Magnesium (Mg) and its alloys are promising alternatives to conventionally used bioinert metals for bone repair due to their favorable biocompatibility and mechanical properties that closely mimic that of natural bone. However, Mg-based implants are limited by rapid corrosion in physiological environments, posing significant challenges such as premature implant failure, hydrogen gas accumulation and potential cytotoxicity. Calcium phosphate and ion-substituted coatings can not only enhance corrosion resistance of Mg-based implants by providing a barrier layer but also promote osseointegration and offer therapeutic functionality. These ceramic coatings, including hydroxyapatite and other substituted variations with strontium, zinc, silicon and silver offer further advantageous properties that can improve bone-implant integration and enhance antibacterial efficiency, leading to better patient outcomes. Advanced deposition techniques, including RF Magnetron sputtering and biomimetic immersion, enable precise control over coating properties and composition resulting in highly functionalized and tailored thin film coatings. This review discusses and evaluates various coating technologies and deposition techniques applicable to bone defect repair and implantation devices, with a focus on ceramic calcium phosphates and ion-substituted apatites, for the optimization of Mg-based implants towards clinic translation.

Cell mechanics, governed by cortical surface dynamics and cytoskeletal viscoelasticity, evolve throughout the cell cycle, influencing cellular function and behavior. Using multimodal microscopy-bimodal atomic force microscopy (AFM), force mapping, and load-rate analysis-we investigate mechanical differences between mitotic and interphase human corneal epithelial-transformed cells (HCE-T). Our quantitative analysis reveals significant variations in stiffness, viscosity, adhesion, and loading-rate responses, reflecting the frequency- and time-dependent properties of cytoskeletal networks and intracellular fluid dynamics. We show that mitotic cells exhibit reduced stiffness in dynamic tests due to intracellular softening and increased fluidity, while static tests highlight cortical stiffening driven by contractile forces. These findings emphasize the dynamic interplay between actin and microtubules in regulating cellular mechanics during division. By integrating high-resolution mechanical mapping with advanced analytical techniques, this study provides novel insights into cytoskeletal remodeling, offering a robust platform for studying mechano-transduction with applications in regenerative medicine and tissue engineering.

The rapid emergence of multidrug-resistant pathogens worldwide has raised concerns regarding the effectiveness of conventional antibiotics. This can be observed in ESKAPE pathogens, among others, whose multiple resistance mechanisms have led to a reduction in effective treatment options. Innovative strategies aimed at mitigating the incidence of antibiotic-resistant pathogens encompass the potential use of biosurfactants. These surface-active agents comprise a group of unique amphiphilic molecules of microbial origin that are capable of interacting with the lipidic components of microorganisms. Biosurfactant interactions with different surfaces can affect their hydrophobic properties and as a result, their ability to alter microorganisms’ adhesion abilities and consequent biofilm formation. Unlike synthetic surfactants, biosurfactants present low toxicity and high biodegradability and remain stable under temperature and pH extremes, making them potentially suitable for targeted use in medical and pharmaceutical applications. This review discusses the development of biosurfactants in biomedical and therapeutic uses as antimicrobial and antibiofilm agents, in addition to considering the potential synergistic effect of biosurfactants in combination with antibiotics. Furthermore, the anti-cancer and anti-viral potential of biosurfactants in relation to COVID-19 is also discussed.

The corrosion rate of Mg alloys is currently too high for viable resorbable implant applications. One possible solution is to coat the alloy with a hydroxyapatite (HA) layer to slow the corrosion and promote bone growth. As such coatings can be under severe stresses during implant insertion, we present a nano-mechanical and nano-tribological investigation of RF-sputtered HA films on AZ31 Mg alloy substrates. EDX and XRD analysis indicate that as-deposited coatings are amorphous and Ca-deficient whereas rapid thermal annealing results in c-axis orientation and near-stoichiometric composition. Analysis of the nanoindentation data using a thin film model shows that annealing increases the coating's intrinsic hardness (H) and strain at break (H/E) values, from 2.7 GPa to 9.4 GPa and from 0.043 to 0.079, respectively. In addition, despite being rougher, the annealed samples display better wear resistance; a sign that the rapid thermal annealing does not compromise their interfacial strength and that these systems have potential for resorbable bone implant applications.

