Adhesion Density Research Articles

Heart failure impairs the mechanotransduction properties of human cardiac pericytes

The prominent impact that coronary microcirculation disease (CMD) exerts on heart failure symptoms and prognosis, even in the presence of macrovascular atherosclerosis, has been recently acknowledged. Experimental delivery of pericytes in non-revascularized myocardial infarction improves cardiac function by stimulating angiogenesis and myocardial perfusion.Aim of this work is to verify if pericytes (Pc) residing in ischemic failing human hearts display altered mechano-transduction properties and to assess which alterations of the mechano-sensing machinery are associated with the observed impaired response to mechanical cues. ResultsMicrovascular rarefaction and defects of YAP/TAZ activation characterize failing human hearts. Although both donor (D-) and explanted (E-) heart derived cardiac Pc support angiogenesis, D-Pc exert this effect significantly better than E-Pc. The latter are characterized by reduced focal adhesion density, decreased activation of the focal adhesion kinase (FAK)/ Crk-associated substrate (CAS) pathway, low expression of caveolin-1, and defective transduction of extracellular stiffness into cytoskeletal stiffening, together with an impaired response to both fibronectin and lysophosphatidic acid. Importantly, Mitogen-activated protein kinase kinase inhibition restores YAP/TAZ nuclear translocation. ConclusionHeart failure impairs Pc mechano-transduction properties, but this defect could be reversed pharmacologically.

BIND (II), characterization of die wall surface modifications for good manufacturing using the surface replication method

Die wall surface modifications are used in pharmaceutical manufacturing; however, selection of the optimal surface modification remains challenging because of a lack of analytical tools. The present study was undertaken to characterize the binding properties of pharmaceutics on die walls with various surface modifications using a new analytical tool: Binding Identification for Net Detriment (BIND). The surface modifications of die walls with and without tapering treatment examined were (i) hard chrome plating (HCr), (ii) chromium nitride coating (CrN), and (iii) mirror subsurface treatment and CrN-coating (CTOP/CrN). Losartan potassium (LP) was chosen as the model chemical. BIND was employed to clarify the influence of surface modification of the die wall on the binding characteristics of the highly-adhesive LP formulation. Use of the die without any modification led to poor tableting properties, as evidenced by a 60.4% powder adhesion density. Surface modifications of the die wall resulted in significant attenuation of binding, reducing the powder adhesion density to 16.6% (HCr), 13.9% (CrN), and 10.8% (CTOP/CrN). Tapering treatment successfully reduced the powder adhesion by 2.9–5.8%. Surface-polishing with HCr made no significant difference to powder adhesion, whereas differences were observed for CrN. Thus, the BIND results suggested that the combined use of CTOP/CrN and tapering treatment is effective for stable production. In this first attempt, BIND can be available for analyzing the effects of die wall surface modifications on the binding characteristics.

Investigation on the interface characteristic between TiN and diamond by first-principles calculation

The electronic and elastic properties of TiN and diamond were calculated by first-principles method in this paper. Then, the work of adhesion (Wad) and charge density difference before and after relaxation of the TiN(111)/diamond(111) interface were analyzed. The calculated results show that TiN has a certain metallicity, which is mainly contributed by electrons in Ti-3d orbital. However, the diamond is an insulator with a bandgap of 4.77 eV. Furthermore, both diamond and TiN are with anisotropy, while the transverse deformation ability of the diamond is stronger than that of TiN. According to the two termination of TiN (111) surface, which are N-terminated and Ti-terminated surfaces, Ti/C (TiN (111) Ti-terminated/diamond (111)) and N/C (TiN (111) N-terminated/diamond (111)) interfaces were established. The bonding strength of Ti/C and N/C interfaces is decreased after relaxation, which is attributed to graphitization transformation of the diamond. The charge transfers at the interfaces of Ti/C and N/C are also changed before and after relaxation, which results in the change of the electrostatic interaction of atoms at the interface, therefore the interfacial bonding is reduced.

