I am attaching herewith the FTIR spectra of pure BSA, AuNPs (citrate capped) and BSA-AuNPs conjugates. It will be very helpful if somebody helps me in realizing the change in FTIR spectra for the two cases to confirm that binding of BSA with AuNPs.
From your data, I would say no binding has happened. However, it is suspicious that the spectrum of pure AuNP is nearly the same compared to pure BSA. Perhaps something went wrong during preparing your AuNP sample for measurement?
What were the concentrations of AuNP and BSA in your sample? The spectrum for the BSA-AuNPs conjugate does seem to suggest that either; no binding has occured as suggested above, or that the BSA constituents of your sample have absorbed the IR more strongly that the AuNP constituents, therefore they have not been detected in the resulting spectrum.
You could try taking 2nd derivatives of your spectra. This could show any extra peaks in the BSA+AuNP spectrum compared to the pure BSA spectrum, especially if the BSA spectrum is masking the AuNP. Alternatively, subtract the pure BSA spectrum from the BSA+AuNP spectrum. If there has been any binding, I would expect to see peaks at around 600-700 and 2100-2200cm-1 (based on your spectrum for pure AuNP).
Dear Charlotte, BSA protein (100 microlitres) of 1 mg/ml concentration has been added to AuNPs ( 1000 microlitres).
Dear Dutta, I believe that the concentration of AuNPs is not enough to produce differences in the spectrum, however, maybe there is some shift around 750 cm-1????? Try to normalize both spectra too
FTIR is not the best technique to do so. UV-Visible is most likely used in this purpose.
I would recommend you to use UV-Vis better or at least you could use it to validate the data.
FTIR spectra of BSA and BSA-gold nano look alike because the binding between nanoparticles with BSA through amide group is weak and closed carboxyl groups. So I would suggest you take the second derivative of FTIR spectrum of BSA-AuNPs. Bessides you could Measure Zeta potential of these samples to examine the binding.
Thank you very much for your reply.
Dear Dr Khaled I have taken UV-VIS spectra and zeta potential and obtained convincing results.
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