I am doing a stability study for my Ag NPs to see if they are stable in cell culture medium. I am noticing that the absorbance is increasing little by little over time and the baseline is shifting up. I have no idea what could cause this because I am not adding anything to my solution or increasing the protein/vitamin concentration in any way.
if something adsorbs on the surface particle you can expect changes. How are the particles stabilized? Do you see a shifted lambda max? Particle agglomeration could also be happening.
Hello, please specify which culture media you use?
May be UV induced photochemical transformations of AgNPs cause your UV -VIS spectra change during the time.
Jack Silver You're right! I didn't even think about that, but that's a strong possibility.
Karen A. Darbinyan I'm using minimum essential media supplemented with 10 FBS and 1% penicilin-streptomyici .
Omar Gonzalez-Ortega I realize I didn't completely word my question properly. The spectra that is increasing is the medium alone. I measure the absorbance of just my medium alone over time, and then i measure the absorbance of my Ag NPs in cell culture medium over time. I don't see an increase in absorbance with the sample containing the nanoparticles (there is a red shift, but I'm pretty sure it's due to some level of aggregation). When I measure the absorbance of my medium alone over time the absorbance increases...as Jack Silver mentioned, it could possibly be due to evaporation and thus my concentration of proteins and medium compenents is increasing, but I'm not sure how I can determine if that's the source. It does seem to be the most tempting explanation though.
Try putting a mark on your flask, if it is evaporation, the liquid level will be below the mark.
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