Characterization of khaya gum as a binder in a paracetamol tablet formulation

The influence of khaya gum, a binding agent obtained from Khaya grandifolia (Meliaceae family), on the bulk, compressional, and tabletting characteristics of a paracetamol tablet formulation was studied in comparison with the effects of two standard binders: polyvinylpyrrolidone (PVP; molecular weight 40,000) and gelatin. The relative ability of khaya gum to destroy any residual microbial contamination in the binder or in the formulation during tabletting was also studied using Bacillus subtilis spores as a model. Formulations containing khaya gum exhibited more densification than formulations containing PVP and gelatin during die filling, but less densification due to rearrangement at low pressures. The mean yield pressure of the formulation particles obtained from Heckel plots, and another pressure term, also inversely related to plasticity, obtained from Kawakita plots, showed dependence on the nature and concentration of the binder, with formulations containing khaya gum exhibiting the lowest and highest values respectively. The values of the pressure terms suggest that the yield pressure relates to the onset of plastic deformation during compression, while the Kawakita pressure relates to the total amount of plastic deformation occurring during the compression process. Tablets made from formulations containing khaya gum had the lowest tensile strength values but also the lowest tendency to laminate or cap, as indicated by their lowest brittleness. All the tablets had friability values < 1% at higher concentrations of the three binders. In addition, khaya gum demonstrated a comparable ability to destroy microorganisms in the formulation during tabletting as the two binders. The characterization of the formulations suggests that khaya gum can be developed into a commercial binding agent for particular tablets.     

Evaluation of sorghum starch as a tablet excipient

The suitability of sorghum starch as a binder and disintegrant at various concentrations in diverse tablet formulations have been investigated. Sodium bicarbonate and calcium carbonate were used as soluble and insoluble inorganic medicinal substances in various tablet formulations.

The effect of sorghum starch on the physical properties of the tablets were compared with those formulated with maize starch using the same concentrations of binder and disintegrant under the same experimental conditions.

The observations show that sorghum starch can be used as binder and disintegrant in tablet formulations. The indication is that the starch exhibit about twice the disintegrant power and about the same binding efficacy compared to maize starch.     

Fabrication of carbon papers using polyacrylonitrile fibers as a binder

Carbon papers (CPs) have been fabricated using wet-laying carbon fibers (CFs) and polyacrylonitrile (PAN) fibers. Scanning electron microscopy revealed that the PAN fibers tightly interconnected the CF junctions with the pores between the fibers. The tensile strength of the carbon webs (CWs) increased as the fraction of PAN fibers used as the binder increased. The CW fabricated with 0.15 wt% PAN fibers had a tensile strength six times greater than that of the CW without PAN fibers. Moreover, by mixing the CFs with PAN fibers in water, the CFs separated from each other in the webs due to the interruption of hydrophobicity between the CFs. After mixing with PAN fibers, the CWs were carbonized at 1200 °C in the presence of a phenolic resin. The PAN fibers maintained their morphology due to their high carbon content after carbonization. The electrical resistivity of the CPs with high PAN fiber content was significantly lower than that of a CP without PAN fibers due to the interconnection of the CFs by the carbonized PAN fibers.     

Valorization of phosphogypsum as hydraulic binder

Phosphogypsum (calcium sulfate) is a naturally occurring part of the process of creating phosphoric acid (H₃PO₄), an essential component of many modern fertilizers. For every tonne of phosphoric acid made, from the reaction of phosphate rock with acid, commonly sulfuric acid, about 3 t of phosphogypsum are created. There are three options for managing phosphogypsum: (i) disposal or dumping, (ii) stacking, (iii) use-in, for example, agriculture, construction, or landfill. This paper presents the valorization of two Tunisian phosphogypsums (referred as G and S) in calcium sulfoaluminate cement in the following proportions: 70% phosphogypsum–30% calcium sulfoaluminate clinker. The use of sample G leads to the production of a hydraulic binder which means that it is not destroyed when immersed in water. The binder including sample S performs very well when cured in air but is not resistant in water. Formation of massive ettringite in a rigid body leads to cracking and strength loss.     

