The impacts of spatio-temporal variation of natural and agricultural influences on the environmental water quality in a fluvial-lacustrine watershed in China.

Despite the significant impacts of natural factors such as rainfall, topography, soil type, and river network as well as agricultural activities on the environmental water quality, little is known about the influence of their temporal and spatial variations in a fluvial-lacustrine watershed. In this study, a whole process accounting method based the export coefficient model (WP-ECM) was first developed to quantify how natural factors and agricultural activities distribution influenced water quality. A case study was performed in a typical fluvial-lacustrine area - Dongting basin, China. The simulated results indicated that the natural factors can promote and inhibit the migration and transformation of agricultural pollutants generated from the watershed and the spatial distribution of the natural factors displayed high variability. It should be priority to monitor the areas with greater natural impact in the basin. Moreover, the cultivated land area and the number of pig-breeding were positively correlated with the pollutant discharge. From the perspective of the spatial distribution of comprehensive influence, the comprehensive high-impact areas are mainly distributed in the Dongting Lake district in 2005-2010 and in Xiang River watershed in 2010-2020. A key strategy for controlling or reducing the cultivated land area and the intensity of livestock breeding in these high-impacts areas is recommended to reduce the impact of the environmental water quality for the entire basin.

Nanoparticle Dynamics in Composite Hydrogels Exposed to Low-Frequency Focused Ultrasound.

Pulsed focused ultrasound (FUS) in combination with microbubbles has been shown to improve delivery and penetration of nanoparticles in tumors. To understand the mechanisms behind this treatment, it is important to evaluate the contribution of FUS without microbubbles on increased nanoparticle penetration and transport in the tumor extracellular matrix (ECM). A composite agarose hydrogel was made to model the porous structure, the acoustic attenuation and the hydraulic conductivity of the tumor ECM. Single-particle tracking was used as a novel method to monitor nanoparticle dynamics in the hydrogel during FUS exposure. FUS exposure at 1 MHz and 1 MPa was performed to detect any increase in nanoparticle diffusion or particle streaming at acoustic parameters relevant for FUS in combination with microbubbles. Results were compared to a model of acoustic streaming. The nanoparticles displayed anomalous diffusion in the hydrogel, and FUS with a duty cycle of 20% increased the nanoparticle diffusion coefficient by 23%. No increase in diffusion was found for lower duty cycles. FUS displaced the hydrogel itself at duty cycles above 10%; however, acoustic streaming was found to be negligible. In conclusion, pulsed FUS alone cannot explain the enhanced penetration of nanoparticles seen when using FUS and microbubbles for nanoparticle delivery, but it could be used as a tool to enhance diffusion of particles in the tumor ECM.

Collagen Crosslinking for Keratoconus: Cellular Signaling Mechanisms.

Collagen crosslinking (CXL) is a widely used treatment to halt the progression of keratoconus (KC). Unfortunately, a significant number of patients with progressive KC will not qualify for CXL, including those with corneas thinner than 400 µm. The present study aimed to investigate the molecular effects of CXL using in vitro models, mirroring the normal, as well as thinner corneal stroma seen in KCs. Primary human corneal stromal cells were isolated from healthy (HCFs) and keratoconus (HKCs) donors. Cells were cultured and stimulated with stable Vitamin C resulting in 3D self-assembled extracellular matrix (ECM), cell-embedded, constructs. CXL was performed on (a) thin ECM with CXL performed at week 2 and (b) normal ECM with CXL performed at week 4. Constructs without CXL served as controls. All constructs were processed for protein analysis. The results showed modulation of Wnt signaling, following CXL treatment, as measured by the protein levels of Wnt7b and Wnt10a, correlated to the expression of α-smooth muscle actin (SMA). Further, the expression of a recently identified KC biomarker candidate, prolactin-induced protein (PIP), was positively impacted by CXL in HKCs. CXL-driven upregulation of PGC-1 and the downregulation of SRC and Cyclin D1 in HKCs were also noted. Although the cellular/molecular impacts of CXL are largely understudied, our studies provide an approximation to the complex mechanisms of KC and CXL. Further studies are warranted to determine factors influencing CXL outcomes.

Engineering collagenous analogs of connective tissue extracellular matrix.

Connective tissue extracellular matrix (ECM) consists of an interwoven network of contiguous collagen fibers that regulate cell activity, direct biological function, and guide tissue homeostasis throughout life. Recently, ECM analogs have emerged as a unique ex vivo culture platform for studying healthy and diseased tissues and in the latter, enabling the screening for and development of therapeutic regimen. Since these tissue models can mitigate the concern that observations from animal models do not always translate clinically, the design and production of a collagenous ECM analogue with relevant chemistry and nano- to micro-scale architecture remains a frontier challenge in the field. Therefore, the objectives of this study are two-fold- first, to apply green electrospinning approaches to the fabrication of an ECM analog with nanoscale mimicry and second, to systematically optimize collagen crosslinking in order to produce a stable, collagen-like substrate with continuous fibrous architecture that supports human cell culture and phenotypic expression. Specifically, the "green" electrospinning solvent acetic acid was evaluated for biofabrication of gelatin-based meshes, followed by the optimization of glutaraldehyde (GTA) crosslinking under controlled ambient conditions. These efforts led to the production of a collagen-like mesh with nano- and micro-scale cues, fibrous continuity with little batch-to-batch variability, and proven stability in both dry and wet conditions. Moreover, the as-fabricated mesh architecture and native chemistry were preserved with augmented mechanical properties. These meshes supported the in vitro expansion of stem cells and the production of a mineralized matrix by human osteoblast-like cells. Collectively these findings demonstrate the potential of green fabrication in the production of a collagen-like ECM analog with physiological relevance. Future studies will explore the potential of this high-fidelity platform for elucidating cell-matrix interactions and their relevance in connective tissue healing.

Multilayer platform to model the bioactivity of hyaluronic acid in gastric cancer.

Hyaluronic acid (HA) has a key role in cancer progression. The HA's molecular weight (Mw) is altered in this pathological state: increased concentration of shorter fragments due to the overexpressed hyaluronidases and ROS. Aiming to mimic this microenvironment, we developed a Layer-by-Layer (LbL) platform presenting HA of different Mws, namely 6.4, 752 and 1500 kDa, to study the influence of HA Mw on the formation of focal adhesion sites (FAs), and the involvement of paxillin and CD44 in this process. High paxillin expression and formation of FAs, via CD44, is observed for MKN45 cells seeded on LbLs presenting HA 6.4 kDa, with the activation of the ERK1/2 pathway, responsible for cell motility and tumour progression. In contrast, activation of p38 pathway, usually related with cancer latency, is observed for cells seeded on LbLs with high Mw HA, i.e. 1500 kDa. Overall, we demonstrate the suitability of the developed platform to study cancer invasiveness.