Optical coherence tomography angiography measured area of retinal neovascularization is predictive of treatment response and progression of disease in patients with proliferative diabetic retinopathy.

BACKGROUND: The purpose of this study was to evaluate the area of retinal neovascularization in patients with treatment-naïve proliferative diabetic retinopathy (PDR) as measured by optical coherence tomography angiography (OCT-A) as a marker of subsequent treatment response after panretinal photocoagulation (PRP), and to examine if this area correlated with area of retinal neovascularization as measured by fluorescein angiography (FA). METHODS: En face OCT-A scans (4.5 × 4.5 mm) of neovascularizations were obtained at baseline (BL) before PRP and at month (M) 3 and M6 after treatment. Progression of PDR were defined as lesion growth (assessed by ophthalmoscopy and wide-field fundus photo) or increasing leakage by Optos ultra-widefield FA, and patients were divided into two groups; progression or non-progression. Mann-Whitney U test and Wilcoxon signed-rank test were used to analyse differences between groups and between time points. Areas of retinal neovascularizations (OCT-A and FA) were calculated by algorithms developed in Python (version 3.6.8, The Python Software Foundation, USA). RESULTS: Of 21 eyes included, 14 had progression of disease. Median OCT-A area did not differ between the two groups (progression vs. non-progression) at BL (76.40 ± 162.03 vs. 72.62 ± 94.15, p = 0.43) but were statistically significantly larger in the progression group at M6 (276.69 ± 168.78 vs. 61.30 ± 70.90, p = 0.025). Median FA area did not differ in the progression vs. the non-progression group at BL (111.42 ± 143.08 vs. 60.80 ± 54.83, p = 0.05) or at M6 (200.12 ± 91.81 vs. 123.86 ± 162.16, p = 0.62). Intraclass correlation between area by OCT-A and FA was -5.99 (95% CI: -35.28-0.993), p = 0.71. CONCLUSIONS: In this study of patients with treatment-naïve PDR, we showed that increasing area of retinal neovascularizations measured by OCT-A at M6 indicated progression of disease after PRP treatment. Our results suggest that area by OCT-A reflects disease activity and that it can be used as an indicator to monitor the progression of PDR over time, and to evaluate treatment response six months after PRP. Trial registration https://clinicaltrials.gov (identifier: NCT03113006). Registered April 13, 2017.

Effects of water-absorption and thermal drift on a polymeric photonic crystal slab sensor.

A photonic crystal slab (PCS) sensor is a universal refractive index sensor with possibilities and performance very similar to surface plasmon resonance (SPR), which represents the gold standard of biosensing. Cheap PCS sensors can be made vacuum-free entirely out of polymers, but come with additional challenges, besides those relating to temperature-variations, which must be considered in any refractive index based method: The polymeric waveguide core was found to swell by ∼0.3% as water absorbed into the waveguide core over ∼1.5 h. This was investigated by monitoring the wavelength of resonant reflection during absorption, by monitoring the release of water using ellipsometry, and by rigorous coupled-wave analysis (RCWA). The approach presented here enables monitoring of water uptake and thermal fluctuations, for drift-free, high-performance operation of a polymeric PCS sensor.

Automation of a single-DNA molecule stretching device.

We automate the manipulation of genomic-length DNA in a nanofluidic device based on real-time analysis of fluorescence images. In our protocol, individual molecules are picked from a microchannel and stretched with pN forces using pressure driven flows. The millimeter-long DNA fragments free flowing in micro- and nanofluidics emit low fluorescence and change shape, thus challenging the image analysis for machine vision. We demonstrate a set of image processing steps that increase the intrinsically low signal-to-noise ratio associated with single-molecule fluorescence microscopy. Furthermore, we demonstrate how to estimate the length of molecules by continuous real-time image stitching and how to increase the effective resolution of a pressure controller by pulse width modulation. The sequence of image-processing steps addresses the challenges of genomic-length DNA visualization; however, they should also be general to other applications of fluorescence-based microfluidics.

Refractometric monitoring of dissolution and fluid flow with distributed feedback dye laser sensor.

Monitoring the dissolution of solid material in liquids and monitoring of fluid flow is of significant interest for applications in chemistry, food production, medicine, and especially in the fields of microfluidics and lab on a chip. Here, real-time refractometric monitoring of dissolution and fast fluid flow with DFB dye laser sensors with an optical imaging spectroscopy setup is presented. The dye laser sensors provide both low detection limits and high spatial resolution. It is demonstrated how the materials NaCl, sucrose, and bovine serum albumin show characteristic dissolution patterns. The unique feature of the presented method is a high frame rate of up to 20 Hz, which is proven to enable the monitoring of fast flow of a sucrose solution jet into pure water.

Propofol modulates the lipid phase transition and localizes near the headgroup of membranes.

The compound 2,6-diisopropylphenol (Propofol, PRF) is widely used for inducing general anesthesia, but the mechanism of PRF action remains relatively poorly understood at the molecular level. This work examines the possibility that a potential mode of action of PRF is to modulate the lipid order in target membranes. The effect on monolayers and bilayers of dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) was probed using Langmuir monolayer isotherms, differential scanning calorimetry (DSC), isothermal titration calorimetry (ITC) and molecular dynamics (MD) simulations. Increasing amounts of PRF in a DPPC monolayer causes a decrease in isothermal compressibility modulus at the phase transition. A partition constant for PRF in DPPC liposomes on the order of K≈1500 M(-1) was found, and the partitioning was found to be enthalpy-driven above the melting temperature (Tm). A decrease in Tm with PRF content was found whereas the bilayer melting enthalpy ΔHm remains almost constant. The last finding indicates that PRF incorporates into the membrane at a depth near the phosphatidylcholine headgroup, in agreement with our MD-simulations. The simulations also reveal that PRF partitions into the membrane on a timescale of 0.5 µs and has a cholesterol-like ordering effect on DPPC in the fluid phase. The vertical location of the PRF binding site in a bacterial ligand-gated ion channel coincides with the location found in our MD-simulations. Our results suggest that multiple physicochemical mechanisms may determine anesthetic potency of PRF, including effects on proteins that are mediated through the bilayer.