Journal of the Faculty of Engineering and Architecture of Gazi University 33:2 (2018) 675-684 Synthesis and characterization of sericin-capped gold nanoparticles Ömer Aktürk 1* , Zehra Gün Gök 1 , Taylan Memik Daş 2 , Özge Erdemli 3 1 Department of Bioengineering, Kırıkkale University, Kırıkkale, 71450, Turkey 2 Department of Mechanical Engineering, Kırıkkale University, Kırıkkale, 71450, Turkey 3 Remoderm Medical Biotechnology Ltd. Sti., Turkey Highlights: Graphical/Tabular Abstract • Synthesis of gold nanoparticles with silk sericin isolated from Bombyx mori silkworm cocoon • The role of sericin as a reducing and capping agent for the synthesis reaction • Effect of sericin concentration on gold nanoparticle properties Purpose: Herein a new “green” and simple gold nanoparticle (AuNP) synthesis method was presented as an alternative to existing similar strategies. The effect of sericin concentration on synthesis reaction and on shape and size distribution of AuNPs, as well as on the aqueous stability of AuNPs was investigated in order to assess the potential ability of these AuNPs for future biomedical applications such as nanocarrier systems for therapeutics and so on. Theory and Methods: Sericin was isolated from B. mori silkworm cocoon by simply boiling cocoon fragments in de-ionized H2 O (0.01 M Na 2 CO3 ) for 30 min and then dialyzing the resulted sericin solution for 2 days. 10 mL of different sericin solutions (0.25, 0.5, 1% w/v) were mixed with equal volumes of gold salt (1 mM HAuCl 4 ·3H2 O) to obtain test groups (S-AuNP0.25, S-AuNP0.5, S-AuNP1) and exposed to UVC light for 1-day duration until a red ruby-like color was formed (Citrate-AuNP control group was synthesized similarly). AuNP synthesis was confirmed by spectral scans between 400-600 nm wavelength in UV-vis spectroscopy. Stability of AuNPs in different ionic strength media was characterized with similar spectral scans and zeta potential measurements were made as well. The size distribution and shape of AuNPs were examined with TEM micrographs. Results: Successful AuNP formation was clearly shown by UV-Vis spectral scans with surface plasmon resonance (SPR) peaks emerging at about 520 nm wavelengths. Adding sericin increased the negative zeta potentials of AuNPs and also suggested more stable nanoparticles in aqueous environment. S-AuNP1 and S-AuNP0.5 groups were better than S-AuNP0.25 and Citrate-AuNP groups in terms of stability. By visual observation, the reaction rate was slower in S-AuNP1 than S-AuNP0.5. Sericin also decreased AuNP size (< 10 nm) significantly and made the size distribution more homogenous. Conclusion: Sericin-capped gold nanoparticles (especially S-AuNP0.5 group with its high stability in aqueous environment and uniform size distribution) could be a promising candidate for future biomedical applications, such as nanocarrier systems for therapeutics or being as a bioactive agent alone. In vitro biocompatibility and potential biofunctions (such as antimicrobial, antioxidant features and so on) will further be assessed in the future for testing the potential applicability of these nanoparticles. Keywords: • Gold nanoparticle • Bombyx mori silk worm • Sericin • Surface plasmon resonance Article Info: Received: 13.12.2016 Accepted: 20.06.2017 DOI: 10.17341/gazimmfd.416377 Acknowledgement: The study was financially supported by the Kırıkkale University Scientific Research Projects (BAP) Coordination Unit under the project no 2016/141. We thank Kırıkkale University BAP Coordination Unit for their support. Correspondence: Author: Ömer Aktürk e-mail: omerakturk@kku.edu.tr phone: +903183574242- 1245