Detection Of The Proteins Based On Liquid-Crystal Biosensors

Recently, liquid crystal molecules have been introduced in sensor fields, exceptthat they have been widely applied to electronic display panels. Especially, liquidcrystal molecules are used to build liquid crystal biosensor in life sciences, and havebursted on the scene edge. Liquid crystal biosensor is of great potential for providingsimple, fast, highly sensitive, label-free and low-cost bioassays. Therefore, thedevelopment is undoutedly of great contribution to the improvement of chemical andbiological sensor. In this paper, severed new liquid crystal biosensor, has beenpropored as following:1. A new liquid crystal biosensor has been development for the detection ofhemoglobin by combining the molecular imprinting technology. Since thecharacteristics of hemoglobin have been well studied, here we employed hemoglobin(Hb) as a prove of concept template protein. Covalent immobilization was achieved byforming imine bonds between the amino groups on the protein surface and theanchored aldehyde groups on glass. Following immobilization of the hemoglobinpromplate template, the organic silanemonomers DMOAP were self-assembled ontothe Hb-glass surface. Protein-imprinted silica using covalently immobilized templateHb (MIPi) was easily obtained by this method, and it has been demonstrated to be ofgood thermostability, mechanical strength and capability as a carrier for proteinseparation. This research is a preliminary exploration to biological macromolecularimprinting. The protein molecules can disrupt the alignment of liquid crystalmolecules. According to the birefringence of the liquid crystal (5CB), the change ofordered alignment of liquid crystal molecules can cause the change of image inpolarization microscope. Thus, we can detect protein molecules. The results show thatthe sensor can be quickly and effectively to detect low concentration levels ofhemoglobin. Using molecular imprinting method and combining with thecharacteristics of liquid crystal sensor, this propored method has realized the Hbmolecules biological molecules detection at the concentration and low to0.3μg/mL.2. Due to the limit at the detection sensitivity, the LC biosensing technique basedon direct biomolecular binding events is difficult to meet the demand of ultrasensitiveprotein assays. Herein we construct a new signal-enhanced liquid-crystal biosensorsbased on enzymatic metal deposition to detect thrombin. First, a chemicallyfunctionalized surface on a plane glass slide is obtained by self-assembling a APS/DMOAP film. The DNA immobilization was then achieved by binding a captureDNA probe to the APS/DMOAP film through a cross-linker(GA), followed byhybridizations of a biotinylated detection DNA probe and thrombin. Due to the highaffinity between streptavidin and biotin, the Sv-ALP can easily bound to the signalDNA probe, then catalytic ascorbic acid phosphate hydrolysis into ascorbic acid. Canthe silver ions insolution can be reduct to the metal silver by the reducting product,accorbic acid, and the latter then deposits on the glass slide. This effect revealed thatthe homeotropic-to-tiled transition of LCs are caused by the deposited silver, anexcellent signal enhancement element. The combination of enzymatic signalamplification and LC-based imaging contributed a highly selective and ultrasensitivemethod for the detection of thrombin. Signal enhancement technology researchprovides a new way for the improvement of sensitivity of the sensor detection and theapplication range of the liquid crystal sensor technology.3. Herein, we construct a new functionalized liquid-crystal biosensors based onthe aptamer to detect thrombin.The thrombin-binding aptamer is known to fold into aquadruplex structure, which contains two G(syn)-G(anti)-G(syn)-G(anti) quartets andthree lateral loops, usually referred to as a "hair structure". First, a chemicallyfunctionalized surface on a plane glass slide is obtained by self-assembling aAPS/DMOAP film. DNA immobilization was then achieved by binding a capture DNAprobe to the APS/DMOAP film by a cross-linker(GA), followed by hybridizations of adetection DNA probe and thrombin. According to the change of image in polarizationmicroscope, we can detect thrombin. The results show that the sensor can be quicklyand effectively to detect the concentration of thrombin, low to0.1nM.