Electrospun Methacrylated Gelatin/Poly(L-Lactic Acid) Nanofibrous Hydrogel Scaffolds for Potential Wound Dressing Application

Electrospun nanofiber mats have attracted intense attention as advanced wound dressing materials. The objective of this study was to fabricate methacrylated gelatin (MeGel)/poly(L-lactic acid) (PLLA) hybrid nanofiber mats with an extracellular matrix (ECM) mimicking nanofibrous structure and hydrogel-like properties for potential use as wound dressing materials. MeGel was first synthesized via the methacryloyl substitution of gelatin (Gel), a series of MeGel and PLLA blends with various mass ratios were electrospun into nanofiber mats, and a UV crosslinking process was subsequently utilized to stabilize the MeGel components in the nanofibers. All the as-crosslinked nanofiber mats exhibited smooth and bead-free fiber morphologies. The MeGel-containing and crosslinked nanofiber mats presented significantly improved hydrophilic properties (water contact angle = 0°; 100% wettability) compared to the pure PLLA nanofiber mats (~127°). The swelling ratio of crosslinked nanofiber mats notably increased with the increase of MeGel (143.6 ± 7.4% for PLLA mats vs. 875.0 ± 17.1% for crosslinked 1:1 MeGel/PLLA mats vs. 1135.2 ± 16.0% for crosslinked MeGel mats). The UV crosslinking process was demonstrated to significantly improve the structural stability and mechanical properties of MeGel/PLLA nanofiber mats. The Young’s modulus and ultimate strength of the crosslinked nanofiber mats were demonstrated to obviously decrease when more MeGel was introduced in both dry and wet conditions. The biological tests showed that all the crosslinked nanofiber mats presented great biocompatibility, but the crosslinked nanofiber mats with more MeGel were able to notably promote the attachment, growth, and proliferation of human dermal fibroblasts. Overall, this study demonstrates that our MeGel/PLLA blend nanofiber mats are attractive candidates for wound dressing material research and application

Culture-expanded allogenic adipose tissue-derived stem cells attenuate cartilage degeneration in an experimental rat osteoarthritis model

<div><p>Mesenchymal stem cell (MSC)-based cell therapy is a promising avenue for osteoarthritis (OA) treatment. In the present study, we evaluated the efficacy of intra-articular injections of culture-expanded allogenic adipose tissue-derived stem cells (ADSCs) for the treatment of anterior cruciate ligament transection (ACLT) induced rat OA model. The paracrine effects of major histocompatibility complex (MHC)-unmatched ADSCs on chondrocytes were investigated in vitro. Rats were divided into an OA group that underwent ACLT surgery and a sham-operated group that did not undergo ACLT surgery. Four weeks after surgery mild OA was induced in the OA group. Subsequently, the OA rats were randomly divided into ADSC and control groups. A single dose of 1 × 10⁶ ADSCs suspended in 60 μL phosphate-buffered saline (PBS) was intra-articularly injected into the rats of the ADSC group. The control group received only 60 μL PBS. OA progression was evaluated macroscopically and histologically at 8 and 12 weeks after surgery. ADSC treatment did not cause any adverse local or systemic reactions. The degeneration of articular cartilage was significantly weaker in the ADSC group compared to that in the control group at both 8 and 12 weeks. Chondrocytes were co-cultured with MHC-unmatched ADSCs in trans-wells to assess the paracrine effects of ADSCs on chondrocytes. Co-culture with ADSCs counteracted the IL-1β-induced mRNA upregulation of the extracellular matrix-degrading enzymes MMP-3 and MMP-13 and the pro-inflammatory cytokines TNF-α and IL-6 in chondrocytes. Importantly, ADSCs increased the expression of the anti-inflammatory cytokine IL-10 in chondrocytes. The results of this study indicated that the intra-articular injection of culture-expanded allogenic ADSCs attenuated cartilage degeneration in an experimental rat OA model without inducing any adverse reactions. MHC-unmatched ADSCs protected chondrocytes from inflammatory factor-induced damage. The paracrine effects of ADSCs on OA chondrocytes are at least part of the mechanism by which ADSCs exert their therapeutic activity.</p></div

CO₂ Exsolution from CO₂ Saturated Water: Core-Scale Experiments and Focus on Impacts of Pressure Variations

For CO₂ sequestration and utilization in the shallow reservoirs, reservoir pressure changes are due to the injection rate changing, a leakage event, and brine withdrawal for reservoir pressure balance. The amounts of exsolved CO₂ which are influenced by the pressure reduction and the subsequent secondary imbibition process have a significant effect on the stability and capacity of CO₂ sequestration and utilization. In this study, exsolution behavior of the CO₂ has been studied experimentally using a core flooding system in combination with NMR/MRI equipment. Three series of pressure variation profiles, including depletion followed by imbibitions without or with repressurization and repetitive depletion and repressurization/imbibition cycles, were designed to investigate the exsolution responses for these complex pressure variation profiles. We found that the exsolved CO₂ phase preferentially occupies the larger pores and exhibits a uniform spatial distribution. The mobility of CO₂ is low during the imbibition process, and the residual trapping ratio is extraordinarily high. During the cyclic pressure variation process, the first cycle has the largest contribution to the amount of exsolved CO₂. The low CO₂ mobility implies a certain degree of self-sealing during a possible reservoir depletion

Evaluation of Various Forms of Geothermal Energy Release in the Beijing Region, China

The energy inside the Earth can not only be released outward through earthquakes and volcanoes but also can be used by humans in the form of geothermal energy. Is there a correlation between different forms of energy release? In this contribution, we perform detailed seismic and geothermal research in the Beijing area. The results show that the geothermal resources in Beijing belong to typical medium-low temperature geothermal resources of the sedimentary basin, and some areas are controlled by deep fault activities (e.g., Xiji geothermal well (No. 17)). The heat sources are upper mantle heat, radioactive heat in granite, and residual heat from magma cooling. The high overlap of earthquakes and geothermal field locations and the positive correlation between the injection water and earthquakes indicate that the exploitation and injection water will promote the release of the earth’s energy. The energy releases are partitioned into multiple microearthquakes, avoiding damaging earthquakes (ML ≥ 5) due to excessive energy accumulation. Therefore, the exploitation of geothermal resources may be one way to reduce destructive earthquakes. Furthermore, the use of geothermal resources can also reduce the burning of fossil energy, which is of great significance in dealing with global warming

Degenerative changes in articular cartilage 4 weeks after surgery.

<p>Gross morphological observation of femoral condyles (A, B) and histological staining (Safranin-O/fast green) of cartilage (C, D).</p

Protective effects of ADSCs on IL-1β-stimulated chondrocytes.

<p>The relative mRNA expression levels of MMP-3, MMP-13, TNF-α, IL-6 and IL-10 in chondrocytes were determined by real-time PCR analysis. The data represent the means ± SD. P values < 0.05 for comparisons were considered significant. * P < 0.05 vs the control group, ^# P < 0.05 vs the IL-1βgroup.</p

Morphological and histological scores of articular cartilage after ADSC treatment.

<p>Morphological and histological scores of articular cartilage after ADSC treatment.</p

Histological evaluation of femoral condyles at week 8 and week 12 after surgery.

<p>H&E staining and Safranin-O/fast green staining of representative specimens. The control group at week 8 (A, E); the ADSC group at week 8 (B, F); the control group at week 12 (C, G); the ADSC group at week 12 (D, H). Severe (C, G), moderate (A, E, D, H) and mild (B, F) cartilage damage were observed.</p