Why is a phosphate buffer solution especially useful for biological applications?

Phosphate buffer solutions have several properties that make them especially useful for biological applications. 

Phosphate buffers are non-toxic and isotonic. When used in biological applications, they prevent denaturation and protect cells against shriveling or rupturing due to osmosis. They also help to maintain a constant pH level in a particular environment and prevent other changes that may compromise the data gathered from a process.