title: pH sensitive silica nanotubes as rationally designed vehicles for NSAIDs delivery.
abstract: A novel pH-sensitive drug delivery system based on functionalized silica nanotubes was developed for the incorporation of non-steroidal anti-inflammatory drugs (NSAIDs), aimed at a tailored drug release in acidic conditions characteristic of inflamed tissues. Silica nanotubes (SNTs) were synthesized by a nanoporous alumina template assisted sol-gel method. Inner surfaces were physically and chemically modified to improve both the functionalization and subsequent incorporation of the drug. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) were used to characterize the designed nanocarriers and their functionalization. To achieve the highest degree of functionalization, three types of aminosilanes were tested and calcination conditions were optimized. APTES was shown to be the most effective aminosilane regarding the functionalization of the SNTs' inner surface and an adequate calcination temperature (220°C) was found to attain mechanical stability without compromising functionalization efficiency. Finally, the incorporation of naproxen into the nanotubes was accessed by fluorescence measurements and drug release studies were performed, revealing that the electrostatic linkage ensures effective release of the drug in the acidic pH typical of inflamed cells, while maintaining the SNT-drug conjugates stable at the typical bloodstream pH.
authors.affiliation: IN and IFIMUP, Institute of Nanoscience and Nanotechnology, Porto, Portugal.
authors.forename: Célia T
authors.initials: CT
authors.lastname: Sousa
authors.forename: Cláudia
authors.initials: C
authors.lastname: Nunes
authors.forename: Mariana P
authors.initials: MP
authors.lastname: Proença
authors.forename: Diana C
authors.initials: DC
authors.lastname: Leitão
authors.forename: José L F C
authors.initials: JL
authors.lastname: Lima
authors.forename: Salette
authors.initials: S
authors.lastname: Reis
authors.forename: João P
authors.initials: JP
authors.lastname: Araújo
authors.forename: Marlene
authors.initials: M
authors.lastname: Lúcio
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry* / Q000378:metabolism; D004337:Drug Carriers / Q000138:chemical synthesis*; D004339:Drug Compounding; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D009288:Naproxen / Q000737:chemistry* / Q000378:metabolism; D011437:Propylamines; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013696:Temperature
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004337:Drug Carriers; D011437:Propylamines; D012821:Silanes; D009288:Naproxen; D012822:Silicon Dioxide; C477625:amino-propyl-triethoxysilane; D000537:Aluminum Oxide