Mass spectrometric study of magnetic gold-cobalt nanocomposite and applications for detection of
                                           biomolecules

                                           Mayuri Ausekar

                                    E-mail: 441691@mail.muni.cz

Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5/A14, 625 00 Brno, Czech
                                             Republic

Gold nanoparticles are used in biomedicine since many years due to their unique properties and
applications [1]. Recently, magnetic bimetallic Au nanoparticles/nanocomposites with the
combination of magnetic Fe (or iron oxide) and Co nanomaterials were prepared. These materials are
mostly studied because, Au confers biocompatibility, optical properties and benefits of easy
functionalization, while Fe or Co gives easy magnetic control due to their magnetic properties [2].
The use of bimetallic nanoparticles/nanocomposites Au-Fe in detection of small biomolecules via
MALDI has also been reported [3].

Laser Desorption Ionization (LDI) Time-of-Flight Mass Spectrometry (TOFMS) has proven a potential
analytical technique to characterize nanoparticles and their utilization for biomolecule detection
[4]. Consequently, we have used this method to generate and study the clusters formed via
interaction of laser pulses with different Au-Co nanomaterials as a precursor.

The Au-Co nanocomposites were prepared by different methods. The products were examined via LDI TOF
MS in positive ion mode. In case of the mixture of CoSO[4] and gold nanoparticles, the laser
ablation produces several positively charged clusters (Au[m]^+, Co[n]^+,^ and Au[m]Co[n]^+). A
series of gold clusters Au[m]^+ (m =1-11) was also detected. The nanocomposites prepared in two
different methods were used for the detection of standard peptide mixtures. The results obtained
using Au-Co enriched α-cyno-4-hydroxy cinnamic acid (CHCA) as a matrix show increased peak
intensity for most of the peptides as compared to only use of CHCA as a matrix.

Concluding, LDI TOF MS can be used with advantage to examine various inorganic nanomaterials,
clusters, and/or nanocomposites. The results obtained are helpful for understanding the processes
proceeding in plasma plume due to interaction of laser pulses with solid-state materials. The
produced Au-Co nanocomposites can be used to improve ionization of many other biomolecules via
nanoparticles assisted LDI/surface assisted LDI (NALDI, SALDI) methods.

References

[1] H-H Wang, C-H Su, Y-J Wu, C-A J. Lin, C-H Lee, J-L Shen, W-H Chan, W. H. Chang, H-I Yeh. Int.
J. Gerontol. 2012, 6, 1-4.

[2] Y. Bao, K. M. Krishnan. J. Magn. Magn. Mater. 2005, 293, 15-19.

[3] R. M. Mawale, M. V. Ausekar, D. Pavliňák, O. Galmiz, P. Kubáček, J. Havel. J. Am. Soc. Mass
Spectrom. 2017, 28, 215-223.

Acknowledgements

This work was supported by Czech Science Foundation (Project No. GA18-03823S).

                        PhD Thesis supervisor: Prof. Dr. Josef Havel, DrSc.