Adhesion Of Human Mesenchymal Stem Cells Research Articles

Amorphous silica fiber matrix biomaterials: An analysis of material synthesis and characterization for tissue engineering.

Silica biomaterials including Bioglass offer great biocompatibility and bioactivity but fail to provide pore and degradation features needed for tissue engineering. Herein we report on the synthesis and characterization of novel amorphous silica fiber matrices to overcome these limitations. Amorphous silica fibers were fused by sintering to produce porous matrices. The effects of sacrificial polymer additives such as polyvinyl alcohol (PVA) and cellulose fibers (CF) on the sintering process were also studied. The resulting matrices formed between sintering temperatures of 1,350–1,550 °C retained their fiber structures. The matrices presented pores in the range of 50–200 μm while higher sintering temperatures resulted in increased pore diameter. PVA addition to silica significantly reduced the pore diameter and porosity compared with silica matrices with or without the addition of CF. The PVA additive morphologically appeared to fuse the silica fibers to a greater extent and resulted in significantly higher compressive modulus and strength than the rest of the matrices synthesized. These matrices lost roughly 30% of their original mass in an in vitro degradation study over 40 weeks. All matrices absorbed 500 wt% of water and did not change in their overall morphology, size, or shape with hydration. These fiber matrices supported human mesenchymal stem cell adhesion, proliferation, and mineralized matrix production. Amorphous silica fiber biomaterials/matrices reported here are biodegradable and porous and closely resemble the native extracellular matrix structure and water absorption capacity. Extending the methodology reported here to alter matrix properties may lead to a variety of tissue engineering, implant, and drug delivery applications.

Investigating the physical characteristics and cellular interplay on 3D-printed scaffolds depending on the incorporated silica size for hard tissue regeneration

Silica has been widely used in bone tissue regeneration which is known to increase the bone mineral density and reduce bone resorption. In this study, surface modified silica particles with different sizes (100, 500, and 800 nm) were incorporated with polycaprolactone (PCL) to study the influence of silica particle size on physical and biological properties. Controversial results were observed between the physical and biological properties. In terms of physical properties including surface roughness, hydrophilicity, and mechanical strength, the PCL scaffold with 800 nm-sized particles showed significantly enhanced results. However, the scaffold with 100 nm-sized particles significantly upregulated the biological properties such as human mesenchymal stem cell adhesion, proliferation, and differentiation. This was also relevant for the in vivo results. Altogether, the results proved that the silica particle size influence the physical and biological properties of the PCL scaffold.

Additive manufacturing of biodegradable porous orthopaedic screw

Advent of additive manufacturing in biomedical field has nurtured fabrication of complex, customizable and reproducible orthopaedic implants. Layer-by-layer deposition of biodegradable polymer employed in development of porous orthopaedic screws promises gradual dissolution and complete metabolic resorption thereby overcoming the limitations of conventional metallic screws. In the present study, screws with different pore sizes (916 × 918 μm to 254 × 146 μm) were 3D printed at 200 μm layer height by varying printing parameters such as print speed, fill density and travel speed to augment the bone ingrowth. Micro-CT analysis and scanning electron micrographs of screws with 45% fill density confirmed porous interconnections (40.1%) and optimal pore size (259 × 207 × 200 μm) without compromising the mechanical strength (24.58 ± 1.36 MPa). Due to the open pore structure, the 3D printed screws showed increased weight gain due to the deposition of calcium when incubated in simulated body fluid. Osteoblast-like cells attached on screw and infiltrated into the pores over 14 days of in vitro culture. Further, the screws also supported greater human mesenchymal stem cell adhesion, proliferation and mineralized matrix synthesis over a period of 21 days in vitro culture as compared to non-porous screws. These porous screws showed significantly increased vascularization in a rat subcutaneous implantation as compared to control screws. Porous screws produced by additive manufacturing may promote better osteointegration due to enhanced mineralization and vascularization.

