- The full article entitled “Visualizing Dynamics of Membrane Rafts on Live Cells” can now be found at the Sciences Advances website (Sci. Adv. 2025, 11, eadv7001)
- Authors: Hsiang-Ling Chuang, Yu-Chen Fa, Kum-Yi Cheng, Er-Chien Horng, Yi-Te Chou, Richard P. Cheng,* Li-Chen Wu,* Ja-an Annie Ho,* Chun-hsien Chen*
Do membrane rafts truly exist on cell membranes? Since the concept was first proposed by Simons and Ikonen in 1997, this question has remained a long-standing and actively debated topic. Membrane rafts are believed to serve as “gateways” through which cells receive external signals, enabling spatial organization of cellular processes. They are highly dynamic and heterogeneous structures. Previous indirect evidence suggested that membrane rafts are only 10–200 nanometers in size—smaller than the resolution limit of conventional optical microscopy (approximately 200 nanometers). As a result, the lack of direct imaging evidence has led to continued skepticism regarding their existence.
To address this challenge, the present study developed an innovative atomic force microscopy (AFM) imaging strategy. The core idea is to suppress weakly correlated image information in order to enhance the reliability of membrane-raft identification. A collaborative research team led by Prof. Chun-hsien Chen, Prof. Ja-An Annie Ho (joint appointment), and Prof. Richard P. Cheng from the Department of Chemistry at National Taiwan University, together with Prof. Li-Chen Wu from the Department of Applied Chemistry at National Chi Nan University, applied a Hadamard product to simultaneously acquire topographic height and mechanical stiffness data of the cell membrane. This approach highlights membrane-raft regions that are both “higher and stiffer” than the surrounding membrane, effectively suppressing irrelevant background signals and enabling direct visual identification of height and stiffness changes in membrane rafts before and after external stimulation.
This technical advance allows direct visualization of membrane-raft dynamics on live breast cancer (MCF-7) cells. In the absence of external stimulation, membrane rafts exhibit diameters below approximately 150 nanometers and heights of about 1.9 nanometers. Upon addition of fibrinogen, a pro-metastatic factor, membrane rafts aggregate into features approximately 1 micrometer in diameter and up to 45 nanometers in height. In contrast, treatment with Mn²⁺/resveratrol, which promotes apoptosis, leads to the formation of dispersed protrusions with heights exceeding 10 nanometers and lifetimes ranging from 10 to 60 minutes. With a temporal resolution of approximately one image every 30 seconds, this AFM approach enables real-time tracking of these dynamic processes and establishes a new analytical platform for understanding cellular signal transduction pathways.
