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Materials Chemistry and Physics 133 (2012) 278– 283

Contents lists available at SciVerse ScienceDirect

Materials Chemistry and Physics

jo u rn al hom epage : www.elsev ier .com/ locate /matchemphys

reparation of DNA–cyclodextrin–silica composite by sol–gel method and itstilization as an environmental material

asanori Yamada ∗, Emiko Nakayamaepartment of Chemistry, Faculty of Science, Okayama University of Science, Ridaicho, Kita-Ku, Okayama 700-0005, Japan

r t i c l e i n f o

rticle history:eceived 11 May 2011eceived in revised form8 November 2011ccepted 9 January 2012

eywords:

a b s t r a c t

A DNA–cyclodextrin–silica composite was prepared by the sol–gel method. This composite possessedthe bi-functions of double-stranded DNA, such as intercalation into DNA, and cyclodextrin, such asinclusion into its intramolecular cavity. Therefore, we demonstrated the accumulation of harmful com-pounds from an aqueous multi-component solution using a DNA–cyclodextrin–silica composite column.As a result, the DNA–cyclodextrin–silica composite column can effectively accumulate not only planarstructure-containing harmful compounds, such as dioxin and polychlorobiphenyl (PCB) derivatives, but

iomaterialolymersomposite materialrganic compoundsol–gel growth

also non-planar structure containing compounds, such as bisphenol A and diethylstilbestrol, from anaqueous multi-component solution. The accumulated amount of these harmful compounds was morethan 90%. Additionally, the DNA–cyclodextrin–silica composite column was recycled by the applicationof methanol. Therefore, the DNA–cyclodextrin–silica composite may have the potential to be used asan environmental material for the accumulation of harmful compounds from industrial or experimentalwaste.

. Introduction

Double-stranded DNA, one of the genetic materials, can beurified from either salmon milts or shellfish gonads, whichre discarded as waste around the world. In addition, DNAas various functions, such as the selective binding of harmfulompounds, the interaction with heavy metal ions, biodegra-ation, etc [1,2]. Therefore, DNA has attracted attention as aunctional material [3,4]. We reported the utilization of theNA as an environmental material, which can selectively accu-ulate planar structure-containing harmful compounds, such

s dioxin-derivatives, polychlorobiphenyl (PCB)-derivatives, andenzo[a]pyrene [5,6]. However, since this accumulative mecha-ism is due to the intercalation into the double-stranded DNA,NA could not accumulate non-planar structure-containing com-ounds, such as bisphenol A and diethylstilbestrol. Therefore,e recently prepared a DNA–cyclodextrin composite material

y mixing DNA and ˇ-cyclodextrin (CD) [7,8], which is a cyclicligosaccharide composed of seven d-glucopyranose residues9–11]. This DNA–CD composite material can accumulate various

armful compounds, such as dioxin, PCB, and bisphenol A, by inter-alation into DNA and inclusion into the CD’s cavity. However, sincehis material, entirely consisting of organic compounds, does not

∗ Corresponding author. Tel.: +81 86 256 9550; fax: +81 86 256 9757.E-mail address: myamada@chem.ous.ac.jp (M. Yamada).

254-0584/$ – see front matter © 2012 Elsevier B.V. All rights reserved.oi:10.1016/j.matchemphys.2012.01.022

© 2012 Elsevier B.V. All rights reserved.

have the required physical property, it is difficult to use it as anenvironmental material under practical conditions.

