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Bacterial infection remains a significant problem associated with orthopaedic surgeries leading to surgical site infection (SSI). This unmet medical need can become an even greater complication when surgery is due to malignant bone tumor. In the present study, we evaluated in vitro titanium (Ti) implants subjected to gallium (Ga) and silver (Ag)-doped thermochemical treatment as strategy to prevent SSI and improve osteointegration in bone defects caused by diseases such as osteoporosis, bone tumor, or bone metastasis. Firstly, as Ga has been reported to be an osteoinductive and anti-resorptive agent, its performance in the mixture was proved by studying human mesenchymal stem cells (hMSC) and pre-osteoclasts (RAW264.7) behaviour. Then, the antibacterial potential provided by Ag was assessed by resembling "The Race for the Surface" between hMSC and Pseudomonas aeruginosa in two co-culture methods. Moreover, the presence of quorum sensing molecules in the co-culture was evaluated. The results highlighted the suitability of the mixture to induce osteodifferentiation and reduce osteoclastogenesis in vitro. Furthermore, the GaAg surface promoted strong survival rate and retained osteoinduction potential of hMSCs even after bacterial inoculation. Therefore, GaAg-modified titanium may be an ideal candidate to repair bone defects caused by excessive bone resorption, in addition to preventing SSI. STATEMENT OF SIGNIFICANCE: This article provides important insights into titanium for fractures caused by osteoporosis or bone metastases with high incidence in surgical site infection (SSI) because in this situation bacterial infection can become a major disaster. In order to solve this unmet medical need, we propose a titanium implant modified with gallium and silver to improve osteointegration, reduce bone resorption and avoid bacterial infection. For that aim, we study osteoblast and osteoclast behavior with the main novelty focused on the antibacterial evaluation. In this work, we recreate "the race for the surface" in long-term experiments and study bacterial virulence factors (quorum sensing). Therefore, we believe that our article could be of great interest, providing a great impact on future orthopedic applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The ability to control cell behaviour, cell fate and simulate reliable tissue models in vitro remains a significant challenge yet is crucial for various applications of high throughput screening e.g. drug discovery. Mechanotransduction (the ability of cells to convert mechanical forces in their environment to biochemical signalling) represents an alternative mechanism to attain this control with such studies developing techniques to reproducibly control the mechanical environment in techniques which have potential to be scaled. In this review, the use of techniques such as finite element modelling and precision interferometric measurement are examined to provide context for a novel technique based on nanoscale vibration, also known as "nanokicking". Studies have shown this stimulus to alter cellular responses in both endothelial and mesenchymal stem cells (MSCs), particularly in increased proliferation rate and induced osteogenesis respectively. Endothelial cell lines were exposed to nanoscale vibration amplitudes across a frequency range of 1-100 Hz, and MSCs primarily at 1 kHz. This technique provides significant potential benefits over existing technologies, as cellular responses can be initiated without the use of expensive engineering techniques and/or chemical induction factors. Due to the reproducible and scalable nature of the apparatus it is conceivable that nanokicking could be used for controlling cell behaviour within a wide array of high throughput procedures in the research environment, within drug discovery, and for clinical/therapeutic applications., Statement of Significance: The results discussed within this article summarise the potential benefits of using nanoscale vibration protocols for controlling cell behaviour. There is a significant need for reliable tissue models within the clinical and pharma industries, and the control of cell behaviour and stem cell differentiation would be highly beneficial. The full potential of this method of controlling cell behaviour has not yet been realised., (Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Recently we identified a novel population of mesenchymal stem cells (MSCs) from human olfactory mucosa (OM-MSCs), a tissue which promotes neurogenesis throughout life, and demonstrated that they promoted CNS myelination to a greater extent than bone marrow-derived (BM)-MSCs. Previous data demonstrated that nanotopographies with a degree of disorder induce BM-MSC osteogenic differentiation. Thus, using biomaterials as non-chemical tools, we investigated if MSCs from a completely different cellular niche could be induced to differentiate similarly to nanoscale cues alone. Both MSCs differentiated into bone when cultured on nanotopographically embossed polycaprolactone (PCL) with a disordered pattern and heights but not on a "smooth" non-embossed PCL control substrate, but OM-MSC changes were at lower expression levels. Both MSCs showed similar increases in differentiation markers at the protein and mRNA level when plated on the two patterned surfaces. Thus, topographical cues from substrates with disordered patterns can up-regulate several MSC resident genes in both BM-MSCs and OM-MSCs. Moreover, antibody purified BM-MSCs had similar properties to non-purified BM-MSCs. These data suggest that MSCs from a neural cellular niche express similar bone-induced cues to BM-MSCs, suggesting