Screening of a molecularly imprinted sol–gel library for nafcillin recognition

Properties of tailored imprinted sol–gels are extremely dependent on the synthesis conditions and on the nature of the reagents used due to the diversity of combinatory interactions among the sol–gel components and the large number of chemical requirements for the sol–gel process. In this paper, methyltrimethyl orthosilicate was used as precursor to create molecularly imprinted polymers against the β-lactamic antibiotic nafcillin under different experimental conditions. A 22 member–library of imprinted sol–gels against nafcillin, and the respective control materials, was produced. Screening of the library members was performed by room temperature phosphorescence (RTP) flow-injection analysis and by batch RTP re-binding assays. A 2² factorial experimental design was also performed in selected sub-libraries of imprinted sol–gels as a function of the template and the additive concentrations, both using acid and basic catalysis.     

Synthesis and characterization of sol–gel-derived molecular imprinted polymeric materials for cholesterol recognition

The sol–gel-derived host matrices are well known for biosensor applications where various types of organic and biological molecules can be immobilized and can act as recognition elements. The molecular imprinting technology is an attractive alternative method where expensive and labile biorecognition elements can be replaced by molecular imprinted polymers (MIPs), which are capable of recognizing a target molecule of an interest. In the present study, hybrid sol–gel MIPs were synthesized in the form of crushed powder (CP) by both non-hydrolytic and hydrolytic method for cholesterol recognition. These MIPs were characterized by scanning electron microscopy (SEM), fourier transform-infrared (FT-IR), liquid chromatography-mass spectrometry (LC–MS) and nitrogen adsorption–desorption isotherm measurements. The template molecule was extracted by means of soxhlet extraction and calcination method. The cholesterol adsorption experiments were performed by using non-imprinted (NI) and extracted crushed powder (ExCP) and the percentage of adsorption was determined by measuring the residual quantity in the analyte solution using Liebermann-Burchard (L-B) reagent. The adsorption studies with non-imprinted crushed powder (NICP) showed interference with L-B reagent as well as non-specific binding between analyte molecules and silica matrix. The percentage of adsorption or rebinding was found to be higher for phenyl triethoxysilane (PhTEOS)-derived ExCP (composition 3) which was synthesized by the aqueous sol–gel processing method at low pH as compared to PhTEOS-derived (composition 1) and 3-aminopropyltriethoxysilane (APTES)-derived ExCP (composition 2) prepared by non-hydrolytic method. The reusability of used ExCP after re-extraction was also investigated. The various factors affecting rebinding of template molecules were discussed along with interference study. The study provided information on molecular imprinting of cholesterol in sol–gel matrix and highlighted the importance of characterization of MIPs before applying it for sensing applications.     

Preparation of a novel molecularly imprinted polymer by the sol–gel process for sensing creatinine

A novel molecularly imprinted polymer (MIP) was prepared and used as an artificial receptor for creatinine (Cre). A sol–gel process was used to prepare the MIP. Tetraethoxysilane (TEOS) was employed as the crosslinker for the formation of a silica matrix for the MIP. Aluminum ion (Al³⁺) was chosen as the dopant to generate Lewis acid sites in the silica matrix for interactions with Cre. Through the sol–gel process, a polymeric matrix with memory sites for Cre was obtained, and this is mentioned here as the molecularly imprinted polymer for creatinine (MIP_Cre). The imprinting efficiency of MIP_Cre was evaluated by contrasting the adsorbed amount of Cre by MIP_Cre with that by the corresponding non-imprinted polymer (NIP). Creatine (Cn), N-hydroxysuccinimide (NHS), and l-tyrosine (l-tyr) were selected as interferences to study the selectivity of the MIP_Cre. The interference studies were also conducted using binary mixtures, such as Cre/Cn, Cre/NHS, and Cre/l-tyr. All these studies reveal that the MIP_Cre possess a remarkable affinity for Cre. The crucial role of Al³⁺ in this system is discussed in detail. Furthermore, the effects of concentrations of Al³⁺ and TEOS on the adsorbed amount of Cre by MIP_Cre were also investigated.     

