Dc to Dc converters

I am working on data acquisition of low voltage analog signal with amplitude range of 0.1uV to 1uV. Basically I am reading Bio potential signal.  I need some help to understand the need of Dc to DC converters in this application.

Suppose if I use DC to DC converter with isolation , will it reduces noise or will it gives protection to human body.

Please help me in this regard.

Thanks

Thejesh