Collagen-Like Peptide as a Matrix for Enzyme Immobilization in Electrochemical Biosensors

Immobilization of the Alkaline Phosphatase on Collagen Surface via Cross-Linking Method

BACKGROUND

Collagen, the most abundant protein in the human body, and as an extracellular matrix protein, has an important role in the fiber formation. This feature of the collagen renders establishment of the structural skeleton in tissues. Regarding specific features associated with the collagen, such as, formation of the porous structure, permeability and hydrophilicity, it can also be used as a biocompatible matrix in the enzyme engineering.

OBJECTIVES

The aim of the present study was to investigate the application of the type I collagen as a matrix for alkaline phosphatase immobilization using cross-linking method.

MATERIALS AND METHODS

The Alkaline phosphatase was covalently immobilized on collagen matrix by using 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride (EDC). The source of the alkaline phosphatase was from the bovine intestinal mucous. After that, the activity of the immobilized enzyme was assayed under different experimental conditions.

RESULTS

The optimum pH was similar to that of the free enzyme, whereas the optimum temperature and thermal stability were shown some increments. The surface topography of the collagen matrix containing immobilized enzyme and ALP (Alkaline phosphatase) deficient was investigated by Atomic-force microscopy (AFM). Images that have been obtained applying AFM show significant differences between uncovered and immobilized enzyme- matrix surface topography.

CONCLUSIONS

Our findings suggest that type I collagen can be utilized as a matrix for alkaline phosphatase immobilization via cross-linking method.

Proteins and peptides as biological nanowires: towards biosensing devices

The current landscape of nanotechnology is such that attention is being given to those materials that self-assemble, as a mode of "bottom-up" fabrication of nanomaterials. The field of nanotubes and nanowires has long been dominated by carbon nanotubes and inorganic materials. However in more recent years, the search for materials with desirable properties, such as self-assembly, has unsurprisingly led to the biological world, where functional nanoscale biomolecular assemblies are in abundance.Potential has been seen for a number of these assemblies to be translated into functional nanomaterials. The early days of bionanotechnology saw a lot of attention given to DNA molecules as nanowires, and proteins and peptides have now also been seen to have promise in this area. With most of the biological structures investigated having low conductivity in the native state, the use of biomolecules as templates for the formation of metallic and semiconductor nanowires has been the direction taken.This chapter will discuss the use of various biomolecules and biomolecular assemblies as nanowires, with a particular emphasis on proteins, beginning with an introduction into the field of nanotubes and nanowires. Many applications are now recognized for nanowires, but for brevity, this chapter will focus solely on their use as biosensors, using glucose sensors as a case study.

Improved enzyme immobilization on an ionic-complementary peptide-modified electrode for biomolecular sensing

An ionic-complementary peptide, EFK16-II, was used to modify a highly ordered pyrolytic graphite (HOPG) electrode surface. The nanofiber structure of the self-assembling peptide on the electrode surface was characterized by atomic force microscopy (AFM). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectra showed that, upon addition of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), EFK16-II molecules tend to be cross-linked among themselves. Cross-linking of the peptide diminishes the number of carboxyl groups available for immobilizing a sensing enzyme, which is glucose oxidase (GOx) in the present case. A simple method based on premixing of the carbodiimide and GOx was developed; it inhibited peptide cross-linking and significantly improved enzyme immobilization. Biosensors constructed in this way showed increased overall signal intensity and a much higher sensitivity at 4.94 mA M(-1) cm(-2), a 6-fold increase compared to the previously reported peptide-modified electrodes. The results presented here demonstrate significant potential for ionic-complementary peptides for constructing electrochemical biosensors.

Synthesis of alpha-chymotrypsin/polymer composites by a reverse micelle/gas antisolvent method

Alpha-chymotrypsin (CT)/polyvinylpyrrolidone (PVP) composites was synthesized by combination of reverse micelles and CO(2). In this method, the two reverse micellar solutions containing CT and PVP, respectively, were first mixed, then compressed CO(2) was used as an antisolvent to precipitate the CT and PVP simultaneously and CT/PVP composites were successfully prepared. The morphology of the obtained CT/PVP composites was characterized by transmission electron microscopy (TEM). The FTIR spectra of the composites showed that there was interaction between CT and PVP. The storage activity of the enzyme immobilized on the polymer by this method was higher than that of the pure enzyme. This method has some advantages and can be easily applied to the synthesis of some other enzyme/polymer composites.