Most recently, we prepared a DNA–CD-inorganic compositematerial by mixing with silane coupling agents [12]. This DNA-inorganic composite material did possess the required physicalproperty, such as tensile strength. However, since the formationsof this composite material were a film or gel, the surface area ofthe composite materials was low. Furthermore, this material is aflexible material and not a solid material. Therefore, the DNA–CD-inorganic composite material could not used as the DNA column,which is the effective method to accumulate the harmful com-pounds. In this study, we focused on the DNA–silica compositematerial. The DNA–silica composite, which was prepared by mix-ing the DNA and tetraethoxysilane (TEOS), has been reported andthis composite has a high surface area [13–15]. Additionally, thiscomposite could accumulate carcinogenic compounds, such asethidium bromide, by intercalation [14]. However, the function asan absorbent for various harmful compounds, such as endocrinedisruptors, has not been reported. Furthermore, the DNA–silicacomposite with the inclusion function of CD has not yet beenreported to the best of our knowledge. Therefore, the compositematerial with the bi-functions of DNA and CD is interesting fordevelopment in the material science field.

In this study, we prepared the DNA–CD–silica composite bythe sol–gel method. This composite possessed the bi-functionsof double-stranded DNA, such as intercalation, and CD, suchas inclusion. Therefore, we demonstrated the accumulation of

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M. Yamada, E. Nakayama / Materials

armful compounds from an aqueous multi-component solutionsing a DNA–CD–silica composite column. As a result, the compos-

te column can accumulate not only the planar structure-containingarmful compounds, such as dioxin and PCB derivatives, but alsohe non-planar structure containing compounds, such as bisphe-ol A and diethylstilbestrol, from an aqueous multi-componentolution. Additionally, the DNA–CD–silica composite column wasecycled using methanol. Therefore, the DNA–CD–silica compos-te might have the potential to be used as an environmental

aterial.

. Experimental

.1. Materials

Double-stranded DNA (sodium salt from salmon milt, molec-lar weight; >5 × 106) was obtained from Biochem Ltd., Kawagoe,

apan. ˇ-Cyclodextrin (CD), 3-aminopropyltriethoxysilane (APTES),etraethoxysilane (TEOS), toluene-p-sulfonyl chloride, ethidiumromide, 1-anilinonaphthalene-8-sulfonate (1,8-ANS), dibenzofu-an (DF), biphenyl (Bip), naphthalene (NP), bisphenol A (Bis-A), andiethylstilbestrol (DES) were purchased from Wako Pure Chemi-al Industries, Ltd., Osaka, Japan, Nacalai Tesque, Inc., Kyoto, Japan,cros Organics, Morris Plains, NJ, or Tokyo Kasei Industries Ltd.,okyo, Japan. The molecular structures of silane coupling reagentsPTES and TEOS are shown in Fig. 1. Additionally, the moleculartructures of model endocrine disruptors and harmful compoundsre shown in Fig. 1.

.2. Synthesis of monotosylated ˇ-CD

The monotosylation of ˇ-CD at the 6-position was synthe-ized by a reported procedure [7,16,17]. The monotosylated ˇ-CDCDOTs) were formed by reaction of ˇ-CD (25 g, 22 mmol) witholuene-p-sulfonyl chloride (12.5 g, 66 mmol) in pyridine (100 ml)t 0 ◦C for 2 h. The resulting CDOTs were purified by recrystalliza-ion from water and a butanol–ethanol–water (5:4:3, v/v/v) mixedolvent. The identification of CDOTs was confirmed by the thin-ayer chromatography (TLC). Rf = 0.46 (butanol–ethanol–water).

.3. Synthesis of DNA–CD–silica composite

Scheme 1 shows the synthetic scheme of DNA–CD–silica com-osite. The precursor solution A (PS-A) was prepared by thecid-hydrolysis of TEOS [14]. TEOS, distilled water, and hydrochlo-ic acid were mixed at 1:5:1 × 10−4 molar ratio. The mixed solutionas stirred at room temperature for 3 h. This precursor solution wassed throughout this experiment. The precursor solution B (PS-) was prepared by the heating of 3-aminopropyltriethoxysilaneAPTES). The APTES (6 wt%) was mixed with ethanol in flask. Addi-ionally, the CDOTs was added into flask at APTES: CDOTs = 1:0.5molar ratio). This mixture was reacted at 80 ◦C for 72 h and cooledt room temperature.