Spray-Dried Chitosan as a Direct Compression Tableting Excipient

The objective of this study was to prepare and evaluate a novel spray-dried tableting excipient using a mixture of chitosan and lactose. Three different grades of chitosan (low-, medium-, and high-molecular-weight) were used for this study. Propranolol hydrochloride was used as a model drug. A specific amount of chitosan (1, 1.9, and 2.5 g, respectively) was dissolved in 50 mL of an aqueous solution of citric acid (1%) and later mixed with 50 mL of an aqueous solution containing lactose (20, 19.1, and 18.5 g, respectively) and propanolol (2.2 g). The resultant solution was sprayed through a laboratory spray drier at 1.4 mL/min. The granules were evaluated for bulk density, tap density, Carr index, particle size distribution, surface morphology, thermal properties, and tableting properties. Bulk density of the granules decreased from 0.16 to 0.13 g/mL when the granules were prepared using medium- or high-molecular-weight chitosan compared with the low-molecular-weight chitosan. The relative proportion of chitosan also showed a significant effect on the bulk density. The granules prepared with 1 g of low-molecular-weight chitosan showed the minimum Carr index (11.1%) indicating the best flow properties among all five formulations. All three granules prepared with 1 g chitosan, irrespective of their molecular weight, showed excellent flow properties. Floating tablets prepared by direct compression of these granules with sodium bicarbonate showed 50% drug release between 30 and 35 min. In conclusion, the spray-dried granules prepared with chitosan and lactose showed excellent flow properties and were suitable for tableting.     

Lagoon PFA: Feasibility for use as a binder in concrete

This paper describes a study carried out to examine the influence of storing pulverized-fuel ash (PFA) in an excess of water, or lagoon, on the properties of the material itself and its suitability for use as a component of the binder in concrete. The work considered PFA slurried and stored in the laboratory (simulated lagoon PFA), and material recovered from power station lagoons (lagoon PFA). The results indicate that simulated lagoon PFA tends to agglomerate, and this appears to relate to chemical changes taking place within the material, as indicated by increasing loss-on-ignition, the formation of gypsum and bassanite, and leaching of solubles from particle surfaces into the simulated lagoon solution. Despite these effects, the use of this material, as part of the binder, has only a minor influence on concrete properties, with small changes in workability, bleeding and compressive strength measured. There was general agreement between the results for labortory and site lagoon PFA. If the effects noted are accommodated within the concrete mix design, there is potential for using lagoon PFA as a binder component in concrete construction.     

Electrochemical telomerase assay with ferrocenylnaphthalene diimide as a tetraplex DNA-specific binder

Spectroscopic studies revealed that ferrocenylnaphthalene diimide (1) can bind to tetraplex DNA at high potassium ion concentration. The tetraplex DNA was stabilized by the binding of 1, and this effect was larger than that of any other tetraplex stabilizers, which are known as a telomerase inhibitor. Quantitative analysis with circular dichroism and a quartz crystal microbalance strongly suggested a 3:1 binding stoichiometry of 1 to the tetraplex DNA. The telomere sequence could be extended by telomerase with the telomerase substrate primer on the surface of an electrode as proven by an increased current signal of 1 bound to the tetraplex DNA formed on the electrode. This is the first example of electrochemical detection of telomerase activity without relying on PCR.     

壳聚糖包覆二氧化硅纳米粒及其作为蛋白载体的研究

通过壳聚糖在二氧化硅纳米粒表面的沉积制备了壳聚糖包覆的二氧硅（CS@SiO2）。采用BSA作为模型蛋白,研究了CS@SiO2作为蛋白载体的可能性。结果表明,CS@SiO2可有效吸附BSA且可控释放被吸附的BSA。     

High-performance carbon composite electrode based on an ionic liquid as a binder

Ionic liquid, n-octylpyridinum hexafluorophosphate (OPFP) has been used to fabricate a new carbon composite electrode with very attractive electrochemical behavior. This type of carbon electrode has been constructed using graphite mixed with OPFP as the binder. The electrode has combined advantages of edge plane characteristics of carbon nanotubes and edge plane pyrolytic graphite electrodes together with the low cost of carbon paste electrodes and robustness of metallic electrodes. It provides a remarkable increase in the rate of electron transfer of different organic and inorganic electroactive compounds and offers a marked decrease in the overvoltage for biomolecules such as NADH, dopamine, and ascorbic acid. It also circumvents NADH surface fouling effects as well as furnishing higher current density for a wide range of compounds tested. Depending on the choice of the electrolyte, the electrode can have the ion-exchange property and adsorptive characteristics of clay-modified electrodes. The proposed electrode thus allows sensitive, low-potential, simple, low-cost, and stable electrochemical sensing of biomolecules and other electroactive compounds. Scanning electron microscopy images indicate significant improvement in the microstructure of the proposed electrode compared to carbon paste electrodes. Such abilities promote new opportunities for a wide range of electrochemical and biosensing applications.     

