Synthesis and characterization of a new magnetic restricted access molecularly imprinted polymer for biological sample preparation

https://doi.org/10.1016/j.mtcomm.2020.101002Get rights and content

Abstract

In this paper, a magnetic restricted access molecularly imprinted polymer (M-RAMIP) was proposed as a new sorbent for magnetic dispersive solid phase extraction of small molecules directly from untreated biological fluids. Fe3O4 nanoparticles were synthesized and functionalized with tetraethylorthosilicate and 3- (trimethoxysilyl) propyl methacrylate, resulting in Fe3O4@SiO2-MPS particles. A molecularly imprinted polymer selective to nicotine was synthesized on the Fe3O4@SiO2-MPS surface, resulting in a magnetic molecularly imprinted polymer (M-MIP). Finally, M-MIP particles were encapsulated with a bovine serum albumin (BSA) layer, resulting in the M-RAMIPs. A magnetic restricted access non-imprinted polymer (M-RANIP) was synthesized by the same procedure but in absence of the template molecule (nicotine). Adsorption kinetic and isotherm studies were best fitted to the fractional order and Sips models, respectively for kinetic and isotherm studies, attesting that the interactions occur by different mechanisms. The M-RAMIP presented higher adsorption capacities in comparison with M-RANIP. This is probably due to the presence of selective binding sites in the M-RAMIP. The selectivity test confirmed that the M-RAMIP was able to capture more nicotine than cotinine, caffeine, lidocaine, and cocaine in comparison with the M-RANIP, however, the covering with BSA reduced the selectivity in comparison with other MIPs from the literature. Protein exclusion capacities of about 79 % and 99 % were observed for M-MIP and M-RAMIP, respectively. M-RAMIP was used to extract nicotine from a human plasma sample, with precision and extraction recovery of about 16 and 27 %, respectively. Additionally, the same material was reusable in at least 50 extraction cycles with the same performance.

Introduction

Molecularly imprinted polymers (MIPs) are selective materials that are able to recognize a molecule or its analogues [1,2]. The selective binding sites are obtained by fixation of functional monomers in specific positions around a template molecule by using a cross-linker reagent. After the synthesis, the template is removed and the binding sites are exposed. Non-covalent interactions between template molecules and monomers have been the most frequent in MIP synthesis, mainly because they are easily breakable after polymerization. However, the selectivity is not so high compared to the covalent interaction-based MIPs [2]. Temperature can also be a critical parameter for the MIP selectivity, given that a lot of synthesis protocols are carried out at 60 °C or higher, whereas the MIP is used in extractions at room conditions. Innovative low temperature synthesis protocols can be highlighted, as for example the molecularly imprinted covalent organic frameworks [3]. MIPs have been often used as sorbents in different sample preparation techniques like conventional solid-phase extraction (SPE) [4,5], solid-phase microextraction [6,7], stir-bar sorptive extraction [8,9], microextraction by packed sorbent [10,11], magnetic dispersive SPE (d-SPE) [12,13], among others.

Despite the high selectivity of MIPs, their performance as a sorbent in SPE of untreated biological samples have not been very efficient. Proteins from biological fluids can be retained on the MIP surface, causing obstruction of selective binding sites and decreasing the adsorption capacity and selectivity [14]. The main approach to solve this problem has been the addition of protective coatings on the MIP surface to avoid protein sorption [15], resulting in restricted access molecularly imprinted polymers (RAMIPs). The first strategy to obtain RAMIPs was the fixation of hydrophilic monomers on the external surface of a conventional MIP, as for example glycerol monomethacylate in association with glycerol dimethacrylate [16,17], glycidyl methacrylate [18,19] and 2-O-meth-acryloylozyethoxyl-(2,3,4,6-tetra-O-acettyl-β-D-galactopyranosyl)-(1–4)-2,2,6-tri-O-acetyl-β-D-glucopyranoside [20]. The hydrophilic surface acts as a chemical barrier that makes the interaction of RAMIPs with protein from the sample difficult. At the same time, the template molecule can migrate through this hydrophilic layer and access the selective binding sites. Along the same line, particles of MIP with surface-grafted hydrophilic polymer brushes prepared by controlled radical precipitation polymerization techniques can be pointed out. These polymers are able to recognize small organic analytes in real, undiluted, biological samples (e.g., milks and serums), without the influence of the macromolecules [[21], [22], [23]]. Another strategy is the use of amphiphilic molecularly imprinted polymers, in which the hydrophobic and hydrophilic groups of the monomers are responsible for analyte capture and protein exclusion, respectively [24].

