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An introduction is presented in which the editors discuss reports within the issue on topics dedicated to the characterization of thin films and membranes.

Abstract There is a growing interest in the design and engineering of operational biofuel cells that can be implanted. This review highlights the recent progress in the electrochemistry of biofuel cell technologies, but with a particular emphasis on the medical and physiological aspects that impact the biocompatibility of biofuel cells operating inside a living body. We discuss the challenge of supplying power to implantable medical devices, with regard to the limitations of lithium battery technology and why implantable biofuel cells can be a promising alternative to provide the levels of power required for medical devices. In addition to the challenge of designing a biofuel cell that provides a stable level of sufficient power, the review highlights the biocompatibility and biofouling problems of implanting a biofuel cell that have a major impact on the availability of the substrates inside body that provide fuel for the biofuel cell. These physiological challenges and associated ethical considerations are essential to consider for biofuel cells that are designed to be implanted for long-term operation inside a living animal and eventually to human clinical applications. Highlights • Implanted biofuel cells (BFCs) have both electrochemical and biocompatibility needs. • Electrochemistry progress gives function of implanted BFC for several months. • Electrochemical challenges remain to optimise bioelectrode surface area and volume. • Biocompatibility challenges need to be overcome for long-term function in mammals. • Insight into optimising electrochemical and biocompatibility challenges is presented. [ABSTRACT FROM AUTHOR]

The author discusses the importance of interfaces for sensing and the significance of their impact for the biological sciences and biomedicine. It is asserted that biosensors have provided notable examples of new interfacial processes. Sensor research is said to have led to the establishment of methods of integrating different interactive phases that combine to create the eventual device, thus leading to a refinement of interfaces.

[Display omitted] • P(NIPAAm-co-NVP) copolymer was successfully tethered to platinum paste electrodes. • Temperature addressable permeability change to H 2 O 2 and K 3 [Fe(CN) 6 ] was demonstrated. • Increased NVP content deduced high LCST to allow self-cleaning at body temperature. • Surface conformational remodeling was important for protein rejection. Electrochemical sensors have progressively become important tools for monitoring the concentration of complex substances in biological media. However, surface fouling and biological contamination from bio-colloids have not been effectively resolved. In this study, a self-cleaning electrochemical sensor was constructed where a thermoresponsive outer polymer layer was equipped to repel the absorbent proteins. Enhanced hydrophilic P(NIPAAm-co-NVP) copolymers bearing N-isopropylacrylamide (NIPAAm) and N-vinyl pyrrolidone (NVP) were synthesized by free radical polymerization, and the resulting thermoresponsive polymeric films were drop coated on screen-printed platinum electrodes (SPPEs) followed by thermal annealing. Grafting density, surface wettability, surface microstructure, amperometric response, electrochemical active surface area (EAS) and other performances, were evaluated for the modified SPPEs. Self-cleaning behavior after albumin adsorption was assessed by cyclic voltammetry (CV) and scanning electron microscopy (SEM) using various set temperatures respectively. The results showed the lower critical solution temperature (LCST) varied from 25 °C to 40 °C for P(NIPAAm-co-NVP) copolymers with the NVP content ranging from 0 to 47.62%. It indicated that NVP enhanced film hydrophilicity and could raise the LCST to above physiological data. The thermosensitivity, stability and repeatability of the modified sensors was proved to be well, and the unchanged selectivity was consistent with bare platinum electrodes. The copolymer film modified SPPEs showed the decreased and temperature-dependent EAS compared with bare SPPEs. It was concluded that films without NVP or with low NVP content resisted protein adsorption over lower temperatures, whilst with higher NVP content outstanding self-cleaning ability was also seen at physiological temperature. This opens the way to realize smart thermally addressable sensors able to solve the existing problem of biological surface contamination in sensor systems, and provides a strong model basis and technical capability for achieving novel, low drift electrochemical sensors. [ABSTRACT FROM AUTHOR]

While microfluidics promises much for streamlining biological assays, the problem of sample deposition must first be solved. [Copyright &y& Elsevier]

