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Surface modified natural zeolite as a carrier for sustained diclofenac release: A preliminary feasibility study

de’ Gennaro B.1, Catalanotti L.1, Cappelletti P.2, Langella A.3, Mercurio M.3, Serri C.4Biondi M.5,6, Mayol L. 5,6
1 Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Piazzale V. Tecchio 80, 80125 Napoli, Italy
 2 DiSTAR, Università di Napoli Federico II, Via Mezzocannone 8, 80134 Naples, Italy
3 Dipartimento di Scienze e Tecnologie, Università del Sannio, Via dei Mulini 59/A, 82100 Benevento, Italy
4 Dipartimento di Scienze Biologiche ed Ambientali, Università di Messina, Piazza Pugliatti 1, Messina, Italy
5 Dipartimento di Farmacia, Università di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy
6 Interdisciplinary Research Centre on Biomaterials – CRIB – Università di Napoli Federico II, P.le Tecchio 80, Napoli, Italy
Colloids and Surfaces B: Biointerfaces, 130, 101-109, 2015
In view of zeolite potentiality as a carrier for sustained drug release, a clinoptilolite-rich rock from California (CLI CA) was superficially modified with cetylpyridinium chloride and loaded with diclofenac sodium (DS). The obtained surface modified natural zeolites (SMNZ) were characterized by confocal scanning laser microscopy (CLSM), powder X-ray diffraction (XRPD) and laser light scattering (LS). Their flowability properties, drug adsorption and in vitro release kinetics in simulated intestinal fluid (SIF) were also investigated. CLI CA is a Na- and K-rich clinoptilolite with a cationic exchange ability that fits well with its zeolite content (clinoptilolite = 80 wt%); the external cationic exchange capacity is independent of the cationic surfactant used. LS and CLSM analyses have shown a wide distribution of volume diameters of SMNZ particles that, along with their irregular shape, make them cohesive with scarce flow properties. CLSM observation has revealed the localization of different molecules in/on SMNZ by virtue of their chemical nature. In particular, cationic and polar probes prevalently localize in SMNZ bulk, whereas anionic probes preferentially arrange themselves on SMNZ surface and the loading of a nonpolar molecule in/on SMNZ is discouraged. The adsorption rate of DS onto SMNZ was shown by different kinetic models highlighting the factthat DS adsorption is a pseudo-second order reaction and thatthe diffusion through the boundary layer is the rate-controlling step ofthe process. DS release in an ionicmedium, such as SIF, can be sustained for about 5 h through a mechanism prevalently governed by anionic exchange with a rapid final phase.
Key-words: Adsorption kinetics; Cetylpyridinium; Clinoptilolite-rich rock; Diclofenac release; Kinetic models; Surfactant modified natural zeolite