Biology subjects

Dietzel, A.

Publications and source records attributed to Dietzel, A..

3 recordsLinked to original sources

bioRxiv2026

Joint effects of climate change and urbanization accelerate plant biodiversity loss across urban green spaces

Urbanization and climate change are rapidly reshaping biodiversity worldwide, yet their combined impacts on ecosystems remain poorly understood. Urban green spaces (UGS) underpin urban biodiversity, but differ widely in their structure, management, and exposure to global change. Here, we examine how these two drivers jointly influence plant communities across five major UGS types (allotments, private gardens, residential green spaces, parks, and ruderal areas) in three socio-culturally distinct Swiss cities. By combining vegetation surveys from 180 sites (60 sites per city) with species-specific thermal niches, high-resolution projections of historical and future urban microclimates, and land-use change scenarios, we trace how climate-driven species loss interacts with the shifting availability of urban habitats to shape biodiversity outcomes by mid-century. We found that UGS types differed markedly in their contributions to biodiversity, with allotments and ruderal areas supporting disproportionately high compositional uniqueness. However, climate change alone was projected to drive substantial plant diversity declines across all UGS types, with 40-80% of species exceeding their thermal niches by mid-century based on climate change scenario and UGS type. Although allotments exhibited relatively greater tolerance due to broader community-level thermal preferences, this advantage was undermined by their rapid decline under urbanization. When considered jointly, climate change and urbanization generated widespread biodiversity losses through complementary mechanisms: climate change drove species declines, while urbanization amplified these losses by disproportionately reducing high-value habitats. These results reveal a consistent trajectory of biodiversity decline across urban landscapes and highlight the need to conserve high-diversity yet shrinking UGS, particularly allotments, while enhancing the ecological value and climate resilience of expanding UGS, such as parks and residential areas, to safeguard future urban biodiversity under global change.

ecology↗

bioRxiv2025

Monodisperse LNPs - from Efficient Microfluidic Production and Loading to in Vitro Testing

Carrier nanoparticles facilitate the encapsulation of drug or mRNA molecules thereby enhancing their bioavailability. Microfluidic mixers provide a unique environment for the precise and continuous generation of nanoparticles by antisolvent precipitation. A major challenge is to understand the influence of microfluidic channel designs and geometries on the continuous production of small, uniform lipid nanoparticles (LNPs) and to identify conditions that ensure effective and controllable mixing of aqueous and organic phases in laminar flows. Another important challenge is that sufficient quantities for preclinical and clinical studies must be produced within a reasonable period of time. With this dual objective, different versions of a low aspect ratio laminar mixer (LARLM) were produced using two-photon polymerization (2PP). In the LARLM the organic phase forms a thin layer a few micrometers with a uniform velocity distribution in the center of the channel, surrounded by the aqueous phase. This concept has three major advantages: Firstly, it keeps all particles centralized in the channel, thus preventing contamination during prolonged particle generation. Secondly, diffusive mixing in the thin central stream occurs very quickly, and thirdly, the growing nanoparticles move at a homogeneous speed, which enables inline measurement of the particles. In systematic experiments with design versions of varied channel dimensions the operational parameters such as lipid concentrations and flow rates and the capability to produce LNPs with desired properties and loading capacities were explored. An interfacial dispersion model (IDM) could explain the surprising reduction of particle sizes with increased productivity. The latter allowed us to produce nanoparticles in the range of 50 nm to 180 nm (with 0.02 < PDI < 0.1) under stable conditions with a productivity of around one liter of LNP suspensions every three hours. Such performance has never been reached before with microfluidics. Moreover, LNPs loaded with coumarine-6 and various drugs were produced in the LARLM. Moreover, in-vitro experiments could confirm an improved bioavailability of coumarin-6 in cell culture experiments when loaded in LNPs by the LARLM. These results highlight the unique capabilities of LARLM devices and their potential to support nanoparticle formulation studies including preclinical and in further developments also clinical studies as required for approval as a marketable medicine.

bioengineering↗

bioRxiv2024

Spatiotemporal control of a multilayered co-axial flow in a 3D printed microchannel with cascaded nozzles

Sculpting and stopping multilayered co-flowing streams is challenging due to inhomogeneous pressure distribution within a fluidic circuit composed of multiple interconnected microchannels having variable flow resistances. Here, we have investigated three different flow control methods to effectively stop a multilayered flow inside a 3D-printed microfluidic channel by bringing the average flow velocity from >100 mm s-1 to below a critical velocity of 200 {micro}m s-1 within a certain delay time tD of [~]2s. Firstly, we 3D printed a sequence of three concentric nozzles ([~]75 {micro}m) embedded serially inside the microchannel ([~]200 {micro}m) using a two-photon polymerization (2PP) method. Secondly, we used the 2PP-based 3D printed device to produce a structured coaxial flow of four streams with individual layer thicknesses of O(10 {micro}m) within the outlet section of the microchannel. Thirdly, we removed the pressure gradient across the fluidic circuit, from > 2 bar to [~]0 bar, to stop the multilayered flow and measured tD to assess the performance of the three stop flow methods. During the stop-flow phase, an inhomogeneous pressure gradient across different inlets resulted in a backflow to inlet channels with lower pressures. In the three stop-flow methods investigated, we systemically managed the fluidic capacitance to minimize a dimensionless backflow index (BFI) value from [~]0.3 (worst case) to [~]0.03 (best case) for a total flow rate ranging from 16.8 {micro}l min-1 to 168 {micro}l min-1. Finally, we have recommended the best stop-flow conditions, which resulted in a minimal delay time of tD [~] 2s and a BFI < 0.05.

bioengineering↗