Sensors, molecular imprinting

SENSORS BASED ON FREE-STANDING MOLECULARLY IMPRINTED POLYMER MEMBRANES. COMPUTATIONAL MODELLING OF SYNTHETIC MIMICKS OF BIORECEPTORS... 

SENSORS WITH RESPONSE ON SOME XANTHENE DYES BASED ON MOLECULARLY IMPRINTED ELECTROSYNTHESIZED POLYMERS... 

The development of highly selective chemical sensors for complex matrixes of medical, environmental, and industrial interest has been the object of greate research efforts in the last years. Recently, the use of artificial materials - molecularly imprinted polymers (MIPs) - with high recognition properties has been proposed for designing biomimetic sensors, but only a few sensor applications of MIPs based on electrosynythesized conductive polymers (MIEPs) have been reported [1-3]. 

Possible applications of MIP membranes are in the field of sensor systems and separation technology. With respect to MIP membrane-based sensors, selective ligand binding to the membrane or selective permeation through the membrane can be used for the generation of a specific signal. Practical chiral separation by MIP membranes still faces reproducibility problems in the preparation methods, as well as mass transfer limitations inside the membrane. To overcome mass transfer limitations, MIP nanoparticles embedded in liquid membranes could be an alternative approach to develop chiral membrane separation by molecular imprinting [44]. 

Kriz, D Ramstrom, O Mosbach, K, Molecular Imprinting, New Possibilities for Sensor Technology, Analytical Chemistry June 1, 345A, 1997. 

Zougagh, M., Valcarcel, M., and Rios, A., Automatic selective determination of caffeine in coffee and tea samples by using a supported liquid membrane-modified piezoelectric flow sensor with molecularly imprinted polymer. Trends Anal. Chem., 23, 399, 2004. 

Haupt K. and Mosbach K., Molecularly Imprinted Polymers and Then Use in Biomimetic Sensors, Chem Rev 2000 100 2495-2504. 

Molecularly imprinted polymers have recently attracted much attention because they are denoted as artificial antibodies which are made from simple chemical components via polymerization and can be used for the preparation ofbiomimetic sensors, affinity separation matrices, catalysts, etc. (Figure 1). 

Diaz-Garcia M.E., Badia R., Molecularly imprinted polymers for optical sensing devices" in Optical Sensors Industrial, Environmental and Diagnostic Applications, R. Narayanaswamy, O. S. Wolfbeis, (Eds.), Springer, 2004. 

The scientists from Hong Kong reported83 on a sol-gel derived molecular imprinted polymers (MIPs) based luminescent sensing material that made use of a photoinduced electron transfer (PET) mechanism for a sensing of a non-fluorescent herbicide - 2,4-dichlorophenoxyacetic acid. A new organosilane, 3 - [N,V-bis(9-anthrylmethyl)amino]propyltriethoxysilane, was synthesized and use as the PET sensor monomer. The sensing MIPs material was fabricated by a conventional sol-gel process. 

A.L. Jenkins, R. Yin, and J.L. Jensen, Molecularly imprinted polymer sensors for pesticide and insecticide detection in water. Analyst 126, 798-802 (2001). 

Size-related problems may become important for all microsensors. Leakage of sensing materials from a small membrane may lead to rapid deterioration of sensor properties [104], While the lipophilicity of membrane components cannot be increased infinitely, immobilization of ionophore and ion exchanger in the polymer by covalent attachment or molecular imprinting along with utilization of plasticizer-free membranes could help solve the leakage problem. 

The concept is extendable to templated sensors made of protein templated xerogels in which a luminescent reporter group is further added in close proximity to the template site so as to effectively transduce the protein-molecularly imprinted polymer binding event (Figure 6.12).11... 

The concept of thin films of a molecularly imprinted sol-gel polymer with specific binding sites for a target analyte is general and can be applied also to electrochemical sensors. For example, a sensor to detect parathion in aqueous solutions is based on films cast on glass substrates and on glassy carbon electrodes (Figure 6.14).12... 

S. Marx, A. Zaltsman, I. Turyan and D. Mandler, Parathion sensor based on molecularly imprinted sol-gel films, Anal. Chem., 2004, 76, 120. 

In conclusion, molecularly imprinted polymers and related materials have every potential to become popular tools in analytical chemistry, catalysis, and sensor technology. Obviously this will require further research, especially in the problem areas of MI mentioned above. Nevertheless, the author of this contribution fully expects that in the near future MIP will become real competitors for biological enzymes or antibodies, and thus will have a major impact on the whole area of biotechnology. 

This chapter will introduce the field of sensors based on molecular imprinted polymers (MIPs). MIPs are highly cross-finked polymers that are formed with the presence of a template molecule (Haupt and Mosbach 2000 Wulff 2002). The removal of the template molecule from the polymer matrix creates a binding cavity that is complementary in size and shape to the template molecule and is fined with appropriately positioned recognition groups (Scheme 15.1). 

---