MSc in Biochemistry
Dissertation Project –2016/2017
Student´s Name:
Student email address:
No:
Supervisor(s) Name: Ermelinda Maçôas and Carla Santos
Supervisor(s) email address: [email protected],
[email protected]
Lab/Institution: Centro de Química-Física Molecular (http://cqfm.tecnico.ulisboa.pt/), Instituto
Superior Técnico, Universidade de Lisboa
Elo de Ligação: César Laia
TITLE: GO Lights Up Gasotransmitters
BACKGROUND
Current methods of detection of gasotransmitters (laser sensor-infrared absorption,
electrochemical assays, gas chromatography and others) are difficult to employ in realtime detection of physiological levels inside living cells in a noninvasive manner.
Fluorescence sensing is a powerful technique to accomplish this goal. Nonlinear, twophoton, excitation has well-known advantages in fluorescence based biomedical
imaging and biosensing over conventional linear excitation methods, which include low
background signal and low phototoxicity, deep penetration depth in scattering tissues
and reduced photobleaching.1,2 graphene oxide quantum dots (GOQD) are now
emerging as promising two-photon fluorophores due to their unique properties such as
water solubility, biocompatibility and photostability alongside their exceptional twophoton absorption cross-sections and high emission quantum yields.3,4,5 Exploration of
the two-photon excitation and emission properties of this type of materials for imaging
and sensing is still very much on its infancy. The first report showing that nonlinear
excitation of GOQDs can be valuable for 3D-imaging in biological and biomedical
applications was published in 2013.5 As of today, there have been no reports on the use
of the nonlinear emission properties of modified GOQD for sensing.
OBJECTIVE
The aim of the project is to prepare GOQD to be used in the design of water soluble,
nonlinear turn-on probes for 3D-mapping of the most important signaling
gasotransmiter (nitrous oxide, carbon monoxide and hydrogen sulfite) using optical
microscopy. GOQD are monolayer graphene oxide sheets of lateral dimensions below 4
nm (Figure 1A). The strategy is to couple the water solubility, cell membrane
penetration ability and exceptionally high nonlinear emission and photostability of
GOQD with the sensitivity and selectivity of optimized molecular units that can act as
modulators of the fluorescence intensity of GOQD (Figure 1B).
Figure 1. A) TEM image of GOQD with a size distribution centered at 2 nm, B) Design
strategy for the nonlinear gasotransmitter probes composed of two units, the nonlinear
fluorescence signal transducer (GOQD) and the fluorescence modulator (FM, molecule with
a reactive center).
PROJECT DESCRIPTION
The work plan can be divided in 4 tasks:
1) Synthesis of GOQD using TOP DOWN methods, in which GO with different
properties and different N-sources will be used.
2) Characterization of the GOQD in terms of size and shape, composition and
photophysics.
3) Coupling of selected GOQD with the molecular probes having terminal amino
groups, after activation of the carboxylic groups in the GOQD.
4) Characterization of the sensing ability in solution and in cellula.
This work plan is rooted on an ongoing project in our research unit. The student will
be engaged in a multidisciplinary team of researchers that will provide the opportunity
to build a solid knowledge on both the modification of carbon based material and the
characterization of nanostructured material using spectroscopic methods (UV-Vis,
FTIR, micro-Raman and XPS), dynamic light scattering (DLS), and various
microscopic techniques (electron, optical and atomic force microscopy).
References
(1)
(2)
(3)
(4)
(5)
Zipfel, W. R.; Williams, R. M.; Webb, W. W. Nat Biotechnol 2003, 21, 1368.
Guo, L.; Wong, M. S. Adv. Mat. 2014, 26, 5400.
Li, J. L.; Tang, B.; Yuan, B.; Sun, L.; Wang, X. G. Biomaterials 2013, 34, 9519.
Miao, P.; Han, K.; Tang, Y. G.; Wang, B. D.; Lin, T.; Cheng, W. B. Nanoscale 2015, 7, 1586.
Liu, Q.; Guo, B. D.; Rao, Z. Y.; Zhang, B. H.; Gong, J. R. Nano Lett. 2013, 13, 2436.
Timeline
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