In this work, the enzyme aldehyde reductase, also known as aldose reductase, was synthesized and cloned from a human gene. Spectrophotometric measurements show that in presence of the nicotinamide adenine dinucleotide phosphate cofactor (NADPH), the aldehyde reductase catalyzed the reduction of glucose to sorbitol. Electrochemical measurements performed on an electrodeposited poly(methylene green)-modified gold electrode showed that in the presence of the enzyme aldehyde reductase, the electrocatalytic oxidation current of NADPH decreased drastically after the addition of glucose. These results demonstrate that aldehyde reductase is an enzyme that allows the construction of an efficient electrochemical glucose biosensor based on glucose reduction. [ABSTRACT FROM AUTHOR]

Jet lag has potentially serious deleterious effects on performance in athletes following transmeridian travel, where time zones are crossed eastwards or westwards; as such, travel causes specific effects related to desynchronization of the athlete's internal body clock or circadian clock. Athletes are particularly sensitive to the effects ofjet lag, as many intrinsic aspects of sporting performance show a circadian rhythm, and optimum competitive results require all aspects of the athlete's mind and body to be working in tandem at their peak efficiency. International competition often requires transmeridian travel, and competition timings cannot be adjusted to suit individual athletes. It is therefore in the interest of the individual athlete and team to understand the effects of jet lag and the potential adaptation strategies that can be adopted. In this review, we describe the underlying genetic and physiological mechanisms controlling the circadian clock and its inherent ability to adapt to external conditions on a daily basis. We then examine the fundamentals of the various adaptation stimuli, such as light, chronobiotics (e.g. melatonin), exercise, and diet and meal timing, with particular emphasis on their suitability as strategies for competing athletes on the international circuit. These stimuli can be artificially manipulated to produce phase shifts in the circadian rhythm to promote adaptation in the optimum direction, but care must be taken to apply them at the correct time and dose, as the effects produced on the circadian rhythm follow a phase-response curve, with pronounced shifts in direction at different times. Light is the strongest realigning stimulus and careful timing of light exposure and avoidance can promote adjustment. Chronobiotics such as melatonin can also be used to realign the circadian clock but, as well as timing and dosage issues, there are also concerns as to its legal status in different countries and with the World Anti-Doping Agency. Experimental data concerning the effects of food intake and exercise timing on jet lag is limited to date in humans, and more research is required before firm guidelines can be stated. All these stimuli can also be used in pre-flight adaptation strategies to promote adjustment in the required direction, and implementation of these is described. In addition, the effects of individual variability at the behavioural and genetic levels are also discussed, along with the current limitations in assessment of these factors, and we then put forward three case studies, as examples of practical applications of these strategies, focusing on adaptations to travel involving competition in the Rugby Sevens World Cup and the 2016 Summer Olympics in Rio de Janeiro, Brazil. Finally, we provide a list of practice points for optimal adaptation of athletes to jet lag. [ABSTRACT FROM AUTHOR]

Protective polymer coatings have been used to enhance the retention of enzymes in sol-gel films as immobilisation phases in electrochemical biosensors. Carbon film electrodes were electrochemically modified with poly(neutral red) (PNR). These electrodes were coated with oxysilane sol-gels incorporating glucose oxidase and an outer coating of carboxylated PVC (CPVC) or polyurethane (PU), with and without Aliquat-336 or isopropyl myristate (IPM) plasticizer, was applied. The biosensors were characterised electrochemically using cyclic voltammetry and amperometry, electrochemical impedance spectroscopy and scanning electron microscopy. Impedance spectra showed that the electrode surface is most active when the sol-gel–GOx layer is not covered with a membrane. However, membranes without plasticizer extend the lifetime of the biosensor to more than 2 months when PU is used as an outer membrane. The linear range of the biosensors was found to be 0.05–0.50 mM of glucose and the biosensor with PU outer membrane exhibited higher sensitivity (ca.117 nA mM−1) in the region of linear response than that with CPVC. The biosensors were applied to glucose measurement in natural samples of commercial orange juice. [ABSTRACT FROM AUTHOR]

Semi‐implantable needle oxygen electrodes were used for forearm subcutaneous monitoring in human subjects undertaking high intensity cycling and fist clenching exercise. pO2 variations in the range between 40 and100 mm Hg oxygen were seen. Superimposed on these were paradoxical rises in subcutaneous pO2, of up to 100 mm Hg which paralleled the scale of the exercise. This was indicative of increased blood flow through skin. Triton X‐100 incorporated into the sensor polyurethane membranes helped to give faster responses and reduced the possibility of biofouling and drift. The sterilizable system, free from internal electrolyte film appears promising for future clinical monitoring. [ABSTRACT FROM AUTHOR]

