Basic Injection Techniques
Yates Yen-Yu Chao, Sebastian Cotofana, Anand V Chytra, Nicholas Moellhoff, Zeenit Sheikh in Adapting Dermal Fillers in Clinical Practice, 2022
Soft tissue fillers intended to be placed superficially in the subdermal fatty layer should be thin, soft, small in particle, or have the character to be integrated well with tissues. Except for soft gel hyaluronic acid (HA) fillers and small particle HA products, poly-L-lactic acid (PLLA) with modified techniques (see Chapter 4) can be applied in a very superficial subdermal pattern. The subdermal depot technique is usually indicated for a shallow depression scar, the correction of minor unevenness, or the gentle enhancement of contours. Depots injected into superficial fat compartments can accentuate facial shapes more efficiently than deep-seated depots; however, volume replacement by fillers should be tailored according to pathognomonic reasons. When the actual lack or loss of volume derives from the bony structures or the deep fat tissue, the new volume is ideally to be placed in deeper layers. When the loss or deficiency is originated from deep but fillers are put superficially, the superficially placed foreign substance can be expected to be more visible and volume efficient. It can even appear normal in static mode but can move awkwardly with the contraction of underlying mimetic muscles. A superficially situated pool of HA without adequate tissue integration can be grouped or present with prominent margins. The light could transmit and be scattered from part of the pool, resulting in an embarrassing transparent appearance or bluish discoloration (colloid light scattering, more often referred to as the Tyndall effect).
Liposomes
Danilo D. Lasic in LIPOSOMES in GENE DELIVERY, 2019
The stability of colloidal systems is an important factor in their applications. Although no general model exists, the DLVO model can quantitatively explain stability of many charged systems. Briefly, it states that if electrostatic repulsion between two particles is larger than van der Waals attraction, the system is stable. With respect to the charge and ionic strength of the medium various force-distance profiles can be calculated and observed in many lyophobic colloids. We shall describe these forces for a homogeneous liposome or genosome suspension with diameter 2R, surface charge σo, at temperature T, and in zi−zj, electrolyte solution at concentration (number density) ρ. The ubiquitous attractive force between liposomes is van der Waals attraction, while the long-range repulsive force is electrostatic repulsion. The balance between the two determines colloidal stability. Using the Poisson–Boltzmann equation to calculate electrostatic interaction potential and nonretarded van der Waals interaction by Hamaker summation method over atom–atom pair potential for spherical geometry, one determines the interaction energy between two particles at a separation D:
Red Blood Cell and Platelet Mechanics
Michel R. Labrosse in Cardiovascular Mechanics, 2018
Colloids are small enough that they exhibit significant Brownian motion, that is, random position fluctuations induced by the thermal energy of the surrounding fluid. Accordingly, any colloid will, in the course of time, explore the entire space that is made available to it. The more the space available, the more favorable the situation for the colloids. Accordingly, a system with many colloids will always attempt to arrange itself in such a way that the colloids have the largest possible space available. Thermodynamically speaking, the system maximizes its entropy. This behavior has dramatic consequences if one considers a mixture of large and small colloids. As illustrated in Figure 8.10a, each large colloid is surrounded by a small volume into which the small colloids cannot fully penetrate. Taking its center of mass as the position of a small colloid, the small colloid cannot approach the large one closer than half of its diameter. This forbidden area reduces the space available for the Brownian motion of the small colloids. As reasoned previously, in order to maximize its entropy, the system will strive to attain a configuration in which the total forbidden area (summed over all large colloids) is minimal. This is clearly achieved if the large colloids touch as much as possible, such that their respective forbidden areas overlap. If many small colloids surround a relatively small number of large colloids, the resulting entropic force driving aggregation of the large colloids can be considerable.