Preparation and characterization of protein molecularly imprinted polysiloxane using mesoporous calcium silicate as matrix by sol–gel technology

Calcium silicate particles containing mesoporous SiO₂ on the surface (CaSiO₃@SiO₂) were prepared by acid modification of calcium silicate with diluted hydrochloric acid. Bovine serum albumin (BSA) molecularly imprinted polysiloxane (MIP) was synthesized using silane as the functional monomer, BSA as the template and CaSiO₃@SiO₂ particles as the matrix in an aqueous phase. SEM, granulometry, FT-IR and BET analysis were used to characterize the protein MIP. Influence factors on the rebinding capacity of the MIP were investigated, such as the pH in treating CaSiO₃, eluent type and silane proportion. The mass of BSA loading and rebinding on CaSiO₃@SiO₂ and MIP was investigated. The adsorption and recognition properties of the MIP were evaluated and the results showed that the MIP exhibited an obvious improvement in terms of rebinding capacity for BSA as compared with non-imprinted polysiloxane (NIP). BSA imprinted polysiloxane could recognize the template protein by using Lys, Ova, Hb, and Glo as control proteins, and the selectivity factor (β) was above 2.3. The rebinding capacity of BSA imprinted polysiloxane for BSA reached 81.31 mg/g, which was 2.25 times of NIP.     

Synthesis and characterization of a novel organic–inorganic hybrid supramolecular recognition material and its selective adsorption for cesium

To separate Cs(I) from highly active liquid waste, a macroporous silica-based 25, 27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂–P, was synthesized and characterized by SEM, FT-IR, and TG-DSC. The adsorption properties of BiPCalix[4]C6/SiO₂–P and a macroporous polymer-based supramolecular recognition composite, BiPCalix[4]C6/XAD-7, were compared. It was found that BiPCalix[4]C6/SiO₂–P exhibited better adsorption ability and faster adsorption dynamics than BiPCalix[4]C6/XAD-7. The adsorption isotherm of Cs(I) onto BiPCalix[4]C6/SiO₂–P was studied at 298 K and it was well described by Langmuir isotherm model. The complex composition between BiPCalix[4]C6/SiO₂–P and Cs(I) was determined as 1:1 type by investigating the effect of the concentrations of BiPCalix[4]C6, Cs(I), and H⁺ on the adsorption. Meanwhile, the selectivity of BiPCalix[4]C6/SiO₂–P towards Na(I), K(I), Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) was investigated.     

Photoregulated uptake and release of drug by an organic–inorganic hybrid sol–gel material

A photo-responsive molecularly imprinted sol–gel organic-inorganic hybrid material prepared by covalent imprinting of the template-functional monomer complex formed between 4,4′-dihydroxylazobenzene and ibuprofen was developed to explore the photo-regulated uptake and release of drug by a silicate-based smart molecularly imprinted materials. After imprinting, the template molecules (ibuprofen) were removed via hydrolysis in acid, and accurate cavities were left, which could be used as the receptor recognition sites for ibuprofen. The new organic–inorganic hybrid material shows specific affinity to ibuprofen and reversible uptake and release of ibuprofen upon alternate irradiation at 365 and 440 nm, respectively. The favorable binding strength of the imprinted receptor sites in the molecularly imprinted polymer (MIP) for ibuprofen is found to be 2.28 × 10³ M⁻¹. Density of receptor sites in the MIP material was 4.0 μmol/g—MIP.     

Design and fabrication of single mode rib waveguides using sol–gel derived organic–inorganic hybrid materials

Multi-layer buried rib waveguides were fabricated using sol–gel derived photopatternable organic–inorganic hybrid materials through multi-step spin coating and photolithography. A single mode circular waveguide at 1,550 nm was designed and fabricated using the equivalent refractive index method. Propagation loss in the order of 1.0 dB/cm was measured by cutback method. Waveguide thermal stability and thermo-optic coefficient were investigated using thermogravimetric analysis (TGA) and spectroscopic ellipsometry, respectively. Results suggest that the single mode waveguide can be used to develop thermal optical devices such as thermo-optic switches.     

Preparation of high selective molecularly imprinted polymers for tetracycline by precipitation polymerization

High selective molecularly imprinted polymers(MIPs) for tetracycline have been prepared by precipitation polymerization. Effects of monomer and solvent,the ratio of monomer and template and the characterization of the polymer were investigated by frontal chromatography and selectivity experiment.The results clearly indicated that the polymer,which had the highest molecular recognition abilities for tetracycline antibiotics,had been received.     

Biodegradable and bioactive hybrid organic–inorganic PEG-siloxane fibers. Preparation and characterization

A mixture of triethoxysilanefunctionalized poly(ethylene glycol), f-PEG, and tetraethoxysilane, TEOS, was used as precursors in the preparation of continuous hybrid f-PEG-siloxane sol–gel derived fibers. The fibers were spun by extrusion through a spinneret. The thus prepared fibers had a diameter of 20–50 m. ²⁹Si-CPMAS NMR measurements confirmed that the functionalized PEG is incorporated into the siloxane network through covalent bonds. The hybrid fiber elasticity was much higher than that of fibers spun from sols with TEOS as the only source for silica. However, the f-PEG chain length plays a crucial role for the spinnability of the sol, since, as a result of bridging flocculation, macroscopic phase separation occurred readily with increasing chain length of the f-PEG. The fibers were shown to be effective substrates for the nucleation and growth of bone-like hydroxyapatite.     

