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.
