Joint research project

Development of innovative FLUOrescent sensors based on polymeric NanoFABrics loaded with xanthene dyes (FLUO-NanoFAB)

Project leaders
Barbara Ventura, Rania Morsi
EGITTO - ASRT - Academy of Scientific Research and Technology
CNR-ASRT 2016-2017
Chemical sciences and materials technology
Thematic area
Chemical sciences and materials technology
Status of the project

Research proposal

The development of reliable, fast, low-cost and easy-to-use sensing systems is an emerging need in many fields, such as security, environmental and food monitoring and medical diagnostics.[1]
Sensors based on fluorescence detection have been extensively investigated particularly in biomedical applications.[2] The transduction mechanisms rely essentially on changes in fluorescence intensity, spectrum or lifetime upon target binding.
Among the fluorophores developed as sensors up to now, the xanthene class (including rhodamines and fluoresceins) is considered one of the most promising due the excellent optical properties of these dyes (high extinction coefficients and quantum yields, good photostability).[3] The sensing mechanism is based on their existence in two forms: a non-fluorescent lactone form and a strongly fluorescent opened form. The ring opening induced by the binding of a metal ion thus produces a fluorescence enhancement. Indeed, spirocyclic derivatives of rhodamine and fluorescein have been explored as sensors for several metal ions (i.e. Cu2+, Hg2+, Fe3+, Cr2+, Pb2+).[3] Still the lack of selectivity and their primary use in solution limit their practical applications.
Optical sensing agents are frequently exploited in an embedded form, in polymer membranes or thin films. These composites display analyte-dependent optical properties such as reflectance or fluorescence. Such sensors mostly provide enhanced stability, reversibility and sensitivity with respect to solution based sensing.[4] However, the development of new technologies toward highly sensitive and selective detection techniques is very challenging. The use of polymeric nanomaterials is expected to offer enhanced results compared to sensing films prepared with the same composition.
Electrospinnig has recently gained much attention as a unique technique to fabricate high surface area nanofibrous materials. In electrospinning, a polymer solution is subjected to a voltage that forces it to form a cone, because of the coupled effects of electrostatic repulsion within the charged droplet and attraction to a grounded electrode of opposite polarity. At a certain value of the applied electric field the charge overcomes the surface tension and a fine jet is ejected from the tip of the cone. These jets dry to form very thin polymer nanofibers collected on a substrate.[5] The diameter of the electrospun fibers depends on the polymer nature, its solution properties and other experimental conditions such as temperature, flow rate, voltage, distance between polymer solution and substrate and humidity. The produced electrospun nanofibrous materials have a large functional surface area and this is expected to provide the potential for unusually high sensitivity and fast response in sensing applications.

In this project we propose an innovative approach to the development of fluorescent sensors based on electrospun fiber materials loaded with xanthene dyes. The key point is the creation of photoresponsive nanofibers to be exploited for the creation of sensitive, selective and easy-to-use sensing devices for metal cations. We target preferentially two ions: Cu2+ and Hg2+. The former metal ion is of vital importance and under overloading conditions in the body it exhibits toxicity, being implied in neurodegenerative diseases such as Alzheimer's and Wilson's diseases;[6] the latter is one of the most prevalent toxic metals in the environment and its efficient detection in drinking and waste water is a great societal challenge.[7]
The success of the project relies on the combination of the complementary skills of Dr. Morsi's and Dr. Ventura's groups. The team lead by Dr. Morsi has an integrated experience in the fabrication of polymeric nanomaterials, nanofibers by electrospinning technique and polymer-based nanocomposites, detection of heavy metal ions in water by atomic absorption methods as well as sensor preparation and sensing of water contaminants. The team lead by Dr. Ventura has an established experience in the photophysical characterization of organic and inorganic luminescent materials and in the study of photoactive host-guest and supramolecular systems. Technical expertise covers steady-state and time-resolved optical absorption and emission spectroscopy, laser based transient techniques and confocal microscopy.

The project will be realized following a sequence of tasks (described in details in the yearly activity):
- Task 1: Choice of the dyes and full photophysical characterization;
- Task 2: Loading of the dyes onto polymeric matrix;
- Task 3: Fabrication of the composites as nanofibers and thin films;
- Task 4: Physical, mechanical, optical and morphological characterization;
- Task 5: Assessment of the sensing activity.

[1] A. P. F. Turner, Chem. Soc. Rev. 2013, 42, 3184.
[2] a) Y. Suzuki, K. Yokoyama, Biosensors 2015, 5, 337. b) L. Basabe-Desmonts, D. N. Reinhoudt, M. Crego-Calama, Chem. Soc. Rev. 2007, 36, 993.
[3] X. Chen, T. Pradhan, F. Wang, J. S. Kim, J. Yoon, Chem. Rev. 2012, 112, 1910.
[4] X. Xu, S. Chen, Q. Wu, J. Colloid Interface Sci. 2012, 385, 193.
[5] M. Z. Elsabee, H. F. Naguib, R. E. Morsi, Mat. Sci. Eng. C 2012, 32 (7), 1711.
[6] T. Hirayama, G. C. Van de Bittner, L. W. Gray, S. Lutsenko, C. J. Chang, PNAS, 2012, 109(7), 2228.
[7] S. Yoon, A. E. Albers, A. P. Wong, C. J. Chang, J. Am. Chem. Soc. 2005, 127, 16030.

Research goals

The key project concept of FLUO-NanoFAB is to combine electrospun nanofiber materials with fluorescent sensors for novel metal ion sensing technology. This approach is expected to guarantee: i) advanced sensing performances with respect to the state-of-the-art, due to the fact that the polymeric fibrous matrix has a large functional surface area; ii) high mechanical and thermal stability of the composite; iii) processability of the produced nanofibers into advanced textiles.

FLUO-NanoFAB pursues the three following primary objectives:
1) Development of innovative hybrid polymeric/monomeric organic materials;
2) Development of novel efficient fluorescent sensors for metal cations, in particular Cu2+ and Hg2+;
3) Applications of the produced materials in diagnostics and environmental monitoring.

This project will open an important scientific and technological collaboration network between Italy and Egypt that will continue also after the closure of the project. Moreover, the proposed multidisciplinary research is expected to have impact on the Mediterranean science base and to offer appealing opportunities for interaction with the industry, since it addresses innovative solutions for some important societal problems.

Last update: 19/08/2022