Surrogate functionality of celluloses as tablet excipients

Background: The variety of excipients from different sources and prices to which we have access gives rise to the necessity to evaluate their functional characteristics. The aim of this work is to determine some physical and technological characteristics of celluloses from different sources, India and United States, to ascertain their functionality as tablet excipients. Methods: The used surrogate functionality properties are particle morphology and particle size distribution, compactibility, ejection pressure, and the disintegration properties of pure excipients and their compressed tablets. Results: The innovators Avicel and Croscarmellose show advantages over the generic celluloses Alfacel and Carmacel. Avicel PH 101 and 102 show an average of 26% greater compactibility than both types of Alfacel, whereas the compactibility of Croscarmellose is greater than that of Carmacel in about 50%. Avicel tablets compacted at a compaction pressure of 47 MPa exhibit shorter disintegration times (3.7 minutes) than Alfacel tablets (28 minutes), whereas Carmacel show better disintegrant properties than Croscarmellose. This occurs regardless of the similar particle morphology, size, and size distribution. As expected, all celluloses show low ejection pressures. Conclusion: The surrogate functionality properties of the generic celluloses are still considered as satisfactory to be used as tablet excipients, although they are inferior in some aspects to innovator celluloses. Alfacel and Carmacel have the potential to be used as filler, binder, and disintegrant, in the design of tablets. Moreover, one should bear in mind that the differences reported here may be altered because of a possible inter-batch variability and variations in the moisture content.     

壳聚糖类缓蚀剂的研究进展

随着人们环保意识的增强,许多毒性大、生物降解差的缓蚀剂的使用受到了限制,壳聚糖是一种新兴的环境友好型材料,有作为缓蚀剂应用的潜质。综述了壳聚糖类缓蚀剂的研究状况,阐述了壳聚糖及其衍生物的缓蚀机理,提出目前壳聚糖缓蚀剂存在的问题,最后对壳聚糖缓蚀剂的发展趋势进行了展望,指出研究开发经济、高效、水溶性好的壳聚糖衍生物缓蚀剂具有重要的理论意义和实用价值。     

利用壳聚糖微球制备固定化乙酰胆碱酯酶

以壳聚糖微球(CS-MS)为载体,戊二醛(GA)为交联剂,制备固定化乙酰胆碱酯酶(AChE)。通过测定各种条件对酶活回收率影响,确定适宜的固定条件为:将1 g CS-MS用5 mL体积分数0.5%的GA活化0.25 h,然后加到含0.75 UAChE、pH 7.0~7.5的PBS中振荡反应24 h。所得到的酶活回收率可达81.94%,优于同类研究水平。红外光谱分析证实,AChE通过共价键和氢键结合到载体上。扫描电镜观察表明,经活化后CS-MS呈蜂窝状且表面平整光滑,利于酶的固定。因此,CS-MS是一种很有潜力的固定AChE载体。     

Chitosan as a polymer for pH-induced DNA capture in a totally aqueous system

A novel DNA solid-phase extraction protocol based on the pH-dependent charge of chitosan was developed specifically for low-volume DNA extraction on microchips. The method uses chitosan-coated beads to extract DNA at pH 5 and release it from the chitosan at pH 9. DNA extraction efficiency as high as 92% could be attained, even from complex samples such as human blood containing significant amounts of protein. Using this method, PCR inhibitors that are typically used in DNA extraction procedures (e.g., chaotropic salts, 2-propanol) can be avoided, making the method more conducive to downstream sample processing using PCR. A high-density multichannel microchip device was then fabricated and the microchannels coated with chitosan for DNA extraction in an open channel configuration without the need for an additional stationary phase. This design provided a relatively high surface area-to-volume ratio for extraction, while retaining the low flow resistance commensurate with open channels. With a flow rate of approximately 1 microL/min during the extraction, the total extraction time was less than 10 min, with most of the DNA recovered in the first 2 microL of elution buffer. Using the microchip device, extraction efficiencies for lambda-phage DNA and human genomic DNA were as high as 67 and 63%, respectively. Human genomic DNA from whole blood samples could be extracted in 10 min with an extraction efficiency of 75 +/- 4% (n = 3), and the purified DNA was suitable for PCR amplification of a fragment of the gelsolin gene. The combination of an entirely aqueous DNA extraction method with a high-density, low-flow resistance microchannel pattern sets the stage for future integration into microfluidic genomic analysis devices.     