The presence of cancer cells in body fluids confirms the occurrence of metastasis and guides treatment. A simple, fast, and homogeneous fluorescent method was developed to detect cancer cells based on catalytic hairpin assembly (CHA) and bifunctional aptamers. The bifunctional aptamer had a recognition domain for binding to target cancer cells and an initiator domain for triggering the CHA reaction. In the presence of target cells, the bifunctional aptamer was released from the inhibitor and initiated a cascade reaction of assembly and disassembly of the hairpins. Separation of the fluorophores from the quenchers produced fluorescence signals. The proposed strategy showed high specificity for discriminating normal cells and leukocytes, and the detection limit was 10 cells/mL, which was lower than that of previous aptasensors. This assay was further tested using four kinds of clinical samples spiked with target cells to confirm its applicability. We developed a simple, rapid, and cost-effective method for the detection of cancer cells that did not require purification, and the approach holds great potential for bioanalysis and early diagnosis. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) show great potential for disease diagnostics due to their specific molecular profiles. Detection of miRNAs remains challenging and often requires sophisticated platforms. Here we report a multienzyme-functionalized magnetic microcarriers-assisted isothermal strand-displacement polymerase reaction (ISDPR) for quantitative detection of miRNAs. Magnetic micro-carriers (MMCs) were functionalized with molecular beacons to enable miRNAs recognition and magnetic separation. The target miRNAs triggered a phi29-mediated ISDPR, which can produce biotin-modified sequences on the MMCs. Streptavidin–alkaline phosphatase was then conjugated to the MMC surface through biotin–streptavidin interactions. In the presence of 2-phospho- L -ascorbic acid, miRNAs were quantitatively determined on a screen-printed carbon electrode from the anodic current of the enzymatic product. We show that this method enables detection of miRNAs as low as 9 fM and allows the discrimination of one base mismatched sequence. The proposed method was also successfully applied to analyze miRNAs in clinical tumor samples. This paper reports a new strategy for miRNAs analysis with high sensitivity, simplicity, and low cost. It would be particularly useful for rapid point-of-care testing of miRNAs in clinical laboratory. [ABSTRACT FROM AUTHOR]

The aim of this work is to review current knowledge relating the established cancer hallmark, sustained cell proliferation to the existence of chemicals present as low dose mixtures in the environment. Normal cell proliferation is under tight control, i.e. cells respond to a signal to proliferate, and although most cells continue to proliferate into adult life, the multiplication ceases once the stimulatory signal disappears or if the cells are exposed to growth inhibitory signals. Under such circumstances, normal cells remain quiescent until they are stimulated to resume further proliferation. In contrast, tumour cells are unable to halt proliferation, either when subjected to growth inhibitory signals or in the absence of growth stimulatory signals. Environmental chemicals with carcinogenic potential may cause sustained cell proliferation by interfering with some cell proliferation control mechanisms committing cells to an indefinite proliferative span. [ABSTRACT FROM AUTHOR]

The concept of enzyme-assisted substrate sensing based on use of fluorescent markers to detect the products of enzymatic reaction has been investigated by fabrication of micron-scale polyelectrolyte capsules containing enzymes and dyes in one entity. Microcapsules approximately 5 μm in size entrap glucose oxidase or lactate oxidase, with peroxidase, together with the corresponding markers Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride (Ru(dpp)) complex and dihydrorhodamine 123 (DHR123), which are sensitive to oxygen and hydrogen peroxide, respectively. These capsules are produced by co-precipitation of calcium carbonate particles with the enzyme followed by layer-by-layer assembly of polyelectrolytes over the surface of the particles and incorporation of the dye in the capsule interior or in the multilayer shell. After dissolution of the calcium carbonate the enzymes and dyes remain in the multilayer capsules. In this study we produced enzyme-containing microcapsules sensitive to glucose and lactate. Calibration curves based on fluorescence intensity of Ru(dpp) and DHR123 were linearly dependent on substrate concentration, enabling reliable sensing in the millimolar range. The main advantages of using these capsules with optical recording is the possibility of building single capsule-based sensors. The response from individual capsules was observed by confocal microscopy as increasing fluorescence intensity of the capsule on addition of lactate at millimolar concentrations. Because internalization of the micron-sized multi-component capsules was feasible, they could be further optimized for in-situ intracellular sensing and metabolite monitoring on the basis of fluorescence reporting. [ABSTRACT FROM AUTHOR]

