The value of amino acids and vegetable oil derivatives as raw materials for the preparation of surfactants was recognized as soon as they were discovered early in the last century. Amino acid-based surfactants, which have an amino acid residue as a hydrophilic moiety, are reviewed with respect to their synthesis, properties and some applications. The review covers three main categories of amino acid-based surfactants: N^α-acyl, N-alkyl amide and O-alkyl ester derivatives among the linear or single chain amino acid-based surfactants; N^α, N^ω-bis(N^α-acylarginine)α,ω-alkylendiamides, which are gemini amino acid-based surfactants; and 1-monoacyl-rac-glycero-3-O-(N^α-acetyl-L-amino acid) and 1,2-diacyl-rac-glycero-3-O-(N^α-acetyl-L-amino acid), both amino acid-based surfactants with glycerolipid-like structures.

The rapid increase of drug resistant bacteria makes necessary the development of new antimicrobial agents. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds given that they can be prepared from renewable raw materials. In this review, we discuss the structural features that promote antimicrobial activity of amino acid-based surfactants. Monocatenary, dicatenary and gemini surfactants that contain different amino acids on the polar head and show activity against bacteria are revised. The synthesis and basic physico-chemical properties have also been included.

Nanoparticles with pH-sensitive behavior may enhance the success of chemotherapy in many cancers by efficient intracellular drug delivery. Here, we investigated the effect of a bioactive surfactant with pH-sensitive properties on the antitumor activity and intracellular behavior of methotrexate-loaded chitosan nanoparticles (MTX-CS-NPs). NPs were prepared using a modified ionotropic complexation process, in which was included the surfactant derived from N(α),N(ε)-dioctanoyl lysine with an inorganic lithium counterion. The pH-sensitive behavior of NPs allowed accelerated release of MTX in an acidic medium, as well as membrane-lytic pH-dependent activity, which facilitated the cytosolic delivery of endocytosed materials. Moreover, our results clearly proved that MTX-CS-NPs were more active against the tumor HeLa and MCF-7 cell lines than the free drug. The feasibilty of using NPs to target acidic tumor extracellular pH was also shown, as cytotoxicity against cancer cells was greater in a mildly acidic environment. Finally, the combined physicochemical and pH-sensitive properties of NPs generally allowed the entrapped drug to induce greater cell cycle arrest and apoptotic effects. Therefore, our overall results suggest that pH-sensitive MTX-CS-NPs could be potentially useful as a carrier system for tumor and intracellular drug delivery in cancer therapy.