International Journal of Peptide Research and Therapeutics
Investigating the Structural Stability of RADA16-I Peptide Conjugated
to Gold Nanoparticles
· Hadis Zarei
· Azadeh Azizi
· Mansooreh Sadat Seyedkarimi
Accepted: 29 May 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
RADA 16-I is an amphiphilic peptide which can form macroscopic scaﬀolds through self-assembly and has found many appli-
cations in tissue regeneration and hemostasis. It is still unclear in which conditions this peptide can perform self-assembly
more eﬀectively while maintaining its stability. Interaction between peptides and gold surfaces has been increasingly regarded
for biotechnological applications. In order to better understand the eﬀect of this conjugation on the application of RADA16-I,
properties of peptide-modiﬁed gold nanoparticles were studied using circular dichroism, DLS, DSC and UV–Visible imaging
to monitor changes in conformation of the conjugated peptide. The bioinformatics studies showed that the peptides exhibit
a predominantly helical structure as monomer. UV–Visible spectrum of the gold nanoparticles showed an absorption peak
at around 520 nm. Spectral and DLS analyses indicated precision of conjugation and the stronger tendency of conjugated
peptide, as compared to its unconjugated form, toward aggregation or self-assembly. CD analysis showed a slight increase
in β-strands of the conjugated peptides. Furthermore, DSC data suggested enthalpy-driven nature of the conjugation process
minor changes in peptide stability. These ﬁndings can help researchers in the design of future nano-biomaterials, such as
biosensors, based on β-sheets, scaﬀolds, and gold nanoparticles. The present study may serve as a scientiﬁc basis for improv-
ing eﬃcacy and application of peptide as hemostat.
Keywords Aggregation · Biomaterial · Nanoparticles · Self-assembly · Stability · Zeta potential
In biotechnology, self-assembling nanopeptides comprise a
class of biomaterials that may spontaneously assemble into
ordered macroscopic structures (Zhao and Zhang 2007).
Detailed analysis of self-assembling capability of amphiphi-
lic peptides and their modiﬁcation has been widely regarded
in medical engineering, biosensor applications and nano-
biomaterial design (Zhang et al. 2002; Yang et al. 2009).
For example, the 16-mer self-assembled peptide, RADARA-
DARADARADA (RADA16-I), was designed and synthe-
sized by mimicking the amphiphilic segment of EAEAKA-
KAEAEAKAKA (EAKA 16-II) of the naturally occurring
yeast Zuotin protein. It is composed of particular repeated
arrangements of hydrophobic (Ala) and hydrophilic (Arg
and Asp) residues. RADA 16-I has a high tendency toward
self-assembly into highly ordered stable ﬁbrils depending on
diﬀerent conditions, making it useful as hemostat and also
for cell growth and adherence, drug delivery and biosensor
applications (Sun et al. 2016). Moreover, researchers are
consistently attempting to undertake modiﬁcations to control
stability and form of ﬁbril dispersions to assemble them into
desired highly ordered structures which are useful for further
applications (Aggeli et al. 2003).
Gold nanoparticles (AuNPs) might be incorporated into
scaﬀolds to treat wounds as a novel strategy (Cozad et al.
2011). The unique properties of AuNPs involve enhanced
mechanical stability and resistance against enzymatic deg-
radation when incorporated into tissue scaﬀolds (Grant
et al. 2014), enhanced biocompatibility (Cui et al. 2014;
Hung et al. 2014) and anti-inﬂammatory (Chen et al. 2013).
AuNPs are commonly used for protein conjugation because
of their good biocompatibility, easily modiﬁable chemistry,
antibacterial activity, and high protein loading (Secundo
2013; Shemetov et al. 2012).
While most research has focused on the RADA16-I self-
assembling mechanisms, to the best of our knowledge, no
* Asieh Aramvash
Malek-Ashtar University of Technology, P.O.
Box 16765-3454, Tehran, Iran