Effective methods for the selective passage of therapeutic molecules or probes through biological barriers are essential for the study of cellular functions. Cell penetrating cationic peptoids, based on a lysine like unit, were efficiently synthesised a combination of solid phase synthesis strategies and microwave heating.  A linear 7mer peptoid was thus prepared by direct solid phase synthesis and conjugated to both a peptide hormone (α- Melanocyte Stimulating Hormone, a 13mer peptide) and to peptide nucleic acids (9mer, 12mer and 15mer prepared using Dde/Mmt protected monomers) targeting tyrosinase mRNA. These conjugates were able to efficiently penetrate different cell lines (average uptake > 90%), and even more, to penetrate human skin, with the heptapeptoid carrier being able to deliver a 12mer PNA deep inside the dermis stratus. Antisense DNA oligomer (19mer, targeting tyrosinase mRNA) conjugated to the heptapeptoid carrier by a disulfide linkage was able to down-regulate tyrosinase expression, showing the potential of the carrier in delivering DNA into cells. Delivery of macromolecules such as protein and plasmid DNA were attempted. Heptapeptoids functionalised with a tetradentate Ni²⁺ ligand were tested for the delivery of hexahistidine (His₆) tagged GFP protein into cells, while 3 generations of a novel peptoid dendrimer were prepared and tested for the cellular delivery of DNA.