I can give you some pointers on biomarkers in general, but I can't deal with specific issues as I'm uncertain as to the course of study you're following.
Biomarkers need to be readily obtainable and easy to measure. They also need to be highly responsive and able to provide consistent results throughout the period of study. In addition, they are required to be either non-invasive or minimally invasive for the individual or cohort concerned. Biomarkers are usually divided up into those of susceptibility, effect, exposure and development but there are others too.
Online databases such as Ingenta Connect, Science Direct, Ovid and Biodigest will provide you with further information via published papers. Other journals not included in these databases should also be accessible via academic libraries.
You should also be able to find textbooks with chapters on biomarkers in academic libraries.