Search

Background: Gemcitabine is a cornerstone drug for the treatment of all stages of pancreatic cancer and can prolong the survival of patients with pancreatic cancer, but resistance to gemcitabine in pancreatic cancer patients hinders its efficacy. The overexpression of Early growth response 1(EGR1) in pancreatic ductal adenocarcinoma as a mechanism of gemcitabine chemoresistance in pancreatic cancer has not been explored. The major mechanisms of gemcitabine chemoresistance are related to drug uptake, metabolism, and action. One of the common causes of tumor multidrug resistance (MDR) to chemotherapy in cancer cells is that transporter proteins increase intracellular drug efflux and decrease drug concentrations by inducing anti-apoptotic mechanisms. It has been reported that gemcitabine binds to MDR1 with high affinity. The purpose of this research was to investigate the potential mechanisms by which EGR1 associates with MDR1 to regulate gemcitabine resistance in pancreatic cancer cells. Methods: The following in vitro and in vivo techniques were used in this research to explore the potential mechanisms by which EGR1 binds to MDR1 to regulate gemcitabine resistance in pancreatic cancer cells. Cell culture; in vitro and in vivo study of EGR1 function by loss of function analysis. Binding of EGR1 to the MDR1 promoter was detected using the ChIP assay. qRT-PCR, Western blot assays to detect protein and mRNA expression; use of Annexin V apoptosis detection assay to test apoptosis; CCK8, Edu assay to test cell proliferation viability. The animal model of pancreatic cancer subcutaneous allograft was constructed and the tumours were stained with hematoxylin eosin and Ki-67 expression was detected using immunohistochemistry. Findings: We revealed that EGR1 expression was increased in different pancreatic cancer cell lines compared to normal pancreatic ductal epithelial cells. Moreover, gemcitabine treatment induced upregulation of EGR1 expression in a dose- and time-dependent manner. EGR1 is significantly enriched in the MDR1 promoter sequence.Upon knockdown of EGR1, cell proliferation was impaired in CFPAC-1 and PANC-1 cell lines, apoptosis was enhanced and MDR1 expression was decreased, thereby partially reversing gemcitabine chemoresistance. In animal experiments, knockdown of EGR1 enhanced the inhibitory effect of gemcitabine on tumor growth compared with the sh-NC group. Conclusions: Our study suggests that EGR1 may be involved in the regulation of MDR1 to enhance gemcitabine resistance in pancreatic cancer cells. EGR1 could be a novel therapeutic target to overcome gemcitabine resistance in pancreatic cancer. [ABSTRACT FROM AUTHOR]

A series of poly[methyl(trifluoropropyl)siloxane‐co‐silphenylenesiloxane] (PMTFPS‐co‐SPS) was synthesized by condensation polymerization of methyltrifluoro‐propylsiloxanediol and 1,4‐bis(dimethylsilyl)benzene. Their chemical structures were investigated using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and dynamic thermomechanical analysis (DMA). The effect of silphenylenesiloxane (SPS) units on the thermal stability of poly[methyl(trifluoropropyl)siloxane] (PMTFPS) was studied by thermogravimetric analysis (TGA), isothermal degradation tests, quantum chemical calculation, and pyrolysis‐gas chromatography–mass spectrometry (Py‐GCMS). The results showed that the thermal stability of PMTFPS improved with the introduction of SPS units into the backbone. The temperature for 5% mass loss in PMTFPS increased by 63°C under a nitrogen atmosphere. Additionally, the mechanism by which the SPS units improve the thermal stability of PMTFPS was also investigated. [ABSTRACT FROM AUTHOR]

It is still crucial to improve the mechanical characteristics of polyvinyl alcohol (PVA) films without resorting to chemical cross-linking. In this study, boric acid (BA) was used to enhance the mechanical characteristics of PVA films while maintaining their excellent transparency and biodegradability. The hydrogen bond interaction between PVA and BA resulted in a 70% increase in tensile strength (from 48.5 to 82.1 MPa) and a 46% increase in elongation at break (from 150 to 220%). To introduce antibacterial properties, polyhexamethylene guanidine hydrochloride (PHMG) was incorporated into PVA/BA composite films resulting in PVA/BA/PHMG composite films. The PVA/BA/PHMG films exhibited 99.99% bacterial inhibition against Escherichia coli and Staphylococcus aureus with negligible leaching of PHMG. The PVA/BA/PHMG films maintained a tensile strength of 75.3 MPa and an elongation at a break of 208%. These improved mechanical and antimicrobial properties make PVA/BA and PVA/BA/PHMG films promising for applications in food and medicinal packaging. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) aqueous suspensions are attracting considerable attention in conductive, antistatic, electromagnetic shielding coatings and films owning to their environmental safety. However, stable CNT suspensions are difficult to prepare because of the remarkable entanglement between CNTs and their intrinsic hydrophobicity. A new class of amphiphilic dispersants—pyrene butyric acid polyethylene glycol monoester (Py-mPEG)—were prepared through the esterification reaction between 1-pyrene butyric acid and polyethylene glycol monomethyl ether. Varieties of multi-walled carbon nanotubes (MWCNTs) aqueous suspensions were prepared by ultrasonic method using the following dispersants: Py-mPEG, sodium dodecyl benzene sulfonate (SDBS), Py-mPEG/Al2O3, and SDBS/Al2O3. The concentrations of suspended MWCNTs were determined by UV–vis absorption spectroscopy, and the state of suspensions was characterized by scanning electron microscopy (SEM). The non-covalent interactions between MWCNTs and Py-mPEG were investigated by fluorescence emission spectroscopy, and density functional theory calculations. The results showed that MWCNTs were more readily dispersed in Py-mPEG solutions than in SDBS solutions, whereas the Al2O3 particles could further improve the dispersion effect. Particularly, the MWCNT concentration reached 1.363 mg/mL using Py-mPEG (1000 ppm)/Al2O3 (particle size: 5–6 µm) as dispersant. A large number of individual MWCNTs were observed from the SEM images of the suspensions. A diffusion experiment on ink showed that the Al2O3 particles with particle size of 5–6 µm were highly responsive to ultrasound. The entangled MWCNTs could be disintegrated by the collision of particles. [ABSTRACT FROM AUTHOR]