Abstract: Analytical expressions for solute adsorption kinetics within porous carbon cylindrical granules of adsorbents with a one point formula for effective diffusion coefficient determination are available based on the assumption that solute transport is the rate limiting step and that it follows Fick''s Second Law. Here the first practical application of this theory is provided with an initial, estimated diffusion coefficient refined by fitting calculated kinetic adsorption curves to experimental data determined for activated carbons. In an ideal experiment, experimental error (noise) is negligible, and no data refinement is needed. However, real experimental data are always more or less noise contaminated. Where such noise is significant, a simulation method offers the best value for effective diffusion coefficient. For this specific system, surface modification, pH and temperature effects on adsorption kinetics were analysed quantitatively as a basis of determining effective diffusion coefficients through the porous structure. [Copyright &y& Elsevier]

Abstract: Silks are a diverse family of natural materials with extraordinary mechanical properties such as high tensile strength and extensibility, as well as reported biological compatibility. In recent years, the reported exceptional nature of silk lead to increased interest in silk for biomedical applications. The aim of this review is to assess the potential and compatibility of silk fibres and silk-based materials for biomedical purposes. It will do so by reviewing silk properties, structure and formation, with special focus on spider and mulberry silkworm silk fibres, as well as the application of silk in the biomedical field. The review will begin by introducing the general characteristics of silk, and a consideration of properties of particular relevance to the use of silk in biomedical applications: degradation and tensile properties. Subsequently, the formation of silk in vivo will be outlined, as well as the current understanding of silk structure. A comparison of the structural differences between spider and silkworm silks will follow. Some of the different types of silk produced by orb weaving spiders, their main functions and structural features will be described. This will be followed by an introduction to ‘supercontraction’, a phenomenon that has only been observed in spider silks, and is considered to be one of the major obstacles to the use of native spider silk for medical applications. Finally, there will be an account of previous biomedical applications of silk. It is the intention of this review to point out the wide range of excellent and valuable properties observed in different silk types, and to propose that silk’s versatility is possibly its strongest advantage. However, in the context of biomedical research and development, there are still major limitations and difficulties with native silk fibres. It is suggested in this review that an artificially produced silk or silk-like material formed to possess specific desired properties will allow the overcoming of present limitations. [Copyright &y& Elsevier]

Abstract: The nanoporous structure of collagen-glycosaminoglycan (CG) hydrogels was studied using 1H NMR spectroscopy and thermally stimulated depolarisation (TSD) current with layer-by-layer freezing-out of bulk and interfacial water. The depression of the freezing point of water is related to the size of the nanopore, to which it is confined. Changes in the Gibbs free energy of the unfrozen interfacial water are related to the amount of bound water in the hydrogel matrix and to the re-arrangement of the 3D network structure of the biopolymer. Analysis of the thermodynamic properties of bulk and interfacial water using the layer-by-layer freezing-out technique combined with NMR and TSDC provides valuable information about the structural features of CG hydrogels that can be used for characterisation of different types of hydrogels and soft tissue scaffolds, artificial skin substitutes and other biomaterials. [Copyright &y& Elsevier]

The oxidation mechanism and adsorption of inosine 5′-monophosphate and hypoxanthine were investigated in solutions of different pH using voltammetric and impedance methods at glassy carbon electrodes. For both compounds, the pH dependence from differential pulse voltammetry showed that the same number of electrons and protons are involved in the rate-determining step of the electrochemical reaction. In the case of hypoxanthine, it was also possible to study the effect of different concentrations. At high concentrations of hypoxanthine, two oxidation peaks were observed, the first due to hypoxanthine oxidation with formation of oligomers and the second due to hypoxanthine oligomer oxidation, both compounds adsorbing strongly. Impedance measurements corroborated the voltammetric results and enabled the study of the adsorption of hypoxanthine on glassy carbon. [Copyright &y& Elsevier]