Magnesium orthopaedic fracture fixation devices can potentially provide significant clinical benefits, such as the elimination of secondary surgeries for device removal due to in-vivo resorption and reduced stress shielding due to reduced device stiffness. However, development, approval, and clinical adoption of magnesium devices has been hindered by the excessively high rates of in-vivo corrosion such that the structural integrity of the device can be catastrophically reduced before fracture healing occurs. Coating of devices with calcium phosphate coatings has been shown to significantly reduce corrosion rates, while enhancing osseointegration. However, the adhesion strength between the CaP coatings and magnesium substrates has not been previously investigated. Clinical insertion of fracture fixation devices such as intramedullary nails and k-wires will impose significant shear loading on the coated surface of the implant. If the effective shear strength of the coating-device interface is not sufficiently high, the coating will be damaged and removed during device insertion. In the current study a bespoke experimental-computational approach is developed to provide a new understanding of the relationship between coating thickness, surface roughness, and effective shear strength of the CaP coating- Mg substrate interface. Nine test cases were created by adjusting either the deposition time (3 thickness values) or the surface treatment of the Mg alloy using SiC paper (3 roughness values) and double-lap shear testing was performed for these coating configurations. Strain development in the Mg substrates was monitored using strain gauges, and failure stress was determined for each configuration. Test results revealed that the effective shear strength of the coating-substrate interface is significantly higher for coatings on the rougher substrate surfaces when compared to those on smoother surfaces. Coating thickness was not found to significantly influence the effective shear strength over the range considered in this study (0.37-1.34 mu m). Micro-scale finite element models of lap-shear tests were constructed using experimental profilometry data. Simulations of rough coating-substrate interfaces reveal that significant localised compression occurs at the coating-substrate interface in regions of large asperities. A novel cohesive zone formulation has been developed to simulate compression induced shear hardening, and the resultant simulations are found to accurately predict the significantly higher effective shear strength measured experimentally for rougher coatings compared to smoother Mg substrate surfaces.

Tissue-engineered (TE) scaffolds provide an 'off-the-shelf' alternative to autograft procedures and can potentially address their associated complications and limitations. The properties of TE scaffolds do not always match the surrounding bone, often sacrificing porosity for improved compressive strength. Previously, the layer-by-layer (LbL) assembly technique was used to deposit nanoclay containing multilayers capable of improving the mechanical properties of open-cell structures without greatly affecting the porosity. However, the previous coatings studied contained poly(ethylenimine) (PEI), which is known to be cytotoxic due to the presence of amine groups, rendering it unsuitable for use in biomedical applications. In this work, poly(diallydimethylammonium chloride) (PDDA)- and chitosan (CHI)-based polyelectrolyte systems were investigated for the purpose of nanoclay addition as an alternative to PEI-based polyelectrolyte systems. Nanocomposite coatings comprising of PEI, poly(acrylic acid) (PAA), Na+ montmorillonite (NC), PDDA, CHI and sodium alginate (ALG) were fabricated. The coatings were deposited in the following manner: (PEI/PAA/PEI/NC), PEI-(PDDA/PAA/PDDA/NC) and (CHI/ALG/CHI/ALG). Results from scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses demonstrated that the nanoclay was successfully incorporated into each polymer bilayer system, creating a nanocomposite coating. Each coating was successful at tailoring the elastic modulus of the open-cell structures, with polyurethane foams exhibiting an increase from 0.15 ± 0.10 MPa when uncoated to 5.51 ± 0.40 MPa, 6.01 ± 0.36 MPa and 2.61 ± 0.41 MPa when coated with (PEI/PAA/PEI/NC), PEI-(PDDA/PAA/PDDA/NC) and (CHI/ALG/CHI/ALG), respectively. Several biological studies were conducted to determine the cytotoxicity of the coatings, including a resazurin reduction assay, scanning electron microscopy and fluorescent staining of the cell-seeded substrates. In this work, the PDDA-based system exhibited equivalent physical and mechanical properties to the PEI-based system and was significantly more biocompatible, making it a much more suitable alternative for biomaterial applications.