Electrospun nanofiber-reinforced three-dimensional chitosan matrices: Architectural, mechanical and biological properties

The poor intrinsic mechanical properties of chitosan hydrogels have greatly hindered their practical applications. Inspired by nature, we proposed a strategy to enhance the mechanical properties of chitosan hydrogels by construction of a nanofibrous and cellular architecture in the hydrogel without toxic chemical crosslinking. To this end, electrospun nanofibers including cellulose acetate, polyacrylonitrile, and SiO2 nanofibers were introduced into chitosan hydrogels by homogenous dispersion and lyophilization. With the addition of 30% cellulose acetate nanofibers, the cellular structure could be maintained even in water without crosslinking, and integration of 60% of the nanofibers could guarantee the free-standing structure of the chitosan hydrogel with a low solid content of 1%. Moreover, the SiO2 nanofiber-reinforced chitosan (SiO2 NF/CS) three-dimensional (3D) matrices exhibit complete shape recovery from 80% compressive strain and excellent injectability. The cellular architecture and nanofibrous structure in the SiO2 NF/CS matrices are beneficial for human mesenchymal stem cell adhesion and stretching. Furthermore, the SiO2 NF/CS matrices can also act as powerful vehicles for drug delivery. As an example, bone morphogenetic protein 2 could be immobilized on SiO2 NF/CS matrices to induce osteogenic differentiation. Together, the electrospun nanofiber-reinforced 3D chitosan matrices exhibited improved mechanical properties and enhanced biofunctionality, showing great potential in tissue engineering.

Downregulation of vimentin intermediate filaments affect human mesenchymal stem cell adhesion and formation of cellular projections

Mesenchymal stem cells hold great promise as a therapeutic cell source for a variety of diseases such as osteoarthritis and degenerative disc disease. Their unique homing ability and multipotentiality play key roles in their applications in medicine. Specifically, hMSCs capability to adhere and migrate to damaged tissue's extracellular matrix is essential for serving their therapeutic purpose. The roles of some cytoskeletal elements, such as actin and microtubules, in cell migration and adhesion have been well described, while that of intermediate filaments (IFs) is not well understood. There is increasing evidence that vimentin IFs also function in cell spreading and adhesion, but their relationships in MSCs have not been fully characterized. In this work, we sought to understand how vimentin IFs govern adhesion and cellular cytoplasmic projection formation in human MSCs. Using shRNA to knockdown vimentin IFs in MSCs, we found that vimentin IFs are necessary for the cellular structural integrity required for cell-substrate adhesion and for forming and maintaining cellular projections.

Human mesenchymal stem cell behavior on segmented polyurethanes prepared with biologically active chain extenders.

The development of elastomeric, bioresorbable and biocompatible segmented polyurethanes (SPUs) for use in tissue-engineering applications has attracted considerable interest because of the existing need of mechanically tunable scaffolds for regeneration of different tissues, but the incorporation of osteoinductive molecules into SPUs has been limited. In this study, SPUs were synthesized from poly (ε-caprolactone)diol, 4,4'-methylene bis(cyclohexyl isocyanate) using biologically active compounds such as ascorbic acid, L-glutamine, β-glycerol phosphate, and dexamethasone as chain extenders. Fourier transform infrared spectroscopy (FTIR) revealed the formation of both urethanes and urea linkages while differential scanning calorimetry, dynamic mechanical analysis, X-ray diffraction and mechanical testing showed that these polyurethanes were semi-crystalline polymers exhibiting high deformations. Cytocompatibility studies showed that only SPUs containing β-glycerol phosphate supported human mesenchymal stem cell adhesion, growth, and osteogenic differentiation, rendering them potentially suitable for bone tissue regeneration, whereas other SPUs failed to support either cell growth or osteogenic differentiation, or both. This study demonstrates that modification of SPUs with osteogenic compounds can lead to new cytocompatible polymers for regenerative medicine applications.

Electrochemically Preadsorbed Collagen Promotes Adult Human Mesenchymal Stem Cell Adhesion.

