Immobilization deposition method

J. Yu and H.X. Ju, Preparation of porous titania sol-gel matrix for immobilization of horseradish peroxidase by a vapor deposition method. Anal. Chem. 74, 3579-3583 (2002). 

J. Yu, S. Liu, and H.X. Ju, Mediator-free phenol sensor based on titania sol-gel encapsulation matrix for immobilization of tyrosinase by a vapor deposition method. Biosens. Bioelectron. 19, 509-514 (2003). 

Fig. 1 Comparison of a conventional DNA-attachment scheme and the silanized nucleic acid strategy. A In conventional deposition methods the slides are universally coated with silane or poly-lysine, then oligonucleotides or cDNA is deposited on the modified surface. The areas on the chip that are not occupied with DNA will have to be blocked in hybridization experiments. B The DNA or oligonucleotides are modified with a silyl group that can directly immobilize the DNA onto an unmodified glass surface...

The enzymatically coupled FET is reviewed in this chapter (32). First, a brief review is given. Determining how to deposit an enzyme-immobilized membrane on the surface of a FET was one of the most difficult problems to solve before tin enzymatically coupled FET could be developed. Therefore, some enzyme-immobilized membrane deposition methods and the photolithographic enzyme-immobilized membrcme patterning method developed by the authors are described in detail. Concomitantly, the performances of some FET biosensors with an enzyme-immobilized membrane made by this method are described. Finally, recent applications of an enzymatically coupled FET are surveyed. 

The three enzyme membrane deposition methods can be adapted for the preparation of different enzyme-immobilized membranes on a single FET chip simply by repeating the cycle of coating, irradiation, and development procedures in the cases of the first and third methods, and by the injection of a different enzyme-immobilizing solution into a different micropool in the case of the second method. 

In 2003, Dai et al. [80] reported a strategy for a reagentless immunosensor for the determination of carcinoma antigen-125 (CA-125) based on the immobilization of antigen and the direct electrochemistry of HRP bound to an antibody. The immunosensor was prepared by immobilizing CA-125 with titania sol-gel on a GCE by the vapour deposition method. The incubation of the immunosensor in phosphate buffer solution containing HRP-labelled CA 125 antibody leads to the formation of an HRP-modified surface. The immobilized HRP displays its direct electrochemistry with a rate constant of 3.04 1.21 s . With a competition mechanism, a differential pulse voltam-metric determination method for CA-125 was established by the peak current decrease of the immobilized HRP. The current decrease resulted from the... 

A method first described around 1980 has remained popular - drying a slurry of support material (commonly celite) in an enzyme solution. The resulting powder necessarily contains both solid support and enzyme. However, the link between them is usually very weak, and the method is now usually described as co-drying or deposition rather than immobilization. At least some of the enzyme is probably present as large aggregates, not close to the support. My impression is that catalytic activity is usually poorer than with enzymes immobilized by methods more likely to produce an even protein layer. 

The polyion complex technique [15] was proposed as a convenient preparative method to immobilize water-soluble, bilayer-forming amphiphiles and polymers as composite thin films. A water-insoluble polyion complex is precipitated when the aqueous solution of the charged bilayer membrane is mixed with a water solution of the countercharged polyelectrolyte. The polyion complex mono-layer also can be formed in situ when the charged amphiphiles are directly spread on the surface of the aqueous polyelectrolyte solution. The principle of the polyion complex LB technique has been expanded into a general and simple alternative deposition method of charged polymers by Decher [16] (this volume chapter 12). 

The preparation of immobilized CdTe nanoparticles in the 30-60 nm size range on a Te-modified polycrystalline Au surface was reported recently by a method comprising combination of photocathodic stripping and precipitation [100], Visible light irradiation of the Te-modified Au surface generated Te species in situ, followed by interfacial reaction with added Cd " ions in a Na2S04 electrolyte. The resultant CdTe compound deposited as nanosized particles uniformly dispersed on the Au substrate surface. 

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