“…[14][15][16][17][18][19][20] Of these pH-responsive drug carriers,t he development of CaPbased nanocarriers has shown that they are potentialc andidates for intracellular drug delivery because CaP remains stable at physiologicalpH, but dissolves rapidly in an acidic endosomal( pH 5.0) or lysosomal (pH 4.5) environment, which leads to fast releaseo fa nticancerd rugs. [21] Moreover,a s am ajor component of bones and teeth, CaP exhibits extraordinary biocompatibility,s uperiorb iodegradability,a nd is nontoxic, [22,23] which makes it suitable for drug delivery.T od ate, researches have reported the use of organic amphiphilic polymers,d endrimers, or adenosine 5'-triphosphate as templates for CaP-based nanocarriers [24][25][26][27][28] to avoid the problemsa ssociated with the direct synthesis CaP NPs. However,t he above approachesh ave suffered from some limitations, such as ac omplicated synthesis process, the use of toxic organics olvents, large diameters, and av ery low drugc apacity.T oa ddress the abovec hallenges, and inspired by our previous study, [29] we used PAA, ap H-responsive material, as at emplate to prepare PAA/CaP NPs with dualp H-responsiveness and ah igh drugloading capacity.…”