Sviluppo di immunoassay basati su reticoli long period per applicazioni bio-sensing.

Responsabili di progetto

Cosimo Trono, Palas Biswas

Accordo

INDIA - CSIR-expired - Council of Scientific and Industrial Research

Bando

CNR/CSIR 2012-2014

Dipartimento

Materiali e Dispositivi

Area tematica

Scienze fisiche e tecnologie della materia

Stato del progetto

Nuovo

Proposta di ricerca

The aim of the project is to develop an high sensitivity immunoassay based on optical fibre long period grating (LPG). The basic principle is the deposition of a biological recognition element on the optical fiber section where the long period grating is located, so as to realize a transducer capable to convert the biological interaction into a measurable signal through high accuracy refractive index measurement. The final target will be a cost effective, potentially inexpensive and portable device for qualitative and quantitative assessment of antigen-antibody interactions.
Traditionally high sensitive optical fibre-based biosensors rely on the interaction of the propagating evanescent wave with the surrounding medium. A common approach is to chemically modify the fibre surface in order to immobilize antibody molecules over the surface of a fibre. The antigen-antibody interaction must occur in some localized area in order to be detected. A variety of immobilization methods have been reported. Consequently, prior to detection, a target antigen specific to the immobilized antibody is incubated with an assisting label, such as a fluorophore and finally fluorescence signal is measured as labeled antigen specifically interacts with immobilized antibody. One disadvantage of these approaches is the need for antigen labeling, which can be both time-consuming and expensive.
Among all the existing technology platforms measuring the refractive index (RI) of a surrounding medium, those based on surface plasmon resonance (SPR) are the most diffused one, also because of the presence of SPR-based devices on the market (Biacore system, first of all); moreover, they are very attractive because they show one of the best resolution ever achieved(10-7 refractive index unit, RIU). Other well-known and fascinating technology platforms are based on the use of interferometers, implemented both on optical fibres and planar waveguides, and optical resonators which in terms of resolution can be comparable with SPR if not one order better.
In the last years LPG have been proposed as tools for chemical and biochemical sensing and many examples are described in the literature of the last years. The use of LPGs can offer some advantages compared to other ones thanks to the typical properties of optical fibres such as compactness lightweight and, from a technological point of view, to the fact that they are highly compatible with optoelectronic components/devices used for standard optical fibres, since the working wavelengths are generally in correspondence of the telecommunication windows around 1.3 and 1.5 µm. Moreover, the combination of the use of optical fibres with the fact that the signal modulation is spectrally encoded offers multiplexing and remote measurement capabilities which the other technology platforms are not able to or hardly can offer. It is also important to stress that the fact that the optical modulation of the signal is a wavelength modulation, implies that the readout is not affected by changes of the optical power due to either fibre bending or source fluctuations.
 

Obiettivi della ricerca

The target in this project will be to develop a sensor technology i.e. an immunoassay based on LPG to be used for bio-sensing applications. The specific objectives would be (i) to fabricate a robust and inexpensive sensing instrument, (ii) to develop a reliable and simple detection system, (iii) to avoid labeling of biochemical reagents and (iv), to conduct real time analysis to quantify antigen antibody reaction.
To achieve such goal the complementary competencies of the two groups involved will address the following stages:
• New high sensitivity evanescent configurations using long period grating where the sensitivity will be tailored through optimization of an overlay coating of functionalized layers. Detailed theoretical modeling of a four layer structure i.e. a fibre grating structure with overlay coating will be done to design the sensors. Special spectral or geometrical profile (e.g. tapered or twisted LPGs) will also be explored to tailor sensitivity. Mode order will be tailored to optimize evanescent interaction.
• To investigate the influence of a thin dielectric/polymeric layer on the sensitivity and selectivity of evanescent interactions will be another important part in this project work. Therefore, coating of long period gratings will be dealt thoroughly and detailed analysis will be done to quantify the effect of thickness on the sensitivity as well.
• Once the refractive index sensing is optimized, it will be worthy of developing a working prototype of the sensor so that the module can be utilized as an immunoassay. The subsequent steps therefore would be to develop an improved long period grating based flow-cell as the basic building block of the immunoassay which in turn will lead us to develop the sandwiched immunoassay to quantify the antigen antibody interaction.
• Appropriate signal readout and processing methodology to decode the wavelength signature of the sensor output will also be developed to finally implement a standalone bio-sensing system.
 

Ultimo aggiornamento: 22/05/2024