Mechanisms of drug release in pH-sensitive micelles for tumour targeted drug delivery system: A review

During the past decades, chemotherapy has been regarded as the most effective method for tumor therapy, but still faces significant challenges, such as poor tumor selectivity and multidrug resistance. The development of targeted drug delivery systems brings certain dramatic advantages for reducing the side effects and improving the therapeutic efficacy. Coupling a specific stimuli-triggered drug release mechanism with these delivery systems is one of the most prevalent approaches for targeted therapy. Among these approaches, pH-sensitive micelles are regarded as the most general strategy with advantages of increasing solubility of water-insoluble drugs, pH-sensitive release, high drug loading, etc. This review will focus on the potential of pH-sensitive micelles in tumor therapy, analyze four types of drug-loaded micelles and mechanisms of drug release and give an exhaustive collection of recent investigations. Sufficient understanding of these mechanisms will help us to design more efficient pH-sensitive drug delivery system to address the challenges encountered in targeted drug delivery systems for tumor therapy.