Gold nanoparticles (AuNPs) functionalized with polyethylene glycol (PEG) and peptide ligands are promising drug delivery vectors for use in cancer therapy. However, to control the interaction of the ligands with blood proteins and specific cell receptors, more needs to be known about the arrangement and properties of these grafted ligands. This issue is examined here principally with atomic force microscopy (AFM) for ligands grafted to both gold films and gold nanoparticles. Macro-level sessile drop measurements on the films indicate that, in dilute solutions, the PEG and peptide ligands exhibit similar affinity to the gold surface. However, at the nano-level, AFM experiments show differences in the morphology and cohesion of the adsorbed ligand films. Differences in tip/surface adhesion are also measured, indicative of variations of hydrophilicity for the top surface of these ligand films. Analysis of force-separation curves suggests a low packing density of PEG ligands. AFM investigations of functionalized AuNPs shows that the ligands improve dispersion and modify the tip/surface adhesion behaviour on the nanoparticles. However, AFM images of as-synthesised citric-capped and functionalized AuNPs gave similar nanoparticle diameters. Analysis of the AFM tip tapping on the AuNPs suggests that Tapping-AFM is not suitable for detection of low packing density ligands.

Scanning Kelvin probe microscopy was used to investigate the evolution of the Ni-BaTiO3 interfacial potential barriers in multilayer ceramic capacitors degraded by the highly accelerated life test method. We detect electric field discontinuities at such interfaces, which through analysis of the expected band diagrams, are associated with the presence of Schottky barriers. The decrease of discontinuities at the cathode in degraded capacitors denotes barrier lowering, indicative of a transition from Schottky to Ohmic contact, validating the proposed mechanism of oxygen vacancies electromigration being at the origin of insulation resistance degradation. Extrapolation of the depletion layer width is consistent with previous observations, and the possibility toward the use of this technique to obtain quantitative information is discussed.

Magnesium (Mg) alloys have significant potential for use as bioresorbable orthopaedic implant devices due to their controllable mechanical properties and an ability to promote new bone growth. However, difficulty lies with controlling the rate of corrosion in physiological conditions to ensure the load-bearing capability of the device is maintained for the required period of time, specifically until an adequate quantity of new bone tissue is formed. In this work, RF magnetron sputtering has been used to create calcium phosphate (CaP) and strontium-substituted calcium phosphate (SrCaP) thin film coatings on two Mg alloy systems (denoted WJK and ZEWX) that have been formulated for the fabrication of orthopaedic fracture fixation devices. A 14-day static-dynamic immersion study in simulated body fluid (SBF), shows that uncoated WJK substrates had a corrosion rate of 4.04 +/- 0.15 millimetres per year (mmpy), which was reduced to 3.22 +/- 0.17 mmpy with the application of a CaP coating, and to 2.92 +/- 0.05 mmpy with a SrCaP coating. Uncoated ZEWX substrates had a corrosion rate of 3.36 +/- 0.05 mmpy which was reduced to 2.98 +/- 0.19 mmpy and 2.79 +/- 0.03 mmpy, for CaP and SrCaP coatings, respectively. Whereas the sputter-deposited CaP and SrCaP coatings completely dissolve in SBF over the period of immersion, their presence at the outset significantly decreases the corrosion rate of both Mg alloys, as compared to the values for the uncoated substrates. Successful incorporation of Sr within the coating offers the potential for improved bioactivity with respect to directing the bone cell response to create new tissue.

