Surface engineering of transparent cellulose nanocrystal coatings for biomedical applications

The concept of blood typing diagnostics using blood drops dried onto transparent cellulose nanocrystal thin film (~35 nm) coatings has been demonstrated. The substrate onto which the blood drops are dried plays an important role in such tests, depending on surface composition, roughness, and wettability. The drying profile of three different fluid dispersions: model latex particles, reagent blood cells, and whole human blood was studied on a range of different surfaces, including cellulose nanocrystals (CNCs), regenerated cellulose, and several hydrophobic polymers, in order to understand the role of surface chemistry, roughness, and fluid dispersion properties. The morphology of these surfaces was investigated using atomic force microscopy, roughness was calculated, and wettability was explored via contact angle measurement. The morphology of dried drops of human blood on different cellulosic surfaces was compared in order to understand the importance of cellulose crystallinity. Well-defined dried blood drops were observed on random and aligned CNC surfaces, facilitating visualization of individual cells. A simple antibody-antigen test was used to demonstrate the effectiveness of the CNC substrate for blood testing, showing high and reproducible selectivity.