Selection of established tumour cells through narrow diameter micropores enriches for elevated Ras/Raf/MEK/ERK MAPK signalling and enhanced tumour growth

ABSTRACT As normal cells become cancer cells, and progress towards malignancy, they become progressively softer. Advantages of this change are that tumour cells become more deformable, and better able to move through narrow constraints. We designed a positive selection strategy that enriched for cells which could move through narrow diameter micropores to identify cell phenotypes that enabled constrained migration. Using human MDA MB 231 breast cancer and MDA MB 435 melanoma cancer cells, we found that micropore selection favoured cells with relatively higher Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) signalling, which affected actin cytoskeleton organization, focal adhesion density and cell elasticity. In this follow-up study, we provide further evidence that selection through micropores enriched for cells with altered cell morphology and adhesion. Additional analysis of RNA sequencing data revealed a set of transcripts associated with small cell size that was independent of constrained migration. Gene set enrichment analysis identified the ‘matrisome’ as the most significantly altered gene set linked with small size. When grown as orthotopic xenograft tumours in immunocompromised mice, micropore selected cells grew significantly faster than Parent or Flow-Sorted cells. Using mathematical modelling, we determined that there is an interaction between 1) the cell to gap size ratio; 2) the bending rigidity of the cell, which enable movement through narrow gaps. These results extend our previous conclusion that Ras/Raf/MEK/ERK MAPK signalling has a significant role in regulating cell biomechanics by showing that the selective pressure of movement through narrow gaps also enriches for increased tumour growth in vivo.

The Effect of β2-Adrenoceptor Agonists on Leucocyte-Endothelial Adhesion in a Rodent Model of Laparotomy and Endotoxemia.

Background: The β2-adrenoceptor agonist dopexamine may possess anti-inflammatory actions which could reduce organ injury during endotoxemia and laparotomy. Related effects on leucocyte-endothelial adhesion remain unclear.Methods: Thirty anesthetized Wistar rats underwent laparotomy followed by induction of endotoxemia with lipopolysaccharide and peptidoglycan (n = 24) or sham (n = 6). Animals received dopexamine at 0.5 or 1 μg kg−1 min−1 (D0.5 and D1), salbutamol at 0.1 μg kg−1 min−1, or saline vehicle (Sham and Control) for 5 h. Intravital microscopy was performed in the ileum of the small intestine to assess leucocyteendothelial adhesion, arteriolar diameter, and functional capillary density. Global hemodynamics and biochemical indices of renal and hepatic function were also measured.Results: Endotoxemia was associated with an increase in adherent leucocytes in post-capillary venules, intestinal arteriolar vasoconstriction as well-reduced arterial pressure and relative cardiac index, but functional capillary density in the muscularis was not significantly altered. Dopexamine and salbutamol administration were associated with reduced leucocyte-endothelial adhesion in post-capillary venules compared to control animals. Arteriolar diameter, arterial pressure and relative cardiac index all remained similar between treated animals and controls. Functional capillary density was similar for all groups. Control group creatinine was significantly increased compared to sham and higher dose dopexamine.Conclusions: In a rodent model of laparotomy and endotoxemia, β2-agonists were associated with reduced leucocyte-endothelial adhesion in post-capillary venules. This effect may explain some of the anti-inflammatory actions of these agents.