One current strategy to deal with the serious issue of antibiotic resistance is to use biosurfactants, weak antimicrobials in their own right, with antibiotics in order to extend the efficacy of antibiotics. Although an adjuvant effect has been observed, the underlying mechanisms are poorly understood. To investigate the nature of the antibiotic and biosurfactant interaction, we undertook a scanning electron microscopy (SEM) and atomic force microscopy (AFM) microscopic study of the effects of the tetracycline antibiotic, combined with sophorolipid and rhamnolipid biosurfactants, on Methicillin-resistantStaphylococcus aureususing tetracycline concentrations below and above the minimum inhibitory concentration (MIC). Control and treated bacterial samples were prepared with an immersion technique by adsorbing the bacteria onto glass substrates grafted with the poly-cationic polymer polyethyleneimine. Bacterial surface morphology, hydrophobic and hydrophilic surface characters as well as the local bacterial cell stiffness were measured following combined antibiotic and biosurfactant treatment. The sophorolipid biosurfactant stands alone insofar as, when used with the antibiotic at sub-MIC concentration, it resulted in bacterial morphological changes, larger diameters (from 758 +/- 75 to 1276 +/- 220 nm,p-value = 10(-4)) as well as increased bacterial core stiffness (from 205 +/- 46 to 396 +/- 66 mN/m,p-value = 5 x 10(-5)). This investigation demonstrates that such combination of microscopic analysis can give useful information which could complement biological assays to understand the mechanisms of synergy between antibiotics and bioactive molecules such as biosurfactants.

Atomic force microscopy (AFM) is a powerful technique for accurate, reliable and non-destructive imaging and characterization of materials at the nanoscale. Among the numerous AFM methods, amplitude modulation or tapping mode AFM (AM-AFM) is an established method for imaging and characterization for most commercial AFM systems. Despite its high spatial resolution and sensitivity, quantitative characterization by AM-AFM lag behind other advanced AFM methods as far as quantification of materials properties is concerned. In this paper a fully analytical multiparametric approach for AM-AFM is proposed which simultaneously quantifies the Hamaker constant and viscoelastic properties of materials. The main advantage of the proposed method lies in the inclusion of adhesion to calculate viscoelasticity, which makes it superior to the current equations used in the AFM community. The accuracy of the proposed method is validated by several simulations and experiments and comparison with nanoindentation results, which strongly support its candidacy as a method of choice for material properties quantification by dynamic AFM.

The unique ability of Atomic Force Microscopy (AFM) to image, manipulate and characterize materials at the nanoscale has made it a remarkable tool in nanotechnology. In dynamic AFM, acquisition and processing of the photodetector signal originating from probe-sample interaction is a critical step in data analysis and measurements. However, details of such interaction including its nonlinearity and dynamics of the sample surface are limited due to the ultimately bounded bandwidth and limited time scales of data processing electronics of standard AFM. Similarly, transient details of the AFM probe's cantilever signal are lost due to averaging of data by techniques which correlate the frequency spectrum of the captured data with a temporally invariant physical system. Here, we introduce a fundamentally new approach for dynamic AFM data acquisition and imaging based on applying the wavelet transform on the data stream from the photodetector. This approach provides the opportunity for exploration of the transient response of the cantilever, analysis and imaging of the dynamics of amplitude and phase of the signals captured from the photodetector. Furthermore, it can be used for the control of AFM which would yield increased imaging speed. Hence the proposed method opens a pathway for high-speed transient force microscopy.

In this study, the effect of fibre sizing on the modification of basalt fibres in preparation for use with a polypropylene matrix (PP) was investigated. Fibres were coated by the manufacturer with a standard available epoxy (EP) sizing and four experimental PP focused sizings (PPs1-4). Fibre with no sizing was produced to act as a control. The surface topography of sized fibre was analysed by SEM and AFM, indicating that PP sized fibres displayed a more inhomogeneous coating of the fibre. Furthermore, PP sizing resulted in an increase in AFM measured roughness by similar to 360%, translating to a 12.5% increase in surface area, over both unsized and EP fibres. Scratching of the fibre surface revealed, that in general, the coating thickness of PP was similar to 30 nm thicker than EP sizing despite the same application parameters. XPS revealed that the sizing in all cases adhered to the fibre surface with an increase in potential reactive sites present on PP sized fibres. Analysis of fibre surface energy showed that the overall surface energy of fibres remained similar but the use of PP focused sizing resulted in a decrease of the polar component. Overall, this investigation shows that sizing has a significant effect on the fibre's surface: changing its topography and chemistry and hence, has an evident potential for increased mechanical and chemical bonding. This was further confirmed by single fibre fragmentation testing which highlighted that sizings PPs2-4 increase the interfacial shear strength by up to 117% compared to non-sized fibres.

