M Subbu Chemical Engineering Book Pdf Free 393
Cre Wallace
Dr. M. Subramanian, the founder of MSubbu Academy has 20+ years of experience in teaching and the author of seven most sought-after books. He is a passionate chemical engineering professional. He is stuffed with two years of experience in chemical industry along with five years of research experience. His knowledge and experience base help fellow chemical engineers to explore their domain with a broad approach.
Cell-encapsulating hydrogels used in regenerative medicine are designed to undergo a rapid liquid-to-solid phase transition in the presence of cells and tissues so as to maximize crosslinking and minimize cell toxicity. Light-activated free-radical crosslinking (photopolymerization) is of particular interest in this regard because it can provide rapid reaction rates that result in uniform hydrogel properties with excellent temporal and spatial control features. Among the many initiator systems available for photopolymerization, only a few have been identified as suitable for cell-based hydrogel formation owing to their water solubility, crosslinking properties and non-toxic reaction conditions. In this study, three long-wave ultraviolet (UV) light-activtied photoinitiators (PIs) were comparatively tested in terms of cytotoxicity, crosslinking efficiency and crosslinking kinetics of cell-encapsulating hydrogels. The hydrogels were photopolymerized from poly(ethylene glycol) (PEG) diacrylate or PEG-fibrinogen precursors using Irgacure PIs I2959, I184 and I651, as well as with a chemical initiator/accelerator (APS/TEMED). The study specifically evaluated the PI type, PI concentration and UV light intensity, and how these affected the mechanical properties of the hydrogel (i.e. maximum storage modulus), the crosslinking reaction times and the reaction's cytotoxicity to encapsulated cells. Only two initiators (I2959 and I184) were identified as being suitable for achieving both high cell viability and efficient crosslinking of the cell-encapsulating hydrogels during the photopolymerization reaction. Optimization of PI concentration or irradiation intensity was particularly important for achieving maximum mechanical properties; a sub-optimal choice of PI concentration or irradiation intensity resulted in a substantial reduction in hydrogel modulus. Cytocompatibility may be compromised by unnecessarily prolonging exposure to cytotoxic free radicals or inadvertently enhancing the instantaneous dose of radicals in solution, both of which are dependent on the PI type/concentration and irradiation intensity. In the absence of a radical initiator, the short exposures to long-wave UV light irradiation (up to 5 min, 20 mW cm(-2), 365 nm) did not prove to be cytotoxic to cells. Therefore, it is important to understand the relationship between PIs, light irradiation conditions and crosslinking when attempting to identify a suitable hydrogel formation process for cell encapsulating hydrogels.
Introduction: The natural extracellular matrix (ECM) has been an attractive model for the design and fabrication of bioactive scaffolds for tissue engineering. In this study, gelatin (major protein in ECM) and elastin (major protein in elastic tissue) were conjugated into polyethylene glycol (PEG) hydrogel in order to mimic multiple functions of the elastic natural ECM for repairing injured tissue.
Microfluidics has been used to process self-assembling liposomal systems that are commonly considered for drug delivery applications. However, it has been found that the parameters of the process are not universally suited for all lipid types. We hypothesize here that size aggregation and instability of microfluidic liposomes are a direct consequence of the presence of interdigitation in these liposomes. Interdigitation refers to the phenomenon where two opposing leaflets of a bilayer interpenetrate into one another and form a single layer. When this happens, aggregation results as the single layer is not thermodynamically stable. Such interdigitation can be induced by pressure, chemicals or by the type of lipid structure. In this study, we systematically investigate the role of lipid composition on membrane interdigitation in order to understand the dependency of lipid interdigitation on liposome formation by microfluidics. By doing so, we use nano DSC and SAXS to probe the extent of lipid interdigitation by measuring the changes in thermodynamics and membrane thickness of the lipid bilayers. Our results show that microfluidic-fabricated liposomes undergo chemical interdigitation in the presence of ethanol, in particular saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Strategies to prevent interdigitation is to either remove ethanol above the lipid's main transition temperature (Tm), preventing the formation of interdigitated structures and subsequent aggregated states or by the incorporation of the inhibiting additives, such as cholesterol.
In burning and heating method, HA of bones will be transformed into BCP ceramic with a wide range of HA/β-TCP compositions. Ooi et al.[14] used cancellous bovine bone alone, without any additives or reactant material. As a result, they could not produce ceramic with a wide range of chemical composition. Lin et al.[13] used reactant materials such as di-ammonium hydrogen phosphate ((NH4)2HPO4) to widen the chemical composition of BCP.