Synthesis of pH-Sensitive polydopamine capsules via pickering emulsions stabilized by cellulose nanocrystals to study drug release behavior

Stimuli-responsive carriers capable of recognizing and responding to physiological changes (external stimuli such as photo, temperature, pH, etc.) play an essential role in targeting drug delivery. In this study, Hollow polydopamine (PDA) nanocapsules was developed with a considerably small mean droplet size of 397 nm templated by Pickering emulsions stabilized by cellulose nanocrystals for drug encapsulation. These PDA drug delivery systems were characterized with scanning electron microscope, dynamic light scattering, and fourier transform infrared techniques. To study the drug release behavior, the typical chemotherapeutic agent, doxorubicin (dox), was loaded into PDA capsules, and drug loading efficiency of 76.14% and encapsulation efficiency 73.43% was obtained. The maximum release percentages of dox after 48 h were 19.01, 39.64, and 80.76% in the solution with pH 7.4, 6.8, and 5.5, respectively. To achieve controlled drug release in the acidic environment of cancer tissue, dox should be released in an acidic media and blocked in the neutral media. These PDA capsules can work as stimuli-sensitive gatekeepers to control the release of drug molecules in response to the pH stimulus. It is worth noting that this is the first work that was able to prepare and investigate drug loading and release properties in PDA capsules formed on emulsion droplets stabilized by cellulose nanocrystals with a size of less than 500 nm.