I work with HBV patient samples with very low concentration of viral DNA. I wana amplify a fragment of HBV genome but samples DNA concentration is too low. what can I do freinds ??
Most of PCR mix final volume is water so just exchange some of that water and substitute it for viral DNA. You have to be sure that your DNA sample is clean (salt, inhibitor free) otherwise adding more volume of it would be detrimental.
I have done PCRs using up to 10 ul of template (DNA) sample in a final volume of 20 ul (chelex extraction) and worked well.
We had some experience with difficult samples: dehydrated pet food processed at very high temperature and with not much DNA and of very low quality. In such cases we used to concentrate DNA extracts by means of an ultrafiltration kit.