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Dictionary
Published in Mario P. Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Colloid. An intimate mixture of two substances, one of which, called the dispersed phase (or colloid), is uniformly distributed in a finely divided state through the second substance, called the dispersion medium (or dispersing medium), The dispersion medium may be a gas, a liquid, or a solid, and the dispersed phase may also be of these, with the exception that one does not speak of a colloidal system of one gas in another. Also called colloidal dispersion, colloidal suspension.
Nanosuspensions as Nanomedicine: Current Status and Future Prospects
Published in Debarshi Kar Mahapatra, Sanjay Kumar Bharti, Medicinal Chemistry with Pharmaceutical Product Development, 2019
Shobha Ubgade, Vaishali Kilor, Abhay Ittadwar, Alok Ubgade
Nanosuspensions have emerged as a promising strategy for the efficient delivery of poorly soluble drugs because of versatile features. In the current scenario, one of the biggest challenges in drug development is to improve the solubility characteristics for the attainment of desired bioavailability of drugs. Several strategies have been employed to overcome these limitations. Particle size reduction has been a smarter approach that can be applied to the nonspecific formulation for many years. Diminution of particle size to sub-micron range is a powerful formulation approach that can increase the dissolution rate, and the saturation solubility, subsequently improves the bioavailability of poorly water-soluble drugs. Drug nanocrystals are considered as a novel approach to improve the solubility of hydrophobic drugs since the technique is simple and effective which can quickly launch product to the market. The nanocrystals were invented at the beginning of the 1990s and the first products appeared very fast on the market from the year 2000 onwards. Additionally, drug nanocrystals are a universal approach generally applied to all poorly soluble drugs for the reason that all drugs can be disintegrated into nanometer-sized particles [13]. Drug nanocrystals are nanoscopic crystals of parent compounds with the dimension of less than 1 mm. They are composed of 100% drug without carriers and typically stabilized with surfactants or polymeric steric stabilizers. A dispersion of drug nanocrystals in an outer liquid medium and stabilized by surface active agents are so-called nanosuspensions. The dispersion medium can be water, aqueous or nonaqueous media, for example, liquid polyethylene glycol (PEG) and oils. The nanosuspensions can be used to formulate compounds that are insoluble in both water and oil and to reformulate existing drugs to remove the toxic less favorable excipients [14–16].
Granulation of Poorly Water-Soluble Drugs
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
Albert W. Brzeczko, Firas El Saleh, Hibreniguss Terefe
Nanoparticles for pharmaceutical applications are produced by two basic methods, comminution or a “top-down” method and precipitation or a “bottom-up” method. Within the comminution method are two primary particle size reduction techniques, bead milling and homogenization. The NanoCrystal® technology for nanoparticle formation is based on the bead milling process. Bead mills are favorable because they are less expensive, relatively simple to use, available at a small R&D scale, and readily scalable for commercialization. Milling media (beads), the dispersion medium, drugs, and other formulation aids (stabilizers) are charged into the milling chamber. Wet milling is essential to achieve smaller nanoparticle sizes when compared with dry bead milling processing. The dispersion medium would ideally be a non-solvent for the drug. For poorly soluble drugs, water often serves as the dispersion medium. Surfactants and stabilizers are essential in the production of nanoparticles by nanosuspensions. The choice of surfactant is dependent on the affinity of the surfactant for the drug surface and the physical nature of the interaction (i.e., steric or electrostatic). Generally, steric stabilization on nanoparticles is preferred. In some cases, a combination of low- and high-hydrophilic‐lipophilic balance surfactants may be warranted. Milling media are available in a variety of materials, but to minimize contamination, yttria zirconium beads offer nearly contamination-free grinding [16]. The extent of bead erosion depends on milling material, suspension concentration, drug hardness, and milling time. Impact and shearing forces between the milling media and the suspended drug particles are responsible for particle reduction. Smaller milling media with a higher number of contact points are preferred to produce smaller nanoparticles. As a general rule, the size of the milling media is 1000 times the size of the desired nanoparticle size. Plug flow, where particles move at a uniform velocity in the mill, is preferred to achieve a consistent and reproducible grind and residence time. Milling times can be highly variable and are largely dependent on drug hardness, dispersion media, milling energy, surfactant and level used, temperature, and type and size of milling media. The wet suspension from bead mill processing can be dried for oral solid dosage manufacturing or the suspension can be used for delivery as a drug suspension.
