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The recently emerged coronavirus pandemic (COVID-19) has become a worldwide threat affecting millions of people, causing respiratory system related problems that can end up with extremely serious consequences. As the infection rate rises significantly and this is followed by a dramatic increase in mortality, the whole world is struggling to accommodate change and is trying to adapt to new conditions. While a significant amount of effort is focused on developing a vaccine in order to make a game-changing anti-COVID-19 breakthrough, novel coronavirus (SARS-CoV-2) is also developing mutations rapidly as it transmits just like any other virus and there is always a substantial chance of the invented antibodies becoming ineffective as a function of time, thus failing to inhibit virus-to-cell binding efficiency as the spiked protein keeps evolving. Hence, controlling the transmission of the virus is crucial. Therefore, this review summarizes the viability of coronaviruses on inanimate surfaces under different conditions while addressing the current state of known chemical disinfectants for deactivation of the coronaviruses. The review attempts to bring together a wide spectrum of surface–virus–cleaning agent interactions to help identify material selection for inanimate surfaces that have frequent human contact and cleaning procedures for effective prevention of COVID-19 transmission.

This issue of Interface Focus is a collection of papers on ‘The biomedical applications of graphene’. The idea to put together this theme issue evolved during discussions between Prof. Peter N.T. Wells CBE, FREng, FMedSci, FRS and myself in mid-2016. Very sadly, about a year ago, Prof. Wells passed away. However, before that and even in the various last stages of his life he was intensely involved in planning this theme issue with me. I am deeply indebted to him for his contributions towards this and I dedicate this theme issue to him as a memorial.

Co-axial electrohydrodynamic atomization was used to prepare core/shell polymethylsilsesquioxane particles for co-delivery of metformin and glibenclamide in a sustained release manner. The drug-loaded microparticles were mostly spherical and uniformly distributed in size, with average diameters between 3 and 5 µm across various batches. FTIR was used to confirm the presence of drugs within the particles while X-ray diffraction studies revealed drugs encapsulated existed predominantly in the amorphous state. Intended as systems that potentially can act as depot formulations for long-term release of antidiabetics, a detailed analysis of drug release from these particles was necessary. Drugs of different solubilities were selected in order to study the effects of drug solubility from a core/shell particle system. Further analyses to determine how conditions such as release into a limited volume of media, sampling rate and partitioning of drug between the core and shell layers influenced drug release were conducted by comparing experimental and mathematically modelled outcomes. It was found that while the solubility of drug may affect release from such systems, rate of removal of drug (sampling frequency) which upsets local equilibrium at the particle/solution interface prompting a rapid release to redress the equilibrium influenced release more.

A novel class of ultra-thin fibres, which affect microbial growth, were explored. The microbial properties of poly(methyl methacrylate) fibres containing 2, 4 and 8 wt% of graphene nanoplatelets (GNPs) were studied. GNPs were dispersed in a polymeric solution and processed using pressurized gyration. Electron microscopy was used to characterize GNP and fibre morphology. Scanning electron microscopy revealed the formation of beaded porous fibres. GNP concentration was found to dictate fibre morphology. As the GNP concentration increased, the average fibre diameter increased from 0.75 to 2.71 µm, while fibre porosity decreased. Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa were used to investigate the properties of 2, 4 and 8 wt% GNP-loaded fibres. GNP-loaded fibres (0 wt%) were used as the negative control. The fibres were incubated for 24 h with the bacteria; bacterial colony-forming units were enumerated by adopting the colony-counting method. The presence of 2 and 4 wt% GNP-loaded fibres promoted microbial growth, while 8 wt% GNP-loaded fibres showed antimicrobial activity. These results indicate that the minimum inhibitory concentration of GNPs required within a fibre is 8 wt%.

Spark plasma sintering has been used for the first time to prepare the ASTM F75 cobalt–chromium–molybdenum (Co–Cr–Mo) orthopaedic alloy composition using nanopowders. In the preliminary work presented in this report, the effect of processing variables on the structural features of the alloy (phases present, grain size and microstructure) has been investigated. Specimens of greater than 99.5 per cent theoretical density were obtained. Carbide phases were not detected in the microstructure but oxides were present. However, harder materials with finer grains were produced, compared with the commonly used cast/wrought processing methods, probably because of the presence of oxides in the microstructure.