The present article reports on the effect of electric potential on the adsorption of collagen type I (the most abundant component of the organic phase of bone) onto optically transparent carbon electrodes (OTCE) and its mediation on subsequent adhesion of adult, human, mesenchymal stem cells (hMSCs). For this purpose, adsorption of collagen type I was investigated as a function of the protein concentration (0.01, 0.1, and 0.25 mg/mL) and applied potential (open circuit potential [OCP; control], +400, +800, and +1500 mV). The resulting substrate surfaces were characterized using spectroscopic ellipsometry, atomic force microscopy, and cyclic voltammetry. Adsorption of collagen type I onto OTCE was affected by the potential applied to the sorbent surface and the concentration of protein. The higher the applied potential and protein concentration, the higher the adsorbed amount (Γcollagen). It was also observed that the application of potential values higher than +800 mV resulted in the oxidation of the adsorbed protein. Subsequent adhesion of hMSCs on the OTCEs (precoated with the collagen type I films) under standard cell culture conditions for 2 h was affected by the extent of collagen preadsorbed onto the OTCE substrates. Specifically, enhanced hMSCs adhesion was observed when the Γcollagen was the highest. When the collagen type I was oxidized (under applied potential equal to +1500 mV), however, hMSCs adhesion was decreased. These results provide the first correlation between the effects of electric potential on protein adsorption and subsequent modulation of anchorage-dependent cell adhesion.

Titanium phosphate glass microcarriers induce enhanced osteogenic cell proliferation and human mesenchymal stem cell protein expression

In this study, we have developed 50- to 100-µm-sized titanium phosphate glass microcarriers (denoted as Ti5) that show enhanced proliferation of human mesenchymal stem cells and MG63 osteosarcoma cells, as well as enhanced human mesenchymal stem cell expression of bone differentiation markers, in comparison with commercially available glass microspheres at all time points. We also demonstrate that these microcarriers provide superior human mesenchymal stem cell proliferation with conventional Dulbecco’s Modified Eagle medium than with a specially developed commercial stem cell medium. The microcarrier proliferative capacity is revealed by a 24-fold increase in MG63 cell numbers in spinner flask bioreactor studies performed over a 7-day period, versus only a 6-fold increase in control microspheres under the same conditions; the corresponding values of Ti5 and control microspheres under static culture are 8-fold and 7-fold, respectively. The capability of guided osteogenic differentiation is confirmed by ELISAs for bone morphogenetic protein-2 and osteopontin, which reveal significantly greater expression of these markers, especially osteopontin, by human mesenchymal stem cells on the Ti5 microspheres than on the control. Scanning electron microscopy and confocal laser scanning microscopy images reveal favorable MG63 and human mesenchymal stem cell adhesion on the Ti5 microsphere surfaces. Thus, the results demonstrate the suitability of the developed microspheres for use as microcarriers in bone tissue engineering applications.

Artificial biomimicking matrix modifications of nanofibrous scaffolds by hE-cadherin-Fc fusion protein to promote human mesenchymal stem cells adhesion and proliferation.

Extracellular matrix (ECM) plays a fundamental role in regulating cell attachment, proliferation, migration and differentiation. Both synthetic and biologically derived materials have been explored as an ECM in regenerative medicine and tissue engineering. To biomimick the extracellular matrix, we combined the advantages of the biological properties of nanofibrous scaffolds and the fusion protein to apply for the culture of human mesenchymal stem cells in vitro. In this study, we fabricated well random-oriented/aligned nanofibrous scaffolds with PCL, modified with hE-cadherin-Fc fusion protein and studied the synergistic effect of the scaffolds. The random-oriented/aligned architecture was observed in the nanofibrous scaffolds by SEM. XPS and WCA measurements evidenced that hE-cadherin-Fc was successfully modified on the PCL nanofibrous scaffolds and hydrophilicity of the scaffolds was well improved after fusion protein coating. The hE-cadherin-Fc modified markedly promoted the adhesion and proliferation of hMSCs and guided hMSCs to a spindlier morphology compared with unmodified nanofibrous scaffolds. Furthermore, hMSCs on the hE-cadherin-Fc-coated nanofibrous scaffolds also had differentiation potential. These results suggested that the combination of PCL nanofibrous scaffolds and hE-cadherin-Fc fusion protein may be a promising artificial ECM for the behavior of hMSCs in vitro.