In 2013, Moraes at al. [25] proposed a new biocompatible RAMIP covered with bovine serum albumin (BSA). The authors observed that the presence of only hydrophilic monomers on the MIP surface was not sufficient to exclude all of the proteins from the samples. Thus, a MIP covered with these hydrophilic monomers was also involved with a BSA capsule chemically crosslinked with glutaraldehyde. The exclusion mechanism occurs when the pH of the medium is higher than the isoelectric point of both proteins from the sample and from the BSA layer. In this case, the proteins will acquire negative charges and be electrostatically repulsed. Exclusion capacities of about 100 % have been obtained with RAMIPs covered with the BSA layer, while maintaining their selectivity to the template and analogues [14,[26], [27], [28]].

Other modifications have also been carried out in conventional MIPs to simplify their use in sample preparation. The incorporation of magnetic nanoparticles in the polymer structure is a good example in which the material acquires magnetic susceptibility and it is used in d-SPE, wherein a magnet is employed to remove the particles from samples [29]. An important advantage for using magnetic molecularly imprinted polymers (M-MIPs) in d-SPE is the good interaction between the M-MIP and the samples. This gives higher extraction recoveries and good selectivity [30]. Besides, the use of a magnet to remove the sorbent from the sample is a very simple and efficient strategy. It avoids problems like the blockage of cartridges, columns, and tubes, which are often faced in conventional SPE. Several applications of M-MIPs for different analytes can be found in the literature [12,[30], [31], [32]].

Based on the relevant advantages of the RAMIPs and M-MIPs in terms of the capacity to exclude macromolecules, as well as the magnetic susceptibility, respectively, we believe that a new material with both characteristics can be very useful in magnetic d-SPE. In this way, this paper reports the development and characterization of a magnetic-restricted access molecularly imprinted polymer (M-RAMIP) selective to nicotine and the investigation of its performance in d-SPE of nicotine and its analogues from human plasma samples. Nicotine was chosen as a proof-of-principle drug to appraise the performance of the M-RAMIP.

Section snippets

Reagents and solutions

Nicotine, cotinine, caffeine, lidocaine and cocaine standards, iron (II) chloride tetrahydrate (FeCl2.4H2O), 3- (trimethoxysilyl) propyl methacrylate (MPS), tetraethylorthosilicate (TEOS), methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), 4′-azobis (4-cyanovaleric acid) (ABCVA), methanol, acetonitrile, and BSA were purchased from Sigma Aldrich® (Steinheim, Germany). Iron (III) chloride hexahydrate (FeCl3.6H2O) was obtained from Vetec® (Rio de Janeiro, Brazil). Ammonium hydroxide

Synthesis and characterization of the magnetic restricted access molecularly imprinted polymers

Fe3O4 magnetic nanoparticles (magnetite) were obtained by the reaction between Fe2+ and Fe3+ ions in alkaline medium. Afterwards, the treatment of Fe3O4 magnetic nanoparticles with TEOS resulted in Fe3O4@SiO2, which can be defined as Fe3O4 nanoparticles covered with a silanol polymeric network [39]. The silanol layer is important to decrease the dipolar attraction between the particles, which improves their dispersion capacity. Moreover, this silanol layer is used to anchor other chemical

Conclusions

An M-RAMIP was successfully synthesized and characterized, and its selectivity to nicotine was confirmed in comparison with cotinine, caffeine, lidocaine and cocaine. The main limitations of M-RAMIPs are: i) selectivity was not as high as in conventional MIPs (uncovered with BSA), probably because different molecules may be non-specifically retained by the BSA layer; and ii) the extraction recovery was not as high as in conventional MIPs, probably because the BSA layer obstructed some selective

CRediT authorship contribution statement

Tássia Venga Mendes: Conceptualization, Methodology, Investigation, Writing - review & editing. Lidiane Silva Franqui: Methodology, Investigation. Mariane Gonçalves Santos: Methodology, Investigation. Célio Wisniewski: Methodology, Investigation. Eduardo Costa Figueiredo: Supervision, Investigation, Writing - review & editing, Funding acquisition.

