Surface micropatterning with calcium phosphate ceramics by micromoulding in capillaries

Abstract

Event Abstract Back to Event Surface micropatterning with calcium phosphate ceramics by micromoulding in capillaries David Barata1, 2, Daniel De Melo Pereira1, 2, Alessandro Resmini3, Sjöerd A. Veldhuis3, Clemens A. Van Blitterswijk1, 2, J E. Ten Elshof3 and Pamela Habibovic1, 2 1 MIRA Institute for Miomedical Technology and Technical Medicine, University of Twente, Department of Tissue Regeneration, Netherlands 2 MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Instructive Biomaterials Engineering, Netherlands 3 MESA+ Institute for Nanotechnology, University of Twente, Inorganic Materials Science, Netherlands Introduction: Current design of biomaterials for regenerative medicine is progressing towards greater control over the biological response in vivo, along with the evolution of the concept of biocompatibility from bioinert to bioactive[1]. Surface patterning is a promising method to achieve spatial control over cell behaviour by physico-chemical cues such as surface chemistry or topography[2]. While a variety of techniques exist to develop patterns of polymers or biomolecules, patterning ceramic materials is explored to a lesser extent and requires further research[3]. This is particularly interesting for the field of bone regeneration, where calcium phosphate (CaP) ceramics are widely used for their close resemblance to bone mineral and associated bioactivity in terms of osteoconduction and osteoinduction[4]. Here we present an approach to micropatterning of surfaces with CaPs by employing micromoulding in capillaries (MIMIC), a method previously shown suitable for patterning zirconia[5]. Materials and Methods: MIMIC was employed to create patterns of dibasic calcium phosphate anhydrous (DCPA) on a flat silicon substrate. Briefly, a polydimethylsiloxane (PDMS) mould with grooves was placed on the silicon substrate to create channels. After air plasma, CaP solution was infiltrated and controlled heating facilitated nucleation and crystal growth inside the microchannels. After completion, the PDMS mould was removed. Selected samples were further annealed to convert DCPA into β-tricalcium phosphate (β-TCP). Substrates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Biocompatibility was assessed by culturing MG-63 osteoblast-like cells on the Si-CaP substrates and analysing cell morphology, metabolic activity and proliferation over a period of 7 days. Results and Discussion: CaP bioceramic patterns were successfully formed by nucleation and growth of crystals in the microchannels. The SEM (Figure 1) and the EDS analyses revealed patterns that were confined to the channels used for patterning. The patterns consisted of flower-like crystals varying in size between 5 and 25 μm. XRD pattern showed peaks characteristic of DCPA (before annealing) and of β-TCP (after annealing). The analysis of cell morphology on the patterns showed the effect of the patterns on cell orientation, an effect that was dependent on the pattern size. Metabolic activity of MG-63 cells showed an increasing trend during the 7-day culture, as did the total DNA amount, confirming the biocompatibility of these materials. The results demonstrated that MIMIC is a suitable technique to fabricate micropatterns of CaP against a chemically different background, and that the created micropatterns can be used to spatially control cell behaviour. Conclusion: MIMIC is a promising technique for patterning of CaP ceramics. Further improvements on the patterning method will focus on obtaining different CaP phases, improving control over the morphology and homogeneity of the CaP pattern, and increasing the complexity of the patterns. DB gratefully acknowledges the financial support of the NIRM (Netherlands Institute of Regenerative Medicine); This research has been in part made possible with the support of the Dutch Province of Limburg