Most studies using In vitro 5-ala photodynamic therapy model uses a serum-free medium while incubating with 5-ala. It is actually sensible that the presence of albumin in serum can interfere with 5-ala absorption and activate ABCG2 to efflux ppIX out of the cell. We have observed in the lab that using fbs containing medium can increase the LD50 making cells less sensitive to PDT compared to when cells are incubated with serum free medium. This goes to show that PPix levels are theoretically different between those two scenarios. Moreover, difference in manufacturing of fbs even of the same brand could also yield inconsistencies of results. We have also observed that using fbs last year and this year, and also within co labmates, had different results. Therefore we used serum free all throughout the experiments.

However, if we will think in vivo, cancer lesions contain more albumin due to increased vasculature. Simulating this in vitro would definitely demand that we use fbs instead. In your opinion, what is your take on using serum free medium in the protocol? Would this be a factor to criticize the in vitro model (no fbs was used)?