Author Correction: Photoinduced self-initiated graft polymerization of methacrylate monomers on poly(ether ether ketone) substrates and surface parameters for controlling cell adhesion

One of the super engineering plastics, poly(ether ether ketone) (PEEK), was functionalized by photoinduced self-initiated graft polymerization of various methacrylate monomers. Anionic, cationic, zwitterionic, nonionic hydrophilic, and nonionic hydrophobic polymer layers were formed onto PEEK substrates. Physical and chemical surface characterizations of the resultant polymer-grafted PEEK substrates were performed through measurements of their surface free energies and ζ potentials. The values of these parameters varied in the ranges of 39–71 mJ/m2 and −69 to 46 mV, respectively. These parameters reflected the chemical structures of the grafted polymers. To understand the effects of these surface parameters on cell adhesion behavior at the substrate surface, the amount of fibronectin adsorbed on the plasma-contacting surface and the density of fibroblast cells adhered to the surface were determined. The adherent cell density showed a good linear correlation with the amount of fibronectin adsorbed on the plasma-contacting surface. The polymer surface with zero ζ potential showed a lower adsorbed fibronectin density. Both anionic and cationic polymer layers had increased cell adhesion compared with that on the original PEEK substrate, whereas the zwitterionic polymer layers significantly prevented cell adhesion. In conclusion, grafting zwitterionic polymers onto a PEEK substrate is anticipated to be useful in the development of a biomedical PEEK substrate. To obtain functionalization of super-engineering plastic, poly(ether ether ketone) (PEEK) substrate, photoinduced self-initiated graft polymerization of several kinds of functional methacrylate was carried out. Graft polymerization proceeded well, and 50–250 nm in thickness graft polymer layers were generated on the PEEK substrate. Surface characteristics such as surface free energy and surface ζ potential on the polymer-grafted PEEK substrate were corresponded to the chemical structure of the graft polymers. Cell attachment on the polymer-grafted PEEK substrate was examined. The surface ζ potentials of the polymer-grafted PEEK substrates governed the cell adhesion density.

First-principles investigation of interfacial stability, mechanical behavior and failure mechanism of β-SiC(1 1 1)/Al(1 1 1) interfaces

In this work, the interfacial stability, mechanical behavior and failure mechanism of β-SiC(1 1 1)/Al(1 1 1) interfaces are systematically investigated by the first-principles simulations based on density functional theory. By stacking the Al(1 1 1) slab with five atom-layers on the β-SiC(1 1 1) slab with seven atom-layers, C-top, C-center, C-hollow, Si-top, Si-center and Si-hollow interfacial models are established according to their different terminations and stacking sequences. Based on simulated results of interfacial energy, work of adhesion and electron density, the C-top and Si-top models provide the most stable interfacial structures with largest work of adhesion and most stable electronic structure. C-top and Si-top models possess the ultimate tensile strengths of 6.33 and 6.65 GPa, while the tensile strains are separately 10% and 12%. Meanwhile, the tensile interfacial fractures appear in the Al slabs of all six interfacial models. For the C-top and Si-top models, the shear strengths are 5.38 and 5.34 GPa, while the shear strains are 12% and 12% respectively. Moreover, the shear slipping along <1 1¯ 0> directions occur in the Al slabs far from the interface for C-top model and close to the interface for Si-top model. In conclusion, an atomic-scale investigation on interfacial structures and mechanical deformations of β-SiC/Al interfaces can be brought into light for designing, fabricating and processing new ceramic/metal composites.

Effect of van der Waals interactions on the adhesion strength at the interface of the hydroxyapatite-titanium biocomposite: a first-principles study.

Hydroxyapatite (HAP) is frequently used as biocompatible coating on Ti-based implants. In this context, the HAP-Ti adhesion is of crucial importance. Here, we report ab initio calculations to investigate the influence of Si incorporation into the amorphous calcium-phosphate (a-HAP) structure on the interfacial bonding mechanism between the a-HAP coating and an amorphous titanium dioxide (a-TiO2) substrate, contrasting two different density functionals: PBE-GGA, and DFT-D3, which are capable of describing the influence of the van der Waals (vdW) interactions. In particular, we discuss the effect of dispersion on the work of adhesion (Wad), equilibrium geometries, and charge density difference (CDD). We find that replacement of P by Si in a-HAP (a-Si-HAP) with the creation of OH vacancies as charge compensation results in a significant increase in the bond strength between the coating and substrate in the case of using the PBE-GGA functional. However, including the vdW interactions shows that these forces considerably contribute to the Wad. We show that the difference (Wad − Wad(vdW)) is on average more than 1.1 J m−2 and 0.5 J m−2 for a-HAP/a-TiO2 and a-Si-HAP/a-TiO2, respectively. These results reveal that including vdW interactions is essential for accurately describing the chemical bonding at the a-HAP/a-TiO2 interface.

