Biomaterials for MEMS

206 P. Y. J. Yeh, J. N. Kizhakkedathu and M. Chiao

Figure 9.1. Schematic diagram of the proposed piezoelectric membrane as an implantable

sensor coating. The membrane is composed of two driving electrodes with a piezoelectric

material in between. Adsorbed protein can be desorbed by an electric field and carried

away by acoustic flow generated by the vibration. Reproduced with the permission from

Yeh et al. (2007).

MEMs fabricated device is evaluated by the criteria of protein quantity on the

surface. Figure 9.1 shows the schematic diagram of an antibiofouling mechanism

which is able to integrate an implant, such as, biosensor. Three steps of this

mechanism shown in the Fig. 9.1 are: (1) protein adsorption, (2) protein desorption

by surface charges, and (3) the desorbed proteins swept by the flow.

9.2 PROTEINS VISUALIZATION

There are many methods to identify or visualize the protein adsorbed on the

surface, to name a few, silver stain, radioactive labeling, reverse stain, fluorescence,

chemiluminescence,

41

AC impedance, quartz crystal nanobalance,

42

and so on.

Mainly the fluorescence detection and the electrochemical impedance measure-

ment are used to investigate the adsorption of proteins In this chapter. Fluores-

cence detection can determine the relative amount of adsorbed proteins,

10,43,44

the

advantage of this method is its linearity (intensity vs quantity) and sensitivity. It

is a relatively convenient method to detect proteins. By attaching fluorescence

dyes of emitting different colors, it is easy to identify different proteins on the

surfaces.

45

But it is not the best method to quantify adsorbed proteins especially

if the substrate has a fluorescence background. The electrochemical impedance

spectroscopy (EIS), on the other hand, is sensitive to the adsorption on interface.

It also can be used to investigate the dynamic adsorption behavior of protein and

the thickness of adsorbed proteins.

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