Blueprint for antibody biologics developability
Published in mAbs, 2023
Carl Mieczkowski, Xuejin Zhang, Dana Lee, Khanh Nguyen, Wei Lv, Yanling Wang, Yue Zhang, Jackie Way, Jean-Michel Gries
Developability of antibody and protein therapeutics is a critical activity to drive and advance the optimization and selection of lead candidates into IND enabling and clinical studies. Proper and thorough developability studies not only examine potential CQAs that will represent the fitness of the process and drug product, but also elucidate the molecular properties that may affect post-administration safety and efficacy and ultimately clinical success. Recent advances in in silico computational approaches and the evaluation of non-specificity have also helped to streamline and enable more informative developability assessments. We propose these four major properties of large-molecule antibody and protein therapeutics as those that affect all developability outcomes: 1) conformational, 2) colloidal, 3) chemical, and 4) other interactions. A complete examination of these properties and their risks during discovery-stage developability and early development activities offers the best likelihood that robust and quality lead candidates are promoted and potential CMC and clinical development risks are manageable.
Preparation and characterisation of self-emulsifying drug delivery system (SEDDS) for enhancing oral bioavailability of metformin hydrochloride using hydrophobic ion pairing complexation
Published in Journal of Microencapsulation, 2023
Seyedeh Nika Rezvanjou, Mohammad Reza Niavand, Omid Heydari Shayesteh, Ehsan Mehrani Yeganeh, Davood Ahmadi Moghadam, Katayoun Derakhshandeh, Reza Mahjub
The Zeta potential of particles refers to the electrical charge at the double layer surrounding a dispersed nano-structure. It is considered as an important indicator of the stability in colloidal dispersions. Generally, emulsions are more stable at high zeta potential values (± 30 mV) due to the electrostatic repulsion forces between the charged particles, while emulsions with low zeta potential are not stable and tend to coagulate or flocculate (Honary and Zahir 2013, Cherniakov et al.2015). In this study, the optimised SEDDS formulation showed a slightly negative charge. Thus, probable flocculation seems to be happening. However, SEDDS formulation is administered orally as a prototype formulation, and formation of self-dispersions would occur simultaneously upon exposure of prototypes to gastrointestinal fluid. Therefore, the low value for the zeta potential is not of crucial importance (Mahmoudian et al.2020). Moreover, due to the high negative charge density of the intestinal mucus layer, preparation of slight negatively charged nano-droplets may reduce the electrostatic repulsion between the nano-droplets and the intestinal epithelium and therefore leads to an increase in permeation (Asfour et al.2020).
Development of nanocubosomes co-loaded with dual anticancer agents curcumin and temozolomide for effective colon cancer therapy
Published in Drug Delivery, 2022
Yosif Almoshari, Haroon Iqbal, Anam Razzaq, Khalil Ali Ahmad, Muhammad Khalid Khan, Saad Saeed Alqahtani, Muhammad H. Sultan, Barkat Ali Khan
The colloidal or dispersion stability is a vital parameter, as nanoscale sized particles dispersed in physiological medium have high proclivity to agglomerate, and the formed of bigger aggregates. So, the colloidal stability of CTNCs were evaluated upto 120 h (5 days) stored at 4 ◦C in different physiological medium, i.e. PBS (pH 7.4), Dist. water, DMEM, NaCl (0.9%) and glucose (5.0%) by measuring the hydrodynamic diameter at specified time periods. The obtained results revealed that no visible change was observed in average hydrodynamic diameter of CTNCs after incubating with different physiological over a period of 120 h at 4 °C, depicted in Figure 3B. The enhanced colloidal stability of CTNCs in dispersions might be due to the charged surface of albumin which induce high repulsive forces among nanocubosomes in dispersion (Li et al., 2021). These strong repulsive interactions prevent the nanocubosomes coming too closely in contact to each other. So, in such environment the coagulation of nanocubosomes hardly occurs.
Related Knowledge Centers
- Aerosol
- Dispersion
- Opacity
- Silica Gel
- Mixture
- Suspension
- Gel
- Tyndall Effect
- Scattering
- Interface & Colloid Science