pH-sensitive polymeric nanocarriers for antitumor biotherapeutic molecules targeting delivery

pH-sensitive smart polymeric nanocarriers have been under development in the field of biomedicine due to permeabilization the physiological barriers readily to address the limitation of conventional chemotherapeutics delivery systems of low intracellular transport and targeting efficiency. Where traditional polymers kept stable under physiological neutral or acidic conditions, pH-sensitive polymeric nanocarriers underwent rapid degradation with a labile group in tumor acidic environment (around 5.0–6.0), allowing these biomaterials to achieve controlled drug release, drug pharmacokinetics improvement and antitumor biotherapeutic molecules efficiency enhancement compared with traditional polymers. This review mainly concentrated on properties of pH-sensitive polymers for biomedical purposes to construct the smart drug delivery system based on acid liable linkers which were categorized into pH-sensitive polymeric prodrugs composed of antitumor drugs (doxorubicin and paclitaxel) bounded to the polymer via acid liable linkers and pH-sensitive copolymeric nanocarriers prepared by block copolymers containing polymer blocks linked with acid-cleavable groups. Besides, advanced platforms in biomedicine for special biotherapeutic molecules delivery were reviewed in the article. Furthermore, several acid-sensitive linkages were reviewed to study the mechanism of the controlled pH-responsive drug delivery, such as hydrazone, acetal, cis-aconityl linker and β-thioether ester, as well as improvement of drug pharmacokinetics.