Figure 4. .

Thermogravimetric analysis (TGA) curves of OPS-CO₂H (oxidized porous silicon with carboxylic acid functional surface), ads-OPS:DNR (oxidized porous silicon particles containing physically adsorbed daunorubicin), and cov-OPS:DNR (oxidized porous silicon particles containing daunorubicin covalently attached to the pore walls as described in the text). Weight percent is reported relative to initial weight of sample, prior to heating. The initial decrease in weight at 120°C is attributed to the loss of water from the sample. The decrease in weight observed from 120°C to 600°C is attributed to the organic functionalization and the drug loaded into the particles. The weight loss difference obtained by subtraction between particles before (OPS-CO₂H) and after drug loading (ads-OPS:DNR or cov-OPS:DNR) accounts exclusively for the organic matter corresponding to the drug loaded into the particles.