Near Infrared (800–2500 nm) spectroscopy has been extensively used in biomedical applications, as it offers rapid, in vivo, bed-side monitoring of important haemodynamic parameters, which is especially important in critical care settings. However, the choice of NIR spectrometer needs to be investigated for biomedical applications, as both the dual beam dispersive spectrophotomer and the FTNIR spectrometer have their own advantages and disadvantages. In this study, predictive analysis of lactate concentrations in whole blood were undertaken using multivariate techniques on spectra obtained from the two spectrometer types simultaneously and results were compared. Results showed significant improvement in predicting analyte concentration when analysis was performed on full range spectral data. This is in comparison to analysis of limited spectral regions or lactate signature peaks, which yielded poorer prediction models. Furthermore, for the same region, FTNIR showed 10% better predictive capability than the dual beam dispersive NIR spectrometer. [ABSTRACT FROM AUTHOR]

Fluoxetine is a selective serotonin re-uptake inhibitor (SSRI) drug, widely used to treat depression, nervous anorexia, autism and bulimia nervosa. The direct electrochemical behaviour of fluoxetine at a glassy carbon electrode (GCE) was studied in simple aqueous solution using voltammetric techniques. Subsequently, a novel molecular imprinted polymer (MIP) modified GCE was fabricated using itaconic acid and N , N -methylene-bis acrylamide as functional monomer and crosslinking agent, respectively, to produce a sensitive, selective fluoxetine sensor. Precipitation polymerization enabled drop coating of reproducible MIP layers on a GCE as a renewable affinity surface for fluoxetine detection. Initial baseline studies undertaken using CV and SWV allowed for rapid optimization of scan conditions and confirming the irreversible nature of the FXT reaction at a bare GCE but DPV finally allowed for the further and necessary high level sensitivity needed for assays. The binding efficiency and selectivity of the MIP affinity sites for fluoxetine were demonstrated using DPV and responses compared with a non-imprinted polymer layer (NIP). Conditions for MIP formation, loading and incubation were optimized to improve the analytical performance. Under optimized conditions, a linear fluoxetine calibration from 4.99 × 10−7 to 3.38 × 10−5 mol L−1 was obtained, with detection and quantification limits of 3.33 × 10−7 mol L−1 (115.01 μg L−1) and 1.11 × 10−6 mol L−1 (383.38 μg L−1), respectively. The sensor was employed to analyse fluoxetine extracted from blood serum. Unlabelled Image • The electrochemical behaviour of Fluoxetine was studied at a GCE by CV, DPV and SWV. • A MIP was synthesized by rapid and convenient photopolymerization and characterized by FTIR, TGA, SEM and BET. • Assay conditions were optimized and Fluoxetine measurement made on solvent extracted blood serum. • The MIP formulation enabled generation of reproducible electrode coatings. [ABSTRACT FROM AUTHOR]

Uninterrupted monitoring of serum lactate levels is a prerequisite in the critical care of patients prone to sepsis, cardiogenic shock, cardiac arrest, or severe lung disease. Yet there exists no device to continuously measure blood lactate in clinical practice. Optical spectroscopy together with multivariate analysis is proposed as a viable noninvasive tool for estimation of lactate in blood. As an initial step towards this goal, we inspected the plausibility of predicting the concentration of sodium lactate (NaLac) from the UV/visible, near-infrared (NIR), and mid-infrared (MIR) spectra of 37 isotonic phosphate-buffered saline (PBS) samples containing NaLac ranging from 0 to 20 mmol/L. UV/visible (300–800 nm) and NIR (800–2600 nm) spectra of PBS samples were collected using the PerkinElmer Lambda 1050 dual-beam spectrophotometer, while MIR (4000–500 cm−1) spectra were collected using the Spectrum two FTIR spectrometer. Absorption bands in the spectra of all three regions were identified and functional groups were assigned. The concentration of lactate in samples was predicted using the Partial Least-Squares (PLS) regression analysis and leave-one-out cross-validation. The regression analysis showed a correlation coefficient (R2) of 0.926, 0.977, and 0.992 for UV/visible, NIR, and MIR spectra, respectively, between the predicted and reference samples. The RMSECV of UV/visible, NIR, and MIR spectra was 1.59, 0.89, and 0.49 mmol/L, respectively. The results indicate that optical spectroscopy together with multivariate models can achieve a superior technique in assessing lactate concentrations. [ABSTRACT FROM AUTHOR]

