33 research outputs found
Hydrogel-based standards for single and multiphoton imaging at depth
No full textMedical imaging is advancing rapidly through the development of novel laser sources and non-linear imaging methodologies. These developments are boosting deep tissue imaging allowing researchers to study diseases deep in the body enabling early diagnosis and better treatment. To help with the testing and optimization of these imaging systems and to aid in this process of deep tissue imaging, it's important to have robust, stable and reproducible standards and phantoms. Herein we present the design and fabrication of robust, multi-layered, hydrogel-based standards. The hydrogel used is a double network hydrogel consisting of two interpenetrating networks agarose and polyacrylamide. Thin layers of tough double network hydrogels are stacked to form multilayered depth standards having modality specific signaling markers embedded in between. Standard design and assembly ensured long term stability and easy transport. These proved useful in-depth imaging studies, utilizing multiple imaging modalities, including one photon fluorescence (1PEF), two photon fluorescence (2PEF), coherent anti-Stokes Raman imaging (CARS) and second harmonic generation imaging (SHG)
Picosecond ultrasonics for elasticity-based imaging and characterization of biological cells
No full text© 2020 Author(s). Characterization of the elasticity of biological cells is growing as a new way to gain insight into cell biology. Cell mechanics are related to most aspects of cellular behavior, and applications in research and medicine are broad. Current methods are often limited since they require physical contact or lack resolution. From the methods available for the characterization of elasticity, those relying on high frequency ultrasound (phonons) are the most promising because they offer label-free, high (even super-optical) resolution and compatibility with conventional optical microscopes. In this Perspective contribution, we review the state of the art of picosecond ultrasonics for cell imaging and characterization, particularly for Brillouin scattering-based methods, offering an opinion for the challenges faced by the technology. The challenges are separated into biocompatibility, acquisition speed, resolution, and data interpretation and are discussed in detail along with new results
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Identification of <i>Neisseria lactamica</i> Outer Membrane Proteins Protective against Meningococcal Disease
No full textA number of approaches have been taken towards the development of a vaccine protective against serogroup B meningococcal disease but, as yet, none have been successful. The commensal bacterium, Neisseria lactamica, shares many surface structures with N. meningitidis and N. lactamica may therefore provide an alternative approach to vaccinating against serogroup B disease. Immunological evidence suggests that carriage of N. lactamica is involved in natural protection against disease caused by N. meningitidis.
This study presents the important observation that N. lactamica vaccines protect mice against meningococcal challenge. To identify the components responsible for protection, the outer membrane proteins of N. lactamica, extracted from whole cells, were separated by preparative electrophoresis and pooled into low 67 kDa) molecular weight protein groups. The low molecular weight group provided the best protection of these groups, and further separation of this group indicated that proteins of 25-43 kDa provided the observed protection. Serum raised against N. lactamica proteins was cross-reactive with meningococci of different serogroups, serotypes and serosubtypes. N. lactamica antisera raised in mice were not bactericidal and although sera raised in rabbits showed some bactericidal activity, titres did not correlate with protection.
Meningococcal proteins cross-reactive with N. lactamica antisera were identified using surface enhance laser-desorption ionisation time-of-flight mass spectroscopy. The cross-reactive proteins had molecular masses of approximately 11.2 kDa, 13.7 kDa, 26.8 kDa, 17.4 kDa, 28.1 kDa, 33.1 kDa, 53.2 kDa and 66.6 kDa. Several meningococcal proteins of unknown function and others that have previously been considered as vaccine antigens (PorB and TbpB) were putatively identified. Proteins with epitopes homologous to these proteins are likely to be present in N. lactamica and may be involved in protection against meningococcal challenge. The identity of the 66.6 kDa protein as TbpB was confirmed by comparing the cross-reactivity of N. meningitidis OMPs from wild-type and TbpB knockout strains with N. lactamica antisera.
