapsulated within the PPy films. Results from cyclic voltammetry showed that 80% of the drugs were released on demand when sweep voltages were applied for five cycles at a scan rate of 0.1 V s(-1). Furthermore, osteoblast (bone-forming cells) and fibroblast (fibrous tissue-forming cells) adhesion were determined on the PPy films. Results showed that PPy[Dex] enhanced osteoblast adhesion after 4 h of culture compared to plain Ti. PPy-Ti (with or without anionic drug doping) inhibited fibroblast adhesion compared to plain Ti. These in vitro results confirmed that electrodeposited PPy[P/S] and PPy[Dex] can release drugs on demand to potentially fight bacterial infection, reduce inflammation, promote bone growth or reduce fibroblast functions, further implicating the use of such materials as implant sensors.