Amine-functionalized magnetic mesoporous silica nanoparticles for DNA separation

Highlights

• Fe₃O₄@SiO₂@EDPS with uniform size and good dispersity is prepared.

• We fabricated MMSN@EDPS with distinct core-shell–shell triple-layer composition.

• DNA adsorption capacity of MMSN@EDPS is considerable.

Abstract

We report a modified approach for the functionalized magnetic mesoporous silica nanoparticles (MMSN) using polymer microspheres incorporated with magnetic nanoparticles in the presence of cetyltrimethylammonium bromide (CTAB) and the core-shell magnetic silica nanoparticles (MSN). These particles were functionalized with amino groups via the addition of aminosilane directly to the particle sol. We then evaluate their DNA separation abilities and find the capacity of DNA binding significantly increased (210.22 μg/mg) compared with normal magnetic silica spheres (138.44 μg/mg) by using an ultraviolet and visible spectrophotometer (UV). The morphologies, magnetic properties, particle size, pore size, core-shell structure and Zeta potential are characterized by Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), Transmission electron microscopy (TEM), Powder X-ray diffraction (XRD), and dynamic light scattering (DLS). This work demonstrates that our MMSN own an excellent potential application in bioseparation and drug delivery.

Introduction

Magnetic core-shell silica nanoparticles have drawn much attention due to their unique magnetic property, uniform size distribution, monodispersity, functional surface and easy separation [1], [2]. Because of these advantages, remarkable efforts have been devoted to its potential applications in heterogeneous catalysis [3], drug delivery [4], adsorption of metal ions [5], DNA/protein purification [6], [7], [8], [9] and magnetic resonance imaging (MRI) [10]. To improve their performances in various applications, more and more researches focus on the preparation of uniform core-shell structure and the functionalization of the particle surface [11], [12].

More recently, preparation and application of porous silica has been a hot topic due to their larger surface area and specific porous channel, which can dramatically increase the binding capacity of target molecule onto the surface and pore [13], [14]. Furthermore, the tunable pore sizes with narrow distributions, well-defined surface properties, and low toxicity make mesoporous silica materials an ideal host for adsorption applications [15], [16]. Like MSN, surface modification of mesoporous silica provides a satisfied surface for ionic (electrostatic) interaction and thus enhances their adsorption ability by introducing different functional groups such as amines, thiols, and carbohydrates [17], [18]. The previous literatures also showed a variety of applications with mesoporous silica, such as heterogeneous catalyst [19], drug delivery [20], ions detection [21], and so on [22], [23].

DNA separation is an essential process in molecular biology and a fundamental step for subsequent sequencing, amplification, and biodetection [24], [25]. Several methods have been developed to extract DNA such as phenol/chloroform extraction, isopropanol precipitation, and formamide lysate method. Nowadays, employing various solid-phase supports for DNA extraction becomes more and more attractive, among which magnetic nanoparticles are preferred due to their easy manipulation and low cost [26], [27]. It has been demonstrated that the amine-functionalized surface would present positive charge at acidic condition due to the protonation of amine groups, which could bind phosphate groups of DNA through electrostatic interaction without any extra binding agents [28], [29]. Consequently, this offers an effective strategy to realize the rapid separation of DNA by using amine-functionalized magnetic nanoparticles. Although some researches have investigated the combination of mesoporous structure and surface functionalization of magnetic nanoparticles in the application of DNA adsorption [30], [31], the structures, surface morphologies, and maximum adsorption capacity of DNA can be further improved.

Herein, we propose amine-functionalized magnetic mesoporous silica nanoparticles (MMSN@EDPS) for the effective separation of DNA. We first prepared traditional surface-modified magnetic silica nanoparticles (MSN) with expected monodispersity and uniform size through a facile hydrothermal technique and the hydrolysis of tetraethoxysilane (TEOS). Besides, we successfully fabricated the magnetic mesoporous silica nanoparticles (MMSN) with uniform pore size by using cetyltrimethylammonium bromide (CTAB) as a surfactant, amine-functionalized surface and mesoporous structure were obtained in one step. DNA separation experiment was carried out with these particles to evaluate their adsorption ability and the maximal adsorption capacity was measured by ultraviolet and visible spectrophotometer. Meanwhile, the structures, properties, and surface morphologies of MMSN and MSN were investigated by Fourier transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM), Powder X-ray diffraction (XRD), Thermo gravimetric analysis (TGA) and Dynamic light scattering (DLS), respectively.