Abstract
A high-throughput label-free resonant waveguide grating biosensor, the Epic BenchTop, was utilized to in situ monitor the adhesion process of cancer cells on Arg-Gly-Asp tripeptide displaying biomimetic polymer surfaces. Using highly adherent human cervical adenocarcinoma (HeLa) cells as a model system, cell adhesion kinetic data with outstanding temporal resolution were obtained. We found that pre-exposing the cells to various concentrations of the main extract of green tea, the (−)-epigallocatechin gallate (EGCG), largely affected the temporal evolution of the adhesion process. For unexposed and low dosed cells, sigmoid shaped spreading kinetics was recorded. Higher dose of EGCG resulted in a complete absence of the sigmoidal character, and displayed adsorption-like kinetics. By using the first derivatives of the kinetic curves, a simple model was developed to quantify the sigmoidal character and the transition from sigmoidal to adsorption-like kinetics. The calculations showed that the transition happened at EGCG concentration of around 60 μg/mL. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide end-point assay, we concluded that EGCG is cytostatic but not cytotoxic. The effect of EGCG was also characterized by flow cytometry. We concluded that, using the introduced label-free methodology, the shape of the cell adhesion kinetic curves can be used to quantify in vitro cell viability in a fast, cost-effective, and highly sensitive manner.
Highlights
Natural compounds are becoming more and more popular in biomedicine, especially in cancer treatment and to develop novel antimicrobial agents.[1−4] Tea catechins, especially (−)-epigallocatechin gallate (EGCG), have been shown to have various health benefits, for example, anti-metastasis, anticancer, anti-inflammatory, and antioxidant properties, and can prevent cardiovascular disease as well.[5−8] EGCG is one of the most studied active substances, and many studies observed its effects on several cancer and normal cell types, and in animal models.[4]
In vitro effect of EGCG on cellular viability was accessed by three different methods using human cervical adenocarcinoma (HeLa) cells: (i) to analyze realtime cell adhesion kinetics, (ii) to determine metabolic activity using colorimetric MTT assay, and (iii) to quantify dead or dying cells by cytofluorometry with PI staining
Adhesion Kinetics of EGCG Pre-Exposed Cells Recorded by the Optical Biosensor
Summary
Natural compounds are becoming more and more popular in biomedicine, especially in cancer treatment and to develop novel antimicrobial agents.[1−4] Tea catechins, especially (−)-epigallocatechin gallate (EGCG), have been shown to have various health benefits, for example, anti-metastasis, anticancer, anti-inflammatory, and antioxidant properties, and can prevent cardiovascular disease as well.[5−8] EGCG is one of the most studied active substances, and many studies observed its effects on several cancer and normal cell types, and in animal models.[4]. Determination of cell viability is a critical step in screening the efficacy of compounds, when evaluating the response to cytotoxic moiety. Flow cytometry is a sensitive and mainstream method to determine compound-induced cytotoxic effects and cell death. The main advantage of the method allows the analysis on a per-cell basis using fluorescent dyes to enter viable or dead cells.
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