Introducing dip pen nanolithography as a tool for controlling stem cell behaviour: unlocking the potential of the next generation of smart materials in regenerative medicine.
ABSTRACT Reproducible control of stem cell populations, regardless of their original source, is required for the true potential of these cells to be realised as medical therapies, cell biology research tools and in vitro assays. To date there is a lack of consistency in successful output when these cells are used in clinical trials and even simple in vitro experiments, due to cell and material variability. The successful combination of single chemistries in nanoarray format to control stem cell, or any cellular behaviour has not been previously reported. Here we report how homogenously nanopatterned chemically modified surfaces can be used to initiate a directed cellular response, particularly mesenchymal stem cell (MSC) differentiation, in a highly reproducible manner without the need for exogenous biological factors and heavily supplemented cell media. Successful acquisition of these data should lead to the optimisation of cell selective properties of materials, further enhancing the role of nanopatterned substrates in cell biology and regenerative medicine. The successful design and comparison of homogenously molecularly nanopatterned surfaces and their direct effect on human MSC adhesion and differentiation are reported in this paper. Planar gold surfaces were patterned by dip pen nanolithography (DPN) to produce arrays of nanodots with optimised fixed diameter of 70 nanometres separated by defined spacings, ranging from 140 to 1000 nm with terminal functionalities of simple chemistries including carboxyl, amino, methyl and hydroxyl. These nanopatterned surfaces exhibited unprecedented control of initial cell interactions and subsequent control of cell phenotype and offer significant potential for the future.
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ABSTRACT: Mechanotransduction is crucial for cellular processes including cell survival, growth and differentiation. Topographically patterned surfaces offer an invaluable non-invasive means of investigating the cell response to such cues, and greater understanding of mechanotransduction at the cell-material interface has the potential to advance development of tailored topographical substrates and new generation implantable devices. This study focuses on the effects of topographical modulation of cell morphology on chromosomal positioning and gene regulation, using a microgrooved substrate as a non-invasive mechanostimulus. Intra-nuclear reorganisation of the nuclear lamina was noted, and the lamina was required for chromosomal repositioning. It appears that larger chromosomes could be predisposed to such repositioning. Microarrays and a high sensitivity proteomic approach (saturation DiGE) were utilised to identify transcripts and proteins that were subject to mechanoregulated changes in abundance, including mediators of chromatin remodelling and DNA synthesis linked to the changes in nucleolar morphology and the nucleoskeleton.Biomaterials 04/2012; 33(10):2835-47. · 7.60 Impact Factor
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ABSTRACT: A dult stem cells in their niche remain as slow proliferating, metabolically quiescent cells in order to help main-tain self-renewal. Understanding the stem cell niche is important, and exploitation of this knowledge will help develop new tissue en-gineering scaffolds and stem cell therapies. However, it has been problematic to produce an in vitro environment to compare growth, differentiation, and metabolism in differen-tiating and self-renewing mesenchymal stem cells (MSCs), as the appropriate experimental controls have not been available. Current strategies to manipulate stem and progenitor populations typically rely on complex and poorly understood cocktails of soluble factors that slow growth or induce cell differentiation. Materials science presents a different ap-proach to directing stem cell fate in the absence of chemical cues or media supple-ments. Researchers have presented data on the application of the cell/material inter-face (chemistry, 1À4 stiffness, 5 and nanotopo-graphy 6,7) to target MSC differentiation. More recently, MSC/materials interfacial research has shifted focus to maintenance of multipotency (as can be indicated by expression of, for example, STRO1, HOP26 (CD63), and ALCAM (CD166)). 8À10 This is important, as MSCs spontaneously differ-entiate in vitro into heterogeneous popula-tions of differentiated cell types, mainly fibroblasts, with dwindling numbers of trueACS Nano 10/2012; 6(11):10239. · 12.06 Impact Factor
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ABSTRACT: The control of cell-material interactions is the key to a broad range of biomedical interactions. Gradient surfaces have recently been established as tools allowing the high-throughput screening and optimization of these interactions. In this paper, we show that plasma polymer gradients can reveal the subtle influence of surface chemistry on embryonic stem cell behavior and probe the mechanisms by which this occurs. Lateral gradients of surface chemistry were generated by plasma polymerization of diethylene glycol dimethyl ether on top of a substrate coated with an acrylic acid plasma polymer using a tilted slide as a mask. Gradient surfaces were characterized by X-ray photoelectron spectroscopy, infrared microscopy mapping and profilometry. By changing the plasma polymerization time, the gradient profile could be easily manipulated. To demonstrate the utility of these surfaces for the screening of cell-material interactions, we studied the response of mouse embryonic stem (ES) cells to these gradients and compared the performance of different plasma polymerization times during gradient fabrication. We observed a strong correlation between surface chemistry and cell attachment, colony size and retention of stem cell markers. Cell adhesion and colony formation showed striking differences on gradients with different plasma polymer deposition times. Deposition time influenced the depth of the plasma film deposited and the relative position of surface functional group density on the substrate, but not the range of plasma-generated species.Acta biomaterialia 02/2012; 8(5):1739-48. · 3.98 Impact Factor