Synthesis and characterizations of new negatively charged organic–inorganic hybrid materials: effect of molecular weight of sol–gel precursor

A series of negatively charged hybrid (organic–inorganic) materials were prepared through sol–gel process. The alkoxysilane-containing sol–gel precursors PEO-[Si(OEt)₃]₂SO₃H were obtained by endcapping polyethylene oxide (PEO) of different molecular weights with 2,4-diisocyanate toluene (TDI), followed by a coupling reaction with phenylaminomethyl triethoxysilane (ND-42) and sulfonation afterwards. The negatively charged precursors were then hydrolyzed and condensed to generate hybrid sol–gel materials, which were characterized by IR, TGA, XRD as well as the conventional ion exchange measurements. The results showed that in the hybrid sol–gel precursors PEO-[Si(OEt)₃]₂SO₃H organic PEO component was incorporated with alkoxysilane-containing ND-42 covalently. As the molecular weight of the precursors increased, thermal stability and cation-exchange capacity of the hybrid material decreased. All the hybrid materials were amorphous and those prepared from higher molecular weight precursors were flexible.     

Preparation and characterization of TiO<Subscript>2</Subscript> hybrid sol for UV-curable high-refractive-index organic–inorganic hybrid thin films

In this study, UV-curable hybrid thin films were successfully prepared from TiO₂ and TiO₂ hybrid sols containing the acrylic monomer DPHA on PMMA substrates. The prepared TiO₂ and TiO₂ hybrid sols showed long-term storage stability and can provide operating control for the preparation of high-refractive-index hybrid thin films. The existence of interaction between the TiO₂ particle and the coupling agent was evidenced by FT-IR and UV–visible spectra. All hybrid thin films showed good adhesion to the PMMA substrate with refractive index falling over the range 1.64–1.77. These results suggested the potential application of present TiO₂ hybrid films in optical devices, such as anti-reflective coatings.     

Biodegradable and biocompatible inorganic–organic hybrid materials. I. Synthesis and characterization

The hydroxyl or vinyl end-groups of linear or three-arm star-shaped poly(ε-caprolactone) (PCL) chains have been derivatized into triethoxysilane groups reactive in the sol-gel process. New transparent hybrid materials that combine tetraethylorthosilicate (TEOS) and PCL known for biodegradability and biocompatibility have accordingly been prepared. The sol-gel process is, however, limited by the early vitrification of the reactive system. However, thermal posttreatment can overcome these diffusional and/or kinetic limitations as assessed by a set of analytical methods. The thermal stability of PCL is improved by incorporation into the silica network. Conversely, the thermal stability of the ceramer depends on the effective PCL content. The extent of PCL incorporation into the silica network depends on PCL molecular weight, number, and reactivity of the PCL functional groups. IR spectroscopy has shown that hydrogen bonding occurs between the ester groups of PCL and residual OH groups of the silicate component. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2295–2309, 1997     

Optical spectroscopy methods for the characterization of sol–gel materials

Journal of Sol-Gel Science and Technology - In this paper, structural, optical, and electrical features of undoped and copper-incorporated nickel oxide (Cu/NiO) films with different mole ratios...     

Preparation and evaluation of an ion imprinted sol–gel material for selective solid-phase extraction of Ni(II)

An ion imprinted silica sorbent was prepared using a sol–gel process for selective extraction of Ni(II) ions from water samples. Bis(dibenzoylmethanto)nickel(II) complex was used as template; phenyltrimethoxysilane and 3-aminopropyltriethoxysilane as functional monomers and tetraethylorthosilicate as reticulating agent. The material was packed in solid-phase extraction (SPE) column. The effect of sampling volume, elution conditions, sample pH and sample flow rate on the extraction of Ni ions from water samples were studied. The relative selectivity coefficients of imprinted sorbent for Ni(II)/Co(II), Ni(II)/Cu(II) and Ni(II)/Cd(II) were 23.7, 30.3 and 24.4, times greater than non-imprinted sorbent, respectively. The relative standard deviation of the eight replicate determinations of Ni(II) was 4.2%. The detection limit was 0.9 µg L^?1 using flame atomic absorption spectrometry. The developed method was successfully applied to the determination of trace nickel in water samples.     

