Imaging 'intact' myofibrils with a near-field scanning optical microscope

Area of Science:

• Biophysics
• Cell Biology
• Microscopy

Background:

• Muscle contraction is fundamental to biological function.
• High-resolution imaging of myofibrils is crucial for understanding muscle structure and function.
• Current imaging techniques may require labeling or suffer from resolution limitations.

Purpose of the Study:

• To compare near-field scanning optical microscopy (NSOM) and shear-force microscopy (SFM) for imaging myofibrils.
• To assess the effectiveness of SFM as a label-free imaging modality for contractile biological samples.
• To evaluate the impact of specimen thickness and substrate adherence on image resolution.

Main Methods:

• Myofibrils were fluorescently labeled and imaged in physiological salt solution.
• Near-field scanning optical microscopy and shear-force microscopy were employed.
• Antibody labeling was used to identify Z-line protein structures for NSOM.
• Specimens were imaged in vitro, adhering to glass, while maintaining contractile ability.

Main Results:

• Both NSOM and SFM successfully imaged myofibrils.
• Z-line protein structures were clearly identified in NSOM fluorescence images.
• The characteristic protein banding of myofibrils was visualized without labeling using SFM.
• SFM images were less affected by specimen thickness compared to transmission NSOM images.
• SFM contrast mechanism remains to be fully elucidated, but the technique shows promise.

Conclusions:

• Shear-force microscopy is a promising label-free imaging technique for biological specimens like myofibrils.
• SFM provides high-resolution structural information without the need for fluorescent labels.
• The technique is relatively robust to specimen thickness, offering advantages over traditional optical microscopy in certain configurations.