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The Use of Poly-L-lysine as an Adhesive in Scanning Electron Microscopy

Poly-L-lysine of a medium molecular weight, 30,000 to 70,000 Daltons (Sigma–Aldrich), is currently used in our facility as a polycationic adhesive on 5 mm square silicon chips to secure individual anionic cells and particles for ease of processing and viewing in the scanning electron microscope. In this technique, a solution of 1 mg/ml of poly-L-lysine is dissolved in distilled water. Drops of the solution are placed onto clean 5 mm square silicon chips and allowed to sit for one to several hours before being wicked away. The prepared chips are used immediately. Suspended cells are then applied to the chips and allowed to settle and adhere, after which they are washed and fixed. Alternatively, fixed suspended cells or particles are applied to these silicon chips. The cells and particles secured to the silicon chips are easily handled through processing steps such as dehydration, critical point drying, and metal sputter coating for viewing in the scanning electron microscope. Presented herein is a brief history of the evolution of the technique of using poly-L-lysine as an adhesive for SEM.