Vascular toxicity of multi-walled carbon nanotubes targeting vascular endothelial growth factor
Published in Nanotoxicology, 2022
Xiao-yu Dai, Li-jun Ren, Lang Yan, Ji-qian-zhu Zhang, Yi-fan Dong, Tao-lin Qing, Wen-jing Shi, Jin-feng Li, Fang-yuan Gao, Xiao-fang Zhang, Yi-jun Tian, Yu-ping Zhu, Jiang-bo Zhu, Ji-kuai Chen
The MWCNTs used in this study were obtained from Cheap Tubes Inc. (Cambridgeport, VT) (20–30 nm: 030104; 30–50 nm: 030106). The physical and chemical properties of MWCNTs are shown in Table 1 which was provided by Cheap Tubes Inc. Dispersion medium was used to disperse MWCNTs. Dispersion medium containing phosphate-buffered saline (PBS) and 150 μg/mL curosurf (Chiesi Farmaceutici, Prama, Italy) was freshly prepared before being used to suspend MWCNTs or to serve as vehicle control. MWCNTs were dispersed in dispersion medium via sonication procedure immediately before use. Dispersion medium effectively disperses MWCNTs as shown by transmission electron microscopy (Huang et al. 2020). The diameter of MWCNTs were measured using a scanning electron microscope (SEM, Hitachi, Tokyo, Japan). The Zeta potential measurements were performed using a Malvern Zetasizer Nano ZS90 analyzer.
Comparison of media milling and microfluidization methods for engineering of nanocrystals: a case study
Published in Drug Development and Industrial Pharmacy, 2020
Manasi Chogale, Sandip Gite, Vandana Patravale
Media milling involves particle size diminution of a dispersion of a drug having a suitable surfactant in a dispersion medium (usually purified water) using a milling media (beads or pearls). The dispersion medium should be a non-solvent for the drug undergoing size reduction. The shear force of impact generated by the movement of the milling media leads to particle size reduction. The beads or balls are usually composed of cerium- or yttrium-stabilized zirconium dioxide and are available in a range of sizes [9]. Zirconium beads have replaced the traditionally used stainless steel beads owing to their advantages including high hardness, high toughness, high density, good abrasion resistance, heat-resistance, corrosion-resistance, high stiffness, non-magnetic, and electrical isolation. These beads are also endowed with high grinding efficiency, good fluidity, impact resistance, and low using cost. Customarily, larger beads are used for coarse grinding bringing down the particle size to a few microns while the smaller beads are used for fine milling thereby yielding nanocrystals. The efficacy of this technology is dependent on numerous factors such as surfactant concentration, the hardness of the drug, viscosity of the dispersion, temperature, energy input, size of milling media, time of milling, and speed of the milling chamber [10]. This is an important particle size reduction technology and is already included in the manufacturing process of numerous FDA approved products [4].
Co-delivery of a RanGTP inhibitory peptide and doxorubicin using dual-loaded liposomal carriers to combat chemotherapeutic resistance in breast cancer cells
Published in Expert Opinion on Drug Delivery, 2020
Yusuf Haggag, Bayan Abu Ras, Yahia El-Tanani, Murtaza M. Tambuwala, Paul McCarron, Mohammed Isreb, Mohamed El-Tanani
The physicochemical characteristics of three different peptide-loaded liposome formulations (F1, F2, and F3) are shown in (Table 2). NT 3–12 peptide was dissolved in aqueous dispersion media with each adjusted to one of the following pH values (PBS pH 7.4, phosphate buffer pH 6.8, and phosphate buffer pH 6) to investigate the effect of the pH value on the physicochemical properties of the peptide-loaded liposomes. Decreasing the pH of the aqueous dispersion medium resulted in a significant increase in liposomal size. The average size of (F1) rehydrated by phosphate buffer (pH 6) was found to be 139 ± 21 which was significantly bigger (p ˂ 0.01) compared to 81 ± 11 nm in the case of (F3) prepared at higher pH of 7.4. Low pH values cause the protonation of the phospholipid heads and therefore hydrogen bond formation may occur resulting in bigger liposomal size meanwhile some phospholipid may exhibit electrostatic repulsion between protonated phospholipid heads. In the case of DPPG, protonation of phospholipid heads was more likely to occur compared to other lipids so that hydrogen bond formation between adjacent protonated heads predominate the electrostatic repulsion resulting in larger liposome size [48,49]. The change in pH value of the dispersion medium showed a slight change in zeta potential (p ˃ 0.05). This might be attributed to the poor electrostatic repulsion effect resulted from the change in pH values.