The gradation of porosity in a biomaterial can be very useful for a variety of medical engineering applications such as filtration, bone replacement and implant development. However, the preparation of such structures is not a technologically trivial task and replication methods do not offer an easy solution. In this work, we elucidate the preparation of structures having a graded porosity by electrohydrodynamic spraying, using zirconia (ZrO 2 ), which is widely used in biomedical and other applications. The processes are generic and can be achieved using other bioactive ceramics with similar particle characteristics. The pores on the sprayed surface, the innermost surface and lengthwise cross sections have been analysed in addition to the change in depth of penetration as a function of spraying time. Control of porosity, pore size and depth of penetration has been obtained by varying parameters such as the spraying time, sintering temperature and the sacrificial template. It has been possible to obtain structures with interconnected pore networks of pore size greater than 100 μm as well as scattered pores smaller than 10 μm in size.

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.

Microspheres are potential candidates for the protein drug delivery. In this work, we prepared polymer-coated starch/bovine serum albumin (BSA) microspheres using co-axial electrohydrodynamic atomization (CEHDA). First, starch solution in dimethyl sulphoxide (DMSO) was prepared and then an aqueous solution of BSA was added to it to make a starch–BSA solution. Subsequently, this solution was made to flow through the inner capillary, while the polymer, polydimethylsiloxane (PDMS), flowed through the outer capillary. On collection, filtration and subsequent drying, near-monodisperse microspheres of 5–6 μm in size were obtained. The microspheres were characterized by Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy. Cumulative BSA release was investigated by UV spectroscopy. BSA structure and activity was preserved in the microspheres and its release in 0.01 M phosphate buffered saline (PBS) was studied over a period of 8 days. There was an initial burst with 32 wt% of total BSA released in 2 h. Overall 75 wt% of BSA was released over a 7 day period.

A polysilane (PS) has been modified chemically with aluminium acetylacetonate (AlAce) to prepare new Si‐Al‐C‐O precursors. Chemical reactions occur between PS and AlAce and this gives rise to higher pyrolysis yields from the precursors at 900°C in nitrogen, compared with that of PS, due to network formation by crosslinking. Further pyrolysis of the precursors to 1700°C in nitrogen produces ceramics of the SiC‐AlN system with composition dependent on the AlAce/PS ratio. The structures of the precursors and their pyrolysis products have been characterized and the influence of the AlAce/PS ratio has been elucidated.

Ceramic ink droplets have been deposited on two fundamentally different types of substrate and the evolution of contact angle, width of the ink–substrate interface and droplet height was measured as a function of time from digital images of the droplet captured on video. On substrate type I, with a lower surface free energy than the surface tension of the ceramic ink, after reaching stability in a few seconds, the contact angle decreased and the width of the ink–substrate interface remained stationary. Subsequently, the contact angle stayed constant and thereafter reduced again, while the width of the ink–substrate interface decreased and remained constant thereafter. On substrate type II, with a higher surface free energy than the surface tension of the ceramic ink, stability was achieved instantaneously and the contact angle decreased rapidly, while the width of the ink–substrate interface increased initially but thereafter remained constant. The corresponding variation of droplet height due to spreading and evaporation, and volume shrinkage rate were also found to be much faster on the type–II substrate.

Owing to the rapid movements of the human upper eyelid, a high-speed camera was used to record and characterize voluntary blinking and the blink dynamics of blepharoptosis patients were compared to a control group. Twenty-six blepharoptosis patients prior to surgery and 45 control subjects were studied and the vertical height of the palpebral aperture (PA) was measured manually at 2 ms intervals during each blink cycle. The PA and blinking speed were plotted with respect to time and a predictive model was generated. The blink dynamic was analysed in closing and opening phases, and revealed a reduced speed of the initial opening phase in ptotic patients, suggesting intrinsic muscle function change in ptosis pathogenesis. The PA versus time curve for each subject was reconstructed using custom-built parameters; however, there were significant differences between the two groups. Those parameters used included the rate of closure, the delay between opening and closing, rate of initial opening, rate of slow opening (nonlinear function) and the ‘switch point’ between those two rates of opening. The model was tested against a new group of subjects and was able to discriminate ptosis patients from controls with 80% accuracy.