Sol–gel derived organic–inorganic hybrid materials: synthesis,characterizations and applications

Organic/inorganic hybrid materials prepared by the sol–gel approach have rapidly become a fascinating new field of research in materials science. The explosion of activity in this area in the past decade has made tremendous progress in both the fundamental understanding of the sol–gel process and the development and applications of new organic/inorganic hybrid materials. Polymer-inorganic nanocomposite present an interesting approach to improve the separation properties of polymer material because they possess properties of both organic and inorganic such as good permeability, selectivity, mechanical strength, and thermal and chemical stability. Composite material derived by combining the sol–gel approach and organic polymers synthesis of hybrid material were the focus area of review It has also been demonstrated in this review that a more complete understanding of their structure–property behavior can be gained by employing many of the standard tools that are utilized for developing similar structure–property relationships of organic polymers. This review article is introductory in nature and gives introduction to composite materials/nanocomposite, their applications and the methods commonly employed for their synthesis and characterization. A brief literature survey on the polysaccharide templated and polysaccharide/protein dual templated synthesis of silica composite materials is also presented in this review article.     

Preparation of bioactive microspheres of organic modified calcium silicates through sol–gel processing

Bioactive ceramics show specific biological activity, a bone-bonding ability, and are used as bone-repairing materials. Particles of bioactive ceramics may be used as fillers for fabricating bioactive composites where bioactive fillers are dispersed in a polymer matrix. Chemical bonding between the filler and the organic matrix requires an effective organic modification of the bioactive filler. Previous studies have reported that inorganic glasses in the CaO–SiO₂ system act as fundamental components showing bioactivity, as they show a high potential to form bone-like apatite after exposure to a body fluid. Therefore, organically modified microspheres composed of CaO–SiO₂ gels can be useful as bioactive fillers to produce bioactive composites. In this study, the conditions for the preparation of organically modified gels composed of CaO–SiO₂ were investigated using sol–gel processing of tetraethoxysilane, calcium nitrate tetrahydrate and silane coupling agents (SCAs), such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane (GPS), along with polyethyleneglycol (PEG). Spherical particles with diameter of 2–3 μm were obtained when adding the SCAs, except for GPS with PEG. Incorporation of the SCAs was confirmed using Fourier transform infrared spectroscopy. All the samples prepared with the SCAs formed bone-like apatite on their surfaces in a simulated body fluid within a period of 1 day. These results indicate that bioactive microspheres of organically modified CaO–SiO₂ gels can be obtained using sol–gel processing with SCAs.     

Preparation and characterization of anticorrosion Ormosil sol–gel coatings for aluminum alloy

Organically modified silicate (Ormosil) coatings have been synthesized through the sol–gel method for corrosion protection of aluminum alloy. Silica-based unmodified coatings were also designed to investigate the effect of tetraethoxysilane (TEOS) content on the properties of the coatings. The surface morphology of the coatings was characterized by scanning electron microscopy. The corrosion resistance was evaluated by immersion test, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. In addition, the surface potential differences of the coated samples were determined by scanning Kelvin probe. The results showed that a better corrosion resistance of unmodified coating was prepared by controlling the TEOS/EtOH/H₂O molar ratio of 0.109/1/1.52. Ormosil coatings provided excellent barrier properties and corrosion resistance in comparison with the unmodified sol–gel coatings. The Ormosil coating modified with triethoxyoctylsilane exhibited corrosion resistance properties superior to the other Ormosil coatings after exposure to 3.5 wt% NaCl solution for 10 days.     

Preparation and characterization of boron-based bioglass by sol−gel process

45S5 bioglass has been widely studied in the last few decades because of its bioactivity and promising applications in the biomedical field. Boron, even few studied, represents a potential element to improve the properties of the 45S5 bioglass derivatives. The bioglasses are conventionally prepared by heat treatment of oxides and silicon. Here, the sol?gel method is proposed for the preparation of the boron-based 45S5 bioglass (45S5B) and the classical 45S5 bioglass (45S5), using water-soluble salts as raw materials. The bioglasses were characterized by FTIR, XRD, and SEM, indicating the success of the sol?gel method for preparation of the samples. The bioglasses were also tested in vitro for bioactivity in biological conditions and cytotoxicity against eukaryotic cells. The bioactivity of 45S5B was similar to the bioactivity of 45S5 bioglass, indicated by the deposition of hydroxyapatite crystals at the surface of the pristine bioglasses. The results of cytotoxicity tests revealed that the IC₅₀ of 45S5B (IC₅₀?=?7.56?mg?mL^?1) was similar to the IC₅₀ of 45S5 (IC₅₀?=?8.15?mg?mL^?1), indicating its safety for application in the biomedical field.

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