Quantitative evaluation of embedding resins for volume electron microscopy

Area of Science:

• Materials Science
• Microscopy Techniques
• Biotechnology

Background:

• Consistent serial sectioning is vital for large tissue samples in volume electron microscopy.
• Non-uniform epoxy resin curing can compromise section quality and uniformity.
• Current methods lack robust quantification of resin curing and its impact on sectioning.

Purpose of the Study:

• To develop and validate methods for quantifying epoxy resin curing non-uniformity.
• To assess the impact of resin properties and embedding techniques on sectioning repeatability.
• To provide a framework for optimizing resin formulations and embedding protocols for improved section quality.

Main Methods:

• Quantification of resin curing non-uniformity using block hardness measurements.
• Measurement of transverse and sectional cutting forces during ultrathin sectioning with a force sensor.
• Exploration of gelatin encapsulation for irregularly shaped tissue samples prior to epoxy embedding.

Main Results:

• Identified conditions leading to non-uniform resin curing.
• Established a procedure to monitor block hardness across various epoxy resins.
• Demonstrated that screening and optimizing resin formulations enhances section thickness repeatability.
• Showcased gelatin encapsulation as a method to improve section uniformity for irregular samples.

Conclusions:

• Block hardness measurement is an effective method to quantify resin curing non-uniformity.
• Optimizing epoxy resin formulations and embedding procedures is essential for consistent serial sectioning.
• Gelatin encapsulation offers a viable strategy for improving section quality of challenging sample geometries.