Self-assembled complexes of multibranched gold nanoparticles with porphyrins used in photodynamic therapy Spectral and structural characterization

ALEJANDRO, ZUNIGA and ARYANE, TOFANELLO and CARLOS, E. DE CASTRO and ERICA, G. A. MIRANDA and FERNANDO, C. GIACOMELLI and ISELI, L. NANTES and JULIANA, C. ARAUJO-CHAVES (2015) Self-assembled complexes of multibranched gold nanoparticles with porphyrins used in photodynamic therapy Spectral and structural characterization. In: Second International Conference on Advances in Bio-Informatics and Environmental Engineering - ICABEE 2015, 18 - 19 April, 2015, Rome, Italy.

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The size and form of gold nanoparticles are crucial for the material properties. Particularly, anisotropic nanostructures are of particular interest because the capacity to enhance electromagnetic field upon irradiation for application in Surface Enhanced Raman Scattering spectroscopy and imaging. In the present study, biocompatible multibranched gold nanoparticles (MGNP) were synthesized by the one pot method using the piperazine moiety of HEPES buffer as reducing and stabilizing agent. The synthesis of MGNP was carried out at pH 3, 7 and 10 by using 0.2, 1.0, 2.5, 5.0 and 25.0 mM HEPES and phosphate buffer. The formation of stable MGNP in high yield was obtained using 2.5 mM HEPES buffer at pH values of 7.0 and 10.0 as evidenced by the deep blue color and the presence of red shifted resonance plasmon bands. The MGNP obtained in these conditions were used for association with cationic and anionic meso-tetrakis porphyrins, TMPyP (5, 10, 15, 20 tetrakis(1-metyl-4-pyridinio) porphyrin tetra(p-toluenesulfonate) and TPPS4 ((4, 4’, 4’’, 4’’’-(porphyrine-5, 10, 15, 20 tetrayl) tetrakis benzenesulfonic acid. These porphyrins were the choice because the well-known application in photodynamic therapy (PDT). TMPyP and TPPS4 bound to the MGNPs as evidenced by changes of zeta potential (ζ). MGNP exhibited ζ potential of -35 mV. The ζ potential increased to -15 mV in the presence of TMPyP and decreased to -37 mV in the presence of TPPS4. Electronic absorption spectra analysis revealed that TMPyP redshifted the resonance plasmon band of MGNP suggesting the formation of elongated aggregates. TPPS4 did not promote changes in the plasmon resonance band of MGNP. Fluorescence spectroscopy analysis revealed changes in the fluorescence spectra of both MGNP and porphyrins. TMPyP exhibited a 50% quenched emission band. TPPS4 in homogeneous media when excited at 433 nm presented a fluorescence band peaking at 675 nm. The association with MGNP promoted a split of the TPPS4 fluorescence band with peaks at 643 and 707 nm suggestive of the conversion of the acidic porphyrin (H2TPPS4) to the desprotonated form TPPS4.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: multibranched gold nanoparticles, green synthesis, plasmonic band, HEPES buffer, zeta potential, fluorescence.
Depositing User: Mr. John Steve
Date Deposited: 02 May 2019 11:17
Last Modified: 02 May 2019 11:17

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