纳米酶的催化机制及应用

Catalytic mechanism and application of nanozymes

近年来,随着纳米材料的发展,一些纳米材料逐渐被发现具有与天然酶相似的高效催化活性,且克服了天然酶易失活、产量低等缺点,被定义为纳米酶其催化活性受纳米材料尺寸、结构、表面修饰等因素调节.这些纳米酶分为金属氧化物纳米酶、贵金属纳米酶和碳基纳米酶.本文将针对不同纳米酶的催化机制进行分类,归纳不同纳米酶的催化机制,并且整理纳米酶在体外疾病检测、体内肿瘤治疗等领域的应用.

Most natural enzymes are composed of hundreds of amino acid molecules, and widely used in many fields such as biosensor, cancer therapy, immunoassay, food safety and environmental management due to their efficient catalytic ability. However, on account of intrinsic drawbacks of natural enzymes, such as ease of inactivated in extreme conditions, difficulty preparation and high cost, limit the application of enzymes, people make great efforts to develop diverse artificial enzymes of high catalytic activity and stability. With the development of nanomaterials, their catalytic performance has been gradually discovered. These nanomaterials, known as nanozymes, have similar activities with natural enzymes. Due to their unique catalytic activities and the inherent properties, nanozymes have cause great attention in recent decades. So far, more than 50 kinds of nanoparticles have been found to have oxidoreductase activity such as peroxidase（POD）, catalase（CAT）, superoxide dismutase（SOD）, glucose oxidase（GOD）. In addition, the catalytic activity can be regulated and designed by changing their size, structure, composition and surface modification. Those nanozymes can be mainly divided into metal oxide nanozymes, noble metal nanozymes and carbon-based nanozymes. Metal oxide nanozymes usually refer to the transition metal oxide nanoparticles. The generation of oxidoreductase activity by integration the nanozymes and the substrates results in valence changes and electron transport. Unlike the catalytic mechanism of metal oxide nanozyme, noble metal nanozymes and carbon-based nanozymes have no valence change of metal elements in the catalytic reaction. They have also been found to exert their activities by the adsorption, activation and surface electron transfer of catalytic substrates. Although the nanozymes have advantage of broader tolerable p H and widely temperature ranges, the enzyme activity generally has p H and temperature dependency similar to the natural enzyme. However, a great advantage of nanozymes is that their activity can be tuned by the size, composition, structure and surface modification of nanomaterials. In general, the smaller the nanozyme size, the greater the specific surface area, the more substrate binding, resulting in the stronger enzyme catalytic activity. Under the same conditions, the 30 nm IONPs have stronger POD activity than IONPs of the 150 and 300 nm size, the smaller Pt NPs have stronger ascorbate oxidase activity and POD activity. Similarly, smaller Au NPs also have stronger POD activity. Moreover, the morphology and structure of nanomaterials also have a considerable impact on the nanozyme activity. Since the catalytic reaction takes place on the surface of the nanozyme, the modification of the nanozyme is also very important for enhancing the sensitivity and selectivity of the nanozymes. Surface-modified molecules include small molecules, synthetic polymers and nucleic acids. In this review, the catalytic mechanisms of the nanozymes in recent years are sorted and classified. In addition, the regulatory factors of the activities and the catalytic specificity of the nanozymes are summarized and analyzed. It is highly expected that establishment of a novel nanozymes as highly stable and low-cost alternatives to natural nanozymes in a wide range of applications in multiple field.