ABSTRACT
In this paper, we describe the development, functionalization and functionality testing of a TeraHertz (THz) Bio-MicroElectroMechanical System (BioMEMS) dedicated to enzyme reaction analysis. The microdevice was fabricated by mixing clean room microfabrication with cold plasma deposition. The first is used to build the microfluidic circuits and the THz sensor, while the later serves for the polymerization of allylamine using a homemade glow discharge plasma reactor for a subsequent immobilization of enzymatic biocatalysts. Thermal stability of the deposited plasma polymer has been investigated by infrared spectroscopy. Fluorescent detection confirmed the efficiency of the immobilization and the enzyme hydrolysis into the BioMEMS microchannels. For the first time, the progression of the hydrolysis reaction over time was monitored by the THz sensor connected to a vectorial network analyzer. Preliminary results showed that sub-THz transmission measurements are able to discriminate different solid films, various aqueous media and exhibit specific transmission behavior for the enzyme hydrolysis reaction in the spectral range 0.06-0.11 THz.
Subject(s)
Enzymes, Immobilized/metabolism , Micro-Electrical-Mechanical Systems/instrumentation , Microtechnology/methods , Allylamine/chemistry , Animals , Cattle , Enzymes, Immobilized/chemistry , Equipment Design , Hydrolysis , Micro-Electrical-Mechanical Systems/methods , Trypsin/chemistry , Trypsin/metabolismABSTRACT
This paper focuses on the immobilization of a proteolytic enzyme, trypsin, on plasma polymerized allylamine (ppAA) films. The later have been deposited onto silicon substrate by means of radiofrequency glow discharge. The covalent attachment of the enzyme was achieved in three steps: (i) activation of the polymer surface with glutaraldehyde (GA) as a linker, (ii) immobilization of trypsin and (iii) imino groups reduction treatment. The effects and efficiency of each step were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Fluorescent spectroscopy was used to evaluate the change of the biological activity following the immobilization steps. The results showed that enzyme immobilization on GA-modified substrate increases the enzyme activity by 50% comparing to adsorbed enzymes, while the imino reduction treatment improves the enzyme retention by about 30% comparing to untreated samples. In agreement with XPS and AFM data, UV-vis absorption spectroscopy, used to quantify the amount of immobilized enzyme, showed that allylamine plasma polymer presents a high adsorption yield of trypsin. Although the adsorbed enzymes exhibit a lower activity than that measured for enzymes grafted through GA linkers, the highest catalytic activity obtained was for the enzymes that underwent the three steps of the immobilization process.
Subject(s)
Allylamine/metabolism , Polymers/metabolism , Trypsin/metabolism , Animals , Cattle , Fluorometry , Immobilized Proteins/metabolism , Immobilized Proteins/ultrastructure , Microscopy, Atomic Force , Reproducibility of Results , Solutions , Spectroscopy, Fourier Transform Infrared , Surface Properties , Trypsin/ultrastructureABSTRACT
The hydrolysis kinetics of native and denatured haemoglobin, using pepsin immobilized on aluminium oxide, was studied in order to produce hydrolysates containing bioactive peptides. Pepsin was immobilized on acidic alumina and on 2-ethanolamine- O -phosphate (2-EAOP)-modified acidic alumina. Surface charge of the two supports was determined as a function of pH. Kinetic studies were performed at 23 degrees C in 0.1 M acetate buffer, pH 4.5. At this pH, the surface charge of the two supports was almost the same. The coating of alumina by 2-EAOP only introduced a two carbon spacer between alumina surface and the reaction medium. Adsorption on the two supports of haemoglobin, haem and peptides produced in the course of hydrolyses were compared. Fixation of 2-EAOP on a pepsin-alumina complex gave hydrolysis kinetics of urea-denatured haemoglobin close to that obtained with the same amount of pepsin in solution, but with comparatively less adsorption of peptides and complete adsorption of haem. Heterogeneous hydrolyses of haemoglobin with pepsin, immobilized on functionalized alumina, resulted in the presence of VV-haemorphin-4, VV-haemorphin-7 and neokyotorphin in the supernatants without haem, the presence of which makes further purification difficult.
Subject(s)
Aluminum Oxide/chemistry , Coated Materials, Biocompatible/chemistry , Hemoglobins/chemistry , Pepsin A/chemistry , Peptides/chemical synthesis , Protein Hydrolysates/chemical synthesis , Animals , Cattle , Enzyme Activation , Enzyme Stability , Enzymes, Immobilized/chemistry , Hydrogen-Ion Concentration , Hydrolysis , Kinetics , Materials TestingABSTRACT
The kinetics of the alpha (1-23) peptide, which is the first anti-bacterial peptide to be isolated from a haemoglobin hydrolysate, was studied in the course of peptic hydrolysis at pH 4.5 and 23 degrees C in an homogeneous-phase system. A one-step reversed-phase HPLC coupled with photodiode array detector method was applied to identify and isolate this anti-bacterial peptide. The kinetics of peptide appearance were investigated in acetate buffer alone and in urea as a haemoglobin-denaturing agent. Two different mechanisms, 'one-by-one' for native haemoglobin hydrolysis and 'zipper' for denatured haemoglobin hydrolysis, were observed. Whatever the haemoglobin state, native or denatured, and whatever the hydrolytic mechanism, one-by-one or zipper, the anti-bacterial alpha (1-23) peptide is a transient peptide. To prepare the alpha (1-23) peptide it is suitable to hydrolyse haemoglobin in the presence of urea at a corrected degree of hydrolysis (DH(c)) of 13.5%. The amount of peptide produced in the presence of urea was twice as high as for the hydrolysis of native haemoglobin. The yields of alpha (1-23) peptide with respect to haemoglobin at the optimal DH(c) values were 55 and 25% respectively.
