Investigating the impact of the quantity of wet and dry cycles on the mechanical characteristics and fracture variations of sandstones.

The sandstone is in a state of dry-wet cycle under the repeated action of rainfall, and its mechanical properties are deteriorated to varying degrees, which causes cracks in the sandstone. Therefore, it is of great significance to study the mechanical properties and fracture propagation of sandstone under the action of dry-wet cycles. Currently, there are limited studies using numerical simulation methods to study the fracture extension of rocks under various dry and wet cycling conditions.Therefore, in this paper, the effects of different amounts of dry and wet cycling on the mechanical properties and fracture behavior of sandstone are investigated through uniaxial compression tests and numerical simulations of fracture extension. The findings indicate that the deformation stage of sandstone remains unchanged by the dry-wet cycle. The uniaxial compressive potency and coefficient of restitution gradually diminish as the quantity of cycles rises, while the Poisson's ratio exhibits the opposite trend, and the impact on the mechanical performance of sandstone wanes with cycle increments, and the correlation coefficient surpasses 0.93, signifying a substantial influence of the dry-wet cycle on sandstone's mechanical performances. The discrepancy between the numerical simulation and experimental results is minimal, with a maximum error of only 3.1%, demonstrating the congruence of the simulation and experimental outcomes.The mesoscopic examination of the simulations indicates that the quantity of fractures in the sandstone specimens rises with the escalation of dry-wet cycles, and the steps of analysis linked to crack inception and fracture propagation are accelerated, and the analysis steps from fracture initiation to penetration are also reduced.

Dual 7-ethyl-10-hydroxycamptothecin conjugated phospholipid prodrug assembled liposomes with in vitro anticancer effects.

7-Ethyl-10-hydroxycamptothecin (SN38), as a highly active topoisomerase I inhibitor, is 200-2000-fold more cytotoxic than irinotecan (CPT-11) commercially available as Camptosar®. However, poor solubility and low stability extensively restricted its clinical utility. In this report, dual SN38 phospholipid conjugate (Di-SN38-PC) prodrug based liposomes were developed in order to compact these drawbacks. Di-SN38-PC prodrug was first synthesized by inhomogeneous conjugation of two SN38-20-O-succinic acid molecules with L-α-glycerophosphorylcholine (GPC). The assembly of the prodrug was carried out without any excipient by using thin film method. Dynamic light scattering (DLS), transmission electron microscope (TEM) and cryogenic transmission electron microscopy (cyro-TEM) characterization indicated that Di-SN38-PC can form spherical liposomes with narrow particle size (<200nm) and negatively charged surface (-21.6±3.5mV). The loading efficiency of SN38 is 65.2 wt.% after a simple calculation. In vitro release test was further performed in detail. The results demonstrated that Di-SN38-PC liposomes were stable in neutral environment but degraded in a weakly acidic condition thereby released parent drug SN38 effectively. Cellular uptake studies reflected that the liposomes could be internalized into cells more significantly than SN38. In vitro antitumor activities were finally evaluated by MTT assay, colony formation assay, flow cytometry, RT-PCR analysis and Western Blot. The results showed that Di-SN38-PC liposomes had a comparable cytotoxicity with SN38 against MCF-7 and HBL-100, and a selective promotion of apoptosis of tumor cells. Furthermore, a pharmacokinetics test showed that Di-SN38-PC liposomes had a longer circulating time in blood compared with the parent drug. All the results indicate that Di-SN38-PC liposomes are an effective delivery system of SN38.

Novel dual VES phospholipid self-assembled liposomes with an extremely high drug loading efficiency.

Vitamin E succinate (VES), a unique selective anti-cancer drug, has attracted much attention for its ability to induce apoptosis in various cancer cells. Importantly, it has been reported that VES is largely non-toxic to normal cells. However, poor aqueous solubility and bioavailability extensively restricted its clinical utility. In this report, dual VES phospholipid conjugate (di-VES-GPC) prodrug based liposomes were prepared in order to develop an efficient delivery system for VES. Di-VES-GPC was first synthesized by conjugating VES with l-α-glycerophosphorylcholine (GPC) using N,N'-dicyclohexylcarbodiimide (DCC) as a coupling agent. The di-VES-GPC prodrug was able to self-assemble into liposomes by reverse-phase evaporation method. The structure of the liposomes was characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and cryo-TEM. The results showed that di-VES-GPC assembled liposomes were spherical with an average diameter approximately 183nm. Cryo-TEM data confirmed the formation of multilamellar liposomes with the bilayer thickness about 5nm by the assembly of the conjugate without any excipient. The VES drug loading highly reaches up to 82.8wt% in the liposomes after a simple calculation. Furthermore, the in vitro release behavior of di-VES-GPC liposomes was evaluated in different media. It was found that the liposomes could release free VES at a weakly acidic microenvironment but exhibited good stability under a simulated biological condition. The cellular uptake and intracellular drug release tests demonstrated that di-VES-GPC liposomes could be internalized effectively and converted into parent drug VES in cancer cells. Furthermore, in vitro antitumor activities of the di-VES-GPC liposomes were evaluated by MTT assay and flow cytometry. It was revealed that the liposomes presented comparable cytotoxicities to free VES. Taken together, the di-VES-GPC liposomes might provide an excellent formulation of VES which have potential in the treatment of cancers.

Self-assembled liposomes of dual paclitaxel-phospholipid prodrug for anticancer therapy.

