The cellular uptake of biologically relevant cargos is a longstanding challenge in drug discovery programs. Thiol-mediated uptake has emerged in recent years as a highly effective way of entering cancer cells using thiol/disulfide dynamic covalent chemistry with cell-surface proteins. In the presented thesis, cyclic oligochalcogenides are used as thiol-mediated uptake transporters. Multivalency/oligomeric effects of cyclic oligochalcogenides on cellular delivery are studied as well as their structure-penetration relationships. The most powerful transporters "asparagusic trimers" were used as new privileged scaffolds for thiol-mediated delivery of proteins in 2D cell cultures. On the other hand, their ability to transport proteins and quantum dots into deep tissues has been probed using cancer cell spheroid models combined with high-content high-throughput microscopy imaging techniques. Their particularly efficient penetration in deep tissues is an intrinsic property of thiol-mediated uptake and therefore should increase its general significance and usefulness in the future.