The Effects of Curcumin on Aspergillus flavus, an opportunistic fungus that causes Invasive Aspergillosis

Undergraduate Basi

MicroCT analysis of connectivity in porous structures: optimising data acquisition and analytical methods in the context of tissue engineering

Micro-computed X-Ray Tomography (MicroCT) is one of the most powerful techniques available for the three dimensional characterisation of complex multi-phase or porous microarchitectures. The imaging and analysis of porous networks are of particular interest in tissue engineering due to the ability to predict various large-scale cellular phenomena through the micro-scale characterisation of the structure. However, optimising the parameters for MicroCT data capture and analyses requires a careful balance of feature resolution and computational constraints whilst ensuring that a structurally representative section is imaged and analysed. In this work, artificial datasets were used to evaluate the validity of current analytical methods by considering the effect of noise and pixel size arising from the data capture, and intrinsic structural anisotropy and heterogeneity. A novel ‘segmented percolation method’ was developed to exclude the effect of anomalous, non-representative features within the datasets, allowing for scale-invariant structural parameters to be obtained consistently and without manual intervention for the first time. Finally, an in-depth assessment of the imaging and analytical procedures are presented by considering percolation events such as micro-particle filtration and cell sieving within the context of tissue engineering. Along with the novel guidelines established for general pixel size selection for MicroCT, we also report our determination of 3 µm as the definitive pixel size for use in analysing connectivity for tissue engineering applications.MN was sponsored by Geitslich Pharma AG and the Gates Cambridge Trus

Perioperative latex hypersensitivity reactions: an integrative literature review

Este estudo teve por objetivo caracterizar as reações de hipersensibilidade ao látex em procedimentos anestésico-cirúrgicos. Foi realizada revisão integrativa da literatura nas bases LILACS, CINAHL, COCHRANE e MEDLINE, com seleção de artigos publicados em periódicos indexados de 1966 a setembro de 2011. Foram identificados 17 relatos de caso, dois estudos de prevalência e um de coorte. As reações ao látex foram majoritariamente do tipo III, e a principal fonte desencadeadora de reações no intraoperatório foram as luvas de látex; o tempo médio para manifestação da reação foi de 59,8 minutos após a indução anestésica; 44,4% dos pacientes relataram episódio de reação ao látex na avaliação pré-anestésica. Identificou-se que a história de episódios de reações a materiais de borracha, ou alimentos, na avaliação pré-anestésica não garante a segurança dos pacientes, se o profissional não estiver alerta à gravidade do problema; no caso de ocorrência de um evento anafilactoide, os profissionais tendem a suspeitar inicialmente dos medicamentos anestésicos.Este estudio tuvo como objetivo caracterizar las reacciones de hipersensibilidad al látex en la anestesia. Ha sido realizada una revisión integradora de la literatura en LILACS, CINAHL, COCHRANE y MEDLINE, con una selección de artículos publicados en periódicos indexados de 1966 hasta septiembre 2011. Fueron identificados 17 casos clínicos, 2 estudios de prevalencia y 1 de la cohorte. Las reacciones al látex fueron en su mayoría del tipo III y la principal fuente de reacción intra-operatoria fue el contacto con los guantes de látex. El tiempo medio hasta la aparición de respuesta fue de 59.8 minutos después de la inducción, 44,4% de los pacientes informaron una reacción al látex en el periodo pre-anestésico. La historia de reacciones alérgicas al látex en el periodo pre-anestésico no garantiza la seguridad de los pacientes si el profesional no está atento a la gravedad del problema. Al principio, se tiende a atribuir que el efecto de la anafilaxia se debe a los medicamentos anestésicos.This article characterizes hypersensitivity reactions during anesthetic-surgical procedures. This integrative literature review was conducted in the LILACS, CINAHL, COCHRANE and MEDLINE databases including papers published from 1966 to September 2011. A total of 17 case reports, two prevalence studies and one cohort study were identified. Latex reactions were mainly type III and the primary source of intraoperative reaction was latex gloves. The average time for clinical manifestation was 59.8 minutes after anesthetic induction; 44.4% of patients reported a reaction to latex at the pre-anesthetic evaluation. It was determined that the history of allergic reactions to latex obtained in the pre-anesthetic evaluation does not ensure the safety of patients if the staff is inattentive to the severity of the issue. There is also a tendency to initially attribute the anaphylactic event to the anesthetic drugs

Crosslinking Collagen Constructs: Achieving Cellular Selectivity Through Modifications of Physical and Chemical Properties

Collagen-based constructs have emerged in recent years as ideal candidates for tissue engineering implants. For many biomedical applications, collagen is crosslinked in order to improve the strength, stiffness and stability of the construct. However, the crosslinking process may also result in unintended changes to cell viability, adhesion or proliferation on the treated structures. This review provides a brief overview of some of both the most commonly used and novel crosslinkers used with collagen, and suggests a framework by which crosslinking methods can be compared and selected for a given tissue engineering application

Tunable bioactivity and mechanics of collagen-based tissue engineering constructs: A comparison of EDC-NHS, genipin and TG2 crosslinkers