Properties and performance of Ag(I) ion imprinted PVDF-PVA/GO composite membrane: Enhanced permeability, rejection and anti-microbial ability

A novel composite membrane with enhanced permeability, rejection and anti-microbial ability was fabricated through chemical modification of PVDF membrane with silver (Ag) ion imprinted poly(vinyl alcohol)/graphene oxide (PVA/GO) thin layer. The physico-chemical properties of the membranes were investigated by a series of analysis techniques. The membrane filtration performance, i.e., pure water flux and rejection efficiency of NaCl, MgSO4 and bovine serum albumin (BSA), was found to be highly affected by the modification processes. Although rejection performance of the H-PVDF-PVA/GO-m-Ag membrane was observed to be slightly decreased compared to that of the H-PVDF-PVA/GO membrane, the uniform imprinting of Ag ions on the membrane surface can endow the membrane with excellent anti-microbial ability. According to results from both batch and dynamic filtration experiments, the H-PVDF-PVA/GO-m-Ag membrane can effectively inactivate 58% and 100% of Pseudomonas aeruginosa cells after incubation for 1 and 4 ​h, respectively and reduce approximately 94% of surface adhesion density. The prepared membrane with the excellent anti-biofouling ability exhibited a promising application potential in water treatment processes.

Antimicrobial Bioresorbable Mg-Zn-Ca Alloy for Bone Repair in a Comparison Study with Mg-Zn-Sr Alloy and Pure Mg.

Magnesium-zinc-calcium (Mg-Zn-Ca) alloys have attracted increasing attention for biomedical implant applications, especially for bone repair, because of their biocompatibility, biodegradability, and similar mechanical properties to human bone. The objectives of this study were to characterize Mg-2 wt % Zn-0.5 wt % Ca (named ZC21) alloy pins microstructurally and mechanically, and determine their degradation and interactions with host cells and pathogenic bacteria in vitro and in vivo in comparison with the previously studied Mg-4 wt % Zn-1 wt % strontium (named ZSr41) alloy and Mg control. Specifically, the in vitro degradation and cytocompatibility of ZC21 pins with bone marrow derived mesenchymal stem cells (BMSCs) were investigated using both direct culture and direct exposure culture methods. The adhesion density of BMSCs on ZC21 pins (i.e., direct contact) was significantly higher than on pure Mg pins in both in vitro culture methods; the cell adhesion density around ZC21 pins (i.e., indirect contact) was similar to the cell-only positive control in both in vitro culture methods. Interestingly, ZC21 showed a higher daily degradation rate, crack width and crack area ratio in the direct exposure culture than in the direct culture, suggesting different culture methods did affect its in vitro degradation behaviors. When cultured with Gram-positive bacteria methicillin-resistant Staphylococcus aureus (MRSA), ZC21 reduced bacterial adhesion on the surface more significantly than that of ZSr41 and Mg. The in vivo degradation and biocompatibility of the ZC21 pins for bone regeneration were studied in a mouse femoral defect model. The in vivo degradation rate of ZC21 pins was much slower than that of ZSr41 alloy and Mg control pins. After 12 weeks of implantation in vivo, the ZC21 group showed the shortest gap at the femoral defect, indicating that ZC21 pins promoted osteogenesis and bone healing more than ZSr41 and Mg control pins. Overall, the ZC21 alloy is promising for bone repair, while providing antibacterial activities, and should be further studied toward clinical translation.

