Novel polyzwitterion shell with adaptable surface chemistry engineered to enhance anti-fouling and intracellular imaging of detonation nanodiamonds under tumor pHe

Abstract

In this work, zwitterionic polymer (polyzwitterion) coating nanodiamonds (ND) with tumorous pH responsiveness were prepared for efficient application of commercial NDs in tumor cells imaging. Poly(carboxybetaine methacrylate) was firstly grafted on the pristine NDs (PCBMA-@-NDs) by surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. To achieve pH responsiveness and activated interaction with tumor cells, PCBMA-@-NDs were subsequently modified with benzene sulfonamide (PCBSA-@-NDs) via one step carbodiimide chemistry. The surface polymer functionalization was characterized by FTIR, 1H NMR and TGA, and PCBMA-@-NDs and PCBSA-@-NDs showed great dispersibility, enhanced fluorescence intensity and excellent antifouling property in contrast to pristine NDs. Moreover, PCBSA-@-NDs was able to switch zwitterionic surface (at pH 7.4) reversibly into positive charge (at pH 6.5) via protonated or deprotonated acylsulfonamide. As expected, PCBSA-@-NDs demonstrated higher cell affinity and better imaging performance than those of zwitterionic NDs at tumor slight acid environment, proven by fluorescence microscopy and flow cytometry. Overall, we provide a feasible and valuable strategy to construct smart NDs, thus encouraging the application of cost-effective fluorescence nanomaterials in biomedical fields.