Adéla Kotzianová

Raman Spectroscopy Based Method for the Evaluation of Compositional Consistency of Nanofibrous Layers

Electrospinning is currently a very popular method used across a number of industries. Electrospinning enables the production of nanofibrous layers of various structures and compositions. The production of a multi-component nanofibrous layer may result in an uneven distribution of the individual components throughout the layer. Confocal Raman spectroscopy combined with statistical methods allows these layers to be analysed by determining their chemical composition and thus provides feedback for the spinning process. This paper presents a method which combines Raman spectroscopy analysis and its subsequent evaluation with singular value decomposition (SVD). Automated measurement of Raman spectra makes it possible to gather extensive spectral data from a particular area selected on a sample; the spectra are measured from a specific volume and not from individual fibres. Samples require no preparation for the analysis and the non-destructive nature of Raman spectroscopy ensures their reusability. When spectra of the individual component materials are included for reference, the subsequent SVD analysis of the spectral data makes it possible to determine the chemical composition of the measured areas, thus providing the content percentages of the individual components, which can be displayed either in the form of a scattered plot or a Raman map.

Evaluating the degree of substitution of water-insoluble acyl derivatives of hyaluronan using Raman spectroscopy: method development and comparison with gas chromatography and 1H NMR

The properties of water-insoluble acyl derivatives of hyaluronan (HA) are strongly influenced by the degree of HA substitution (DS) and, therefore, the knowledge of exact DS values is greatly needed. The DS values of polysaccharides are usually evaluated by 1H NMR or chromatographic methods, which require sample dissolution. However, the studied HA derivatives are only soluble in mixed solvents, which is problematic especially for 1H NMR. To avoid solubilization issues, we developed a method for evaluating the DS of HA in the solid state using Raman spectroscopy. Calibration was performed using palmitoyl-HA oligosaccharides with the DS known from their molecular weight. The evaluation of Raman data is therefore not based on correlation with another technique. The results of Raman spectroscopy and gas chromatography agreed very well, with an average relative deviation of 5.5%. Conversely, 1H NMR significantly overestimated the DS due to the preferential dissolution of acyl groups. This problem was overcome by additional calibration. Our results show that Raman spectroscopy is a promising tool for evaluating the DS of HA acyl derivatives.

Non‐invasive diagnostic system and its opto‐mechanical probe for combining confocal Raman spectroscopy and optical coherence tomography

Non-invasive optical diagnostic methods allow important information about studied systems to be obtained in a non-destructive way. Complete diagnosis requires information about the chemical composition as well as the morphological structure of a sample. We report on the development of an opto-mechanical probe that combines Raman spectroscopy (RS) and optical coherence tomography (OCT), two methods that provide all the crucial information needed for a non-invasive diagnosis. The aim of this paper is to introduce the technical design, construction and optimization of a dual opto-mechanical probe combining two in-house developed devices for confocal RS and OCT. The unique benefit of the probe is a gradual acquisition of OCT and RS data, which allows to use the acquired OCT images to pinpoint locations of interest for RS measurements. The parameters and the correct functioning of the probe were verified by RS scanning of various samples (silicon wafer and ex vivo tissue) based on their OCT images - lateral as well as depth scanning was performed. Both the OCT and RS systems were developed, optimized and tested with the ultimate aim of verifying the functionality of the probe. Picture: Schematic illustration and visualization of the developed RS-OCT probe.

Increased thickness uniformity of large-area nanofibrous layers by electrodynamic spinning

This paper studies the causes of thickness inhomogeneities in continuously deposited large-area nanofibrous layers, introduces a new method of their rapid analysis and suggests technical measures to ensure greater thickness uniformity of produced nanofibrous layers. The thickness uniformity of nanofibrous layers over large surface areas and its testing have recently appeared as very important issues following the scale up of the production of nanofibrous layers from laboratory to industrial levels, i.e. from point-to-plate arrangement to roll-to-roll processing. The basic electrostatic spinning method produces layers with thickness distribution corresponding to the bivariate Gaussian distribution. However, increasing production and scaling-up processes often results in variations in the thickness of deposited nanofibrous layers even up to the order of tens of percent. But for most applications, inhomogeneities in the thickness are a critical and even limiting factor. Our results show that by using the met...