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Development of an Aptamer-Conjugated Polyrotaxane-Based Biodegradable Magnetic Resonance Contrast Agent for Tumor-Targeted Imaging
摘要： Gadolinium-based magnetic resonance imaging (MRI) contrast agents with biodegradability, biosafety, and high efficiency are highly desirable for tumor diagnosis. Herein, a biodegradable, AS1411-conjugated, α-cyclodextrin polyrotaxane-based MRI contrast agent (AS1411-G2(DTPA-Gd)-SS-PR) was developed for targeted imaging of cancer. The polyrotaxane-based contrast agent was achieved by the complexation of α-cyclodextrin (α-CD) and a linear poly(ethylene glycol) (PEG) chain containing disulfide linkages at two terminals. The disulfides enable the de-threading of the polyrotaxane into excretable small units due to cleavage of the disulfide linkages by reducing agents such as intracellular glutathione (GSH). Furthermore, the second-generation lysine dendron conjugated with gadolinium chelates and AS1411, a G-quadruplex oligonucleotide that has high binding affinity to nucleolin generally presenting a high level on the surface of tumor cells, coupled to the α-CD via click chemistry. The longitudinal relaxivity of AS1411-G2(DTPA-Gd)-SS-PR (11.7 mM?1 s?1) was two times higher than the clinically used Gd-DTPA (4.16 mM?1 s?1) at 0.5 T. The in vitro degradability was confirmed by incubating with 10 mM 1,4-Dithiothreitol (DTT). Additionally, the cytotoxicity, histological assessment and gadolinium retention studies showed that the prepared polyrotaxane-based contrast agent had a superior biocompatibility and was predominantly cleared renally without long-term accumulation toxicity. Importantly, AS1411-G2(DTPA-Gd)-SS-PR displayed the enhanced performance in MRI of breast cancer cells in vitro as well as a subcutaneous breast tumor in vivo due to the targeting ability of AS1411 aptamer. The enhanced performance was due to efficient multivalent interactions with tumor cells, producing faster accumulation and longer contrast imaging time at the tumor site. This work clearly confirms that the specially designed and fabricated α-CD-based polyrotaxane is a promising contrast agent with excellent contrast imaging performance and biosafety for tumor MR imaging.
关键词： AS1411 aptamer,biodegradability,polyrotaxanes,magnetic resonance imaging,breast cancer targeting
更新于2025-09-23 15:23:52
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Treatment of sanitary landfill leachate by the combination of photo-Fenton and biological processes
摘要： In this work, the pollutant reduction performance in landfill leachate by combining both photo-Fenton and biological processes was investigated. First, conventional biological treatment was performed, consisting of a decantation process, with centrifugation at 5000 rpm for 15 min, followed by the biological process conducted at 2.36 ± 0.1 mg mg?1 (BOD5/MLSS) and 0.571 ± 0.04 vvm (L L?1 min?1) for 40 h. At the same time, in the application of the photo-Fenton process, a central composite rotatable design (CCRD) was applied to evaluate the effect of main process variables. The quadratic models of chemical oxygen demand (COD) and 5 days biological oxygen demand (BOD5) removal were proposed and validated, being separately used as objective functions during the search for optimal operating conditions. After the application of the conventional biological process, removals of 87 ± 2% and 84 ± 2% were obtained for COD and BOD5, respectively. For the photo-Fenton process under optimum conditions (3400 mg H2O2 L?1, 80 mg Fe2? L?1, pH = 2.40 and 120 min), removals of 89 ± 3% COD and 75 ± 1% BOD5 were obtained. However, both processes did not meet effluent discharge standards. So, the optimized photo-Fenton process was then combined with the biological process, performed for 150 h with 1.571 ± 0.06 vvm and 4.41 ± 0.3 mg mg?1 (BOD5/MLSS). With the combined process, it was possible to treat an effluent with high organic load, achieving a removal of 98% COD and BOD5 and meeting the restrictive standards of release in recipient water bodies.
关键词： Toxic effluent,Processes combination,Biodegradability,Processes performance assessment
更新于2025-09-23 15:23:52
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Biodegradability of Disulfide-Organosilica Nanoparticles Evaluated by Soft X-ray Photoelectron Spectroscopy: Cancer Therapy Implications
摘要： Two kinds of organosilica nanoparticles (NPs) that were fabricated from thiol-containing precursors, (3-mercaptopropyl)trimethoxysilane and (3-mercaptopropyl)methyldimethoxysilane (MPDMS), are potential delivery vehicles of anticancer drugs. MPMS can form three siloxane bonds, but MPDMS forms two siloxane bonds as the maximum limit. Hence, disulfide bonds can be involved in the three-dimensional morphology of MPDMS NPs. In addition, NPs containing disulfide bonds are potentially degraded by a reduced form of glutathione (GSH). To examine reactions between the organosilica NPs and GSH, the NPs were incubated in 10 mM GSH aqueous solution at 37 °C for 7 d and the products were analyzed using field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and soft X-ray photoelectron spectroscopy (XPS). The Raman spectra showed the presence of disulfide bonds in the MPDMS NPs and the absence of disulfide bonds in MPMS NPs. The results of XPS measurements suggested that the disulfide bonds in the outer layer of MPDMS NPs were reduced to thiol groups. FE-SEM observations of MPDMS NPs detected changes in NP morphology after the GSH incubation. These results support the idea that MPDMS NPs contain disulfide bonds and are degradable by GSH. Therefore, MPDMS NPs possess a biodegradable feature that is advantageous for clinical translation, that is, nanomedicine.