The DNA–CD–silica composite was synthesized by the follow-ng procedures. The double-stranded DNA was dissolved in 0.2 Mcetate buffer solution (pH 4). The concentration of DNA was

mg ml−1. PS-A (6 ml), PS-B (3 ml), and DNA solution (6 ml) wasixed in flask. This mixture was reacted at 60 ◦C for 72 h. The

btained gel was repeatedly washed with distilled water andethanol to remove the salts, ethanol, and unreacted components.

his gel was dried by the freeze-dryer for 48 h. DNA–CD–silica com-osite was obtained as a white powder. On the other hand, normal

ilica gel without DNA and CD was synthesized from the TEOS solu-ion.

The amount of encapsulated DNA was determined by the fol-owing procedure [5,6]: DNA–CD–silica composite (50 mg) were

stry and Physics 133 (2012) 278– 283 279

hydrolyzed with 1 M HCl (5 ml) at 100 ◦C for 1 h, and then theamount of DNA in the aqueous solution was determined from theabsorbance at 260 nm.

2.4. IR spectra of DNA–CD–silica composite

In infrared (IR) measurements, we prepared the IR sampleswithout the mixing of TEOS. The IR absorption spectra of thesematerials were measured by the attenuated total reflection (ATR)method using a FT-IR 8400 Fourier transform infrared spectrome-ter (Shimadzu Corp., Kyoto, Japan). The IR spectrum was measuredwith a resolution of 4 cm−1.

2.5. Characterization of DNA–CD–silica composite

The thermal stability of the DNA–CD–silica composite wasanalyzed by thermogravimetric–differential thermal analysis(TG–DTA) (DTG-60, Shimadzu Corp., Kyoto, Japan). The TG–DTAmeasurement was carried out at a heating rate of 10 ◦C min−1 inthe range from room temperature to 300 ◦C under a dry-nitrogenflow. Sample weights of TG–DTA measurements were normalizedat 1 mg. Pure DNA and CD was used for a control.

2.6. Accumulation of harmful compounds from multi-componentsolution by DNA–CD–silica composite column

DNA–CD–silica composite (100 mg) were packed in a Pasteurpipett (� 5 mm, Iwaki Glass Co., Ltd., Tokyo, Japan). The length ofthe mobile phase in DNA–CD–silica composite column was 30 mm.The DNA–silica composite column without the CD molecule andnormal silica column without DNA and CD molecules were similarlyprepared.

The harmful multi-component solution, which contained Bis-A,DES, NP, Bip, and DF, was prepared by mixing of the aque-ous solutions. The concentrations of Bis-A, DES, NP, Bip, and DFin the multiple component solution were 5.3 × 10−2, 5.6 × 10−3,7.0 × 10−2, 3.3 × 10−2, and 1.2 × 10−2 �M, respectively. The accu-mulation of harmful compounds by a DNA–CD–silica compositecolumn was examined by the following procedures. The aque-ous solution (5 ml) of harmful compounds was applied intothe DNA–CD–silica composite column. The flow rate of theDNA–CD–silica composite column was 0.1 ml min−1. The accu-mulated amounts of these compounds were determined by theabsorbance of the eluted solution and the starting solution.This solution was analyzed by reverse-phase high performanceliquid chromatography (HPLC) using an Inertsil® ODS-P col-umn (7.6 mm × 250 mm, GL Science Inc., Tokyo, Japan) with aCH3OH/water (80:20, v/v). The detections (276 nm) of the harmfulcompounds used a UV-8010 UV–vis detector (Tosoh Coop., Tokyo,Japan). Additionally, the DNA–silica column without the CD andthe normal silica column without the DNA and CD were used fora control. In contrast, the reuse of DNA–CD–silica column wasdemonstrated by the applying of methanol solution (10 ml).

