The Effect of SBA-15 Surface Modification on the Process of 18β-Glycyrrhetinic Acid Adsorption: Modeling of Experimental Adsorption Isotherm Data

Abstract

This study aimed at the adsorption of 18β-glycyrrhetinic acid (18β-GA), a pentacyclic triterpenoid derivative of oleanane type, onto functionalized mesoporous SBA-15 silica and non-porous silica (Aerosil®) as the reference adsorbent. Although 18β-GA possesses various beneficial pharmacological properties including antitumor, anti-inflammatory, and antioxidant activity, it occurs is small amounts in plant materials. Thus, the efficient methods of this bioactive compound enrichment from vegetable raw materials are currently studied. Siliceous adsorbents were functionalized while using various alkoxysilane derivatives, such as (3-aminopropyl)trimethoxysilane (APTMS), [3-(methylamino)propyl]trimethoxysilane (MAPTMS), (N,N-dimethylaminopropyl)trimethoxysilane (DMAPTMS), and [3-(2-aminothylamino)propyl] trimethoxysilane (AEAPTMS). The effect of silica surface modification with agents differing in the structure and the order of amine groups on the adsorption capacity of the adsorbent and adsorption efficiency were thoroughly examined. The equilibrium adsorption data were analyzed while using the Langmuir, Freundlich, Redlich-Peterson, Temkin, Dubinin-Radushkevich, and Dubinin-Astakhov isotherms. Both linear regression and nonlinear fitting analysis were employed in order to find the best-fitted model. The adsorption isotherms of 18β-GA onto silicas functionalized with APTMS, MAPTMS, and AEAPTMS indicate the Langmuir-type adsorption, whereas sorbents modified with DMAPTMS show the constant distribution of the adsorbate between the adsorbent and the solution regardless of silica type. The Dubinin-Astakhov, Dubinin-Radushkevich, and Redlich-Peterson equations described the best the process of 18β-GA adsorption onto SBA-15 and Aerosil® silicas that were functionalized with APTMS, MAPTMS, and AEAPTMS, regardless of the method that was used for the estimation of isotherm parameters. Based on nonlinear fitting analysis (Dubinin-Astakhov model), it can be concluded that SBA-15 sorbent that was modified with APTMS, MAPTMS, and AEAPTMS is characterized by twice the adsorption capacity (202.8–237.3 mg/g) as compared to functionalized non-porous silica (118.2–144.2 mg/g).

Entrapping Digestive Enzymes with Engineered Mesoporous Silica Particles Reduces Metabolic Risk Factors in Humans

“…[ 45–47 ] The pH of the enzyme solution is also a known important parameter that will influence enzymes adsorption. [ 38 ] In theory, increased entrapment could possibly be achieved by more sophisticated chemical modifications; [ 48,49 ] however, this would then move away from a material consisting of pure silica, which would alter the safety profile. In addition, we cannot rule out that other interactions might also be involved, such as adsorption of other GI enzymes, lipids, carbohydrates, and bile acids.…”

Surface Properties and Microstructures of Al-SBA-15 under Different Temperature Calcinations in Relation to Adsorption Performance

“…It indicated that SBA-15 and Al-SBA-15 x samples have ordered cylindrical pores. 32 Figure 2a shows that the volume of nitrogen adsorbed on the Al-SBA-15 x sample was smaller than that of the SBA-15 sample, and the volume of adsorbed nitrogen decreased with the increase in the calcination temperature. It indicated that the pore volume and specific surface area of the Al-SBA-15 x sample decreased with the increase in the calcination temperature.…”

“…As shown in Figure , the N 2 adsorption–desorption isotherms of SBA-15 and Al-SBA-15 x samples were of type IV according to the IUPAC classification and had a clear H1 type of hysteresis loop. It indicated that SBA-15 and Al-SBA-15 x samples have ordered cylindrical pores …”

“…38 In addition, the peak at 967 cm −1 on the SBA-15 sample was attributed to the stretching vibration peak of the non-bridging Si−OH group. 32 According to the comparison, it was found that the intensity of the bending vibration peak of adsorbed water and the tensile vibration peak of the −OH group decreased with the increase of the calcination temperature. In particular, the stretching vibration peak of the −OH groups almost disappeared on the Al-SBA-15 x sample roasted at 700 °C.…”

Sulfonic Acid Derivative-Modified SBA-15, PHTS and MCM-41 Mesoporous Silicas as Carriers for a New Antiplatelet Drug: Ticagrelor Adsorption and Release Studies

“…All these features make mesoporous silicas attractive sorbents that can be used as the carriers in drug delivery systems providing controlled drug release. Since their first usage as carriers for ibuprofen [ 14 ], mesoporous silicas have been employed for other anti-inflammatory drugs [ 18 , 19 ], antihypertensive drugs [ 20 , 21 ], antibiotics [ 22 , 23 ], vitamins [ 24 , 25 ] and many others [ 26 , 27 , 28 , 29 ]. Controlled drug release may result from physical or chemical drug–silica interactions, or can be triggered by external stimuli such as magnetic fields [ 30 ], the presence of enzymes [ 31 ] or the presence of light [ 32 ].…”