Bandgap tailoring and enhancing the aromatization in cysteine-based carbon dots.

Cysteine, as a non-aromatic precursor, was used to produce Nitrogen (N) and Sulfur (S) sources for preparing N, S-doped carbon dots (CDs) with tunable luminescence emission. Despite the tremendous investigations, the photoluminescence (PL) mechanism of CDs is still unclear due to its complex core-shell structure, variety of surface functional groups, and structure dependency. This study focuses on controlling aromatization and graphitization processes during the hydrothermal synthesis on CDs by using Citric Acid (CA) and Ammonium persulfate. Detailed characterizations by FTIR spectroscopy, XPS, and HR-TEM are provided to suggest both chemical and bandgap structures. Results reveal that the red-shift of PL occurred due to the graphitization and increasing content of graphitic nitrogen in the core, as well as the Pyridinic and Amine groups creating sub-bands on the surface. These findings resolve the controversy on the PL mechanism of Cysteine-based CDs and provide a general guide for increasing the aromatization and graphitization degree from non-aromatic precursors which clarify the mechanism exploration and structural analysis of other types of CDs.

Controlled temperature-mediated curcumin release from magneto-thermal nanocarriers to kill bone tumors.

Systemic chemotherapy has lost its position to treat cancer over the past years mainly due to drug resistance, side effects, and limited survival ratio. Among a plethora of local drug delivery systems to solve this issue, the combinatorial strategy of chemo-hyperthermia has recently received attention. Herein we developed a magneto-thermal nanocarrier consisted of superparamagnetic iron oxide nanoparticles (SPIONs) coated by a blend formulation of a three-block copolymer Pluronic F127 and F68 on the oleic acid (OA) in which Curcumin as a natural and chemical anti-cancer agent was loaded. The subsequent nanocarrier SPION@OA-F127/F68-Cur was designed with a controlled gelation temperature of the shell, which could consequently control the release of curcumin. The release was systematically studied as a function of temperature and pH, via response surface methodology (RSM). The bone tumor killing efficacy of the released curcumin from the carrier in combination with the hyperthermia was studied on MG-63 osteosarcoma cells through Alamar blue assay, live-dead staining and apoptosis caspase 3/7 activation kit. It was found that the shrinkage of the F127/F68 layer stimulated by elevated temperature in an alternative magnetic field caused the curcumin release. Although the maximum release concentration and cell death took place at 45 °C, treatment at 41 °C was chosen as the optimum condition due to considerable cell apoptosis and lower side effects of mild hyperthermia. The cell metabolic activity results confirmed the synergistic effects of curcumin and hyperthermia in killing MG-63 osteosarcoma cells.

Optimized composition of nanocomposite scaffolds formed from silk fibroin and nano-TiO2 for bone tissue engineering.

Natural silk fibroin (SF) polymer has biomedical and mechanical properties as a biomaterial for bone tissue engineering scaffolds. Freeze-dried porous nanocomposite scaffolds were prepared from silk fibroin and titanium dioxide (TiO2) nanoparticles as a bioactive reinforcing agent by a phase separation method. In order to fabricate SF/TiO2 scaffolds, 5, 10, 15 and 20wt% of the TiO2 were added to the SF. The phase structure, functional groups and morphology of the scaffolds were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques, respectively. Porosity of the scaffolds was measured by Archimedes' Principle. In addition, mechanical properties of prepared scaffolds were evaluated by measuring the compressive strength and compressive modulus. The bioactivity property of these scaffolds was examined for 7, 14, 21 and 28days immersion in simulated body fluid (SBF) at 37°C and the in vitro degradation was studied by incubation in phosphate buffered saline (PBS) at 37°C and pH7.4 for up to 30days. Moreover, the scaffolds' biocompatibility was evaluated by seeding and culture of SaOS-2 osteoblast-like cells and assessment of their proliferation with MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Results showed that the prepared scaffolds had directional porosity and the reduction of porosity in composite scaffolds with higher contents of TiO2 nanoparticles resulted to an improvement of the mechanical strength. The macroporous structures with open interconnected and directional pores were successfully obtained without applying any porogen or inorganic solvent. The bioactivity of these scaffolds was confirmed by scanning electron microscopy (SEM) showing surface crystallization of the apatite layer proportional to the duration of immersion in the SBF and the degradation rate of scaffolds were increased by increasing the TiO2 content. The osteoblast-like cells showed a high attachment and proliferation on these scaffolds and their viability was increased with increasing the SF content. Finally, an optimum composition of SF/TiO2 nanocomposite scaffolds was selected.

The effect of three ergonomics training programs on the prevalence of low-back pain among workers of an Iranian automobile factory: a randomized clinical trial.

BACKGROUND: Many workers suffer from low-back pain. Type and severity of spinal complaints have relationship with work load. Lack of adherence to ergonomics recommendations among the important causes of low-back pain. OBJECTIVE: To assess the effect of 3 ergonomics training programs on the prevalence of lowback pain among workers of an Iranian automobile factory. METHODS: In a parallel-design 4-arm randomized clinical trial, 760 active workers of an automobile factory were studied. 503 workers were found eligible and randomized into 3 intervention groups (n=252), and a control group (n=251). The intervention groups consisted of 3 arms: 84 workers were educated by pamphlet, 84 by lectures, and 84 by workshop. Nordic questionnaire was used to determine the prevalence of spinal complaint before and 1-year after the interventions. The trial is registered with the Iranian Randomized Clinical Trial Registry, number IRCT2013061213182N2. RESULTS: Out of 503 workers, 52 lost to follow-up leaving 451 workers for analyses. The prevalence of low-back pain at the baseline was not significantly different among the studied arms. 1-year after the interventions, the prevalence did not change significantly from the baseline values for the lecture and pamphlet group. However, the prevalence of LBP experienced during the last year significantly (p=0.036) decreased from 42% to 23% in participant took part in the workshop. CONCLUSION: Training of automobile factory workers in ergonomics is more effective by running workshop than giving lecture or disseminating pamphlet.