The focus of this study was to investigate the potential of short basalt fibre (BF) as reinforcement for polypropylene (PP) and the effect fibre sizing has on adhesion and resultant mechanical properties. Short fibre PP composites were manufactured at fibre loadings of 10, 20 and 30 wt% using fibres coated in multi-purpose epoxy based sizing and four experimental PP tailored sizings. SEM image analysis of polished composite cross-sections showed. that dispersion was independent of what matrix the fibre sizing was designed for. Fibre length distribution showed the final fibre length of BF was larger than glass fibres in PP composites, which is attributed to its higher abrasive resistance. DSC revealed in general basalt does not influence the crystallinity of PP but some sizings resulted in a 2-3%increase, however, BF increases onset crystallisation temperature by similar to 3 degrees C. Tensile and flexural properties of PP can be significantly increased by up to 64% (tensile strength) and 110% (tensile modulus) through the addition of short BF with properties increasing as fibre content increases; however the impact strength simultaneously decreases. Mechanical properties were highly dependent on fibre sizing, where fibres indicating good adhesion provided the greatest increase in tensile and flexural strength but resulted in lower impact strength. Analysis of the fibre-matrix interface highlighted the significant effect sizing has on interfacial shear strength where improvements of 117% were evident. This study highlights the potential of BF as an effective reinforcement for PP while enforcing the importance and advancements of fibre sizing on promotion of adhesion.

We investigated the chemical, mechanical and geometrical properties of basalt fibers from three different commercial manufacturers and compared the results with those from an industry standard glass fiber. The chemical composition of the fibers was investigated by X-ray fluorescence spectrometry, which showed that basalt and glass fibers have a similar elemental composition, with the main difference being variations in the concentrations of primary elements. A significant correlation between the ceramic content of basalt and its tensile properties was demonstrated, with a primary dependence on the Al2O3 content. Single fiber tensile tests at various lengths and two-way ANOVA revealed that the tensile strength and modulus were highly dependent on fiber length, with a minor dependence on the manufacturer. The results showed that basalt has a higher tensile strength, but a comparable modulus, to E-Glass. Considerable improvements in the quality of manufacturing basalt fibers over a three-year period were demonstrated through geometrical analysis, showing a reduction in the standard deviation of the fiber diameter from 1.33 to 0.61, comparable with that of glass fibers at 0.67. Testing of single basalt fibers with diameters of 13 and 17 µm indicated that the tensile strength and modulus were independent of diameter after an improvement in the consistency of fiber diameter, in line with that of glass fibers.

Control of the corrosion that occurs in magnesium alloys in vivo is a significant challenge for their use as resorbable orthopaedic implants. In this work, we report on the provision of bioactive calcium phosphate (CaP) coatings on magnesium alloys that can delay substrate corrosion while offering an attendant physiochemical environment with properties known to promote an osteoinductive response in vivo. RF magnetron sputtering from hydroxyapatite (HA) powder targets has been employed to create CaP coatings on AZ31 magnesium alloy substrates. Coatings of similar to 70 and 210 nm thickness were achieved via regulation of sputtering parameters, in particular deposition time. XPS and ToF-SIMS were used to investigate the chemistry of the coating alloy interface and also to confirm composition and thickness. The Ca/P atomic ratio of the coatings was determined by EDX to be 1.54. mu CT analysis showed a substrate volume loss after 14 days exposure to SBF of 5.89 +/- 3.15 mm(3) for the un-coated alloy while the presence of the similar to 70 nm CaP coating reduced this to 3.42 +/- 0.48 mm(3) and the similar to 210 nm coating to 0.30 +/- 0.28 mm(3). The corrosion rates were calculated to be 1.74 +/- 0.06 mmpy for the AZ31 control; 1.57 +/- 0.09 mmpy for the similar to 70 nm CaP coated alloy and 1.01 +/- 0.07 mmpy for the similar to 210 nm CaP coating. This data confirms that CaP coating thickness can control the rate of corrosion of magnesium alloys while offering the potential for improved bioactivity.