Lysine-Appended Polydiacetylene Scaffolds for Human Mesenchymal Stem Cells

We report on the self-assembly based fabrication of fibrous polymers for tissue engineering applications. Directed self-assembly followed by polymerization of lysine-appended diacetylenes generated a variety of polymers (P1-P5) with distinct chemical properties. The self-assembly along with the conjugated double and triple bonds and rigid geometry of diacetylene backbone imposed a nanofibrous morphology on the resulting polymers. Chemical properties including wettability of the polymers were tuned by using lysine (Lys) with orthogonal protecting groups (Boc and Fmoc). These Lys-appended polydiacetylene scaffolds were compared in terms of their efficiency toward human mesenchymal stem cells adhesion and spreading. Interestingly, polymer P4 containing Lys N(α)-NH2 and Lys N(ε)-Boc with balanced wettability supported cell adhesion better than the more hydrophobic polymer P2 with N(ε)-Boc and N(α)-Fmoc or more hydrophilic polymer P5 containing free N(ε) and N(α) amino groups. The molecular level control in the fabrication of nanofibrous polymers compared with other existing methods for the generation of fibrous polymers is the hallmark of this work.

Changing ligand number and type within nanocylindrical domains through kinetically constrained self-assembly - impacts of ligand 'redundancy' on human mesenchymal stem cell adhesion and morphology.

In this paper, we firstly describe a facile method by which sequential attachment of different adhesion peptides to a nanotopographical, self-assembled block copolymer cell culture surface is made possible through orthogonal click chemistry. Functionalization of polystyrene-b-polyethylene oxide block copolymers (PS-PEO) with azide (PS-PEO-N3) and aminooxy (PS-PEO-ONH2) moieties permitted the use of orthogonal click chemistry protocols to sequentially add desired bioactive moieties. Thereafter, we show that co-self-assembly of non-functionalised PS-PEO with different amounts of these functionalized PS-PEOs produces polymer films having well-defined, hexagonally arrayed PEO nanocylinder domains, of near constant diameter (∼17 nm diameter) and lateral spacing (∼35 nm). The invariant diameters and lateral spacing of the nanodomains with changes in the amounts of PS-PEO-N3 and PS-PEO-ONH2 confirmed our ability to tune the number density of these functional groups locally within each PEO nanodomain. Stepwise conjugation of alkyne-terminated IKVAV or aldehyde-terminated RGD to the azide and aminooxy decorated nanodomains produced a series of substrates with increasing local number density of grafted adhesion peptides in each nanodomain. We then systematically investigated the impacts of ligand affinity and availability (leading to differing levels of redundancy) on cell integrin binding and adhesion behaviours. We show that with increasing numbers of single peptides (IKVAV or RGD) or with changes in the ratio of IKVAV and RGD peptides within each of the ∼17 nm nanodomains of these films, there was significant changes in the number of hMSCs adhered and substantial modulation of cell morphology, cytoskeletal actin stress fibres and focal adhesion maturation. We observed that increases in the ratio of RGD to IKVAV peptides within the constrained surface nanodomains greatly enhanced hMSC adhesion, and effectively modulated hMSC morphology, cytoskeletal actin structures and focal adhesion number and maturity between the two extremes noted for the single peptides. The results presented suggest that these self assembled block copolymer substrates regulate hMSC adhesion and morphology through modulation of ligand affinity and ligand redundancy, and hence the effectiveness of integrin binding and mechanotransduction signalling. These novel 2D polymer substrates offer encoded and defined cues for cell adhesion at length scales previously unrealised and the results of this investigation expose a new parameter set by which the surfaces of biomaterials may be tailored for stem cell culture, selection and fate.

Bioactive Chemical Nanopatterns Impact Human Mesenchymal Stem Cell Fate

We present a method of preparing and characterizing nanostructured bioactive motifs using a combination of nanoimprint lithography and surface functionalization. Nanodots were fabricated on silicon surfaces and modified with a cell-adhesive RGD peptide for studies in human mesenchymal stem cell adhesion and differentiation. We report that bioactive nanostructures induce mature focal adhesions on human mesenchymal stem cells with an impact on their behavior and dynamics specifically in terms of cell spreading, cell-material contact, and cell differentiation.

