Acid and light dual- stimuli-cleavable polymeric micelles

In this study, acid and light dual- stimuli-responsive amphiphilic AB-type methoxy poly(ethylene glycol)-acetal-ONB-poly(4-substituted-ε-caprolactone) (MPEG-a-ONB-PXCL) diblock copolymers were synthesized using ring-opening polymerization and nucleophilic substitution reactions. The prepared copolymer features an acid-cleavable acetal group and photocleavable o-nitrobenzyl linkage between the hydrophilic MPEG and hydrophobic PXCL blocks. The design enables the diblock copolymers to respond to both acid and ultraviolet (UV) light while ensuring the minimum number of stimuli-reactive moieties in the copolymer structure. The disruption of the copolymeric micelles in aqueous solution was examined under the action of pH or UV light alone or under the combined stimulation pH and UV light. Under the combined stimulation of UV irradiation and pH, the micellar nanoparticles could dissociate; therefore, the loaded molecules could be released from the assemblies more efficiently than under either stimulus alone. The nanoparticles exhibited nonsignificant toxicity against human cervical cancer (HeLa) cells at concentrations ≤300 μg mL⁻¹. Doxorubicin (DOX)-loaded micelles facilitated the uptake of DOX by the HeLa cells at the initial stage. The dual stimuli-cleavable polymeric micelles show promising potential as new nanocarrier for precisely controlled release of encapsulated drug.