A comparative study on conventional drilling and helical milling has been reported under the context of aircraft alloy hole making. The impacts of these two different machining processes on the microstructures and the fatigue performance of different aircraft alloys have been elaborated. Results show that both alloys undergo more severe surface/subsurface plastic deformation under conventional drilling comparing to helical milling process. Helical milling leads to a longer coupon fatigue life compared to conventional drilling for both alloys. The fatigue life of Al 2024-T3 is significantly longer than that of Ti-6Al-4V under all machining conditions. The use of coolant generally produces less damaged surface and leads to enhanced fatigue performance of the machined alloys. In addition, the machined surface roughness has been studied to further elaborate the effects of different machining processes.

Polyamide 6 (PA6)/graphene oxide (GO) nanocomposites were prepared via in situ, ring opening polymerization of e-caprolactam in the presence of both dried powder and colloidally dispersed single layer GO. Characterization of the composites and GO (both as received and after removal from the composites) was carried out using atomic force microscopy (AFM), Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis, differential scanning calorimetry and tensile testing. Reduction in the GO during polymerization was observed. So too was functionalization of the GO flakes with PA6 chains. FTIR demonstrates the retention of some carbonyl oxygen functionalities after polymerization. AFM imaging indicated the presence of single layer GO and the sheet height increased to similar to 4 nm for graphene sheets after polymerization. This suggests the graphene acts as a base for polymer chain formation, leading to good interfacial interaction between the filler and matrix. Raman data show no evidence of the restoration of sp2 hybrid as a result of polymerization. The nanocomposites are thermally stable while molecular weight and crystallinity have both been affected by GO inclusion. A percentage linear increase in Young's modulus was observed as colloidally dispersed GO content increased. (C) 2015 Society of Plastics Engineers

Predicting how proteins fold and adsorb onto surfaces is a complex problem of strong relevance to the health and environmental sectors. In this work, two nano-patterning techniques, namely focused ion beam (FIB) milling and atomic force microscopy (AFM) nanoindentation were used to develop hydrogenated amorphous carbon (a-C:H) model surfaces with similar nano-topography but different local composition. On the un-patterned surfaces, bovine plasma fibrinogen (BPF) resulted in a thicker and rougher adsorbed film than bovine serum albumin (BSA), although FTIR analysis indicated that, the secondary structure of the proteins changed similarly, with an increase of the β-sheet component (+27% and+34% for BSA and BPF, respectively). AFM analysis on the FIB-patterned surfaces indicates that patterning can modify specific protein adsorption behaviors. Moreover, the patterns were compared by imaging the AFM tip/surface adhesive force for BSA adsorbed on either AFM tips or patterned surfaces. The results show an electrostatic interaction between the implanted Ga+ and BSA surface, modifying the adsorption behavior and the adhesive force. Modelling this interaction gave an estimate of the surface charge per protein, a significantly lower value than in dilute solution (−1.8e instead of -18e). This finding is indicative of protein misfolding, as detected in the FTIR analysis.

Titania nanostructures have been prepared by anodisation in aqueous solution assisted by focused ion beam (FIB) milling. The structures formed are bi-periodic, a disordered “native” nanotube array, with characteristics similar to those formed by the standard anodisation process and an ordered array of tubes with larger diameters, guided by the positioning of the FIB concave pits. Low kV EDX analysis shows implanted Ga in FIB-treated titanium which is efficiently removed by the anodisation process. Following thermal annealing, the FIB-treated regions also crystallise to the same anatase phase as the native regions. This result is in stark contrast to previous FIB-assisted anodisation studies which only produced nanostructured arrays of native dimensions. This singularity is discussed in terms of the stable FIB-induced crystalline defects which, in an aqueous electrolyte, can result in the growth of a weaker barrier layer and larger tubes. This novel process gave hexagonal and square arrays with tailored cross-sectional dimensions and therefore has potential for the synthesis of novel meta-materials.