Magnetic poly(ε-caprolactone)/iron-doped hydroxyapatite nanocomposite substrates for advanced bone tissue engineering

In biomedicine, magnetic nanoparticles provide some attractive possibilities because they possess peculiar physical properties that permit their use in a wide range of applications. The concept of magnetic guidance basically spans from drug delivery and hyperthermia treatment of tumours, to tissue engineering, such as magneto-mechanical stimulation/activation of cell constructs and mechanosensitive ion channels, magnetic cell-seeding procedures, and controlled cell proliferation and differentiation. Accordingly, the aim of this study was to develop fully biodegradable and magnetic nanocomposite substrates for bone tissue engineering by embedding iron-doped hydroxyapatite (FeHA) nanoparticles in a poly(ε-caprolactone) (PCL) matrix. X-ray diffraction analyses enabled the demonstration that the phase composition and crystallinity of the magnetic FeHA were not affected by the process used to develop the nanocomposite substrates. The mechanical characterization performed through small punch tests has evidenced that inclusion of 10 per cent by weight of FeHA would represent an effective reinforcement. The inclusion of nanoparticles also improves the hydrophilicity of the substrates as evidenced by the lower values of water contact angle in comparison with those of neat PCL. The results from magnetic measurements confirmed the superparamagnetic character of the nanocomposite substrates, indicated by a very low coercive field, a saturation magnetization strictly proportional to the FeHA content and a strong history dependence in temperature sweeps. Regarding the biological performances, confocal laser scanning microscopy and AlamarBlue assay have provided qualitative and quantitative information on human mesenchymal stem cell adhesion and viability/proliferation, respectively, whereas the obtained ALP/DNA values have shown the ability of the nanocomposite substrates to support osteogenic differentiation.

Nanophase hydroxyapatite and poly(lactide-co-glycolide) composites promote human mesenchymal stem cell adhesion and osteogenic differentiation in vitro

Human mesenchymal stem cells (hMSCs) typically range in size from 10 to 50 μm and proteins that mediate hMSC adhesion and differentiation usually have a size of a few nanometers. Nanomaterials with a feature size smaller than 100 nm have demonstrated the unique capability of promoting osteoblast (bone forming cell) adhesion and long-term functions, leading to more effective bone tissue regeneration. For new bone deposition, MSCs have to be recruited to the injury or disease sites and then differentiate into osteoblasts. Therefore, designing novel nanomaterials that are capable of attracting MSCs and directing their differentiation is of great interest to many clinical applications. This in vitro study investigated the effects of nanophase hydroxyapatite (nano-HA), nano-HA/poly(lactide-co-glycolide) (PLGA) composites and a bone morphogenetic protein (BMP-7) derived short peptide on osteogenic differentiation of hMSCs. The short peptide was loaded by physical adsorption to nano-HA or by dispersion in nanocomposites and in PLGA to determine their effects on hMSC adhesion and differentiation. The results showed that the nano-HA/PLGA composites promoted hMSC adhesion as compared to the PLGA controls. Moreover, nano-HA/PLGA composites promoted osteogenic differentiation of hMSCs to a similar extent with or without the presence of osteogenic factors in the media. In the MSC growth media without the osteogenic factors, the nanocomposites supported greater calcium-containing bone mineral deposition by hMSC than the BMP-derived short peptide alone. The nanocomposites provided promising alternatives in controlling the adhesion and differentiation of hMSCs without osteogenic factors from the culture media, and, thus, should be further studied for clinical translation and the development of novel nanocomposite-guided stem cell therapies.

