pH, temperature and reduction multi-responsive polymeric microspheres as drug delivery system for anti-tumor drug: Effect of middle hollow layer between pH and reduction dual-responsive cores and temperature sensitive shells

Multi-responsive polymeric microspheres have attracted more and more interest as drug delivery system (DDS) for anti-tumor drugs because they could achieve “on-demand” drug release, triggered by the tumor micro-environment. Here the pH, temperature and reduction multi-stimuli responsive polymeric microspheres were fabricated via distillation–precipitation polymerization technique, with or without the middle hollow layer between their pH and reduction responsive poly(methacrylic acid) (PMAA) cores and temperature sensitive poly( N -isopropylacrylamide) (PNIPAM) shells. The effect of the hollow layer on their drug loading and drug release performance was investigated in detail. It was found that the PMAA/PNIPAM yolk/shell microspheres with hollow layer possessed a higher drug loading capacity, while the PMAA/PNIPAM core/shell microspheres without hollow layer exhibited a better controlled release behavior. This understanding must be helpful on designing intelligent anti-tumor DDS.