DNA是生命体重要的遗传物质，在很多生命活动中扮演着重要的角色。然而，同一核酸链上相邻胸腺嘧啶在紫外光的作用下可通过加成反应形成环丁烷嘧啶二聚体（CPD）交联损伤产物。这种损伤产物如果不能及时得到修复，可进一步引起细胞衰老、死亡甚至癌变。研究发现，光修复酶如天然的光裂合酶可在光的作用下修复CPD，从而抑制DNA损伤所引发的皮肤类疾病，故在功能化妆品和医药产品中具有潜在的应用。但是光裂合酶不稳定，易受多种物理、化学因素的影响而失活。因此，寻找天然酶的替代品成为了当前的热点。基于以上背景，本文对具有良好体外活性和皮肤渗透性的二氧化钛纳米酶光催化修复CPD损伤进行了研究，初步探究光催化二氧化钛纳米酶修复CPD的反应条件。通过稳态紫外-可见吸收光谱的变化，发现二氧化钛在UVA光的作用下展现了修复CPD损伤的能力，并且修复效果与二氧化钛浓度具有一定关系，过高或者过低的浓度均会导致CPD损伤修复效果的下降。以上研究对人工酶修复DNA光损伤的进一步研究和相关应用提供了基础。

DNA is an important biomolecule and plays a critical role in functioning to express, store and transmit genetic information. Under the ultraviolet (UV) irradiation from sunlight, two adjacent thymine bases in the same DNA strand can undergo cycloaddition to form a cyclobutene pyrimidine dimmer (CPD), inducing damage of DNA that is associated with cell aging, death and even cancer. Studies have shown that the natural photolyase can recognize these damaged thymine dimers and restore these lesions with the help of blue light, showing potential applications in functional cosmetics and pharmaceutical products. However, photolyase is unstable and easily inactivated in vitro. Therefore, finding alternatives to natural enzymes that can repair the CPD damage has become a current hot topic. In this context, using the steady-state UV-Vis spectroscopy, we carefully studied the photocatalytic repair of CPD by titanium dioxide nanozymes, which has shown in vitro activity and skin permeability. When the CPD is repaired to normal thymine bases, the absorption around 260 nm will increase, due to the extinction coefficient of thymine is much larger than that of CPD. Interestingly, in the presence of both UVA light and titanium dioxide, the steady-state absorption around 260 nm increases pronouncedly as time proceeds, which corresponds to the repair of CPD lesion to normal thymine bases. This observation clearly demonstrates that titanium dioxide has the ability to repair CPD under the UVA light. Moreover, we also found that the repair efficiency is dependent on the concentration of titanium dioxide, and too high or too low concentration will reduce the repair efficiency of CPD. These results here shed light on the study of repairing DNA CPD lesion by titanium dioxide nanozymes, and the rational design of nanozymes in advanced cosmetics with repairing ability.