3D printed and smart alginate wound dressings with pH-responsive drug and nanoparticle release

The pH of a wound site can undergo a significant change from its normal range of 5.4–5.6 to a more alkaline environment of 7.2–8.9 after being infected by microorganisms. Therefore, the development of a smart material that can respond to this shift in pH and release antimicrobial agents for effective treatment of wound infections holds great promise for the future of wound care. In the present work, we produced 3D printed alginate wound dressings doped with calcium phosphate nanoparticles (CaP NPs), referred to as alginate-CaP nanocomposites hereafter. The CaP NPs enabled pH-responsive switching of the degradation and drug release of 3D-printed alginate-based wound dressings. Three sizes of rod-shaped CaP NPs were synthesised, including small NPs (62 × 18 nm), medium NPs (197 × 49 nm), and large NPs (496 × 143 nm). The addition of CaP NPs significantly increased both the tensile strength and elongation at the break of the alginate dressings. Additionally, the degradation rate of the alginate-CaP nanocomposite dressings increased with pH, potentiating pH responsive drug delivery from the dressing. Alginate nanocomposites with 1 mg/mL of medium-sized CaP NPs were found to elicit the strongest pH responsiveness. The release rates of rhodamine B, the antibiotic peptide bacitracin, and antimicrobial selenium nanoparticles were assessed, and showed faster release at higher pHs. These results illustrate that CaP NPs can be easily used as a pH-responsive switch to effectively control the degradation and drug release of alginate based wound dressings, enabling increased antimicrobial release at the pH of infected wounds.