Preparation and Characterization of Nitrogen-Doped Carbon Microspheres for pH-Responsive Colon-Targeted Drug Delivery

In this study, poly(acrylic acid) (PAA)-coated aspirin (ASA)/amino-N-doped carbon microspheres (P-ASA@ANMCs) were synthesized by a hydrothermal method, amination method, and electrostatic coating method with cassava starch as the carbon source. The design considers both the drug delivery efficiency and biological safety. The microstructure, drug loading capacity, cytotoxicity, antimicrobial activity, and drug release mechanisms were investigated using SEM, FTIR, XRD, Raman spectroscopy, XPS, cell experiments, and antimicrobial testing. The results revealed that the microspheres show a uniform spherical shape (∼1 μm) with a high drug loading capacity. Furthermore, P-ASA@ANMCs exhibited excellent antimicrobial properties against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>. They also demonstrated pH-responsive colon-targeted sustained-release properties. The detailed release mechanisms were proposed based on characterization data. This study validates the biomedical application potential of cassava-starch-derived microspheres, highlighting the promise of P-ASA@ANMCs for pH-responsive colon-targeted drug delivery systems (pH-CTDDS).