Switching to Biosystems Engineering from chemical engineering

I'm a 4th year chemical engineering undergrad from BITS Pilani. My CGPA is 7.2. I have 5 projects, 3 of which are from internships at CSIR laboratories. I am interested in pursuing Biosystems engineering for further studies. I have previous roject experience in Biomedical Nanotechnology. But all my other projects are in Core chemical engineering(Thermo, Reaction Engg, Catalysis, Extraction) .

1) will it be difficult to secure admission in one of the top ranked universities (say below 100)?
2) Should I take a subject GRE to show my knowledge of Biology?

I haven't takeen the GRE or TOEFL yet, but will be doing so in the next month.