The Application of Poly(2-(hydroxymethyl)acrylic Acid as a Functional Nanomaterial to Ensure the Biosafety of Herbal Decoctions

Heavy metal ions in herbal medicine sometimes exceed the standard limit, inducing severe and harmful problems in human health. Exploring new nanomaterials to chelate heavy metal ions and reduce their concentration in herbal decoctions could be a solution route. In this study, the nanoadsorbent poly(2-(hydroxymethyl)acrylic acid (PHMAA) was prepared via free radical polymerization and the hydrolysis method. PHMAA showed excellent dispersion in aqueous solution and self-assembled into spherical aggregates with a negative surface charge. After freeze-drying, PHMAA was a white solid powder with a loose porous structure. PHMAA presented no significant influence on the cell viability and weight of normal BALB/c mice. PHMAA showed good removal efficiency towards Cd²⁺ ions in aqueous solution; the removal rate exceeded 80%. In herbal decoctions, PHMAA presented moderate to good removal capacity towards Cd²⁺ ions; the removal rate was 60%, 83%, and 89% for the <i>Morindae officinalis radix</i> decoction, <i>Ligusticum wallichii</i> decoction, and <i>Coptidis rhizome</i> decoction, separately. When the concentration of Cd²⁺ ions in the decoction was decreased to 5 μg/mL, PHMAA also presented good removal efficiency. During the removal process, PHMAA played no influence on the active ingredients. To conclude, PHMAA showed good biosafety and removal capacity towards Cd²⁺ ions, which might be utilized as nanoadsorbents to reduce the concentration of Cd²⁺ ions in aqueous solution and herbal decoctions.