Enhanced permeation retention

Ultrafiltration of heterogenous colloidal suspensions such as citrus juice is complex and many factors other than molecular weight contribute to fouling and permeation. For example, low MW aroma compounds were unevenly distributed in the permeate and retentate in UF in 500 kd MWCO system (10). The authors observed that the 500 kd MWCO UF removed all suspended solids, including pectin and PE. If PE is complexed to pectate in an inactive complex, then it is conceivable that release of PE from pectin with cations will enhance permeation in UF. At optimum salt concentration, less PE activation was observed at lower pH values than at higher pH (15). In juice systems, it is difficult to separate the effect of juice particulates on PE activity. Model studies with PE extracts allows UF in the absence of large or insoluble particulates and control of composition of the ultrafilter. In... 

By utilizing polymerization in the miniemulsion system, larger HPG analogues can be created by linking several HPG units to a nanoparticle in order to obtain an optimum diameter of 50 nm [116], This size range is considered to be ideal for drug delivery carriers that may accumulate in tumors or inflamed tissue by the enhanced permeation and retention effect (EPR) [52],... 

This is unfortunate because the theoretical advantage of nanosystems is their small size, allowing freer movement than microspheres in the circulation, including the lymph and in tissues. Flow rates are important not least in the determination of the possibility of nanoparticle interaction with endothelial receptors prior to internalization, or indeed in the decoupling of carriers and receptors due to shear forces. Flow of nanoparticles is a vital element in extravasation and in the enhanced permeation and retention (EPR) effect. What is the influence of nanoparticle size on particle flow in the circulation And, with the advent of CNTs in particular, what is the influence of shape on flow and fate CNTs certainly behave differently in the blood from spherical C60 fidlerenes. CNTs activate human platelets and induce them to aggregate, whereas their spherical analogues do not... 

Decreased lymphatic drainage keeps the carriers in the tumor. This passive targeting mechanism has been called the enhanced permeation and retention (EPR) effect and was first identified by Maeda et al. [98,99]. Numerous studies have shown that the EPR effect results in passive accumulation of macromolecules and nanosized particulates (e.g., polymer conjugates, polymeric micelles, dendrimers, and liposomes) in solid tumor tissues, increasing the therapeutic index while decreasing side effects. Figure 4 describes the concept of passive tumor targeting by EPR effects. 

Microemulsion-based gel showed greater retention of drug into skin layers than microemulsion and market preparation. Microemulsion-based gel was found to be significantly less irritating. Results indicated interaction of microemulsion components with skin, resulting in permeation enhancement and retention of drug into skin layers. 

Then it appeared that conjugation of drugs with a polymer or macromolecule enhanced its passive distribution in favour to tumour tissue. This enhanced permeation and retention (EPR) effect was explained by differences... 

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