Abstract

A comparative study was performed for the effect of trehalose on two photo bioconjugates of R-Phycoerythrin (PE) with Nanoparticles (NPs) of similar size but different nature. Light-sensitive bioconjugates of PE with Ag⁰ and CdS NPs (Ag⁰.PE and CdS.PE) show promise for recording intermolecular interactions, cancer theranostics and drug delivery due to theiique optical properties, ability of ROS generation, electrical activity, and small size. Bioconjugates were obtained by synthesizing Ag⁰ and CdS NPs in the tunnel cavities of R-phycoerythrin, a photosynthetic pigment of red algae, as a natural resource. The current study was undertaken to determine the influence of trehalose, a known protein stabilizer, on the properties of Ag⁰.PE and CdS.PE bioconjugates. The results indicate that the fluorescence intensity of both bioconjugates increases when excited by visible light. However, the mechanisms of their fluorescence enhancement are different. The intensity of CdS.PE fluorescence excited at 280nm decreases in the presence of trehalose by about half, while the fluorescence of Ag⁰.PE remains unchanged. The ambiguous effect of trehalose on the UV-excited fluorescence of Ag⁰.PE and CdS.PE bioconjugates is due to the unequal nature of NPs (metallic and semiconducting) is discussed. Trehalose has no effect on the size of NPs in both bioconjugates. Trehalose inhibits the ability of R-phycoerythrin to photosensitize the electron transfer. It was demonstrated that trehalose can be successfully used in rapidly developing nanotechnology based on photo bioconjugates as a promising source of multifunctional biomaterials and highly sensitive optical biosensor systems.

Keywords: Nanotechnology; Photoactive bioconjugates; R-phycoerythrin; Silver nanoparticles; Semiconductor nanoparticles

Abbreviations:

PE: R-phycoerythrin; NPs: Nanoparticles; Ag⁰.PE: Bioconjugate of R-phycoerythrin with Ag⁰ nanoparticle; CdS.PE: Bioconjugate of R-phycoerythrin with CdS nanoparticle; ROS: Reactive Oxygen Species; Trp: Tryptophan