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Selection Considerations for Membranes and Models for In Vitro/Ex Vivo Permeation Studies
Published in Tapash K. Ghosh, Dermal Drug Delivery, 2020
Pei-Chin Tsai, Tannaz Ramezanli, Dina W. Ameen, Sonia Trehan, Nathaly Martos, Zheng Zhang, Bozena Michniak-Kohn
A wide spectrum of polymeric membranes is available on the market. These polymeric membranes can be categorized according to different criteria. For example, according to the composition, polymeric membranes can be grouped as “silicone based” (with the main component polydimethylsiloxane, PDMS),68 “cellulose based” (e.g., regenerated cellulose, cellulose esters and cellulose nitrate),69 and “synthetic polymeric” based (e.g., polyacrylonitrile, nylon, sulfone, polycarbonate and polypropylene membrane, and others). The polymeric membranes can also be characterized based on whether they are porous or non-porous: for example, silicone membranes are non-porous, while cellulose-based and synthetic polymeric membranes are often porous, having different thickness, pore size and molecular weight cut off (MWCO) values. Also, polymeric membranes can be grouped into high-flux and low-flux type, based on the value of flux.70 Overall, polymeric membranes are widely used to study the drug release (which is different from drug permeability) from formulations that are applied in the Franz diffusion cell technique. In the following section, the studies on skin permeability using silicone membranes are further discussed since they are often employed to simulate the skin due to their skin-imitating lipophilicity and rate-limiting permeation properties.71,72,73
Modeling the antifouling properties of atomic layer deposition surface-modified ceramic nanofiltration membranes
Published in Biofouling, 2022
Welldone Moyo, Nhamo Chaukura, Machawe M. Motsa, Titus A. M. Msagati, Bhekie B. Mamba, Sebastiaan G. J. Heijman, Thabo T. I. Nkambule
The effectiveness of membrane separation performance is delineated by the physico--chemical properties, composition and microstructure of the active layer (Tylkowski and Tsibranska 2015). Membranes can either be derived from organic/polymeric or inorganic/ceramic materials. Polymeric membranes have been preferred because they are relatively cheaper compared to ceramic membranes. However, they suffer several limitations such as a short life span, limited recyclability and poor chemical, mechanical and thermal stability (Metsämuuronen et al. 2014). In comparison, ceramic membranes derived from metal oxides, typically zirconia, titania, alumina and more recently silicon carbide, have high selectivity and superior mechanical, thermal and chemical stability (Amin 2016). For this reason, ceramic membranes have found applications in food processing, pharmaceutical production, petrochemical refining, chemical manufacturing and water and wastewater treatment, where the conditions can be extreme (Metsämuuronen et al. 2014). The utility of ceramic membranes is further enhanced by modifying the membrane surface and tuning the porosity through the choice of precursors and the fabrication conditions or by post modification treatments following synthesis.
Hybrid powdered activated carbon-activated sludge biofilm formation to mitigate biofouling in dynamic membrane bioreactor for wastewater treatment
Published in Biofouling, 2022
Mohammad Reza Mehrnia, Fatemeh Nasiri, Fatemeh Pourasgharian Roudsari, Fatemeh Bahrami
Combining solid-liquid separation and biological treatment (Lee et al. 2020), membrane bioreactors (MBRs) have been extensively adopted for municipal and industrial wastewater treatment over the last decades (Sokhandan et al. 2020). Some advantages of MBRs over conventional activated sludge processes including high concentrations of mixed liquor suspended solids (MLSS), high quality of permeate and substantially small footprint have made them broadly applicable in wastewater treatment (Ko 2018; Etemadi and Yegani 2019). Despite MBR advantages, fouling and the high cost of membranes are the main obstacles to the widespread use of MBRs in the industry (Liébana et al. 2015; Sari Erkan et al. 2020). The biofilm on the surface of a membrane reduces the operational flux or increases transmembrane pressure (TMP) depending on the operation mode (Mafirad et al. 2011). On the other hand, biofouling rejects finer particles such as viruses and inorganic ions (Najmi et al. 2020). Consequently, many scientific endeavours have been focusing on minimization of the fouling affecting long-term filtration of micro/ultra-polymeric membranes.
Pharmaceutical implants: classification, limitations and therapeutic applications
Published in Pharmaceutical Development and Technology, 2020
Zahra Mohtashami, Zahra Esmaili, Molood Alsadat Vakilinezhad, Ehsan Seyedjafari, Hamid Akbari Javar
There are many possible classifications for implantable systems. In general, two major groups of “drug implants” and “implantable drug-loaded pumps” could be addressed. In the first group, i.e. drug implants, various types of polymers, and polymeric membranes are used to control the drug release from the delivery system. The latter group, i.e. implantable drug-loaded pumps, utilize a mechanical pump to control the drug release (Danckwerts and Fassihi 1991). Following the technological advances in this area, the third atypical group of implants has emerged. Different delivery systems such as sustained-release intraocular systems for the treatment of glaucoma, hydroxyapatite cement systems used in osteomyelitis, and transurethral injection systems for impotence are a few examples.