Editing Regenerated amorphous Cellulose (section)

== Regenerated amorphous cellulose (RAC) preparation <br> ==

Microcrystalline cellulose Avicel PH105 (20 um) – FMC (Philadelphia,<br>PA, USA).<br>

Approximately 0.2 g of microcrystalline cellulose and 0.6 mL distilled water were added into a 50-mL centrifuge tube to form a cellulose-suspension slurry. Ten milliliters of ice-cold 86% H3 PO4 (i.e., commercial 85% grade) was slowly added into the slurry with vigorous stirring so that the final phospho-ric acid concentration was ca. 83.2%. The cellulose mixture turned transparent within several minutes. It stood for ca. an hour in an ice bath with occasional stirring. Approximately 40 mL of ice-cold water was added at a rate of approximately 10 mL per addition with vigorous stirring between additions, resulting in a white cloudy precipitate. The precipitated cellulose was centrifuged at ∼10,000 × g and 4 ◦ C for 20 min. The pellet was suspended in ice-cold water, followed by centrifugation to remove the phosphoric acid from the supernatant, four times. Approximately 0.5 mL of 2 M Na2CO3 and 40 mL of ice- cold distilled water were used to neutralize and suspend the cellulose pellet. After centrifugation, the pellet was washed by distilled waters twice or until pH 5–7. The carbohydrate concentration of RAC was calibrated by the phenol-H2SO4 method [28]. Other cellulose powders such as SigmaCell can be used to replace FMC PH105. The RAC slurry can be stored as a ∼10 g RAC L −1 suspension solution at 4 ◦ C in the presence of 0.2% (w/v) sodium azide for at least 1 year. 

<br>