Declaration of Competing Interest

There are no conflicts to declare.

Acknowledgements

The authors are thankful to the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG, Belo Horizonte, Brazil), projects CDS-APQ-00638-17, CDS-PPM-00144-15 and CEX-APQ-01556-13; to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brasília, Brazil), project 483371/2012-2; and to the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brasilia, Brazil) for their financial support.

References (53)

  • P. Dramou et al.

    Development of novel amphiphilic magnetic molecularly imprinted polymers compatible with biological fluids for solid phase extraction and physicochemical behavior study

    J. Chromatogr. A

    (2013)
  • M.G. Santos et al.

    Analysis of tricyclic antidepressants in human plasma using online-restricted access molecularly imprinted solid phase extraction followed by direct mass spectrometry identification/quantification

    Talanta.

    (2017)
  • M.M. de Lima et al.

    On-line restricted access molecularly imprinted solid phase extraction of ivermectin in meat samples followed by HPLC-UV analysis

    Food Chem.

    (2016)
  • S. Ansari et al.

    Recent configurations and progressive uses of magnetic molecularly imprinted polymers for drug analysis

    Talanta.

    (2017)
  • F.F. Chen et al.

    Preparation of magnetic molecularly imprinted polymer for selective recognition of resveratrol in wine

    J. Chromatogr. A

    (2013)
  • F.-F. Chen et al.

    Preparation of magnetic molecularly imprinted polymer for selective recognition of resveratrol in wine

    J. Chromatogr. A

    (2013)
  • X. Kong et al.

    Synthesis and characterization of the core-shell magnetic molecularly imprinted polymers (Fe 3O 4@MIPs) adsorbents for effective extraction and determination of sulfonamides in the poultry feed

    J. Chromatogr. A

    (2012)
  • R.C. dos Santos et al.

    Characterization and application of restricted access carbon nanotubes in online extraction of anticonvulsant drugs from plasma samples followed by liquid chromatography analysis

    J. Chromatogr. B Anal. Technol. Biomed. Life Sci.

    (2017)
  • K.Y. Foo et al.

    Insights into the modeling of adsorption isotherm systems

    Chem. Eng. J.

    (2010)
  • C. Cui et al.

    Restricted accessed material-copper(II) ion imprinted polymer solid phase extraction combined with inductively coupled plasma-optical emission spectrometry for the determination of free Cu(II) in urine and serum samples

    Talanta

    (2013)
  • M.M.M. De Lima et al.

    On-line restricted access molecularly imprinted solid phase extraction of ivermectin in meat samples followed by HPLC-UV analysis

    Food Chem.

    (2016)
  • J. Wackerlig et al.

    Molecularly imprinted polymer nanoparticles in chemical sensing – synthesis, characterisation and application

    Sensors Actuators B Chem.

    (2015)
  • L. Ji et al.

    Al-MCM-41 sorbents for bovine serum albumin: relation between Al content and performance

    Microporous Mesoporous Mater.

    (2004)
  • C.E. Zubieta et al.

    Reactive dyes remotion by porous TiO2-chitosan materials

    J. Hazard. Mater.

    (2008)
  • A.R. Cestari et al.

    Determination of kinetic parameters of Cu(II) interaction with chemically modified thin chitosan membranes

    J. Colloid Interface Sci.

    (2005)
  • J. Gañán et al.

    Evaluation of a molecularly imprinted polymer for determination of steroids in goat milk by matrix solid phase dispersion

    Talanta

    (2014)
  • Cited by (0)

    View full text