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Download Author Version (PDF) Polymer Chemistry Accepted Manuscript This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/polymers Please do not adjust margins Page 1 of 6 Polymer Chemistry Journal Name ARTICLE Synthesis of Electroconductive Hydrogel Films by Electro- controlled Click Reaction and its Application to Drug Delivery eceived 00th January 20xx, System† Accepted 00th January 20xx Eun Jung Choi,a, Jisoo Shin, b, Zinah Hilal Khaleel, a, Inhwan Cha, a, Sang-Ho Yun, c, Seung-Woo DOI: 10.1039/x0xx00000x Cho, *b , and Changsik Song *a www.rsc.org/ Electroconductive hydrogels are composed of 3-dimensionally structured hydrogels and conducting molecules with electrical, optical, and reversible redox properties. This hybrid material can be utilized as electrically-stimulated biomaterials in implantable biosensors or drug delivery systems. In this study, carbon nanotube-incorporated polyvinyl alcohol (PVA)-based hydrogels were synthesized by an electro-click reaction, which was controlled by an electrochemically Manuscript generated Cu(I) catalyst. When the reduction potential of Cu(II) ions was applied, PVA-based hydrogels were deposited onto indium-tin-oxide-coated glass electrodes via Cu(I)-catalysed alkyne–azide cycloaddition (click reaction). When the hydrogels contained carbon nanotubes, thicker films were deposited because the embedded carbon nanotubes provided a larger electrochemical active area. In addition, the carbon nanotubes improved the electrical conductivity of the hydrogel systems. We investigated the electro-stimulated drug release behaviour with electro-click conductive hydrogels using tetracycline as a model drug. several drug delivery methods such as oral dosing and 1. Introduction transdermal drug delivery. Oral dosing is the simplest method, Electroconductive hydrogels are conducting polymeric but it has disadvantages such as poor absorption. Transdermal Accepted networks composed of hydrogels and inherently conductive drug delivery is an alternative that introduce drug molecules polymers. 1 These composites have a combination of their through the skin into the blood stream. It is attractive because it 6 components` properties, which are hydrogels’ softness, high is safe and easy to apply, but one of its disadvantages is that 7 degree of hydration, high diffusivity of small molecules and high molecular drugs have low permeability. Iontophoresis is a biocompatibility and the conducting polymers’ electrical method used to transfer drugs or proteins in patches into our 8 conductivity, optical switching, and reversible redox properties. bodies through the skin using an applied electric field. Pillai et Furthermore, their chemical and mechanical properties can be al. showed that insulin delivery through the skin was influenced 9 tuned easily such as changing the crosslinking density. 2, 3 These by electronic parameters. The charge applied during hybrid systems can be fabricated into specific forms on various iontophoresis affected the electrochemical stability of insulin substrates according to the intended purposes. and the current strength also affected the permeation of insulin. Electroconductive hydrogels have been applied to biomaterials Electroconductive hydrogels can be a good option for electro- 10 Chemistry with electrical stimuli such as those used in biosensors, 4 or stimulated drug delivery because they have faster response tissue engineering. 5 due to their improved electrical properties. Pillay et al. reported Drug delivery is the process of transferring a drug into the body ON-OFF drug release kinetics using polyaniline-incorporated 11 over a period of time and at a specific rate, with the desired poly(vinyl alcohol)-based hydrogel via electrical stimulus. drug concentration maintained for effective therapy. There are When the amount of polyaniline increased, the conductivity of polyaniline-poly(vinyl alcohol) hydrogel increased linearly. The erosion rate of the hydrogel also increased due to electro- a Department of Chemistry, Sungkyunkwan University, Suwon, Gyeonggi 440-746, actuation, leading to erosion. Torresi et al. reported the Republic of Korea. E-mail: [email protected] bDepartment of Biotechnology, Yonsei University, Seoul, 120-749, Republic of controlled release of safranin from semi-interpenetrating 12 Polymer Korea. E-mail: [email protected] polyaniline-polyacrylamide networks. The polyaniline grew cDepartment of Mechanical Engineering, Inha University, Incheon, 402-751, inside the pores of swellable polyacrylamide hydrogel. The Republic of Korea . †Electronic Supplementary Information (ESI) available: SEM image of ITO-coated change in the oxidation state of the polyaniline expanded and glass after gelation reaction without bis-azide crosslinker (Fig S1); Cyclic contracted the hydrogel, indicating that the safranin storage in voltammogram of CNT/PVA click solution (Fig S2); Cyclic voltammogram of the hydrogel was liberated by electric stimuli. 