Manipulating Cell Migration and Proliferation with a Light‐Activated Polypeptide

Abstract

Remote control of cells: A polypeptide has been made that stimulates proliferation and migration of cells upon photochemical activation. This light-activated polypeptide enables spatially defined control of cell populations at the scale of tissue organization; this is accomplished without physically contacting the cells or modifying their substrate. Polypeptide growth and differentiation factors modulate a wide variety of cell behaviors and can be used to manipulate cells in vitro for tissue engineering and basic studies of cell biology. To emulate in vitro the spatial aspect of growth factor function, new methods are needed to generate defined spatial gradients of activity. Polypeptide factors that are engineered to be activated with light provide a method for creating concentration gradients with the fine precision in space and time with which light can be directed. As a first test of this approach, we have chemically synthesized a polypeptide with the sequence of epidermal growth factor in which a critical glutamate is "caged" with a photoremovable group. Photolysis of this polypeptide afforded maximal mitogenic and chemokinetic activity at concentrations at which the caged factor was inactive. Spatially resolved photolysis of the factor resulted in spatial patterning of fibroblasts. This system will be useful for ex vivo tissue engineering and for investigating the interactions of cells with their matrix and the role of chemical gradients in biological pattern formation.

Mechanical approach to chemical transport

“…This situation arises in practical applications. Experiments are coming online that can expose nonhomogeneous systems such as live cells or electrochemical interfaces to programmable spatiotemporal patterns of temperature, chemical composition, osmotic pressure, light exposure, and other variables (18)(19)(20)26).…”

“…The approach does not consider convection or Fourier heat flow in the system, and transport phenomena or chemical reactions should not perturb the externally imposed temperature gradients. Nevertheless, the general model presented here may be used to describe the processes besides traditional physical chemistry applications such as live cell kinetics, electrochemical transport, or spatially patterned perturbation of self-assembled monolayers with simultaneous reactions and diffusion (18)(19)(20)27). Furthermore, the random walk view of consumption (31) and various economic optimization problems can be formulated based on Lagrangians with logarithmic terms.…”

“…We believe that such a model could be useful for describing transport in electrochemistry, spatially heterogeneous kinetics, biophysics, and other areas where position-dependent forces are applied to a system. For example, temperature jumps and photoexcitation patterned with spatial light modulators, chemical and osmotic pressure gradients, or other complex perturbations can nowadays be applied to nonhomogeneous systems ranging from selfassembled monolayers to live cells (18)(19)(20) to induce transport phenomena.…”

4-Hydroxytamoxifen probes for light-dependent spatiotemporal control of Cre-ER mediated reporter gene expression

“…HPLC: t R = 10.37, 10.54 min; purity 498% (quantitative deprotection). MS (ESI) m/z (relative intensity, %) = 669.4 (11) ). II.…”

In situ cell manipulation through enzymatic hydrogel photopatterning

“…Using a generic protein binding strategy, our method can be applied to virtually any kind of protein, and makes it a powerful alternative to selectively blocking the active site of biomolecules by photolabile groups 31,32 . The latter approach is straightforward for peptides but cumbersome in the case of full-length proteins.…”