# Recent Lipid Membrane-Based Biosensing Platforms
## 3 Lipid Membrane-Based Biosensing
A hybrid structure is produced with part of the membrane covering the pores and the rest lying on the solid surface (Figure 5g); the analytical useful part of the membrane is confined over the pores, giving rise to a network-like architecture of mini-membranes that can accommodate more bioelement molecules within a given area, as compared to a single membrane. Studies have shown that higher the thickness of the material and the smaller the pore size, the higher the stability of the membrane [44]. It, also, turned out that stray capacitance and leakage current values are lower in such constructs [41], allowing for chip integration. Polymer-supports (Figure 5h), including chitosan [47], hydrogels [48], or dextrans [30], cushion membranes to simulate the cytosol of the cell, to insert a hydrophilic area between the membrane and the substrate and to give membranes good electrical sealing for protein studies. However, conditions should be optimized for surface interrogation: Substrate thickness should be low and roughness should be high, whereas the thickness of the gel should be adequate to yield a smooth plane [48]. Lengthy experiments may be complicated by gel cracking due to aging and membrane fluidity decay [49]. Complex architectures can be achieved by Langmuir-Blodgett membranes, formed by stacking monomolecular (LB) films on solid supports. The thickness and the size of the layers can be controlled, lipid alignment can be tuned, mixed membranes, even with varying composition, can be produced, and large area patterning is possible [50]. These structured layers are used in engineering biological interfaces in molecular electronic devices [51]. Mechanically stable membranes can be produced via polymerization or microfabrication. UV irradiation or thermal polymerization involves the spread of a lipid solution over a polymer base [52]; if UV-assisted, bioelements can be added in the lipid solution or after the membrane formation; if temperature-assisted, bioelements are added only after membrane formation to avoid denaturation. Automated lipid assembly into vertically-oriented micro-bilayers has been extensively used in chip integration [53]. Further, microfluidic devices drive bilayer assembly through droplet collisions. Droplet interface bilayers can assume higher structures and seeded with pores or channels to simulate complex natural membrane systems and intracellular signal transduction cascades [54]. Microscope-monitored nanotopography forms bilayers in nano-pits [55]. Using a combination of Langmuir-Blodgett technology and vesicle fusion, the whole process can be fully automated, provided humidity and temperature are optimized. Dip-pen nanolithography, uses an atomic force microscope to deposit lipids on substrates and control their interaction [56]. Multicompositional arrays can be; thus, prepared with minimal effort and high reproducibility [57]. The range of biochemical interactions that have been monitored with these lipid membrane platforms is vast, indeed, including enzyme-substrate systems [58], redox-active proteins [59], immunological assemblies [60], nucleic acid and nucleotide-assisted detection or sequencing [61], pore forming toxins [59], ion channels [62], ligand-coupled receptors [63], hormonal function [62], inorganics, and chemical pollutants [64]. Methods for the Preparation of the Most Important Platforms of Stabilized Biosensors Based on Lipid Membranes  
During the last decade, the construction of stabilized lipid film-based biosensors that are not prone to electrical or mechanical shock and are stable outside an electrolyte solution has been the investigation of a number of reports; these investigations will provide devices that can be commercialized due to their practical applications. Nanotechnological advances have provided a route to construct devices so that their size is less than 1 \(\upmu\)m size and; therefore, belong to the class of nanosensors.