3- Fe(CN) 6 with different scan rates (Fig S3); UV-vis spectra of tetracycline (Fig S4); The release profile of tetracycline from PVA hydrogel film without CNTs (Fig S5). See DOI: 10.1039/x0xx00000x This journal is © The Royal Society of Chemistry 20xx J. Name ., 2013, 00 , 1-3 | 1 Please do not adjust margins Please do not adjust margins Polymer Chemistry Page 2 of 6 COMMUNICATION Journal Name (a) roughly estimated to be 1/20 out of repeat units of PVA, which = was proven by 1H-NMR spectra(more detailed information in the reference 15). Multi-walled carbon nanotubes (CNTs) were = purchased from Sigma-Aldrich, and tetracycline hydrochloride was purchased from TCI. (b) 2.2 Instrumentation (-) - Cyclic voltammetry were performed on a CHI electrochemical analyser in a three-electrode cell configuration consisting of an Drug - - Ag/AgCl reference electrode, a Pt coil as a counter-electrode loading - and an indium tin oxide (ITO)-coated glass, fluoride tin oxide (FTO)-coated glass. 0.1 M solution of potassium chloride in water was used as a supporting electrolyte. Scanning electron Fig 1. (a) In the presence of Cu(I) generated by an electric potential, CNT-wrapping microscope images were obtained by using FE-SEM JEOL- 13-16 alkyne-functionalized PVA chains are crosslinked with bis-azdie via Cu(I) catalyzed 7100. Hydrogel thickness were obtained by using surface alkyne–azide cycloaddition. (b) Schematic illustration of electroconductive hydrogel films synthesized by electrically controlled click reaction. CNT-embedded hydrogel profiler. films were synthesized onto the electrode at the reduction potential of Cu(II). These Electrochemical impedance spectra of hydrogels were hydrogel films can be used in electro-stimulated drug delivery system. measured using the potentiostat (CompactStat, Ivium Tech.). EIS measurements were performed with an amplitude of 10 mV Herein, carbon nanotube (CNT)-incorporated polyvinyl alcohol and the frequency from 0.1 Hz to 2000000 Hz at open-circuit Manuscript (PVA)-based hydrogels were synthesized by an voltage. Swollen hydrogel films were placed between ITO- electrochemically controlled click reaction, specifically, Cu- coated glass electrodes with 1 mm Teflon spacer. catalysed alkyne–azide cycloaddition (Figure 1). Click reaction has many advantages, 17 such as high selectivity and high yields, 2.3 CNT dispersion in a-PVA (CNT/PVA) and thus this reaction has been widely used for polymer surface A solution of a-PVA was prepared from a-PVA powder (30 18 modification and film fabrication. In previous research, we mg) in 1 mL of 0.1 M KCl aqueous solution. CNT (~1 mg) was demonstrated that electroconductive hydrogels can be added to the solutions, and sonicated with a probe-tip sonicator synthesized via click chemistry using a Cu(I) catalyst generated (26 W) for 30 min. The mixture was centrifuged (13 000 rpm) 19 by a reducing agent (sodium L-ascorbate). In this study, we for 90 min, and then decants were collected. utilized an electrochemical strategy to generate Cu(I) from 20 Accepted Cu(II) in-situ instead of using a reductant. This “electro-click” 2.4 Synthesis of hydrogel film reaction has been exploited by several research groups in 30 mg/mL of a-PVA, 6 mM of bis-azide and 10 mM creating multifunctional polymer materials 21-26 since further CuSO •5H O in aqueous solution was prepared with 0.1 M KCl stabilization of the easily oxidized Cu(I) during film deposition 4 2 as supporting electrolyte. Firstly, the reduction potential of Cu is not necessary and spatial and temporal control of the reaction (II) was found by cyclic voltammetry using the ITO-coated is also possible. Using the
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