Immobilization and sustained release of cefalexin on MCF nano-mesoporous material

Abstract

Mesocellular foams (MCF) silica nanometer mesoporous molecular sieve was successfully synthesized by hydrothermal route. This method used poly(ethylene glycol)-block-poly(propyl glycol)-block-poly(ethylene glycol) as template, tetraethyl orthosilicate as silica source and 1, 3, 5-trimethylbenzene as pore-expanding agent to prepare nano mesoporous MCF in acidic medium. The MCF mesoporous material was characterized by powder X-ray diffraction (XRD), infrared (IR) spectroscopy, low temperature nitrogen adsorption-desorption at 77 K, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The effects of pH, temperature, adsorbent dosage, cefalexin dosage and contact time on the immobilization of cefalexin were studied. Under the optimized conditions, MCF has the best effect on the drug immobilization. The maximum immobilization amount of cefalexin in MCF nano-mesoporous material is 498.8 mg/g. The behavior of adsorption of cefalexin by MCF belongs to multilayer heterogeneous adsorption, which accords with the Freundlich adsorption isotherm. In the adsorption process, all the ΔH⁰, ΔS⁰ and Gibbs free energy change ΔG⁰ are less than zero, indicating that the adsorption process is spontaneous, exothermic entropy decreasing reaction at ordinary temperature. Kinetic investigation showed that the adsorption process of cefalexin on MCF belongs to the pseudo-second-order kinetic process. The release laws of composite material cephalexin-MCF in the simulated body fluid, gastric and intestinal fluid were investigated, respectively. The maximum cumulative release rate in simulated body fluid was 99.4% at 18 h. The maximum cumulative release rate in the simulated gastric juice was 48.7% at 6 h and in the simulated intestinal fluid the maximum cumulative release rate of 61.9% was achieved at 8 h. These release processes satisfy the zero-order ordered kinetic process.

1. Behavior of the adsorption of cefalexin by MCF belonged to multilayer heterogeneous adsorption, according with the Freundlich adsorption isotherm.

2. Kinetic investigation showed that the adsorption process of cefalexin onto MCF belonged to the pseudo-second-order kinetic process.

3. The maximum immobilization amount of cefalexin in MCF nano-mesoporous material was 498.8 mg/g.

4. In the adsorption process, all the ΔH⁰, ΔS⁰ and Gibbs free energy change ΔG⁰ are less than zero, indicating that the adsorption process was spontaneous, exothermic entropy decreasing reaction at ordinary temperature.

5. Good sustained release effect of cefalexin in MCF was achieved in simulated body fluid.

Graphical Abstract

Keywords:

• cephalexin
• nano mesoporous MCF
• molecular sieve
• sustained release

Additional information

Funding

This research was supported by the project of the Education Department of Jilin Province, P. R. China. The authors wish to express their thanks（Project number：2010JTY10, KYC -JC-XM-2010-014）.