In recent years, zinc oxide nanoparticles (ZnONPs) emerged as an excellent candidate in the field of optical, electrical, food packaging and particularly in biomedical research. ZnONPs show cancer cell specific toxicity via the pH-dependent (low pH) dissolution into Zn²⁺ ions, which generate reactive oxygen species and induce cytotoxicity in cancer cells. Further, ZnONPs have also been used as an effective carrier for the targeted delivery of several anticancer drugs into tumor cells. The increasing focus on ZnONPs resulted in the development of various synthesis approaches including chemical, pHysical, and green or biological for the manufacturing of ZnONPs. In this article, at first we have discussed the various synthesis methods of ZnONPs and secondly its biomedical applications. We have extensively reviewed the anticancer mechanism of ZnONPs on different types of cancers considering its size, shape and surface charge dependent cytotoxicity. Photoirradiation with UV light or NIR laser further increase its anticancer activity via synergistic chemo-photodynamic effect. The drug delivery applications of ZnONPs with special emphasis on drug loading mechanism, stimuli-responsive controlled release and therapeutic effects have also been discussed in this review. Finally, its side effects to vital body organs with mechanism via different exposure routes, the future direction of the ZnONPs research and application are also discussed.

近年来，氧化锌纳米粒子 (ZnONPs) 成为光学、电气、食品包装领域，尤其是生物医学研究领域的优秀候选者。ZnONPs 通过 pH 依赖性（低 pH）溶解到 Zn ^{2+ 中}显示出癌细胞特异性毒性离子，产生活性氧并在癌细胞中诱导细胞毒性。此外，ZnONPs 还被用作将几种抗癌药物靶向递送到肿瘤细胞中的有效载体。对 ZnONPs 的日益关注导致了各种合成方法的发展，包括用于制造 ZnONPs 的化学、物理和绿色或生物方法。在本文中，我们首先讨论了 ZnONPs 的各种合成方法，其次讨论了其生物医学应用。考虑到 ZnONPs 的大小、形状和表面电荷依赖性细胞毒性，我们广泛审查了 ZnONPs 对不同类型癌症的抗癌机制。紫外光或近红外激光光照射通过协同化学光动力效应进一步提高其抗癌活性。本综述还讨论了 ZnONPs 的药物递送应用，特别强调载药机制、刺激响应控制释放和治疗效果。最后，还讨论了其通过不同暴露途径对重要身体器官的副作用，以及ZnONPs的研究和应用的未来方向。