Regenerated amorphous cellulose

Synthesis

Microcrystalline cellulose – Avicel PH105 (20μm) is from FMC (Philadelphia,PA),
or SigmaCell Sigmacell Cellulose Type 20, 20 μm

Add ~ 0.2g of microcrystalline cellulose to 0.6 mL distilled water in a 50-mL centrifuge tube.
Add 10 ul of ice-cold 86% H3PO4 (i.e., commercial 85% grade) slowly into the slurry with vigorous stirring so that the final phosphoric acid concentration is ~ 83.2%.
The cellulose mixture will become transparent within a few minutes.
Incubate on ice for ~ 1 hour with occasional stirring.
Add ~ 40mL of ice-cold water while mixing/stiring, this will result in a white cloudy precipitate.
Spin 10,000×g at 4◦C for 20 min.
Suspend the pellet in ice-cold water.
Spin again to remove the phosphoric acid.
Repeat wash for 4 times.
Add 0.5mL of 2M Na2CO3 and 40mL of ice-cold distilled water to neutralize and suspend the cellulose pellet.
Spin, wash the pellet with distilled waters twice or until pH 5–7.

Store the slurry as a 10g RAC/1L suspension solution at 4◦C in the presence of 0.2% sodium azide