High-temperature wear and frictional behavior of partially oxidized Al with NiCr composite coating

The influence of composite coating in improving wear and frictional behavior from room temperature to 600 °C was investigated. Partially oxidized Al powder was prepared with a flame spray process by spraying pure Al powder into distilled water. The composite powder is the mixture of 30 weight percent of partially oxidized Al and 70 weight percent of NiCr alloy powder. The composite powder was subsequently coated on MDN321 steel by air plasma spray process. The composite coatings are characterized with respect to adhesion strength, porosity, micro-hardness, and density. Wear and frictional behavior of coatings are evaluated under disc speed of 1 and 2 m s−1, loads of 10, 20 and 30 N and 3000 m sliding distance. The test results indicated that at room temperature, frictional heat generated due to applied load produce three-body abrasion at the interface caused to increase the wear and friction in the coating. The oxide film formed at high temperature due to plastic deformation avoids surface degradation at the interface and reduce the wear and friction. The worn surfaces at 600 °C consist phases of α-Al2O3, NiO, and Cr3O. These phases are contributing to improving the wear resistance of the coating more than 4-times compared to uncoated steels under varying load and sliding velocities. The coefficient of friction reduced with increase in temperature due to generated oxides act as lubricants at the interface.

Electrophoretic Deposition of Magnesium Oxide Nanoparticles on Magnesium: Processing Parameters, Microstructures, Degradation, and Cytocompatibility.

Magnesium (Mg) and its alloys are a class of promising materials for biodegradable orthopedic and craniomaxillofacial implants; however, rapid release of hydrogen gas remains a key challenge for clinical translation. This study reported the optimal parameters of electrophoretic deposition (EPD), at which magnesium oxide nanoparticles (nMgO) could be deposited onto Mg substrates with homogeneous surface morphology and elemental distribution. The results showed that the distribution and uniformity of the nMgO coatings on Mg improved when the nMgO concentration in ethanol increased and the time of applied voltage decreased. The nMgO-coated Mg showed a homogeneous surface and distinct degradation mode during the 9-day immersion studies in revised simulated body fluid (r-SBF) and Dulbecco's modified Eagle's medium (DMEM), when compared with the noncoated Mg controls. The nMgO coating initially mitigated hydrogen gas formation. The degradation layer on nMgO-coated Mg was thicker than the noncoated Mg and enriched with Ca and P that are favorable for skeletal implant applications. In the direct culture study with bone marrow derived mesenchymal stem cells (BMSCs) in vitro, the cell adhesion density and morphology were not affected by the solubilized degradation products released by the nMgO-coated Mg under indirect contact. However, at the cell-biomaterial interface, the cell spreading decreased under direct contact, possibly because of the continuous dynamic degradation of the samples. The electrophoretically deposited nMgO coatings on Mg-based medical implants should be further studied to improve the coating-substrate and cell-material interfaces for clinical applications.

Nanowall enclosed architecture infused by lubricant: A bio-inspired strategy for inhibiting bio-adhesion and bio-corrosion on stainless steel

Microbiologically influenced corrosion (MIC) severely deteriorates metal material in seawater environment. Finding versatile coatings to inhibit bioadhesion and biocorrosion is a critical option to avoid degradation by microorganisms. Inspired by Nepenthes pitcher, this study prepares lubricant-infused surface (LIS) by using a three-step method: electrodeposition, vapor deposition, and oil infusion. First, Co(OH)2 is built on stainless steel (SS) via electrodeposition. The wrinkled nanowall circumvents the partition architecture, thus producing a highly porous structure. Second, through dodecanethiol modification, the combination of anchored hydrophobic moiety and porous structure creates a lotus-inspired superhydrophobic (SHP) surface. Third, oil infusion produces LIS. The independent partition architecture increases the anchoring effect to oil phase, thereby enhancing the stability. After immersion for 28 days in an abiotic seawater environment, the corrosion current density of SS covered by LIS SS is as low as 2.52 × 10−10 A/cm2, which is approximately five orders of the magnitude lower than that of bare SS. After immersion in sulfate-reducing bacteria (SRB) suspension for 6 days, the cell adhesion density on LIS decreases by one order of magnitude compared with that on bare SS, thereby showing high bio-adhesion inhibition capability. The decrement of bacteria adhesion steadily decreases the MIC to SS. After exposure to SRB suspension for 10 days, the corrosion current density of LIS SS is only 1.06 × 10−8 A/cm2, which is lower than that of SHP coating under the same immersion periods. Therefore, the bio-inspired LIS for SS is a promising way to inhibit bioadhesion and biocorrosion in seawater environment.