关键词： (3-mercaptopropyl)methyldimethoxysilane,nanoparticles,(3-mercaptopropyl)trimethoxysilane,biodegradability,glutathione,X-ray photoelectron spectroscopy,Raman spectroscopy
更新于2025-09-23 15:22:29
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Degradation of tetracycline by solar photo-Fenton: Optimization and application in pilot photoreactor
摘要： The objective of this study is to analyze the photodegradation of the antibiotic tetracycline by the solar photo-Fenton process. The optimal conditions were obtained in a 22 (2 × 2) factorial design with the following input variables: reaction time and catalyst concentration (ferrous ion [Fe2+]). After statistical analysis using the Statistica 7.0 software, the optimal conditions determined, time = 120 min and Fe2+ = 166.81 mg/L, were applied in a pilot scale photoreactor, resulting in an 88.7% removal of the drug. In addition, in this stage we studied the reaction kinetics, biodegradability, and phytotoxicity of the products generated by the process. In the kinetic study, a constant of 1.82 × 10?2 min?1 was obtained. For this constant, a reaction time of 38.16 min is required for the initial tetracycline concentration to be reduced by 50%. The biodegradability tests indicated a gradual increase in the five-day biological oxygen demand/chemical oxygen demand ratio over time. The phytotoxicity tests showed an 18.5% decrease in the inhibition rate of the root growth of lettuce seedlings, indicating that the treatment applied reduces the toxicity of the substance.
关键词： photo-Fenton,photoreactor,solar photocatalysis,biodegradability,tetracycline,phytotoxicity
更新于2025-09-23 15:21:21
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Photo-Fenton oxidative of pharmaceutical wastewater containing meropenem and ceftriaxone antibiotics: influential factors, feasibility, and biodegradability studies
摘要： The main aim of the present research, as the first study, was coupling of hydrogen peroxide (H2O2), ferrous ions (Fe2t) and UV irradiation in a photo-Fenton system to degradation two anti-biotics (e.g. meropenem and ceftriaxone) from aqueous solution. The tests were carried out at different experimental conditions namely solution pH, iron dosages, H2O2 concentrations, UV light intensities, temperatures, and initial antibiotic concentrations. The degradation rates of 99 and 96.2% were observed for respectively meropenem and ceftriaxone during 60 min treatment. Biodegradability tests illustrated that photo-Fenton system has a high performance in removing organic compounds and biodegradability enhanced remarkably after treatment.
关键词： homogeneous Fenton,mineralization,antibiotic degradation,Photo-Fenton oxidation,biodegradability
更新于2025-09-23 15:19:57
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Chemodrug-Gated Biodegradable Hollow Mesoporous Organosilica Nanotheranostics for Multimodal Imaging-Guided Low-Temperature Photothermal Therapy/Chemotherapy of Cancer
摘要： Non-invasive physical treatment with relatively low intensity stimulation and the development of highly efficient anticancer medical strategy are still desirable for cancer therapy. Herein, a versatile biodegradable hollow mesoporous organosilica nanocapsule (HMONs) nananoplatform that is capped by the gemcitabine (Gem) molecule through a pH-sensitive acetal covalent bond is designed. The fabricated nanocapsule exhibits desirable small molecule release at the tumor tissues/cell sites, shows a reduced potential for drug accumulation risk. After loading indocyanine green (ICG), the heat-shock protein 90 (Hsp 90) inhibitor, 17AAG and modification with polyethylene glycol (NH2-PEG), the resulting ICG-17AAG@HMONs-Gem-PEG exhibited a precisely controlled release of ICG and 17AAG and low-temperature photothermal therapy (PTT) (~41 °C) with excellent tumor destruction efficacy. In addition, ICG loaded conferring the nanoplatform with near-infrared fluorescence imaging (FL) and photoaccoustic (PA) imaging capability. In short, this work not only presents a smart drug self-controlled nanoplatform with pH-responsive payloads released and theranostic performance, but also provides an outstanding low-temperature PTT strategy, which is highly valid in inhibition of cancer cells with minimal damage to the organism. Therefore, this research provides a paradigm that has a chemodrug-gated HMONs-based theranostic nanoplatform with intrinsic biodegradability, multimodal imaging capacity, high low-temperature PTT/chemotherapy efficacy and reduced systemic toxicity.
关键词： biodegradability,nanotheranostics,Hollow mesoporous organosilica,chemodrug gatekeeper,low-temperature photothermal therapy
更新于2025-09-11 14:15:04