Christopher Joachim Ochs

Publications (14) View all

• Source

  Available from: Kenichi Funamoto

  Article: A novel microfluidic platform for high-resolution imaging of a three-dimensional cell culture under a controlled hypoxic environment.

  Kenichi Funamoto, Ioannis K Zervantonakis, Yuchun Liu, Christopher J Ochs, Choong Kim, Roger D Kamm
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  ABSTRACT: Low oxygen tensions experienced in various pathological and physiological conditions are a major stimulus for angiogenesis. Hypoxic conditions play a critical role in regulating cellular behaviour including migration, proliferation and differentiation. This study introduces the use of a microfluidic device that allows for the control of oxygen tension for the study of different three-dimensional (3D) cell cultures for various applications. The device has a central 3D gel region acting as an external cellular matrix, flanked by media channels. On each side, there is a peripheral gas channel through which suitable gas mixtures are supplied to establish a uniform oxygen tension or gradient within the device. The effects of various parameters, such as gas and media flow rates, device thickness, and diffusion coefficients of oxygen were examined using numerical simulations to determine the characteristics of the microfluidic device. A polycarbonate (PC) film with a low oxygen diffusion coefficient was embedded in the device in proximity above the channels to prevent oxygen diffusion from the incubator environment into the polydimethylsiloxane (PDMS) device. The oxygen tension in the device was then validated experimentally using a ruthenium-coated (Ru-coated) oxygen-sensing glass cover slip which confirmed the establishment of low uniform oxygen tensions (<3%) or an oxygen gradient across the gel region. To demonstrate the utility of the microfluidic device for cellular experiments under hypoxic conditions, migratory studies of MDA-MB-231 human breast cancer cells were performed. The microfluidic device allowed for imaging cellular migration with high-resolution, exhibiting an enhanced migration in hypoxia in comparison to normoxia. This microfluidic device presents itself as a promising platform for the investigation of cellular behaviour in a 3D gel scaffold under varying hypoxic conditions.
  Lab on a Chip 09/2012; 12(22):4855-63. · 5.67 Impact Factor
• Source

  Available from: Almar Postma

  Article: Immobilization and intracellular delivery of an anticancer drug using mussel-inspired polydopamine capsules.

  Jiwei Cui, Yan Yan, Georgina K Such, Kang Liang, Christopher J Ochs, Almar Postma, Frank Caruso
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  ABSTRACT: We report a facile approach to immobilize pH-cleavable polymer-drug conjugates in mussel-inspired polydopamine (PDA) capsules for intracellular drug delivery. Our design takes advantage of the facile PDA coating to form capsules, the chemical reactivity of PDA films, and the acid-labile groups in polymer side chains for sustained pH-induced drug release. The anticancer drug doxorubicin (Dox) was conjugated to thiolated poly(methacrylic acid) (PMA(SH)) with a pH-cleavable hydrazone bond, and then immobilized in PDA capsules via robust thiol-catechol reactions between the polymer-drug conjugate and capsule walls. The loaded Dox showed limited release at physiological pH but significant release (over 85%) at endosomal/lysosomal pH. Cell viability assays showed that Dox-loaded PDA capsules enhanced the efficacy of eradicating HeLa cancer cells compared with free drug under the same assay conditions. The reported method provides a new platform for the application of stimuli-responsive PDA capsules as drug delivery systems.
  Biomacromolecules 07/2012; 13(8):2225-8. · 5.48 Impact Factor
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  Available from: Christopher Joachim Ochs

  Article: Flake-shell capsules: adjustable inorganic structures.

  Qingmin Ji, Chunyan Guo, Xiaoyan Yu, Christopher J Ochs, Jonathan P Hill, Frank Caruso, Hiromoto Nakazawa, Katsuhiko Ariga
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  ABSTRACT: Structure-adjustable capsules are fabricated from inorganic components by using a self-template dissolution-regrowth mechanism to give flake-shell silica microcapsules. The capsules shrink under thermal stimulus and their structures can be adjusted by treatment at different pH values. Tuning of shell pore diameters leads to tailored drug release over prolonged periods.
  Small 05/2012; 8(15):2345-9. · 8.35 Impact Factor
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  Available from: Christopher Joachim Ochs

  Article: ATRP-mediated continuous assembly of polymers for the preparation of nanoscale films.

  Damien Mertz, Christopher J Ochs, Zhiyuan Zhu, Lillian Lee, Stefanie N Guntari, Georgina K Such, Tor Kit Goh, Luke A Connal, Anton Blencowe, Greg G Qiao, Frank Caruso
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  ABSTRACT: The continuous assembly of polymers (CAP) via atom transfer radical polymerisation (ATRP) is reported as an efficient approach for the preparation of dense, cross-linked, nanoscale engineered films as surface coatings, hollow capsules and replica particles. These films can be reinitiated to allow the preparation of thicker films without loss of film growth efficiency while maintaining similar film density.
  Chemical Communications 11/2011; 47(47):12601-3. · 6.17 Impact Factor
• Source

  Available from: Christopher Joachim Ochs

  Article: Nanoengineered films via surface-confined continuous assembly of polymers.

  Tor Kit Goh, Stefanie N Guntari, Christopher J Ochs, Anton Blencowe, Damien Mertz, Luke A Connal, Georgina K Such, Greg G Qiao, Frank Caruso
  Small 10/2011; 7(20):2863-7. · 8.35 Impact Factor