Liposome characterization most popular for drug de

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Characterization of liposomes for drug delivery system Pauline Carnell, a senior applied scientist of Malvern instruments, and Mike kazsuba, a technical support manager, discussed the application and effect of nanoparticle tracking and analysis technology and light scattering technology in characterizing liposomes as drug carriers

liposome is an important drug delivery carrier, which has been approved for a variety of therapeutic formulations. Liposomes are composed of phospholipids, with single-layer or multi-layer structure, hydrophilic inner layer and hydrophobic outer layer, which can be made into particles of different sizes. These particles are biodegradable and basically non-toxic. Most importantly, it can encapsulate both hydrophilic and hydrophobic substances. In addition, by modifying the surface of liposomes, targeted drug delivery can be carried out to specific physiological sites, which can prolong the retention time of liposomes in vivo, and can be used to design diagnostic tools

as in other similar studies, the key to the application of liposomes is to ensure that their physical properties are consistent with their uses. For example, how will liposomes react after entering the human body? Are liposomes stable enough to ensure targeting? Is the particle size suitable for clinical application, or will it disappear in the blood circulation

understanding the continuous driving force of future mass production and expansion of production one by one constitutes the company's deeds. The particle size, concentration and zeta potential of liposome preparation can help people predict its change trend in organisms, and the molecular relationship between charged liposomes and opposite electricity can also be monitored by measuring the zeta potential of polymers produced by both. These factors have a significant impact on the effectiveness of drug delivery, especially when drug formulation researchers believe that a certain liposome is suitable for the delivery carrier, the above factors should be considered comprehensively. Therefore, an analysis system that can provide comprehensive data is of great benefit to the formulation design process. Nanoparticle tracking analysis technology and dynamic light scattering technology are two important analysis methods, which provide important information for liposome research

nanoparticle tracking and analysis technology

nanoparticle tracking and Analysis Technology (NTA) uses laser scattering to test the nanoparticle size in solution (Figure 1). Using this analysis method, researchers can observe a single particle and track its Brownian motion trajectory, so as to quickly produce the particle size distribution map of each particle based on a single particle in a short time

Figure 1 effect display of nano particle tracking analysis technology

the scattered light of particles in solution can be captured by using scientific digital camera, and the instrument software can track the motion trajectory of each particle frame by frame (Figure 2)

the light spot in Figure 2 is a particle in Brownian motion

the velocity of the particle is related to the equivalent hydrodynamic radius of the sphere calculated by Stokes Einstein equation (Figure 3). NTA technology can calculate the granularity grain by grain, and because of the image segment as the analysis basis, users can accurately characterize the real-time dynamics

Figure 3 Stokes Einstein equation

nta technology allows researchers to observe single nanoparticles at the same time. Therefore, in addition to the basic particle size analysis, it can also measure the relative light scattering intensity of each liposome. Drawing the data results and the separately measured particle size data into a coordinate diagram can more carefully distinguish the particles composed of different refractive index (RI) or materials. With this unique function, researchers can explore whether the contents encapsulated by nanoscale drug delivery carriers (such as liposomes) are different: the refractive index (light scattering ability) of hollow liposomes may be lower than that of liposomes containing substances with higher refractive index. Such differences allow people to distinguish between liposomes of similar size. In addition, NTA's single particle detection system makes particle concentration measurement possible

particle size and zeta potential

the position where liposomes interact with cells in vivo is largely determined by the particle size of liposomes. Mastering the zeta potential of liposomes is helpful to predict the change trend of liposomes in vivo. Zeta potential of particles refers to the total charge obtained by particles in a specific medium. Taking gene therapy as an example, the measurement of zeta potential can be used to optimize the ratio of specific liposomes to various DNA plasmids, so as to minimize the aggregation of the formula (Fig. 4)

Figure 4 complexing of cationic liposomes (positively charged) with DNA (plasmids)

dynamic light scattering (DLS) is a relatively mature and widely used liposome characterization technology. In addition, because zeta potential is also an important parameter, the analysis system that can measure particle size and zeta potential at the same time is becoming more and more popular, and the Zetasizer nano system of Malvern instruments is one of them. Generally speaking, researchers use dynamic light scattering technology to measure particle size, and laser Doppler micro electrophoresis technology to measure zeta potential

light scattering caused by Brownian motion of particles is also the core of DLS technology with excessive viscosity of oil. DLS technology measures the fluctuation of scattered light intensity with time, and determines the diffusion coefficient of particles. On this basis, Stokes Einstein equation is used to transform the data into particle size distribution

when zeta potential is measured by laser Doppler micro electrophoresis, when an electric field is applied to molecular solution or particle dispersion, these particles will move at a certain rate, which is positively related to Zeta potential. By measuring this rate, the electrophoretic mobility can be calculated, and the zeta potential and zeta potential distribution of particles can be calculated


the physical characterization of liposomes is very important for understanding the applicability of liposomes in various applications. Rapid and repeatable characterization is an important consideration in the process of R & D and quality control. The technology introduced in this paper can provide supplementary information about the particle size, concentration and zeta potential of liposomes

the second constant temperature field can be established Note: the reprinted content is indicated with the source. The reprint is for the purpose of transmitting more information, and does not mean to agree with its views or confirm the authenticity of its content

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