Photo-assisted green synthesis of silver doped silk fibroin/carboxymethyl cellulose nanocomposite hydrogels for biomedical applications.

Silver nanoparticles (AgNPs) and regenerated silk fibroin (RSF) have recently attracted significant interests for their potential applications in preventing wound-related infections and in tissue engineering. Indeed, nano-silver has long been recognized as one of the most effective antimicrobial agents, and silk fibroin is well known for its capability of stimulating cell activities and facilitating tissue regeneration. In this study, a green synthesis approach was used to create a composite hydrogel (CoHy) of RSF stabilized with CarboxymethylCellulose-Na (CMC-Na) and loaded with AgNPs. Their swelling ratios were up to 59 g/g when tested in different physiologically relevant fluids. Material characterizations by Scanning electron microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), and X-Ray Diffraction (XRD) confirmed the presence of AgNPs on the surface. Antimicrobial properties of the CoHy samples were evaluated using agar diffusion tests. The results showed distinct inhibition zones against major microorganisms found in wound infections, including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis), Methicillin Resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa (P. aeruginosa), Candida albicans (C. albicans) and Fluconazole-resistant Candida albicans (FRCA). Cytocompatibility studies with rat bone marrow derived mesenchymal stem cells (BMSCs) in vitro showed that the adhesion density of BMScs on the CoHy loaded with 1 mg/mL was similar to the cell-only control group for the first 24 h of culture; moreover, higher cell proliferation was observed on the CoHy without AgNPs, indicating the regenerative potentials of the RSF/CMC composite hydrogels.

Impact of Antifouling PEG Layer on the Performance of Functional Peptides in Regulating Cell Behaviors.

Cell adhesive and other functional peptides (such as RGD, KRSR, YIGSR, VAPG, and BMP-2 peptides) are extensively studied and utilized in tissue engineering scaffolds and biomedical devices to modulate cell functions. Though PEG is frequently used as the antifouling layer, it is unclear how it affects the performance of functional peptides. By analyzing the impact of PEG at short (OEG4), medium (OEG8), and long chain length (PEG2K), we reveal that PEG chain length is critical and a medium-length PEG enables functional peptides to display their optimal and genuine functions in cell adhesion, migration, and differentiation by providing excellent antifouling to minimize background noise of unwanted cell adhesion and high enough surface density of functional peptides. Our result provides new avenues for maximizing the genuine functions of peptides. This study also provides a solution to prevent the heterogeneous and even divergent results caused by inappropriate choice of antifouling PEG and provides a general guidance in identifying new functional peptides.

Heparin inhibits lipopolysaccharide-induced adhesion of monocytes to endothelial cells

