Surface Engineering of Transparent Cellulose Nanocrystal Coatings for Biomedical Applications

Abstract

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.

Cellulose Nano-Films as Bio-Interfaces

“…CNC has a low aspect ratio (diameter 5–10 nm, length 30–100 nm) compared to CNF (diameter 30–100 nm, length 1–2 μm). Prathapan et al spin coated a CNC layer on a uniaxially stretched polydimethylsiloxane (PDMS) precoated with poly(ethylene oxide) (PEO) (Prathapan et al, 2018). The uniaxially stretched PDMS created a surface with well-aligned grooves and low roughness.…”

“…AFM and contact angle measurements quantified the roughness and wettability of the dried blood stains onto the CNC interface (Figure 14). Blood antibody and antigen tests proved the CNC layer capability to provide high selectivity for blood testing diagnostics (Prathapan et al, 2018).…”

“…The before and after drying images were taken in transmittance mode. Reproduced with permission from Prathapan et al (2018).…”

“…Other drawbacks of paper are controlling the fiber mesh network, pore size, and fiber strength. These variables significantly affect diffusion and biomolecules loss in the fiber network, and its activity (Derikvand et al, 2016; Huang et al, 2017; Prathapan et al, 2018). Such challenges can be overcome by engineering cellulose nanoscale thin film as substrate for biomolecules immobilization.…”

“…The controlled crystalline/amorphous phase ratio provides different film swelling behavior which is useful to optimize the liquid content in films (Aulin et al, 2009). The advantage of anisotropically ordered cellulose fiber thin film or anisotropic film surface morphology is the directional distribution and functionality of the adsorbed biomolecules (Prathapan et al, 2018).…”