The cell membrane is a protective layer that strictly controls the passage of molecules restricting the delivery of biomolecules such as drugs, oligonucleotides, peptides, and siRNA into the cells. This shortcoming has been overcome by the discovery of Cell-Penetrating Peptides (CPPs) that has undergone 30 years of evolution. To date, CPPs are largely modified to improve its efficacy and to suit the different delivery applications. The modes of CPPs penetration are still an unresolved mystery and requires further investigations to increase its effectiveness and to diversify its use. Despite having huge potential as a biomolecule carrier, CPPs also have some drawbacks. In this review, the natural and synthetic CPPs, the modifications that have been conducted on CPPs to improve its efficacy, its extended applications, modes of penetration and limitation as well as challenges will be discussed.

细胞膜是严格控制分子通过的分子的保护层，这些分子限制了生物分子如药物，寡核苷酸，肽和siRNA进入细胞的传递。通过发现已经经历了30年进化的细胞穿透肽（CPP），克服了这一缺点。迄今为止，对CPP进行了大量修改以提高其功效并适应不同的交付应用。CPP渗透的方式仍然是一个未解之谜，需要进一步研究以提高其有效性并使其用途多样化。尽管CPP作为生物分子载体具有巨大潜力，但它也有一些缺点。在这篇评论中，天然和合成的CPP，为提高CPP的功效而进行的修改，扩展的应用，