To investigate the effects of heparin on the secretion of monocyte chemotactic protein-1 (MCP-1) in human umbilical vein endothelial cells (HUVEC) and the adhesion of monocytes to endothelial cells stimulated by lipopolysaccharide (LPS). HUVEC were cultured in vitro, and the cells between generation 4 and 5 were used for the experiments. The cells were divided into phosphate buffer saline (PBS) control group, heparin control group, LPS group, and heparin+LPS group. The LPS group was challenged with LPS 10 mg/L; the PBS control group was added with the same amount of PBS; the heparin group was added with 10 kU/L unfractionated heparin; the heparin+LPS group was treated with 10 kU/L unfractionated heparin 15 minutes before LPS stimulation. The cells were harvested at 6 hours and 12 hours after LPS stimulation in each group, and the MCP-1 mRNA expression was determined by real-time fluorescent quantitative reverse transcription-polymerase chain reaction (qRT-PCR). After incubation with each group, the fluorescent dyelabeled human monocyte cell line THP-1 was cultured with each group for 1 hour in the dark, and the adhesion density of THP-1 and HUVEC was observed under fluorescence microscope. Compared with the PBS control group, the MCP-1 mRNA expression significantly increased at 6 hours and 12 hours after LPS stimulation and peaked at 6 hours, then decreased gradually, but remained significantly higher than the PBS control group at 12 hours [2-ΔΔCt: 16.41 (15.03, 18.00) vs. 1.00 (0.80, 1.26) at 6 hours, 9.27 (8.11, 9.85) vs. 1.00 (0.84, 1.20) at 12 hours, both P < 0.05]. Heparin preconditioning significantly reduced LPS-induced MCP-1 mRNA expression [2-ΔΔCt: 2.06 (1.72, 2.46) vs. 16.41 (15.03, 18.00) at 6 hours, 2.46 (2.19, 4.56) vs. 9.27 (8.11, 9.85) at 12 hours, both P < 0.05]. There was no significant difference in MCP-1 mRNA expression between the heparin control group and the PBS control group [2-ΔΔCt: 1.47 (1.29, 1.65) vs. 1.00 (0.80, 1.26) at 6 hours, 2.69 (2.58, 2.77) vs. 1.00 (0.84, 1.20) at 12 hours, both P > 0.05]. Fluorescence microscopy observation showed that LPS stimulation could promote the adhesion of THP-1 to HUVEC; heparin preconditioning could inhibit the adhesion of THP-1 to HUVEC stimulated by LPS. Heparin preconditioning could inhibit the MCP-1 mRNA expression , thereby reduce the adhesion of THP-1 to HUVEC, thus play a protective role in sepsis.

Mediating the Migration of Mesenchymal Stem Cells by Dynamically Changing the Density of Cell-selective Peptides Immobilized on β-Cyclodextrin-modified Cell-resisting Polymer Brushes

Dynamic control of mesenchymal stem cell (MSC) behaviors on biomaterial surface is critically involved in regulating the cell fate and tissue regeneration. Herein, a stimuli-responsive surface based on host-guest interaction with cell selectivity was developed to regulate migration of MSCs in situ by dynamic display of cell-specific peptides. Azobenzene-grafted MSC-affinitive peptides (EPLQLKM, Azo-E7) were grafted to β-cyclodextran (β-CD)-modified poly(2-hydroxyethyl methacrylate)-b-poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) (PHG) brushes, which were prepared by using surface-initiated atom transfer radical polymerization (SI-ATRP). X-ray photoelectron spectroscopy (XPS), quartz crystal microbalance (QCM), and water contact angle were used to characterize their structure and property. Cell adhesion assay showed that the combination effect of resisting property of PHG and MSC-affinity of E7 could promote the selective adhesion of MSCs over other types of cells such as RAW264.7 macrophages and NIH3T3 fibroblasts to some extent. UV-Vis spectroscopy proved that the competing guest molecules, amantadine hydrochloride (Ama), could release Azo-E7 peptides from the CD surface to different extents, and the effect was enhanced when UV irradiation was employed simultaneously. As a result, the decrease of cell adhesion density and migration rate could be achieved in situ. The cell density and migration rate could be reduced by over 40% by adding 20 μmol/L Ama, suggesting that this type of surface is a new platform for dynamic regulation of stem cell behaviors in situ.