In this investigation, biodegradable polycaprolactone polymeric particles (300–4500 nm in diameter) were prepared by jetting a solution in an electric field. An extensive study has been carried out to determine how the size and size distribution of the particles generated can be controlled by systematically varying the polymer concentration in solution (and thereby its viscosity and electrical conductivity), and also the selected flow rate (2–50 µl min −1 ) and applied voltage (0–15 kV) during particle generation. Change in these parameters affects the mode of jetting, and within the stable cone-jet mode window, an increase in the applied voltage (approx. 15 kV) resulted in a reduction in particle size and this was more pronounced at high flow rates (such as; 30, 40 and 50 µl min −1 ) in the same region. The carrier particles were more polydisperse at the peripheral regions of the stable cone-jet mode, as defined in the applied voltage-flow rate parametric map. The effect of loading a drug on the particle size, size distribution and encapsulation efficiency was also studied. Release from drug-loaded particles was investigated using UV spectrophotometry over 45 days. This work demonstrates a powerful method of generating drug-loaded polymeric particles, with the ability to control size and polydispersivity, which has great potential in several categories of biotechnology requiring carrier particles, such as drug delivery and gene therapy.

Bioactive hydroxyapatite (HA) with addition of silicon (Si) in the crystal structure (silicon-doped hydroxyapatite (SiHA)) has become a highly attractive alternative to conventional HA in bone replacement owing to the significant improvement in the in vivo bioactivity and osteoconductivity. Nanometre-scaled SiHA (nanoSiHA), which closely resembles the size of bone mineral, has been synthesized in this study. Thus, the silicon addition provides an extra chemical cue to stimulate and enhance bone formation for new generation coatings, and the next stage in metallic implantation design is to further improve cellular adhesion and proliferation by control of cell alignment. Topography has been found to provide a powerful set of signals for cells and form contact guidance. Using the recently developed novel technique of template-assisted electrohydrodynamic atomization (TAEA), patterns of pillars and tracks of various dimensions of nanoSiHA were achieved. Modifying the parameters of TAEA, the resolution of pattern structures was controlled, enabling the topography of a substrate to be modified accordingly. Spray time, flow rate and distance between the needle and substrate were varied to improve the pattern formation of pillars and tracks. The 15 min deposition time provided the most consistent patterned topography with a distance of 50 mm and flow rate of 4 µl min −1 . A titanium substrate was patterned with pillars and tracks of varying widths, line lengths and distances under the optimized TAEA processing condition. A fast bone-like apatite formation rate was found on nanoSiHA after immersion in simulated body fluid, thus demonstrating its high in vitro bioactivity. Primary human osteoblast (HOB) cells responded to SiHA patterns by stretching of the filopodia between track and pillar, attaching to the apex of the pillar pattern and stretching between two. HOB cells responded to the track pattern by elongating along and between the track, and the length of HOB cells was proportional to the gaps between track patterns, but this relationship was not observed on the pillar patterns. The study has therefore provided an insight for future design of next generation implant surfaces to control and guide cellular responses, while TAEA patterning provides a controllable technique to provide topography to medical implants.

Surface topography is well known to play a crucial role in influencing cellular responses to an implant material and is therefore important in bone tissue regeneration. A novel jet-based patterning technique, template-assisted electrohydrodynamic atomization spraying, was recently devised to control precisely the surface structure as well as its dimensions. In the present study, a detailed investigation of this patterning process was carried out. A range of nano-hydroxyapatite (nHA) line-shaped patterns In vitrostudies showed that the nHA patterns generated are capable of regulating the human osteoblast cell attachment and orientation.

The origin of defects in moulded ceramic bodies during pyrolytic removal of the organic vehicle is predicted. The kinetics of thermal degradation of the polymer are combined with a nonlinear, numerical model for the unsteady-state diffusion of degradation products in solution in the parent polymer. The resulting centre concentration of monomer in an infinite cylinder is used to predict the incidence of boiling which results in the formation of internal defects in the ceramic body. The calculation, which incorporates the concentration dependence of the diffusion coefficient based on free volume theory, reveals the outcome of the competition between degradation and diffusion and thus allows the influence of material, geometric and process variables to be explored.

In this short communication, we describe the scope and flexibility of using a novel device containing three coaxially arranged needles to form a variety of novel morphologies. Different combinations of materials are subjected to controlled flow through the device under the influence of an applied electric field. The resulting electrohydrodynamic flow allows us to prepare double-layered bubbles, porous encapsulated threads and nanocapsules containing three layers. The ability to process such multilayered structures is very significant for biomedical engineering applications, for example, generating capsules for drug delivery, which can provide multistage controlled release.