Anita Lorenz

Miniaturization of liquid chromatography (LC) systems offers numerous advantages. Nevertheless, miniaturized LC is still not widely used. Here, we present the additive manufacturing of hierarchically structured macro- and mesoporous functionalized polymer monoliths and their application for miniaturized reversed-phase chromatographic separations. A CAD-predesigned macroporous structure was generated by 3D printing of a repetitive design of Schoen gyroids from a photoresin via two-photon polymerization. For this, a photoresin formulation was developed containing a porogenic solvent to induce the formation of mesopores and a hydrophobic monomer to achieve a surface functionality suitable for reversed-phase chromatography. This strategy enables independent tuning of macropore geometry and mesoporosity, which is not readily achievable by conventional polymer monolith synthesis. Successful fabrication of hierarchically structured polymer monoliths was demonstrated by scanning electron microscopy and nano-computed tomography. The monolithic stationary phase was connected to a microfluidic system, and chromatographic separation of the nonpolar analytes naphthalene and fluoranthene was demonstrated. This highlights the applicability of the hierarchically structured porous functionalized polymer monolith as a reversed-phase stationary phase.

Polyelectrolyte multilayer (PEM) coatings represent a promising strategy for the biofunctionalization of biomaterials. Incorporating nonpolymeric components into the polymer matrix is a strategy to modulate PEM properties, enabling the development of new, application-specific functionalities. For example, integrating nano-thick wax layers both within and atop the PEM matrix creates hydrophobic waterproof barrier coatings that show great potential for use on bioresorbable magnesium implants. These coatings hinder contact between the implant and surrounding tissue and bodily fluids, thereby slowing down implants’ degradation. However, the hydrophobic nature of such coatings raises concerns regarding their cell compatibility and overall biocompatibility. This study investigates and compares the viability of fibroblasts (3T3 cells) and human umbilical vein endothelial cells (HUVECs) on three different hydrophilic PEM coatings and their corresponding composite hydrophobic PEM/Wax counterparts. Our results show that some aspects of cellular behavior are cell-type-specific, while others are commonly influenced by the chemical composition of the coatings. Although hydrophobic, all three PEM/Wax coatings supported fibroblast adhesion and growth, surpassing their hydrophilic PEM counterparts, whereas the more surface- and environment-sensitive HUVECs showed reduced adhesion and viability on the hydrophobic coatings compared with the hydrophilic PEMs. Cytotoxicity testing, conducted in accordance with ISO 10993-5, confirmed that all coatings are noncytotoxic, supporting their suitability for use in medical devices.

The early detection of head and neck cancer is a prolonged challenging task. It requires a precise and accurate identification of tissue alterations as well as a distinct discrimination of cancerous from healthy tissue areas. A novel approach for this purpose uses microspectroscopic techniques with special focus on hyperspectral imaging (HSI) methods. Our proof-of-principle study presents the implementation and application of darkfield elastic light scattering spectroscopy (DF ELSS) as a non-destructive, high-resolution, and fast imaging modality to distinguish lingual healthy from altered tissue regions in a mouse model. The main aspect of our study deals with the comparison of two varying HSI detection principles, which are a point-by-point and line scanning imaging, and whether one might be more appropriate in differentiating several tissue types. Statistical models are formed by deploying a principal component analysis (PCA) with the Bayesian discriminant analysis (DA) on the elastic light scattering (ELS) spectra. Overall accuracy, sensitivity, and precision values of 98% are achieved for both models whereas the overall specificity results in 99%. An additional classification of model-unknown ELS spectra is performed. The predictions are verified with histopathological evaluations of identical HE-stained tissue areas to prove the model’s capability of tissue distinction. In the context of our proof-of-principle study, we assess the Pushbroom PCA-DA model to be more suitable for tissue type differentiations and thus tissue classification. In addition to the HE-examination in head and neck cancer diagnosis, the usage of HSI-based statistical models might be conceivable in a daily clinical routine. Graphical abstract

A lens-based Raman spectrometer is characterized by studying the optical elements in the optical path and we study the measure of aberration–diffraction effects. This is achieved by measuring the spectral resolution (SR) thus encompassing almost all optical elements of a spectrometer that are mostly responsible for such effects. An equation for SR is used to determine the quality factor Q which measures aberration/diffraction effects occurring in a spectrometer. We show how the quality factor changes with different spectrometer parameters such as grating groove density, the wavelength of excitation, pinhole width, charge-coupled device (CCD) pixel density, etc. This work provides an insight into the quality of a spectrometer and helps to monitor the performance of the spectrometer over a certain period. Commercially available spectrometers or home-built spectrometers are prone to misalignment in optical elements and can benefit from this work that allows maintaining the overall quality of the setup. Performing such experiments over a period helps to minimize the aberration/diffraction effects occurring as a result of time and maintaining the quality of measurements.

Characterization of brain tumours requires neuropathological expertise and is generally performed by histological evaluation and molecular analysis. One emerging technique to assist pathologists in future tumour diagnostics is multimodal optical spectroscopy. In the current clinical routine, tissue preprocessing with formalin is widely established and suitable for spectroscopic investigations since degradation processes impede the measurement of native tissue. However, formalin fixation results in alterations of the tissue chemistry and morphology for example by protein cross-linking. As optical spectroscopy is sensitive to these variations, we evaluate the effects of formalin fixation on multimodal brain tumour data in this proof-of-concept study. Nonfixed and formalin-fixed cross sections of different common human brain tumours were subjected to analysis of chemical variations using ultraviolet and Fourier-transform infrared microspectroscopy. Morphological changes were assessed by elastic light scattering microspectroscopy in the visible wavelength range. Data were analysed with multivariate data analysis and compared with histopathology. Tissue type classifications deduced by optical spectroscopy are highly comparable and independent from the preparation and the fixation protocol. However, formalin fixation leads to slightly better classification models due to improved stability of the tissue. As a consequence, spectroscopic methods represent an appropriate additional contrast for chemical and morphological information in neuropathological diagnosis and should be investigated to a greater extent. Furthermore, they can be included in the clinical workflow even after formalin fixation.