I am looking to analyse hormone concentrations in blood using Raman spectroscopy (specifically SERS with conductive silver paint), however I am having issues with the samples. I am leaving the samples to airdry, but I am getting saturation of the sample at very low laser power and exposure (10 seconds exposure at 1% and 5% laser power). I have noticed that cracks are appearing in both the whole blood and serum samples once dried, which are contributing to the saturation. I have tried thick and thin blood and serum smears as well as using wet samples and dry samples, but there is so much more variation in the spectrum, and some areas seem fine while others are still saturating. I have tried collecting blood with an anticoagulant but this appears to have no effect. I have also tried hormones in ethanol (standards) which, while they are not appearing cracked, I am still getting saturation at low exposure time and laser power. I am using a Renishaw inVia Raman - Bruker Innova AFM. Are there any suggestions as to how I can prevent cracks in the sample and/or why I cannot seem to reduce the saturation of the sample? Thank you!