Preparation of peptide-based nanomaterials and investigation of their cellular interactions

Traditional treatment methods for cancer diseases encounter disadvantages such as tumor invasion, the spread of tumors to different tissues, and multiple drug resistance. Therefore, developing new methods is of great importance. In the field of gene therapy, there is a growing interest in peptide-based structures that stand out in the production of nanomaterials with advantages such as self-regulation, biocompatibility, and biodegradability, thanks to their molecular recognition functions. In the scope of this thesis, novel nanomaterials (NM) based on diphenylalanine amide (FFA), which are self-regulating in terms of size and balanced surface charge and are novel for carrying small interfering RNA (siRNA) as a gene silencer to cancer cells, were synthesized. After the synthesis of FFA-NMs, they were decorated with Ca2+ ions. Characterization studies included analysis using scanning electron microscopy (SEM), transmission electron microscopy (TEM), mass spectrometry (MS), dynamic light scattering (DLS), Zeta potential measurement, Image J size assessment, and Fourier-transform infrared (FTIR) spectroscopy. To evaluate their potential in forming coronas with biological molecules, the synthesized FFA and Ca2+- FFA-NMs were interacted with HSA, IgG, and DNA molecules. The corona layer formed on the surface of NMs was assessed both by DLS and spectrophotometrically. Some findings obtained after conducting cell toxicity and internalization tests can be summarized as follows: The average size distribution of FFA-NMs, which was 87.93 nm, had a surface charge of -20.1 mV, while after Ca2+ decoration, it became +9.3 mV. Surface charge distribution of Ca2+-FFA-NMs occurred as -7.6, -3.7, and -9.7 mV, respectively, depending on the corona structures they formed with HSA, IgG, and DNA molecules. No toxicity was observed after the 24-hour interaction of Ca2+-FFA-NMs with HeLa and HT29 cell lines. Complexes formed by different siRNA types (Mcl-1 and Bcl-xL) with Ca2+-FFA-NMs were internalized into HeLa and HT29 cell lines, leading to an approximately 36% decrease in their viabilities. The FFA-based NMs used in this study are considered as biocompatible and are believed to hold promise for future advanced studies aimed at increasing the internalization degree of silencing siRNAs into cancer cells.