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Adsorption and in vitro release of ofloxacin from alkali-treated halloysite
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Abstracts / Journal of Controlled Release 172 (2013) e14–e97
Slow swelling is one of the reasons limiting the application of hydrogels as controlled drug delivery systems. Superporous hydrogels (SPHs), prepared by creating interconnected pores throughout the hydrogel matrix are swelling fast and may act as superabsorbents [1]. In this work, a novel superporous hydrogel based on the monomer N-isopropylacrylamide (NIPAm) and cross-linker N,N′methylenediacrylamide (MBA) was prepared by using yeast and glucose as vesicant. Baicalin, a flavonoid extracted from the dry root of Scutellaria baicalensis Georgi and commonly used as traditional antiinflammatory herbal medicine, served as a model drug in the SPHs. Baicalin has interesting pharmacological activities like anti-inflammatory activity, lowering blood pressure, remoting urination and anti-allergic properties and so on [2]. The chemical structure, internal morphology and pore structure of the synthesized SPHs were examined by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), respectively. The temperature-sensitivity and swelling degree were measured by weighing. The absorption of baicalin by SPHs was investigated by Ultraviolet/Visible Spectroscopy (UV/vis). The results show that a large amount of CO2 was produced by the fermentation of the yeast. With the increase of yeast content, the pore size of the SPHs increased from ~100 μm to ~2 mm, while the lower critical solution temperature was still kept at 32 °C. Compared with pure PNIPAm hydrogel, the swelling ratio of SPHs increased 5–10 times. The absorption of baicalin by SPHs firstly increased and then remained constant.
carrier for drug delivery. The loading of drugs including 5aminosalicylic acid, diltiazem HCl and nifedipine onto halloysite was investigated and encouraging results were obtained [2]. In recent years, the functionalization of halloysite by various methods such as acid activation, mechanical–chemical activation and intercalation has attracted considerable interest in order to improve the properties of halloysite and the related products [3]. However, little information is available concerning the effects of alkali treatment of halloysite on adsorption capacity and release of drugs although halloysite is a well-known promising vehicle for drug delivery. Herein, we systematically investigated the effects of alkali treatment on the physicochemical properties, structure and morphology of halloysite. Afterwards, the adsorption and in vitro release properties of the treated halloysite for ofloxacin (OFL) were evaluated. Results indicate that NaOH treatment has no influence on the crystalline and tubular structure of halloysite. In addition, the number of mesopores and macropores of alkali-treated halloysite increases evidently with increasing NaOH concentration (Fig. 1), which leads to a remarkable increase of adsorption capacity and adsorption rate for OFL. Moreover, NaOH treatment can prolong the release of the adsorbed OFL due to improved hydrogen bonding and cation exchange. Thus, NaOH activation is a simple and effective protocol to improve the adsorption and release of cationic molecules from halloysite.
Scheme 1. The process of baicalin absorption by SPH, baicalin release and the SEM images of the SPH.
Keywords: Superporous hydrogels, Yeast, N-isopropylacrylamide, Baicalin, Controlled drug delivery Acknowledgements Great thanks to the National Nature Science Foundation of China (21104058 & 50973084), and the grant from the Applied Basic Research and Advanced Technology Programs of Science and Technology Commission Foundation of Tianjin (12JCQNJC01400) for financial support References [1] R.A. Gemeinhart, H. Park, K. Park, Pore structure of superporous hydrogels, Polym. Adv. 11 (2000) 617–625. [2] H.Y. Mou, X.J. Wang, T. Lv, L. Xie, H.P. Xie, On-line dissolution determination of baicalin in solid dispersion based on near infrared spectroscopy and circulation dissolution system, Chemom. Intell. Lab. Syst. 105 (2011) 38–42.
doi:10.1016/j.jconrel.2013.08.143
Adsorption and in vitro release of ofloxacin from alkali-treated halloysite Qin Wang, Junping Zhang⁎, Aiqin Wang Center of Eco-material and Green Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China E-mail address: [email protected] (Q. Wang). Halloysite is an aluminosilicate mineral, chemically similar to kaolin and structurally like carbon nanotubes [1]. This special nanotubular structure and the good biocompatibility make halloysite a promising
Fig. 1. Pore size distribution of alkali-treated halloysite samples. 4.0 g of natural halloysite powder suspended in 40 mL of NaOH solution with various concentrations (0.5, 4 and 6 mol L− 1) was sonicated at 50 °C for 1 h, and then washed with distilled water for many times until neutrality and dried at 105 °C to constant weight.
Keywords: Halloysite, Alkali-treatment, Adsorption and release, Ofloxacin Acknowledgements The authors are thankful for the joint supports of the “National Youth Natural Science Foundation of China” (No. 51003112) and the “Special Research Fund of Scholarship of Dean of CAS”. References [1] E. Joussein, S. Petit, J. Churchman, B. Theng, D. Righi, B. Delvaux, Halloysite clay minerals: a review, Clay Miner. 40 (2005) 383–426. [2] Y.M. Lvov, D.G. Shchukin, H. Möhwald, R.R. Price, Halloysite clay nanotubes for controlled release of protective agents, ACS Nano 2 (2008) 814–820. [3] B.C. Du, D. Guo, M. Jia, Newly emerging applications of halloysite nanotubes: a review, Polym. Int. 59 (2010) 574–582.
doi:10.1016/j.jconrel.2013.08.144
Coordination-responsive selenium-containing polymer micelles for controlled drug release Wei Cao, Yang Li, Zhiwei Sun, Huaping Xu⁎ Department of Chemistry, Tsinghua University, Beijing 100084, China E-mail addresses: [email protected] (W. Cao), [email protected] (H. Xu).