Due to its ubiquity and versatility in the human body, collagen is an ideal base material for tissue-engineering constructs. Chemical crosslinking treatments allow precise control of the biochemical and mechanical properties through macromolecular modifications to the structure of collagen. In this work, three key facets regarding the collagen crosslinking process are explored. Firstly, a comparison is drawn between the carbodiimide-succinimide (EDC-NHS) system and two emerging crosslinkers utilising alternate chemistries: genipin and tissue transglutaminase (TG2). By characterising the chemical changes upon treatment, the effect of EDC-NHS, genipin and TG2 crosslinking mechanisms on the chemical structure of collagen, and thus the mechanical properties conferred to the substrate is explored. Secondly, the relative importance of mechanical and biochemical cues on cellular phenomena are investigated, including cell viability, integrin-specific attachment, spreading and proliferation. Here, we observe that for human dermal fibroblasts, long-term, stable proliferation is preconditioned by the availability of suitable binding sites, irrespective of the substrate modulus post-crosslinking. Finally, as seen in the graphical abstract we show that by choosing the appropriate crosslinker chemistries, a materials selection map can be drawn for collagen films, encompassing both a range of tensile modulus and fibroblast proliferation which can be modified independently. Thus, in addition to a range of parameters that can be modified in collagen constructs, we demonstrate a route to obtaining tunable bioactivity and mechanics in collagen constructs is uncovered, that is exclusively driven by the crosslinking process.EPSRC, Geistlich Pharma AG, Bill and Melinda Gates Foundatio

Feature importance in multi-dimensional tissue-engineering datasets: random forest assisted optimization of experimental variables for collagen scaffolds

Ice-templated collagen-based tissue-engineering scaffolds are ideal for controlled tissue regeneration since they mimic the micro-environment experienced in vivo. The structure and properties of scaffolds are fine-tuned during fabrication by controlling a number of experimental parameters. However, this parameter space is large and complex, rendering the interpretation of results and selection of optimal parameters to be challenging in practice. This paper investigates the impact of a cross section of this parameter space (drying conditions and solute environment) on the scaffold microstructure. Qualitative assessment revealed the previously unreported impact of drying temperature and pressure on pore wall roughness, and confirmed the influence of collagen concentration, solvent type, and solute addition on pore morphology. For quantitative comparison, we demonstrate the novel application of random forest regression to analyze multi-dimensional biomaterials datasets, and predict microstructural attributes for a scaffold. Using these regression models, we assessed the relative importance of the input experimental parameters on quantitative pore measurements. Collagen concentration and pH were found to be the largest factors in determining pore size and connectivity. Furthermore, circular dichroism peak intensities were also revealed to be a good predictor for structural variations, which is a parameter that has not previously been investigated for its effect on a scaffold microstructure. Thus, this paper demonstrates the potential for predictive models such as random forest regressors to discover novel relationships in biomaterials datasets. These relationships between parameters (such as circular dichroism spectra and pore connectivity) can therefore also be used to identify and design further avenues of investigation within biomaterials

MicroCT analysis of connectivity in porous structures: optimizing data acquisition and analytical methods in the context of tissue engineering.

Micro-computed X-ray tomography (MicroCT) is one of the most powerful techniques available for the three-dimensional characterization of complex multi-phase or porous microarchitectures. The imaging and analysis of porous networks are of particular interest in tissue engineering due to the ability to predict various large-scale cellular phenomena through the micro-scale characterization of the structure. However, optimizing the parameters for MicroCT data capture and analyses requires a careful balance of feature resolution and computational constraints while ensuring that a structurally representative section is imaged and analysed. In this work, artificial datasets were used to evaluate the validity of current analytical methods by considering the effect of noise and pixel size arising from the data capture, and intrinsic structural anisotropy and heterogeneity. A novel 'segmented percolation method' was developed to exclude the effect of anomalous, non-representative features within the datasets, allowing for scale-invariant structural parameters to be obtained consistently and without manual intervention for the first time. Finally, an in-depth assessment of the imaging and analytical procedures are presented by considering percolation events such as micro-particle filtration and cell sieving within the context of tissue engineering. Along with the novel guidelines established for general pixel size selection for MicroCT, we also report our determination of 3 μm as the definitive pixel size for use in analysing connectivity for tissue engineering applications

Self-assembly of collagen bundles and enhanced piezoelectricity induced by chemical crosslinking.

The piezoelectricity of collagen is purported to be linked to many biological processes including bone formation and wound healing. Although the piezoelectricity of tissue-derived collagen has been documented across the length scales, little work has been undertaken to characterise the local electromechanical properties of processed collagen, which is used as a base for tissue-engineering implants. In this work, three chemically distinct treatments used to form structurally and mechanically stable scaffolds-EDC-NHS, genipin and tissue transglutaminase-are investigated for their effect on collagen piezolectricity. Crosslinking with EDC-NHS is noted to produce a distinct self-assembly of the fibres into bundles roughly 300 nm in width regardless of the collagen origin. These fibre bundles also show a localised piezoelectric response, with enhanced vertical piezoelectricity of collagen. Such topographical features are not observed with the other two chemical treatments, although the shear piezoelectric response is significantly enhanced upon crosslinking. These observations are reconciled by a proposed effect of the crosslinking mechanisms on the molecular and nanostructure of collagen. These results highlight the ability to modify the electromechanical properties of collagen using chemical crosslinking methods.ERC, Bill and Melinda Gates Foundation, Geistlich Pharma A

In-situ ESEM imaging of the vapor-pressure-dependent sublimation-induced morphology of ice

Sublimation is a fundamental phase transition that has a profound impact on both natural phenomena and advanced manufacturing technologies. Although great strides have been made in the study of ice growth from melt and vapour, little consideration has been given to the effect of sublimation on the morphological features that develop in the ice microstructure. In this experimental study, we demonstrate the effect of vapour pressure on the mesoscopic faceting observed and show that a vapour pressure-specific wavelength characterises the periodic features that arise during sublimation. The ability to control the length scale of these features not only provides us with new insights on the mesoscopic roughness of ice crystals, but also presents the potential to exploit this effect in a plethora of applications from comet dating to ice-templated tissue engineering scaffoldsM Nair also funded by Geistlich Pharma AG and Gates Cambridge Trust