Chemical design of pH-sensitive nanovalves on the outer surface of mesoporous silicas for controlled storage and release of aromatic amino acid

• Published in: Journal of solid state chemistry Vol. 215; pp. 284 - 291
• Main Authors: Roik, N.V., Belyakova, L.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-07-2014; Elsevier
• Subjects: 2-Aminodiphenylamine; 4-Aminobenzoic acid; Activation; Adsorbents; AMINO ACIDS; Channels; CHEMICAL ANALYSIS; CHEMICAL COMPOSITION; Chemistry; Cross-disciplinary physics: materials science; rheology; DESORPTION; ETHANOL; Exact sciences and technology; General and physical chemistry; INFRARED SPECTRA; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Liquid phases; LIQUIDS; Materials science; Mesoporous silica; Nanostructure; NANOSTRUCTURES; pH-Controlled release; Physics; Porosity; Porous materials; granular materials; Selective modification; SILICA; Silicon dioxide; SOLUTIONS; Specific materials; Surface chemistry; Surface physical chemistry; X RADIATION; Selective modification; 4-Aminobenzoic acid; 2-Aminodiphenylamine; pH-Controlled release; Mesoporous silica; Encapsulation; Liquid state; Surface reaction; Chemical analysis; Reaction product; Template reaction; Desorption; Neutral solution; Inorganic adsorbent; Porous material; Silica; Mesoporosity; Template method; Ammonia; Aminoacid; pH; Chemical composition; Alcoholic solution; Infrared spectrum
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2014.04.018

Mesoporous silicas with hexagonally arranged pore channels were synthesized in water–ethanol-ammonia solution using cetyltrimethylammonium bromide as template. Directed modification of silica surface with N-[N′-(N′-phenyl)-2-aminophenyl]-3-aminopropyl groups was realized by postsynthetic activation of halogenoalkylsilicas, which have surface uniformly or selectively distributed 3-chloropropyl groups, with 2-aminodiphenylamine in the liquid phase. Chemical composition of silica materials was estimated by IR spectroscopy and chemical analysis of the surface products of reactions. Characteristics of porous structure of MCM-41-type silicas were determined from X-ray and low-temperature nitrogen ad-desorption measurements. Release ability of synthesized silica carriers was established on encapsulation of 4-aminobenzoic acid in pore channels and subsequent delivery at pH=6.86 and pH=1.00. It was found that N-[N′-(N′-phenyl)-2-aminophenyl]-3-aminopropyl groups block pore entrances at neutral pH preventing 4-aminobenzoic acid release. At pH=1.00 repulsion of positively charged surface aromatic amino groups localized near pore orifices provides unhindered liberation of aromatic amino acid from mesoporous channels.
Blocking of pores with N-[N′-(N′-phenyl)-2-aminophenyl]-3-aminopropyl groups at pH=6.86 for storage of ABA and opening of pore entrances at pH=1.00 for unhindered ABA liberation. [Display omitted]
•Modification of MCM-41 with N-[N′-(N′-phenyl)-2-aminophenyl]-3-aminopropyl groups.•Study of release ability of synthesized silica carriers in relation to amino acid.•Controlled blocking and opening of pores by amino groups at pH change were performed.•Retention of amino acid at pH=6.86 and its liberation at pH=1.00 was proved.