Nanoprecipitation technique

Biocompatible and biodegradable PLG nanoparticles (80-150 nm) have been prepared by following the nanoprecipitation technique [33]. The nanoparticles were coated with a 5-10 nm thick layer of PPO-PEO block copolymer or with tetrafunctional (PEO-PPO)2N-CH2-CH2-N(PPO-PEO)2 [33]. Such coats are bound to the core of the nanosphere by hydrophobic interactions of the PPO chains, while the PEO chains protrude into the surrounding medium and form... 

Amphiphilic CDs yield nanoparticles spontaneously in the form of nanospheres or nanocapsules depending on the preparation technique. Nanoparticles have been manufactured using three different techniques. However, the nanoprecipitation technique is generally preferred since it is a simple technique resulting in unimodal distribution. The general preparation techniques for amphiphilic CD nanoparticles are as follows ... 

D. Chan-Seng, M. K. Georges, Living radical emulsion polymerization using the nanoprecipitation technique an extension to atom transfer radical polymerization, J. Polym. Sci., Part A Polym. Chem. 2006, 44, 4027-4038. 

Narayanan et al. reported targeted NP-mediated delivery to enhance the efficacy of the well-known nutraceutical GSE. NanoGSE was prepared by a nanoprecipitation technique whereby GSE was encapsulated in PLGA nanoparticles. The potential cancer-targeting ligand folic acid was conjugated to GSE-PLGA NPs and tested... 

The key objective of this chapter is to provide comprehensive information about the nanoprecipitation method to form polymeric nanoparticles. It provides crucial factors, such as the type of components used and processing conditions (e.g., addition rate of various components and mixing time) that are involved in nanoprecipitation. The chapter comprises a brief discussion on the parameters affecting the size of the nanoparticles and the mechanism of nanoparticle formations. Additionally, the different semps used to mix the phases and the recent advancements in the manufacturing techniques are discussed. Finally, the biomedical applications of the nanoprecipitation technique are conversed. 

The method of preparation of nanoparticles via nanoprecipitation is experimentally well-known, but the mechanisms responsible for the formation of nanoparticles are not yet fuUy known, which need to be addressed [7]. Knowledge of the mechanisms that control the nanoprecipitation process can be useful. It can help us to understand how various controlling parameters, such as molar masses, concentration of polymer, surfactants, and mixing rates, affect the final particle size. This knowledge will help to develop an effective nanoprecipitation technique. There are two proposed mechanisms, which are supposed to be consistent with the experimental results mechanical mechanism and classical nucleation mechanism. Both of these mechanisms abide by the fact that the formation of particles takes place in the metastable region of the phase diagram, i.e., between the binodal and spinodal curve [31]. 

Nanoparticles are able to cross the Reticuloendothelial system (RES) due to their stealth characteristic that enhances the Enhanced Permeability and Retention (EPR) effect. An increased EPR aids in treating cancers and tumors. The nanocarriers produced by the nanoprecipitation technique had PACA core, stealth... 

The procedure chosen for the preparation of lipid complexes of AmB was nanoprecipitation. This procedure has been developed in our laboratory for a number of years and can be applied to the formulation of a number of different colloidal systems liposomes, microemulsions, polymeric nanoparticles (nanospheres and nanocapsules), complexes, and pure drug particles (14-16). Briefly, the substances of interest are dissolved in a solvent A and this solution is poured into a nonsolvent B of the substance that is miscible with the solvent A. As the solvent diffuses, the dissolved material is stranded as small particles, typically 100 to 400 nm in diameter. The solvent is usually an alcohol, acetone, or tetrahydrofuran and the nonsolvent A is usually water or aqueous buffer, with or without a hydrophilic surfactant to improve colloid stability after formation. Solvent A can be removed by evaporation under vacuum, which can also be used to concentrate the suspension. The concentration of the substance of interest in the organic solvent and the proportions of the two solvents are the main parameters influencing the final size of the particles. For liposomes, this method is similar to the ethanol injection technique proposed by Batzii and Korn in 1973 (17), which is however limited to 40 mM of lipids in ethanol and 10% of ethanol in final aqueous suspension. 

This technique, based on the precipitation of a hydrophobic polymer, is useful for the encapsulation of either hydrophilic or hydrophobic drugs because a variety of solvents, including polar (e.g., acetone or methanol) and non-polar (methylene chloride or chloroform) solvents can be chosen for dissolving the drug. This procedure is just like nanoprecipitation, however, the miscibility of both phases is prevented by the saturation of the external aqueous phase with PVA. Precipitation occurs when a sufficient amount of water is added to allow complete diffusion of the acetone into the aqueous phase. 

Bilati, U., Allemann, E., and Doelker, E. (2005), Nanoprecipitation versus emulsion-based techniques for the encapsulation of proteins into biodegradable nanoparticles and process-related stability issues, AAPS Pharm. Sci. Tech., 6,74. 

This method, also known as the nanoprecipitation method, can be applied to numerous synthetic poly-mers. ° In general, the polymer is dissolved in acetone and the polymer solution is added into water. The acetone is then evaporated to complete the formation of the particles. Surface active agents are usually added to water to ensure the stability of the polymer particles. This easy technique of nanoparticle preparation was scaled up for large batch production. It leads to the formation of nanospheres. Nanocapsules can easily be prepared by the same method just by adding a small amount of an organic oil in the polymer solution.When the polymer solution is poured into the water phase, the oil is dispersed as tiny droplets in the solvent-non-solvent mixture and the polymer precipitates on the oil droplet surface. This method leads to the preparation of oil-containing nanocapsules... 

Nanoprecipitation is another technique to obtain nano-sized polymer particles. An organic polymer solution is rapidly given to a nonsolvent (typically water), and nanoparticles are generated during precipitation of the polymer at the interfaces. The process depends critical on all components, and surfactant can be added to further control nanoparticle size. In this way one can produce polymer nanoparticles at large scale to be used in biomedical, biotechnological, or environmental applications. Also here the chapter of the book describes further details. 

One of the important parameters associated with the solvent is its dielectric constant. The diff erence in the dielectric constants between the solvent and the non-solvent affects the efficiency of nanoprecipitation. If the difference is very high, nanoprecipitation may fail. It has been seen that smaller nanoparticles are formed when dielectric constant of the solvent is high [25]. Nanoprecipitation depends on various phenomena that affect the diffusion of the solvents, in addition to the dielectric constant. Hence, the effectiveness of the technique is dependent on combined properties of the solvent and the non-solvent, such as their solubility values and volumes ratios [12] (which will be discussed in Section Controlling Nanoparticle Size ). 

Different methods of mixing are employed to mix the organic phase with the aqueous phase, which will be discussed in Section Manufacturing Techniques Used in Nanoprecipitation . The technique used to mix the phases could also have an effect on the nanoparticle size. Nanoprecipitation is a non-equilibrium process, which initiates with the mixing of the two phases, which suggests that the variation in the particle size can be obtained by change in mixing methods. Nanoparticle size... 

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