Quantification of lactate/lactic acid in critical care environments is essential as lactate serves as an important biochemical marker for the adequacy of the haemodynamic circulation in shock and of cell respiration at the onset of sepsis/septic shock. Hence, in this study, ATR-FTIR was explored as a potential tool for lactate measurement, as the current techniques depend on sample preparation and fails to provide rapid response. Moreover, the effects of pH on PBS samples (7.4, 7, 6.5 and 6) and change in solution conditions (PBS to whole blood) on spectral features were also investigated. A total 189 spectra from five sets of lactate containing media were obtained. Results suggests that lactate could be measured with more than 90% accuracy in the wavenumber range of 1500–600 cm − 1 . The findings of this study further suggest that there exist no effects of change in pH or media, when estimating lactate concentration changes in this range of the Mid-IR spectral region. [ABSTRACT FROM AUTHOR]

3D bioprinting is a major area of interest in health sciences for customized manufacturing, but lacks specific bioinks to enhance the shape fidelity of 3D bioprinting and efficiency of tissue repair for particular clinical purposes. A naringin derived bioink, which contains 1.5 mM methylacryloyl naringin and 0.15 mM methylacryloyl gelatin, improves the fidelity of 3D bioprinting due to 405 nm light absorption of methylacryloyl naringin. The naringin derived bioink promotes the growth of chondrocytes due to preserving bioactivities of naringin and functions as a medical ingredient from which it has been described as a medical bioink in this study. It facilitates cartilage regeneration by upregulating the transcription of chondrogenesis-related genes like SOX9 and genes against oxidative stress like SOD1 and SOD2 and maintains chondrocytes active resulting from the significantly enhanced COL II / COL I ratio. According to a rabbit cartilage defect model, the proposed naringin derived medical bioink significantly improves the efficiency and quality of cartilage defect repair, suggesting that the bioink is suitable for cartilage defect repair applications and a feasible strategy is provided for the formulation of medical bioinks for specific clinical purposes.

The disruptive action of an acute or critical illness is frequently manifest through rapid biochemical changes that may require continuous monitoring. Within these changes, resides trend information of predictive value, including responsiveness to therapy. In contrast to physical variables, biochemical parameters monitored on a continuous basis are a largely untapped resource because of the lack of clinically usable monitoring systems. This is despite the huge testing repertoire opening up in recent years in relation to discrete biochemical measurements. Electrochemical sensors offer one of the few routes to obtaining continuous readout and, moreover, as implantable devices information referable to specific tissue locations. This review focuses on new biological insights that have been secured through in vivo electrochemical sensors. In addition, the challenges of operating in a reactive, biological, sample matrix are highlighted. Specific attention is given to the choreographed host rejection response, as evidenced in blood and tissue, and how this limits both sensor life time and reliability of operation. Examples will be based around ion, O 2 , glucose, and lactate sensors, because of the fundamental importance of this group to acute health care.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety 'Mode of Action' framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology., (© The Author 2015. Published by Oxford University Press.)

Recent years have seen an increased interest in the use of natural and modified silks for tissue engineering. Despite longstanding concerns regarding the biocompatibility of silk sutures, only a few studies have been carried out to investigate the biocompatibility of natural silk fibers. Here, we report an in vitro assessment of the effect of nonmodified, degummed silks on cells. We describe the effects of degummed silk fibers as well as extracted sericin on cell metabolism and proliferation. Endothelial cells directly exposed to native degummed Bombyx mori and Antheraea pernyi silks showed lower rates of proliferation and metabolism than nonexposed cells. A similar but milder effect was observed for cells in direct contact with Nephila edulis egg sack fibers. Sericin and silk-conditioned medium had no negative effect on cell proliferation except in medium supplemented with 5% bovine serum prior to conditioning with A. pernyi silk. The toxicity of A. pernyi was negligible after thorough enzymatic treatment of the fibers with trypsin. It is, therefore, proposed that A. pernyi silk contain one or more cytotoxic components, which need to be removed prior to medical use., ((c) 2009 Wiley Periodicals, Inc.)

