No chemicals can make human tissue regenerate in seconds. Biological tissue is composed mainly of a large collection of cells sitting in a scaffolding of proteins and sugar chains (the extracellular matrix) and bathed in fluids that carry various chemicals between the cells. Public Domain Image, source: Christopher S. Baird. The regeneration of tissue mainly involves the fabrication of the extracellular matrix, which is secreted by cells, and the creation of new cells by way of cell division. Therefore, the rate at which tissue regenerates is mainly limited by how fast one cell can divide into two new, fully-functional cells that then become mature enough to divide again. This cell reproduction time depends on the type of cell, but for humans the shortest duration of a single cell cycle is about one day. In order to generate a decent amount of tissue, several cell cycles will be needed, so the total time to regenerate tissue is at the very best a few days. This number is an absolute minimum. In most cases, it will take far longer for a human to regenerate a significant amount of tissue; from weeks to months. Furthermore, if the need to regenerate is caused by acute damage to the tissue, the body may respond by forming a scar rather than regenerating the tissue. Certain types of human tissue simply can't regenerate on their own in response to significant injury. Even if we could apply chemicals that force the tissue to regenerate as fast as possible (but still remain as somewhat normal human cells), the best we can do is to have tissue regenerate in few day, not in a few seconds. A few exotic non-human embryo cells can reproduce as fast as every 8 minutes. However, such reproduction is so fast this it does not allow enough time for the cells to grow in size. They only divide into smaller cells while the overall volume of the tissue remains the same. So this would not really count as tissue regeneration in 8 minutes. Assuming it did count, this would mean that with extensive genetic engineering to make human cells act like these exotic non-human embryo cells, the best we could ever do is to get tissue regeneration in 8 minutes, not in a matter of seconds. This is simply a plausibility limit. It is doubtful that this regeneration time could ever be achieved, even with the best genetic engineering. Again, the fastest human cell cycle duration is a day.