Chitosan as a bioadhesive agent between porphyrins and phospholipids in a biomembrane model

Porphyrins are currently used in photodynamic therapy as photosensitizers. In this paper we studied the interaction of two charged porphyrins, 5, 10, 15, 20-mesotetrakis(N-metyl-4-pyridyl) porphyrin, (TMPyP/chloride salt) cationic, and 5, 10, 15, 20-meso-tetrakis(sulfonatophenyl) porphyrin, (TPPS4/sodium salt) anionic, nanoassembled in phospholipid Langmuir monolayers and Langmuir-Blodgett films. Furthermore, we used chitosan to mediate the interaction between the porphyrins and the model membrane, aiming to understand the role of the polysaccharide in a molecular level. The effect of the interaction of the photosensitizers on the fluidity of the lipid monolayer was investigated by using dilatational surface elasticity. We also used photoluminescence (PL) spectroscopy to identify the porphyrins adsorbed in the phospholipid films. We observed an expansion of the monolayer promoted by the adsorption of the porphyrins into the lipid-air interface which was more pronounced in the case of TMPyP, as a consequence of a strong electrostatic interaction with the anionic monolayer. The chitosan promoted a higher adsorption of the porphyrins on the phospholipid monolayers and enabled the porphyrin to stay in its monomeric form (as confirmed by PL spectroscopy), thus demonstrating that chitosan can be pointed out as a potential photosensitizer delivery system in photodynamic therapy.     

Bisphenol A based polyester binder as an effective interlaminar toughener

Bisphenol A based thermoplastic polyesters are commonly used in the industry as binders, or tackifiers, to produce cost-saving preforms in Liquid Composite Moulding processes such as Vacuum Assisted Resin Transfer Moulding (VARTM). However, it is often reported that the presence of these polyesters has a detrimental effect on the mechanical properties of the resulting composite laminates. In contrast, this study shows that interlaminar toughness can be increased without negatively affecting other properties by coating the reinforcing plies with a bisphenol A based thermoplastic polyester if some precautions are taken in mind.The polyester was added to an epoxy resin in order to study its effect on the thermophysical properties and fracture toughness of the bulk epoxy. The polyester molecules acted as a plasticizer for the epoxy resin when the polyester was added in low amounts. This increased the bulk fracture toughness of the epoxy resin by 30%. Polyester modified glass/epoxy laminates were produced and tested for Mode I interlaminar fracture toughness and flexural properties. The increased toughness of the epoxy matrix led to a 60% increased Mode I interlaminar fracture toughness of the laminates, without negatively affecting flexural stiffness and strength of the laminates.     

Modified polyester resins as an effective binder for polymer concretes

Polymer concretes (PCs) are extensively used in the construction industry. Unsaturated polyester resins are amongst the most important binders in PCs. In this research a new kind of enhanced polyester resin, as the binder for PCs is presented. In order to assess the performance of PCs built with this new resin, samples of concrete comprising ordinary polyester resin and the enhanced polyester resin were prepared and examined in physical/mechanical tests. So as to evaluate the functionally of these products chemical strength tests in the presence of sulfuric acid with the pH of 1 were performed. The results suggested that physical/mechanical properties of the PCs were very similar. Moreover, the resin modification considerably enhances durability and long term chemical performance. Hence, application of the new resin in aggressive environments, specifically in coastal areas and sewage systems prone to sulfuric acid and sulfate attack, is recommended.     

The use of natural rubber latex as a renewable and sustainable modifier of asphalt binder

Natural rubber (NR) powder as a bio-modifier of asphalt binder has been shown to have some beneficial effects. However, there is limited research into the use of the liquid form of NR, i.e. concentrated NR latex, as an asphalt binder modifier. Compared to NR powder, NR latex is cheaper and more accessible in some countries, and potentially creates viscosity-reducing foams in the modified binder during mixture production. In this research, asphalt binders modified with different amount of NR latex were systematically studied, including the rotational viscosities, rutting resistance, fatigue resistance, low-temperature behaviour and temperature sensitivity. The dispersion of the NR latex in the modified binders was examined using fluorescence microscope and atomic force microscope. Test results indicate that the addition of NR latex increases the viscosity and elastic recovery of the modified binders and potentially enhances asphalt pavements’ resistance to rutting, thermal cracking and fatigue damage. The NR latex also reduces the temperature sensitivity of the modified binders. The optimum NR latex content was found to be 7% of the total mass of the modified binder. A network of extensive microstructures mixed with bubbles was identified in the modified binders under heat. As a renewable and sustainable material, NR latex has the potential to be used as an effective asphalt modifier.