title: Nanostructures for pH-sensitive Drug Delivery and Magnetic Resonance Contrast Enhancement Systems.
abstract: According to the differences of microenvironments between tumors and healthy tissues, if the anticancer drugs or magnetic resonance contrast agents (MRCAs) can be controlled to precisely match physiological needs at targeted tumor sites, it is expected to acquire better therapeutic efficacy and more accurate diagnosis. Over the decade, stimuli-responsive nanomaterials have been a research hotspot for cancer treatment and diagnosis because they show many excellent functions, such as in vivo imaging, combined targeting drug delivery and systemic controlled release, extended circulation time, etc. Among the various stimuli nanosystems, pH-stimuli mode is regarded as the most general strategy because of solid tumors acidosis. When exposed to weakly acidic tumor microenvironment, pH-responsive nanoplatforms can generate physicochemical changes for their structure and surface characteristics, causing drug release or contrast enhancement. In this review, we focused on the designs of various pH-responsive nanoplatforms and discussed the mechanisms of controlled drug release or switch on-off in MRCAs. This review also discussed the efficacy of cellular internalization for these nanoplatforms via endocytosis of acidic tumor cell. Meanwhile, nanoplatforms response to acidic intracellular pH (such as endosome, lysosome) are discussed, along with approaches for improving drug release performance and magnetic resonance contrast enhancement. A greater understanding of these pH-responsive nanoplatforms will help design more efficient nanomedicine to address the challenges encountered in conventional diagnosis and chemotherapy.
authors.affiliation: Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Sun
authors.affiliation: Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Guilong
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zhengyan
authors.initials: Z
authors.lastname: Wu
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D003287:Contrast Media / Q000737:chemistry*; D016503:Drug Delivery Systems; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D049329:Nanostructures / Q000737:chemistry*; D009369:Neoplasms / Q000188:drug therapy* / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D003287:Contrast Media
keywords: cancer diagnosis and chemotherapy; contrast enhancement; controlled
  release; drug delivery systems; magnetic resonance contrast agents; pH-responsive.