A comparative study on the nanoindentation behavior, wear resistance and in vitro biocompatibility of SLM manufactured CP–Ti and EBM manufactured Ti64 gyroid scaffolds

The present study investigates the nanoindentation behavior, wear resistance and in vitro biocompatibility of SLM manufactured CP–Ti and EBM manufactured Ti64 gyroid scaffolds and the results were compared to those of casting CP–Ti. Both the SLM- and EBM manufactured scaffolds exhibited anisotropic properties with higher reduced modulus (up to 10%) and nanohardness (up to 30%) in the transverse direction than those in building direction. The wear resistance of scaffolds in transverse direction was higher than those of in building direction by up to ∼25% and ∼82% for SLM manufactured CP–Ti and EBM manufactured Ti64 scaffolds, respectively. The SLM manufactured CP–Ti scaffolds displayed significant enhancement in wear resistance over cast dense CP–Ti with 75% lower mean worn height during a nanowear test. The coefficient of friction was varied between 0.11 and 0.24 and exhibited a steady mean value of 0.15–0.18 for CP–Ti and Ti64 scaffolds, respectively. During in vitro cell culture study, CP–Ti scaffolds showed higher cell viability and cell adhesion density in comparison to Ti64 scaffolds for all unit cell sizes. Moreover, cell adhesion density of scaffolds with smaller unit cell sizes (G2) are lower than those of larger unit cells (G3). SEM observations confirmed that both the inner space and surfaces of gyroid scaffolds provided a suitable environment for cell migration, attachment and proliferation after cell culture for 7 d. Statement of significanceIt is essential to evaluate the properties of EBM/SLM manufactured scaffolds and to determine whether they can meet the tough performance requirements of the biomedical industry. In this study, nanoindentation and nanowear properties of SLM manufactured CP–Ti and EBM manufactured Ti64 gyroid scaffolds with different unit cell sizes and sample orientations were evaluated and compared to cast dense CP–Ti samples. Moreover, the in vitro biocompatibility of the scaffolds was assessed and compared to each other. To our best of knowledge, this type of study on EBM/SLM manufactured CP-Ti and Ti64 scaffolds have not been reported, to date.

Inside Cover: Label‐free multi‐parametric imaging of single cells: dual picosecond optoacoustic microscopy (J. Biophotonics 8/2019)

Sub‐picosecond light pulses are used to launch high‐frequency ultrasound in cells. The dual detection of acoustic echoes and of the time‐domain Brillouin scattering allows mapping remotely and in a single run experiment the cell adhesion, thickness, storage modulus and mass density, all with micron resolution. The dual picosecond opto‐acoustic microscope is demonstrated with the multiple imaging of a mitotic macrophage‐like cell. This novel modality is compatible with simultaneous fluorescence imaging.Further details can be found in the article by Liwang Liu, Laurent Plawinski, Marie‐Christine Durrieu, Bertrand Audoin (e201900045). image

Effect of electroplated interlayers on properties of cold-sprayed copper coatings on SS316L steel

Cold-sprayed copper (Cu) coatings have been recommended for the passivation of plasma-facing components in the vacuum vessel of Tokamaks. Therefore, research is under progress to develop such coatings with desired properties, which is still a challenging task. In the present work, the effect of nickel (Ni) and Cu electroplated interlayers on several properties of cold-spray copper coated SS316L steel was investigated. Further, the effect of heat-treatment on the developed coatings was also analyzed. The developed coatings were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), microhardness, nanoindentation, macro-tensile, and lap-shear test/ adhesion testing, and porosity, density and, electrical and thermal conductivity measurements. The novelty of the article includes the in-situ micro-tensile investigations performed under SEM to reveal the fracture phenomenon for the coatings. It was observed that the heat-treatment, in general, improves the coating properties. Additionally, gamma (γ)-ray and heavy nuclei irradiation and thermal cyclic tests were performed to elucidate the actual environmental performance of the coatings. Based on the overall results of the study, the heat-treated Cu-coating developed on Ni-electroplated steel substrate was found to be the most suitable material for protecting the plasma-facing components.