3. Results and discussion

3.1. Preparation of DNA–CD–silica composite

The DNA–CD–silica composite was prepared by the sol–gelmethod. Fig. 2(a) shows a photograph of DNA–CD–silica compos-ite. The dried DNA–CD–silica composite was obtained as a whitepowder. The amount of encapsulated DNA in the DNA–CD–silica

composite was hydrolyzed by 1 M HCl and quantified by absorbanceat 260 nm. The amount of the encapsulated DNA in the silicacomposite was 16 mg g−1 of the DNA–CD–silica composite. Thewater-stability of DNA–CD–silica composite was evaluated by the

280 M. Yamada, E. Nakayama / Materials Chemistry and Physics 133 (2012) 278– 283

O

dibenzofuran(DF)

biphenyl(Bip)

HO

OHOHHO

bisphenol A(Bis-A)

diethylstilbestrol(DES)

naphthalene(NP)

tetraethoxysilane(TEOS)

3-aminopropyltriethoxysilane(APTES)

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ig. 1. Molecular structures of tetraethoxysilane (TEOS), 3-aminopropyltriethoxysDES), and naphthalene (NP).

luted DNA from the composite material in water. Although theNA–CD–silica composite was incubated in aqueous solution forore than 24 h, the eluted DNA was not detected by the absorbance

t 260 nm (data not shown). This is due to the encapsulation ofNA into the siloxane network of TEOS molecule and these water-

tabilities have been reported at DNA–silica composite [14].Next, we examined the properties of the double-stranded DNA

nd CD in the DNA–CD–silica composite material. Fig. 2(b) and (c)hows the fluorescence images of the DNA–CD–silica compositen the aqueous ethidium bromide and 1-anilinonaphthalene-8-ulfonate (1,8-ANS) solutions, respectively. The ethidium bromideolecules intercalate into the double-stranded DNA and pro-

uce a strong fluorescence under UV irradiation [1,2]. In fact, theNA–CD–silica composite, which was incubated in an aqueousthidium bromide solution for 1 day, showed a red fluorescencender UV irradiation (see Fig. 2(b)). These results suggested thathe DNA in the DNA–CD–silica composite maintained the double-tranded structure and the DNA functions as an intercalation. The,8-ANS molecules are included into the intramolecular cavity ofhe CD and indicate the fluorescence under UV irradiation [17].he DNA–CD–silica composite, which was incubated in an aqueous,8-ANS solution for 1day, showed a blue fluorescence under UV

rradiation (see Fig. 2(c)). Therefore, the DNA–CD–silica compositeossesses the function of inclusion of a molecule into the CD cavity.hese results suggested that the DNA–CD–silica composite have theunctions of both the double-stranded DNA and CD. Furthermore,

(APTES), dibenzofuran (DF), biphenyl (Bip), bisphenol A (Bis-A), diethylstilbestrol

these DNA–CD–silica composite with staining by ethidium bromideor 1,8-ANS did not show the release of these molecules in spite ofa long incubation.

3.2. Molecular structure of DNA–CD–silica composite

The molecular structures of the DNA–CD–silica compositewere confirmed by IR spectrometry using an ATR prism. TheDNA–CD silica composite with mixing of TEOS showed a strongabsorbance which was attributed to the siloxane network whilethe absorption bands of the DNA, CD, and APTES moleculeswere too weak to obtain the molecular structure. Therefore,we prepared the IR samples without the mixing of the TEOSmolecule.

Fig. 3 shows the IR spectra of (a) pure hydrolyzed APTES; (b) pureDNA; (c) pure CD; (d) APTES–DNA composite without TEOS, and (e)dried-precursor solution B (PS-B). When the APTES molecules weremixed with the DNA, the absorption band at 1591 cm−1, attributedto the antisymmetric vibration of the NH3

+ in the APTES molecule[18,19], was shifted ca. 30 cm−1 to a lower frequency (see thedashed line in Fig. 3(a) and (d)). Similar results, such as the shift to alower frequency, have been reported for the DNA-poly(allylamine)

composite material with an electrostatic interaction [7,12]. Addi-tionally, the absorption band at 1226 cm−1 in the pure DNA, relatedto the antisymmetric vibration of the phosphate group [7,12,18],was shifted ca. 10 cm−1 to a lower frequency by the mixing of

