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Membrane Coating
Published in Sam A. Hout, Manufacturing of Quality Oral Drug Products, 2022
Cellulose acetate is used as the primary membrane film coating polymer. Typically, average molecular weight specifications for cellulose acetate are 320S and 398-10. Cellulose acetate 320S forms membranes with slightly larger pores, which increase the movement of water through the membrane. In addition to cellulose acetate at 60% solids, hydroxypropyl cellulose at 35% solids might be used in combination with a plasticizer at 5%. The hydroxypropyl cellulose is soluble in water and acts as a flux enhancer. After ingestion, it is dissolved by water in the digestive system and opens the membrane, increasing its permeability.
Mucoadhesive Polymers
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
A further advantage of mucoadhesive polymers can be seen in the high buffer capacity of ionic polymers. As these polymers can act as ion exchange resins, they are able to maintain their pH value inside the polymeric network over a considerable period of time. Matrix tablets based on neutralized carbomer, for instance, can buffer the pH value inside the swollen carrier system even for hours in an artificial gastric fluid of pH 2 [112]. This high buffer capacity seems to be highly beneficial for various reasons. For example, the epidermal growth factor (EGF) is recognized as an important agent for acceleration of ulcer healing and has a peculiar biological property to repair tissue damage by an enhanced proliferation and differentiation of epithelial tissues [113]. Itoh and Matsuo demonstrated in a double-blind controlled clinical study the enhanced healing of rat gastric ulcers after oral administration of EGF. This effect could even be drastically increased by using the mucoadhesive polymer hydroxypropyl cellulose as drug carrier matrix [114]. As EGF is strongly degraded by pepsin [115], the use of mucoadhesive polymers providing an additional protective effect toward pepsinic degradation might therefore be helpful. It can be achieved by a comparatively higher pH value inside the drug carrier matrix based on its high buffer capacity at which penetrating pepsin is already inactive.
Preparation, stimuli-response performance of HPC-PMAA/PpIX nanogels and their application in photodynamic therapy
Published in Journal of Biomaterials Science, Polymer Edition, 2022
Chengyan Zhao, Qiusheng Song, Lin Zhu, Haihong Ma
Hydroxypropyl cellulose (HPC) is a kind of typical natural polymer, and it has been widely used to produce drugs, adhesives, foods, cosmetics, etc. [6–8]. As it is compatible well with organism and is biodegradable, particularly, it is thermo-sensitive with a volume phase transition temperature (VPTT) around 41 °C. Therefore, nanogels based on HPC have caught great attentions for application in controllable drug loading [9] and releasing [10]. For example, Lu and coworkers [11,12] reported a series of thermo-sensitive nanogels made from HPC and acrylics. Song et al. [13] prepared thermo-sensitive fluorescent complex gels from HPC and rare-earth compound, and the gels show excellent performance for drug loading and releasing. Because HPC/acrylics nanogels can be synthesized without emulsifiers and organic solvents, they have been thought as ‘green’ ones [14,15].