Polymeric membranes have been used as interfaces between implantable devices and biological tissues to operate as a protective barrier from water exchanging and to enhance biocompatibility. Polyurethanes have been used as biocompatible membranes for decades. In this study, copolymers of polyether urethane (PEU) with polydimethylsiloxane (PDMS) were synthesised with the goal of creating materials with low water permeability and high elasticity. PDMS was incorporated into polymer backbone as a part of the soft segment during polyurethane synthesis and physical properties as well as water permeability of resulting copolymer were studied in regard to PDMS content. Increase in PDMS content led to increase of microphase separation of the copolymer and corresponding increase in elastic modulus. Surface energy of the polymer was decreased by incorporating PDMS compared to unmodified PEU. PDMS in copolymer formed a hydrophobic surface which caused reduction in water permeability and water uptake of the membranes. Thus, PDMS containing polyurethane with its potent water resistant properties demonstrated a great promise for use as an implantable encapsulation material.

Degradation of a commercially available collagen-glycosaminoglycan dermal equivalent matrix was studied using electrochemical techniques. Degradation was accelerated by exposure to gamma radiation followed by storage at elevated temperatures or exposure to enzymes. The time-dependent diffusion of a small, electrochemically active, molecular probe, potassium ferrocyanide, through the matrix was monitored via changes in the oxidation peak currents of cyclic voltammograms. These measurements were made using a two-compartment diffusion chamber with the sample positioned well away from the working electrodes and a single-compartment electrode cell where the matrix was in direct contact with the working electrode. The relative merits of these two approaches are considered. Regardless of the approach chosen, amperometry appears well suited to monitoring progressive diffusivity changes through mechanically weak porous structures subject to different solution environments.

Various analytical expressions for solute adsorption kinetics within porous absorbents of defined geometry (planar sheet, cylinder, and sphere) are available in the literature. However, these expressions are limited for practical numerical evaluation because they are based on infinite series. An investigation of these expressions has been carried out and then accurate but simple expressions derived that enable rapid determination of effective diffusion coefficients for adsorption within geometrically categorical absorbents. These involve directly fitting calculated kinetic adsorption curves to experimental ones. A simple one point method is also proposed to estimate the effective diffusion coefficient for an adsorption process within these simple geometrical absorbents as an initial value for a best fit.

Background: Tight regulation of blood glucose levels from patients suffering from diabetes mellitus can significantly reduce the complications associated with this disease. For this reason, elaborate research efforts have been devoted to the development of a glucose sensor for the continuous in vivo monitoring of glucose. Although the use of microdialysis as a sampling interface between the body and the biosensor is widely accepted, a major drawback of conventional microdialysis is the limited in vivo recovery. Here, ultraslow microdialysis is proposed in order to obtain (near) quantitative in vivo recoveries. To avoid, however, unacceptable long delay times, the need for a small and low dead volume measuring device was recognised., Methods: A portable lightweight measuring device for continuous in vivo monitoring of glucose in subcutaneous tissue is presented. The measuring device consists of a miniaturised flow-through biosensor, connected to a microdialysis probe and a semi-vacuum pump. The biosensor is based on the amperometric detection of hydrogen peroxide after conversion of glucose by immobilised glucose oxidase. A portable potentiostat equipped with data logging is used for detection and registration., Results: The device was validated for its accuracy, precision, linearity, sensitivity, selectivity and stability during ex vivo and in vivo experiments. The linearity was found to be up to 30 mmol/l with a limit of detection of 0.05 mmol/l. The precision, depending on the biosensor tested was found to be 2-4%. No contribution to the signal could be observed from several tested electroactive species. The accuracy was found to be well in accordance with the criteria set for methods of Self Monitoring of Blood Glucose for patients with diabetes mellitus. The biosensors could be used for up to 3 days in the continuous mode. In vivo monitoring of glucose in dialysate of subcutaneous sampled tissue during glucose tolerance tests in healthy volunteers demonstrated the potential of this measuring device., Conclusions: A portable lightweight measuring device is presented which can measure continuously glucose in vivo without excessive calibration steps. The performance characteristics determined justify the application of this measuring device for the in vivo monitoring of glucose in subcutaneous sampled interstitium of diabetic patients.