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

## TL;DR

A new nanomaterial called PHMAA was developed to safely remove harmful cadmium ions from herbal decoctions without affecting their active ingredients.

## Contribution

The study introduces PHMAA as a novel nanoadsorbent for biosafely removing Cd2+ ions from herbal medicines.

## Key findings

- PHMAA showed over 80% removal efficiency for Cd2+ in aqueous solutions and 60-89% in herbal decoctions.
- PHMAA did not affect the viability of normal mice cells or the active ingredients in herbal decoctions.
- PHMAA maintained good removal efficiency even when Cd2+ concentration was as low as 5 μg/mL.

## Abstract

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 Morindae officinalis radix decoction, Ligusticum wallichii decoction, and Coptidis rhizome 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.