Constrained cell penetrating peptides.

In this review we provide an overview of recent developments in the field of cell penetrating peptides (CPPs) on research that aims to achieve better control over their transduction properties - one of the big challenges - by means of restraining them. Three different constraining strategies are presented: triggerable activation, backbone rigidification and macrocyclization. Each of these methods have their opportunities in gaining control over CPP activity and selectivity.

Sensing cell adhesion using polydiacetylene-containing peptide amphiphile fibres.

Sensing cell adhesion by means of a colourimetric response provides an intuitive measure of cell binding. In this study polydiacetylene-containing peptide amphiphiles fibres were designed to sense cell adhesion by means of a colour change. The diacetylene-containing peptide amphiphiles were functionalised with the cell-binding motif RGDS, and subsequently mixed with non-functionalised diacetylene-containing spacer amphiphiles. The diacetylenes in the backbone of these fibres were polymerised using UV-light to give dark blue fibre solutions. Subsequent cell adhesion induced a colour change from blue to pink. The propensity of the RGDS fibres to change colour upon cell adhesion could be tuned by varying the C-terminal amino acid of the spacer amphiphile. In addition to this, by varying the RGDS density we found that the optimum colourimetric response was obtained for fibres with a 6 : 1 ratio of non-RGDS to RGDS amphiphiles.