[googleviet]

Have you ever heard about a medicine include a polypeptide chain to increase its soluble in blood and suitable with your body? Thanks for your answer.

[agrobert]

Your question is vague in the sense that we don't know what type of drug you would be attaching a polypeptide chain.  Yes, there are drugs that include peptide chains but they generally function for more than just solubilty in blood. 

Things to consider are

Where is the desired active site of your drug within metabolism?
How large is your drug and will it be accessible during metabolism with a polypeptide chain?
Will the polypeptide chain interfere with the activity of your drug?
Will the polypepdtide chain enhance the activity of your drug?
On what position of the drug will the chain branch?
Does the polypeptide chain affect drug stability?

If the sole purpose of the polypeptide chain is to increase blood solubilty I think you would have better results with a salt (which would most likely be more cost efficient).