M. Yamada, E. Nakayama / Materials Chemistry and Physics 133 (2012) 278– 283 281

(a) Precursor solution A (PS-A)

(b) Precursor solution B (PS-B)

TEOS : H2O : HC l = 1 : 5 : 1 × 10-4 (molar ratio )

Stirr ing at RT for 3 h

PS-A

APTES : CDOT s = 1 : 0.5 (molar ratio)

Stirr ing at 80 °C for 72 h

PS-B

(c) DNA-CD-silica compositePS-BPS-A DNA solution

Stirr ing at 60 °C for 72 h

DNA-CD-Si lica composite (suspended solution )

Washed with water and methanolFreeze-drying

DNA-CD-Si lica composite (powder)

Scheme 1. Synthetic scheme of DNA–CD–silica. (a) Precursor solution A (PS-A). (b) Precursor solution B (PS-B). (c) DNA–CD–silica composite.

Fig. 2. Photograph of DNA–CD–silica composite. (a) Dried DNA–CD–silica compositewithout staining. (b) Fluorescence image of DNA–CD–silica composite with stainingof ethidium bromide under UV irradiation of 312 nm. (c) Fluorescence image ofDNA–CD–silica composite with staining of 1,8-ANS under UV irradiation of 312 nm.

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Fig. 3. IR spectra of DNA–CD–silica composite. (a) Pure hydrolyzed APTES; (b) pure

DNA; (c) pure CD; (d), DNA-APTES composite, and (e) dried-precursor solution B(PS-B). The IR spectrum was measured with a resolution of 4 cm−1. Triplicate exper-iments gave similar results.

APTES (see the dashed line in Fig. 3(b) and (d)). This shift to a lowerfrequency is due to the electrostatic interaction between the phos-phate group and positively charged molecule [7,12]. These results

suggested that the phosphate group of DNA binds to the NH3

+

group of APTES by an electrostatic interaction in the DNA–CD–silicacomposite. On the other hand, the dried-PS-B (APTES–CD com-posite without mixing of TEOS) showed an absorption band at

282 M. Yamada, E. Nakayama / Materials Chemistry and Physics 133 (2012) 278– 283

Fig. 4. TG (a) and DTA (b) curves of DNA–CD–silica composite with the heating rateo ◦ −1 ◦

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Fig. 5. Accumulated amount of various harmful compounds by the silica gel (openbar), DNA–silica composite (diagonal bar), and DNA–CD–silica composite columns(solid bar). This aqueous multi-component solution, which contained Bis-A, DES,

f 10 C min in the range from room temperature to 300 C under dry nitrogen.1) Pure CD material; (2) pure DNA material; and (3) DNA–CD–silica composite.riplicate experiments gave similar results.

120 cm−1, attributed to the stretching vibration of C-N in the sec-ndary amine [18] (see dashed line Fig. 3(e)). This result suggestedhat the CDOTs molecule reacts with the amino group of the APTES

olecule and form a covalent bond between the CD and APTESolecules in the DNA–CD–silica composite. Therefore, the APTESolecules play a role in the encapsulation and immobilization ofNA and CD in the DNA–CD–silica composite, respectively.