Glycosaminoglycans enhance osteoblast differentiation of bone marrow derived human mesenchymal stem cells

Extracellular matrix plays an important role in regulating cell growth and differentiation. The biomimetic approach of cell-based tissue engineering is based on mirroring this in vivo micro environment for developing a functional tissue engineered construct. In this study, we treated normal tissue culture plates with selected extracellular matrix components consisting of glycosaminoglycans such as chondroitin-4-sulphate, dermatan sulphate, chondroitin-6-sulphate, heparin and hyaluronic acid. Mesenchymal stem cells isolated from adult human bone marrow were cultured on the glycosaminoglycan treated culture plates to evaluate their regulatory role in cell growth and osteoblast differentiation. Although no significant improvement on human mesenchymal stem cell adhesion and proliferation was observed on the glycosaminoglycan-treated tissue culture plates, there was selective osteoblast differentiation, indicating its potential role in differentiation rather than proliferation. Osteoblast differentiation studies showed high osteogenic potential for all tested glycosaminoglycans except chondroitin-4-sulphate. Osteoblast differentiation-associated genes such as osterix, osteocalcin, integrin binding sialoprotein, osteonectin and collagen, type 1, alpha 1 showed significant upregulation. We identified osterix as the key transcription factor responsible for the enhanced bone matrix deposition observed on hyaluronic acid, heparin and chondroitin-6-sulphate. Hyaluronic acid provided the most favourable condition for osteoblast differentiation and bone matrix synthesis. Our results confirm and emphasise the significant role of extracellular matrix in regulating cell differentiation. To summarise, glycosaminoglycans of extracellular matrix played a significant role in regulating osteoblast differentiation and could be exploited in the biomimetic approach of fabricating or functionalizing scaffolds for stem cell based bone tissue engineering.

Design and Optimization of Polyphosphazene Functionalized Fiber Matrices for Soft Tissue Regeneration

Electrospun polycaprolactone nanofiber matrices surface functionalized with poly[(ethyl alanato), (p-methyl phenoxy),] phosphazene were fabricated for the purpose of soft skeletal tissue regeneration. This preliminary study reports the effect of fiber diameter and polyphosphazene surface functionalization on significant scaffold properties such as morphology, surface hydrophilicity, porosity, tensile properties, human mesenchymal stem cell adhesion and proliferation. Six fiber matrices comprised of average fiber diameters in the range of 400-500, 900-1000, 1400-1500, 1900-2000, 2900-3000 and 3900-4000 nm were considered for primary evaluation. After achieving the greatest proliferation while maintaining moderate tensile modulus, matrices in the diameter range of 2900-3000 nm were selected to examine the effect of coating with 1%, 2% and 3% (weight/volume) polyphosphazene solutions. Polyphosphazene functionalization resulted in rougher surfaces that correlated with coating solution concentration. Analytical techniques such as energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, elemental analysis, differential scanning calorimetry, water contact angle goniometry and confocal microscopy confirmed the presence of polyphosphazene and its distribution on the functionalized fiber matrices. Functionalization achieved through 2% polymer solutions did not affect average pore diameter, tensile modulus, suture retention strength or cell proliferation compared to PCL controls. Surface polyphosphazene functionalization significantly improved the matrix hydrophilicity evidenced through decreased water contact angle of PCL matrices from 130 degrees to 97 degrees. Further, enhanced total protein synthesis by cells during in vitro culture was seen on 2% PPHOS functionalized matrices over controls. Improving PCL matrix hydrophilicity via proposed surface functionalization may be an efficient method to improve cell-PCL matrix interactions.

A basic approach toward the development of nanocomposite magnetic scaffolds for advanced bone tissue engineering

AbstractMagnetic scaffolds for bone tissue engineering based on a poly(ε‐caprolactone) (PCL) matrix and iron oxide (Fe3O4) magnetic nanoparticles were designed and developed through a three‐dimensional (3D) fiber‐deposition technique. PCL/Fe3O4 scaffolds were characterized by a 90/10 w/w composition. Tensile and magnetic measurements were carried out, and nondestructive 3D imaging was performed through microcomputed tomography (Micro‐CT). Furthermore, confocal analysis was undertaken to investigate human mesenchymal stem cell adhesion and spreading on the PCL/Fe3O4 nanocomposite fibers. The results suggest that nanoparticles mechanically reinforced the PCL matrix; the elastic modulus and the maximum stress increased about 10 and 30%, respectively. However, the maximum strain decreased about 50%; this suggested an enhanced brittleness. Magnetic results evidenced a superparamagnetic behavior for these nanocomposite scaffolds. Micro‐CT suggested an almost uniform distribution of nanoparticles. Confocal analysis highlighted interesting results in terms of cell adhesion and spreading. All of these results show that a magnetic feature could be incorporated into a polymeric matrix that could be processed to manufacture scaffolds for advanced bone tissue engineering and, thus, provide new opportunity in terms of scaffold fixation and functionalization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Direct growth of oriented Mg–Fe layered double hydroxide (LDH) on pure Mg substrates and in vitro corrosion and cell adhesion testing of LDH-coated Mg samples

