1. Palacký University in Olomouc
Interaction of nanoparticles with amino acids and a physiologically important model protein studied by spectroscopic techniques
Karolína M. Šišková,
Dept. of Biophysics, CRH
Faculty of Science
Palacký University in Olomouc
Czech Republic
Advanced Materials & Processing, September 07-08, 2017, Edinburgh Scotland

2. Graphical abstract of this talk
Ag NP W C H R E T P
UV-Vis
and
SERS spectroscopies K F D M S Y
Au NP
Advanced Materials & Processing, September 07-08, 2017, Edinburgh Scotland

3. Ag and Au NPs
Unique optical properties
Ag NPs = Antimicrobial agents
Scholl J.A. et al. Quantum plasmon resonances of individual metallic nanoparticles. Nature, 2012, 483,
Kahraman M. et al. Fundamentals and applications of SERS-based bioanalytical sensing. Nanophotonics, 2017, 6 (5),
Rai M. et al. Silver nanoparticles: The powerful nanoweapon against multidrug-resistant bacteria. J. Appl. Microbiol. 2012, 112, 841−852
Commercially exploited
their toxicity and ecotoxicity need to be carefully evaluated
Siskova K.M. et al. Revisiting spontaneous silver nanoparticles formation: a factor influencing the determination of minimum inhibitory concentration values? AIMS Environ. Sci. 2015, 2 (3),
Their main features:
Localized surface plasmon - dependent on composition, size, shape, aggregation state
Electric double-layer - changed by surface functionalization

4. Ag and Au NPs in deionized waternm nm
UV-Vis spectra: surface plasmon extinction
Here example of isolated spherical NPs prepared by borohydride reduction
TEM images:
size and shape of NPs

5. Ag NPs Electric bilayer (EB) enveloping each NP
in aqueous solution; negative zeta potential values of NPs
If EB destroyed (e.g. adsorption of AA molecules), aggregation proceeds – observable by naked eye:

6. Interaction of Ag nanoparticles with amino acids based on UV-Vis absorption measurements
Type of NPs-AA system
0.01 mM AA
0.1 mM AA
1 mM AA
Agbh-C -
Agbh-M +
Agbh-E
Agbh-D
Agbh-R
Agbh-K
Agbh-F
Agbh-Y
Agbh-H
Agbh-W
Agbh-P
Agbh-S
Agbh-T
9 from 13 AAs interact with Ag NPs!
Functional groups of AAs play a key role;
AA concentration is also important.
Notes: final concentrations of AA are mentioned; + means aggregation observed, - no aggregation

7. Au NPs Aggregation observable by naked eye >
Recorded by UV-Vis extinction

8. Interaction of Au nanoparticles with amino acids based on UV-Vis absorption measurements
Type of NPs-AA system
0.01 mM AA
0.1 mM AA
1 mM AA
Aubh-C -
Aubh-M
Aubh-E
Aubh-D +
Aubh-R
Aubh-K
Aubh-F
Aubh-Y
Aubh-H
Aubh-W
Aubh-P
Aubh-S
Aubh-T
2 from 13 AAs interact with Au NPs!
Functional groups of AAs play a key role;
AA concentration is also important.
Notes: final concentrations of AA are mentioned; + means aggregation observed, - no aggregation

9. Surface-Enhanced Raman Scattering - principle
Not in real scale = only scheme: l
hn - light
Adsorbate molecule
Ag NP
and/or
Au NP
Oscillating dipole
Enhancement (G) of initial and Raman scattered light
G ~ E2laser* E2Raman ~ E4

10. Example of phenylalanine (at pH 7): Raman scattering vs
Example of phenylalanine (at pH 7): Raman scattering vs. SERS (using Agbh NPs)
Region of Ag-O,
Ag-S,
Ag-N vibrations
Fingerprint region
Raman shift (cm-1)

11. Interaction of Agbh NPs with AAs (1mM) based on SERS
type of NPs-AA system
exc. 532 nm signal; AA final charge in solution
at pH 7
at pH 9
at pH 10
at pH 11
Agbh-C
no; 0
no; -I
yes; -I
yes; -II
Agbh-M
yes; 0
yes, but decrease; -I x
Agbh-E
yes (decrease after 3h); -I
yes, but decrease; -II
Agbh-D
yes ; -I
Agbh-R
yes; +I
yes, but decrease; 0
Agbh-K
Agbh-F
yes (increase after 3h); 0
Agbh-Y
Agbh-H
yes, but changes; -I
Agbh-W
Agbh-P
yes (after 4h); -I
no; -II
Agbh-S
yes (after 3h); 0
(yes); -I
(yes), decrease; -I
Agbh-T
yes (after 2,5h); 0
Notes: "x" means not measured; "no"/"yes" if signal not observed and/or observed (immediately when no time mentioned or after several hours as indicated); "yes, but decrease" means the signal decreased at the particular pH in comparison to less basic pH; "(yes)" means that the signal was very weak and only three or less characteristic peaks were observed.
C interacted with AgNPs after pH increase due to HS/-S transition
Positively charged AAs (K, R) = more attractive for negatively charged AgNPs
Neutral AAs with AgNPs = good SERS signals (except C)
Negatively charged AAs (E, D, P) - the time of interaction matters.

12. Interaction of AgCitr NPs with AAs (1mM) based on SERS
Type of NPs-AA system
excitation laser line
532 nm
AgCitr-C no
AgCitr-M
AgCitr-E
AgCitr-D
yes
AgCitr-R
AgCitr-K
AgCitr-F
AgCitr-Y
AgCitr-H
AgCitr-W
AgCitr-P
AgCitr-s
Agcitr-T
Citrates take more space than borates + bound through carboxylic groups
=> NPs less reactive
Positively charged AAs = more attractive for
negatively charged AgNPs (citrates on surface)
Neutral AAs with AgCitr = no SERS signals
Notes: yes/no indicates if SERS signal observed or not
Length of AA carbon chain matters: D vs. E

13. Conclusions Outlook Evidenced that AuNPs are less reactive than AgNPs.
Species on the surface of NPs play a crutial role (citrates vs. borates).
Zeta potential value of NPs vs. charge of amino acids in solution of the particular pH is an important factor.
Ionic vs. covalent interaction between amino acids and NPs can be distinguished in SERS.
Outlook
SERS signal from different AuNPs at 633 nm excitation
Influence of pH changes on SERS spectra of AuNPs
SERS signal + Raman optical activity measurements from a physiologically important model protein, Na+/K+-ATPase
Fluorescence spectra of NPs + amino acids (namely Y, F, W)

14. Thank you for your attention!
Acknowledgement
Dr. Eva Kocisova and Assoc. Prof. Peter Mojzes
Dept. of Physics of Biomolecules, Institute of Mathematics and Physics, Charles University, Prague, Czech Republic
Assoc. Prof. Martin Kubala, Dept. of Biophysics, CRH,
Dr. Josef Kapitan, Dept. of Optics,
Faculty of Science, Palacky University in Olomouc, Czech Republic
Thank you for your attention!