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. Author manuscript; available in PMC: 2012 Sep 1.
Published in final edited form as: Trends Cell Biol. 2011 Jul 3;21(9):543–551. doi: 10.1016/j.tcb.2011.06.002

Figure 2.

Figure 2

Biopolymer based hydrogels control the translocation of microscopic objects and act as selective permeability filters. They allow the passage of certain molecules (green) whereas rejecting others (orange). (A) The epithelium is lined with a layer of mucin polymers, which form a hydrogel that shields the underlying cell layer from infectious agents such as viruses or bacteria. (B) Extracellular matrix systems such as the basal lamina or the connective tissue regulate the passage of molecules to and from the blood stream or between cells. (C) Nuclear pores are filled with nucleoporin polymers, which regulate the import and export of proteins into or out of the nucleus. (D) In bacterial biofilms, extracellular polymers effectively shield the bacteria from antibiotics while allowing nutrients to enter the biofilm. (E) The vitreous humour in the mammalian eye allows the penetration of certain antibiotics while blocking others.