that MSCs that inherently support nervous tissue can differentiate along the bone lineage in a similar manner to MSCs from a skeletal environment., (Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The differentiation of progenitor cells is dependent on more than biochemical signalling. Topographical cues in natural bone extracellular matrix guide cellular differentiation through the formation of focal adhesions, contact guidance, cytoskeletal rearrangement and ultimately gene expression. Osteoarthritis and a number of bone disorders present as growing challenges for our society. Hence, there is a need for next generation implantable devices to substitute for, or guide, bone repair in vivo. Cellular responses to nanometric topographical cues need to be better understood in vitro in order to ensure the effective and efficient integration and performance of these orthopedic devices. In this study, the FDA-approved plastic polycaprolactone was embossed with nanometric grooves and the response of primary and immortalized osteoprogenitor cells observed. Nanometric groove dimensions were 240 nm or 540 nm deep and 12.5 μm wide. Cells cultured on test surfaces followed contact guidance along the length of groove edges, elongated along their major axis and showed nuclear distortion; they formed more focal complexes and lower proportions of mature adhesions relative to planar controls. Down-regulation of the osteoblast marker genes RUNX2 and BMPR2 in primary and immortalized cells was observed on grooved substrates. Down-regulation appeared to directly correlate with focal adhesion maturation, indicating the involvement of ERK 1/2 negative feedback pathways following integrin-mediated FAK activation., (Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Biomimicry is being used in the next generation of biomaterials. Tuning material surface features such as chemistry, stiffness and topography allow the control of cell adhesion, proliferation, growth and differentiation. Here, microtopographical features with nanoscale depths, similar in scale to osteoclast resorption pits, were used to promote in vitro bone formation in basal medium. Primary human osteoblasts were used to represent an orthopaedically relevant cell type and analysis of adhesions, cytoskeleton, osteospecific proteins (phospho-Runx2 and osteopontin) and mineralisation (alizarin red) was performed. The results further demonstrate the potential for biomimicry in material design and show that the osteoblast response can be tuned from changes in feature size., (Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Human skeletal stem cells (STRO-1 positive/STRO-1+) respond to different topographical features in various ways. On a flat surface these cells spread and tend to develop a fibroblast-like morphology. On a microgrooved surface enriched skeletal stem cell populations prefer to stretch along the grooves, which affects their cellular structure and differentiation, a phenomenon known as contact guidance. Growth factors, hormones and chemicals can also stimulate cell differentiation. A traditional Chinese medicine, puerariae radix, has previously been observed to stimulate bone formation. The active ingredients have been identified as isoflavones with estrogen-like bioactivity. This study combined the effects of microgrooved topology and hormone-like isoflavones in the biodegradable polymer polycaprolactone (PCL). Human osteogenic cells (STRO-1+) were cultured on flat PCL, grooved PCL and puerariae powder-impregnated grooved PCL for 5 weeks. Coomassie staining indicated that cell growth and survival was similar on flat PCL, grooved PCL and grooved PCL impregnated with 1 wt.% or 2 wt.% puerariae powder. Grooved PCL impregnated with 2 wt.% puerariae powder was observed to have an influence on protein expression, as observed by positive osteocalcin staining. Protein expression profiles were analyzed by difference gel electrophoresis to identify proteins that showed modulation of expression in response to these different environments. Overall, our results suggest that puerariae powder has an additive effect, along with microgrooved topographical stimulation, to promote changes in the STRO-1+ proteome that affect cell phenotype., (2010. Published by Elsevier Ltd.)

Surface nanotopography is known to influence the interaction of human skeletal (mesenchymal) stem cells (hMSC) with a material surface. While most surface nanopatterning has been performed on polymer-based surfaces there is a need for techniques to produce well-defined topography features with tuneable sizes on relevant load-bearing implant materials such as titanium (Ti). In this study titania nanopillar structures with heights of either 15, 55 or 100 nm were produced on Ti surfaces using anodization through a porous alumina mask. The influence of the surface structure heights on hMSC adhesion, spreading, cytoskeletal formation and differentiation was examined. The 15 nm high topography features resulted in the greatest cell response with bone matrix nodule forming on the Ti surface after 21 days.

We have used a recent comparative proteomics technique, differential in-gel electrophoresis (DIGE), to study osteoprogenitor cell response to contact guidance in grooves. In order to increase protein output from small sample sizes, we used bioreactor culture before protein extraction and gel electrophoresis. Mass spectroscopy was used for protein identification. A number of distinct proteins were observed to exhibit significant changes in expression. These changes in protein expression suggest that the cells respond to tailored grooved topographies, with alterations in their proteome concurrent with changes in osteoprogenitor phenotype.