I'm doing immunofluorescent staining of dopamine neurons in mice brains. I've seen various protocols using different concentrations of PB or PBS in their blocking buffer. I would like to know how would a 10x PBS (0.1M) effect the staining in comparison to using a lower concentration 1X (0.01M).
PBS should be used at 1x, otherwise it will not be at the appropriate osmotic pressure. This results in cell swelling or shrinking, affecting morphology. I would imagine that 10x PBS would cause crenation of your cells as the cells try to maintain osmotic pressure.
I definitely agree with what Craig said above.
I'll add that IMO, in the protocols/recipes you saw, 0.1M and 0.01M likely were talking about the phosphate buffer system (Sodium or potassium phosphate mono and dibasic) concentration. Without getting too fancy, suffice it to say that the ratio of mono vs dibasic phosphates determines pH, while the total amount determines buffer capacity. So:
standard 0.01M PBS (1x) has only 10mM of phosphates but a lot of NaCl and usually some KCl, totalling osmolarity close to saline.
0.1M PB is an aqueous buffer solutions of phosphates totalling 100mM (for example, for pH 7.4, 20mM monobasic and 80 dibasic, it also happens to perfectly dial in at 280mOsm). I've seen it mostly used for fixatives.
There's enough material and protocol divergence to start with, and then nomenclature adds a whole other layer out there to make you go crazy.
To conclude, I don't think anyone was knowingly using what we usually call 0.1M PBS (also common and better name imo is 10X PBS), a solution of >2700mOsm, in their IF protocols.
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