Surface Modification of Functional Self-Assembled Monolayers on 316L Stainless Steel via Lipase Catalysis

• Published in: Langmuir Vol. 22; no. 3; pp. 901 - 905
• Main Authors: Mahapatro, Anil, Johnson, David M, Patel, Devang N, Feldman, Marc D, Ayon, Arturo A, Agrawal, C. Mauli
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 31-01-2006
• Subjects: Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Lipase - metabolism; Spectroscopy, Fourier Transform Infrared; Stainless Steel; Surface Properties; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Drug; Photoelectron; Self assembly; Monolayer; Modification; Oxygen; Catalytic reaction; Hydrocarbon; Methodology; Toluene; X ray; Carbonyl; Carbon; Esterification; Biocatalyst; Infrared spectrometry; Ester; Carboxylic acid; Stainless steel; Ibuprofen; Benzenic compound; Photoelectron spectrometry; Catalysis
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la052817h

Lipase catalyzed esterification of therapeutic drugs to functional self-assembled monolayers (SAMs) on 316L stainless steel (SS) after assembly has been demonstrated. SAMs of 16-mercaptohexadecanoic acid (−COOH SAM) and 11-mercapto-1-undecanol (−OH SAM) were formed on 316L SS, and lipase catalysis was used to attach therapeutic drugs, perphenazine and ibuprofen, respectively, on these SAMs. The reaction was carried out in toluene at 60 °C for 5 h using Novozyme-435 as the biocatalyst. The FTIR spectra after surface modification of −OH SAMs showed the presence of the CO stretching bands at 1745 cm-1, which was absent in the FTIR spectra of −OH SAMs. Similarly, the FTIR spectra after the reaction of the −COOH SAM with perphenazine showed two peaks in the carbonyl region, a peak at 1764 cm-1, which is the representative peak for the CO stretching for esters. The second peak at 1681 cm-1 is assigned to the CO stretching of the remaining unreacted terminal COOH. XPS spectra after lipase catalysis with ibuprofen showed a photoelectron peak evolving at 288.5 eV which arises from the carbon (CO) of the carboxylic acid of the drug (ibuprofen). Similarly for −COOH SAMs, after esterifiation we see a small, photoelectron peak evolving at 286.5 eV which corresponds to the C in the methylene groups adjacent to the oxygen (C−O), which should evolve only after the esterification of perphenazine with the −COOH SAM. Thus, lipase catalysis provides an alternate synthetic methodology for surface modification of functional SAMs after assembly.