Using a N. lactamica genomic expression library, the DNA sequences of recombinant N. lactamica proteins cross-reactive with N. lactamica antiserum were obtained. Meningococcal proteins with homology to the N. lactamica sequences were identified by comparison with the complete genome sequences of N. meningitidis serogroups A and B. Fifteen cross-reactive sequences coded, either partially or completely, for 23 different proteins.
This study demonstrates that N. lactamica provides an effective vaccine in mice against lethal meningococcal challenge and that N. lactamica may provide an alternative approach to vaccination against serogroup B meningococcal disease. Putative identifications of the proteins involved in this protection have been made
Effect of skin color on optical properties and the implications for medical optical technologies: a review
No full textSignificance: Skin color affects light penetration leading to differences in its absorption and scattering properties. COVID-19 highlighted the importance of understanding of the interaction of light with different skin types, e.g., pulse oximetry (PO) unreliably determined oxygen saturation levels in people from Black and ethnic minority backgrounds. Furthermore, with increased use of other medical wearables using light to provide disease information and photodynamic therapies to treat skin cancers, a thorough understanding of the effect skin color has on light is important for reducing healthcare disparities.Aim: The aim of this work is to perform a thorough review on the effect of skin color on optical properties and the implication of variation on optical medical technologies.Approach: Published in vivo optical coefficients associated with different skin colors were collated and their effects on optical penetration depth and transport mean free path (TMFP) assessed.Results: Variation among reported values is significant. We show that absorption coefficients for dark skin are ∼6% to 74% greater than for light skin in the 400 to 1000 nm spectrum. Beyond 600 nm, the TMFP for light skin is greater than for dark skin. Maximum transmission for all skin types was beyond 940 nm in this spectrum. There are significant losses of light with increasing skin depth; in this spectrum, depending upon Fitzpatrick skin type (FST), on average 14% to 18% of light is lost by a depth of 0.1 mm compared with 90% to 97% of the remaining light being lost by a depth of 1.93 mm.Conclusions: Current published data suggest that at wavelengths beyond 940 nm light transmission is greatest for all FSTs. Data beyond 1000 nm are minimal and further study is required. It is possible that the amount of light transmitted through skin for all skin colors will converge with increasing wavelength enabling optical medical technologies to become independent of skin color
Studies of Genes Involved in Congenital Heart Disease
No full textCongenital heart disease (CHD) affects the intricate structure and function of the heart and is one of the leading causes of death in newborns. The genetic basis of CHD is beginning to emerge. Our laboratory has been engaged in identifying mutations in genes linked to CHD both in families and in sporadic cases. Over the last two decades, we have employed linkage analysis, targeted gene sequencing and genome wide association studies to identify genes involved in CHDs. Cardiac specific genes that encode transcription factors and sarcomeric proteins have been identified and linked to CHD. Functional analysis of the relevant mutant proteins has established the molecular mechanisms of CHDs in our studies
Living cells as a biological analog of optical tweezers – a non-invasive microrheology approach
No full textMicrorheology, the study of fluids on micron length-scales, promises to reveal insights into cellular biology, including mechanical biomarkers of disease and the interplay between biomechanics and cellular function. Here a minimally-invasive passive microrheology technique is applied to individual living cells by chemically binding a bead to the surface of a cell, and observing the mean squared displacement of the bead at timescales ranging from milliseconds to 100s of seconds. Measurements are repeated over the course of hours, and presented alongside analysis to quantify changes in the cells’ low-frequency elastic modulus, G′0, and the cell’s dynamics over the time window ∼10−2s to 10s. An analogy to optical trapping allows verification of the invariant viscosity of HeLa S3 cells under control conditions and after cytoskeletal disruption. Stiffening of the cell is observed during cytoskeletal rearrangement in the control case, and cell softening when the actin cytoskeleton is disrupted by Latrunculin B. These data correlate with conventional understanding that integrin binding and recruitment triggers cytoskeletal rearrangement. This is, to our knowledge, the first time that cell stiffening has been measured during focal adhesion maturation, and the longest time over which such stiffening has been quantified by any means
