Human Serum Albumin–Oligothiophene Bioconjugate: A Phototheranostic Platform for Localized Killing of Cancer Cells by Precise Light Activation

Abstract

The electronic, optical, and redox properties of thiophene-based materials have made them pivotal in nanoscience and nanotechnology. However, the exploitation of oligothiophenes in photodynamic therapy is hindered by their intrinsic hydrophobicity that lowers their biocompatibility and availability in water environments. Here, we developed human serum albumin (HSA)–oligothiophene bioconjugates that afford the use of insoluble oligothiophenes in physiological environments. UV–vis and electrophoresis proved the conjugation of the oligothiophene sensitizers to the protein. The bioconjugate is water-soluble and biocompatible, does not have any “dark toxicity”, and preserves HSA in the physiological monomeric form, as confirmed by dynamic light scattering and circular dichroism measurements. In contrast, upon irradiation with ultralow light doses, the bioconjugate efficiently produces reactive oxygen species (ROS) and leads to the complete eradication of cancer cells. Real-time monitoring of the photokilling activity of the HSA–oligothiophene bioconjugate shows that living cells “explode” upon irradiation. Photodependent and dose-dependent apoptosis is one of the primary mechanisms of cell death activated by bioconjugate irradiation. The bioconjugate is a novel theranostic platform able to generate ROS intracellularly and provide imaging through the fluorescence of the oligothiophene. It is also a real-time self-reporting system able to monitor the apoptotic process. The induced phototoxicity is strongly confined to the irradiated region, showing localized killing of cancer cells by precise light activation of the bioconjugate.

Synthesis, properties, and material hybridization of bare aromatic polymers enabled by dendrimer support

“…Human embryonic kidney 293T (HEK293T) cells were incubated with a PBS solution of the polythiophene-conjugated HSA at 37 °C. Confocal microscopic images showed fluorescence of polythiophene in the cellular membrane and cytoplasm of HEK293T cell 53 , indicating that bare polythiophene can be internalized in the cell (Fig. 6d ).…”

Fluorescent Benzothiadiazole Derivatives as Fluorescence Imaging Dyes: A Decade of New Generation Probes

“…BTD ring) in physiological environments. [179] No cytotoxicity could be noted in the dark and the BTD-conjugate was observed in its monomeric form. When the fluorescent bioconjugate was submitted to irradiation with ultralow light doses, however, ROS could be produced leading to the cancer cells (HeLa) killing.…”

“…The theranostic fluorescent platform allowed imaging monitoring (intense red emission) of the cells as a consequence of the BTD fluorophore attached to the biomolecule. [179] Lysosomal selective staining Except for red blood cells, [180] lysosomes are vesicle organelles surrounded by a single membrane made up of a lipid bilayer widely distributed in all mammalian cells. Proteins, nucleic acids, carbohydrates and lipids are biomolecules typically degraded in lysosomes.…”

“…A designed BTD derivative ( BTD‐3 a , Figure 18) was employed as the fluorescent probe to afford a fluorescent protein. The BTD‐containing human serum albumin (HSA) bioconjugate allowed the use of insoluble oligothiophenes (attached to a BTD ring) in physiological environments [179] . No cytotoxicity could be noted in the dark and the BTD‐conjugate was observed in its monomeric form.…”

EGFR-Targeted Photodynamic Therapy

“…The bioconjugation of a photosensitizer to a protein is able to bypass many of the restrictions typical of photosensitizers, such as (i) the poor water solubility or low biocompatibility, (ii) the dependency of their ability to generate ROS on the features of the physiological environment, (iii) aggregation phenomena, (iv) the non-specificity of the cellular uptake, and (v) the poor pharmacokinetic or pharmacodynamic properties [42,[88][89][90][91][92]. Bioconjugates of EGF with disulfochloride aluminum phthalocyanine [Pc(Al)] and disulfochloride cobalt phthalocyanine [Pc(Co)] were prepared, using EGF as a vector for targeted delivery of the phthalocyanines to cancer cells [93].…”