Hi Raghul

There are different ratios of hydroxyapatite (HA) that can be reinforced with the polymer for tissue regeneration scaffold depending on the method of prep, morphology and particle size of HA.

What is your method of prep particle and size of HA, so I can give you answer more precisely.

Moreover, I will suggest you to read following articles

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3997175/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3975421/

https://www3.nd.edu/~rroeder/publications/2015%20Acta%20Biomat%20Kane.pdf

My method of preparation is Wet chemical synthesis and size of HA is around 174 nm.

There are no limits. For example, to prepare a scaffold, one can take 99% of polymer (collagen, polyethylene, etc.) and add 1% of hydroxyapatite or one can take 99% of hydroxyapatite and add 1% of polymer (collagen, polyethylene, etc.). The problem is to find the optimum properties of the scaffolds, such as the maximum strength, the maximum toughness, the fastest bioresorbability, etc.; however, each of these optimums has different hydroxyapatite/polymer ratios.

Actually in order to know that one of the important things is the properties of polymer you use. And as you said you are asking it for "bone regeneration" you cannot know it without doing preliminary experiments either in vitro or in vivo or both. Your question is is so wide and "unknown"