OPTOADVANCE, makes use of nano and bio technologies in an experimental manner in the research laboratories in order to gain an answer from the optical fibre elements. It wants to propose to a market, through appropriate demonstrators, innovative applications of biosensors for the environmental protection and for the security in the industrial field and other fields of interest.
A biosensor is an analytical gadget that converts a biological reaction in to a signal, of different types (electrical, calorimetrical,, magnetic, micromechanical, piezoelectric, photonic, etc.) for the purpose to determine the concentration of a certain substance. A correct definition for biosensor is the following: “an analytical device that includes biological material integrated or associated with a physical-chemical transducer or with a micro system transduction. The transducer could be optical, electrochemical, thermo metrical, piezoelectric and magnetic or micromechanical”.
In few words, a biosensor is characterised by the fact that uses a biological system. The term “biosensor” nevertheless, is used in more ample meaning to indicate sensors that are able to determine the concentration of chemical substances. (i.e. blood pressure, pH etc.) even though they don’t use a direct biological system. In this last exception, the number of devices to be taken in consideration, increases in excess and takes valuations and comparisons completely forward. In fact, the majority of these devices should be categorized in the physic or chemical parameters and not numbered amid the sensors.
However, as to regard concerning a non comprehensive description of the biosensors based on the usage of optical fibres transducers with a long-period grating which is the technology used by OPTOADVANCE, one observes as follows:
The biosensor is an optical devise made as a whole from a guide of an optical wave having core and cladding, preferably of monomial optical fibre, where at least in one of its section, a long period grading has been transcribed (Long Period Grating (LPG) by one or more thin layers of materials deposited on the cladding of the optical fibre. The said material layers is deposited at least in part, by the dip coating technique through the fibre where the gratings are present and where at least one layer close to the cladding, has an index of higher refraction than the cladding itself. The width of the said materials stratification is chosen in a regular way and the device functioning of the same, in a modal transaction.
Devices of this type can have multiple uses according to the chemical-physical proprieties of the material used to achieve stratification. It can be used particularly as biochemical, chemical, modulator, and optical switch sensor. In the example of a biochemical sensor, the external surface of the stratification materials is modified through the immobilization of some known elements bimolecular (proteins, antibodies, enzymes, peptides, whole cells, microorganism, etc.). The biosensor made this way is placed to a sample to be analyzed and it has a recognised bimolecular reaction between the immobilized elements of the surface of the device and the substance in which one wants to identify the presence and to measure its concentration. Such reaction of identification causes a change in the optical properties (for example the refraction index) of the covering layer of the immediate circumstances of the biosensor surface. At least one of the optical characteristics of the biosensor to be analysed, is compared with means of reference and utilized for detection.
In the example of the chemical sensor, the materials stratification is made up with at least of a material capable to absorb a certain chemical substance from the external ambience and to concentrate it in its own volume and in a modality usually indicated as micro extraction in a solid phase (Solid Phase Micro Extraction SPME). The absorption of such chemical substance provokes a change in the chemical-physical of the layer chemo-sensitive that is reflected in a change of his width and/ or refraction index. At least one of the optical characteristics of the chemical sensor absorbed in the middle to be analysed, is compared with means of reference and utilized for detection.
In the example of the optical modulator, the material stratification is made up by at least a material whose characteristics (width and or refraction index) are sensitive to an applied electromagnetic field. Can be used materials with electro optical, piezoelectric, magneto restrictive and photo chromic characteristics. The appliance of an electromagnetic field modulates the optical characteristics of the device and these can be used to modulate the optical signal transmitted.
The most popular example of the biosensor most used, is the glucometer, an instrument for measuring the glycaemia, costing only few Euros, and largely used by diabetics. Practically, the amperometric sensors based on the enzymes for measuring glucose are the most commercially used. The ones to measure cholesterol closely follow.
The use of an optical fibre as a probe or for the biosensors detection, is taking foot because of the advantages of the optical fibres, especially the one of the light transference at great distance. It has the ability to capture the light emitted by the targets and the immunity to the electrical and magnetic interferences. A typical optical biosensor uses absorbance measurements to determine a change in the analytes concentration that take up the light of certain wave length. The light is transmitted through an optical fibre as a sample; the quantity of light which has been absorbed by the analyte is then detected by the same fibre or by a second fibre. The biological material is then immobilised at the extremity of the optical fibre where the analyte is detected. Furthermore, one ha to remember the bioluminescence: The basal principal of the bioluminescence is the same as the one of chemiluminiscence, when, some molecules, conditioned by a chemical reaction by an electronic exhilaration, they emit part of the energy in the form of light radiation (photons), returning to its basic state.
To who is the biosensor is directed?
In the case of the biosensor produced by OPTOADVANCE, the purchaser is certainly a professional person working in a hospital or in a research laboratory and he could find that by using a LPG sensor is a lot more advantageous than using other gadgets which are more costly and sophisticated.
The biosensor at LPG, with the whole measuring device, is the most economic in the market for his type, is about in the order of ten thousand Euros (15K-20K). Obviously in a serial production the cost would be lower.
Every LPG has a relatively high price (about 200 Euros) and its production is handmade and not in an industrial way. Therefore, the first problem to solve is the one to define the LPG characteristics that one wants to utilize and industrialize its production. This has the purpose to keep a lower price, to increase the quantity and make deliveries in good time.
This means to place other phases in the LPG production beyond the simple writing in the fibre (i.e. thin fibres characteristics able to interact with the substance), and to focus some simple biochemical protocols that can be used by the operator before using of the probe.