Drug Delivery from Therapeutic Self-Assembled Monolayers (T-SAMs) on 316L Stainless Steel

Dave   M.   Johnson; Anil      Mahapatro; Devang   N.   Patel; Marc   D.   Feldman; Arturo   A.   Ayon; C.   Mauli   Agrawal

Abstract

Delivery of therapeutic agents from self-assembled monolayers (SAMs) on 316L stainless steel (SS) has been demonstrated as a viable method to deliver drugs for localized coronary artery stent application. SAMs are highlyordered, nano-sized molecular coatings, adding 1-10 nm thickness to a surface. Hydroxyl terminated alkanethiol SAMs of 11-mercapto-1-undecanol ( – OH SAM) were formed on 316L SS with 48 hr immersion in ethanolic solutions. Attachment of ibuprofen (a model drug) to the functional SAMs was carried out in toluene for 5 hrs at 60 C using Novozume-435 as a biocatalyst. SAM formation and subsequent attachment of ibuprofen was characterized collectively using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measurements. The quantitative in vitro release of ibuprofen into a “physiological” buffer solution was characterized using reverse phase HPLC. Drug release kinetics showed that 14.1 μg of ibuprofen eluted over a period of 35 days with 2.7μg being eluted in the first day and the remaining being eluted over a period of 35 days. The drug release kinetics showed an increase in ibuprofen elution that occurred during first 14 days (2.7μg in 1 day to 9.5 μg in 14 days), following which there was a decrease in the rate of elution. Thus, functional SAMs on 316L SS could be used as tethers for drug attachment and could serve as a drug delivery mechanism from stainless steel implants such as coronary artery stents.

Keywords: Drug delivery, 316 L SS, stent, self assembled monolayers

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