Fabrication and modelling of fractal, biomimetic, micro and nano-topographical surfaces.

Natural surface topographies are often self-similar with hierarchical features at the micro and nanoscale, which may be mimicked to overcome modern tissue engineering and biomaterial design limitations. Specifically, a cell's microenvironment within the human body contains highly optimised, fractal topographical cues, which directs precise cell behaviour. However, recreating biomimetic, fractal topographies in vitro is not a trivial process and a number of fabrication methods have been proposed but often fail to precisely control the spatial resolution of features at different lengths scales and hence, to provide true biomimetic properties. Here, we propose a method of accurately reproducing the self-similar, micro and nanoscale topography of a human biological tissue into a synthetic polymer through an innovative fabrication process. The biological tissue surface was characterised using atomic force microscopy (AFM) to obtain spatial data in X, Y and Z, which was converted into a grayscale 'digital photomask'. As a result of maskless grayscale optical lithography followed by modified deep reactive ion etching and replica molding, we were able to accurately reproduce the fractal topography of acellular dermal matrix (ADM) into polydimethylsiloxane (PDMS). Characterisation using AFM at three different length scales revealed that the nano and micro-topographical features, in addition to the fractal dimension, of native ADM were reproduced in PDMS. In conclusion, it has been shown that the fractal topography of biological surfaces can be mimicked in synthetic materials using the novel fabrication process outlined, which may be applied to significantly enhance medical device biocompatibility and performance.

Enhanced Contraction of a Normal Breast-Derived Fibroblast-Populated Three-Dimensional Collagen Lattice via Contracted Capsule Fibroblast-Derived Paracrine Factors: Functional Significance in Capsular Contracture Formation.

BACKGROUND: The authors' aim was to identify morphological, genotypic, and cytokine profiles of normal breast-derived fibroblasts, noncontracted breast implant capsule (Baker grades 1 and 2) fibroblasts, and contracted breast implant capsule (Baker grades 3 and 4) fibroblasts, and to investigate the paracrine effects of contracted breast capsule fibroblast--conditioned media on a breast-derived fibroblast-populated three-dimensional collagen lattice. METHODS: Primary breast-derived fibroblasts (n = 5), noncontracted breast capsule fibroblasts (n = 5), and contracted breast capsule fibroblasts (n = 5) were cultured, and conditioned media were obtained from passage 1 cells. Cells were immunostained for alpha smooth muscle actin to identify myofibroblasts. A panel of 16 inflammatory, fibrosis, extracellular matrix, and tissue remodeling-related genes were investigated using quantitative reverse transcriptase polymerase chain reaction and cytokine arrays. Fibroblast-populated collagen lattices were fabricated and treated with conditioned media, and lattice contracture was measured over 5 days. RESULTS: Several inflammatory and fibrotic genes were significantly dysregulated in contracted breast capsule fibroblasts compared with noncontracted breast capsule fibroblasts and breast-derived fibroblasts (p < 0.05). Breast-derived fibroblast-populated collagen lattices treated with contracted breast capsule fibroblast-conditioned media demonstrated increased lattice contraction compared with treatment with normal 10% serum media (control), breast-derived fibroblasts, or noncontracted breast capsule fibroblast-conditioned media (p < 0.05). Breast-derived fibroblasts supplemented with contracted breast capsule fibroblast-conditioned media transformed into a contracted breast capsule fibroblast-like cell (p < 0.05). CONCLUSION: The authors show that contracted breast capsule-derived fibroblasts induce normal breast fibroblast transformation and contraction via paracrine signaling, which may contribute to capsular contracture formation.

Development and functional evaluation of biomimetic silicone surfaces with hierarchical micro/nano-topographical features demonstrates favourable in vitro foreign body response of breast-derived fibroblasts.

Reproducing extracellular matrix topographical cues, such as those present within acellular dermal matrix (ADM), in synthetic implant surfaces, may augment cellular responses, independent of surface chemistry. This could lead to enhanced implant integration and performance while reducing complications. In this work, the hierarchical micro and nanoscale features of ADM were accurately and reproducibly replicated in polydimethylsiloxane (PDMS), using an innovative maskless 3D grayscale fabrication process not previously reported. Human breast derived fibroblasts (n=5) were cultured on PDMS surfaces and compared to commercially available smooth and textured silicone implant surfaces, for up to one week. Cell attachment, proliferation and cytotoxicity, in addition to immunofluorescence staining, SEM imaging, qRT-PCR and cytokine array were performed. ADM PDMS surfaces promoted cell adhesion, proliferation and survival (p=<0.05), in addition to increased focal contact formation and spread fibroblast morphology when compared to commercially available implant surfaces. PCNA, vinculin and collagen 1 were up-regulated in fibroblasts on biomimetic surfaces while IL8, TNFα, TGFß1 and HSP60 were down-regulated (p=<0.05). A reduced inflammatory cytokine response was also observed (p=<0.05). This study represents a novel approach to the development of functionalised biomimetic prosthetic implant surfaces which were demonstrated to significantly attenuate the acute in vitro foreign body reaction to silicone.

Identification of molecular phenotypic descriptors of breast capsular contracture formation using informatics analysis of the whole genome transcriptome.

Breast capsular contracture formation following silicone implant augmentation/reconstruction is a common complication that remains poorly understood. The aim of this study was to identify potential biomarkers implicated in breast capsular contracture formation by using, for the first time, whole genome arrays. Biopsy samples were taken from 18 patients (23 breast capsules) with Baker Grade I-II (Control) and Baker Grade III-IV (Contracted). Whole genome microarrays were performed and six significantly dysregulated genes were selected for further validation with quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. Hematoxylin and eosin was also carried out to compare the histological characteristics of control and contracted samples. Microarray results showed that aggrecan, tissue inhibitor of metalloproteinase 4 (TIMP4), and tumor necrosis factor superfamily (ligand) member 11 were significantly down-regulated in contracted capsules; while matrix metallopeptidase 12, serum amyloid A 1, and interleukin 8 (IL8) were significantly up-regulated. The dysregulation of aggrecan, tumor necrosis factor superfamily (ligand) member 11, TIMP4, and IL8 was validated by quantitative reverse transcriptase polymerase chain reaction (p < 0.05). Immunohistochemistry confirmed an increased protein expression for IL8 and matrix metallopeptidase 12 in contracted capsules (p < 0.05), and decreased protein expression of TIMP4 (p < 0.05). This study has shown, for the first time, a number of unique biomarkers of significance in capsular contracture formation. IL8 and TIMP4 may serve as potential key diagnostic, therapeutic, and prognostic biomarkers in capsular contracture formation.