FT-IR characterization of a theranostic nanoprobe for photodynamic therapy and epidermal growth factor receptor targets

Abstract Photodynamic Therapy (PDT) is an effective cancer treatment method based on light-activation of a photosensitizer in the presence of cellular oxygen. In an effort to develop a novel PDT agent for breast cancer treatment we report on the synthesis and characterization of a bifunctional theranostic nanoprobe; possessing both a photosensitizer agent (Chlorin e6) and tumor targeting agent – an Epidermal Growth Factor (EGF) complex which targets the EGF receptor. It’s effectiveness in arresting cancer cell growth was tested using the breast cancer cell line MDA-MB-468. FT-IR analysis confirms that carbodiimide chemistry was effective in creating covalent bonded complexes between the photosensitizer Chlorin e6 (Ce6) and cysteamine, and the EGF and α-lipoic acid, which exhibit excellent affinity for gold nanoparticles (AuNPs). In particular, for the Ce6-cysteamine complex FT-IR analysis shows peaks with significant increase in intensity at 1713, 1542, 2227 cm −1 and a decrease at 941 cm −1 and for the EGF-α-lipoic acid complex there are significant decreases in intensity at 1708, 1073, 947 cm −1 and increases at 1542, 1680, 1108 cm −1 . These changes are consistent with the creation of amide bonds, loss of carboxylic acid, and modification of the N H and C O bonds. Conjugation of these complexes to AuNPs was confirmed by UV–vis and Dynamic Light Scattering experiments. MDA-MB-468 cells treated with the bifunctional nanoprobe exhibited similar cell death and mitochondrial activity at 10-fold smaller Ce6 concentrations when bound to AuNPs compared with free Ce6. In addition only half the exposure time was needed to achieve these effects compared with unbound Ce6.