Influence of Size and Shape of Silica Supports on the Sol⁻Gel Surface Molecularly Imprinted Polymers for Selective Adsorption of Gossypol.

Yingfang Jiang,Lulu Wang,Letao Zhang,Yagang Zhang,Keke Zhi,Akram Yasin

doi:10.3390/ma11050777

Abstract

The influence of various silica gel supports with different shapes and sizes on the recognition properties of surface molecular imprinted polymers (MIPs) was investigated. MIPs for selective recognition and adsorption of gossypol were synthesized via the sol–gel process with a surface imprinting technique on silica gel substrates. 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were chosen as the functional monomer and the cross-linker. The morphology and structure of the gossypol-MIPs were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a standard Brunauer–Emett–Teller (BET) analysis. Results indicated that the surface imprinted polymer layer facilitated the removal and rebinding of the template, and thus, achieved fast binding kinetics. Compared with the MIPs prepared on irregularly shaped silica with a broad particle size distribution, the MIPs using regularly-shaped silica of uniform size showed higher imprinting factor (IF), and the MIP made with a relatively larger sized (60 μm) spherical silica, demonstrated higher adsorption capacity compared to the MIPs made with smaller sized, spherical silica. The MIP prepared with 60 μm spherically shaped silica, featured a fast adsorption kinetic of 10 min, and a saturated adsorption capacity of 204 mg·g−1. The gossypol-MIP had higher selectivity (IF = 2.20) for gossypol over its structurally-similar analogs ellagic acid (IF = 1.13) and quercetin (IF = 1.20). The adsorption data of the MIP correlated well with the pseudo-second-order kinetic model and the Freundlich isotherm model, which implied that chemical adsorption dominated, and that multilayer adsorption occurred. Furthermore, the MIP exhibited an excellent regeneration performance, and the adsorption capacity of the MIP for gossypol only decreased by 6% after six reused cycles, indicating good application potential for selective adsorption of gossypol.

Highlights

The molecular imprinting technique is an attractive approach for molecular recognition with high affinity and selectivity [1,2,3,4,5]
Gossypol as the template molecule was very sensitive to alkaline substance, including ammonia hydroxide, so acetic acid was chosen as the catalyst
The results indicated that the molecular imprinted polymers (MIPs) exhibited high specificity for gossypol recognition

Summary

Introduction

The molecular imprinting technique is an attractive approach for molecular recognition with high affinity and selectivity [1,2,3,4,5]. This technology has been extensively investigated in various areas, such as stationary phase extractions, sensors, chromatographic separation, and as a mimic for enzyme catalysis [6,7,8,9,10,11]. The main disadvantages of this approach are poor site accessibility for target molecules, and the potential for trapped templates to generate “dead” sites, which result in incomplete template removal, and slow binding kinetics, as well as bleeding of the template.

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Results

Conclusion