Sumeet, put in this way your question seems to be too general. The bad wording is "all the things". An FTIR spectrum of a lipid contains huge amount of information. The same may be true for an FTIR spectrum of a drug. Thus, one obtains: "huge info" + "huge info" of spectral information about molecular structure of a lipid and of a drug. In a simplest case (no lipid-drug interaction) this info will be simply additive. In other cases, the resulting FTIR spectra of drug loaded lipid nanoparticles will contain info about lipid-drug interaction, etc., etc. In any case, for studying the system of yours one will need, for the start, separate FTIR spectra of the neat lipid (lipid nanoparticles) and of the neat drug. Then, having run an FTIR spectrum of the drug loaded lipid nanoparticles, you will know "all the things you should look for in the spectra" - provided, however, you already have a general task on your mind relevant to the system under investigation. These tasks may be, e.g.: Quantitative evaluation of the drug load in the lipid, interaction of the drug with the lipid, stability of the components in the composition, evaluation of the drug release rate, etc.

From a seriou side, I hope you already have the FTIR spectra of the neat components of the composition. Then, please, be a bit more specific in formulating the question. Yet, uploading a real spectrum along with the question is a good practice - since it helps to community to answer spectroscopy-related questions. Good Luck!

Dear Dr. Shchegolikhin thank you very much. I agree my question was in much broader sense. I am having FTIR Spectra of neat lipid and neat drug. I have already performed compatibility studies. I have taken FTIR Spectra of drug loaded nanoparticles too. I would like to evaluate interaction of drug and lipid, polymorphic changes in lipid after converting them into nanoparticles.

Sumeet, thanks for the prompt response. Taking into account what you've added, you should be prepared not only to assign "statically" FTIR absorption bands to corresponding molecular fragments of the drug or lipid matrix, but be able to differentiate polymorphs. It means that one have to interpret not only positions (frequencies) and intensities of the FTIR absorption bands, but possible changes in the bands shapes, bands frequencies shifts (to red or blue) and the bands intensities redistribution depending on the molecular structure changes. It is OK, and it can be done in FTIR spectroscopy. But my advice is, please, try to find an experienced spectroscopist nearby. Else, try to find a good Raman instrument with a good Raman guy. I feel that Raman measurements would be of much help in your case. Further, judging by your publications, you routinely use DSC in your studies. Then another advice: combine FTIR and Raman measurements with DSC ones. In parallel or directly. For instance, FTIR-ATR measurements nowadays are frequently made on heatable ATR crystals or plates. Raman measurements can be made even more easily by placing the sample on a heatable table. Thus you could follow the dynamics of the phase or structural transitions in your system, and this helps a lot to understand origins of the polymorphs.

Fortunately, there is a lot of publications on the topic at hand (drugs-LNPs-FTIR-Raman) in the web. Please find a couple of attached papers. Hope they would be of help methodologically (please take my apologies if you already red them). To finalize, a word of caution. In one of the papers the folks use KBr-disks technique for samples preparation before running FTIR spectra. It is a bad practice. Don't do that. KBr-disk technique disintegrates the sub- and molecular structure of such comparatively fragile systems like yours. Use ATR-FTIR, or gently smear your samples on a thin Si-chip plate and measure the sample in transmittance FTIR regime. Again, try to use Raman also to have "complete vibrational spectra" for your samples. Raman is extra good in that it doesn't require any sample preparation, i.e., is non-destructive and almost non-invasive. Good Luck!

Another promised paper from the web.

Dear Dr. Shchegolikhi thank you so much for your valuable reply. I'll go through the papers. The information given by you is exactly what I was looking for. I'll get back to you with queries.

By comparing the FTIR of the individual lipid carrier and the drug, you will know their characteristic absorption bands that are due to the fundtional groups present. Chemically and structurally analyze possible interactions between the functional group of the lipid and the drug once these are combined in a condition that will allow such interactions. For example, at pH below 7, what will be the configuration of the functional groups? same analysis should be done at pH above 7 and at pH equal to 7. Similarly, analyze what persists in various solutions, buffers, etc. Then, combine them at those different conditions and see the resulting FTIR. Qualitatively, you will be able to see appearance of new bands and changes in intensities from the individual spectrum of the lipid and the drug and when these are combined at various conditions. If you have the access to PM-FTIR, you'll be able to use it also to see the interaction of your drug and your lipid individually and in a mixture to the gold surface on the sample holder or where you deposit your sample to take the PM-FTIR.

Please see the supplemental section of this publication: Z. P. Aguilar, W. Vandaveer, I. Fritsch, “Self-contained Microelectrochemical Immunosensors for Small Volumes Using Mouse IgG as Model Analyte", Analytical Chemistry, 2002, 74,3321-3329. Although we did not use lipid or drug, you can infer the cahnges in the PM-FTIR signals that happens when two or more materials are combined or added in a layering fashion.