Biomolecular Adsorption in Microfluidics

Biomolecular adsorption in microfluidics usually refers to the nonspecific adsorption of biomolecules (amino acids, peptides, DNA, RNA, proteins, and cells) onto the surfaces of microfluidic devices. In this sense, this is often referred as... 

Biomolecular Adsorption in Microfluidics, Table 1 Advancing and static water contact angles on common materials used for microfluidic device surfaces [5,6, 18-41]... 

Biomolecular adsorption in microfluidics usually refers to the nonspecific adsorption of biomolecules (amino acids, peptides, DNA, RNA, proteins, and cells) onto the surfaces of microfluidic devices. In this sense, this is often referred as biofouling in microfiuidics. This causes many problems including reduced device sensitivity, poorer detection limits and selectivity, and diminished device lifetime. Among the above adsorbing species, proteins (including protective proteins of cells) cause the biggest problems resulting from irreversible adsorption and subsequent denaturation. 

To prevent biomolecular adsorption and water stiction, the surface materials for a microfluidic device should be carefully chosen with consideration of the actuation method (hydrodynamic or electrokinetic) and analytes to be manipulated (small solutes, DNA, proteins, and/or cells). Tables 2 and 3 summarize the surface materials that have been used in microfiuidic applications. 

In several types of microfluidic actuation, hydro-phobic surfaces have been used to control the rate of EOF or to manipulate droplets [3]. As noted earlier, however, it has not been possible to prevent protein adsorption that occurs through hydro-phobic interactions. One way around this problem is to make the surface hydrophobic to prevent water stiction, while utilizing electrostatic repulsion to prevent biomolecular adsorption. We have recently demonstrated this strategy in electrowetting-based microfluidic actuation [3]. 

The above summary addresses the adsorption of individual biomolecules in microfluidics. Biomolecular adsorption from real-world liquid samples such as blood will be much more complicated and probably almost impossible to prevent or control. However, we need to remember that biomolecular adsorption is not a problem unique to microfluidics people have been working on anti-fouling coatings since the 1950s [17]. The future... 

---