Relevance and utility of the in-vivo and ex-vivo optical properties of the skin reported in the literature: a review [Invited]
No full textImaging non-invasively into the human body is currently limited by cost (MRI and CT scan), image resolution (ultrasound), exposure to ionising radiation (CT scan and X-ray), and the requirement for exogenous contrast agents (CT scan and PET scan). Optical imaging has the potential to overcome all these issues but is currently limited by imaging depth due to the scattering and absorption properties of human tissue. Skin is the first barrier encountered by light when imaging non-invasively, and therefore a clear understanding of the way that light interacts with skin is required for progress on optical medical imaging to be made. Here we present a thorough review of the optical properties of human skin measured in-vivo and compare these to the previously collated ex-vivo measurements. Both in-vivo and ex-vivo published data show high inter- and intra-publication variability making definitive answers regarding optical properties at given wavelengths challenging. Overall, variability is highest for ex-vivo absorption measurements with differences of up to 77-fold compared with 9.6-fold for the in-vivo absorption case. The impact of this variation on optical penetration depth and transport mean free path is presented and potential causes of these inconsistencies are discussed. We propose a set of experimental controls and reporting requirements for future measurements. We conclude that a robust in-vivo dataset, measured across a broad spectrum of wavelengths, is required for the development of future technologies that significantly increase the depth of optical imaging
A U-Shape Fibre-Optic pH Sensor Based on Hydrogen Bonding of Ethyl Cellulose with a Sol-Gel Matrix
No full text© 1983-2012 IEEE. Development of a biocompatible pH sensor is of importance in biomedical applications, particularly for in vivo measurement, providing necessary information for clinical diagnosis and treatment such as chronic wounds and foetal acidosis. Traditional pH-indicator based optical sensors have problems of dye-leaching and photobleaching that restrict their uses in long-term monitoring. In this work, a dye-free fibre optic pH sensor is proposed consisting of a U-shape multimode optical fibre coated with a hybrid organic-inorganic composite film. The film is formed by cross-linking ethyl cellulose with a silica matrix at an optimised ethyl cellulose/silica molar ratio of 0.0065 via weakly interacted hydrogen bonding. This bonding is affected by hydrogen concentration (i.e., pH) in a solution resulting in a morphological change of the polymer aggregation presented in the silica matrix leading to refractive index change of the film. The developed sensor shows a reversible response to pH from 4.5 to 12.5 and exhibits linear correlation between transmitted light power and pH with a limit of agreement (LoA) between the sensor and a commercial probe of ±0.2 pH. For a clinically important range of pH values between 6 and 8 the LoA is ±0.1 pH. The sensor has low cross-sensitivity to temperature as the maximum interpreted pH change attributed to the power change is 0.12 pH when the temperature changes from 21 °C to 39 °C. To demonstrate biomedical relevance, the sensor is used to monitor pH of human serum. An in-house cytotoxicity assay is conducted with mouse fibroblast cell revealing that the film is not cytotoxic
Structure–Property Relationships of Near-Infrared Cyanine Dyes: Chalcogen-Driven Singlet Oxygen Generation with High Fluorescence Efficiency
No full textWe report the design, synthesis, and optical characterisations of eight novel near-infrared (NIR) cyanine dyes incorporating different chalcogens (O, S, and Se). These dyes exhibited excellent deep-NIR absorption (λmax = 767-833 nm) and emission (λmax = 784-859 nm) profiles. TDDFT calculations matched well the experimental trends and data. All compounds exhibited high extinction coefficients (178,000-267,000 cm-1 M-1) and good fluorescence quantum yields, resulting in high overall brightnesses. Remarkably, the selenium-containing dyes featuring terminal indole and benzoindole-type units exhibited impressive singlet oxygen quantum yields of around 13%, a standout performance in the deep-NIR region. These values are particularly promising and highlights the potential of these dyes for deep-NIR imaging and photodynamic applications
