5 Smart membranes for glucose sensing

Nano-structured membranes for various applications including biosensing have been comprehensively reviewed elsewhere [166–168]. The membrane materials, their structure and porosity play an important role in their selective permeability to solutes. They are said to be nano-porous when their pore sizes are less than 100 nm, and sometimes the upper limit is extended to 500 nm. Further, based on porosity they are classified into four categories: 1) non-porous, 2) microporous (≤2 nm), 3) mesoporous (2–50 nm), and 4) macroporous (50–500 nm) [167]. Membranes based on all four categories have been used for glucose biosensing and their use has four major purposes: 1) to entrap or immobilize enzyme or other glucose affinity molecules at sensing surface, 2) to avoid interferents (that compromise sensor function) from reaching the sensing element, 3) to widen the dynamic glucose measuring range (covering the required 2–30 mM), and 4) to tailor the foreign body responses to implantable glucose biosensor and enhance their reliable sensing lifetime upon implantation.