Study on the host-guest interactions during caffeine encapsulation into zeolite

Abstract

The objective of this study was to investigate the equilibrium and kinetics behavior, sorption mechanism and host-guest interactions during caffeine (CAF) encapsulation in natural zeolite. The chemical, spectral and morphological properties of the newly obtained drug-carrier system were analyzed. Zeolite surface chemistry and morphology were characterized by determination of pH of zero charge, FT-IR and digital microscopy analyses. Equilibrium and kinetic sorption experiments and modeling were conducted to assess zeolite potential. Satisfactory extend of CAF encapsulation in the zeolite matrix (E 36.4%) was obtained. The probable host-quest interactions include Van der Waals interactions, H-bonds and chemical interactions between CAF functional groups and zeolite silanol groups, as well as parallel intraparticle diffusion of drug molecules in the mesopores of the mineral particles. The analyses of the experimental results indicated that natural zeolite could be successfully applied for encapsulating CAF.

Unpredicted photocatalytic activity of clinoptilolite–mordenite natural zeolite

“…Table 2 shows that the rate of caffeine adsorption is similar on NH (k 2 ¼ 13.5 Â 10 À6 g mol À1 s À1 ) and NFe (k 2 ¼ 14.2 10 À6 g mol À1 s À1 ). Comparison of these magnitudes with those obtained by Yaneva et al 39 for Bulgarian clinoptilolite is not possible since the authors performed their experiments with stirring at temperature and pH values different from ours. The adsorption equilibrium parameters K LF , n m , and b are also comparable in NH and NFe.…”

“…37 There are isolated reports of caffeine retention by zeolitic materials: zeolite NaY 38 and natural clinoptilolite from Bulgaria. 39 In our study, the photocatalytic decomposition of caffeine under UV-light irradiation was observed for the rst time on natural clinoptilolite-mordenite zeolite in form of millimetric granules sieved from the native tuff, and in the absence of a semiconductor. To reveal the photocatalytic activity of pristine zeolitic structures, a mixture of synthetic clinoptilolite and mordenite was studied too.…”

“…If caffeine is oriented in perfect correspondence with this window, its diffusion into the zeolite cavity could be unrestricted and this only in case the molecule is not solvated, which is difficult to achieve in aqueous solution. Thus, Yaneva's et al 39 graphical relationship between the caffeine dimensions and its encapsulation in clinoptilolite cavities needs to be claried because the authors disregarded the window size of the channels in the crystalline structure of the zeolite. Furthermore, they assumed that the tuff micro-and mesopore sizes measured by nitrogen adsorption corresponded to the zeolite cavity.…”

Drug Mass Transfer Mechanism, Thermodynamics, and In Vitro Release Kinetics of Antioxidant-encapsulated Zeolite Microparticles as a Drug Carrier System

“…Acidic and basic sites on the sorbent were determined by the acid-base titration (potentiometric titration) method proposed by Boehm. 19 The zero surface charge (pH PZC ) characteristics of natural zeolite were determined using the solid addition method. The procedure has been described elsewhere.…”

Low-temperature plasma-modified zeolite (LTPMZ) vs. natural Bulgarian zeolite (NBZ) – Comparative physicochemical, UV/VIS and FTIR studies

“…Our scientific team previously studied the equilibrium behavior of 4-nitrophenol during its adsorption on Romanian and Bulgarian zeolites from aqueous solutions [5], as well the host-guest interactions during caffeine encapsulation into a natural Bulgarian zeolite (NBZ) [6].…”