This work presents a novel method for directly forming highly-oriented Mg–Fe–CO3 LDH coating on pure Mg samples by treating the sample in pH 5.6 aqueous Fe3+/HCO3−/CO32− at 50 °C, and then immersing it in pH 9.5 aqueous HCO3−/CO32− at 50 °C. The former step was performed to yield Mg2+ in aqueous solution at pH 5.6 by corroding the Mg sample. A two-layered thin film was thus formed on the Mg substrate, of which the outer layer (∼1 μm-thick) comprised fine platelet-like Mg–Fe–CO3 LDH. The latter treatment in pH 9.5 aqueous HCO3−/CO32− at 50 °C resulted in the growth of the fine LDH platelets into a strongly-oriented Mg–Fe–CO3 LDH. The chemical formula of the Mg–Fe–CO3 LDH is Mg0.74Fe0.26(OH)2(CO3)0.13·mH2O. The method used herein involves a metal salt-free system, which requires no addition of Mg(NO3)2 and Fe(NO3)3. Several in vitro tests of the Mg–Fe–CO3 LDH coating on a Mg sample were performed. Based on the measured contact angle between the sample surface and human whole blood, the Mg–Fe–CO3 LDH coating can improve the hydrophilicity of a pure Mg surface. According to the results of an in vitro corrosion test in revised simulated body fluid (R-SBF), the Mg–Fe–CO3 LDH coated sample had a much higher corrosion resistance than the pure Mg substrate. The results of in vitro human mesenchymal stem cell adhesion tests showed that the Mg–Fe–CO3 LDH coated sample had a better cell spreading and cell–cell interaction behavior than the pure Mg substrate.

Patterning the mechanical properties of hydrogen silsesquioxane films using electron beam irradiation for application in mechano cell guidance

Hydrogen silsesquioxane (HSQ) is a material with the potential for studying the effect of surface stiffness on stem cell differentiation. Here, the effects of electron beam dose on the topography and the mechanical properties of HSQ obtained with or without trimethylamine (TMA) development are characterised by atomic force microscopy imaging and indentation. A correlation between the surface stiffness (uniform across the sample) and electron beam exposure is observed. Surface roughness of HSQ samples developed in TMA decreases exponentially with increasing electron beam exposure. Surface coating with plasma polymerised allylamine (ppAAm) leads to an overall decrease in stiffness values. However, the increase in surface stiffness with increasing electron beam exposure is still evident. The ppAAm coating is shown to facilitate human mesenchymal stem cell adhesion.

Surface coatings for improving the corrosion resistance and cell adhesion of AZ91D magnesium alloy through environmentally clean methods

Two different coatings, Mg–Al hydrotalcite and aragonite (CaCO 3), were produced on die-cast AZ91D Mg alloy (Mg–9wt.%Al–1wt.%Zn) through environmentally clean methods. The corrosion resistance and human mesenchymal stem cell adhesion properties of the coatings on AZ91D were investigated. Results showed that through environmentally clean methods, both Mg–Al hydrotalcite and aragonite CaCO 3 surface coatings could be produced on AZ91D surfaces. These coatings increased the corrosion potential and polarization resistance and decreased the corrosion rate of AZ91D in simulated body fluid. Both surface coatings also improved stem cell spreading and interaction in culture. Further long-term animal testing is suggested before these surface coatings can be recommended for use in clinical applications.