Self-gated porous organic polymer as drug delivery system for pH stimuli-responsive controlled Quercetin release

Porous organic polymers (POPs) featuring low toxicity and large specific surface areas are suitable for drug delivery carriers. But owing to the special stability of covalent bond, POPs could not be metabolized and accumulate in the body, restricting its further applications, greatly. Acetal is a special chemical bond, unstable in acidic solutions, but stable to bases and oxidants. Here, an acetal-linked porous organic polymer, namely HCTP-MA, was well-designed and facilely fabricated via the condensation of body-absorbable D-Mannitol (MA) and biodegradable hexa (p-formylphenyl)cyclotriphosphazene (HCTP). The oxygen rich acetal-links endowed strong polarity to the porous skeletons, improving the drug loading capacity significantly. The polyhydric-drug, i.e. Quercetin, could load into the porous skeleton firmly via both hydrogen bond and van der Waals' force. HCTPMA displayed a high drug loading capacity of 85.60 +/- 0.13%, higher than other reported POP based materials. Acetal-bond, served as the gatekeeper, also introduced the stimuli-responsive performance to POP with almost no release in neutral pH. The controlled release of drugs could be achieved by lowering pH to degrade the acetalgatekeepers. Experimental results also validated the synergistic action of dehydration (induced by the catabolite MA) and the regulation of Que in the gated drug delivery system also enhanced the therapeutic effects to the lung cancer.