Rational Design of Thermoresponsive Elastin-Like Protein Monolayers for Nonenzymatic Cell Harvesting

A combined theoretical and experimental investigation presents a consistent parabolic potential model for the prediction and optimization of mammalian cell adhesion and detachment from genetically engineered thermoresponsive elastin-like protein (ELP) modified surfaces. Linear ELP chains concatenated with both thiol-gold surface-binding and RGD cell-binding domains serve as thermally responsive cell harvesting surfaces. This architecture of a 1:1 ratio of cell binding domain to linear polymer chain provides precise control of the chemical representation of the cell binding and thermoresponsive properties. The parabolic potential model of surface-grafted phase-separating polymers describing the ELP brush films, combined with surface-bound cell culture measurements, is used to analyze the effects of protein chain length N and surface area per chain σ. The cell binding fractions allow the calculation of system free energies, which are consistent with the parabolic potential model through identification of the underlying polymer lengths. This offers the ability for the model to identify optimal conditions that promote cell attachment and detachment. This model represents a quantitative framework for optimizing surface grafted protein layer thickness and cell displacement energy, which is a crucial technical step forward for programming of thermoresponsive biopolymer substrates for nonenzymatic cell harvesting.