In this report, a newly liposomal formulation of paclitaxel (PTX) based on dual paclitaxel succinate glycerophosphorylcholine (Di-PTX-GPC) prodrug was developed. The Di-PTX-GPC prodrug was synthesized by conjugating PTX with GPC through esterification under N,N'-carbonyldiimidazole (CDI) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) catalytic system. Di-PTX-GPC liposomes were prepared by thin film method and characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). The results indicated that the liposomes have an average diameter of 157.9nm with well-defined spherical morphology. In vitro drug release studies confirmed that the Di-PTX-GPC liposomes have controlled release profile of PTX at a weakly acidic environment, which formulates them suitable for sustained drug delivery. Additionally, in vitro cellular uptake analysis and cytotoxicity evaluation showed that Di-PTX-GPC liposomes were internalized successfully into tumor cells to induce the apoptosis against MCF-7, HeLa and HepG-2 cells. In vivo pharmacokinetics study revealed that such liposomal formulation of Di-PTX-GPC has longer retention half-life in bloodstream, which subsequently leads to slight accumulate in tumor sites due to enhanced permeability and retention (EPR) effect. More importantly, Di-PTX-GPC liposomes demonstrated good in vivo anticancer activities compared to Taxol with reduced adverse effects. Conclusively, these results suggest that Di-PTX-GPC liposomes could be an effective PTX delivery vehicles in clinical cancer chemotherapy.

Assembled liposomes of dual podophyllotoxin phospholipid: preparation, characterization and in vivo anticancer activity.

AIM: A novel amphiphilic prodrug dual podophyllotoxin (PPT) succinate glycerophosphorylcholine (Di-PPT-GPC) assembled liposomes was developed to improve efficiency of PPT. MATERIALS & METHODS: Di-PPT-GPC liposomes were prepared by thin film technique and characterized by dynamic light scattering and cryo-electron microscopy. RESULTS: In vitro release studies showed that Di-PPT-GPC liposomes could significantly release PPT in weakly acidic environment but had good stability under biological conditions. Methyl tetrazolium assay data revealed that the liposomes have comparable cytotoxicities to free PPT against MCF-7, HeLa and U87 cells. More importantly, in vivo antitumor evaluation indicated that Di-PPT-GPC liposomes exhibited favorable tumor growth inhibition without side effects. CONCLUSION: Di-PPT-GPC liposomes might have potential to promote the therapeutic effect of PPT for cancer therapy.

Nanoformulation of dual bexarotene-tailed phospholipid conjugate with high drug loading.

Bexarotene (Bex), a synthetic retinoid X receptor-selective activator, has been proved to be an efficacious chemotherapeutic agent. But, its clinical application is limited due to the poor solubility. In this report, dual bexarotene-tailed phospholipid (DBTP) conjugate based nanovesicles were prepared in order to develop new nanoformulation. DBTP conjugate was first synthesized by conjugating two Bex molecules with glycerophosphorylcholine (GPC) through facial esterification. The amphiphilic DBTP nanovesicles were prepared without any additive by reverse-phase evaporation method. They were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The results revealed that the DBTP nanovesicles have a spherical structure with an average diameter approximately 138.7nm and a negatively charged surface (-33.3±2.5mV). The loading efficiency of Bex is 76wt% after a simple calculation. In vitro degradation of DBTP nanovesicles and the release of Bex were further studied in detail. The results demonstrated that DBTP nanovesicles were stable in neutral environment but degraded in a weakly acidic condition and released parent drug Bex effectively. Cellular uptake was investigated by confocal laser scanning microscope (CLSM) and liquid chromatography-mass spectroscopy (LC-MS). The results demonstrated the successful internalization and intracellular release of DBTP nanovesicles. Furthermore, the cytotoxicity analysis and apoptosis of the nanovesicles showed higher antitumor activities compared with free Bex. In a conclusion, DBTP nanovesicles could be an effective nanoformulation of Bex.

Silicone hydrogels grafted with natural amino acids for ophthalmological application.

In this report, protein repelling silicone hydrogels with improved hydrophilicity were prepared by photo-polymerization of silicone-containing monomer and glycidyl methacrylate followed by grafting zwitterionic amino acids. The grafted silicone hydrogels possessed excellent hydrophilic surfaces due to the enrichment of amino acids, which was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle, and equilibrium water content measurements. Remarkable resistance to bovine serum albumin and lysozyme fouling was observed for the silicone hydrogels immobilized with neutrally charged amino acids because of the formation of zwitterionic surfaces with pairs of protonated secondary ammonium cations and deprotonated carboxyl anions. Meanwhile, the silicone hydrogels grafted with positively or negatively charged amino acids were able to repulse same charged protein with reduced deposition and attract oppositely charged protein with increased adsorption. Preliminary cytotoxicity test indicated that the zwitterionic silicone hydrogels were non-cytotoxic. Similarly, three types of natural amino acids, including serine, aspartic acid and histidine, modified silicone hydrogel contact lenses exhibited excellent hydrophilicity and non-damage to the rabbit's eyes, but only serine modified zwitterionic contact lens showed superior protein fouling resistance compared with the current commercial hydrogel contact lens, which may have great potential application in ophthalmology.

TiO2 nanoparticles: low-temperature hydrothermal synthesis in ionic liquids/water and the photocatalytic degradation for o-nitrophenol.

The well-crystallized anatase TiO2-IL nanoparticles were synthesized by one-step routes under low-temperature using room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate as an additional solvent with water. The photocatalytic properties of TiO2 nanoparticles were evaluated by photocatalytic degradation experiments of o-nitrophenol. The TiO2 nanoparticles show a higher photocatalytic activity than the TiO2 with pure water and commercial TiO2 (P25), which may be related to the high crystallinity. The TiO2-IL nanoparticles still hold a high photocatalytic activity after the catalyst was recycled nine times. Chemical oxygen demand removal was achieved under optimum experimental conditions.