.3. Characterization of DNA–CD–silica composite

Fig. 4(a) and (b) shows the thermogravimetric (TG) and differ-ntial thermal analyses (DTA) of (1) pure CD material, (2) pure DNAaterial, and (3) DNA–CD–silica composite. The TG–DTA measure-ent was carried out at a heating rate of 10 ◦C min−1 in the range

rom room temperature to 300 ◦C under a dry-nitrogen flow. Theure CD material and pure DNA material showed the TG weight lossf 10–15% below 200 ◦C (lines (1) and (2) in Fig. 4(a)). This TG weightoss is due to the evaporation of water from these materials. Addi-ionally, the high TG weight loss of the pure CD and DNA materialsbove 250 ◦C is attributed to pyrolysis or decomposition. Similaresults have been reported for various DNA materials [20,21]. Inontrast, the DNA–CD–silica composite showed the TG weight lossf approximately 10% below 150 ◦C, related to the evaporation ofater from the composite (line (3) in Fig. 4(a)). The DTA analysis

f the DNA–CD–silica composite showed an endothermic peak at82.6 ◦C. This endothermic peak was due to pyrolysis or decom-osition of the organic components in the composite. In fact, theNA–CD–silica composite showed a high TG weight loss above00 ◦C. Therefore, these results suggest that the DNA–CD–silicaomposite can be used for materials below 150 ◦C.

.4. Accumulation of harmful compounds by the DNA–CD–silicaomposite column

We demonstrated the accumulation of harmful compoundsy the DNA–CD–silica composite column. In this experiment, wesed a harmful multi-component solution, which contained Bis-, DES, NP, Bip, and DF. The concentrations of Bis-A, DES, NP,

NP, Bip, and DF, was analyzed by HPLC. The accumulated amount was determinedby the absorbance (276 nm) of the eluted solution and the starting solution. Each ofthe values represents the mean of three separate determinations.

Bip, and DF in the multiple component solution were 5.3 × 10−2,5.6 × 10−3, 7.0 × 10−2, 3.3 × 10−2, and 1.2 × 10−2 �M, respectively.This aqueous solution was applied to the DNA–CD–silica column.This aqueous solution was analyzed by reverse phase HPLC. Theaccumulated amount of harmful compounds was determined bythe absorbance of the eluted solution from the DNA–CD–silicacolumn and the starting solution. Fig. 5 shows the accumulatedamount of various harmful compounds by the normal silica gelcolumn without DNA and CD molecule (open bar), DNA–silica col-umn (diagonal bar) without the CD molecule, and DNA–CD–silicacolumn (solid bar). The normal silica gel column without DNAand CD accumulated the DES, NP, Bip, and DF. These accumulatedamounts were 40–55%. These accumulations are due to the absorp-tion onto the silica gel with the high surface area. In contrast, theBis-A molecules, which shows the highest solubility in these fivemolecules, was not accumulated by the normal silica gel column.Therefore, we evaluated the accumulation of harmful compoundsby the DNA–silica column. The DNA–silica column without theCD molecules accumulated the DES, NP, Bip, and DF (see diagonalbar in Fig. 5). These accumulated amounts of harmful compoundsby the DNA–silica column were higher than that by normal sil-ica gel column. Especially, the accumulated amounts of Bip andDF showed a high value, and these values were 80–95%. Gener-ally, Bip and DF are planar structure-containing molecules and arethe compounds intercalated into the double-stranded DNA [22,23].Therefore, these compounds were accumulated by the interca-lation into the double-stranded DNA of the DNA–silica column.In contrast, since Bis-A does not have a planar structure, Bis-Acould not intercalate into the double-stranded DNA. As a result,the DNA–silica column did not show the accumulation of Bis-A. Asimilar result was obtained for DES without the planar structure.The accumulated amount of DES by the DNA–silica column wasapproximately 50% and this value was same as that of normal sil-ica gel column. Therefore, we demonstrated the accumulation ofBis-A or DES by the DNA–CD–silica column. Surprisingly, theDNA–CD–silica column could accumulate the Bis-A or DES with-out the planar structure. Additionally, the accumulated amounts ofBis-A and DES were 90% and 98%, respectively. The increase in theaccumulated amount is due to the inclusion of Bis-A or DES into theintramolecular CD’s cavity. Similar results, such as the inclusion of

Bis-A or DES into the CD’s cavity, have been reported for the CD-immobilized polymers [7,12] and it is known to that these harmfulcompounds, such as Bis-A, form the encapsulated compounds at the1:2 (= Bis-A:CD molecule) [24]. Furthermore, the DNA–CD–silica

