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Basic Concepts of Acid–Base Physiology
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Several buffers are present in ECF and intracellular fluid (ICF). The effectiveness and capacity of a buffer system are determined by the amount of buffer present, its pKa, the pH of the solution and whether the buffer functions as an open (physiological) system or a closed (completely chemical) system. Approximately 80% of buffering occurs within ±1 pH unit of the pKa of the buffer system. The major buffer systems in the body are bicarbonate, haemoglobin, protein and phosphate.
Cellular Grafting Techniques
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
Phosphate-buffered saline (PBS) is a buffer solution commonly used in biological research. The osmolarity and ion concentrations of the solution usually match those of the human body (isotonic), and it is nontoxic to cells. With this, the cost of the procedure can be reduced since there is no need for melanocyte media and there are no concerns of mitogenesis due to the melanocyte medium [22].
The renal system, hypertension and pre-eclampsia
Published in Judy Bothamley, Maureen Boyle, Medical Conditions Affecting Pregnancy and Childbirth, 2020
Chronic renal failure is progressive and irreversible damage to about 75% of nephrons. The kidneys exhibit remarkable adaptive abilities and so the onset of symptoms is slow. The main causes are glomerulonephritis, diabetes, reflux nephropathy and hypertension. There is reduced glomerular filtration, which leads to a build up of urea and creatinine in the blood. A large quantity of urine is produced as reabsorption of water is impaired. Acidosis occurs as the kidney buffer system that normally maintains pH fails. An imbalance of sodium and potassium occurs. Hypertension can be a cause and a result of renal failure (Huether, 2006; Macfarlane, et al., 2000; Waugh and Grant, 2006).
Exploring microfluidics and membrane extrusion for the formulation of temozolomide-loaded liposomes: investigating the effect of formulation and process variables
Published in Journal of Liposome Research, 2023
Tejashree Waghule, Ranendra Narayan Saha, Gautam Singhvi
A weighed quantity of phospholipid and cholesterol were dissolved in 4 ml of chloroform and methanol mixture (2:1). The organic solvent was evaporated using the Buchi Rotary Evaporator R210. The temperature of the water bath was kept 5–10 °C above the phase transition temperature (PTT) of the phospholipid (DSPC:55 °C, DPPC:41 °C, and DMPC:23 °C). The formed film was kept for drying overnight and hydrated with TMZ (1 mg/mL) containing acetate buffer (pH 4.5). The buffer was used to ensure the stability of the drug during formulation. This was further bath sonicated for 10 min to ensure complete hydration of the film and formation of a dispersion. The formed liposomal dispersion was extruded through a membrane extruder (Avanti® Mini-extruder) using a 0.1 µm polycarbonate filter to obtain a homogenous liposomal dispersion. The extrusion was done at 5–10 °C above the phase transition temperature of the phospholipid. The effect of the number of extrusion cycles on particle size and entrapment efficiency was investigated. Also, the effect of various formulation variables like type of phospholipid (DSPC, DPPC, DMPC), phospholipid to cholesterol ratio, and phospholipid to drug ratio was investigated (Gim et al.2016, Shukla et al.2019).
A drift on liposomes to proliposomes: recent advances and promising approaches
Published in Journal of Liposome Research, 2022
Neha Dhiman, Jayrajsinh Sarvaiya, Poorti Mohindroo
The in vitro dissolution of proliposomes can be carried out by filling them into a capsule or compressing them into a tablet using the United States Pharmacopoeial type-I or II apparatus (or as described in Pharmacopoeia). In vitro drug release study of PLs is conducted to predict the dissolution profile of the drug in physiologically discriminating dissolution media. It provides a complete understanding of the release kinetics of the formulation under the physiological condition of our body (Nekkanti et al.2015). Normally the buffer solution with the physiological pH ranging from 7.4 to 7.6 was selected and the temperature adjusted to 37 °C (Patel and Patel 2020). Moreover, a new approach called dialysis was also investigated to study the drug release profile. In this method, liposomes are filled in a dialysis tube, immersed in an aqueous solution, and kept stirring for 24 h at 37 °C. Samples will then be taken after sufficient time intervals and assessed quantitatively through HPLC (Omer et al.2018).
Pirfenidone as a potential antifibrotic injectable for Dupuytren’s disease
Published in Pharmaceutical Development and Technology, 2022
Suchitra Panigrahi, Amanda Barry, Scott Multner, Gerald B. Kasting, Julio A. Landero Figueroa, Latha Satish, Harshita Kumari
SC injection doses usually have small volumes; hence, we aimed to use an injection volume of 0.4 mL for safety studies in animals, which is within the generally accepted range (≤1.5 mL). The clear homogenous solution could lead to pain at the injection site if factors, such as the tonicity, pH, buffer type, and viscosity are not controlled during formulation. As the PFD solution was prepared in an aqueous medium, the viscosity was not investigated. Benzyl alcohol was added as a preservative to prevent the growth of microorganisms (typically in multidose injections). Benzyl alcohol is considered safe up to 2% w/v for small-molecule injectable formulations (Usach et al. 2019) and has been used in many approved injectable preparations (U.S. Food and Drug Administration). Buffers are added to maintain the pH of the overall formulation close to physiological pH. Most buffering agents in injectable products are used at concentrations of 10–100 mM (Usach et al. 2019) depending on the amount of active ingredient in the final product. Citric acid, which is commonly used as a buffer in approved parenteral products (Nash et al. 2016), induced more pain than other buffers. Therefore, phosphate, which is the second most common buffering agent, was used at the recommended concentration to maintain the pH of the prepared formulation close to physiological pH during storage (pH of the formulation without buffer observed to be ∼5).