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.

在这项工作中，制备了具有肿瘤pH响应性的两性离子聚合物（聚两性离子）涂层纳米金刚石（ND），以将商业ND有效地应用于肿瘤细胞成像。首先通过表面引发的可逆加成-断裂链转移（RAFT）聚合将聚（甲基丙烯酸甜菜碱酯）接枝到原始的NDs（PCBMA-@-NDs）上。为了获得pH响应性和与肿瘤细胞的活化相互作用，随后通过一步碳二亚胺化学用苯磺酰胺（PCBSA-N-ND）修饰PCBMA-N-ND。表面聚合物官能化的特征在于FTIR，¹与原始NDs相比，1 H NMR和TGA以及PCBMA-@-NDs和PCBSA-@-NDs显示出很大的分散性，增强的荧光强度和优异的防污性能。此外，PCBSA-@-NDs能够通过质子化或去质子化的酰基磺酰胺将两性离子表面（pH 7.4）可逆地转换为正电荷（pH 6.5）。如预期的那样，通过荧光显微镜和流式细胞术证明，在肿瘤轻微的酸性环境下，PCBSA-@-NDs比两性离子NDs具有更高的细胞亲和力和更好的成像性能。总体而言，我们提供了构建智能ND的可行且有价值的策略，从而鼓励了具有成本效益的荧光纳米材料在生物医学领域中的应用。