I need to find a way to measure protein concentration.

Question

It's for part of my infection and immunity lab report.

We've done about radial immunodiffusion calculating the concentration of bovine serum albumin in unknown samples, and the last question is:

What other techniques could you use to measure the concentration of an antigen in a biological sample?

For some reason under this I have written: 'Specific protien concentrations' I guess this was because the lecturer mentioned it when the work was set and it makes sense antigens have protiens on so if I could work out the concentration of the protein then I'm there but I'm not sure how to do that?

Does anyone know of a way?

I also thought of a titration because that's how we always found the concentration of stuff back when did chemistry, so that would be titrating antibody against antigen, but I would need an indicator and I don't know of any.

Can anyone help me please?

Ballet_Baibe