The Effect of Nanomorphology as Quantified via the K-Index on the Drug Delivery Properties of Isocyanate-Derived Aerogels

This study explores the potential to predict the drug-loading and release profiles of aerogels based on their morphologies: a milestone in drug delivery research, which can help save time and cost in formulating new aerogel drug carriers and cut-down evaluation of the drug delivery capabilities of aerogels to a few experimental runs. Polyurea (PUA) and poly(isocyanurate-urethane) (PIR-PUR) aerogels were used as model systems, while 5-fluorouracil (5-FU) and paracetamol (PM) were used as model drugs. These model systems were chosen because they can be synthesized into different morphologies, which can be quantified by the so-called K -index (water contact angle divided by porosity). The model drugs were loaded onto the aerogels using a physical adsorption method, and the drug-loaded aerogels were characterized with FT-IR, SEM, DSC, XPS, and UV spectroscopy. Our study revealed that drugs are loaded onto the surfaces of macropores, mesopores, or fibers depending on the morphology being studied and can be released quickly or slowly depending on the location of the drugs and different surface energies associated with different pore surfaces within the different morphologies onto which the drugs were loaded. Comparing all the morphologies studied, the various nanoparticle-based nanostructures ( K = 1.2–1.5) and entangled nanofibers ( K = 1.6) could uptake larger amounts of drug; fused nanoparticles ( K = 1.5) and bicontinuous nanostructures ( K = 2.2) are more suitable for fast-release formulations; morphologies with K -indexes equal to 1.2, 1.3, and 1.6 and those containing nanoparticles entangled with different ratios of nanofibers ( K = 1.7–2.0) are more suitable for sustained-release formulations; and nanofibrous morphologies ( K = 1.6) are more suitable for controlled-release formulations.