M. Yamada, E. Nakayama / Materials Chemi

Fig. 6. Reuse of the DNA–CD–silica composite column. The aqueous multi-component solution was applied to the DNA–CD–silica column. Used DNA–CD–silicacr

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olumn was recycled by the washing with a methanol solution. Each of the valuesepresents the mean of three separate determinations.

olumn indicated the high accumulated amount of >90% for NP,ip, and DF. The increase in the accumulated amount is also dueo the inclusion of these harmful compounds into the CD’s cavity.n the other hand, we demonstrated the accumulation of harmfulompounds at the higher concentration. The concentrations of Bis-, DES, NP, Bip, and DF in the multiple component solution were.9 �M, 2.0 �M, 2.9 �M, 23 �M, and 1.9 �M, respectively. This accu-ulation amount of harmful compounds by the DNA–CD–silica

olumn did not show the decrease (data not shown). Therefore,n our experimental condition, DNA–CD–silica column can use ateast in the concentration range of 1.2 × 10−2 to 23 �M.

Since the DES without a planar structure is a non-intercalativeompound, it could not interact with the double-stranded DNA byhe intercalation. Additionally, the aromatic ring of NP with the pla-ar structure is too small to intercalate into the double-strandedNA. Therefore, NP cannot interact with the double-stranded DNA.imilar results have been reported for the UV-irradiated DNAiomatrix [7,12,24]. However, the DNA–silica column without CDolecules indicated the accumulated amounts of 50% and 70% forES and NP, respectively (see diagonal bar in Fig. 5). This phe-omenon is due to the adsorption of these compounds onto theilica surface. In fact, the silica column without the DNA and CDhows the accumulation of DES and NP (see open bar in Fig. 5).

.5. Reusability of DNA–CD–silica composite column

Finally, we demonstrated the reuse of the DNA–CD–silicaomposite column. When the methanol solution was applied tohe harmful compounds-accumulated DNA–CD–silica column, thearmful compounds were released into the methanol solution fromhe DNA–CD–silica composite (data not shown). These releases ofhe harmful compounds to the organic solvent have been reported25], and this is due to the extraction by the organic solvent.fter the application of the methanol solution, an aqueous multi-

ompound solution, which contained Bis-A, DES, NP, Bip, andF, was reapplied to the DNA–CD–silica composite column. Thisycling was repeated three times. Fig. 6 shows the accumulatedmount of the harmful compounds versus the number of cycles.

[

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stry and Physics 133 (2012) 278– 283 283

Although the DNA–CD–silica composite column was recycled threetimes by application of the methanol solution, the accumulatedamount was maintained at more than 90% and did not appearto be decreasing. These results suggested that the DNA–CD–silicacomposite column could be recycled by washing with an organicsolvent, such as methanol.

4. Conclusion

We prepared a DNA–cyclodextrin (CD)–silica composite by mix-ing DNA, CD, and tetraethoxysilane (TEOS). This DNA–CD–silicacomposite possessed the properties of both the double-strandedDNA and CD. Additionally, the DNA–CD–silica composite couldeffectively accumulate various harmful compounds, such as dioxin,PCB, and bisphenol A, from an aqueous multi-component solution.The accumulated amount of these harmful compounds was greaterthan 90%. Additionally, the DNA–CD–silica composite column couldbe recycled by the application of methanol, and the accumulatedamount of harmful compounds did not appear to be decreasing.Therefore, the DNA–CD–silica composite may have the potential tobe used as an environmental material, such as for the accumulationof harmful compounds from factory or experimental waste.

Acknowledgments

This work was supported by matching fund subsidy for privateuniversities from MEXT (Ministry of Education, Culture, Sports, Sci-ence and Technology of Japan). Additionally, the part of this workwas supported by Wesco Scientific Promotion Foundation.

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