Interactions at interfaces

Use Cases 

What are the effects of carbon quantum dots on the adsorption dynamics of proteins ? 

Reference: Lai, L.; Wei, X.-Q.; Huang, W.-H.; Mei, P.; Ren, Z.-H.; Liu, Y., Impact of carbon quantum dots on dynamic properties of BSA and BSA/DPPC adsorption layers. Journal of colloid and interface science 2017, 506, 245-254.

The effects of carbon quantum dots (CQDs) on the dynamic properties of bovine serum albumin (BSA) were investigated using the pendant drop profile analysis method (TRACKER™ by TECLIS). Furthermore, the effects of CQDs on the competitive adsorption of BSA and dipalmitoyl phosphatidylcholine (DPPC) were examined. These experiments showed that when the CQD concentration increases, a gradual increase in the adsorption rate of BSA molecules is observed. Moreover, the addition of CQDs resulted in a significant transition of kinetic dependencies of surface elasticity of BSA solution above a critical CQD concentration. The maximum surface elasticity value is attributed to the formation of tails and loops. When the dynamic surface properties are dominated by BSA molecules, the effects of CQDs on the surface properties of BSA/DPPC mixture are similar to those of BSA alone. However, when the surface film mainly consists of DPPC, CQDs can change the interfacial properties of the DPPC monolayer.

TECLIS product: TRACKER™ automatic drop tensiometer

Key words: dynamic surface tension, dynamic dilational rheology, protein, carbon quantum dots.

How to characterize the ability of proteins to penetrate an interface ? 

Reference: Meyers, N. L.; Larsson, M.; Vorrsjö, E.; Olivecrona, G.; Small, D. M., Aromatic residues in the C terminus of apolipoprotein C-III mediate lipid binding and LPL inhibition. Journal of lipid research 2017, 58 (5), 840-852.

The exclusion pressure represents the pressure starting from which there is no more adsorption of molecules at the interface while the decrease of surface tension induced by the presence of proteins is an evidence of their migration to the interface. Above a critical value of surface pressure Π_i, corresponding to the exclusion surface pressure Π_ex, this adsorption is no longer possible and no further lowering of surface tension is observed (ΔΠ=0). In this paper, the authors controlled the initial surface pressure with an automated drop tensiometer (TRACKER™ by TECLIS) by changing the drop volume; reducing the drop volume leads to a smaller surface area and hence a higher surface concentration and a higher surface pressure. These experiments allowed to determine the exclusion pressure of a protein which is an indicator of its ability to penetrate an interface.

TECLIS product: TRACKER™ automatic drop tensiometer, automatic CMC

Key words: Exclusion pressure (Π𝑒𝑥), protein, surface tension 

What is the effect of surfactant tail length in surfactant–mediated protein stabilization? 

Reference: Hanson, M. G., Katz, J. S., Ma, H., Putterman, M., Yezer, B. A., Petermann, O., & Reineke, T. M. (2020). Effects of Hydrophobic Tail Length Variation on Surfactant-Mediated Protein Stabilization. Molecular pharmaceutics, 17(11), 4302-4311.

One of the major drawbacks of the use of protein therapeutics is their lack of stability due to aggregation and denaturation. To limit these mechanisms, surfactants have been used: first, they compete with proteins for space at the interface hence limiting the aggregation and denaturation of proteins , secondly, surfactants can interact directly with proteins to stabilize then and prevent protein-protein interactions that would result in their aggregation. In this paper, the authors test the effect of the tail length  (ranging from 8 to 18 carbon ) of six FM100 derivatives on the stability of Immunoglobin G (IgG). Using an automatic drop tensiometer (TRACKER™ by TECLIS), surface tension measurements were performed, and the results showed that the FM100 series of surfactants  exhibits two types of surface tension decays that could correspond to an initial adsorption followed by rearrangements of the monolayer. Moreover, 14FM100 was found to be ideal having both a rapid and large initial decrease in surface tension. Additional DLS experiments showed that mid-tail lengths prevent IgG aggregation the most. These findings strongly suggest that 14FM100 is an optimal  candidate  for the stabilization of  IgG  being better at outcompeting IgG on the surface and preventing IgG aggregation compared to both shorter and longer hydrophobic tails.

TECLIS product: TRACKER™ automatic drop tensiometer

Key words: Surfactant, protein, tail length, surface tension, aggregation, competitive adsorption.