Abstracts / Journal of Controlled Release 172 (2013) e14–e97
Slow swelling is one of the reasons limiting the application of hydrogels as controlled drug delivery systems. Superporous hydrogels (SPHs), prepared by creating interconnected pores throughout the hydrogel matrix are swelling fast and may act as superabsorbents [1]. In this work, a novel superporous hydrogel based on the monomer N-isopropylacrylamide (NIPAm) and cross-linker N,N′methylenediacrylamide (MBA) was prepared by using yeast and glucose as vesicant. Baicalin, a flavonoid extracted from the dry root of Scutellaria baicalensis Georgi and commonly used as traditional antiinflammatory herbal medicine, served as a model drug in the SPHs. Baicalin has interesting pharmacological activities like anti-inflammatory activity, lowering blood pressure, remoting urination and anti-allergic properties and so on [2]. The chemical structure, internal morphology and pore structure of the synthesized SPHs were examined by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), respectively. The temperature-sensitivity and swelling degree were measured by weighing. The absorption of baicalin by SPHs was investigated by Ultraviolet/Visible Spectroscopy (UV/vis). The results show that a large amount of CO2 was produced by the fermentation of the yeast. With the increase of yeast content, the pore size of the SPHs increased from ~100 μm to ~2 mm, while the lower critical solution temperature was still kept at 32 °C. Compared with pure PNIPAm hydrogel, the swelling ratio of SPHs increased 5–10 times. The absorption of baicalin by SPHs firstly increased and then remained constant.
carrier for drug delivery. The loading of drugs including 5aminosalicylic acid, diltiazem HCl and nifedipine onto halloysite was investigated and encouraging results were obtained [2]. In recent years, the functionalization of halloysite by various methods such as acid activation, mechanical–chemical activation and intercalation has attracted considerable interest in order to improve the properties of halloysite and the related products [3]. However, little information is available concerning the effects of alkali treatment of halloysite on adsorption capacity and release of drugs although halloysite is a well-known promising vehicle for drug delivery. Herein, we systematically investigated the effects of alkali treatment on the physicochemical properties, structure and morphology of halloysite. Afterwards, the adsorption and in vitro release properties of the treated halloysite for ofloxacin (OFL) were evaluated. Results indicate that NaOH treatment has no influence on the crystalline and tubular structure of halloysite. In addition, the number of mesopores and macropores of alkali-treated halloysite increases evidently with increasing NaOH concentration (Fig. 1), which leads to a remarkable increase of adsorption capacity and adsorption rate for OFL. Moreover, NaOH treatment can prolong the release of the adsorbed OFL due to improved hydrogen bonding and cation exchange. Thus, NaOH activation is a simple and effective protocol to improve the adsorption and release of cationic molecules from halloysite.
Scheme 1. The process of baicalin absorption by SPH, baicalin release and the SEM images of the SPH.
Keywords: Superporous hydrogels, Yeast, N-isopropylacrylamide, Baicalin, Controlled drug delivery Acknowledgements Great thanks to the National Nature Science Foundation of China (21104058 & 50973084), and the grant from the Applied Basic Research and Advanced Technology Programs of Science and Technology Commission Foundation of Tianjin (12JCQNJC01400) for financial support References [1] R.A. Gemeinhart, H. Park, K. Park, Pore structure of superporous hydrogels, Polym. Adv. 11 (2000) 617–625. [2] H.Y. Mou, X.J. Wang, T. Lv, L. Xie, H.P. Xie, On-line dissolution determination of baicalin in solid dispersion based on near infrared spectroscopy and circulation dissolution system, Chemom. Intell. Lab. Syst. 105 (2011) 38–42.
doi:10.1016/j.jconrel.2013.08.143
Adsorption and in vitro release of ofloxacin from alkali-treated halloysite Qin Wang, Junping Zhang⁎, Aiqin Wang Center of Eco-material and Green Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China E-mail address: [email protected] (Q. Wang). Halloysite is an aluminosilicate mineral, chemically similar to kaolin and structurally like carbon nanotubes [1]. This special nanotubular structure and the good biocompatibility make halloysite a promising
Fig. 1. Pore size distribution of alkali-treated halloysite samples. 4.0 g of natural halloysite powder suspended in 40 mL of NaOH solution with various concentrations (0.5, 4 and 6 mol L− 1) was sonicated at 50 °C for 1 h, and then washed with distilled water for many times until neutrality and dried at 105 °C to constant weight.
Keywords: Halloysite, Alkali-treatment, Adsorption and release, Ofloxacin Acknowledgements The authors are thankful for the joint supports of the “National Youth Natural Science Foundation of China” (No. 51003112) and the “Special Research Fund of Scholarship of Dean of CAS”. References [1] E. Joussein, S. Petit, J. Churchman, B. Theng, D. Righi, B. Delvaux, Halloysite clay minerals: a review, Clay Miner. 40 (2005) 383–426. [2] Y.M. Lvov, D.G. Shchukin, H. Möhwald, R.R. Price, Halloysite clay nanotubes for controlled release of protective agents, ACS Nano 2 (2008) 814–820. [3] B.C. Du, D. Guo, M. Jia, Newly emerging applications of halloysite nanotubes: a review, Polym. Int. 59 (2010) 574–582.
doi:10.1016/j.jconrel.2013.08.144
Coordination-responsive selenium-containing polymer micelles for controlled drug release Wei Cao, Yang Li, Zhiwei Sun, Huaping Xu⁎ Department of Chemistry, Tsinghua University, Beijing 100084, China E-mail addresses: [email protected] (W. Cao), [email protected] (H. Xu).