Planar photonic chips with tailored angular transmission for high-contrast-imaging devices

A limitation of standard brightfield microscopy is its low contrast images, especially for thin specimens of weak absorption, and biological species with refractive indices very close in value to that of their surroundings. We demonstrate, using a planar photonic chip with tailored angular transmission as the sample substrate, a standard brightfield microscopy can provide both darkfield and total internal reflection (TIR) microscopy images with one experimental configuration. The image contrast is enhanced without altering the specimens and the microscope configurations. This planar chip consists of several multilayer sections with designed photonic band gaps and a central region with dielectric nanoparticles, which does not require top-down nanofabrication and can be fabricated in a larger scale. The photonic chip eliminates the need for a bulky condenser or special objective to realize darkfield or TIR illumination. Thus, it can work as a miniaturized high-contrast-imaging device for the developments of versatile and compact microscopes.

Planar photonic chips with tailored angular transmission for high-contrast-imaging devices

A limitation of standard brightfield microscopy is its low contrast images, especially for thin specimens of weak absorption, and biological species with refractive indices very close in value to that of their surroundings. Here, we demonstrate, using a planar photonic chip with tailored angular transmission as the sample substrate, a standard brightfield microscopy can provide both darkfield and total internal reflection (TIR) microscopy images with one experimental configuration. The image contrast is enhanced without altering the specimens and the microscope configurations. This planar chip consists of several multilayer sections with designed photonic band gaps and a central region with dielectric nanoparticles, which does not require top-down nanofabrication and can be fabricated in a large scale. The photonic chip eliminates the need for a bulky condenser or special objective to realize darkfield or TIR illumination. Thus, it can work as a miniaturized high-contrast-imaging device for the developments of versatile and compact microscopes.

Basis of Image Analysis for Evaluating Cell Biomaterial Interaction Using Brightfield Microscopy

Medical imaging is a growing field that has stemmed from the need to conduct noninvasive diagnosis, monitoring, and analysis of biological systems. With the developments and advances in the medical field and the new techniques that are used in the intervention of diseases, very soon the prevalence of implanted biomedical devices will be even more significant. The implanted materials in a biological system are used in diverse fields, which require lengthy evaluation and validation processes. However, currently the evaluation of the toxicity of biomaterials has not been fully automated yet. Moreover, image analysis is an integral part of biomaterial research, but it is not within the core capacities of a significant portion of biomaterial scientists, which results in the use of predominantly ready-made tools. The detailed image analysis can be conducted once all the relevant parameters including the inherent characteristics of image acquisition techniques are considered. Herein, we cover the currently used image analysis-based techniques for assessment of biomaterial/cell interaction with a specific focus on unstained brightfield microscopy acquired mostly in but not limited to microfluidic systems, which serve as multiparametric sensing platforms for noninvasive experimental measurements. We present the major imaging acquisition techniques that enable point-of-care testing when incorporated with microfluidic cells, discuss the constraints enforced by the geometry of the system and the material that is analyzed, and the challenges that rise in the image analysis when unstained cell imaging is employed. Emerging techniques such as utilization of machine learning and cell-specific pattern recognition algorithms and potential future directions are discussed. Automation and optimization of biomaterial assessment can facilitate the discovery of novel biomaterials together with making the validation of biomedical innovations cheaper and faster.

Cholecalciferol Mediates Apoptosis in Siha Cervical Cancer Line via Autocrine Mechanisms

Cervical cancer disproportionately affects low-resource countries and is a significant health burden in South Africa. Pre-clinical studies have demonstrated numerous anti-cancer actions of vitamin D metabolites. Here, the anti-cancer action of the vitamin D precursor, cholecalciferol, was investigated in a high-grade cervical cancer cell line, SiHa. SiHa cell cultures were treated with a range of cholecalciferol doses (26 nM, 104 nM, 260 nM and 2600 nM) for 72 hours. Cell count and viability were assessed by crystal violet and trypan blue assays, respectively. Apoptotic cell death was investigated by flow cytometry, which measured mitochondrial membrane potential (∆Ψm), phosphatidylserine (PS) externalisation, effector caspase activation and the expression of DNA damage markers. Additionally, brightfield microscopy and transmission electron microscopy (TEM) were respectively used to characterise morphological and ultrastructural features of apoptosis. Expression of the vitamin D metabolising system (VDMS) – consisting of cholecalciferol activating (CYP2R1 and CYP27A1), calcidiol activating (CYP27B1) and calcidiol inactivating (CYP24A1) enzymes, and the vitamin D receptor (VDR) – was assessed by qPCR and Western blots. Data were analysed using a one-way ANOVA and Bonferroni post-hoc tests and p < 0.05 was considered statistically significant. Significant decreases in cell count (p = 0.011) and cell viability (p < 0.0001) were identified in SiHa cells treated with 2600 nM cholecalciferol. Furthermore, biochemical markers at 2600 nM treatment were significant for apoptosis, and included decreased ∆Ψm (p = 0.0145); increased PS externalisation (p = 0.0439); terminal caspase activation (p = 0.0025); and nuclear damage (p = 0.004). Moreover, biochemical apoptosis was corroborated by classical apoptotic features observed by brightfield microscopy and TEM. Additionally, a significant increase in CYP2R1 gene (p < 0.0001) and protein (p = 0.021) expression, and a converse significant decrease in CYP27B1 gene (p = 0.003) and protein expression (p = 0.031) were observed at 2600 nM cholecalciferol treatment. Furthermore, significant increases in VDR gene (p = 0.033) and protein (p = 0.04) expression, and CYP24A1 gene (p < 0.0001) and protein (p = 0.0274) expression were observed at 2600 nM cholecalciferol. In summary, high-dose cholecalciferol treatment of SiHa cervical cancer cells inhibits cell growth, induces apoptosis, and furthermore, upregulates CYP2R1 and VDR expression. Taken together, these findings suggest that autocrine activation of cholecalciferol to calcidiol may mediate VDR signalling of cell growth inhibition, and apoptosis in SiHa experimental cultures.